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2517-02.09.1970
5e) ORDINANCE NG. 'S �� AN ORDINANCE REPEALING IN ITS ENTIRETY ORDINANCE 1/ NO. 2376 AND REPEALING SECTION 305, OF ORDINANCE NO. 2071, AND AMENDING ORDINANCE NO. 2071, ELEC- TRICAL CODE, WITH SECTION 305A AS SET FORTH, AND SUB-SECTION X-A, PRE-WIRED BUILDINGS, AS SET FORTH BE IT ORDAINED BY THE COUNCIL OF THE CITY OF WATERLOO, IOWA: That all of Section 305 of Ordinance No. 2071, as amended, which reads as follows, be, and the same is hereby repealed in its entirety: SECTION 305. Standards For Electrical Equipment And Its Installation All electrical equipment and its installation shall be reasonably safe to persons and property and in conformity with the provisions of this ordinance, the applicable statutes of the State of Iowa, and any orders, rules or regulations issued by the au- thority thereof, except where special circumstances reasonably require different methods of installation or equipment. Conformity of electrical equipment with applicable standards of Underwriters Labora- tories, Inc. , and conformity of electrical equipment installations with applicable regu- lations set forth in the National Electric Code, National Electric Safety Code or other safety codes approved by the American Standards Association shall be proof that all equipment or installations under this section are reasonably safe to persons and pro- perty when used for the purposes for which approved by such codes. The Electrical Inspector may authorize or approve special methods of installation or equipment. BE IT FURTHER ORDAINED BY THE COUNCIL OF THE CITY OF WATERLOO, IOWA: That amended Section 305A be, and the same is hereby enacted in lieu thereof: SECTION 305A - Standards For Electrical Equipment And Its Installation All electrical equipment and its installation shall be reasonably safe to persons and property and in conformity with the provisions of this Ordinance, the applicable statutes of the State of Iowa, and any orders, rules or regulations issued by the authority thereof, except where special circumstances reasonably require different methods of installation or equipment. Conformity of electrical equipment with applicable standards of Underwriters Labora- tories, Inc. , and conformity of electrical equipment installations with applicable regulations set forth in the National Electric Code, 1968 Edition, National Electric Safety Code or other safety codes approved by the American Standards Association shall be proof that all equipment or installations under this Section are reasonably safe to persons and property when used for the purposes for which approved by such codes. The Electrical Inspector may authorize or approve special methods of installation or equipment. BE IT FURTHER ORDAINED BY THE COUNCIL OF THE CITY OF WATERLOO, IOWA: That Sub-Section (x) , Section 601, of Ordinance No. 2071, as amended, which reads as follows, be, and the same is hereby repealed in its entirety: (x) Pre-Wired Buildings. All Pre-Wired Buildings shall have the conductors pulled into the outlet box at the factory. All conductors shall be continuous from panel to box and box to box without splice. All conductors shall be of grounding type or meet the requirements of type of occupancy for which building is designed. All circuits shall be terminated at the entrance panel and the local electrician in the City of Waterloo shall terminate all conductors on the over-current devices. The local elec- trician in the City of Waterloo shall make up joints in all outlet boxes; install the meter box and service conductors, install the service grounding wire, and then call for inspection before switches, fixtures, and outlets, and junction boxes are completed. Final inspection shall be called when building wiring is completed. Page 2 - BE IF FURTHER ORDAINED BY THE COUNCIL OF THE CITY OF WATERLOO, IOWA: That Sub-Section (x-a) , Section 601, of Ordinance No. 2071, as amended, be, and the same is hereby enacted in lieu thereof: (x-a) Pre-Wired Buildings. Pre-Wired Buildings shall be wired with a minimum of ground- ing type non-metalic cable, or shall be wired with material for Type of Occupancy and Zoning. All buildings shall be inspected at the time of construction at the Manufactur- ing Plant by a qualified inspector who is an active member in good standing of the International Association of Electrical Inspectors, using the Waterloo Electrical Ordinance as a guide for his inspection. Before shipping to the job site, the Inspector shall attach to the building a Certificate of Inspection, and also forward a duplicate of said Certificate to the Inspector in the City of Waterloo, Iowa. Any work that is required at the job site shall be executed by a Bonded, Licensed Electrician to do work in the City of Waterloo, Iowa. An electrical permit shall be required by the local electrician and fees shall be paid in accordance with Article IV, Section 407, of the Waterloo Ordinance No. 2071. olie at. ._ Passed and adopted this day of ;1"-yt4fE6.1,f, 19 76) Wit- ---, MAYOR ATTEST: CITY CLERK Str--142 STATE OF IOWA, I, .._?QbP __J.__Tdlge-C oar SS Publisher of the Black Hawk County, lUatexloa t••• "We Courier a daily newspaper printed in the English language and published in Waterloo, Black Hawk County, Iowa do solemnly swear that the annexed copy of Ordinance No. 2517 . ORDINANCE NO.I JN i AN ORDINANCE REPEALING IN ITS notice was published in the English language only it}y i ENTIRETY ORDINANCE NO. 2376 AND REPEALING SECTION 305, OF ORDI- NANCE NO. 2071, AND AMENDING OR- DINANCE NO.2071,ELCTRICAL CODE, 19 WITH 'SECTION 305A AS SET FORTH, AND SUB-SECTION X-A, PRE-WIRED commencing on the day of BUILDINGS,AS SET FORTH. FebrUar 1.2 1970 I BE IT ORDAI ED THE COUNCIL OF THE CITY LOO, IOWA: , in the issues of .y That all of Section 306 of ORDINANCE No. 2071, as amended, which reads as of said newspaper, and follows, be, and the same is hereby re- S In its .entirety:tan that the annexed rate of advertising is the regular legal rate of SECTION ment And ndIts dInstallation Electrical All electrical equipment and Its installa- tion shall be reasonably safe to persons said newspaper, and that the following is a correct bill for pub- and property and In conformity with the fishing said notice. provisions of this ordinance, theoppfica- ble statutes of the State of Iowa, and p any orders, rules or regulations issued by Printer's Bill $ 28•40 the authority thereof, except where spe- cial circumstances reasonably require dif- ferent methods of Installation or equip- ment. ' Conformity of electrical equipment with applicable standards of Underwriters Lab- oratories, Inc.,. and conformity of elec- trical equipment installations with ap- Subscribed and sworn to before me this 12th day pilcabie regulations set forth In the Na- tional Electric Code, National Electric. February r,o Safety Code or other safety codes op- of J A. D., 19 7 proved by the American Standards As- sociation shall be proof that all equip- ment or installations under this section a.,_00. _ _ _____ are reasonably safe to persons and prop- erty when used for the purposes for which approved by such codes. The Electrical Inspector may authorize or approve special methods of instolla- Received of _. lion or equipment. EE IT FURTHER ORDAINED BY THE COUNCIL OF THE CITY OF WATER- the sum of Dollars LOG, IOWA: That amended Section 305A be,and the same is hereby enacted in lieu thereof: in full for publication of the above notice. SECTION rdtl Electrical And IsInsallai All electrical equipment and its in- 1stallation shall be reasonably safe to Publishers persons and property and in conformity with the provisions of this Ordinance, the applicable statutes of the State of tn Iowa, and any orders, rules or regula- I�I ulli 'Issued by the authority thereof, except where Sptekil t reu'mdans lig. onably require different methods of in- I steliatIon or equipment. t . a,fcrmity a eelactrvcol Ia wtirItprc Lob-: ' . ._ _ .,...., .., n..duru,ritore Lah-I NATIONAL ELECTRICAL CODE 1968 A USA STANDARD /#417)‘ /.7 , _a . r ., .0,9- . i/2, 7.., _ 417O . . ..__ . .. . _ . . ..,,,_•„....._,........_ .......„.. . .... . . , , ,.. .,, • , . . , ,. . . ., . . . .. ..,...„ _, . „. . . , ,,,.., , _ ... .,,,,,,,• : ,, i... 4. ' : ' i ,„, . isti . ., , ......„....„,„...„........„_ „ „ , i • 'F,;.. „. x . A ,,,, . _4- ',., ' .4 f.. .,+ 1. ;. t, •i. kt , :, '.t , . — Pvi t i..„, t g - . iiV .'''''-- ' \-,:.,tt: is,„ , 1 1 i i„ s e A�". NFPA No. 70-1968 "-` `g" USAS C1-1968 ABOUT THE SPONSOR This National Electrical Code is sponsored by the National Fire Pro- tection Association under the auspices of the United States of America Standards Institute. The purpose of the National Electrical Code is de- tailed in Section 90-1 and the scope of the Code is outlined in Section 90-2. The National Fire Protection Association was organized in 1896 to promote the science and improve the methods of fire protection. Mem- bership in the Association is open to anyone interested.The annual dues for Associate Members are $20.00 a year. International, national, and regional organizations, institutes, and societies interested in the protec- tion of life and property against loss by fire may be Organization Mem- bers of the Association for which the dues are $150.00 a year. Full de- tails on membership privileges and benefits are available from the As- sociation's Headquarters. The National Fire Protection Association has acted as sponsor of the National Electrical Code since 1911. The original Code document was developed in 1897 as a result of the united efforts of various insurance, electrical, architectural, and allied interests. Membership in the present National Electrical Code Committee is shown on Pages 70-v through 70-xi.The Rules of Procedure under which the National Electrical Code Committee operates are published in the Appendix, and the Time Schedule for the next (1971) Edition of the National Electrical Code is also given in the Appendix. The National Fire Protection Association has an Electrical Section which provides particular opportunity for NFPA members interested in electrical safety to become better informed and to contribute to the development of the National Electrical Code and other NFPA elec- rical standards.The Electrical Section sponsors,for the above purposes, open meetings that are normally held during the NFPA Annual Meet- ings. During these Section Meetings, proposals for revisions or addi- tions to NFPA electrical standards are reviewed and discussed. Bulletins and reports on matters affecting the National Electrical Code Committee and other NFPA activities in the electrical field are issued to members of the section periodically. Membership in the Electrical Section is open to any Associate Member of the NFPA and up to four individuals desig- nated by any NFPA Organization Member at no additional cost. The Section is composed of technically interested individuals (not com- panies, government departments or organizations) and each member- ship must be in the name of the individual. A folder on the purposes, privileges and personnel of the NFPA Electrical Section is available from the Association. Prices for Additional Copies The following schedule of prices applies for single and multiple copies of this edition of the 1968 National Electrical Code. 1 to 5 copies $2.00 each Over 5 copies $1.90 ea. 100 copies and over . . $1.55 ea. 25 copies and over 1.80 ea. 250 copies and over .. 1.35 ea. 50 copies and over 1.70 ea. 500 copies and over . . 1.20 ea. 1,000 copies and over: Ask for special quotation. Prices quoted are F.O.B.Boston,Mass. Taxes not included. Copyright©1968 NATIONAL FIRE PROTECTION ASSOCIATION 60 Batterymarch St.,Boston,Mass.02110 70-i National Electrical Code 1968 Edition A USA Standard NFPA No.70-1968;USAS C1-1968(Rev.of C1-1965) 1968 Edition of National Electrical Code This 1968 Edition of the National Electrical Code (NFPA No. 70- 1968; USAS C1-1968)was adopted by the National Fire Protection As- sociation at its Annual Meeting held May 20-24, 1968 in Atlanta, Georgia and approved by the United States of America Standards Insti- tute on July 11, 1968.It supersedes all previous editions of the National Electrical Code,the most recent previous edition being 1965. Changes in this 1968 Edition of the National Electrical Code (as compared with the 1965 Edition) are indicated by vertical marginal rules on the affected pages. In certain cases, minor editorial changes are not so indicated. Special attention is called to the inclusion in this 1968 Edition of Tentative Interim Amendments Nos. 146 and 148 appearing in the Ap- pendix. Attention is also called to the Appendix for the "Time Schedule for the 1971 National Electrical Code"which is the next regular edition. The "Method of Submitting Proposal to Revise the National Electrical Code" is included in the Appendix to guide anyone concerned with the proper procedures for handling proposed revisions. This Code is purely advisory as far as the NFPA and the USASI are concerned but is offered for use in law and for regulatory purposes in the interest of life and property protection (see copyright statement on Page 70-ii).Anyone noticing any errors should please notify the NFPA Executive Office,the Chairman and the Secretary of the Committee. This edition is also published by the NFPA in the 1968-69 edition of Volume 5 of the National Fire Codes and will appear in subsequent yearly editions of this Volume until superseded by a later edition. Origin and Development of National Electrical Code Consistent with the Rules of Procedure for the National Electrical Code Committee (see Appendix) a "PREPRINT" OF THE PROPOSED AMENDMENTS FOR THE 1968 NATIONAL ELECTRICAL CODE was pub- lished by the National Fire Protection Association in July 1967. This "PREPRINT" recorded the actions of the various Code-Making Panels and the Correlating Committee of the National Electrical Code Com- mittee on each proposal that had been made to revise the 1965 Code. Subsequently, the various Code-Making Panels finalized their recom- mendations and their reports were processed through the Correlating Committee of the National Electrical Code Committee. This was pre- paratory to the formal presentation of this 1968 Edition of the National Electrical Code in Volume 2 of the 1968 NFPA TECHNICAL COM- MITTEE REPORTS. This latter publication was circulated tp all members of the National Electrical Code Committee, to other interested NFPA members, and offered to the public through technical releases in the in- 70-ii NATIONAL ELECTRICAL CODE terested trade papers.The action of the 1968 NFPA Annual Meeting as to the adoption of the 1968 Edition is recorded in the PROCEEDINGS of that Meeting published by the Association in the September 1968 issue of Fire Journal. Coincident with the above processing procedures, each of the Code- Making Panels and the Chairman of the Correlating Committee re- ported their recommendations to meetings of the Electrical Section at both the 1967 and 1968 NFPA Annual Meetings.The Electrical Section (See Rules of Procedure, Appendix) thus had opportunity to discuss and review the report of the National Electrical Code Committee prior to the adoption of this Edition of the Code by the Association. Other Printings This 1968 Edition of the National Electrical Code is also printed by the National Fire Protection Association in Volume 5 of the NATIONAL FIRE CODES.This Volume also contains the NFPA Standard for the Pro- tection of Electronic Computer/Data Processing Equipment (NFPA No. 75), the Standard for Essential Electrical Systems for Hospitals (NFPA No. 76), the Electrical Standard for Metalworking Machine Tools (NFPA No. 79), and the Standard for Purged Enclosures for Electrical Equipment in Hazardous Locations (NFPA No. 496). This Volume (one of ten) is issued annually with the other 190 Standards of the Association and provides those interested with a desk and library compendium of all current Standards issued by the Association. A"One- and Two-Family Residential Occupancy Electrical Code" is being prepared under authority granted by the Correlating Committee of the National Electrical Code Committee. This document is an abridged version of this text, edited only as dictated to eliminate extraneous material not of concern to this type occupancy, and to place in the text only the more popular types of wiring methods,not to exclude any other type authorized by the complete Code. The Compson Code Company of Lansing, Michigan offers a sepa- rate printing of this Edition of the Code under an agreement with the Association. The NFPA HANDBOOK OF THE NATIONAL ELECTRICAL CODE is pub- lished by The McGraw-Hill Book Company,Inc.,330 West 42nd Street, New York, New York 10036. This text is prepared by the Secretary of the National Electrical Code Committee who is the NFPA Electrical Field Service Engineer. First Printing,Aug.1968;Second Printing,Sept.1968;Third Printing,Dec.1968 Copyright © 1968 National Fire Protection Association This publication is copyrighted © by the National Fire Protection Asso- ciation. Permission is granted to republish in full the material herein in laws, ordinances, regulations, administrative orders or similar documents issued by public authorities. All others desiring permission to reproduce this ma- terial in whole or in part shall consult the National Fire Protection Asso- ciation. Printed in U.S.A. 70-iii TABLE OF CONTENTS ARTICLE PAGE ARTICLE PAGE 90 Introduction 1 357 Structural Raceways 145 358 Cellular Concrete Floor Chapter 1. General Raceways 146 100 Definitions 4 362 Wireways 148 364 Busways 149 110 General 13 I 365 Cablebus 150 370 Outlet,Switch and Junction Chapter 2. Wiring Design and Boxes, and Fittings 152 Protection 373 Cabinets and Cutout Boxes 158 200 Use and Identification of 374 Auxiliary Gutters 161 384 Switches 163 Grounded Conductors ._.. 18 384 Switchboards and 210 Branch Circuits 20 Panelboards 165 215 Feeders 27 390 Prefabricated Buildings .. 169 220 Branch Circuit and Feeder Calculations 28 Chapter 4. Equipment for 230 Services 39 General Use 240 Overcurrent Protection 54 250 Grounding 61 400 Flexible Cords and Cables 170 280 Lightning Arresters 80 4402 Fixture Wires 180 0 Lighting Fixtures,Lamp- Chapter 3. Wiring Methods and holders,Lamps,Recep- Materials tacles and Rosettes 184 422 Appliances 197 300 Wiring Methods—General 424 Fixed Electric Space Heat- Requirements 82 ing Equipment 203 310 Conductors for General 430 Motors,Motor Circuits and Wiring 88 Controllers 211 318 Continuous Rigid Cable 445 Generators 247 Supports 110 450 Transformers and Trans- 320 Open Wiring on Insulators 113 former Vaults 248 324 Concealed Knob-and- 460 Capacitors 254 Tube Work 116 470 Resistors and Reactors 256 328 Bare-Conductor Feeders .... 117 480 Storage Batteries 257 330 Mineral Insulated-Metal Sheathed Cable 118 Chapter 5. Special Occupancies ' 331 Aluminum Sheathed Cable 119 500 Hazardous Locations 260 334 Metal-Clad Cable 120 501 Class I Installations- 336 Nonmetallic Sheathed Hazardous Locations 264 Cable 123 502 Class II Installations- 338 Service-Entrance Cable 125 Hazardous Locations 274 339 Underground Feeder and 503 Class III Installations— Branch Circuit Cable ..._ 126 Hazardous Locations 283 342 Nonmetallic Extensions 127 510 Hazardous Locations- 344 Underplaster Extensions .._ 129 Specific 287 346 Rigid Metal Conduit 130 511 Commerical Garages, 347 Rigid Nonmetallic Conduit 133 Repair and Storage _....... 287 348 Electrical Metallic Tubing_. 136 512 Residential Storage Garages 290 350 Flexible Metal Conduit 138 513 Aircraft Hangars 290 351 Liquidtight Flexible 514 Gasoline Dispensing and Metal Conduit 139 Service Stations 294 352 Surrffacee lRaceways 140 515 Bulk-Storage Plants 295 516 Finishing Processes 298 Nonmetallic 140 517 Flammable Anesthetics 302 353 Multioutlet Assembly 141 520 Theaters and Assembly 354 Underfloor Raceways 142 Halls 305 356 Cellular Metal Floor 530 Motion-Picture Studios and Raceways 143 Similar Locations 312 70-iv NATIONAL ELECTRICAL CODE ARTICLE PAGE ARTICLE PAGE 540 Motion-Picture Projectors__ 315 750 Stand-By Power Generation 550 Mobile Homes 317 Systems 391 551 Travel Trailers 325 555 Boat Harbor Wiring 330 Chapter 8. Communication Systems Chapter 6. Special Equipment 800 Communication Circuits .... 393 810 Radio and Television 600 Electric Signs and Outline Equipment 398 Lighting 331 820 Community Antenna Tele- 610 Cranes and Hoists 337 vision and Radio Distribu- 620 Elevators,Dumbwaiters, tion Systems 403 Escalators,and Moving Walks 348 Chapter 9. Tables and 630 Electric Welders 348 pExamples 640 Sound-Recording and Tables 407 Similar Equipment 352 Examples 421 645 Data Processing Systems.._. 354 650 Organs 356 660 X-Ray Equipment 357 Index 665 Induction and Dielectric Heating Equipment 360 Index 431 670 Metal Working Machine Tools 365 Appendix 680 Swimming Pools 366 Rules of Procedure Chapter 7. Special Conditions Electrical Section 457 National Electrical Code 700 Emergency Systems 370 Committee 458 710 Over 600 Volts—General._._ 374 Tentative Interim Amendments 460 720 Circuits and Equipment Interpretation Procedure 461 • Operating at Less Than Timetable for 1971 50 Volts 380 Code 463 725 Remote-Control,Low- Method of Submitting Proposal Energy Power,Low-Voltage to Revise the National Elec- Power and Signal trical Code 464 Circuits 381 Tentative Interim Amendments 730 Outside Branch Circuits Nos. 146 and 148 465 and Feeders 387 Order Form 467 70-v National Electrical Code Committee This Committee is organized as a Sectional Committee (desig- nated C1) of the United States of America Standards Institute with the National Fire Protection Association acting as Sponsor. Personnel Roster Corrected to June 10, 1968 Electrical Correlating Committee Richard Lloyd,Chairman, Underwriters'Laboratories,Inc., 1285 Walt Whitman Rd.,Melville,L.I.,N.Y. 11746 Baron Whitaker, Vice Chairman, Underwriters'Laboratories,Inc.,207 East Ohio St.,Chicago,Ill.60611 Frank Stetka,t Secretary, P.O.Drawer M,Laurel,Md.20810 Walter R.Stone,t Editorial Coordinator, National Fire Protection Association,60 Batterymarch St.,Boston,Mass.02110 Miss Gladys H.Mueller,t Recording Secretary, Underwriters'Laboratories,Inc., 1285 Walt Whitman Rd.,Melville,L.I.,N.Y. 11746 E. A. Brand, 131 Monroe Drive, Buffalo, W.A.McAdams,General Electric Co., 570 N.Y. 14221 Lexington Ave., New York, N.Y. 10022 Alternate: Howard R. Stevenson, De- Alternate: Kent P. Stiner, Bulldog Elec- troit Edison Co., 2000 Second Ave., De- tric Products Division, I-T-E Imperial troit,Mich.48226 Corp., Box 177, R. Park Annex, Detroit, Swaffield Cowan,Factory Insurance Assn., Mich.48232 131 Providence Road,Charlotte,N.C.28207 Richard W. Osborn, Osborn Electric Co., C. F. Hedlund, Factory Mutual Engineer- 5516 S.Kingshighway,St.Louis,Mo.63109 ing Corporation, 1151 Boston-Providence Alternate: N. Ellis Cannady, Jr., M. B. Turnpike,Norwood,Mass.02062 Haynes Electric Co.,Box 1250,Asheville, L. E. LaFehr, Managing Director, Interna- N.C.28802 tional Assn. of Electrical Inspectors, 201 L. H. Sessler,Bell Telephone Laboratories, E.Erie St.,Rm.300,Chicago,Ill.60611 Inc., Mountain Ave.,Room 5A113,Murray Hill,N.J.07971 The Electrical Correlating Committee has an executive and editorial function with re- spect to the Code-Making Panels responsible for the National Electrical Code. Each Code- Making Panel listed on this and the next seven pages is responsible for the portions of the Code as indicated after their designation. t Non-voting member. Panel No. 1 —Articles 90, 100, 110 H.P.Michener,Chairman, National Electrical Manufacturers Assn.,155 East 44th St.,New York,N.Y. 10017 Carroll A. Badeau, The Thomas & Betts Alternate: C.J.Hart,National Electrical Co.,36 Butler St.,Elizabeth,N.J.07207 Contractors Assn., Inc., 1730 Rhode Is- E. A. Brand, 131 Monroe Drive, Buffalo, land Ave.,N.W.Washington,D.C.20036 N.Y. 14221 W. A. Farquhar, Underwriters' Laborato- L. E. LaFehr, International Assn. of Elec- ries,Inc.,1285 Walt Whitman Rd.,Melville, trical Inspectors, 201 E. Erie St., Chicago, L.I.,N.Y. 11746 III.60611 R. L. Higgins,National Electrical Contrac- tors Assn., Inc., 1730 Rhode Island Ave., H. R. Stevenson,The Detroit Edison Co., N.W.Washington,D.C.20036 2000 Second Ave.,Detroit,Mich.48226 Panel No.2—Articles 200,210,215,220,550,551,700,750 Examples Nos. 1 through 7 Kent P.Stiner,Chairman, Bulldog Electric Products Division, I-T-E Imperial Corp.,Box 177,R.Park Annex, Detroit,Mich.48232 Russell S.Davis,Secretary (nonvoting), I-T-E Imperial Corp.,Bulldog Electric Products Div.,P.O.Box 177, Detroit,Mich.48232 (Alternate to Kent P.Stiner) 70-vi NATIONAL ELECTRICAL CODE T. P. Branch, 2800 Dennis Ave., Silver H. B. Love," Chief, Bureau of Electrical Spring,Md.90202 Inspection, 418 City-County Bldg., Detroit, Swaffield Cowan, Factory Insurance Mich. 48226 (Liaison representative NFPA Assn., 131 Providence Rd.,Charlotte, N.C. Committee on Mobile Homes and Travel 28207 Trailers) Alternate: Norbert J. Patek, Factory J. W. Mannix, Inspection of Wires Dept., Insurance Assn., 300 W. Adams St., 450 Concord Ave.,Belmont,Mass.02178 Chicago,Ill.60606 W. H. Martin,Jr.,Bell Telephone Labora- D.C.Fleckenstein,Industry Codes&Stan- tories, Inc., Whippany Road, Whippany, dards, Engineering Services, General Elec- N.J.07981 tric Co., 1 River Road, Schenectady, N.Y. T. Van Arsdale, Local Union No. 3, 12305 I.B.E.W., 130 E.25th St.,New York,N.Y. Alternate: H. P. Michener, National 10010 Electrical Mfrs. Assn., 155 East 44th St., Harold Ware,c/o Belco, Inc., Box 19158, New York,N.Y. 10017 S.W.Station,Oklahoma City,Okla.73119 Roy Hudenburg,* Kiff, Voss & Franklin, O. Zimmerman, Portland General Elec- 230 Park Ave.,New York,N.Y.10017 tric Co., 621 S.W. Alder St., Portland, Cecil T.Jones,South-Eastern Underwriters Ore.,97205 Assn.,P.O.Box 5048,Atlanta,Ga.30303 Alternate: John P.Barron,Dallas Power L. M. Kline, Underwriters' Laboratories, &Light Co., 1506 Commerce St., Dallas, Inc., 1285 Walt Whitman Rd., Melville, Texas 75201 L.I.,N.Y.11746 *Liaison Representative of Committee on Hospitals—Vote Limited **Liaison Representative of Committee on Mobile Homes and Travel Trailers—Vote Limited Panel No.3—Articles 230,600,730 Robert A.Jutstrom,Chairman, New England Electric System,441 Stuart St.,Boston,Mass.02116 H.Bounds,Local Union No.570,I.B.E.W., L. F. Lynch, Chief Electrical Safety Engr., 750 S.Tucson Blvd.,Tucson,Ariz.85716 State of Oregon, Bureau of Labor, 1400 Frank G.Camus,C&C Electric Co., 1302 S.W.Fifth Ave.,Portland,Ore.97201 Louisiana Ave.,Shreveport,La.71101 Joseph J. Reevie, Reynolds Metals Co., W. L. Gregory, American Electric Power Front&Lloyd Sts.,Chester,Pa.19013 Service Corp., 2 Broadway, New York, B.Z.Segall,2801 Joseph St.,New Orleans, N.Y. 10008 La.70115 Lorne M. Holdaway, Electric Operations H.I.Stanback,Square D Co., 1601 Mercer & Standards Div., U.S. Dept. of Agricul- Rd.,Lexington,Ky.40505 ture, Rural Electrification Administration, Alternate: Francis B. Murray, MurrayWashington,D.C.20250 y A. D. Lutgens,Underwriters'Laboratories, Manufacturing Corp., 113 South Service Inc., 1285 Walt Whitman Road, Melville, Rd.,Jericho,L.I. N.Y. 11753 L.I.,N.Y.11746 Panel No.4—Article 240 R.W.Seelbach,Chairman, Underwriters'Laboratories,Inc.,1285 Walt Whitman Rd.,Melville,L.I.,N.Y.11746 Charles Bangert, Jr., Circuit Protective newal, 393 Seventh Ave., New York, Devices Dept., General Electric Co., 41 N.Y.10001 Woodford Ave.,Plainville,Conn.06062 Milton Minto, MacNutt Electric Co., Inc., J. A. Bussmann, Jr. Bussmann Mfg. Div., 420 Lexington Ave., New York, N.Y. McGraw Edison Co., 2536 W. University 10017 Ave.,St.Louis,Mo.63107 R. A. Niedermeyer, Electrical Division, Swaffield Cowan, Factory Insurance Room 403,City Hall,1220 S.W.Fifth Ave., Assn., 131 Providence Rd.,Charlotte, N.C. Portland,Ore.97204 28207 George E. Schell, Underwriters' Labora- Alternate: Norbert J. Patek, Factory tories, Inc., 1285 Walt Whitman Rd., Mel- Insurance Assn., 300 W. Adams St., ville, L.I.,N.Y. 11746 (Alternate to R. W. Chicago, III.60606 Seelbach) C. F. Hedlund, Factory Mutual Engineer- H. I. Stanback, Square D Co., 1601 Mer- ing Corporation, 1151 Boston-Providence cer Rd.,Lexington,Ky.40505 Turnpike,Norwood,Mass.02062 Alternate: Walter F. Huette, Allen- W. E. Macbeth, Tecumseh Products Co., Bradley Co., 1201 S.Second St.,Milwau- Tecumseh,Mich.49286 kee,Wis.53204 Alternate: Frederick J. Reed, Air Con- George J. Yanda, Metering & Under- ditioning & Refrigeration Institute, 1815 ground Dept., Cleveland Electric Illumina- N. Fort Myer Drive, Arlington, Va. ting Co., Box 5000,Cleveland,Ohio 44101 22209 Alternate: R. P. Fogarty, Consolidated Fred Mayglothling, Building Codes Bu- Edison Co. of New York, Inc.,4 Irving reau, Div.of Housing&Community Re- Place,New York,N.Y.10003 NFPA CODE COMMITTEE 70-vii Panel No.5—Articles 250,280,555 L.H.Sessler,Chairman, Bell Telephone Laboratories,Inc.,Mountain Ave.,Room 5A113,Murray Hill,N.J.07971 J. L. Bennett, Black & Decker Co., Tow- Agriculture, Rural Electrification Adminis- son,Md.21204 tration,Washington,D.C.20250 Alternate: L.C. Pratt,Millers Falls Co., R. H. Kaufmann,2208 Dean St., Schenec- Greenfield,Mass.01301 lady,N.Y. 12309 K. R. Dennis, Northwest Electric Co., 420 Alternate: W. F. Hildebrand, General Yale Ave.,N.,Seattle,Wash.98109 Electric Co., 1 River Rd., Schenectady, W. A. Farquhar, Underwriters' Labora- N.Y. 12305 tories, Inc., 1285 Walt Whitman Rd., Mel- N.N.Koch,Ohio Edison Co.,Akron,Ohio Mel- ville,L.L,N.Y.11746 44308 A. G. Forcier, Factory Insurance Assn., 85 Alternate: J. C. Young, New Orleans Woodland St.,Hartford,Conn.06102 Public Service, Inc., Box 60340, New Alternate: C. W. Conaway, Factory In- Orleans,La.70160 surance Assn., 465 California St., San Francisco,Calif.94104 Joseph J. Reevie, Reynolds Metals Co., Leland J. Hall, Mill Mutual Fire Preven- Front&Lloyd Sts.,Chester,Pa. 19013 tion Bureau,2 N.Riverside Plaza,Chicago, R. E. Ward, Chief, Electrical Inspection Ill.60606 Section, Division of Fire Prevention, 202 C. F. Hedlund, Factory Mutual Engineer- Capitol Towers Bldg., Nashville, Tenn. ing Corporation, 1151 Boston-Providence 37219 Turnpike,Norwood,Mass.02062 Alternate: P.N.Bryant,Chief Electrical Lorne M.Holdaway,Electric Operations& Inspector, 4368 Mountaindale Rd., Bir- Standards Division, U.S. Department of mingham,Ala.35213 Panel No.6—Articles 300,310,400,402 Tables Nos.5 through 9 W.R.Milby,Chairman, Detroit Edison Co.,2000 Second Ave.,Detroit,Mich.48226 W Apgar,American Insurance Assn., I.B.E.W., 55 Fillmore St., San Francisco, 85 John St.,New York,N.Y.10038 Calif.94117 Wm. P. Hogan, Jr., Bureau of Electrical H.E.Reymers,Underwriters'Laboratories, Inspection, 320 North Clark St., Chicago, Inc., 1285 Walt Whitman Rd., Melville, Ill.60610 L.I.,N.Y. 11746 Roger S.Keith,Kaiser Aluminum&Chem, S.J.Rosch,324 Woodworth Ave.,Yonkers, ical Corp., Electrical Products Div., 500 N.Y. 10701 Wood St.,Bristol,R.I.02809 C. H. Seaberg,Wire& Cable Dept., Gen- A. F. KnicKrehm, The KnicKrehm Co., eral Electric Co., 1285 Boston Ave.,Bridge- 3007 W. Temple St., Los Angeles, Calif. port,Conn.06602 90026 Alternate: L. H. Selden, Rome Cable Alternate: S. F. Hill,Hill Electrical Co., Div., Cyprus Mines Corp., P.O. Box 71, 1809 Hill Drive, Los Angeles, Calif. Rome,N.Y. 13440 90041 B. Z. Segall, 2801 Joseph St., New Or- W. M. Reedy, Local Union No. 6, leans,La.70115 Panel No.7—Articles 320,324,328,330,331,334,336,338,339, 342,344,390,645 George B.Newbold,Chairman, Middle Department Association of Fire Underwriters,6th&Chestnut Sts., Philadelphia,Pa. 19106 T. P. Branch, 2800 Dennis Ave., Silver Mines Corp., P.O. Box 71, Rome, N.Y. Spring,Md.20902 13440 C. J. Hart, National Electrical Contractors Alternate: E. G. Driscoll, Phelps Dodge Assn., 1730 Rhode Island Ave., N.W., Copper Products Corp., Yonkers, N.Y. Washington,D.C.20036 10702 Hazen E. House,Aluminum Co. of Amer- R. E. L. Shirley, Georgia Power Co., P.O. ica, 1500 Alcoa Bldg.,Pittsburgh,Pa. 15219 Box 4545,Atlanta,Ga.30302 Cecil T.Jones,South-Eastern Underwriters Alternate: Walter J. Stepien, Jr., Ni- Assn.,Box 5048,Atlanta,Ga.30303 agara Mohawk Power Corp., 300 Erie Blvd.,West,Syracuse,N.Y.13202 A. D. Lutgens,Underwriters'Laboratories, Robert L. Thompson, Electrical Adminis- Inc., 1285 Walt Whitman Rd., Melville, trative Board, State of New Mexico, 505 L.I.,N.Y. 11746 Marquette, N.W., Room 1020, Albuquer- W. J. Richard, 14 High St., Brandon, Vt., que,N.M.87101 05733 John H. Trout, International Business Ma- L. H. Selden, Rome Cable Div., Cyprus chines Corp.,Armonk,N.Y.10504 70-viii NATIONAL ELECTRICAL CODE Panel No.8—Articles 318,346,347,348,350,351,352, 353,354,356,357,358,362,364,365 Tables Nos. 1 through 4 J.L.Adams,Chairman, Union Electric Co.,P.O.Box 149,St.Louis,Mo.63166 D. L. Breting, Underwriters' Laboratories, Thomas V. Pope, Kaiser Aluminum & Inc.,207 E.Ohio St.,Chicago,III.60611 Chemical Sales, Inc., 300 Lakeside Drive, D. J. Diamond, Local Union No. 58, Oakland,Calif.94612 I.B.E.W., General P.O. Box 699, Detroit, W. F. Reed, Dept. of Bldg. & Safety, 400 Mich.48232 West 8th St.,Santa Ana,Calif.92701 W. C. Kessler, Long Island Lighting Co., A. C. Veit, 819 N. Olive St., Alhambra, 1650 Islip Ave., Brentwood, N.Y. 11717 Calif.91801 (Alternate to J.L.Adams.) H. H. Watson, BurndyCorp.,W. N. Livermore, E. I. duPont de Conn.06852 Norwalk, Nemours&Co.,Wilmington,Del.19898 Alternate: L. H. Selden, Rome Cable Milton Lounsbury, Albany Div., New Div., Cyprus Mines Corp., P.O. Box 71, York Board of Fire Underwriters, 75 State Rome,N.Y.13440 St.,Albany,N.Y. 12207 Walter G. Wells, American Iron & Steel Milton Minto, MacNutt Electric Co., 420 Institute, 633 Third Ave., New York, N.Y. Lexington Ave.,New York,N.Y.10017 10017 Robert H. Murphy, The Wiremold Co., Alternate: James C. Spence, American Hartford,Conn.06110 Iron & Steel Institute, 633 Third Ave., New York,N.Y.10017 Panel No.9—Articles 370,373,374,380,384 William P.Hogan,Jr.,Chairman, Chief Electrical Inspector,Bureau of Electrical Inspection,320 North Clark St., Chicago,Ill.60610 Richard G. Biermann,Biermann's Univer- John W. Hager,c/o Dept. of Water Sup- sity Electric Co.,Inc.,2300 University Ave., ply, Gas & Electricity, Tremont & Arthur Des Moines,Iowa 50311 Ayes.,Bronx,N.Y. 10457 M. F. Borleis, Baltimore Gas & Electric O. J. Moses, Factory Mutual Engineering Co.,Lexington Bldg.,Baltimore,Md.21203 Corp., 1151 Boston-Providence Turnpike, C. J. Falk, General Electric Co., 1260 Norwood,Mass.02062 Boston Ave.,Bridgeport,Conn.06602 Nathan H. Rudolph, Asst. Chief Engr., Alternate: A. D. Vanderbilt, Crouse- All-Steel Equipment, Inc., Aurora, Ill. Hinds Co.,Syracuse,N.Y.13201 60507 R. H. Fries, Underwriters' Laboratories, Wm. F. Seubert,Mgr., Engrg.&Develop- Inc., 1285 Walt Whitman Rd., Melville, ment Dept., Circle F. Industries, Inc., P.O. L.I.,N.Y. 11746 Box 591,Trenton,N.J.08604 Panel No.10—Articles 410,422,424,680 B.Z.Segall,Chairman, 2801 Joseph St.,New Orleans,La.70115 George W.Flach,Vice Chairman, Room 7E04,City Hall,Civic Center,New Orleans,La.70112 Cliff Atkins,20140 N.E. Sandy,Troutdale, A. B. Newton, York Div., Borg-Warner Ore.97060 Corp., P.O. Box 1592, York, Pa. 17405 Clement T.Baxter,Sylvania Electric Prod- Alternate: Frederick J. Reed, Air Con- ucts, Inc., 100 Endicott St., Danvers,Mass. ditioning & Refrigeration Institute, 1815 01923 N. Fort Myer Drive, Arlington, Va. Alternate: Frank E. Devlin, Westing- 22209 house Electric Corp., 1421 State St., Ernest H. Salter,* Electrical Testing Lab- Bridgeport,Conn.06602 oratories, Inc., 2 E. End Ave., New York, Second Alternate: Robert L. Boyd, Cli- N.Y. 10021 mate Control Div.,The Singer Company, J. M. Turnbull, Western Massachusetts 62 Columbus St., Auburn, N.Y. 13021 Electric Company, 174 Brush Hill Ave., Leslie E. Bley, Noone Electric Co., Inc., West Springfield,Mass.01089 270 Fredhilton Pass, Baltimore, Md. 21229 Alternate: Ray Vertovec, Common- W. H. Farrell,Underwriters'Laboratories, wealth Edison Co., 72 W. Adams St., Inc., 333 Pfingsten Rd., Northbrook, 111. Chicago,Ill.60609 60062 Second Alternate: J. C. Young, New Paul H.Lawrenz,American Motors Corp., Orleans Public Service Inc., Box 60340, 14250 Plymouth Road,Detroit,Mich.48232 New Orleans,La.70160 Alternate: Herbert Phillips, Assn. of Home Appliance Manufacturers, 20 North Wacker Drive, Chicago, Ill. 60606 *Voting privileges limited to Article 410. NFPA CODE COMMITTEE 70-ix Panel No.11—Articles 430,445,Example No.8 Richard W.Osborn,Chairman, Osborn Electric Co.,5516 S.Kingshighway,St.Louis,Mo.63109 N.Ellis Cannady,Jr.,Alternate Chairman, M.B.Haynes Electric Co.,Box 1250,Asheville,N.C. J. A. Bussmann,Jr. Bussmann Mfg. Div., W. F. Schacht, Factory Insurance Assn., McGraw Edison Co., 2536 W. University 300 W.Adams St.,Chicago,Ill.60606 Ave.,St.Louis,Mo.63107 Alternate: Clair W. Conaway, Factory Karl M. Gerteis, Carrier Air Corp., Syra- Insurance Assn., 465 California St., San cuse,N.Y. 13201 Francisco,Calif.94106 Alternate: Frederick J. Reed, Air Con- Marvin L. Schmidt, General Electric Co., ditioning & Refrigeration Institute, 1815 1701 College St.,Fort Wayne,Ind.46804 N. Fort Myer Drive, Arlington, Va. Alternate: R. N. Eck, Cutler Hammer, 22209 Inc., 4201 N. 27th St., Milwaukee, Wis. R. T. Hauck, City Chief Electrical Inspec- 53216 tor, 1829 Brownsboro Road,Louisville,Ky. Second Alternate: Carl E. Gryctko, 40206 I-T-E Imperial Corp., 1924 Hamilton H. B. Love,Chief Electrical Inspector, Bu- St.,Philadelphia,Pa. 19130 reau of Electrical Inspection, Rm. 418, R. W. Seelbach, Underwriters' Labora- City-County Bldg.,Detroit,Mich.48226 tories, Inc., 207 E. Ohio St., Chicago, Ill. G. B. M. Robertson, Philadelphia Electric 60611 Co., 2301 Market St., Philadelphia, Pa. A. P. White, Texas Instruments, Inc., 34 19103 Forest St.,Attleboro,Mass.02703 C. E. Schaad, New York Board of Fire Underwriters,85 John St.,New York,N.Y. 10038 Panel No. 12—Articles 610,620,630,670 E.E.Carlton,Chairman, Dept.of Industrial Relations,Div.of Industrial Safety,P.O.Box 603, San Francisco,Calif.94101 H. B. Buckingham, United States Steel John Lusti, Otis Elevator Co., 260 11th Corp.,P.O.Box 599,Fairfield,Ala.35064 Ave.,New York,N.Y.10001 G. M. Chapple, International Brotherhood William J.Meese,Codes&Standards Sec- of Electrical Workers,Local Union No. 38, tion, National Bureau of Standards, Wash- 10716 South Highland Ave., Garfield ington,D.C.20234 Heights,Ohio 44125 A. H. Myles, Square D Co., HI Division, C. F. Hedlund, Factory Mutual Engineer- 4500 Lee Road,Cleveland,Ohio 44128 ing Corporation, 1151 Boston-Providence A. A. Rutkowski, Harnischfeger Corp., Turnpike,Norwood,Mass.02062 4400 W. National Ave., Milwaukee, Wis. George Helfer, Thelco Electrical Con- 53246 tractors, Inc., 655 Caleb's Path, Haup- D.F.Simmons,Pacific Gas&Electric Co., pauge,N.Y. 11787 245 Market St.,San Francisco,Calif.94103 Panel No. 13—Articles 450,460,470,710 C.F.Hedlund,Chairman, Factory Mutual Engineering Corporation,1151 Boston-Providence Turnpike, Norwood,Mass.02062 R. B. Boyd, Jr., State Ins. Dept., State Gordon R. Messmer, U.S. Department of Office Bldg.,Raleigh,N.C.27602 Agriculture, Rural Electrification Adminis- E. E. Carlton, Dept. of Industrial Rela- tration,Washington,D.C.20250 [ions, Div. of Industrial Safety, P.O. Box William A. Muska, Tony Muska Electric 603,San Francisco,Calif.94101 Co.,700 Grand Ave.,St.Paul,Minn.55105 R. H.Kaufmann, 2208 Dean St., Schenec- G. B. Newbold, Supt., Electrical Dept., tady,N.Y. 12309 Middle Department Assn. of Fire Unds., R. M. McCuistion, Houston Lighting & 6th&Chestnut Sts.,Philadelphia,Pa. 19106 Power Co.,P.O. Box 1700,Houston,Texas W. E. Thomas, Westinghouse Electric 77001 Corp., RED Center, Bldg. 501, Pittsburgh, Alternate: L. H.Bell,Virginia Electric& Pa. 15235 Power Co., P.O. Box 1194, Richmond, Alternate: Glenn Bates, Power Circuit Va.23209 Breaker Div., Westinghouse Electric Corp., One Market St., San Francisco, Calif.94103 Panel No. 14—Articles 480,500-503,510-517 L.J.Hall,Chairman, Mill Mutual Fire Prevention Bureau,2 North Riverside Plaza,Chicago,III.60606 S. P. Axe, Atlantic Richfield Co., 3144 David T. Gorrell, Gorrell Electric Co., Passyunk Ave.,Philadelphia,Pa. 19145 P.O.Box 866,Parkersburg,W.Va.26101 70-x NATIONAL ELECTRICAL CODE S. F. Henderson, Westinghouse Electric C. E. Schaad, New York Board of Fire Corp.,P.O.Box 225,Buffalo,N.Y.14240 Underwriters, 85 John St.,New York,N.Y. Alternate: H. A. Norberg,Nelson Elec- 10038 tric Division, Sola Basic Industries, P.O. Kent P. Stiner,* Bulldog Electric Products Box 726,Tulsa,Okla.74101 Division, I-T-E Imperial Corp., Box 177, E. B. Hoge,Eastern Air Lines, Miami In- R.Park Annex,Detroit,Mich.48232 ternational Airport,Miami,Fla.33418 W. C. Westerberg, Underwriters' Labo- Robert P. Howell, Standard Oil Co. of ratories, Inc., 207 E. Ohio St., Chicago, California, P.O. Box 3069, San Francisco, III.60611 Calif.94120 G.A.Wintz,City Electrical Inspector,City Charles F. Kisselstein, Crouse-Hinds Co., Hall,Rm.495,Los Angeles,Calif.90012 P.O.Box 131,Syracuse,N.Y.13201 Otto F.Zedler,Jr.,Humble Pipe Line Co., A.H.McKinney,Engineering Service Div., P.O.Drawer 2220,Houston,Texas 77002 E. I. duPont de Nemours& Co., Wilming- Fred J. Zeleny, Factory Insurance Assn., ton,Del. 19898 300 W.Adams St.,Chicago,III.60606 Alternate: J. C. Norton, Union Carbide Alternate: Clair W. Conaway, Factory Corp., P.O. Box 8361, South Charleston, Insurance Assn., 465 California St., San W.Va.25303 Francisco,Calif.94106 O. J. Moses, Factory Mutual Engineering Corporation, 1 151 Boston-Providence Turn- *Liaison Representative—vote limited pike,Norwood,Mass.02062 to items on hospitals. F. S. Rittenhouse, Consumers Power Co., 212 W. Michigan Ave., Jackson, Mich. 49504 Panel No.15—Articles 520,530,540,640,650,810,820 K.S.Geiger,Chairman, Underwriters'Laboratories,Inc.,207 E.Ohio St.,Chicago,Ill.60611 R.G.Biermann,Biermann's Univ.Electric Alternate: A. C. Veit, 819 North Olive Co.,Inc.,2300 University Ave.,Des Moines, St.,Alhambra,Calif.91801 Iowa 50311 Wm. M. Riches, CBS Television Network J.A.Caffaux,Electronic Industries Assn., Broadcast Center, 51 W. 52nd St., New 2001 Eye St., N.W., Washington, D.C. York,N.Y. 10019 20006 Alternate: George T. Anderson, CBS John G. Degenkolb, 5940 Echo St., Los Television Network, Television City, Angeles,Calif.90042 Hollywood,Calif.90036 L.H.Sessler,Bell Telephone Laboratories, Kent Glenn, Southern California Edison Inc., Mountain Ave., Room 5A113, Mur- Co., Edison Bldg., Los Angeles, Calif. ray Hill,N.J.07971 90053 W. A. Sunter, Harvey Hubbell, Inc., V. C. Holloway, Interstate Electric Co., Bridgeport,Conn.06602 6444 N.E. Fourth Ave., Miami, Fla. 33132 Alternate: Jack Gaines, Sierra Electric p., 151 Fig H.A.Kliegl,Kliegl Bros.,32-32 48th Ave., 85,rGardenaa,,Calif.South90247 ueroa, P.O. Box Long Island City,N.Y.11101 L. O. Trim, Electrical Inspection Dept., W. F. Miner,Revue Studios, 3900 Lanker- City Hall, 275 E. Olive Ave., Burbank, sham Blvd.,Universal City,Calif.91608 Calif.91503 Panel No. 16—Articles 720,725,800 (Appointment of Chairman Pending) James B. Eppes,Jr., Station Equipment& Fred Mayglothling, Building Codes Bu- Protection Engr., Rural Electrification Ad- reau, Division of Housing & Community ministration,Washington,D.C.20250 Renewal, 393 Seventh Ave., New York, C. M. Garner, White-Rodgers Co., 9797 N.Y. 10001 Reavis Rd.,St.Louis,Mo.63123 L. H. Sessler,Bell Telephone Laboratories, Alternate: Irving Mande, Edwards & Inc.,Mountain Ave.,Room 5A113,Murray Co.,Inc.,Norwalk,Conn.06856 Hill,N.J.07971 Boyd A.Hartley,Fire Protection Engineer- Leo Wits, Continental Electrical Construc- ing Dept., Illinois Institute of Technology, tion Co., 3540 N. Southport Ave., Chicago, Chicago,Ill.60616 Ill.60657 J. C. Hewitt, Washington State Electrical Rene H. Yerke, Underwriters' Labora- Inspector, 114 North Columbia Way,Olym- tories, Inc., Pfingsten Rd., Northbrook, Ill. pia,Wash.98501 60062 NFPA CODE COMMITTEE 70-xi Panel No. 17—Articles 660,665 W.A.McAdams,Chairman, General Electric Co.,570 Lexington Ave.,New York,N.Y. 10022 L.H.Horn,Vice-Chairman, Underwriters'Laboratories,Inc.,333 Pfingsten Rd.,Northbrook,Ill.60062 J. F. Cachat, The Ohio Crankshaft Co., Alternate: R. L. Sweeny, Standard X- 3800 Harvard Ave.,Cleveland,Ohio 44105 'Jay Div.,Cenco Instruments Corp.,2600 M. G. Folkes, Chief Electrical Inspector, S.Kostner Ave.,Chicago,III.60623 Bureau of Electrical Inspection, 501 N. 9th Scott W. Smith (Dr.), 10210 Grosvenor St.,Room 121,Richmond,Va.23219 Place, Rockville, Md.20852 George C. Hilstad, Electrical Builders, R. B. Swallow, Public Service Electric & Inc.,Mayville,N.D.58257 Gas Co., 80 Park Place, Newark, N.J. O. J. Moses, Factory Mutual Engineering 07101 Corporation, 1151 Boston-Providence Turn- pike,Norwood,Mass.02062 M. L. Young, Chief Electrical Inspector, George B.Myers,Picker X-Ray Corp.,595 7717 Gambrill Rd., Springfield, Va. 22150 Miner Road,Cleveland Heights,Ohio 44143 70-1 National Electrical Code NFPA No. 70; USAS C1-1968 ARTICLE 90—INTRODUCTION 90-1. Purpose. (a) The purpose of this Code is the practical safeguarding of per- sons and of buildings and their contents from hazards arising from the use of electricity for light, heat, power, radio, signalling and for other purposes. (b) This Code contains basic minimum provisions considered neces- sary for safety. Compliance therewith and proper maintenance will re- sult in an installation essentially free from hazard, but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use. Hazards often occur because of overloading of wiring systems by meth- ods or usage not in conformity with the Code. This occurs because initial wiring did not provide for increases in use of electricity. For this reason it is recommended that the initial installation be adequate and that reasonable provisions for system changes be made as may be required for future in- crease in the use of electricity. (c) This Code is not intended as a design specification nor an instruc- tion manual for untrained persons. 90-2. Scope. (a) Covered. It covers the electric conductors and equipment in- stalled within or on public and private buildings and other premises, including yards, carnival and parking lots, and industrial substations; also the conductors that connect the installations to a supply of elec- tricity, and other outside conductors adjacent to the premises; also mo- bile homes and travel trailers. (b) Not Covered. It does not cover (1) Installations in ships, watercraft, railway rolling stock, air- craft or automotive vehicles. (2) Installations underground in mines. (3) Installations of railways for generation, transformation, trans- mission or distribution of power used exclusively for operation of roll- ing stock or installations used exclusively for signaling and communica- tion purposes. (4) Installations of communication equipment under exclusive control of communication utilities, located outdoors or in building spaces used exclusively for such installations. (5) Installations under the exclusive control of electric utilities for the purpose of communication, metering or for the generation, control, transformation, transmission and distribution of electric energy located in buildings used exclusively by utilities for such purposes or 70-2 NATIONAL ELECTRICAL CODE located outdoors on property owned or leased by the utility or on public highways, streets, roads, etc., or outdoors by established rights on private property. (c) Special Permission. The authority having jurisdiction for en- forcing the Code may grant exception for the installation of conductors and equipment, not under the exclusive control of the electric utilities and used to connect the electric utility supply system to the service entrance conductors of the premises served, provided such installations are outside a building or terminate immediately inside a building wall. 90-3. Code Arrangement. This Code is divided into nine chapters. Chapters 1, 2, 3 and 4 apply generally; Chapters 5, 6 and 7 apply to special occupancies, special equipment, or other special conditions. The latter chapters supplement or amend the general rules. Chapters 1-4 apply except as amended by Chapters, 5, 6 and 7 for the particular con- ditions. Chapter 8 covers communications systems and is independent of the other chapters except where they are specifically referenced therein. Chapter 9 consists of tables and examples. 90-4. Definitions. Article 100 contains definitions of a number of terms that are used in two or more Articles. In general, terms used only in a single Article are defined in the Article concerned. For electrical terms not defined in the Code, refer to the USA Standard Definitions of Electrical Terms,USAS C-42-series. 90-5. Fundamental Rules. Throughout the Code are paragraphs which state only fundamentals or objectives of safeguarding. These are fol- lowed by paragraphs setting forth the recognized methods and detail by which the purpose and intent of the fundamental may be satisfied. Ac- cordingly, when employed, the rules stating a fundamental only will appear as the first paragraph of an Article or Section. 90-6. Interpretation. In order to promote uniformity of interpretation and application of this Code, the National Electrical Code Committee of the National Fire Protection Association has established a formal procedure for rendering interpretations in case of question. Applica- tions for interpretations should be addressed to the National Fire Pro- tection Association (see procedure for securing official interpretations of Code appearing in the Appendix). 90-7. Enforcement. This Code is intended to be suitable for manda- tory application by governmental bodies exercising legal jurisdiction over electrical installations and for use by insurance inspectors. The administrative authority supervising such enforcement of the Code will have the responsibility for making interpretations of the rules, for de- ciding upon the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules. 90-8. Examination of Equipment for Safety. For approval of specific items of equipment and materials covered by the Code, examinations for safety should be made under standard conditions, and the record made generally available through promulgation by organizations prop- erly equipped and qualified for experimental testing, inspections of the run of goods at factories, and service-value determination through field ARTICLE 90—INTRODUCTION 70-3 inspections. This avoids the necessity for repetition of examinations by different examiners, frequently with inadequate facilities for such work, and the confusion that would result from conflicting reports as to the suitability of devices and materials examined for a given purpose. It is the intent of the Code that factory-installed internal wiring or the construction of equipment need not be insl5ected at the time of installa- tion of the equipment except to detect alterations or damage if the equipment has been listed by an electrical testing laboratory, which is nationally recognized as having the facilities described above and which requires suitability for installation in accordance with the Code. 90-9. Wiring Planning. (a) It is recommended that electrical engineers and others when drawing plans and specifications make provision for ample raceways for wiring, spaces for equipment, and allowances for future increases in the use of electricity. In laying out an installation for constant- potential systems, provision should be made for distribution centers located in easily accessible places for convenience and safety of opera- tion. (b) It is elsewhere provided in this Code that the number of wires and circuits confined in a single enclosure be varyingly restricted. It is strongly recommended that electrical engineers and others who are planning installations provide similar restrictions wherever practicable, to the end that the effects of breakdowns from short-circuits or grounds, even though resulting fire and similar damage are confined to wires, their insulation and enclosures, may not involve entire services to premises nor interruptions of essential and independent services. 90-10. Revisions. It is customary to revise this Code periodically to conform with developments in the art and the result of experience, and the latest edition of the Code should always be used. 70-4 Chapter 1. General ARTICLE 100—DEFINITIONS General guides for this Article on Definitions include: (1) for simplicity, only definitions essential to the proper use of this Code are included; (2) only those terms used in two or more Articles are defined in full in Article 100, other definitions being defined in the individual Article where they ap- ply; (3) in general, NEC definitions will be the same as definitions in the latest revision of USAS C-42 series, "Definitions of Electrical Terms," and are so identified by an asterisk*. *Accessible: (As applied to wiring methods.) Not permanently closed in by the structure or finish of the building; capable of being re- moved without disturbing the building structure or finish. (See "Con- cealed"and"Exposed.") *Accessible: (As applied to equipment.) Admitting close approach because not guarded by locked doors, elevation or other effective means. (See"Readily Accessible.") Ampacity: Current-carrying capacity expressed in amperes. Anesthetizing Location: See Section 517-1(b). Appliance: An appliance is utilization equipment, generally other than industrial, normally built in standardized sizes or types, which is installed or connected as a unit to perform one or more functions such as clothes washing,air conditioning,food mixing,deep frying,etc. Appliance — Fixed: An appliance which is fastened or otherwise se- cured at a specific location. Appliance— Portable: An appliance which is actually moved or can easily be moved from one place to another in normal use. Appliance — Stationary: An appliance which is not easily moved from one place to another in normal use. Approved: Acceptable to the authority enforcing this Code. *Askarel: A synthetic nonflammable insulating liquid which, when decomposed by the electric arc, evolves only nonflammable gaseous mixtures. *Attachment Plug (Plug Cap) (Cap): An attachment plug is a device which, by insertion in a receptacle, establishes connection between the conductors of the attached flexible cord and the conductors connected permanently to the receptacle. *Automatic: Automatic means self-acting, operating by its own mechanism when actuated by some impersonal influence, as for ex- ample, a change in current strength, pressure, temperature, or mechan- ical configuration. (See"Nonautomatic.") Block(City,Town,or Village): See Section 800-2. ARTICLE 100—DEFINITIONS 70-5 Bonding Jumper: A reliable conductor to assure the required elec- trical conductivity between metal parts required to be electrically con- nected. Bonding Jumper,Circuit: The connection between portions of a con- ductor in a circuit to maintain required ampacity of the circuit. Bonding Jumper, Equipment: The connection between two or more portions of the equipment grounding conductor. Bonding Jumper, Main: The connection between the grounded cir- cuit conductor and the equipment grounding conductor at the service. *Branch Circuit: A branch circuit is that portion of a wiring system extending beyond the final overcurrent device protecting the circuit. A device not approved for branch circuit protection such as a thermal cutout or motor overload protective device is not considered as the overcur- rent device protecting the circuit. * Branch Circuit—Appliance: An appliance branch circuit is a cir- cuit supplying energy to one or more outlets to which appliances are to be connected; such circuits to have no permanently connected light- ing fixtures not a part of an appliance. Branch Circuit — General Purpose: A branch circuit that supplies a number of outlets for lighting and appliances. Branch Circuit — Individual: A branch circuit that supplies only one utilization equipment. Branch Circuit, Multiwire: A multiwire branch circuit is a circuit consisting of two or more ungrounded conductors having a potential difference between them, and an identified grounded conductor having equal potential difference between it and each ungrounded conductor of the circuit and which is connected to the neutral conductor of the system. Building: A structure which stands alone or which is cut off from adjoining structures by fire walls with all openings therein protected by approved fire doors. *Cabinet: An enclosure designed either for surface or flush mount- ing, and provided with a frame, mat or trim in which swinging doors are hung. Cell(As Applied to Raceways): See Sections 356-1 and 358-1. Circuit Breaker: A device designed to open and close a circuit by nonautomatic means, and to open the circuit automatically on a pre- determined overload of current, without injury to itself when properly applied within its rating. Communication Circuit: See Section 800-1. *Concealed: Rendered inaccessible by the structure or finish of the building. Wires in concealed raceways are considered concealed, even though they may become accessible by withdrawing them. Conductor: BARE: A bare conductor is one having no covering or insulation whatsoever. (See"Conductor,Covered.") 70-6 NATIONAL ELECTRICAL CODE COVERED: A covered conductor is one having one or more layers of nonconducting materials that are not recognized as insulation under the Code. (See"Conductor,Bare.") INSULATED: An insulated conductor is one covered with material recognized as insulation. *Connector, Pressure (Solderless): A pressure wire connector is a device which establishes the connection between two or more conduc- tors or between one or more conductors and a terminal by means of mechanical pressure and without the use of solder. Continuous Load: A load where the maximum current is expected to continue for three hours or more. Control Circuit: See Section 430-71. Controller: A device, or group of devices, which serves to govern, in some predetermined manner, the electric power delivered to the ap- paratus to which it is connected.See also Section 430-81(a). Cooking Unit, Counter-Mounted: An assembly of one or more do- mestic surface heating elements for cooking purposes designed for flush mounting in, or supported by, a counter, and which assembly is com- plete with inherent or separately mountable controls and internal wiring. (See"Oven,Wall-Mounted.") Current Limiting Overcurrent Protective Device: (See Section 240-27.) *Cutout Box: An enclosure designed for surface mounting and having swinging doors or covers secured directly to and telescoping with the walls of the box proper. (See"Cabinet.") *Demand Factor: The demand factor of any system, or part of a system, is the ratio of the maximum demand of the system, or part of a system, to the total connected load of the system, or of the part of the system under consideration. Device: A unit of an electrical system which is intended to carry but not utilize electric energy. Disconnecting Means: A device, or group of devices, or other means whereby the conductors of a circuit can be disconnected from their source of supply. Dry: (See"Location—Dry.") Dust-Ignition-Proof: See Section 502-1. *Dustproof: So constructed or protected that dust will not interfere with its successful operation. *Dust-tight: So constructed that dust will not enter the enclosing case. Duty: *CONTINUOUS: Continuous duty is a requirement of service that demands operation at a substantially constant load for an indefinitely long time. *INTERMITTENT: Intermittent duty is a requirement of service that demands operation for alternate intervals of (1) load and no load; or (2) load and rest;or (3) load,no load and rest. ARTICLE 100—DEFINITIONS 70-7 *PERIODIC: Periodic duty is a type of intermittent duty in which the load conditions are regularly recurrent. *SHORT TIME: Short time duty is a requirement of service that demands operation at a substantially constant load for a short and definitely specified time. *VARYING: Varying duty is a requirement of service that de- mands operations at loads, and for intervals of time,both of which may be subject to wide variation. See Table 430-22 (a—Exception) for illustrations of various types of duty. Duty Cycle(Welding): See Section 630-31(c). *Electric Sign: A fixed, stationary or portable, self-contained, elec- trically illuminated utilization equipment with words or symbols de- signed to convey information or attract attention. *Enclosed: Surrounded by a case which will prevent a person from accidentally contacting live parts. Equipment: A general term including material, fittings, devices, appliances, fixtures, apparatus and the like used as a part of, or in con- nection with,an electrical installation. * Explosion-proof Apparatus: Apparatus enclosed in a case which is capable of withstanding an explosion of a specified gas or vapor which may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and which operates at such an external tempera- ture that a surrounding flammable atmosphere will not be ignited thereby. Exposed: (As applied to live parts.) Exposed means that a live part can be inadvertently touched or approached nearer than a safe dis- tance by a person. It is applied to parts not suitably guarded, isolated or insulated. (See"Accessible"and"Concealed.") *Exposed: (As applied to wiring method.) Exposed means not con- cealed. *Externally Operable: Externally operable means capable of being operated without exposing the operator to contact with live parts. This term is applied to equipment, such as a switch, that is enclosed in a case or cabinet. Feeder: A feeder is the circuit conductors between the service equipment, or the generator switchboard of an isolated plant, and the branch circuit overcurrent device. Festoon Lighting: See Section 730-6. Fitting: An accessory such as a locknut, bushing or other part of a wiring system which is intended primarily to perform a mechanical rather than an electrical function. Garage: A building or portion of a building in which one or more self-propelled vehicles carrying volatile, flammable liquid for fuel or power are kept for use, sale, storage, rental, repair, exhibition or dem- onstrating purposes, and all that portion of a building which is on or 70-8 NATIONAL ELECTRICAL CODE below the floor or floors in which such vehicles are kept and which is not separated therefrom by suitable cutoffs. Ground: A ground is a conducting connection, whether intentional or accidental, between an electrical circuit or equipment and earth, or to some conducting body which serves in place of the earth. Grounded: Grounded means connected to earth or to some con- ducting body which serves in place of the earth. Grounded (Effectively Grounded Communication System): See Sec- tion 800-2(d). Grounded Conductor: A system or circuit conductor which is in- tentionally grounded. Grounding Conductor: A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes. Grounding Conductor, Main: (Ungrounded system) the conductor connecting the equipment grounding conductor at the service to the grounding electrode. Grounding Conductor, Common Main: (Grounded system) the con- ductor that connects both the circuit grounded conductor and the equip- ment grounding conductor to the grounding electrode. The above definition does not apply to a conductor used as both the grounded and grounding conductor, as permitted in Section 250-52 for services and Section 250-60 for ranges and clothes dryers. Grounding Conductor, Equipment: A conductor used to connect the equipment being grounded to the service equipment enclosure. Guarded: Covered, shielded, fenced, enclosed or otherwise pro- tected, by means of suitable covers or casings, barriers, rails or screens, mats or platforms, to remove the liability of dangerous contact or ap- proach by persons or objects to a point of danger. Hazardous Locations: See Article 500. Header: See Section 356-1. Header Ducts: See Section 358-1. Hoistway: Any shaftway, hatchway, well hole, or other vertical opening or space in which an elevator or dumbwaiter is designed to op- erate. Identified: Identified, as used in this Code in reference to a con- ductor or its terminal, means that such conductor or terminal is to be recognized as grounded.See Article 200. *Isolated: Isolated means that an object is not readily accessible to persons unless special means for access are used. *Lighting Outlet: An outlet intended for the direct connection of a lampholder, a lighting fixture or a pendant cord terminating in a lamp- holder. ARTICLE 100—DEFINITIONS 70-9 Location: DAMP LOCATION: A location subject to a moderate degree of mois- ture, such as some basements, some barns, some cold storage ware- houses, and the like. DRY LOCATION: A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness,as in the case of a building under construction. WET LOCATION: A location subject to saturation with water or other liquids, such as locations exposed to weather, washrooms in ga- rages, and like locations. Installations underground or in concrete slabs or masonry in direct contact with the earth shall be considered as wet locations. Low-Energy Power Circuit: A circuit which is not a remote-control or signal circuit but which has the power supply limited in accordance with the requirements of Class 2 remote control circuits. See Article 725. Such circuits include electric door openers and circuits used in the opera- tion of coin operated phonographs. Multioutlet Assembly: A type of surface or flush raceway designed to hold conductors and attachment plug receptacles, assembled in the field or at the factory. *Nonautomatic: Nonautomatic means that the implied action re- quires personal intervention for its control. (See"Automatic.") As applied to an electric controller, nonautomatic control does not neces- sarily imply a manual controller, but only that personal intervention is necessary. *Outlet: A point on the wiring system at which current is taken to supply utilization equipment. *Outline Lighting: An arrangement of incandescent lamps or gas- eous tubes to outline and call attention to certain features such as the shape of a building or the decoration of a window. Oven, Wall-Mounted: A domestic oven for cooking,purposes de- signed for mounting in or on a wall or other surface. Panelboard: A single panel or group of panel units designed for as- sembly in the form of a single panel; including buses, and with or with- out switches and/or automatic overcurrent protective devices for the control of light, heat or power circuits of small individual as well as aggregate capacity; designed to be placed in a cabinet or cutout box placed in or against a wall or partition and accessible only from the front. (See"Switchboard.") Projector,Nonprofessional: See Section 540-30. Projector,Professional: See Section 540-10. Qualified Person: One familiar with the construction and operation of the apparatus and the hazards involved. Raceway: Any channel for holding wires, cables or busbars, which is designed expressly for,and used solely for,this purpose. 70-10 NATIONAL ELECTRICAL CODE Raceways may be of metal or insulating material and the term includes rigid metal conduit, rigid nonmetallic conduit, flexible metal conduit, elec- trical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, structural raceways, wire- ways and busways. *Raintight: So constructed or protected that exposure to a beating rain will not result in the entrance of water. *Readily Accessible: Capable of being reached quickly, for opera- tion, renewal, or inspections, without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders,chairs,etc. (See"Accessible.") Receptacle (Convenience Outlet): A receptacle is a contact device installed at an outlet for the connection of an attachment plug and flex- ible cord. *Receptacle Outlet: An outlet where one or more receptacles are installed. Remote-Control Circuit: Any electrical circuit which controls any other circuit through a relay or an equivalent device. Sealable Equipment: Equipment enclosed in a case or cabinet that is provided with means of sealing or locking so that live parts cannot be made accessible without opening the enclosure. The equipment may or may not be operable without opening the enclosure. Sealed(Hermetic Type)Motor Compressor: A mechanical compressor consisting of a compressor and a motor, both of which are enclosed in the same sealed housing, with no external shaft nor shaft seals, the motor operating in the refrigerant atmosphere. Service: The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the premises served. *Service Cable: The service cable is the service conductors made up in the form of a cable. Service Conductors: The supply conductors which extend from the street main,or from transformers to the service equipment of the prem- ises supplied. Service Drop: The overhead service conductors from the last pole or other aerial support to and including the splices, if any, connecting to the service entrance conductors at the building or other structure. Service-Entrance Conductors, Overhead System: The service conduc- tors between the terminals of the service equipment and a point usually outside the building, clear of building walls, where joined by tap or splice to the service drop. Service-Entrance Conductors, Underground System: The service con- ductors between the terminals of the service equipment and the point of connection to the service lateral. Where service equipment is located outside the building walls, there may be no service-entrance conductors, or they may be entirely outside the building. ARTICLE 100—DEFINITIONS 70-11 Service Equipment: The necessary equipment, usually consisting of circuit-breaker or switch and fuses, and their accessories, located near point of entrance of supply conductors to a building and intended to constitute the main control and means of cutoff for the supply to that building. Service Lateral: The underground service conductors between the street main, including any risers at a pole or other structure or from transformers, and the first point of connection to the service entrance conductors in a terminal box or meter or other enclosure with adequate space, inside or outside the building wall. Where there is no terminal box, or meter or other enclosure with adequate space, the point of con- nection shall be considered to be the point of entrance of the service conductors into the building. Service Raceway: The rigid metal conduit, electrical metallic tub- ing, or other raceway, that encloses the service entrance conductors. Setting: (Of Circuit-breaker.) The value of the current at which it is set to trip. Show-Window: A show-window is any window used or designed to be used for the display of goods or advertising material, whether it is fully or partly enclosed or entirely open at the rear, and whether or not it has a platform raised higher than the street floor level. Sign: See"Electric Sign." Signal Circuit: Any electrical circuit which supplies energy to an appliance which gives a recognizable signal. Such circuits include circuits for door bells, buzzers, code-calling systems, signal lights,and the like. Special Permission: The written consent of the authority enforcing this Code. Switches: *GENERAL USE SWITCH: A general use switch is a switch in- tended for use in general distribution and branch circuits. It is rated in amperes, and it is capable of interrupting its rated current at its rated voltage. GENERAL USE SNAP SWITCH: A form of general use switch so constructed that it can be installed in flush device boxes, or on outlet box covers, or otherwise used in conjunction with wiring systems recog- nized by this Code. AC GENERAL USE SNAP SWITCH: A form of general use snap switch suitable only for use on alternating current circuits for control- ling the following: (a) Resistive and inductive loads (including electric discharge lamps) not exceeding the ampere rating at the voltage involved. (b) Tungsten filament lamp loads not exceeding the ampere rating at 120 volts. (c) Motor loads not exceeding 80 per cent of the ampere rating of the switches at the rated voltage. 70-12 NATIONAL ELECTRICAL CODE All AC general use snap switches are marked "AC" in addition to their electrical rating. AC-DC GENERAL USE SNAP SWITCH: A form of general use snap switch suitable for use on either direct or alternating current circuits for controlling the following: (a) Resistive loads not exceeding the ampere rating at the voltage in- volved. (b) Inductive loads not exceeding one-half the ampere rating at the voltage involved, except that switches having a marked horsepower rating are suitable for controlling motors not exceeding the horsepower rating of the switch at the voltage involved. (c) Tungsten filament lamp loads not exceeding the ampere rating at 125 volts,when marked with the letter"T". AC-DC general use snap switches are not generally marked AC-DC, but are always marked with their electrical rating. *ISOLATING SWITCH: An isolating switch is a switch intended for isolating an electric circuit from the source of power. It has no inter- rupting rating, and it is intended to be operated only after the circuit has been opened by some other means. MOTOR CIRCUIT SWITCH: A switch, rated in horsepower, capable of interrupting the maximum operating overload current of a motor of the same horsepower rating as the switch at the rated voltage. Switchboard: A large single panel, frame, or assembly of panels, on which are mounted, on the face or back or both, switches, overcurrent and other protective devices, buses and usually instruments. Switch- boards are generally accessible from the rear as well as from the front and are not intended to be installed in cabinets. (See"Panelboard.") Thermal Cutout: An overcurrent protective device which contains a heater element in addition to and affecting a renewable fusible member which opens the circuit. It is not designed to interrupt short circuit cur- rents. Thermally Protected: (As applied to motors.) The words"Thermally Protected"appearing on the nameplate of a motor or motor-compressor indicate that the motor is provided with a thermal protector. Thermal Protector: (As applied to motors.) A thermal protector is a protective device for assembly as an integral part of a motor or motor-compressor and which, when properly applied, protects the mo- tor against dangerous overheating due to overload and failure to start. The thermal protector may consist of one or more sensing elements inte- gral with the motor or motor-compressor and an external control device. *Utilization Equipment: Utilization equipment is equipment which utilizes electric energy for mechanical, chemical, heating, lighting, or similar useful purposes. *Ventilated: Provided with a means to permit circulation of air sufficient to remove an excess of heat,fumes or vapors. Volatile Flammable Liquid: A flammable liquid having a flash point below 100°F.or whose temperature is above its flash point. ARTICLE 110—GENERAL 70-13 * Voltage (of a circuit): Voltage is the greatest root-mean-square (effective) difference of potential between any two conductors of the circuit concerned. On various systems such as 3-phase 4 wire,single phase 3 wire and 3 wire direct current,there may be various circuits of various voltages. Voltage to Ground: In grounded circuits the voltage between the given conductor and that point or conductor of the circuit which is grounded; in ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit. Watertight: So constructed that moisture will not enter the enclos- ing case. *Weatherproof: Weatherproof means so constructed or protected that exposure to the weather will not interfere with successful op- eration. Raintight or watertight equipment may fulfill the requirements for "weatherproof." However, weather conditions vary and consideration should be given to conditions resulting from snow, ice, dust, or temperature extremes. Welder, Electric: RATED PRIMARY CURRENT: Section 630-31(c). ACTUAL PRIMARY CURRENT: Section 630-31(c). Wet: (See"Location—Wet.") X-ray: LONG TIME RATING: Section 660-1. MOMENTARY RATING: Section 660-1. ARTICLE 110—GENERAL 110-1. Scope. This Article provides the general requirements for elec- trical installations. 110-2. Approval. The conductors and equipment required or permit- ted by this Code shall be acceptable only when approved. See defini- tion of"Approved"in Article 100. 110-3. Mandatory and Advisory Rules. Mandatory rules of this Code are characterized by the use of the word, "shall." Advisory rules are characterized by the use of the word, "should," or are stated as recom- mendations of that which is advised but not required. 110-4. Examination of Equipment. Materials, devices, fittings, ap- paratus and appliances designed for use under this Code shall be judged chiefly with reference to the following considerations which also determine the classification by types, size, voltages, current ca- pacities,and specific use. (a) Suitability for installation and use in conformity with the pro- visions of this Code. 70-14 NATIONAL ELECTRICAL CODE (b) Mechanical strength and durability, including, for parts de- signed to enclose and protect other equipment, the adequacy of the protection thus provided. (c) Electrical insulation. (d) Heating effects under normal conditions of use and also under abnormal conditions likely to arise in service. (e) Arcing effects. 110-5. Voltages. Throughout this Code the voltage considered shall be that at which the circuit operates, whether the current is supplied by a battery,generator,transformer,rectifier,or a thermopile. 110-6. Conductor Gages. Conductor sizes are given in American Wire Gage (AWG). 110-7. Conductors. Conductors normally used to carry current shall be of copper unless otherwise provided in this Code. Where the con- ductor material is not specified, the sizes given in this Code shall apply to copper conductors. Where other materials are used, the size shall be changed accordingly. For aluminum conductors,see Tables 310-14 and 310-15. 110-8. Wiring Methods. Only wiring methods recognized as suitable are included in this Code. The recognized methods of wiring may be installed in any type of building or occupancy except as otherwise pro- vided in this Code. 110-9. Interrupting Capacity. Devices intended to break current shall have an interrupting capacity sufficient for the voltage employed and for the current which must be interrupted. 110-10. Circuit Impedance and Other Characteristics. The overcur- rent protective devices, the total impedance and other characteristics of the circuit to be protected shall be so selected and coordinated as to permit the circuit protective devices used to clear a fault without the occurrence of extensive damage to the electrical components of the cir- cuit. This fault may be assumed to be between two or more of the cir- cuit conductors; or between any circuit conductor and the grounding conductor or enclosing metal raceway. 110-11. Deteriorating Agencies. Unless approved for the purpose, no conductors or equipment shall be located in damp or wet locations; where exposed to gases, fumes, vapors, liquids or other agents having a deteriorating effect on the conductors or equipment; nor where exposed to excessive temperatures. Control equipment, utilization equipment and busways approved for use in dry locations only, should be protected against permanent dam- age from weather during building construction. 110-12. Mechanical Execution of Work. Electrical equipment shall be installed in a neat and workmanlike manner. 110-13. Mounting of Equipment. Electrical equipment shall be firmly secured to the surface on which it is mounted. Wooden plugs driven into holes in masonry, concrete,plaster or similar materials shall not be depended on for security. ARTICLE 110—GENERAL 70-15 110-14. Connections to Terminals. Connection of conductors to terminal parts shall insure a thoroughly good connection without dam- aging the conductors and shall be made by means of pressure connec- tors (including set screw type), solder lugs or splices to flexible leads except that No. 8 or smaller solid conductors and No. 10 or smaller stranded conductors may be connected by means of clamps or screws with terminal plates having upturned lugs. Terminals for more than one conductor shall be of a type approved for the purpose. Because of different characteristics of copper and aluminum, devices such as pressure connectors and soldering lugs shall be suitable for the material of the conductor and shall be properly installed and used. Ma- terials such as solder, fluxes, inhibitors, and compounds, where em- ployed, shall be suitable for the use and shall be of a type which will not adversely affect the conductors,installation,or equipment. 110-15. Splices. Conductors shall be spliced or joined with splicing devices approved for the use or by brazing, welding or soldering with a fusible metal or alloy. Soldered splices shall first be so spliced or joined as to be mechanically and electrically secure without solder and then soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors. 110-16. Working Space about Electrical Equipment (600 Volts or Less). Sufficient access and working space shall be provided and maintained about all electrical equipment to permit ready and safe operation and maintenance of such equipment. (a) Working Clearances. Except as elsewhere required or permitted in this Code, the dimension of the working space in the direction of ac- cess to live parts, operating at not more than 600 volts,which are likely to require examination, adjustment, servicing or maintenance while alive, shall not be less than indicated in Table 110-16(a). Distances are to be measured from the live parts if such are exposed or from the enclosure front or opening when such are enclosed. Table 110-16(a). Working Clearances Voltage to Ground Minimum clear distance Condition: 1 2 3 0-150 21/2 ft. 21 ft. 3 ft. 151-690 21/2 31/2 4 Where the"Conditions"are as follows: 1. Exposed live part on one side and no live or grounded part on the other side of the working space or exposed live parts on both sides ef- fectively guarded by suitable wood or other insulating materials. In- sulated wire or insulated bus bars operating at not more than 300 volts shall not be considered live parts. 2. Exposed live parts on one side and grounded parts on the other side.Concrete,brick or tile walls shall be considered as grounded. 3. Exposed live parts on both sides of the work space (not guarded as provided in Condition 1) with the operator between. 70-16 NATIONAL ELECTRICAL CODE Exception No. 1. Working space is not required in back of assemblies such as dead-front switchboards or control centers when there are no renewable or adjustable parts such as fuses or switches on the back and when all connections are accessible from other locations than the back. Exception No. 2. Smaller spaces may be permitted by the authority having jurisdiction where it is judged that the particular arrangement of the installation will provide adequate accessibility. (b) Clear Spaces. Working space required by this Section shall not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or gen- eral open space,shall be suitably guarded. (c) Access and Entrance to Working Space. At least one entrance of sufficient area shall be provided to give access to the working space about electrical equipment. (d) Front Working Space. In all cases where there are live parts normally exposed on the front of switchboards or control centers, the working space in front of such boards or panels shall be not less than 3 feet. (e) Illumination. Adequate illumination shall be provided for all working spaces about switchboards and control centers. (f) Headroom. The minimum headroom of working spaces about switchboards or control centers where there are live parts exposed at any time,shall be 61/4 feet. For higher voltages,see Article 710. 110-17. Guarding of Live Parts. (Not more than 600 Volts) (a) Except as elsewhere required or permitted by this Code, live parts of electrical equipment operating at 50 volts or more shall be guarded against accidental contact by approved cabinets or other forms of approved enclosures,or any of the following means: (1) By location in a room, vault, or similar enclosure which is ac- cessible only to qualified persons. (2) By suitable permanent, substantial partitions or screens so ar- ranged that only qualified persons will have access to the space within reach of the live parts. Any openings in such partitions or screens shall be so sized and located that persons are not likely to come into acciden- tal contact with the live parts or to bring conducting objects into con- tact with them. (3) By a guard rail, provided the live parts operate at 600 volts or less and provided the location is such as to make contact with live parts unlikely. (4) By location on a suitable balcony, gallery, or platform so ele- vated and arranged as to exclude unqualified persons. (5) By elevation at least 8 feet above the floor or other working surface. (b) In locations where electrical equipment would be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage. ARTICLE 110—GENERAL 70-17 (c) Entrances to rooms and other guarded locations containing ex- posed live parts shall be marked with conspicuous warning signs forbid- ding unqualified persons to enter. For motors see Sections 430-132 and 430-133. For additional require- ments at voltages over 600 see Article 710. 110-18. Arcing Parts. Parts of electrical equipment which in ordinary operation produce arcs, sparks, flames or molten metal, shall be en- closed unless separated and isolated from all combustible material. For hazardous locations see Articles 500-517 inclusive. For motors see Section 430-14. 110-19. Light and Power from Railway Conductors. Circuits for light- ing and power shall not be connected to any system containing trolley wires with a ground return, except in electric railway cars, car houses, power houses, or passenger and freight stations operated in connection with electric railways. 110-20. Insulation Resistance. All wiring shall be so installed that when completed the system will be free from short-circuits and from grounds other than as provided in Article 250. 110-21. Marking. The manufacturer's name, trademark, or other de- scriptive marking by which the organization responsible for the product • may be identified, shall be placed on all electrical equipment. Other markings shall be provided giving voltage, current, wattage, or other ratings as are prescribed elsewhere in this Code. 110-22. Identification. Each disconnecting means required by this Code for motors and appliances, and each service, feeder or branch circuit at the point where it originates, shall be legibly marked to indi- cate its purpose unless located and arranged so the purpose is evident. The marking shall be of sufficient durability to withstand the environ- ment involved. 70-18 Chapter 2. Wiring Design and Protection ARTICLE 200—USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 200-1. Scope. This Article provides requirements for the use and identification of a grounded conductor in interior wiring systems. (See definitions of "grounded conductor" and "grounding conductor" in Article 100.) 200-2. General. All interior wiring systems shall have a grounded conductor which is continuously identified throughout the system ex- cept as follows: Exception No. 1. A grounded conductor is not required in certain circuits or systems as provided in Sections 200-5, 250-3, 250-5, 250-6, 250-7,250-8,503-13,and 517-6. Exception No. 2. Continuous identification throughout a length of a conductor between terminals is not required for certain conductors under Section 200-6(a and b). 200-3. Connection to Grounded System. No interior wiring shall be electrically connected to a supply system unless the latter contains, for any grounded conductor of the interior system, a corresponding con- ductor which is grounded. Electrically connected implies connection capable of carrying current as distinguished from connection through electromagnetic induction. 200-4. Circuits Derived from Auto-Transformers. Branch circuits as described in Article 210 shall not be supplied through auto-transform- ers (transformers in which a part of the winding is common to both primary and secondary circuits) unless the system supplied has an iden- tified grounded conductor which is solidly connected to a similar identi- fied grounded conductor of the system supplying the auto-transformer. 200-5. Unidentified Circuits. (a) Two-wire branch circuits and AC circuits of two or more con- ductors may be tapped from the ungrounded conductors of circuits having identified grounded neutrals. Switching devices in each tapped circuit shall have a pole in each ungrounded conductor. These poles shall manually switch together where the switching devices serve as the disconnecting means required by Sections 422-21 and 422-23. Exception:For Motor Controllers see Section 430-84,and for heating equipment see Section 424-21. (b) Polyphase circuits need not have one conductor grounded and identified, except as required by Section 250-5, but where one conduc- tor is grounded it shall be identified. (c) Other unidentified ungrounded systems or circuits may be used only by special permission. ARTICLE 200—GROUNDED CONDUCTORS 70-19 200-6. Means of Identification of Grounded Conductors. Identification for grounded conductors shall be as follows: (a) Insulated conductors of No. 6 or smaller, except conductors of Type MI cable, shall have an outer identification of white or natural gray color as specified in 310-2(g). The grounded conductors of Type MI cable shall be identified by distinctive marking at the terminals dur- ing the process of installation. (b) Insulated conductors larger than No. 6, shall have an outer iden- tification of white or natural gray color, or shall be identified by distinc- tive white marking at terminals during process of installation. (c) Where, on a 4-wire delta-connected secondary, the midpoint of one phase is grounded to supply lighting and similar loads, that phase conductor having the higher voltage to ground shall be indicated by tagging or other effective means at any point where a connection is to be made if the neutral conductor is present. 200-7. Identified Conductor in Grounded Circuits Only. Conductors having white or natural gray covering shall not be used other than as conductors for which identification is required by Section 200-2, ex- cept under the following conditions, and then only where they are, in other respects, suitable for use as ungrounded conductors in the cir- cuit: Exception No. 1. Identified conductors, rendered permanently un- identified by painting or other effective means at each outlet where the conductors are visible and accessible, may be used as unidentified con- ductors. Exception No. 2. Cable containing an identified conductor may be used for single-pole, three-way or four-way switch loops where the con- nections are so made that the unidentified conductor is the return con- ductor from the switch to the outlet. This exception makes it unnecessary to paint the terminal of the identi- fied conductor at the switch outlet. Exception No. 3. A flexible cord, for connecting a portable appli- ance, having one conductor identified as required by Section 400-13 may be used even though there is no grounded conductor in the circuit supplying the outlet to which it is connected. 200-8. Connections to Screw-Shells. An identified conductor, where run to a screw-shell lampholder,shall be connected to the screw-shell. 200-9. Means of Identification of Terminals. The identification of ter- minals to which a grounded conductor is to be connected shall be by means of a metallic plated coating substantially white in color, such as nickel or zinc, or the terminals may be of material substantially white in color. The other terminals shall be of a readily distinguishable dif- ferent color. 200-10. Identification of Terminals. (a) Device Terminals. All devices provided with terminals for the attachment of conductors and intended for connection to more than one side of the circuit shall have terminals properly marked for identi- fication except as follows: 70-20 NATIONAL ELECTRICAL CODE Exception No. 1. Marking may be omitted where the electrical con- nection of a terminal intended to be connected to the grounded con- ductor is clearly evident. Exception No. 2. Single-pole Devices. Devices to the terminals of which only one side of the line is connected need not have terminals marked for identification. Exception No. 3. Panelboards and Devices. The terminals of lighting panelboards and of devices having a normal current rating of over 30 amperes need not be marked for identification, except as required in Section 200-10(b) for polarized receptacles for attachment plugs and polarized attachment plugs. (b) Plugs, Receptacles, and Connectors. Polarized attachment plugs, receptacles and cord connectors for plugs and polarized plugs shall have the terminal intended for connection to the grounded (white) conductor identified by a metal or metal coating substantially white in color. If the terminal for the grounded conductor is not visible, the con- ductor entrance hole for the connection shall be marked with the word "white." The terminal for the connection of the equipment grounding con- ductor shall be identified by: (1) A green colored, not readily remov- able terminal screw with hexagonal head; or (2) A green colored, hexagonal, not readily removable terminal nut; or (3) A green colored pressure wire connector. If the terminal for the grounding conductor is not visible, the conductor entrance hole shall be marked with the word "green"or otherwise identified by a distinctive green color. Exception: Two-wire attachment plugs, unless of the polarity type, need not have their terminals marked for identification. (c) Screw-Shells. In the case of devices with screw-shells, the identi- fied terminal shall be the one connected to the screw-shell. This does not apply to screw-shells which serve as fuseholders. (d) Screw-Shell Devices with Leads. In the case of screw-shell de- vices with attached leads, the conductor attached to the screw-shell shall have white or natural gray finish. The outer finish of the other conductor shall be of a solid color that will not be confused with the white or natural-gray finish which is to identify the grounded conduc- tor. (e) Fixed Appliances. The terminals of fixed appliances need not be marked to indicate the proper connection to the grounded conduc- tor unless a single-pole switch forms an integral part, then the terminal connected to the switch shall be the unidentified terminal. (f) Portable Appliances. The terminals of portable appliances need not be marked for identification. ARTICLE 210—BRANCH CIRCUITS 210-1. Scope. The provisions of this Article shall apply to branch circuits supplying lighting or appliance loads or combinations of such loads. Where motors, or motor-operated appliances, are connected to any circuit supplying lighting or other appliance loads, the provisions of both this Article and Article 430 shall apply.Article 430 shall apply where branch circuit supplies only motor loads. ARTICLE 210—BRANCH CIRCUITS 70-21 210-2. Specific Purpose Branch Circuit. The provisions applying to branch circuits referred to in the following list are exceptions to the provisions of this Article or are supplementary thereto, and shall apply to branch circuits supplying the loads referred to therein: Boat Harbor Wiring Section 555-2 Busways Section 364-8 Cranes and Hoists Section 610-42 Data Processing Systems Section 645-2 Elevators, Dumbwaiters and Escalators Section 620-61 Fixed Electric Space Heating Equipment Section 424-3 Infrared Industrial Heating Equipment . . . Sections 422-15, 424-3 Inductive and Dielectric Heat Generating Equipment Article 665 Instruments Section 384-22 Moticn Picture Studios and Similar Locations Article 530 Motors and Motor Controllers Article 430 Organs Section 650-6 Remote-Control,Low-Energy Power,Low- Voltage Power and Signal Circuits Article 725 Signs and Outline Lighting Section 600-6 Sound Recording and Reproduction Section 640-6 Systems over 600 Volts Article 710 Systems under 50 Volts Article 720 Theaters and Assembly Halls Sections 520-41, 520-52, and 520-62 Welders Article 630 X-ray Equipment Section 660-3 210-3. Classifications. Branch circuits recognized by this Article shall be classified in accordance with the maximum permitted rating or set- ting of the overcurrent device, and the classification for other than in- dividual branch circuits shall be 15, 20, 30, 40 and 50 amperes. When conductors of higher capacity are used for any reason, the rating or setting of the specified overcurrent device shall determine the circuit classification. A. General Provisions 210-4. Multiwire Branch Circuits. Branch circuits recognized by this Article may be installed as multiwire circuits. See Article 100 for Definition. 210-5. Color Code. Where installed in raceways, as aluminum sheathed cable, as open work, or as concealed knob-and-tube work, the conductors of multiwire branch circuits and two-wire branch circuits connected to the same system shall conform to the following color code. Three-wire circuits — one black, one white, one red; four-wire circuits—one black, one white, one red, one blue; five-wire circuits— one black, one white, one red, one blue, one yellow. Where more than one multiwire branch circuit is carried through a single raceway the ungrounded conductors of the additional circuit may be of colors other than those specified. All circuit conductors of the same color shall be connected to the same ungrounded feeder conductor throughout the installation. 70-22 NATIONAL ELECTRICAL CODE Any conductor intended solely for grounding purposes shall be iden- tified by a continuous green color or a continuous green color with one or more yellow stripes unless it be bare. Branch circuit conductors and equipment lead wires to which branch circuit conductors attach having a continuous green color or a continuous green color with one or more yellow stripes shall not be used for other than grounding purposes. The above is not intended to prohibit the use of a conductor having a con- tinuous green color or a continuous green color with one or more yellow stripes as insulation for internal wiring of equipment, except where such wiring serves as the lead wires to which the branch circuit conductors attach. See Section 200-7 for use of white or natural gray for grounded or neutral conductors. 210-6. Voltage. (a) Voltage to Ground. The voltage to ground on branch circuits supplying lampholders,fixtures,or standard receptacles of 15-ampere or less rating shall not exceed 150 volts,except as follows: Exception No. 1. In industrial establishments or in stores where the conditions of maintenance and supervision assure that only competent individuals will service the lighting fixtures the voltage of branch cir- cuits which supply only lighting fixtures that are equipped with mogul- base screw-shell lampholders or with lampholders of other types ap- proved for the application, mounted not less than eight feet from the floor, which do not have switch control as an integral part of the fixture shall not exceed 300 volts to ground; Exception No. 2. In industrial establishments, office buildings, schools, stores, and public and commercial areas of other buildings, such as hotels or transportation terminals, the voltage of branch cir- cuits which supply only the ballasts for electric discharge lamps mounted in permanently installed fixtures, by other than screw-shell type lampholders, which do not have manual switch control as an in- tegral part of the fixture shall not exceed 300 volts to ground. Where screw-shell type lampholders are used for electric discharge lamps the fixtures shall be installed not less than eight feet from the floor. Exception No. 3. For infrared industrial heating appliances as de- scribed in Section 422-15; Exception No.4.In railway properties as described in Section 110-19; Exception No. 5. The branch circuits supplying the ballasts for electric discharge lamps mounted in permanently installed fixtures on poles for the illumination of areas such as highways, bridges, athletic fields, parking lots, at a height not less than 22 feet, or on other struc- tures such as tunnels at a height not less than 18 feet, shall not exceed 500 volts between conductors when installed as provided in Section 730-7(a). (b) Voltage Between Conductors — Dwellings. In dwelling occupan- cies, the voltage between conductors supplying lampholders of the screw-shell type, receptacles, or appliances, shall not exceed 150 volts, except as follows: Exception: The voltage between conductors may exceed 150 volts when supplying only: ARTICLE 210—BRANCH CIRCUITS 70-23 (1) Permanently connected appliances, (2) Portable appliances of more than 1,380 watts, (3) Portable motor-operated appliances of 1/ horsepower or greater rating. (c) Voltage Drop. The size of the conductors for branch circuits as defined in Article 100 should be such that the voltage drop would not exceed 3 per cent to the farthest outlet for power, heating, lighting, or combinations thereof. Providing further that the maximum total volt- age drop for feeders and branch circuits should not exceed 5 per cent over all. 210-7. Grounding Receptacles. Receptacles and cord connectors equipped with grounding contacts shall have those contacts effectively grounded. The branch circuit or branch circuit raceway shall include or provide a grounding conductor to which the grounding contacts of the receptacle or cord connector shall be connected. The armor of type AC metal-clad cable, the sheath of MI and ALS cables, or a metallic raceway is acceptable as a grounding conductor. See Sections 210- 21(b), 250-45, 250-57(a), 250-59 and 350-5. Exception: For extensions only in existing installations which do not have a grounding conductor in the branch circuit, the grounding con- ductor of a grounding type receptacle outlet may be grounded to a grounded cold water pipe near the equipment. 210-8. Heavy-Duty Lampholders. Heavy-duty lampholders referred to in this Article shall include lampholders rated at not less than 750 watts. Exception: Admediuln lampholders rated at 660 watts shall be considered to be heavy duty type. B. Specific Requirements 210-19. Conductors. Circuit conductors shall conform to the follow- ing: (a) Ampacity. Shall have an ampacity of not less than the rating of the branch circuit and not less than the maximum load to be served. (b) Minimum Size. Shall not be smaller than No. 8 for ranges of 83/4 kw or more rating,nor smaller than No. 14 for other loads. (c) Exceptions: Exception No. 1. Range Loads. See Note 5 of Table 220-5. Where the maximum demand of a range of 83/4 kw or more rating is computed according to Column A of Table 220-5, the neutral conductor of a three-wire branch circuit supplying a household electric range, a wall- mounted oven or a counter-mounted cooking unit may be smaller than the ungrounded conductors but shall have an ampacity at least 70 per cent of the ampacity of the ungrounded conductors and shall not be smaller than No.10. Cable assemblies with the neutral conductor smaller than the un- grounded conductors shall be so marked. Exception No. 2. Tap Conductors. Tap conductors may be of less capacity than the branch circuit rating provided no tap conductor is of 70-24 NATIONAL ELECTRICAL CODE less capacity than the load to be served and provided the rating is not less than 20 amperes for 40 or 50 ampere circuits or 15 amperes for circuits rated less than 40 amperes and only when these tap conductors supply either: (a) Individual lampholders or fixtures with taps extending not longer than 18 inches beyond any portion of the lampholder or fixture, except as required in Section 410-65 (b-2);or, (b) Individual outlets with taps not over 18 inches long;or, (c) Infra-red lamp industrial heating appliances. (d) Nonheating leads of snow and ice melting cables and mats. Exception No. 3. Fixture Wires and Cords. Fixture wires and cords may be of smaller size, but not less than the size specified in Exception No.3 of Section 240-5(a). See Tables 400-9(b) and 402-4. Exception No. 4. Outlet Devices. Outlet devices may have less carry- ing capacity than the branch circuit rating, but not less than the types and ratings specified in Sections 210-21(a-c). Exception No. 5. Where tap conductors supply electric ranges, wall- mounted electric ovens and counter-mounted electric cooking units from 50 ampere branch circuits they shall be of suitable capacity for the load to be served, not less than 20 amperes in rating and no longer than necessary for servicing the appliance. 210-20. Overcurrent Protection. The rating or setting of overcurrent devices shall conform to the following: (a) Rating. Shall not be in excess of the value specified in Section 240-5. Exception: Tap Conductors and Fixture Wires. Tap conductors, fix- ture wire and cords as permitted in Section 210-19(c) may be consid- ered as protected by the circuit overcurrent device. (b) Single Appliance. Shall not exceed 150 per cent of the rating of the appliance, where the circuit supplies only a single appliance of 10-ampere or more rating. (c) Continuous Loads. Where loads other than motor loads will con- stitute continuous loads see Sections 210-23(b),220-2 and 240-2. 210-21. Outlet Devices. Outlet devices shall have a rating not less than the load to be served and shall conform to the following: (a) Lampholders. Lampholders when connected to circuits having a rating of over 20 amperes shall be of the heavy-duty type. (b) Receptacles. Receptacles installed on 15 ampere and 20 am- pere branch-circuits shall be of the grounding type and they shall be installed in accordance with Section 210-7. Grounding type receptacles which are of a type that rejects non-grounding type attachment plugs or which are of the locking type may be used for specific purposes or in special locations. A single receptacle installed on an individual branch circuit shall have a rating of not less than the rating of the branch circuit. ARTICLE 210—BRANCH CIRCUITS 70-25 When grounding type receptacles are used as replacements for existing non-grounding types a grounding conductor installed in accord- ance with Section 250-57 shall be provided. If it is impractical to reach a source of ground a non-grounding type receptacle shall be used. The installation of grounding type outlets shall not be used as a requirement that all portable equipment be of the grounded type. See Article 250 for requirements for the grounding of portables. Receptacles required in Section 517-3(d) are considered as meeting the requirements of this Section. When connected to circuits having two or more outlets, receptacles shall conform to the following: 15-amp.circuits Not over 15-amp. rating 20-amp.circuits 15 or 20-amp.rating 30-amp.circuits 30-amp.rating 40-amp.circuits 40 or 50 amp. rating 50-amp.circuits 50-amp.rating Receptacles connected to circuits having different voltages, frequen- cies or types of current (AC or DC) on the same premises shall be of such design that attachment plugs used on such circuits are not inter- changeable. Grounding type receptacles shall be installed only on circuits of the voltage class and current for which they have been approved. Receptacles rated at 15 amperes connected to 15 or 20 ampere branch circuits serving two or more outlets shall not supply a total load in excess of 12 amperes for portable appliances. Receptacles rated at 20 amperes connected to 20 ampere branch circuits serving two or more outlets shall not supply a total load in excess of 16 amperes for portable appliances. (c) Capacity of range receptacles may be based on single range loads as computed from Table 220-5. 210-22. Receptacle Outlets Required. Receptacle outlets shall be in- stalled as follows: (a) General. Where portable cords are used, except where the at- tachment of cords by other means is specifically permitted. A cord connector that is supported by a permanently connected cord pendant is considered a receptacle outlet. (b) Dwelling Type Occupancies. In every kitchen, family room, dining room, breakfast room, living room, parlor, library, den, sun room, recreation room and bedroom, receptacle outlets shall be in- stalled so that no point along the floor line in any wall space is more than six feet, measured horizontally, from an outlet in that space in- cluding any wall space two feet wide or greater and the wall space occupied by sliding panels in exterior walls. The receptacle outlets shall, insofar as practicable, be spaced equal distances apart. Receptacle out- lets in floor shall not be counted as part of the required number of receptacle outlets unless located close to the wall. At least one outlet shall be installed for the laundry. 70-26 NATIONAL ELECTRICAL CODE Outlets in other sections of the dwelling for special appliances such as laundry equipment, shall be placed within 6 feet of the intended lo- cation of the appliance. Exception No. 1. A dwelling unit that is an apartment or living area in a multi-family building where laundry facilities are provided on the premises that are available to all building occupants need not be pro- vided with a laundry receptacle. Exception No. 2. In other than single family dwellings where laundry facilities are not to be installed or permitted, a laundry receptacle need not be provided. Exception No. 3. A dwelling that is a unit in a hotel, motel, motor court, or motor hotel, need not be provided with a laundry receptacle. (c) Guest rooms in Hotels, Motels, and Similar Occupancies. These shall have receptacles installed in accordance with Section 210-22 (b). 210-23. Maximum Load. The maximum load shall conform to the following: (a) Appliances Consisting of Motors and Other Loads. Where a cir- cuit supplies only motor operated appliance loads, Article 430 shall ap- ply. For other than a portable appliance, the branch circuit size shall be calculated on the basis of 125 per cent of motor load where the motor is larger than 1/s hp plus the sum of the other loads. (b) Other Loads. The total load shall not exceed the branch circuit rating, and shall not exceed 80 per cent of the rating when load will constitute a continuous load such as store lighting and similar loads. In computing the load of lighting units which employ ballasts, transform- ers or auto-transformers, the load shall be based on the total of the ampere rating of such units and not on the wattage of the lamps. Exception No. 1. When the assembly including the overcurrent de- vice protecting the branch circuit is approved for continuous operation at 100 per cent of its rating, the total load may equal the branch circuit rating. Exception No. 2. Where branch circuits are derated in accordance with Note 8 of Tables 310-12 through 310-15 the derating factor for continuous loading shall not apply. Exception No.3.Range Loads.See Note 5 of Table 220-5. 210-24. Permissible Loads. Individual branch circuits may supply any loads. Branch circuits having two or more outlets may supply only loads as follows: (a) 15- and 20-Ampere Branch Circuits. Lighting units and/or ap- pliances. The rating of any one portable appliance shall not exceed 80 per cent of the branch circuit rating. The total rating of fixed appli- ances shall not exceed 50 per cent of the branch circuit rating when lighting units or portable appliances are also supplied. Small appliance branch circuits shall supply only the loads stipulated in Section 220-3 (b). (b) 30-Ampere Branch Circuits. FixeJjghting units with heavy duty lampholders in other than dwelling occdancies; or appliances in any ARTICLE 215—FEEDERS 70-27 occupancy. The rating of any one portable appliance shall not exceed 24 amperes. (c) 40-Ampere Branch Circuits. Fixed lighting units with heavy duty lampholders in other than dwelling occupancies; or fixed cooking ap- pliances;or infra-red heating units. (d) 50-Ampere Branch Circuits. Fixed lighting units with heavy duty lampholders in other than dwelling occupancies; or fixed cooking appliances;or infra-red heating units. The term"fixed"as used in this Section recognizes cord connections where otherwise permitted. Fixed outdoor electric snow melting and deicing installations may be supplied by any of the branch circuits described herein provided the circuit supplies no other load. 210-25. Table of Requirements. The requirements for circuits having two or more outlets [other than the receptacle circuits of Section 220- 3(b)] as specifically provided for above are summarized in Table 210- 25. Table 210-25 Branch Circuit Requirements (Type FEP, FEPB, RUW, SA, T, TW, RH, RUH, RHW, RHH, THHN, THW,THWN,and XHHW conductors in raceway or cable.) CIRCUIT RATING 15 Amp. 20 Amp. 30 J'inp. 40 Amp. 50 Amp. CONDUCTORS: (Min.Size) Circuit Wires* 14 12 10 8 6 Taps 14 14 14 12 12 Fixture Wires and Cords Refer to Section 240-5(a), Exception No. 3 OVERCURRENT PROTECTION 15 Amp. 20 Amp. 30 Amp. 40 Amp. 50 Amp. OUTLET DEVICES: Lampholders Any Any Heavy Heavy Heavy Permitted Type Type Duty Duty Duty Receptacle 15 Max. 15 or 20• 30 40 or 50 50 Rating Amp. Amp. Amp. Amp. Amp. MAXIMUM LOAD 15 Amp. 20 Amp. 30 Amp. 40 Amp. 50 Amp. PERMISSIBLE Refer to Refer to Refer to Refer to Refer to LOAD Section Section Section Section Section 210-24(a) 210-24(a) 210-24(b) 210-24(c) 210-24(d) *These ampacities are for copper conductors where derating is not re- quired.See Tables 310-12 through 310-15. ARTICLE 215—FEEDERS 215-1. Scope. This Article deals with installation requirements for, and, the size of conductors in the feeders needed to supply power to branch circuits and,the loads as calculated under Article 220. 215-2. Conductor Size. Feeder conductors shall have a current rating not smaller than the feeder load as determined by Section 220-4. A 2- 70-28 NATIONAL ELECTRICAL CODE wire feeder supplying two or more 2-wire branch circuits, or a 3-wire feeder supplying more than two 2-wire branch circuits, or two or more 3-wire branch circuits, shall be not smaller than Np. 10. Where a feeder carries the total current supplied by the service-entrance con- ductors, such feeder, for services of No. 6 and smaller, shall be of the same size as the service-entrance conductors. Where at any time it is found that feeder conductors are, or will be, overloaded, the feeder conductors shall be increased in capacity to ac- commodate the actual load served. See Examples Nos. 1 to 7 of Chapter 9. 215-3. Voltage Drop. The size of the conductors for feeders should be such that the voltage drop for the load as computed by Section 220-4 would not be more than 3% for power, heating or lighting loads or combinations thereof. Providing further that the maximum total volt- age drop for conductors for feeders and branch circuits should not ex- ceed 5% over all. 215-4. Overcurrent Protection. Feeders shall be protected against overcurrent in accordance with the provisions of Article 240. 215-5. Common Neutral Feeder. A common neutral feeder may be employed for two or three sets of 3-wire feeders, or two sets of 4-wire or 5-wire feeders. When in metal enclosures, all conductors of feeder circuits employing a co;mrpon neutral feeder shall be contained within the same enclosure as provided in Section 300-20. 215-6. Diagram of Feeders. If required by the authority having juris- diction, a diagram showing feeder details shall be supplied previous to installation. This diagram should show: Area in square feet; load (before applying demand-factors); demand-factors selected; computed load (after applying demand-factors);and the size of conductors. 215-7. Installation Requirements. Where a feeder supplies branch cir- cuits in which grounding conductors are required, the feeder shall in- clude or provide a grounding means to which the grounding conductor of the branch circuit shall be connected. ARTICLE 220—BRANCH CIRCUIT AND FEEDER CALCULATIONS 220-1. Scope. This Article provides the basis for calculating the ex- pected branch circuit and feeder loads and for determining the number of branch circuits required. 220-2. Calculation of Branch Circuit Loads. The load for branch circuits shall be computed in accordance with the provisions of this Section. Where in normal operation the maximum load will constitute a con- tinuous load, such as store lighting and similar loads, the minimum unit loads specified in this Section shall be increased by 25 per cent. Exception No. 1. Where branch circuits are derated in accordance with Note 8 of Tables 310-12 through 310-15 the unit loads are not re- quired to be increased by 25 per cent. ARTICLE 220—BRANCH CIRCUIT AND FEEDER CALCULATIONS 70-29 Exception No. 2. When the assembly including the overcurrent de- vices protecting the branch circuits and feeders are approved for opera- tion at 100 per cent of their rating the minimum unit loads need not be increased over those specified. (a) General Lighting Load. (1) In Listed Occupancies. In the occupancies listed in Table 220- 2(a), a load of not less than the unit load specified shall be included for each square foot of floor area. In determining the load on the "watts per square foot" basis, the floor area shall be computed from the outside dimensions of the building, apartment or area involved, and the number of floors; not including open porches, garages in connection with dwelling occupancies, nor unfinished spaces and unused spaces in dwellings unless adaptable for future use. The unit values herein are based on minimum load conditions and 100 per cent power factor, and may not provide sufficient capacity for the in- stallation contemplated. In view of the trend toward higher intensity lighting systems and increased loads due to more general use of fixed and portable appliances, each instal- lation should be considered as to the load likely to be imposed and the capacity increased to insure safe operation. Where electric discharge lighting systems are to be installed, high power- factor type should be used or the conductor capacity may need to be in- creased. (2) In Other Occupancies. In other occupancies, a load of not less than the unit load specified in Section 220-2(b) shall be included for each outlet. (b) Other Loads. For lighting other than general illumination and for appliances other than motors, a load of not less than the unit load specified below shall be included for each outlet. *Outlets supplying specific appliances and other loads Amp. rating of appliance Outlets supplying heavy-duty lampholders 5 amperes $Other outlets 1 i amperes *For motors,see Sections 430-22 and 430-24. $This provision shall not be applicable to receptacle outlets con- nected to the circuit specified in Section 220-3(b) nor to receptacle out- lets provided for the connection of stationary equipment as provided for in Section 400-3. (c) Exceptions. The minimum load for outlets specified in Section 220-2(b) shall be modified as follows: Exception No. 1. Ranges. For household electric ranges, the branch circuit load may be computed in accordance with Table 220-5. Exception No. 2. Show-Window Lighting. For show-window light- ing a load of not less than 200 watts for each linear foot of show-win- dow, measured horizontally along its base, may be allowed in lieu of the specified load per outlet. 70-30 NATIONAL ELECTRICAL CODE Exception No. 3. Multioutlet Assemblies. Where fixed multioutlet as- semblies are employed, each five feet or fraction thereof of each sep- arate and continuous length shall be considered as one outlet of not less than 1 1 ampere capacity; except in locations where a number of appliances are likely to be used simultaneously, when each one foot or fraction thereof shall be considered as an outlet of not less than 1' amperes. The requirements of this Section are not applicable to dwell- ings or the guest rooms of hotels. Table 220-2(a). General Lighting Loads by Occupancies Unit Load per Type of Occupancy Sq.Ft.(Watts) Armories and Auditoriums 1 Banks 2 Barber Shops and Beauty Parlors 3 Churches 1 Clubs 2 Court Rooms 2 `Dwellings (Other Than Hotels) 3 Garages—Commercial (storage) 1/a Hospitals 2 *Hotels and Motels,including apartment houses without provisions for cooking by tenants 2 Industrial Commercial (Loft) Buildings 2 Lodge Rooms 1' Office Buildings 5 Restaurants 2 Schools 3 Stores 3 Warehouses Storage t/a In any of the above occupancies except single- family dwellings and individual apartments of multifamily dwellings: Assembly Halls and Auditoriums 1 Halls,Corridors,Closets lh Storage Spaces �a *All receptacle outlets of 15-ampere or less rating in single-family and multifamily dwellings and in guest rooms of hotels and motels [except those connected to the receptacle circuits specified in Section 220-3(b)]may be con- sidered as outlets for general illumination,and no additional load need be in- cluded for such outlets. ARTICLE 220—BRANCH CIRCUIT AND FEEDER CALCULATIONS 70-31 Exception No. 4. Telephone Exchanges. Shall be waived for manual switchboards and switching frames in telephone exchanges. The provisions of Section 220-2(b) shall apply to all other receptacle outlets. (d) Existing Installations. Additions to existing installations shall conform to the following: (1) Dwelling Occupancies. New circuits or extensions to existing circuits may be determined in accordance with Sections 220-2(a or b); except that portions of existing structures Clot previously wired, or addi- tions to the building structure, either of which exceeds 500 square feet in area,shall be determined in accordance with Section 220-2(a). (2) Other Than Dwelling Occupancies. When adding new circuits or extensions to existing circuits in other than dwelling occupancies,the provisions of Section 220-2(a orb) shall apply. 220-3. Branch Circuits Required. Branch circuits shall be installed as follows: (a) Lighting and Appliance Circuits. For lighting, and for appli- ances, including motor-operated appliances, not specifically provided for in Section 220-3(b), branch circuits shall be provided for a com- puted load not less than that determined by Section 220-2. The number of circuits shall be not less than that determined from the total computed load and the capacity of circuits to be used. In every case the number shall be sufficient for the actual load to be served, and the branch circuit loads shall not exceed the maximum loads specified in Section 210-23. Where the load is computed on a "watts per square foot" basis, the total load, in so far as practical, shall be evenly proportioned among the branch circuits according to their capacity. When lighting units to be installed operate at other than 100 per cent power factor, see Section 210-23(b) for maximum ampere load permitted on branch circuits. For general illuminatio❑ in dwelling occupancies, it is recommended that not less than one branch circuit be installed for each 500 square feet of floor area in addition to the receptacle circuits called for in Section 220-3(b). See Examples No. 1, la, lb, lc,and 4,Chapter 9. (b) Small Appliance Branch Circuits, Dwellirg Occupancies. For the small appliance load in kitchen, pantry, family room, dining room, and breakfast room of dwelling occupancies, two or more 20-ampere ap— pliance branch circuits in addition to the branch circuits specified in Section 220-3(a) shall be provided for all receptacle outlets in these rooms,and such circuits shall have no other outlets. Receptacle outlets supplied by at least two appliance receptacle branch circuits shall be installed in the kitchen. At least one 20-ampere branch circuit shall be provided for laundry receptacle(s) required in Section 210-22(b). Receptacle outlets installed solely for the support of and the power supply for electric clocks may be installed on lighting branch circuits. A three-wire 115/230 volt branch circuit is the equivalent of two 115 volt receptacle branch circuits. 70-32 NATIONAL ELECTRICAL CODE (c) Other Circuits. For specific loads not otherwise provided for in Section 220-3(a or b), branch circuits shall be as required by other sections of the Code. 220-4. Calculation of Feeder Loads. The computed load of a feeder shall be not less than the sum of all branch circuit loads supplied by the feeder, as determined by Section 220-2, subject to the following provisions: (a) General Lighting. The demand factors listed in Table 220-4(a) may be applied to that portion of the total branch circuit load com- puted for general illumination. These demand factors shall not be ap- plied in determining the number of branch circuits for general illumina- tion supplied by the feeders. See Section 220-4(g and h). The demand factors herein are based on minimum load conditions and 100 per cent power factor, and in specific instances may not provide suffi- cient capacity for the installation contemplated. In view of the trend to- ward higher intensity lighting systems and increased loads due to more general use of fixed and portable appliances, each installation should be con- sidered as to the load likely to be imposed and the capacity increased to in- sure safe operation. Where electric discharge lighting systems are to be installed, high power-factor type should be used or the conductor capacity may need to be increased. Table 220-4(a). Calculation of Feeder Loads by Occupancies Type of Portion of Lighting Load Feeder Occupancy to which Demand Demand Factor Applies(wattage) Factor Dwellings—other First 3000 or less at 100% than Hotels Next 3001 to 120,000 at 35% Remainder over 120,000 at 25% *Hospitals First 50,000 or less at 40% Remainder over 50,000 at 20% *Hotels and Motels—includ- First 20,000 or less at 50% ing Apartment Houses Next 20,001 to 100,000 at 40% without provision for Remainder over 100,000 at 30% cooking by tenants Warehouses First 12,500 or less at 100% (Storage) Remainder over 12,500 at 50% All Others Total Wattage 100% * The demand factors of this Table shall not apply to the computed load of sub-feeders to areas in hospitals, hotels and motels where en- tire lighting is likely to be used at one time; as in operating rooms, ballrooms,or dining rooms. (b) Show-Window Lighting. For show-window lighting, a load of not less than 200 watts shall be included for each linear foot of show- window measured horizontally along its base. (c) Motors. For motors, a load computed according to the provi- sions of Sections 430-24,430-25 and 430-26 shall be included. ARTICLE 220—BRANCH CIRCUIT AND FEEDER CALCULATIONS 70-33 (d) Neutral Feeder Load. The neutral feeder load shall be the maximum unbalance of the load determined by Section 220-4. The maximum unbalanced load shall be the maximum connected load be- tween the neutral and any one ungrounded conductor; except that the load thus obtained shall be multiplied by 140 per cent for 5-wire, 2-phase systems. For a feeder supplying household electric ranges, wall- mounted ovens and counter-mounted cooking units, the maximum un- balanced load shall be considered as 70 per cent of the load on the un- grounded conductors, as determined in accordance with Table 220-5. For 3-wire DC or single-phase AC, 4-wire 3-phase and 5-wire 2-phase systems, a further demand-factor of 70 per cent may be applied to that portion of the unbalanced load in excess of 200 amperes. There shall be no reduction of the neutral capacity for that portion of the load which consists of electric discharge lighting. See Examples 1, la, lb, ic, 2, 3,4 and 5,Chapter 9. (e) Fixed Electrical Space Heating. The computed load of a feeder supplying fixed electrical space heating equipment shall be the total connected load on all branch circuits. Exception No. 1. Where reduced loading of the conductors results from units operating on duty-cycle, intermittently, or from all units not operating at one time, the authority enforcing this code may grant per- mission for feeder conductors to be of a capacity less than 100 per cent, provided the conductors are of sufficient capacity for the load so de- termined. Exception No. 2. Section 220-4(e) does not apply when feeder ca- pacity is calculated in accordance with optional method in Section 220-7 for one-family residences. (f) Noncoincident Load. In adding the branch circuit loads to de- termine the feeder load, the smaller of two dissimilar loads may be omitted from the total where it is unlikely that both of the loads will be served simultaneously. (g) Small Appliances. The computed branch circuit load for re- ceptacle outlets in other than dwelling occupancies, for which the al- lowance is not more than 11/2 amperes per outlet, may be included with the general lighting load and subject to the demand factors in Sec- tion 220-4(a). Dwelling Occupancies The requirements in following Sections 220-4 (h-k) apply to dwelling type occupancies and are supplemental to the preceding Sections 220-4(a-g). (h) 1. Small Appliances. In single-family dwellings, in individual apartments of multi-family dwellings having provisions for cooking by tenants, and in each hotel suite having a serving pantry, a feeder load of not less than 1500 watts for each two-wire circuit installed as required by Section 220-3(b) shall be included for small appliances (portable appliances supplied from receptacles of 15 or 20 ampere rating) in kitchen, pantry, family room, dining room, and breakfast room. Where the load is subdivided through two or more feeders, the computed load for each shall include not less than 1500 watts for each two-wire circuit 70-34 NATIONAL ELECTRICAL CODE for small appliances.These loads may be included with the general light- ing load and subject to the demand factors in Section 220-4(a). 2. Laundry Circuit. A feeder load of not less than 1500 watts shall be included for each 2-wire laundry circuit installed as required by Section 220-3(c). This load may be included with the general lighting load and subject to the demand factors in Section 220-4(a). (i) Electric Ranges. The feeder load for household electric ranges and other cooking appliances,individually rated more than 13/4 kw,may be calculated in accordance with Table 220-5. In order to provide for possible future installation of ranges of higher ratings, it is recommended that where ranges of less than 83/4 kw ratings or wall-mounted ovens and counter-mounted cooking units are to be installed, the feeder capacity be not less than the maximum demand value specified in Column A of Table 220-5. Where a number of single-phase ranges are supplied by a 3-phase, 4-wire feeder, the current shall be computed on the basis of the de- mand of twice the maximum number of ranges connected between any two-phase wires. See Example 7,Chapter 9. (j) Fixed Electrical Appliances (Other than Ranges, Clothes Dryers, Air Conditioning Equipment or Space Heating Equipment). Where four or more fixed electrical appliances other than electric ranges, clothes dryers, air conditioning equipment or space heating equipment are con- nected to the same feeder in a single or multifamily dwelling, a demand factor of 75 per cent may be applied to the fixed appliance load. (k) Space Heating and Air Cooling. In adding branch circuit loads for space heating and air cooling in dwelling occupancies, the smaller of the two loads may be omitted from the total where it is unlikely that both of the loads will be served simultaneously. (I) Farm Buildings. Feeders supplying farm buildings (excluding dwellings) or loads consisting of two or more branch circuits shall have minimum capacity computed in accordance with the following table: Table 220-4(I) Demand Computation for Farm Buildings or Loads Per Cent of Load in Amperes at 230 Volts Connected Load Loads expected to operate without diversity, but not less than 125% full load current of the largest motor and not less than first 60 amperes. 100% Next 60 Amperes of all other loads 50% Remainder of other load 25% Note 1: For services to farm dwellings,see Sections 220-2 through 220-7. Note 2: For service at main point of delivery to farmstead, see Section 220-4(m). ARTICLE 220—BRANCH CIRCUIT AND FEEDER CALCULATIONS 70-35 Table 220-5. Demand Loads for Household Electric Ranges, Wall-Mounted Ovens,Counter-Mounted Cooking Units and Other Household Cooking Appliances over 134 kw Rating Column A to be used in all cases except as otherwise permitted in Note 4 below. Maximum Demand Demand Factors NUMBER OF (See Notes) (See Note 4) APPLIANCES COLUMN A COLUMN B COLUMN C (Not over 12 (Less than 31/2 (3/ kw to 83/4 kw Rating) kw Rating) kw Rating) 1 8 kw 80% 80% 2 11 kw 75% 65% 3 14 kw 70% 55% 4 17 kw 66% 50% 5 20 kw 62% 45% 6 21 kw 59% 43% 7 22 kw 56% 40% 8 23 kw 53% 36% 9 24 kw 51% 35% 10 25 kw 49% 34% 11 26 kw 47% 32% 12 27 kw 45% 32% 13 28 kw 43% 32% 14 29 kw 41% 32% 15 30 kw 40% 32% 16 31 kw 39% 28% 17 32 kw 38% 28% 18 33 kw 37% 28% 19 34 kw 36% 28% 20 35 kw 35% 28% 21 36 kw 34% 26% 22 37 kw 33% 26% 23 38 kw 32% 26% 24 39 kw 31% 26% 25 40 kw 30% 26% 26-30 15 kw plus 1 kw 30% 24% 31-40 f for each range} 30% 22% 41-50 25 kw plus 3/ 30% 20% 51-60 { kw for each 30% 18% 61&over range 30% 16% Note 1. Over 12 kw to 27 kw ranges all of same rating. For ranges, individually rated more than 12 kw but not more than 27 kw, the maximum demand in Column A shall be increased 5 per cent for each additional kw of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kw. Note 2. Over 12 kw to 27 kw ranges of unequal ratings. For ranges individually rated more than 12 kw and of different ratings but none exceeding 27 kw an average value of rating shall be calculated by add- ing together the ratings of all ranges to obtain the total connected load (using 12 kw for any range rated less than 12 kw) and dividing by the total number of ranges; and then the maximum demand in Column A 70-36 NATIONAL ELECTRICAL CODE shall be increased 5 per cent for each kw or major fraction thereof by which this average value exceeds 12 kw. Note 3. This table does not apply to commercial ranges. See Table 220-6(a) for demand factors for commercial cooking equipment. Note 4. Over 13/4 kw to 83/4 kw. In lieu of the method provided in Column A,loads rated more than 13/4 kw but not more than 83/4 kw may be considered as the sum of the nameplate ratings of all the loads, multiplied by the demand factors specified in Columns B or C for the given number of loads. Note 5. Branch Circuit Load. Branch circuit load for one range may he computed in accordance with Table 220-5. The branch circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room shall be computed by adding the nameplate ratings of the indi- vidual appliances and treating this total as equivalent to one range. Table 220-6(a) Feeder Demand Factors for Commercial Electric Cooking Equipment; including Dishwasher Booster Heaters, Water Heaters, and Other Kitchen Equipment. Number of Units Demand Factors of Equipment (per cent) 1 100 2 100 3 90 4 80 5 70 6 & over 65 Table 220-6(b) Demand Factors for Household Electric Clothes Dryers Number of Demand Factor Dryers (per cent) 1 100 2 100 3 100 4 100 5 80 6 70 7 65 8 60 9 55 10 50 11-13 45 14-19 40 20-24 35 25-29 32.5 30-34 30 35-39 27.5 40 & over 25 ARTICLE 220—BRANCH CIRCUIT AND FEEDER CALCULATIONS 70-37 (m) Farm Services. (1) Service equipment and service entrance conductors for indi- vidual farm buildings (excluding dwellings) shall have minimum ca- pacity computed in accordance with Section 220-4(1). (2) Minimum capacity of service conductors and service equip- ment, if any, at the main point of delivery to farms (including dwell- ings) shall be determined in accordance with the following formula: 100 per cent of the largest demand computed in accordance with Section.220-4(1). 75 per cent of the second largest demand computed in accordance with Section 220-4(1). 65 per cent of the third largest demand computed in accordance with Section 220-4(1). 50 per cent of the demands of remaining loads computed in accord- ance with Section 220-4(1). Note 1: Consider as a single computed demand the total of the computed demands of all buildings or loads having the same function. Note 2: The demand of the farm dwelling, if included in the demands of this formula, should be computed in accordance with Note 1 of Ta- ble 220-4(1) 220-7. Optional Calculation for Single Family Dwelling or Individual Apartment of Multifamily Dwelling. For a single family dwelling or individual apartment of a multifamily dwelling served by a 115/230 volt, 3-wire, 100 ampere or larger service where the total load is sup- plied by one feeder or one set of service entrance conductors, the per- centages shown in Table 220-7 may be used in lieu of the method of determining feeder (and service) loads detailed in Section 220-4. All other load shall include 1500 watts for each 20 ampere appli- ance circuit [Section 220-3(b)]; lighting and portable appliances at 3 watts per square foot; all fixed appliances, (including four or more separately controlled space heating units [see Section 220-4(k)], ranges, wall-mounted ovens and counter-mounted cooking units) at nameplate rated load (kva for motors and other low power-factor loads). See Examples 1(b) and 1(c) of Chapter 9. Table 220-7 Optional Calculation for Single Family Dwelling or Individual Apartment of Multifamily Dwelling Per Cent LOAD(in kw or kva) of Load Air conditioning and cooling including heat pump compressors [see Section 220-4(k)] 100% Central electrical space heating [see Section 220-4(k)] 100% Less than four separately controlled electrical space heating units [see Section 220-4(k)] 100% First 10 kw of all other load 100% Remainder of other load 40% 70-38 NATIONAL ELECTRICAL CODE 220-8. Optional Calculation for Additional Loads in Existing One-Family Dwelling Occupancy. Load calculations for an existing one-family dwelling occupancy now served by an existing 115/230 volt or 120/208 volt, 3-wire, 60 ampere service may be computed as follows: Load in KW or KVA Per Cent of Load First 8 KW of load at 100% Remainder of load at 40% Load calculation shall include lighting and portable appliances at 3 watts per square foot; 1500 watts for each 20 ampere appliance circuit; range or wall-mounted oven and counter-mounted cooking unit, and other fixed or stationary appliances,at nameplate rating. If air conditioning equipment or electric space heating equipment is to be installed the following formula shall be applied to determine if the existing service is of sufficient size. Air conditioning equipment* 100% Central electrical space heating* 100% Less than four separately controlled space heating units* . 100% First 8 KW of all other load 100% Remainder of all other load 40% Other loads shall include: 1500 watts for each 20 ampere appliance circuit. Lighting and portable appliances at 3 watts per sq.ft. Household range or wall-mounted oven and counter-mounted cook- ing unit. All other fixed appliances including four or more separately con- trolled space heating units,at nameplate rating. *Use larger connected load of air conditioning and space heating, but not both. 220-9.Optional Calculation for Multifamily Dwellings. (a) For multifamily dwellings equipped with electric cooking equip- ment, and electric space heating or air conditioning or both, the re- quired demand load for each feeder and for the service entrance con- ductors may be determined by the following method in lieu of the method of determining feeder (and service) loads detailed in Section 220-4, provided that no individual dwelling unit is supplied by more than one feeder. Any house loads on such feeders shall be calculated in accordance with applicable Sections of Article 220 and shall be added to loads as determined by this Section. (b) The connected load to which the demand factor applies shall in- clude: (1) 1500 watts for each 2-wire 20 ampere appliance circuit re- quired by Section 220-3(b) and 1500 watts for each 2-wire 20 ampere laundry circuit installed in accordance with Section 220-3(b). (2) Lighting and portable appliances at 3 watts per square foot. (3) All fixed or stationary appliances including ranges, wall- mounted ovens, counter-mounted cooking units, and laundry dryers 1 ARTICLE 230—SERVICES 70-39 at nameplate rated load (kva for motors and other low power-factor loads). (4) Water heaters at nameplate rated load, using only the maxi- mum possible at one time in the case of a water heater with interlocked elements. (5) The larger load of all space heating units or all air conditioning units,per Section 220-4(k). Table 220-9 Demand Factors for Feeders and Service Entrance Conductors for Multifamily Dwelling Number of Demand Dwelling Factor Units (per cent) 3-5 45 6-7 44 8-10 43 11 42 12-13 41 14-15 40 16-17 39 18-20 38 2I 37 22-23 36 24-25 35 26-27 34 28-30 33 31 32 32-33 31 34-36 30 37-38 29 39-42 28 43-45 27 46-50 26 51-55 25 56-61 24 62&over 23 ARTICLE 230—SERVICES A. General Requirements 230-1. Scope. The provisions of this Article shall apply to the con- ductors and equipment for control and protection of services — cir- cuits that conduct electric power from the supply system or plant to the premises to be served. 230-2. Number of Services to a Building or Other Premises Served. In general, a building or other premises served shall be supplied through only one set of service conductors,except as follows: 70-40 NATIONAL ELECTRICAL CODE Exception No. 1. Fire Pumps. Where a separate service is required for fire pumps. Exception No. 2. Emergency Lighting. Where a separate service is required for emergency lighting and power purposes. Exception No.3.Multiple-Occupancy Buildings. (a) By special permission, in multiple-occupancy buildings where there is no available space for service equipment accessible to all the occupants. (b) Buildings of multiple occupancy may have two or more sep- arate sets of service-entrance conductors which are tapped from one service drop or lateral, or two or more sub-sets of service-entrance con- ductors may be tapped from a single set of main service-entrance con- ductors. DEFINITION: Sub-sets of service-entrance conductors are taps from main service conductors run to service equipment. Exception No. 4. Capacity Requirements. Where capacity require- ments make multiple services desirable. Exception No. 5. Buildings of Large Area. By special permission, where more than one service is necessary due to the area over which a single building extends. Exception No. 6. Different Characteristics or Classes of Use. Where additional services are required for different voltages, frequency, or phase, or different classes of use. Different classes of use could be be- cause of needs for different characteristics, or because of rate schedule as in the case of controlled water heater service. 230-3. Supply to a Building from Another. The service conductors supplying each building or structure shall not pass through the inside of another building unless these buildings are under single occupancy or management.See Section 230-45. B. Insulation and Size of Service Conductors 230-4. Insulation of Service Conductors. Service conductors shall normally withstand exposure to atmospheric and other conditions of use without detrimental leakage of current to adjacent conductors, objects, or the ground. For Service Drops—See Section 230-22. For Service Entrance Conductors—See Section 230-40. For Underground Services—See Section 230-30. 230-5. Size of Service Conductors. Service conductors shall have ade- quate ampacity to safely conduct the current for the loads supplied with- out a temperature rise detrimental to the insulation or covering of the conductors, and shall have adequate mechanical strength. Minimum sizes are given in the following references: For Service Drops—Section 230-23. For Service Entrance Conductors—Section 230-41. For Underground Service Conductors—Section 230-31. For Farmstead Service Conductors—See Section 220-4(m). ARTICLE 230—SERVICES 70-41 C. Service Drops 230-21. Number of Drops. No building shall be supplied through more than one service drop, except for the purposes listed in Section 230-2. 230-22. Service Drop Conductors. (a) In multiple conductor cables, conductors shall be insulated or covered with rubber or thermoplastic. Exception.A grounded conductor may be without insulation or cover- ing where the nominal voltage to ground of any conductor is not over 300 volts. (b) All open,individual conductors shall be insulated or covered. 230-23. Minimum Size of Service Drop Conductors. Conductors shall have sufficient ampacity to carry the load. They shall have adequate mechanical strength and shall not be smaller than No. 8 copper or No. 6 aluminum. Exception. For installations to supply only limited loads of a single branch circuit such as small polyphase power, controlled water heaters and the like, they shall not be smaller than No. 12 hard drawn copper or equivalent. Overhead conductors to a building or other structure from a pole on which a meter or disconnecting means is installed shall be considered as a service drop and installed accordingly. Conductors having extruded covering used for service drops have the same ampacities as covered conductors listed in Tables 310-13 and 310-15. 230-24. Clearance of Service Drops. Service drop conductors shall not be readily accessible and when not in excess of 600 volts, shall conform to the following: (a) Clearance Over Roof. Conductors shall have a clearance of not less than 8 ft. from the highest point of roofs over which they pass with the following exceptions: Exception No. 1. Where the voltage between conductors does not exceed 300 and the roof has a slope of not less than 4 inches in 12 inches the clearance may be not less than 3 feet. Exception No. 2. Service drop conductors of 300 volts or less which do not pass over other than a maximum of 4 feet of the overhang por- tion of the roof for the purpose of terminating at a (through-the-roof) service raceway or approved support may be maintained at a minimum of 18 inches from any portion of the roof over which they pass. (b) Clearance from Ground. Service drop conductors when not in excess of 600 volts, shall have the following minimum clearance from ground. 10 feet—above finished grade, sidewalks or from any platform or projection from which they might be reached; 12 feet—over residential driveways and commercial areas such as parking lots and drive-in establishments not subject to truck traffic; 70-42 NATIONAL ELECTRICAL CODE 15 feet—over commercial areas,parking lots,agricultural or other areas subject to truck traffic; 18 feet—over public streets, alleys, roads and driveways on other than residential property. (c) Clearance from Building Openings. Conductors shall have a clearance of not less than 36 inches from windows, doors, porches, fire escapes,or similar locations. Conductors run above the top level of a window are considered out of reach from that window. For clearances of conductors of over 600 volts see National Electrical Safety Code. (Available from Superintendent of Documents, Government Printing Office,Washington,D.C.20401.) 230-25. Supports Over Buildings. Where practicable, conductors pass- ing over a building shall be supported on structures which are inde- pendent of the building. Where necessary to attach conductors to roof they shall be supported on substantial structures. 230-26. Point of Attachment. The point of attachment of a service drop to a building or other structure shall be not less than 10 feet above finished grade and shall be at a height to permit the minimum clear- ance requirements of Section 230-24. In the event a mast type riser is required to attain the required height, it shall be of such construction and so supported that it will withstand the strain imposed by the service drop. Raceway fittings shall be of a type approved for the purpose. 230-27. Means of Attachment. Multiple-conductor cables used for service drops shall be attached to buildings or other structures by fittings approved for the purpose. Open conductors shall be attached to non- combustible, nonabsorptive insulators securely attached to the building or other structure or by fittings approved for the purpose. D. Underground Services 230-30. Insulation—Underground Service Conductors. (a) Underground conductors up to the point of connection to serv- ice equipment shall be insulated,except: Exception No. 1. Where the nominal voltage to ground of any con- ductor is not over 300 volts, a grounded conductor of copper or alu- minum without individual insulation or covering may be installed under- ground when part of an approved cable assembly. Exception No. 2. Where the nominal voltage to ground of any con- ductor is not over 300 volts, bare grounded conductors of copper may be installed underground in duct or conduit. (b) Insulated service conductors installed underground, or in concrete slabs or masonry in direct contact with earth, shall be lead-covered or of other types specially approved for the purpose. 230-31. Size of Underground Service Conductors. (a) Size of Underground Service Lateral. Conductors shall have suf- ficient ampacity to carry the load. They shall not be smaller than No. 8 copper or No. 6 aluminum. ARTICLE 230—SERVICES 70-43 Exception: For installations to supply only limited loads of a single branch circuit such as small polyphase power, controlled water heaters and the like, they shall not be smaller than No. 12 copper or No. 10 aluminum. (b) Size of Underground Service Entrance Conductors. Same as re- quired for overhead service entrance conductors.See Section 230-41. (c) Number of Service Laterals. No building or other structure shall be supplied through more than one service lateral, except for the pur- poses listed in Section 230-2. 230-32. Protection Against Damage. (a) In the Ground. Underground service conductors shall be pro- tected against physical damage by being installed: (1) in duct; (2) in rigid metal conduit or electrical metallic tubing made of a material suitable for the condition, or provided with corrosion protec- tion suitable for the condition; (3) in rigid nonmetallic conduit if installed in accordance with Sections 347-2 and 347-3; (4) in cable of one or more conductors approved for direct burial in the earth; (5) other approved means. (b) On Poles. Where underground service conductors are carried up a pole the mechanical protection shall be installed to a point at least 8 feet above the ground. Such mechanical protection may be provided by the use of approved cable,pipe,or other approved means. (c) Where Entering Building. Underground service conductors shall have mechanical protection in the form of rigid or flexible conduit, electrical metallic tubing, auxiliary gutters, the metal tape of an ap- proved service cable, or other approved means. The mechanical pro- tection shall extend to the enclosure for the service equipment unless the service switch is installed on a switchboard, in which case a bushing shall be provided which, except where lead-covered conductors are used,shall be of the insulating type. 230-33. Raceway Seal. Where a service raceway or duct enters from an underground distribution system, the end within the building shall be sealed with suitable compound so as to prevent the entrance of mois- ture or gases.Spare or unused ducts shall also be sealed. E. Service-Entrance Conductors 230-40. Insulation of Service-Entrance Conductors. (a) Service-entrance conductors entering buildings or other structures shall be insulated. Where only on the exterior of buildings or other structures the conductors shall be insulated or covered. Exception: Where the nominal voltage to ground of any conductor is not over 300 volts,a bare grounded conductor may be installed. (b) Open individual conductors which enter the building or other structure shall be rubber-covered or thermoplastic-covered. 70-44 NATIONAL ELECTRICAL CODE 230-41. Size of Service-Entrance Conductors, Overhead System and Un- derground System. Service-entrance conductors shall have sufficient ampacity to carry the load as determined by Article 220 and in accord- ance with Tables 310-12, 310-13, 310-14, 310-15. Service entrance con- ductors shall not be smaller than No. 6 except: Exception No. 1. For single family residences with an initial load of 10 KW or more computed in accordance with Article 220, or if the initial installation has more than five 2-wire branch circuits, the service- entrance conductors shall have an ampacity of not less than 100 am- peres 3-wire. It is recommended that a minimum of 100 ampere 3-wire service be pro- vided for all individual residences. Exception No. 2. For installations consisting of not more than two 2-wire branch circuits they shall not be smaller than No.8. Exception No. 3. By special permission due to limitations of supply source or load requirements they shall not be smaller than No.8. Exception No. 4. For installations to supply only limited loads of a single branch circuit, such as small polyphase power, controlled water heaters and the like, they shall not be smaller than the conductors of the branch circuit and in no case smaller than No. 12. Exception No. 5. The neutral conductor which shall have an am- pacity in conformity with Section 220-4(d), but shall not be smaller than the ungrounded conductors when these are No.8 or smaller. 230-42. Service-Entrance Conductors without Splice. Service-entrance conductors shall be without splice except as follows: Exception No. 1. Clamped or bolted connections in a meter en- closure are permitted. Exception No. 2. Taps to main service conductors are permitted as provided in Section 230-2 Exception No. 3(b) or to individual sets of service equipment as provided in Section 230-70(g). Exception No. 3. A connection is permitted, when properly enclosed, where an underground service conductor enters a building and is to be extended to the service equipment or meter in another form of ap- proved service raceway or service cable. Exception No. 4. A connection is permitted where service conduc- tors are extended from a service drop to an outside meter location and returned to connect to the service-entrance conductors of an existing installation. 230-43. Other Conductors in Service Raceway. Conductors other than service conductors, grounding conductors, or control conductors from time switches having overcurrent protection, shall not be installed in the same service raceway or service entrance cable. F. Installation of Service-Entrance Conductors 230-44. Wiring Methods. Service-entrance conductors extending along the exterior,or entering buildings or other structures may be installed as follows: ARTICLE 230—SERVICES 70-45 (a) As separate conductors, in cables approved for the purpose, or enclosed in rigid conduit; (b) For circuits not exceeding 600 volts the conductors may be in- stalled in electrical metallic tubing, wireways, auxiliary gutters, bus- ways or as a cablebus installed for services in accordance with Article 365. Service-entrance conductors should not be run within the hollow spaces of frame buildings unless provided with overcurrent protection at their outer end. 230-45. Conductor Considered Outside Building. Conductors placed under at least two inches of concrete beneath a building, or conductors within a building in conduit or duct and enclosed by concrete or brick not less than two inches thick shall be considered outside the building. 230-46. Mechanical Protection. Individual open conductors or cables other than approved service-entrance cables, shall not be installed within 8 feet of the ground or where exposed to physical damage. Service-entrance cables, where liable to contact with awnings, shutters, swinging signs, installed in exposed places in driveways, near coal chutes or otherwise exposed to physical damage, shall be of the pro- tected type or be protected by conduit, electrical metallic tubing or other approved means. 230-47. Individual Open Conductors Exposed to Weather. Individual open conductors exposed to weather shall be supported on insulators, racks, brackets, or other means, placed at intervals not exceeding 9 feet and separating the conductors at least 6 inches from each other and 2 inches from the surface wired over; or at intervals not exceeding 15 feet if they maintain the conductors at least 12 inches apart. For 300 volts or less, conductors may have a separation of not less than 3 inches where supports are placed at intervals not exceeding 41 feet and con- ductors are not less than 2 inches from the surface wired over. 230-48. Individual Open Conductors Not Exposed to Weather. Indi- vidual open conductors not exposed to the weather may be supported on glass or porcelain knobs placed at intervals not exceeding 41/2 feet and maintaining the conductors at least one inch from the surface wired over and a separation of at least 21/ inches between conductors. 230-49. Individual Conductors Entering Buildings. Individual conduc- tors entering buildings shall pass inward and upward through slanting noncombustible, nonabsorptive insulating tubes, or shall enter through roof bushings, and shall conform to the provisions of Article 324. Drip loops shall be formed on the conductors before entering tubes. 230-50. Service Cables. Service cables of a type not approved for mounting in contact with a building shall have insulating supports at in- tervals not exceeding 15 feet, and maintaining a distance of at least 2 inches from the surface wired over. Service cables mounted in contact with the building shall be supported at intervals not exceeding 41/2 feet. 230-51. Connections at Service Head. (a) Service raceways shall be equipped with a raintight service head. 70-46 NATIONAL ELECTRICAL CODE (b) Service cables, unless continuous from pole to service equipment or meter, shall be either: (1) equipped with a raintight service head or (2) formed in a gooseneck, taped and painted or taped with a self- sealing weather-resistant thermoplastic. (c) Service heads and goosenecks in service-entrance cables shall be located above the point of attachment of the service-drop conductors to the building or other structure. Exception: Where it is impracticable to locate the service head above the point of attachment, the service head may be located not farther than twenty-four inches from the point of attachment. (d) Service cables shall be held securely in place by connection to service-drop conductors below the gooseneck or by a fitting approved for the purpose. (e) Service heads shall have conductors of opposite polarity brought out through separately bushed holes. (f) Drip loops shall be formed on individual conductors. To prevent the entrance of moisture,service-entrance conductors shall be connected to the service-drop conductors either: (1) below the level of the service head,or (2) below the level of the termination of the service-entrance cable sheath. (g) Service-drop conductors and service-entrance conductors shall be so arranged that water will not enter service raceway or equipment. 230-52. Enclosing Raceways Made Raintight. When rigid metal race- ways are installed where exposed to weather the raceways shall be made raintight and arranged to drain. 230-53. Terminating Raceway at Service Equipment. Where conduit, electrical metallic tubing, or service cable is used for service conduc- tors, the inner end shall enter a terminal box or cabinet, or be made up directly to an equivalent fitting, enclosing all live metal parts, except that where the service disconnecting means is mounted on a switch- board having exposed bus-bars on the back, the raceway may be equipped with a bushing which shall be of the insulating type unless lead-covered conductors are used. G. Service Equipment 230-60. Hazardous Locations. Service equipment installed in hazard- ous locations shall comply with the requirements of Articles 500 to 517 inclusive. 230-61. Service Equipment Grouped. Where supplied at the same side of the building by more than one overhead service drop or more than one set of underground service conductors, the service equipment, ex- cept for services as permitted in Section 230-2, shall be grouped and equipment marked to indicate the load it serves. H. Grounding and Guarding 230-62. Guarding. Live parts of service equipment shall be enclosed so that they will not be exposed to accidental contact, unless mounted ARTICLE 230—SERVICES 70-47 on a switchboard, panelboard or controller accessible to qualified per- sons only and located in a room or enclosure free from easily ignitible material. Such an enclosure shall be provided with means for locking or sealing doors giving access to live parts. 230-63. Grounding and Bonding. Service equipment shall be grounded as follows: (a) Equipment. The enclosure for service equipment shall be grounded in the manner specified in Article 250, unless (1) the volt- age does not exceed 150 volts to ground and such enclosures are (2) isolated from conducting surfaces, and (3) unexposed to contact by persons or materials that may also be in contact with other conducting surfaces. (b) Raceways and Cable Armor. Service raceways, cable armor and the metal sheath of service cables, shall be grounded. Conduit and metal pipe from underground supply shall be considered sufficiently grounded where containing lead-sheathed cable bonded to a continuous underground lead-sheathed cable system. (c) Flexible Conduit. Where a service run of rigid metal raceway is interrupted by flexible metal conduit, the sections of rigid metal race- way thus interrupted shall be bonded together by a copper conductor not smaller than specified for grounding conductors in Table 250-94 (a), using clamps or other approved means. The conductor and bond- ing devices shall be protected from physical damage. Where the flexible conduit runs to the service cabinet, similar bonding shall be installed between the cabinet and the rigid raceway. J. Disconnecting Means 230-70. General. (a) Disconnection from Service Conductors. Means shall be pro- vided for disconnecting all conductors in the building or other structure from the service entrance conductors. (b) Location. The disconnecting means shall be located at a readily accessible point nearest to the entrance of the conductors, either inside or outside the building or structure. Sufficient access and working space shall be provided about the disconnecting means. In a multiple occupancy building, each occupant shall have access to his disconnecting means. A multiple occupancy building having in- dividual occupancy above the second floor shall have service equipment grouped in a common accessible place, the disconnecting means con- sisting of not more than six switches or six circuit breakers. Multiple occupancy buildings that do not have individual occupancy above the second floor may have service conductors run to each occupancy in ac- cordance with Section 230-2, Exception No. 3 and each such service may have not more than six switches or circuit breakers. (c) Approval. The disconnecting means shall be of a type approved for service equipment and for prevailing conditions. (d) Types Permitted. The disconnecting means for ungrounded con- ductors shall consist of either: 70-48 NATIONAL ELECTRICAL CODE (1) A manually operable switch or circuit breaker equipped with a handle or other suitable operating means positively identified and marked for mechanical operation by hand. (2) An electrically operated switch or circuit breaker provided the switch or circuit breaker can be opened by hand in event of a failure of the power supply and the open and closed positions are clearly indi- cated to the operator. (e) Externally Operable. An enclosed service switch or circuit breaker shall be externally operable. (f) Indicating. The disconnecting means shall plainly indicate whether it is in the open or closed position. (g) Switch and Circuit Breaker. The disconnecting means for each set or sub-set of service-entrance conductors shall consist of not more than six switches or six circuit breakers in a common enclosure, or group of separate enclosures. Two or three single pole switches or breakers, capable of individual operation, may be installed on multi- wire circuits, one pole for each ungrounded conductor, as one multipole disconnect provided they are equipped with "handle ties," "handles within 1/16 inch proximity," a "master handle," or "other means," making it practical to disconnect all conductors of the service with no more than six operations of the hand. See Section 384-16(a). (h) Simultaneous Openings. The disconnecting means shall simul- taneously disconnect all ungrounded conductors, except for 3-wire direct-current or single-phase circuits or multiwire circuits that do not supply polyphase motors. See Section 200-5(a). (i) Disconnection of Grounded Conductor. Where the switch or cir- cuit breaker does not interrupt the grounded conductor, other means shall be provided in the service cabinet or on the switchboard for dis- connecting the grounded conductor from the interior wiring. 230-71. Rating of Service Equipment. (a) The service equipment shall have a rating not less than the load to be carried determined in accordance with Article 220. The service disconnecting means shall have a rating of not less than 60 amperes except: Exception No 1. For single family residences with an initial load of 10 KW or more computed in accordance with Article 220, or if the initial installation has more than five 2-wire branch circuits, the service equipment shall have a rating of not less than 100 amperes 3-wire. Exception No. 2. For installations consisting of not more than two 2-wire branch circuits a service equipment of 30-ampere minimum rating may be used. (b) Where multiple switches or circuit breakers are used in accord- ance with Section 230-70(g) the combined rating shall not be less than required for a single switch or breaker. ARTICLE 230—SERVICES 70-49 230-72. Connection to Terminals. The service conductors shall be at- tached to the disconnecting means by pressure connectors, clamps or other approved means, except that connections which depend upon solder shall not be used. 230-73. Connections Ahead of Disconnecting Means. The following may be connected ahead of the service disconnecting means: (a) Service fuses, high-impedance shunt circuits, time switches, surge protective capacitors, instrument transformers (current and potential) and lightning arresters. (b) Taps used only to supply time switches, circuits for emergency systems,fire pump equipment,fire and sprinkler alarms if provided with service equipment and installed in accordance with requirements for service-entrance conductors. (c) Meters nominally rated not in excess of 600 volts, provided all metal housings and service enclosures are grounded in accordance with Article 250. For detailed service provisions for fire alarm, sprinkler supervisory, or watchman systems, see appropriate Standards of the National Fire Protec- tion Association. 230-74. Safeguarding Emergency Supply. Where an emergency sup- ply is provided to feed the conductors controlled by the service dis- connecting means, the disconnector shall be of a design that will open all ungrounded conductors from the usual supply before connection is made to the emergency supply, unless agreed upon arrangements have been made for parallel operation and suitable automatic control equip- ment provided.See Article 700. 230-76. More than One Building. In a property comprising more than one building under single management, the conductors supplying each building served shall be provided with a readily accessible means, within or adjacent to the building, of disconnecting all ungrounded conductors from the source of supply. In garages and outbuildings on residential property the disconnecting means may consist of a snap switch, suitable for use on branch circuits, including switch controls at more than one point. K. Overcurrent Protection 230-90. Where Required. Each ungrounded service-entrance con- ductor shall have overcurrent protection. (a) Ungrounded Conductor. Such protection shall be provided by an overcurrent device in series with each ungrounded service conduc- tor, having a rating or setting not higher than the allowable ampacity of the conductor,except as follows: Exception No. 1. For motor-starting currents, ratings in conformity with Sections 430-52,430-62,or 430-63 may be used. Exception No. 2. Fuses and circuit breakers may have a rating or setting in conformity with Section 240-5(a), Exceptions No. I and 2, also Section 240-5(b). 70-50 NATIONAL ELECTRICAL CODE Exception No. 3. Not more than six circuit breakers or six sets of fuses may serve as the overcurrent device. Exception No. 4. In a multiple occupancy building each occupant shall have access to his overcurrent protective devices. A multiple oc- cupancy building having individual occupancy above the second floor shall have service equipment grouped in a common accessible place, the overcurrent protection consisting of not more than six circuit breakers or six sets of fuses. Multiple occupancy buildings that do not have individual occupancy above the second floor may have service conductors run to each occupancy and each such service may have not more than six circuit breakers or six sets of fuses. A set of fuses is all the fuses required to protect all the ungrounded con- ductors of a circuit. Single pole breakers may be grouped as in Section 230- 70(g) as one multiple protective device. (b) Not in Grounded Conductor. No overcurrent device shall be in- serted in a grounded service conductor except a circuit breaker which simultaneously opens all conductors of the circuit. (c) More Than One Building. In a property comprising more than one building under single management, the ungrounded conductors supplying each building served shall be protected by overcurrent de- vices, which may be located in the building served or in another build- ing on the same property, provided they are accessible to the occupants of the building served. 230-91. Location. The service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto,unless located at the outer end of the entrance. 230-92. Location of Branch-Circuit Overcurrent Devices. Where the service overcurrent devices are locked or sealed, or otherwise not read- ily accessible, branch-circuit overcurrent devices shall be installed on the load side, shall be mounted in an accessible location and shall be of lower rating than the service overcurrent device. 230-93. Protection of Specific Circuits. Where necessary to prevent tampering, an automatic overcurrent device protecting service con- ductors supplying only a specific load such as a water heater, may be locked or sealed where located so as to be accessible. 230-94. Relative Location of Overcurrent Device and Other Service Equipment. The overcurrent device shall protect all circuits and de- vices except as follows: (a) The service switch may be placed on the supply side. (b) High impedance shunt circuits, lightning arresters, surge protec- tive capacitors, instrument transformers, (current and potential), may be connected and installed on the supply side of the service disconnect- ing means as permitted in Section 230-73. (c) Circuits for emergency supply and time switches may be con- nected on the supply side of the service overcurrent device where sep- arately provided with overcurrent protection. (d) Circuits used only for the operation of fire alarm, other protec- tive signalling systems, or the supply to fire pump equipment may be ARTICLE 230—SERVICES 70-51 connected on the supply side of the service overcurrent device where separately provided with overcurrent protection. (e) Meters nominally rated not in excess of 600 volts, provided all metal housings and service enclosures are grounded in accordance with Article 250. L.Services Exceeding 600 Volts 230-100. Scope. Service conductors and equipment used on circuits exceeding 600 volts shall comply with the applicable provisions of the preceding Sections of this Article and with the following Sections which are additions to or modifications of the preceding Sections. Secondary conductors, not the primary conductors, are the service conductors to the building proper in the following cases: 1. Where step-down transformers are located outdoors. 2. Where step-down transformers are located in a separate build- ing from the one served. 3. Where step-down transformers are located in the building served in transformer vaults, locked rooms or locked enclosures in accordance with Article 450 and accessible only to qualified persons. In all other cases, the primary conductors are the service conductors. In no case will the provisions of this Article apply to equipment con- nected ahead of the service conductors. 230-101. Service-Entrance Conductors. (a) Conductor Size. Service conductors shall be not smaller than No. 6 unless in cable. Conductors in cable shall be not smaller than No. 8. (b) Wiring Methods. In locations accessible to other than qualified persons service-entrance conductors of more than 600 volts shall be in- stalled in rigid conduit, or as multiple conductor cable approved for the purpose. (c) Open Work. If open work is employed where not accessible to other than qualified persons, the service conductors shall be rigidly supported on glass, porcelain or other insulators approved for the pur- pose, which will keep them at least 8 inches apart, except at terminals of equipment. They shall be not less than 2 inches from the surfaces wired over and for voltages exceeding 2,500 not less than 3 inches. (d) Supports. Service conductors and their supports, including in- sulators, shall have strength and stability sufficient to insure mainte- nance of adequate clearance with abnormal currents in case of short circuits. (e) Guarding. Open wires shall be guarded where accessible to un- qualified persons. (f) Service Cable. Where cable conductors emerge from a metal sheath or raceway, the insulation of the conductors shall be protected from moisture and physical damage by a pothead or other approved means. 70-52 NATIONAL ELECTRICAL CODE (g) Draining Raceways. Unless conductors specifically approved for the purpose are used, raceways embedded in masonry, or exposed to the weather,or in wet locations shall be arranged to drain. (h) Over 15,000 Volts. Where the voltage exceeds 15,000 volts between conductors they shall enter either metal enclosed switchgear or a transformer vault conforming to the requirements of Section 450- 41 to 450-48. (i) Conductor Considered Outside Building. Conductors placed un- der at least two inches of concrete beneath a building, or conductors within a building in conduit or duct and enclosed by concrete or brick not less than two inches thick shall be considered outside the building. 230-102. Warning Signs. High voltage signs shall be posted where unauthorized persons might come in contact with live parts. 230-103. Disconnecting Means. The circuit-breaker or the alternatives for it specified in Section 230-106 will constitute the disconnecting means required by Section 230-70 and shall comply with Section 230- 70(h). The disconnecting means shall be capable of being closed on a fault within the maximum interrupting rating of the overcurrent pro- tection. 230-104. Isolating Switches. Isolating switches shall be provided as follows: (a) Air-break isolating switches shall be installed between oil switches or air or oil circuit breakers used as service switches and the supply conductor, except where such equipment is mounted on remov- able truck panels or metal-enclosed switchgear units which cannot be opened unless the circuit is disconnected, and which, when removed from the normal operating position, automatically disconnect the cir- cuit breaker or switch from all live parts. (b) When the fuses used with nonautomatic oil switches in accord- ance with Section 230-106 are of a type that may be operated as a dis- connect switch, they may serve as the isolating switch when they com- pletely disconnect the oil switch and all service equipment from the source of supply. (c) Air-break isolating switches shall be accessible to qualified attend- ants only. They shall be arranged so that a grounding connection on the load side can readily be made. Such grounding means need not be provided for duplicate isolating switches, if any, installed and main- tained by the supply company. 230-105. Equipment in Secondaries. Where the primary service equip- ment supplies one or more transformers whose secondary windings con- nect to a single set of mains, and the primary load-interrupter switch or circuit-breaker is capable of being opened and closed from a point outside the transformer vault, the disconnecting means and overcurrent protection may be omitted from the secondary circuit provided the pri- mary fuse or circuit-breaker is rated or set to protect the secondary circuit. 230-106. Overcurrent Protection. Overcurrent devices shall be pro- vided in accordance with the following: ARTICLE 230—SERVICES 70-53 (a) In Vault or Consisting of Metal-Enclosed Switchgear. Where the service equipment is installed in a transformer vault meeting the provi- sions of Sections 450-41 to 450-48, or consists of metal-enclosed switch- gear, the requirements for overcurrent protection and disconnecting means may be fulfilled by the following: (1) A non-automatic oil switch, oil fuse cutout, air load-interrupter switch, or other approved switch, capable of interrupting the rated cir- cuit load,and suitable fuses may be used. (2) An automatic trip circuit-breaker of suitable current carrying and interrupting capacity with an overcurrent unit in each ungrounded conductor may be used. (3) A switch capable of interrupting the no-load current of the transformer supplied through the switch and suitable fuses may be used, provided the switch is interlocked with a single switch or circuit breaker on the secondary circuit of the transformer so that the primary switch cannot be opened when the secondary circuit is closed. (4) Metal-enclosed switchgear shall consist of a substantial metal I structure and a sheet metal enclosure. Barriers between adjacent switch- gear units and internal metal barriers shall be not less than 1/2 inch of metal or No. 11 USS gage. All other covers, panels and doors shall be not less than No. 14 USS gage. Where installed over a wood floor, suitable protection thereto shall be provided. (b) Not in Vault or Not Consisting of Metal-enclosed Switchgear. Where the service equipment is not in a vault or metal-enclosed switch- gear, the requirements for the overcurrent protection and disconnecting means may be fulfilled by the following: (1) Air load-interrupter switches, or other approved switches, ca- pable of interrupting the rated circuit load may be used with suitable fuses on a pole or elevated structure outside the building provided the switch may be operated by persons using the building. (2) On circuits of any voltage, an automatic trip circuit-breaker of suitable ampacity and interrupting capacity with an overcurrent unit in each ungrounded conductor may be used. The circuit-breaker shall be located outside the building as near as practicable to where the service conductors enter the building. The location may be on a pole, roof, foundation,or other structure. (c) Fuses. Fuses shall have an interrupting rating at least equal to the maximum short-circuit current possible in the circuit. I (d) Circuit Breakers. Circuit breakers shall be free to open in case the circuit is closed on an overload. This can be accomplished by means such as trip-free breakers or by multiple breakers having an operating handle per pole. A service circuit breaker shall indicate clearly whether it is open or closed, and shall be capable of interrupting the maximum short-circuit current to which it may be subjected. (e) Enclosed Overcurrent Devices. The restriction to 80 per cent of rating for an enclosed overcurrent device on continuous loads shall not apply to overcurrent devices installed in services operating at over 600 volts. 70-54 NATIONAL ELECTRICAL CODE 230-107. Lightning Arresters. Lightning arresters installed in accord- ance with the requirements of Article 280 shall be placed on each un- grounded overhead service conductor on the supply side of the service equipment,when called for by the authority having jurisdiction. ARTICLE 240—OVERCURRENT PROTECTION A. Installation 240-1. Scope. This Article provides the general requirements for the application of overcurrent protective devices. 240-2. Purpose of Overcurrent Protection. Overcurrent protection for conductors and equipment is provided for the purpose of opening the electric circuit if the current reaches a value which will cause an exces- sive or dangerous temperature in the conductor or conductor insulation. 240-3. Protection of Equipment. Equipment shall be protected against overcurrent as specified in the references in the following list: Equipment Article No. Appliances 422 Capacitors 460 Cranes and Hoists 610 Elevators, Dumbwaiters and Escalators 620 Emergency Systems 700 Fixed Electric Space Heating Equipment 424 Generators 445 Inductive and Dielectric Heat 665 i Generating Equipment S Machine Tools 670 , Motion Picture Studios and Similar Locations 530 i 650 ' Motors Organs 710 Over 600 Volts Remote-Control,Low-Energy Power,Low- 725 Voltage Power and Signal Circuits Services 23020 Signs and Outline Lighting 600 Sound Equipment 384 Switchboards and Panelboards Theaters and Assembly Halls 52020 Transformers 6304 Welders 660 X-ray Equipment 240-4. Time-Delay Overcurrent Devices. Circuit breakers and plug fuses installed in residential occupancies on circuits of 20 amperes or less shall be of the time-delay type. 240-5. Overcurrent Protection. (a) Conductors. Conductors shall be protected in accordance with their ampacities, as given in Tables 310-12 through 310-15, except as follows: ARTICLE 240-OVERCURRENT PROTECTION 70-55 Exception No. 1. Rating of Nonadjustable Overcurrent Protection of 800 Amperes or Less. Where the standard ampere ratings of fuses and nonadjustable circuit breakers do not correspond with the allowable ampacities of conductors, the next higher standard rating may be used, only where the rating is 800 amperes or less. Exception No. 2. Adjustable-Trip Circuit Breakers. Adjustable-trip circuit breakers of the thermal trip, magnetic time-delay trip or instan- taneous-trip types shall be set to operate at not more than 125 per cent of the allowable ampacity of the conductors. The effect of the temperature on the operation of thermally controlled circuit breakers should be taken into consideration in the application of such circuit breakers when they are subjected to extremely low or extremely high temperatures. Exception No. 3. Fixture Wires and Cords. Fixture wire or flexible cord,Size No. 16 or No. 18, and tinsel cord shall be considered as pro- tected by 20 ampere overcurrent devices except as provided in Section 620-61. Fixture wires of the sizes permitted for taps in Section 210- 19 (c-2) shall be considered as protected by the overcurrent protection of the 30, 40, and 50 ampere branch circuits of Article 210. Flexible cord approved for use with specific appliances shall be considered as protected by the overcurrent device of the branch circuit of Article 210 when conforming to the following: 20 ampere circuits,No.18 cord and larger. 30 ampere circuits,cord of 10 amperes capacity and over. 40 ampere circuits,cord of 20 amperes capacity and over. 50 ampere circuits,cord of 20 amperes capacity and over. Exception No. 4. Motor Circuits. The conductors supplying motors and motor-operated appliances shall be considered as protected by the overcurrent protective devices specified in Sections 430-32, 430-34, 430-52,430-53 and 430-62. Exception No.5.Remote Control.Except as provided in Article 725, the conductors of the control circuits of remote-control switches shall be considered as protected from overcurrent by overcurrent devices that are not of the so-called time-lag type and are rated or set at not more than 500 per cent of the ampacity of the remote-control conductors, as specified in Tables 310-12 through 310-15. (b) Standard Ratings. Standard ampere ratings for fuses and non- adjustable circuit breakers are 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000. 240-6. Fuses. (a) Plug fuses and fuseholders shall not be used in circuits exceeding 125 volts between conductors except in circuits supplied from a system having a grounded neutral and no conductor in such circuits operating at more that 150 volts to ground. (b) Cartridge fuses and fuseholders rated at 300 volts shall not be used in circuits exceeding 300 volts between conductors except in cir- cuits supplied from a system having a grounded neutral and no con- ductor in such circuits operating at more than 300 volts to ground. 70-56 NATIONAL ELECTRICAL CODE (c) The screw-shell of plug-type fuseholders shall be connected to the load side of the circuit. 240-8. Thermal Devices. Thermal cutouts, thermal relays and other devices not designed to open short-circuits, shall not be used for protec- tion of conductors against overcurrent due to short-circuits or grounds but may be used to protect motor branch circuit conductors from over- load if protected in accordance with Section 430-40. 240-9. Feeders at Supply Stations. Each conductor of a constant-po- tential circuit entering or leaving a supply station, except grounded neutral conductors, shall be protected from excessive current by a cir- cuit breaker, or by an equivalent device of approved design. Such pro- tective devices shall be located as near as practicable to the point where the conductors enter or leave the building. For the outgoing circuits not connected with other sources of power, the protective devices may be placed on the supply side of transformers or similar devices. 240-11. Ungrounded Conductors. (a) An overcurrent device (fuse or overcurrent trip unit of a circuit breaker) shall be placed in each ungrounded conductor. For motor cir- cuits see Article 430. (b) Circuit breakers shall open all ungrounded conductors of the circuit,except as follows: Exception: Individual single-pole circuit breakers may be used for the protection of each conductor of ungrounded 2-wire circuits, each ungrounded conductor of 3-wire direct-current or single-phase circuits, or for each ungrounded conductor of lighting or appliance branch cir- cuits connected to 4-wire three-phase systems, or 5-wire 2-phase sys- tems, provided such lighting or appliance circuits are supplied from a system having a grounded neutral and no conductor in such circuits operates at a voltage greater than permitted in Section 210-6. 240-12. Grounded Conductor. No overcurrent device shall be placed in any permanently grounded conductor,except as follows: Exception No. 1. Where the overcurrent device simultaneously opens all conductors of the circuit. Exception No. 2. For motor-running protection as provided in Sec- tions 430-36 and 430-37. 240-13. Change in Size of Grounded Conductor. Where a change oc- curs in the size of the ungrounded conductor, a similar change may be made in the size of the grounded conductor. 240-14. Fuses or Circuit Breakers in Parallel. Overcurrent devices con- sisting of fuses and/or circuit breakers shall not be arranged or in- stalled in parallel. Exception: Circuit breakers assembled in parallel which are tested and approved as a single unit. B. Location 240-15. Location in Circuit. Overcurrent devices shall be located at the point where the conductor to be protected receives its supply, ex- cept as follows: ARTICLE 240—OVERCURRENT PROTECTION 70-57 Exception No. 1. Service Conductors. An overcurrent protective device for service conductors may be located as specified in Section 230-91. Exception No. 2. Smaller Conductor Protected. Where the overcur- rent device protecting the larger conductors also protects the smaller conductors in accordance with Tables 310-12 through 310-15. Exception No. 3. Branch Circuits. Taps to individual outlets and circuit conductors supplying a single household electric range shall be considered as protected by the branch circuit overcurrent devices when in accordance with the requirements of Sections 210-19, 210-20 and 210-25. Exception No. 4. Feeder Taps. A conductor tapped from a feeder shall be considered as properly protected from overcurrent when in- stalled in accordance with Sections 364-8 and 430-59. Exception No. 5. Feeder Taps Not Over 10 Feet Long. Where (1) the smaller conductor has an ampacity of not less than the sum of the allowable ampacities for the conductors of the one or more circuits or loads supplied, and (2) the tap is not over 10 feet long and does not extend beyond the switchboard, panelboard, or control devices which it supplies,and (3) except at the point of connection to the feeder, the tap is enclosed in conduit, electrical metallic tubing, or in metal gutters when not a part of the switchboard or panelboard. Exception No. 6. Feeder Taps Not Over 25 Feet Long. Where the smaller conductor has an ampacity at least one-third that of the con- ductor from which it is supplied, and provided the tap is suitably pro- tected from physical damage, is not over 25 feet long, and terminates in a single circuit breaker or set of fuses which will limit the load on the tap to that allowed by Tables 310-12 through 310-15.Beyond this point the conductors may supply any number of circuit breakers or sets of fuses. 240-16. Location in Premises. Overcurrent devices shall be located where they will be: (a) Readily accessible, except as provided in Sections 230-91 and 230-92 for service equipment and Section 364-11 for busways. (b) Not exposed to physical damage. (c) Not in the vicinity of easily ignitible material. C. Enclosures 240-17. Enclosures for Overcurrent Devices. (a) General. Overcurrent devices shall be enclosed in cutout boxes or cabinets, unless a part of a specially approved assembly which af- fords equivalent protection, or unless mounted on switchboards, panel- boards or controllers located in rooms or enclosures free from easily ignitible material and dampness. The operating handle of a circuit breaker may be accessible without opening a door or cover. (b) Damp or Wet Locations. Enclosures for overcurrent devices in damp or wet locations shall be of a type approved for such locations and shall be mounted so there is at least one-fourth inch air space be- tween the enclosure and the wall or other supporting surface. 70-58 NATIONAL ELECTRICAL CODE (c) Vertical Position. Enclosures for overcurrent devices shall be mounted in a vertical position unless in individual instances this is shown to be impracticable. (d) Rosettes. Fuses shall not be mounted in rosettes. D. Disconnecting and Guarding 240-18. Disconnection of Fuses and Thermal Cutouts Before Handling. Disconnecting means shall be provided on the supply side of all fuses or thermal cutouts in circuits of more than 150 volts to ground and cartridge fuses in circuits of any voltage, where accessible to other than qualified persons, so that each individual circuit containing fuses or thermal cutouts can be independently disconnected from the source of electrical energy, except as provided in Section 230-73 and except that a single disconnecting means may be used to control a group of circuits each protected by fuses or thermal cutouts under the conditions de- scribed in Section 430-112. 240-19. Arcing or Suddenly Moving Parts. Arcing or suddenly mov- ing parts shall comply with the following: (a) Location. Fuses and circuit breakers shall be so located or shielded that persons will not be burned or otherwise injured by their operation. (b) Suddenly Moving Parts. Handles or levers of circuit breakers, and similar parts which may move suddenly in such a way that persons in the vicinity are liable to be injured by being struck by them, shall be guarded or isolated. E. Plug Fuses and Fuseholders 240-20. Plug Fuses of the Edison-Base Type. Plug fuses of the Edison- base type shall conform to the following: (a) Classification. Plug fuses of this type shall be classified at not over 125 volts,0 to 30 amperes. (b) Live Parts. Fuses and fuseholders when installed and assembled together shall have no live parts exposed. (c) Marking. Plug fuses of 15 amperes rating or less shall be dis- tinguished from those of larger rating by an hexagonal opening in the cap through which the mica or similar window shows, or by some other prominent hexagonal feature such as the form of the top or cap itself,or an hexagonal recess or projection in the top or cap. Plug fuses of the Edison-base type are recognized in this Code only as a replacement item in existing installations where there has been no evidence of overfusing or tampering. 240-21. Fuseholders for Plug Fuses. Fuseholders for plug fuses of 30 amperes or less shall not be installed unless they comply with Section 240-22 or are made to comply with Section 240-22 by the insertion of an adapter. 240-22. Plug Fuses and Fuseholders of Type S. Where Type S plug fuses are to be used as the overcurrent device required by this Code, the fuses and fuseholders shall conform to the following requirements: ARTICLE 240—OVERCURRENT PROTECTION 70-59 (a) Classification. Plug fuses and fuseholders of Type S shall be classified at not over 125 volts; 0 to 15 amperes, 16 to 20 amperes, and 21 to 30 amperes. (b) Use of Fuses in a Fuseholder of a Different Classification. Fuses of the 16 to 20 ampere and the 21 to 30 ampere classification shall not be usable with fuseholders or adapters of a lower ampere classification. (c) Fuseholders and Adapters. Fuses, fuseholders, and adapters shall be so designed that a fuse other than a Type S fuse cannot be used in a fuseholder or adapter designed for Type S fuses. (d) Tamperability. Fuses, fuseholders and adapters shall be so de- signed as to be subject to tampering or bridging only with difficulty. (e) Adapters to be Nonremovable. Fuse adapters shall be so de- signed that when once inserted in a fuseholder they cannot be removed. (f) Interchangeability. Fuses, fuseholders and adapters of various manufacturers shall be interchangeable with each other, and the plugs with adapters shall be suitable for use in the Edison-base type fuse- holder. (g) Plug Type. Fuses and fuseholders shall be of the plug type. (h) Ampere Rating. Each fuse, fuseholder and adapter shall be marked with its ampere rating. (i) Marking. Fuses of the 0 to 15 ampere rating shall be distin- guished from those of larger rating by an hexagonal opening in the cap through which the mica or similar window shows, or some other prom- inent hexagonal feature such as the form of the top or cap itself, or an hexagonal recess or projection in the top or cap. F. Cartridge Fuses and Fuseholders 240-23. Cartridge Fuses and Fuseholders. Cartridge fuses and fuse- holders shall conform to the following: (a) Classification. (1) 0-600 ampere cartridge fuses and fuseholders shall be classi- fied as regards current and voltage as follows: Not over 250 volts Not over 300 volts Not over 600 volts Amperes Amperes Amperes 0- 30 0-15 0- 30 31- 60 16-20 31- 60 61-100 21-30 61-100 101-200 31-60 101-200 201-400 - 201-400 401-600 - 401-600 (2) 601-6000 ampere cartridge fuses and fuseholders shall be clas- sified at 600 volts as follows: 601- 800 1601-2000 3001-4000 801-1200 2001-2500 4001-5000 1201-1600 2501-3000 5001-6000 There are no 250 volt ratings over 600 amperes, but 600 volt fuses may be used for lower voltages. 70-60 NATIONAL ELECTRICAL CODE (b) Noninterchangeable—O-6000 Ampere Cartridge Fuseholders. Fuseholders shall be so designed that it will be difficult to put a fuse of any given class into a fuseholder which is designed for a current lower, or voltage higher, than that of the class to which it belongs. Fuseholders for current limiting fuses shall not permit insertion of fuses which are not current limiting. (c) Marking. Fuses shall be plainly marked with the ampere rating, voltage rating, interrupting rating when greater than 10,000 amperes, current limitation where it applies, and the name or trademark of the maker.The marking shall be either by direct printing on the fuse barrel or by means of an attached label. G. Link Fuses and Fuseholders 240-24. Link Fuses and Fuseholders. Link fuses and fuseholders shall be used only by special permission and shall conform to the following: (a) Mounting. Link fuses shall be mounted on approved fusehold- ers. (b) Dimensions. Link fuses and fuseholders shall have the following dimensions in inches: Minimum Separation of Nearest Metal Minimum Parts of Opposite Break Amperes Capacity Polarity Distance Not over 125 volts 601-1500 11 11/2 Not over 250 volts 601-1500 23/4 2 For 3-wire systems, link fuses, and fuseholders shall have the break distance required for circuits of the potential of the outside wires, ex- cept that in 125-250-volt systems with grounded neutral the fuses and fuseholders in 2-wire, 125-volt branch circuits may have the spacing specified for not over 125 volts. (c) Spacing. A space shall be maintained between the fuse termi- nals of link fuses of the same polarity of at least 1/2 inch for voltages up to 125, and of at least 3/4 inch for voltages from 126 to 250. This is the minimum distance allowable and greater separation shall be pro- vided where practicable. (d) Material. Contact surfaces or tops of link fuses shall be of cop- per or aluminum having good electrical connections with the fusible part of the strip. (e) Minimum Rating. Link fuses and fuseholders shall be used only in sizes rated at more than 600 amperes,and only by special permission. (f) Marking. Link fuses shall be stamped with 80 per cent of the maximum current which they can carry indefinitely. H. Circuit Breakers 240-25. Circuit Breakers. Circuit breakers shall conform to the fol- lowing: (a) Method of Operation. In general, circuit breakers shall be ca- pable of being closed and opened by hand without employing any ARTICLE 250—GROUNDING 70-61 other source of power, although normal operation may be by other power such as electrical, pneumatic, and the like. Large circuit break- ers which are to be closed and opened by electrical, pneumatic, or other power shall be capable of being closed by hand for maintenance purposes and shall also be capable of being tripped by hand under load without the use of power. (b) Type of Operation. Circuit breakers of the 0 to 30 ampere class should be of the time-delay type. (c) Injury to Operator. Circuit breakers shall be arranged and mounted so that their operation is not likely to injure the operator. (d) Indication. Circuit breakers shall indicate whether they are in the open or closed position. (e) Nontamperable. An air circuit breaker, used for the branch circuits described in Article 210, shall be of such design that any altera- tion of its trip point (calibration), or in the time required for its opera- tion,will be difficult. (f) Marking. Circuit breakers shall be marked with their rating in such a manner that the marking will be durable and visible after instal- lation except that it may be necessary to remove a trim or cover. The ampere rating of circuit breakers rated 100 amperes or less and 600 volts or less shall be molded, stamped, etched, or similarly marked into the handle or the escutcheon area of the circuit breaker. Each circuit breaker intended to interrupt fault currents greater than 10,000 am- peres shall have its interrupting rating shown on the label or on the product. I. General 240-27. Current Limiting Overcurrent Protective Device. A current lim- iting overcurrent protective device is a device which, when interrupting a specified circuit, will consistently limit the short-circuit current in that circuit to a specified magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance. 240-30. Supplementary Overcurrent Protection. Where supplementary overcurrent protection is utilized in connection with appliances or other utilization equipment to provide individual protection for specific com- ponents or internal circuits within the equipment itself, this does not abrogate any of the requirements applicable to branch circuits and is not to be used as a substitute for branch-circuit protection. It is not the intent of the above requirement that supplementary overcur- rent protective devices be subject to the accessibility requirements as given elsewhere in this code for branch circuit overcurrent protective devices. ARTICLE 250—GROUNDING A. General 250-1. Scope. This Article treats of protection of electric installations by grounding. Insulation, isolation, and guarding are suitable alterna- tives under certain conditions.See Section 110-17. (a) Systems and Circuits. Circuits are grounded for the purpose of limiting the voltage upon the circuit which might otherwise occur through exposure to lightning or other voltages higher than that for 70-62 NATIONAL ELECTRICAL CODE which the circuit is designed; or to limit the maximum potential to ground due to normal voltage. (b) Exposed Enclosures. Conductive materials enclosing electric con- ductors or equipment,or forming part of such equipment, are grounded for the purpose of preventing a potential above ground on these mate- rials. (c) Operation of Overcurrent Devices. Circuits and enclosures are grounded to facilitate overcurrent device operation in case of insulation failure or ground faults.See Section 110-10. 250-2. Other Articles. In other Articles, applying to particular cases of installation of conductors and equipment, there are requirements that are in addition to those of this Article or are modifications of them: Article Section Appliances 422-16 Boat Harbor Wiring 555-6 Branch Circuits 210-5 210-6 Cablebus 365-9 Communications Circuits 800 Community Antenna Television and Radio Dis- tribution Systems 820-3 820-8 820-9 Conductors 310 Conductors (Grounded) 200 Cranes and Hoists 610 Data Processing Systems 645-4 Elevators,Dumbwaiters, Escalators, and Moving Walks 620 Fixed Electric Space Heating Equipment 424-79 Fixtures & Lighting Equipment 410-91 410-92 410-93 410-94 410-95 410-96 Flexible Cords 400-13 400-14 Generators 445-8 Grounding Receptacles (Outlets) 210-7 210-21 210-22 Hazardous Locations 500-517 Inductive and Dielectric Heat Generating Equip- ment 665 Less Than 50 V 720 Lighting Fixtures 410 Metalworking Machine Tools 670 Mobile Homes 550 Motion Picture Studios 530-19 530-66 ARTICLE 250—GROUNDING 70-63 Article Section Motors and Controllers 430 Organs 650 Outlet, Switch and Junction Boxes, and Fittings 370-4 370-15 Radio and Television 810 Receptacles & Attachment Plugs 410-55 410-56 Remote Control Circuits 725-21 Services 230 Service Equipment 230-63 Signs and Outline Lighting 600 Sound Recording Equipment 640-4 Swimming Pools 680 Switchboards 384-11 Switches 380-1 380-12 Theaters & Assembly Halls 520-81 Transformers 450-8 Travel Trailers 551 X-ray Equipment 660 B. Circuit and System Grounding 250-3. Two-Wire Direct-Current Systems. Two-wire direct-current sys- tems supplying interior wiring, and operating at not more than 300 volts between conductors, shall be grounded, unless such system is used for supplying industrial equipment in limited areas and the circuit is equipped with a ground detector. It is recommended that 2-wire direct-current systems operating at more than 300 volts between conductors be grounded when a neutral point can be established such that the maximum difference of potential between the neutral point and any other point on the system does not exceed 300 volts. It is recommended that 2-wire direct-current systems be not grounded when the voltage to ground of either conductor would exceed 300 volts after grounding. 250-4. Three-Wire Direct-Current Systems. The neutral conductor of all 3-wire direct-current systems supplying interior wiring shall be grounded. 250-5. Alternating-Current Systems. Secondary alternating-current systems supplying interior wiring, and interior alternating-current wir- ing systems, except those covered in Sections 250-6, 250-7 and 250-8, shall be grounded when they can be so grounded that the maximum voltage to ground does not exceed 150 volts. Where a service conduc- tor is uninsulated in accordance with Section 230-4, the system shall be grounded. It is recommended that alternating-current systems be grounded as pro- vided in this article when the voltage to ground does not exceed 300 volts. Higher voltage systems may be grounded. It is also recommended that ungrounded systems supplying industrial equipment and operating at more than 150 volts and less than 600 volts be equipped with ground detectors. 250-6. Furnace Circuits. Electric furnace circuits need not be grounded. 70-64 NATIONAL ELECTRICAL CODE 250-7. Electric Crane Circuits. Circuits for electric cranes operating over combustible fibers in Class III hazardous locations shall not be grounded.See Section 503-13. 250-8. Circuits of Less than 50 Volts. Circuits of less than 50 volts need not be grounded,except as follows: (a) Where supplied by transformers from systems of more than 150 volts to ground,except as provided in Section 250-45(d). (b) Where supplied by transformers from ungrounded systems. (c) Where run overhead outside buildings. C. Location of Grounding Connections 250-21. Current Over Grounding Conductors. The grounding of wiring systems, circuits, arresters, cable armor, conduit, or other metal race- ways as a protective measure shall be so arranged that there will be no objectionable passage of current over the grounding conductors. The temporary currents set up under accidental conditions, while the grounding conductors are performing their intended protective func- tions, are not to be considered as objectionable. Where an objection- able flow of current occurs over a grounding conductor, due to the use of multiple grounds, (1) one or more of such grounds shall be aban- doned, or (2) their location shall be changed, or (3) the continuity of the conductor between the grounding connections shall be suitably in- terrupted, or (4) other means satisfactory to the authority having jurisdiction shall be taken to limit the current. 250-22. Grounding Connection for Direct-Current Systems. Direct-cur- rent systems which are to be grounded shall have the grounding con- nection made at one or more supply stations but not at individual services nor elsewhere on interior wiring. 250-23. Grounding Connections for Alternating-Current Systems. (a) Secondary alternating-current circuits which are to be grounded shall have a connection to a grounding electrode at each service, except as provided for in Section 250-21. The connection shall be made on the supply side of the service disconnecting means. Each secondary distribu- tion system which is grounded shall have at least one additional ground- ing conductor connection to a grounding electrode at the transformer or elsewhere.No connection to a grounding electrode shall be made to the grounded circuit conductor on the load side of the service disconnecting means. See Section 250-24 for two or more buildings supplied by a single service and Section 250-26 for separately derived systems. (b) Where the secondary system is grounded at any point, the grounded conductor shall be run to each service. This conductor shall be not smaller than the required common main grounding conductor specified in Table 250-94(a) and, in addition, for service phase con- ductors larger than 1100 MCM the grounded conductor shall be not smaller than 121/2 per cent of the area of the largest phase conductor. 250-24. Two or More Buildings Supplied by a Single Service. Where more than one building is supplied by the same service, the grounded circuit conductor of the wiring system of any building utilizing one ARTICLE 250—GROUNDING 70-65 branch circuit supplied from such service may be connected to a grounding electrode at such building, and in the case of any building housing equipment required to be grounded or utilizing two or more branch circuits supplied from such service, and in the case of a build- ing housing live stock,shall be so connected. 250-25. Conductor to be Grounded. For alternating-current interior wiring systems the conductor to be grounded shall be as follows: (a) Single-phase,2-wire: the identified conductor; (b) Single-phase, 3-wire: the identified neutral conductor; (c) Multiphase systems having one wire common to all phases: the identified common conductor; (d) Multiphase systems having one phase grounded: the identified conductor; (e) Multiphase systems in which one phase is used as in (b): the identified neutral conductor. One phase only can be grounded. See Article 200. The identified conductor is commonly known as"the white wire." 250-26. Separately Derived Systems. For an interior wiring system which is required by Section 250-5 to be grounded, the phase conduc- tors of which are not electrically connected to another supply system, a common main grounding conductor shall be connected at the trans- former, generator or other source of supply or at the switchboard on the supply side of the disconnecting means of the system. D. Enclosure Grounding 250-32. Service Conductor Enclosures. Service raceways, service cable sheaths or armoring,when of metal,shall be grounded. 250-33. Other Conductor Enclosures. Metal enclosures for conductors shall be grounded, except they need not be grounded in runs of less than 25 feet which are free from probable contact with ground, grounded metal, metal lath or conductive thermal insulation and which, where within reach from grounded surfaces, are guarded against con- tact by persons. 250-34. Spacing from Lightning Rods. Metal enclosures of conduc- tors shall, wherever practicable, be kept at least 6 feet away from light- ning rod conductors. Where it is not practicable to secure 6 feet sepa- ration,they shall be bonded together. E. Equipment Grounding 250-42. Fixed Equipment—General. Under any of the following con- ditions, exposed, noncurrent-carrying metal parts of fixed equipment, which are liable to become energized,shall be grounded: (a) Where equipment is supplied by means of metal-clad wiring; (b) Where equipment is located in a wet location and is not isolated; (c) Where equipment is located within reach of a person who can make contact with any grounded surface or object; (d) Where equipment is located within reach of a person standing on the ground; 70-66 NATIONAL ELECTRICAL CODE (e) Where equipment is in a hazardous location; see Articles 500-517 inclusive; (f) Where equipment is in electrical contact with metal or metal lath; (g) Where equipment operates with any terminal at more than 150 volts to ground,except as follows: (1) Enclosures for switches or circuit breakers where accessible to qualified persons only; (2) Metal frames of electrically heated devices, exempted by spe- cial permission, in which case the frames shall be permanently and effectively insulated from ground; (3) Transformers mounted on wooden poles at a height of more than 8 feet from the ground. 250-43. Fixed Equipment—Specific. Exposed, noncurrent-carrying metal parts of the following kinds of equipment, regardless of voltage, shall be grounded: (a) Frames of motors as specified in Section 430-142; (b) Controller cases for motors,except lined covers of snap switches; (c) Electric equipment of elevators and cranes; (d) Electric equipment in garages, theaters and motion picture stu- dios, except pendant lampholders on circuits of not more than 150 volts to ground; (e) Motion-picture projection equipment; (f) Electric signs and associated equipment, unless these are inacces- sible to unauthorized persons and are also insulated from ground and from other conductive objects; (g) Generator and motor frames in an electrically operated organ, unless the generator is effectively insulated both from ground and from the motor driving it; (h) Switchboard frames and structures supporting switching equip- ment, except that frames of direct-current, single-polarity switchboards need not be grounded where effectively insulated; (i) Equipment supplied by Class 1 and Class 2 remote control and signaling circuits where Part B of this article requires those circuits to be grounded. 250-44. Nonelectrical Equipment. The following metal parts shall be grounded: (a) Frames and tracks of electrically operated cranes; (b) The metal frame of a nonelectrically driven elevator car to which electric conductors are attached; (c) Hand-operated metal shifting ropes or cables of electric elevators; (d) Metal enclosures such as partitions, grill work, etc., around equipment carrying voltages in excess of 750 volts between conductors, unless in substations or vaults under the sole control of the supply com- pany. ARTICLE 250—GROUNDING 70-67 Where extensive metal in or on buildings may become energized and is subject to personal contact, adequate bonding and grounding will provide additional safety. 250-45. Equipment Connected by Cord and Plug. Under any of the following conditions, exposed noncurrent-carrying metal parts of cord and plug connected equipment, which are liable to become energized, shall be grounded: (a) In hazardous locations (see Articles 500 to 517); (b) When operated at more than 150 volts to ground,except: (1) Motors,where guarded; (2) Metal frames of electrically heated appliances exempted by Section 422-16. (c) In residential occupancies, (1) refrigerators, freezers, air condi- tioners, and (2) clothes-washing, clothes-drying and dish-washing ma- chines, sump pumps and (3) portable, hand held, motor operated tools and appliances of the following types: drills,hedge clippers, lawn mow- ers,wet scrubbers,sanders and saws. Exception: Portable tools and appliances covered by Section 250-45(c) (3), protected by an approved system of double insulation, or its equivalent, need not be grounded. Where such an approved system is employed the equipment shall be distinctively marked. Portable tools or appliances not provided with special insulating or grounding protection are not intended to be used in damp, wet or conductive locations. (d) In other than residential occupancies, (1) refrigerators, freezers, air conditioners, and (2) clothes-washing,clothes-drying and dish-wash- ing machines,sump pumps and (3) portable,hand held,motor operated tools and appliances of the following types: drills, hedge clippers, lawn mowers, wet scrubbers, sanders and saws, and (4) cord and plug con- nected appliances used in damp or wet locations, or by persons standing on the ground or on metal floors or working inside of metal tanks or boilers, and (5) portable tools which are likely to be used in wet and conductive locations. Exception No. 1: Portable tools which are likely to be used in wet and conductive locations need not be grounded where supplied through an insulating transformer with ungrounded secondary of not over 50 volts. Exception No. 2: Portable tools covered by Sections 250-45(d) (3), (4) and (5) and appliances covered by Section 250-45(d) (3), pro- tected by an approved system of double insulation, or its equivalent, need not be grounded. Where such an approved system is employed, the equipment shall be distinctively marked. Where conditions of mainte- nance and supervision assure that proper grounding of tools or appli- ances will be maintained (as, for example, on some factory production lines) it is recommended that grounded type tools and appliances be used. It is recommended that the frames of all portable motors which operate at more than 50 volts to ground be grounded. 70-68 NATIONAL ELECTRICAL CODE 250-46. Spacing from Lightning Rods. Metal frames and enclosures of electric equipment shall, wherever practicable, be kept at least 6 feet away from lightning rod conductors. Where it is not practicable to se- cure 6 feet separation, they shall be bonded together. See Sections 250- 34 and 250-86. F. Methods of Grounding 250-51. Effective Grounding. The path to ground from circuits, equip- ment, and conductor enclosures shall (1) be permanent and continu- ous and (2) shall have ample carrying capacity to conduct safely any currents liable to be imposed on it, and (3) shall have impedance sufficiently low to limit the potential above ground and to facilitate the operation of the overcurrent devices in the circuit. 250-52. Location of System Ground Connection. The grounding con- ductor may be connected to the grounded conductor of the wiring sys- tem at any convenient point on the premises on the supply side of the service disconnecting means. It is recommended that high capacity services have the grounding con- ductor connected to the grounded conductor of the system within the serv- ice entrance equipment enclosure. 250-53. Common Use of Grounding Conductor. The grounding con- ductor of a wiring system shall also be used for grounding equipment, conduit and other metal raceways or enclosures for conductors, includ- ing service conduit or cable sheath and service equipment. Exception: The grounding connection as covered in the exception in Section 210-7 may be made to a grounded cold water pipe near the equipment. 250-54. Common Grounding Electrode. Where the alternating-current system is connected to a grounding electrode in or at a building as specified in Sections 250-23 and 250-24, the same electrode shall be used to ground conductor enclosures and equipment in or on that building. 250-55. Underground Service Cable. Where served from a continu- ous underground metal-sheathed cable system, the sheath or armor of underground service cable metallically connected to the underground system, or underground service conduit containing a metal-sheathed cable bonded to the underground system, need not be grounded at the building and may be insulated from the interior conduit or piping. 250-56. Short Sections of Raceway. Isolated sections of metal race- way or cable armor, where required to be grounded, shall preferably be grounded by connecting to other grounded raceway or armor, but may be grounded in accordance with Section 250-57. 250-57. Fixed Equipment. (a) Metal boxes, cabinets and fittings, or noncurrent-carrying metal parts of other fixed equipment where metallically connected to grounded flexible metal raceways and fittings both approved for grounding pur- poses; the grounded armor of Types AC, ALS, and MI cables; or grounded rigid metal raceways are considered to be grounded by such connections. ARTICLE 250—GROUNDING 70-69 (b) They may also be grounded in one of the following ways: (1) By a grounding conductor run with circuit conductors; this conductor may be uninsulated, but where it is provided with an indi- vidual covering, the covering shall be finished a continuous green color or a continuous green color with one or more yellow stripes. (2) By a grounding conductor in the supply cord, when cord con- nected as permitted in Section 400-3; (3) By special permission, other means for grounding fixed equip- ment may be used. 250-58. Equipment on Structural Metal. (a) Electric equipment secured to and in contact with the grounded structural metal frame of a building,shall be deemed to be grounded. (b) Metal car frames supported by metal hoisting cables attached to or running over sheaves or drums of elevator machines shall be deemed to be grounded where the machine is grounded in accordance with this Code. 250-59. Portable and/or Cord and Plug-Connected Equipment. The non-current carrying metal parts of cord and plug-connected equipment required to be grounded may be grounded in any one of the following ways: (a) By means of the metal enclosure of the conductors feeding such equipment, provided an approved grounding-type attachment plug is used, one fixed contacting member being for the purpose of grounding the metal enclosure, and provided, further, that the metal enclosure of the conductors is attached to the attachment plug and to the equipment by connectors approved for the purpose; Exception: The grounding contacting member of grounding type at- tachment plugs on the power supply cord of portable hand-held, hand- guided or hand-supported tools or appliances may be of the movable self-restoring type. Attachment plug caps are not intended to be used as terminations for metal-clad cable or flexible metal conduit. (b) By means of a grounding conductor run with the power supply conductors in a cable assembly or flexible cord that is properly termi- nated in an approved grounding-type attachment plug having a fixed grounding contacting member. The grounding conductor in a cable as- sembly may be uninsulated; but where an individual covering is pro- vided for such conductors it shall be finished a continuous green color or a continuous green color with one or more yellow stripes. Exception: The grounding contacting member of grounding type at- tachment plugs on the power supply cord of portable tools or portable appliances may be of the movable self-restoring type. (c) A separate flexible wire or strap, insulated or bare, protected as well as practicable against physical damage may be used only by spe- cial permission except where a part of an approved portable equip- ment. 250-60. Frames of Electric Ranges and Electric Clothes Dryers. Frames of electric ranges and electric clothes dryers shall be grounded by any of 70-70 NATIONAL ELECTRICAL CODE the means provided for in Sections 250-57 and 250-59;or, where served by a 120/240 volt, single phase, three-wire circuit or a 120/208 volt circuit derived from a three-phase, four-wire supply, they may be grounded by connection to the grounded circuit conductors, provided the grounded circuit conductors are not smaller than No. 10 AWG. Where service-entrance cable having an uninsulated neutral conductor is used, the branch circuit shall originate at the service-entrance equip- ment.The frames of wall-mounted ovens and counter-mounted cooking units shall be grounded and may be grounded in the same manner as electric ranges. Grounding contacts of receptacles furnished as a part of equipment grounded to the neutral circuit conductor shall be bonded to the equipment which is so grounded. It is recommended that all branch circuits supplying equipment which is grounded to the grounded circuit conductor originate at the service equip- ment. 250-61. Grounding Equipment to Circuit Conductor. The grounded service conductor on the supply side of the service disconnecting means may be used for grounding meter housing and service equipment and metallic enclosures and guards. The grounded circuit conductor on the load side of the service disconnecting means shall not be used for grounding equipment, cable armor, or metal raceways except as pro- vided in Section 250-57 (b) (4),and in Section 250-60. G. Bonding 250-71. Bonding at Service Equipment. The electrical continuity of the grounding circuit for the following equipment and enclosures shall be assured by one of the means given in Section 250-72. (a) The service raceways or service cable armor or sheath, except as provided in Section 230-63(b) and Section 250-55; (b) All service equipment enclosures containing service entrance conductors, including meter fittings, boxes or the like, interposed in the service raceway or armor; (c) Any conduit or armor which forms part of the grounding con- ductor to the service raceway. 250-72. Continuity at Service Equipment. Electrical continuity at service equipment shall be assured by one of the following means: (a) Bonding equipment to the grounded service conductor in a man- ner provided in Section 250-113. (b) Threaded couplings and threaded bosses on enclosures with joints shall be made up wrenchtight where rigid conduit is involved. (c) Threadless couplings made up tight for rigid metal conduit and electrical metallic tubing. (d) Bonding jumpers meeting the other requirements of this article. Bonding jumpers shall be used around concentric or eccentric knock- outs which are punched or otherwise formed so as to impair the elec- trical connection to ground. (e) Other devices (not locknuts and bushings) approved for the purpose. ARTICLE 250—GROUNDING 70-71 250-73. Metal Armor or Tape of Service Cable. With service cable having an uninsulated grounded service conductor in continuous elec- trical contact with its metallic armor or tape, the metal covering is con- sidered to be adequately grounded. 250-74. Bonding at Grounding-Type Receptacles. Grounding continu- ity between a grounded outlet box and the grounding circuit of the re- ceptacle shall be established by means of a bonding jumper between the outlet box and the receptacle grounding terminal. Exception No. 1: When the box is surface-mounted, direct metal-to- metal contact between the device yoke and the box may be used to establish the grounding circuit. Exception No.2:Contact devices or yokes designed and approved for the purpose may be used in conjunction with the supporting screws to establish the grounding circuit between the device yoke and flush-type boxes installed in walls. 250-75. Continuity at Other Enclosures. The electrical continuity of metallic raceway systems and cable armor that are to serve as ground- ing conductors shall be assured. At points where raceway or armor connects to metal enclosures, any nonconducting coating which might interrupt such continuity shall be removed unless fittings are used which are so designed that such removal is unnecessary. 250-76. Voltages Exceeding 250 Volts. The electrical continuity of metal raceway or metal sheathed cable which contains any conductor other than service entrance conductors of more than 250 volts to ground shall be assured by one of the methods specified in Sections 250- 72(b), (c), (d),and (e),or by one of the following methods: (a) Threadless fittings, made up tight, with conduit or metal-clad cable; (b) Two locknuts,one inside and one outside of boxes and cabinets. 250-77. Loosely Jointed Metal Raceways. Expansion joints and tele- scoping sections of raceways shall be made electrically continuous by bonding jumpers or other approved means. Metal trough raceways used in connection with sound recording and reproducing, made up in sections, shall contain a grounding conductor to which each section shall be bonded. 250-78. Hazardous Locations. In hazardous locations, regardless of the voltage involved, the electrical continuity of metallic raceway, boxes and the like, shall be assured by one of the methods specified in Sections 250-72(b), (c), (d),and (e). 250-79. Bonding Jumpers. Bonding jumpers shall conform to the following: (a) Material and Size. Bonding jumpers shall be of copper or other corrosion-resistant material. The size shall be as required by Section 250-94 for services and as required by Section 250-95 for raceways and equipment on the load side of the service protective equipment. (b) Attachment. Bonding jumpers shall be attached to cabinets and the like in a manner provided in Section 250-113; where used between 70-72 NATIONAL ELECTRICAL CODE grounding electrodes or around water meters and the like, they shall be attached in a manner provided for in Section 250-115. H. Grounding Electrodes 250-81. Water Pipe. A metallic underground water piping system, either local or supplying a community, shall always be used as the grounding electrode where such a piping system is available.Where the buried portion of the metallic piping system is less than ten feet (in- cluding well casings bonded to the piping system) or there is some likelihood of the piping system being disconnected or isolated through the use of nonmetallic piping or insulated couplings, the piping system shall be supplemented by one or more of the grounding electrodes rec- ognized in Sections 250-82 and 250-83. The interior metallic cold wa- ter piping system shall always be bonded to the one or more grounding electrodes. Expanding use of nonmetallic piping for water systems and insulating couplings on metallic water systems makes it more important that water piping within a building be adequately grounded without depending on con- nections to an outside piping system. The interior piping system should be electrically continuous. Bonding to gas, sewer, hot water piping and metallic air ducts within the premises will provide additional safety. 250-82. Other Available Electrodes. Where a water system as de- scribed in Section 250-81 is not available, the grounding connection may be made to any of the following: (a) The metal frame of the building,where effectively grounded. (b) Where permitted, a continuous metallic underground gas piping system. Underground gas service piping shall not be used as a ground- ing electrode except when it is electrically continuous uncoated metallic piping and its use as a grounding electrode is acceptable both to the serving gas supplier and to the authority having jurisdiction, since gas piping systems are often constructed with insulating bushings or joints, or are of coated or nonmetallic piping. (c) Other local metallic underground systems, such as piping, tanks, and the like. 250-83. Made Electrodes. Where electrodes described in Sections 250- 81 and 250-82 are not available, the grounding electrode shall consist of a driven pipe, driven rod, buried plate or other device approved for the purpose and conforming to the following requirements: (a) Concrete Encased Electrodes. Not less than twenty feet of bare copper conductor of a size specified in Table 250-94(a), and in no case smaller than No. 4, encased along the bottom of a concrete foundation footing which is in direct contact with the earth. (b) Plate Electrodes. Each plate electrode shall present not less than 2 square feet of surface to exterior soil. Electrodes of iron, or steel plates shall be at least 1/4 inch in thickness. Electrodes of nonferrous metal shall be at least 0.06 inch in thickness. (c) Pipe Electrodes. Electrodes of pipe or conduit shall be not smaller than of the 3/4-inch trade size and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corro- sion protection. (d) Rod Electrodes. Electrodes of rods of steel or iron shall be at ARTICLE 250—GROUNDING 70-73 least 5/a inch in diameter. Approved rods of nonferrous materials or their approved equivalent used for electrodes shall be not less than i/2 inch in diameter. (e) Installation. Electrodes should, as far as practicable, be im- bedded below permanent moisture level. Except where rock bottom is encountered, pipes or rods shall be driven to a depth of at least 8 feet regardless of size or number of electrodes used. Pipes or rods when less than standard commercial length shall preferably be of one piece. Such pipes or rods shall have clean metal surfaces and shall not be covered with paint, enamel or other poorly conducting materials. Where rock bottom is encountered at a depth of less than 4 feet, electrodes shall be buried in a horizontal trench, and where pipes or rods are used as the electrode they shall comply with Section 250-83(b and c) and shall not be less than 8 feet in length. Each electrode shall be separated at least 6 feet from any other electrode, including those used for signal circuits, radio,lightning rods,or any other purpose. 250-84. Resistance. Made electrodes shall, where practicable, have a resistance to ground not to exceed 25 ohms. Where the resistance is not as low as 25 ohms, two or more electrodes connected in parallel shall be used. Continuous metallic underground water or gas piping systems in general have a resistance to ground of less than 3 ohms. Metal frames of buildings and local metallic underground piping systems, metal well casings, and the like, have, in general, a resistance substantially below 25 ohms. It is recom- mended that in locations where it is necessary to use made electrodes for grounding interior wiring systems, additional grounds, such as connections to a system ground conductor be placed on the distribution circuit. It is also recommended that single electrode grounds when installed, and periodically afterwards,be tested for resistance. 250-85. Railway Tracks. Rails or other grounded conductors of elec- tric railway circuits shall not be used (a) as a ground for other than railway lightning arresters and railway equipment, conduit, armored cable, metal raceway, and the like, where other effective grounds are available; and (b) in no case shall such rails or other grounded con- ductors of railway circuits be used for grounding interior wiring sys- tems other than those supplied from the railway circuit itself. 250-86. Use of Lightning Rods. Lightning rod conductors and driven pipes, rods or other made electrodes used for grounding lightning rods, shall not be used in lieu of the made grounding electrodes required by this Article for grounding wiring systems and equipment. The forego- ing provision shall not be taken to forbid the bonding together of the several made electrodes that are respectively provided for electric wir- ing systems and equipment, for communication systems, and for light- ning protection.See Section 800-31(b)(5). It is recommended that all separate electrodes be bonded together to limit potential differences between them and between their associated wiring sys- tems. J. Grounding Conductors 250-91. Material. The material for the grounding conductors shall be as follows: (a) For System or Common Grounding Conductor. The grounding conductor of a wiring system shall be of copper or other corrosion- 70-74 NATIONAL ELECTRICAL CODE resistant material.The conductor may be solid or stranded, insulated or bare. Except in cases of bus-bars, the grounding conductor shall be without joint or splice throughout its length. Where the grounding conductor is not of copper, its electrical resistance per linear foot shall not exceed that of the allowable copper conductor for such a purpose. (b) For Conductor Enclosures and Equipment Only. The grounding conductor for equipment and for conduit and other metal raceways or enclosures for conductors, may be a conductor of copper or other corrosion-resistant material, stranded or solid, insulated or bare, a bus- bar or a rigid metal conduit, electrical metallic tubing or flexible metal conduit and fittings both approved for grounding purposes, the armor of Type AC metal-clad cable, Types MI or ALS cable. Under conditions favorable to corrosion, a suitable corrosion-resistant material shall be used. All bolted and threaded connections at joints and fittings shall be made tight by the use of suitable tools. 250-92. Installation. Grounding conductors shall be installed as fol- lows: (a) System or Common Grounding Conductor. A grounding con- ductor, No. 4 or larger, may be attached to the surface on which it is carried without the use of knobs, tubes or insulators. It need not have protection unless exposed to severe physical damage. A No. 6 ground- ing conductor, which is free from exposure to physical damage, may be run along the surface of the building construction without metal cov- ering or protection,where it is rigidly stapled to the construction;other- wise, it shall be in conduit, electrical metallic tubing or cable armor. Grounding conductors smaller than No. 6 shall be in conduit, electrical metallic tubing or cable armor. Metallic enclosures for grounding con- ductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode, and shall be securely fastened to the ground clamp or fitting. Metallic enclosures which are not physically continuous from cabinet or equipment to the ground- ing electrode can be made electrically continuous by bonding each end to the grounding conductor. Where rigid metallic conduit or steel pipe is used as protection for a grounding conductor, the installation shall comply with the requirement of Article 346; where electrical metallic tubing is used, the installation shall comply with the requirements of Article 348. Aluminum grounding conductors shall not be used where in direct contact with masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum grounding conductors shall not be installed within 18 inches of the earth. (b) Conductor Enclosures and Equipment Only. A grounding con- ductor for conductor enclosures and equipment only shall meet the re- quirements of Section 250-92 (a), except that where smaller than No. 6, as permitted by Section 250-95, it need not be armored or in- stalled in a raceway where run through the hollow spaces of a wall or partition or otherwise run so as to be not subject to physical damage. 250-93. Direct Current Systems. The ampacity of the grounding con- ductor for a direct-current supply system or generator shall be not less than that of the largest conductor supplied by the system, except that where the grounded circuit conductor is a neutral derived from a bal- ARTICLE 250—GROUNDING 70-75 ancer winding or a balancer set protected in accordance with require- ments of Section 445-4(d), the size of the grounding conductor shall not be less than that of the neutral conductor. The grounding conduc- tor shall in no case be smaller than No. 8 copper. 250-94. Alternating Current Systems. (a) Service and Common Grounding Conductor for Grounded Systems. Where the wiring system is grounded, the size of the grounding con- ductor for an alternating current system or for a common grounding conductor shall not be less than is given in Table 250-94.(a), except that where connected to made electrodes (as in Section 250-83), that portion of the grounding conductor which is the sole connection be- tween the grounding electrode and the grounded system conductor need not be larger than No.6 copper wire or its equivalent in ampacity. (b) Service Equipment Grounding Conductor for Ungrounded Systems. Where the wiring system is ungrounded, the size of a grounding con- ductor for a service raceway, for the metal sheath or armor of a service cable, and for service equipment shall not be less than is given in Table 250-94.(b), except that where connected to made electrodes (as in Sec- tion 250-83) that portion of the grounding conductor which is the sole connection between the grounding electrode and the service equipment need not be larger than No. 6 copper wire or its equivalent in ampacity. 250-95. Size of Equipment Grounding Conductors. The size of copper or aluminum equipment grounding conductors shall be not less than given in Table 250-95. For permissible use of the enclosing raceway see Sections 250-57(a) and 250-91(b). Exception:A conductor not smaller than No. 18 AWG copper which is part of an approved cord assembly may be used to ground cord con- nected equipment protected at not more than 20 amperes. Table 250-94(a) Service and Common Main Grounding Conductor for Grounded Systems Size of Largest Service Conductor or Size of Grounding Equivalent for Multiple Conductors Conductor Copper Aluminum Copper Aluminum* 2 or smaller 0 or smaller 8 6 1 or 0 2/0 or 3/0 6 4 2/0 or 3/0 4/0 or 250 MCM 4 2 Over 3/0 to Over 250 MCM 2 0 350 MCM to 500 MCM Over 350 MCM Over 500 MCM 0 3/0 to 600 MCM to 900 MCM Over 600 MCM Over 900 MCM 2/0 4/0 to 1100 MCM to 1750 MCM Over 1100 MCM Over 1750 MCM 3/0 250 MCM *See installation restrictions in Section 250-92(a). See Section 250-23 (b). 70-76 NATIONAL ELECTRICAL CODE Table 250-94(b) Service Equipment Grounding Conductor for Ungrounded Systems Size of Largest Service Conductor or Size of Grounding Equivalent for Multiple Conductors Conductor Elec- trical Con- Metal- duit lic Cop- Alumi- or Tub- Copper Aluminum per num Pipe ing 2 or smaller 0 or smaller 8 6 1/2 1/2 1 or 0 2/0 or 3/0 6 4 1/2 1 2/0 or 3/0 4/0 or 250 MCM 4 2 3/4 11/4 Over 3/0 to Over 250 MCM 2 0 3/4 11/4 350 MCM to 500 MCM Over 350 MCM Over 500 MCM 0 3/0 1 2 to 600 MCM to 900 MCM Over 600 MCM Over 900 MCM 2/0 4/0 1 2 to 1100 MCM to 1750 MCM Over 1100 MCM Over 1750 MCM 3/0 250 MCM 1 2 250-97. Outline Lighting. Isolated noncurrent-carrying metal parts of outline lighting systems may be bonded together by a No. 14 conductor protected from physical damage, where a conductor complying with Section 250-95 is used to ground the group. 250-98. Common Raceway. A grounding conductor may be run in the same metal raceway with other conductors of the system to which it is connected. 250-99. Continuity. No automatic cutout or switch shall be placed in the grounding conductor of an interior wiring system unless the open- ing of the cutout or switch disconnects all sources of energy. K. Grounding Conductor Connections 250-111. To Raceway or Cable Armor. The point of connection of the grounding conductor to interior metal raceways, cable armor and the like shall be as near as practicable to the source of supply and shall be so chosen that no raceway or cable armor is grounded through a run of smaller size than is called for in Section 250-95. 250-112. To Electrode. The grounding connection to the electrode shall be located as follows: (a) To Water Pipes. System or common grounding conductors shall be attached to a water piping system on the street side of the water me- ter or on a cold water pipe as near as practicable to the water service entrance to the building. Where the source of the water supply is from ARTICLE 250—GROUNDING 70-77 Table 250-95. Size of Equipment Grounding Conductors for Grounding Interior Raceway and Equipment Rating or Setting of Automatic Overcurrent Size Device in Circuit Ahead of Equipment,Conduit, Copper Aluminum etc.,Not Exceeding Wire No. Wire No.* (Amperes) 15 14 12 20 12 10 30 10 8 40 10 8 60 10 8 100 8 6 200 6 4 400 3 1 600 1 2/0 800 0 3/0 1000 2/0 4/0 1200 3/0 250 MCM 1600 4/0 350 " 2000 250 MCM 400 " 2500 350 " 500 3000 400 " 600 " 4000 500 " 800 " 5000 700 " 1000 " 6000 800 " 1200 " See installation restrictions in Section 250-92(a). a driven well in the basement of the premises, the connection shall be made as near as practicable to the well. Where practicable, the point of attachment shall be accessible. Where the point of attachment is not on the street side of the water meter, the water piping system shall be made electrically continuous by bonding together all parts between the at- tachment and the street side of the water meter or the pipe entrance which contain insulating sections or are liable to become disconnected, as at meters,valves and service unions. (b) To Gas Pipes. The point of attachment of a grounding conduc- tor to gas piping where permitted under Section 250-82, shall always be on the street side of the gas meter, and shall be accessible where practicable. (c) To Other Electrodes. The grounding conductor shall be attached to other electrodes permitted in Sections 250-82 and 250-83 at a point which will assure a permanent ground. Where practicable the point of attachment shall be accessible. 250-113. Attachment to Circuits and Equipment. The grounding con- ductor, bond, or bonding jumper shall be attached to circuits, conduits, 70-78 NATIONAL ELECTRICAL CODE cabinets, equipment, and the like, which are to be grounded, by means of suitable lugs,pressure connectors, clamps, or other approved means, except that connections which depend upon solder shall not be used. 250-114. Continuity and Attachment of Branch Circuit Grounding Con- ductors to Boxes. Where more than one grounding conductor of a branch circuit enters a box, all such conductors shall be in good elec- trical contact with each other and the arrangement shall be such that the disconnection or removal of a receptacle, fixture, or other device fed from the box will not interfere with or interrupt the grounding continuity. (a) Metallic Boxes. A connection shall be made between the one or more grounding conductors and a metallic box by means of a grounding screw which shall be used for no other purpose, or an ap- proved grounding device. (b) Nonmetallic Boxes. One or more grounding conductors brought into a nonmetallic outlet box shall be so arranged that a connection can be made to any fitting or device in that box which requires grounding. 250-115. Attachment to Electrodes. The grounding conductor shall be attached to the grounding electrode by means of (1) an approved bolted clamp of cast bronze or brass or of plain or malleable cast iron, or (2) a pipe fitting, plug, or other approved device, screwed into the pipe or into the fitting, or (3) other equally substantial approved means. The grounding conductor shall be attached to the grounding fitting by means of suitable lugs, pressure connectors, clamps, or other approved means, except that connections which depend upon solder shall not be used. Not more than one conductor shall be connected to the grounding electrode by a single clamp or fitting,unless the clamp or fitting is of a type approved for such use. 250-116. Ground Clamps. For the grounding conductor of a wiring system the sheet-metal-strap type of ground clamp is not considered adequate unless the strap is attached to a rigid metal base which, when installed, is seated on the water pipe, or other electrode and the strap is of such material and dimensions that it is not liable to stretch during or after installation. Ground clamps for use on copper water tubing and copper, brass, or lead pipe should preferably be of copper, and those for use on galvanized or iron pipe should preferably be of galvanized iron and so designed as to avoid physical damage to pipe. Ground clamps used with aluminum ground- ing conductors should be approved for the purpose. 250-117. Protection of Attachment. Ground clamps or other fittings, unless approved for general use without protection, shall be protected from ordinary physical damage (1) by being placed where they are not liable to be damaged or (2) by being enclosed in metal, wood, or equivalent protective covering. 250-118. Clean Surfaces. Where a nonconductive protective coating, such as paint or enamel, is used on the equipment, conduit, couplings or fittings, such coating shall be removed from threads and other con- tact surfaces in order to insure a good electrical connection. ARTICLE 250—GROUNDING 70-79 L. Instrument Transformers,Relays,etc. 250-121. Instrument Transformer Circuits. The secondary circuits of current and potential instrument transformers shall be grounded where the primary windings are connected to circuits of 300 volts or more to ground, and where on switchboards, shall be grounded irrespective of voltage, except that such circuits need not be grounded where the primary windings are connected to circuits of 750 volts or less and no live parts or wiring are exposed or accessible to other than qualified persons. 250-122. Instrument Transformer Cases. Cases or frames of instru- ment transformers shall be grounded where accessible to other than qualified persons, except that cases or frames of current transformers, the primaries of which are not over 150 volts to ground and which are used exclusively to supply current to meters,need not be grounded. 250-123. Cases of Instruments, Meters and Relays—Operating Voltage 750 or Less. Instruments, meters and relays which operate with windings or working parts at 750 volts or less shall be grounded as fol- lows: (a) Not on Switchboards. Instruments, meters, and relays not lo- cated on switchboards, which operate with windings or working parts at 300 volts or more to ground, and accessible to other than qualified persons,shall have the cases and other exposed metal parts grounded; (b) On Dead Front Switchboards. Instruments, meters and relays (whether operated from current and potential transformers, or con- nected directly in the circuit) on switchboards having no live parts on the front of the panels shall have the cases grounded; (c) On Live Front Switchboards. Instruments, meters and relays (whether operated from current and potential transformers, or con- nected directly in the circuit) on switchboards having exposed live parts on the front of panels shall not have their cases grounded. Mats of in- sulating rubber or other suitable floor insulation, shall be provided for the operator where the voltage to ground exceeds 150. 250-124. Cases of Instruments, Meters and Relays—Operating Voltage Over 750. Where instruments, meters and relays have current-carry- ing parts over 750 volts to ground, they shall be isolated by elevation or protected by suitable barriers, grounded metal or insulating covers or guards.Their cases shall not be grounded,except as follows: (a) In electrostatic ground detectors the internal ground segments of the instrument are connected to the instrument case and grounded; the ground detector shall be isolated by elevation. 250-125. Instrument Grounding Conductor. The grounding conductor for secondary circuits of instrument transformers and for instrument cases shall not be smaller than No. 12 where of copper, or where of other metal shall have equal conductance. Cases of instrument trans- formers, instruments, meters and relays which are mounted directly on grounded metal surfaces of enclosures or grounded metal switchboard panels shall be considered to be grounded and no additional grounding conductor will be required. 70-80 NATIONAL ELECTRICAL CODE M. Lightning Arresters 250-131. On Secondary Services, 750 Volts or Less. Where a lightning arrester is installed on a secondary service, the connections to the serv- ice conductors and to grounding conductor shall be as short as prac- ticable. The grounding conductor may be (1) the grounded service conductor, or (2) the common grounding conductor, or (3) the serv- ice equipment grounding conductor. The bonding or grounding con- ductor shall be of copper not smaller than No. 14 or of equivalent corrosion-resistant material. 250-132. On Primary Circuits. The grounding conductor of a lightning arrester protecting a transformer which supplies a secondary distribu- tion system may be interconnected as follows: (a) Metallic Interconnection. A metallic interconnection may be made to the secondary neutral provided that, in addition to the direct grounding connection at the arrester: (1) The grounded conductor of the secondary has elsewhere a grounding connection to a continuous metallic underground water piping system. However, in urban waterpipe areas where there are at least four waterpipe connections on the neutral and not less than four such connections in each mile of neutral, the metallic interconnection may be made to the secondary neutral with omission of the direct grounding connection at the arrester. (2) The grounded conductor of the secondary system is part of a multigrounded neutral system, of which the primary neutral has at least four ground connections in each mile of line in addition to a ground at each service. (b) Through Spark Gap. Where the secondary is not grounded as in Section 250-132(a), but is otherwise grounded as in Sections 250- 82 and 250-83, such interconnection, where made, shall be through a spark gap having a 60-cycle breakdown voltage of at least twice the primary circuit voltage but not necessarily more than 10 kv, and there shall be at least one other ground on the grounded conductor of the secondary not less than 20 feet distant from the lightning arrester grounding electrode. (c) By Special Permission. Except as above provided, intercon- nection of the arrester ground and the secondary neutral may be made only by special permission. ARTICLE 280—LIGHTNING ARRESTERS A. Industrial Stations 280-1. Where Required. Lightning arresters shall be provided in in- dustrial stations in locations where thunderstorms are frequent and adequate protection against lightning is not otherwise provided. For lightning arresters in hazardous locations,see Articles 500-517. 280-2. Number Required. A lightning arrester shall be connected to each ungrounded overhead conductor entering or leaving the station, ARTICLE 280—LIGHTNING ARRESTERS 70-81 except that where there is more than one circuit, a single set of arresters may be installed on the station bus where means are provided to pro- tect circuits that may remain disconnected from the bus. 280-3. Where Connected. The arrester shall be connected on the line side of all connected station apparatus. B. Other Occupancies 280-11. Utilization Equipment. Lightning arresters installed for the protection of utilization equipment may be installed either inside or outside the building or enclosure containing the equipment to be pro- tected. Arresters, unless isolated by elevation or made otherwise inac- cessible to unqualified persons, shall be enclosed, and where the operat- ing voltage of the circuit exceeds 750 volts between conductors they shall be inaccessible to unqualified persons. Secondary lightning protection devices may reduce damage to wiring and equipment caused by lightning disturbances. (See Section 502-3.) C. General 280-21. Location—Indoors. Arresters installed indoors shall be located well away from other equipment, passageways and combustible parts of buildings, and where containing oil shall be separated from other equipment by walls meeting the requirements of Section 450-42. 280-22. Location—Outdoors. Where arresters containing oil are lo- cated outdoors, provision shall be made to drain away any accumula- tion of oil. Oil may be drained away by ditches and drains or the oil may be absorbed and danger of spreading removed by paving the yard with cinders or other absorbent material to a depth of several inches. 280-23. Connectors—Size and Material. The connections between the arrester and the line wire or bus, and between arrester and ground shall be of copper wire or cable or the equivalent, and, except as provided on secondary services in Section 250-131, shall not be smaller than No. 6, and shall be made as short and as straight as practicable, avoiding as far as possible all bends and turns,especially sharp bends. 280-24. Insulation. Lightning-protection accessories such as gap electrodes, and choke coils where used, shall have an insulation from ground or from other conductors at least equal to the insulation re- quired at other points of the circuit. 280-25. Switch for Isolating Arrester. Where isolating switches or dis- connecting devices are used, they shall withstand, in full open position, a voltage test between live parts 10 per cent in excess of the maximum voltage test they will withstand to ground. 280-26. Grounding. Lightning arresters shall be grounded in the man- ner prescribed in Article 250, except that grounding conductors shall not be run in metallic enclosures unless bonded to both ends of such enclosures. 70-82 Chapter 3. Wiring Methods and Materials ARTICLE 300—WIRING METHODS—GENERAL REQUIREMENTS 300-1. Scope. (a) The provisions of Chapter 3 apply to the electrical and mechani- cal requirements for the various methods of installing fixed electrical I) conductors for electric light,heat,power, and certain signal systems. (b) The provisions of this Article shall apply to all wiring installa- tions, except for remote-control, including low voltage relay switching, low-energy power and signal systems as provided in Article 725, and communication systems as provided in Article 800. (c) On premises where a continuous underground metallic water- piping network system is not available as a grounding electrode, and where it is not practicable otherwise to secure a ground of permanently low resistance, the use of a wiring method which does not employ metal enclosures for the wires is recommended, unless the character or occupancy of the building is such as to require the use of a metal-en- closed wiring system. (d) The provisions of this Article are not intended to apply to the conductors which form an integral part of equipment such as motors, motor controllers and the like. 300-2. Voltage Limitations. Wiring methods specified in Chapter 3 may be used for voltages not exceeding 600, unless specifically limited in some Article of Chapter 3. They may be used for voltages over 600 where specifically permitted elsewhere in this code. 300-3. Conductors of Different Systems. (a) Conductors of light and power systems of 600 volts or less may occupy the same enclosure, without regard to whether the individual circuits are alternating-current or direct-current, only where all con- ductors are insulated for the maximum voltage of any conductor within the enclosure. (b) Conductors of light and power systems of over 600 volts shall not occupy the same enclosure with conductors of light and power systems of 600 volts or less. (c) Secondary wiring to electric discharge lamps of 1,000 volts or less, insulated for the secondary voltage involved, may occupy the same fixture enclosure as the branch circuit conductors. (d) Primary leads of electric discharge lamp ballasts, insulated for the primary voltage of the ballast, when contained within the individual wiring enclosure may occupy the same fixture enclosure as the branch circuit conductors. ARTICLE 300—WIRING METHODS—GENERAL 70-83 (e) Excitation, control, relay and ammeter conductors used in con- nection with any individual motor or starter may occupy the same en- closure as the motor circuit conductors. (f) Conductors of signal or radio systems shall not occupy the same enclosure with conductors of light or power systems except as permit- ted for elevators in Section 620-36; for sound recording in Section 640-6; for remote-control, low-energy power and signal circuits in Sections 725-16 and 725-42; and communication system in Sections 800-3 and 800-21. 300-4. Protection Against Physical Damage. Where subject to physical damage,conductors shall be adequately protected. 300-5. Protection Against Corrosion. Metal raceways, cable armor, boxes,cable sheathing,cabinets,metallic elbows,couplings,fittings, sup- ports and support hardware shall be of materials suitable for the en- vironment in which they are to be installed. (a) Ferrous raceways, cable armor, boxes, cable sheathing, cabinets, metallic elbows, couplings,fittings,supports and support hardware shall be suitably protected against corrosion inside and outside (except threads at joints) by a coating of approved corrosion resistant material such as zinc, cadmium, or enamel. Where protected from corrosion solely by enamel,they shall not be used out of doors or in wet locations as described in (c) below. When boxes or cabinets have an approved system of organic coatings and are marked "Raintight" or "Outdoor Type"they may be used out of doors. (b) Unless made of materials judged suitable for the condition, or unless corrosion protection approved for the condition is provided, fer- rous or non-ferrous metallic raceways, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports and support hardware shall not be installed in concrete or in direct contact with the earth,or in areas subject to severe corrosive influences. (c) In portions of dairies, laundries, canneries, and other indoor wet locations, and in locations where walls are frequently washed or where there are surfaces of absorbent materials, such as damp paper or wood, the entire wiring system, including all boxes, fittings, conduits and cable used therewith, shall be mounted so that there is at least one- quarter inch air space between it and the wall or supporting surface. Meat-packing plants, tanneries, hide cellars, casing rooms, glue houses, fertilizer rooms, salt storage, some chemical works, metal refineries, pulp mills, sugar mills, round houses, some stables, and similar locations are judged to be occupancies where severe corrosive conditions are likely to be present. 300-6. Raceways Exposed to Different Temperatures. (a) Sealing. Where portions of an interior raceway system are ex- posed to widely different temperatures, as in refrigerating or cold- storage plants, provision shall be made to prevent circulation of air from a warmer to a colder section through the raceway. (b) Expansion Joints. Expansion joints for runs of raceway shall be provided where required to compensate for thermal expansion and contraction. 70-84 NATIONAL ELECTRICAL CODE 300-7. Underground Runs. Conductors run underground shall comply with the provisions of Section 230-32 as far as mechanical protection is concerned. Underground cable run under a building shall be in a raceway that is extended beyond the outside y t de wall of the building. 300-8. Through Studs,Joists and Rafters. (a) Where exposed or concealed wiring conductors in insulating tubes or cables are installed through bored holes in studs, joists or similar wood members,holes shall be bored at the approximate centers of wood members,or at least two inches from the nearest edge where practical. (b) Where there is no objection because of weakening the building structure,metal-clad or nonmetallic sheathed cable, aluminum sheathed cable and Type MI cable may be laid in notches in the studding or joists when the cable at those points is protected against the driving of nails into it by having the notch covered with a steel plate at least 1/16 inch in thickness before building finish is applied. 300-9. Grounding Metal Enclosures. Metal raceways, boxes, cabinets, cable armor and fittings shall be grounded if and as prescribed in Article 250. 300-10. Electrical Continuity of Metal Raceways and Enclosures. Metal raceways, cable armor, and other metal enclosures for conductors, shall be metallically joined together into a continuous electrical con- ductor, and shall be so connected to all boxes, fittings and cabinets as to provide effective electrical continuity. Raceways and cable assem- blies shall be mechanically secured to boxes, fittings, cabinets and other enclosures,except as provided for nonmetallic boxes in Section 370-7. 300-11. Secured in Place. Raceways, cable assemblies, boxes, cabi- nets and fittings shall be securely fastened in place, unless otherwise provided for specific purposes elsewhere in this Code. See Article 318 for Continuous Rigid Cable Supports. 300-12. Mechanical Continuity—Raceways and Cables. Raceways and cable assemblies shall be continuous from outlet to outlet and from fit- ting to fitting. 300-13. Mechanical Continuity—Conductors. Conductors shall be contin- uous between outlets,devices,etc.,and,except as permitted for auxiliary gutters in Section 374-8, and for wireways in Section 362-6, there shall be no splice or tap within a raceway itself. 300-14. Free Length of Conductors at Outlets and Switch Points. At least six inches of free conductor shall be left at each outlet and switch point for the making up of joints or the connection of fixtures or devices, except where conductors are intended to loop without joints through lampholders,receptacles and similar devices. 300-15. Boxes or Fittings. Except as permitted in Sections 336-11 and 410-60 a box or fitting shall be installed at each outlet, switch point, ARTICLE 300—WIRING METHODS—GENERAL 70-85 junction point or conductor splice connection joining sections of con- duit, electrical metallic tubing or surface raceway. A box shall be in- stalled at each outlet, switch point, or conductor splice connection joining sections of metal-clad cable, aluminum sheathed cable, non- metallic sheathed cable or Type MI cable, and at each outlet and switch point of concealed knob-and-tube work. Exception: Straight through splice joints for MI cable are permitted without a box provided the splice is accessible and a fitting approved for the purpose is used. 300-16. Raceway or Cable to Open or Concealed Wiring. (a) A box or terminal fitting having a separately bushed hole for each conductor shall be used wherever a change is made from conduit, electrical metallic tubing, nonmetallic sheathed cable, metal-clad ca- ble, aluminum sheathed cable, or Type MI cable and surface raceway wiring to open wiring or to concealed knob-and-tube work. A fitting used for this purpose shall contain no taps or spices and shall not be used at fixture outlets. (b) A bushing may be used in lieu of a box or terminal fitting at ends of conduit or electrical metallic tubing where conductors leave the conduit or tubing behind a switchboard, or where more than 4 con- ductors leave the conduit or tubing at control apparatus or in similar locations, in which case the conductors shall be bunched, taped and painted with insulating paint. Such a bushing shall be of the insulating type except for lead-covered conductors. 300-17. Number of Conductors in Raceway. In general the percent- age of the total interior cross-sectional area of a raceway occupied by conductors shall not be more than will permit a ready installation or withdrawal of the conductors and dissipation of the heat generated without injury to the insulation of the conductors. See the follow- ing Sections of this Code: conduit, Section 346-6; electrical metallic tubing, 348-6; flexible metal conduit, 350-3; surface raceways, 352-4 and 352-25; underfloor raceways, 354-5; cellular metal floor raceways, 356-5; structural raceways, 357-6; cellular concrete floor raceways, 358-9; wireways, 362-5; auxiliary gutters, 374-5; theatres, 520-5; signs, 600-21(d); elevators, 620-33; and sound recording, 640-3 and 640-4; and Remote-Control, Low-Energy Power, Low-Voltage Power and Signal Circuits,Article 725. 300-18. Inserting Conductors in Raceways. (a) Raceways shall first be installed as a complete raceway system without conductors, except those raceways exposed and having a re- movable cover or capping. (b) As far as possible, conductors shall not be inserted until the in- terior of the building has been physically protected from the weather, and all mechanical work on the building which is likely to injure the conductors has been completed. (c) Pull wires, if to be used, shall not be installed until the raceway system is in place. (d) Cleaning agents or materials used as lubricants that might have a deleterious effect on conductor coverings shall not be used. 70-86 NATIONAL ELECTRICAL CODE 300-19. Supporting Conductors in Vertical Raceways. (a) Conductors in vertical raceways shall be supported at intervals not greater than those specified in the following Table: Table 300-19(a). Spacings for Conductor Supports Conductors Aluminum Copper No. 18 to No.8 Not Greater than....100 feet 100 feet No. 6 to No.0 ....200 feet 100 feet No.00 to No.0000 46 " ....180 feet 80 feet 211,601 CM to 350,000 CM " " " ....135 feet 60 feet 350,001 CM to 500,000 CM " " " ....120 feet 50 feet 500,001 CM to 750,000 CM " " " .... 95 feet 40 feet Above 750,000 CM " " " .... 85 feet 35 feet (b) One of the following methods of support, or a method of equal effectiveness is recommended: (1) By clamping devices constructed of or employing insulating wedges inserted in the ends of the conduits. With cables having var- nished cambric or thermoplastic insulation it may also be necessary to clamp the conductor. (2) By inserting boxes at the required intervals in which insulating supports are installed and secured in a satisfactory manner to with- stand the weight of the conductors attached thereto, the boxes being provided with covers. (3) In junction boxes, by deflecting the cables not less than 90 degrees and carrying them horizontally to a distance not less than twice the diameter of the cable, the cables being carried on two or more in- sulating supports, and additionally secured thereto by tie wires if de- sired. When this method is used cables shall be supported at intervals not greater than 20 per cent of those mentioned in the preceding tabu- lation. 300-20. Induced Currents in Metal Enclosures. When conductors car- rying alternating current are installed in metal enclosures they shall be so arranged as to avoid heating the surrounding metal by induction. To accomplish this all phase conductors and the neutral,where one is used, shall be grouped together. When a single conductor of a circuit passes through metal with magnetic properties the inductive effect shall be minimized by: (1) Cutting slots in the metal between the individual holes through which the individual conductors pass,or (2) Passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit. Exception: In the case of circuits supplying vacuum or electric dis- charge lighting systems or signs, or X-ray apparatus, the currents car- ried by the conductors are so small that the inductive heating effect may be ignored where these conductors are placed in metal enclosures or pass through metal. ARTICLE 300—WIRING METHODS—GENERAL 70_87 Aluminum being a nonmagnetic metal, there.will be no heating due to eddy currents, however, induced currents will be present. These are not considered of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections. 300-21. Prevention of Spread of Fire. Electrical installations shall be so made that the possible spread of fire through fire-stopped partitions, hollow spaces, fire walls or fire partitions, vertical shafts, ventilating or air-handling ducts is reduced to a minimum. 300-22. Wiring in Ducts,Plenums,and Other Air Handling Spaces. (a) No wiring systems of any type shall be installed in ducts used to transport dust, loose stock, flammable vapors, nor shall any wiring sys- tem of any type be installed in any duct, or shaft containing only such ducts,used for vapor removal or ventilation of commercial type cooking equipment. (b) Wiring systems of MI cable, ALS cable, electrical metallic tub- ing,or rigid metal conduit may be installed in ducts or plenum chambers used to transport higher velocity environmental air. Flexible metal con- duit may be used, in lengths not to exceed 4 feet, to connect physically adjustable equipment and devices permitted to be in these ducts and plenum chambers.The connectors used with flexible metal conduit shall effectively close any openings in the connection. Equipment and devices may only be installed within such ducts or plenum chambers if neces- sary for their direct action upon,or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to fa- cilitate maintenance and repair, enclosed gasketed type fixtures may be installed. (c) Hollow spaces which are used as ducts or plenum chambers for lower velocity environmental air, other than those described in Para- graph (b) above, may contain MI cable, ALS cable, electrical metallic tubing, rigid metal conduit, flexible metal conduit, and other electrical equipment that is permitted within the concealed spaces of such struc- tures,provided: (1) The wiring materials, including fixtures, are suitable for the expected ambient temperature to which they will be subjected. (2) The wiring system, including fixtures, in no way reduces the fire protective rating of the construction in which they are installed. (3) Flexible metal conduit shall be limited to the connection of de- vices,equipment, and fixtures in lengths not exceeding six feet. The con- nectors used with flexible metal conduit shall effectively close any open- ings in the connection. Exception No. 1. The above provisions shall not apply to integral fan systems specifically approved for the purpose. Exception No. 2. This section does not include habitable rooms or areas of buildings,the prime purpose of which is not air handling. NFPA Standard for the Installation of Air Conditioning and Ventilating Systems, No. 90A, sets forth requirements of building used for ducts and plenums. (d) The wiring systems used for data processing systems and located 70-88 NATIONAL ELECTRICAL CODE within air handling areas created by raised floors shall conform to Article 645. 300-23. Temporary Wiring. (a) Suitable disconnecting switches or plug connectors shall be in- stalled to permit the disconnection of all conductors of the temporary circuit by a single operation. (b) No bare conductors nor earth returns shall be used for the wiring of any temporary circuit. ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 310-1. General. (a) The purpose of this Article is to assure that conductors have mechanical strength, insulation, and ampacity adequate for the particu- lar conditions under which they are to be used. (b) Conductors shall be insulated, except when covered or bare con- ductors are specifically permitted in this Code. (c) The provisions of this Article are not intended to apply to con- ductors which form an integral part of equipment such as motors, mo- tor controllers, and the like, or which are provided for elsewhere in this Code. 310-2. Application and Construction. (a) Conductor Application. Conductor insulations as specified in the following Table 310-2(a) may be installed for any of the wiring meth- ods recognized in this Chapter, except as otherwise provided for in the Table or in Section 310-3, or as otherwise specified in this Code. They are suitable for 600 volts unless otherwise specified. (b) Conductor Construction. Insulated conductors for use at 600 volts or less shall conform to the provisions of Table 310-2(b). (c) Marking. Insulated wires, cables and cords of all kinds except paper-insulated wire shall have a continuous distinctive marking so that their maker may be readily identified. All wires, cables and cords shall also be plainly tagged or marked as follows: (1) The maximum working voltage for which the wire was tested or approved. This may be omitted for asbestos-covered switchboard wires. (2) The words "National Electrical Code Standard," or "NEC Std." (3) The manufacturer's name, trade-mark, or other distinctive marking, by which the organization responsible for the product may be readily identified. (4) Month and year when manufactured. (5) The proper type letter for the particular style of wire or cable as given in the following sections. (d) Surface Marking. A durable marking on the surface shall be provided at intervals not exceeding 24 inches, by which the maker may be identified. Such marking shall be the manufacturer's name, trade- (Continued on page 96) ARTICLE 310—CONDUCTORS 70-89 Table 310-2(a). Conductor Application Trade Type Max. Application Name Letter Provisions iem P• Rubber-Covered *RF-1 60°C Fixture wiring. Fixture Wire 140°F Limited to 300 V. Solid or *RF-2 60°C Fixture wiring, and as permitted 7-Strand 140°F in Section 310-8. Rubbered-Covered *FF-1 60°C Fixture wiring. Fixture Wire 140°F Limited to 300 V. Flexible Stranding *FF-2 60°C Fixture wiring, and as permitted 140°F in Section 310-8. Heat-Resistant *RFH-1 75°C Fixture wiring. Rubber-Covered 167°F Limited to 300 V. Fixture Wire Solid or *RFH-2 75°C Fixture wiring, and as permitted 7-Strand 167°F in Section 310-8. Heat-Resistant *FFH-1 75°C Fixture wiring. Rubber-Covered 167°F Limited to 300 V. Fixture Wire Flexible *FFH-2 75°C Fixture wiring, and as permitted Stranding 167°F in Section 310-8. Thermoplastic- *TF 60°C Fixture wiring, and as permitted Covered Fixture 140°F in Section 310-8, and for circuits Wire—Solid or as permitted in Article 725. Stranded Thermoplastic- *TFF 60°C Fixture wiring, and as permitted Covered Fixture 140°F in Section 310-8, and for circuits Wire—Flexible as permitted in Article 725. Stranding Heat Resistant, *TFN 90°C Fixture wiring, and as permitted Thermoplastic— in Section 310-8. Covered Fixture Wire—Solid or tr Stranded Heat Resistant *TFFN 90°C Fixture wiring, and as permitted Thermoplastic— in Section 310-8. Covered Fixture Wire—Flexible Stranding ICotton-Covered, *CF 90°C Fixture wiring. Heat-Resistant, 194°F Limited to 300 V. Fixture Wire *Fixture wires are not intended for installation as branch circuit conduc- tors except as permitted in Article 725. 70-90 NATIONAL ELECTRICAL CODE Table 310-2(a)—Continued Trade Type Max.. Application •Name LetterO t,n9 Provisions Tem p. Asbestos-Covered 150°C Fixture wiring. Heat-Resistant, *AF 302°F Limited to 300 V. and Indoor Fixture Wire Dry Location. Fluorinated *PF 200°C Fixture Wiring and as permitted Ethylene in Section 310-8. Propylene *PGF 392°F Fixture Wire Solid or 7 Strand Fluorinated Ethylene *PFF 150°C Fixture Wiring and as permitted Propylene in Section 310-8. Fixture Wire *PGFF 302°F Silicone Rubber *SF-1 200°C Fixture wiring. Insulated Fixture 392°F Limited to 300 V. Wire Solid *SF-2 200°C Fixture wiring and as permitted or 7 Strand 392°F in Section 310-8. Silicone Rubber *SFF-1 150°C Fixture wiring. Insulated Fixture 302°F Limited to 300 V. Wire Flexible *SFF-2 150°C Fixture wiring and as permitted Stranding 302°F in Section 310-8. Heat-Resistant RH 75°C Dry locations. Rubber 167°F Heat-Resistant RHH 90°C Dry locations. Rubber 194°F Moisture and RHW 75°C Dry and wet locations. Heat-Resistant 167°F For over 2000 volts, insulation Rubber shall be ozone-resistant. Heat-Resistant RUH 75°C Dry locations. Latex Rubber Moisture Resistant RUW 60°C Dry and wet locations. Latex Rubber 140°F Thermoplastic T 60°C Dry locations. 140°F Moisture- TW 60°C Dry and wet locations. Resistant 140°F Thermoplastic *Fixture wires are not intended for installation as branch circuit conduc- tors except as permitted in Article 725. ARTICLE 310—CONDUCTORS 70-91 Table 310-2(a)—Continued Trade Type Max. Application Name Letter OTemt1n8 Provisions P• Heat-Resistant THHN 90°C Dry locations. Thermoplastic 194°F Moisture and THW 75°C Dry and wet locations. Heat-Resistant 167°F Thermoplastic Moisture and THWN 75°C Dry and wet locations. Heat-Resistant 167°F Thermoplastic Moisture and 90°C Dry locations. Heat-Resistant 194°F Cross-Linked XHHW Thermosetting 75°C Polyethylene 167°F Wet locations. Moisture-,Heat-and 60°C Wet locations,Machine Tool Wir- Oil-Resistant 140°F ing. (see Article 670 and NFPA Thermoplastic MTW Standard No.79). 90°C Dry locations. Machine Tool 194°F Wiring. (see Article 670 and NFPA Standard No.79). Moisture-, THW-MTW 75°C Dry and wet locations. Heat-and 167°F Oil-Resistant Thermoplastic 90°C Special applications within elec- 194°F tric discharge lighting equipment. Limited to 1000 open-circuit volts or less. (Size 14-8 only.) Thermoplastic TA 90°C Switchboard wiring only. and Asbestos 194°F Thermoplastic TBS 90°C Switchboard wiring only. and Fibrous 194°F Outer Braid Synthetic SIS 90°C Switchboard wiring only. Heat-Resistant 194°F Mineral Insulation MI 85°C Dry and wet locations with Type (Metal Sheathed) 185°F 0 termination fittings. 250°C For special application. 482°F 70-92 NATIONAL ELECTRICAL CODE Table 310-2(a)—Continued Trade Type Max. Application Name Letter Og Provisions Temt'n P. Silicone- SA 90°C Dry locations. Asbestos 194°F 125°C For special application. 257°F Fluorinated 90°C Dry locations. Ethylene FEP 194°F Propylene or 200°C Dry locations—special applica- FEPB 392°F tions. Varnished V 85°C Dry locations only. Smaller than Cambric 185°F No.6 by special permission. Asbestos and AVA 110°C Dry locations only. Varnished 230°F Cambric Asbestos and AVL 110°C Dry and wet locations. Varnished 230°F Cambric Asbestos and AVB 90°C Dry locations only. Varnished 194°F Cambric Asbestos A 200°C Dry locations only.Only for leads 392°F within apparatus or within race- ways connected to apparatus. Limited to 300 V. Asbestos AA 200°C Dry locations only.Only for leads 392°F within apparatus or within race- ways connected to apparatus or as open wiring. Limited to 300 V. Asbestos AI 125°C Dry locations only.Only for leads 257°F within apparatus or within race- ways connected to apparatus. Limited to 300 V. Asbestos AIA 125°C Dry locations only.Only for leads 257°F within apparatus or within race- ways connected to apparatus or as open wiring. Paper 85°C For underground service conduc- 185°F tors, or by special permission. ARTICLE 310—CONDUCTORS 70-93 Table 310-2(b). Conductor Insulations Trade Type Thickness of Outer Name Letter Insulation Insulation Covering **14-12 2/64 Inch *Moisture- 10 3/64 Inch resistant, Heat- RH Heat- 8-2 4/64 Inch flame- Resistant RHH Resistant 1-4/0 5/64 Inch retardant, Rubber 213-500 6/64 Inch non- 501-1000 7/64 Inch metallic 1001-2000 8/64 Inch covering Moisture RHW Moisture 14-10 3/64 Inch'`Moisture- and Heat- and Heat 8-2 4/64 Inch resistant, Resistant Resistant 1-4/0 5/64 Inch flame- Rubber 213-500 6/64 Inch retardant, 501-1000 7/64 Inch non- 1001-2000 8/64 Inch metallic covering Heat- RUH 90% Un- 14-10 18 Mils Moisture- Resistant milled, 8-2 25 Mils resistant, Latex Grainless flame- Rubber Rubber retardant, non- metallic covering Moisture- RUW 90% Un- 14-10 18 Mils Moisture- Resistant milled, 8-2 25 Mils resistant, Latex Grainless flame- Rubber Rubber retardant, non- metallic covering Thermo- T Flame- 14-10 2/64 Inch plastic Retardant, 8 3/64 Inch Thermo- 6-2 4/64 Inch plastic 1-4/0 5/64 Inch None Compound 213-500 6/64 Inch 501-1000 7/64 Inch 1001-2000 8/64 Inch Moisture- TW Flame- 14-10 2/64 Inch Resistant Retardant, 8 3/64 Inch Thermo- Moisture- 6-2 4/64 Inch plastic Resistant 1-4/0 5/64 Inch None Thermo- 213-500 6/64 Inch plastic 501-1000 7/64 Inch 1001-2000 8/64 Inch *Outer covering is not required over rubber insulations which have been specifically approved for the purpose. **For 14-12 sizes RHH shall be 3/64 inch thickness insulation. For insulated aluminum conductors, the minimum size is No. 12 AWG. See Tables 310-14 and 310-15. 70-94 NATIONAL ELECTRICAL CODE Table 310-2(b)—Continued Trade Type Thickness of Outer Name Letter Insulation Insulation Covering Heat- Flame- 14-12 15 Mils Resistant Retardant 10 20 Mils Thermo- THHN Heat 8-6 30 Mils Nylon plastic Resistant 4-2 40 Mils Jacket Thermo- 1-4/0 50 Mils plastic 250-500 MCM 60 Mils Moisture Flame- 14-10 3/64 Inch and Heat- Retardant, 8-2 4/64 Inch Resistant Moisture 1-4/0 5/64 Inch Thermo- THW and Heat- 213-500 6/64 Inch None plastic Resistant 501-1000 7/64 Inch Thermo- 1001-2000 8/64 Inch plastic Moisture Flame- 14-12 15 Mils and Heat- Retardant, 10 20 Mils Resistant Moisture 8-6 30 Mils Nylon Thermo- THWN and Heat- 4-2 40 Mils Jacket plastic Resistant 1-4/0 50 Mils Thermo- 250-500 MCM 60 Mils plastic Moisture Flame- 14-10 30 Mils and Heat- Retardant 8-2 45 Mils Resistant Cross- 1-4/0 55 Mils Cross- XHHW Linked 213-500 65 Mils None Linked Polyethylene 501-1000 80 Mils Thermo- 1001-2000 95 Mils setting Polyethylene (A) (B) Moisture-, Flame- 22-12 2/64 15 Mils (A) None Heat-and Retardant, 10 2/64 20 Mils Oil-Resistant Moisture-, 8 3/64 30 Mils (B) Nylon Thermo- MTW Heat-and 6 4/64 30 Mils jacket plastic Oil-Resistant 4-2 4/64 40 Mils Thermo- 1-4/0 5/64 50 Mils plastic 213-500MCM ...6/64 60 Mils 501-1000MCM ..7/64 70 Mils Moisture-, Flame- 14-10 3/64 Heat,and Retardant, 8-2 4/64 'i Oil-Resistant Moisture-, 1-4/0 5/64 Thermo- THW- Heat-and 213-500 6/64 None plastic MTW Oil-Resistant 501-1000 7/64 Thermo- 1001-2000 8/64 plastic Thermo- Thermo- Th'pl'. Asb. Flame- plastic and plastic and 14-8 20 Mils 20 Mils retardant, Asbestos TA Asbestos 6-2 30 Mils 25 Mils non-metallic 1-4/0 40 Mils 30 Mils covering For insulated aluminum conductors, the minimum size is No. 12 AWG. See Tables 310-14 and 310-15. ARTICLE 310—CONDUCTORS 70-95 Table 310-2(b)—Continued Trade Type Thickness of Outer Name Letter Insulation Insulation Covering Thermo- 14-10 2/64 Inch Flame- plastic TBS Thermo- 8 3/64 Inch retardant, and Fibrous plastic 6-2 4/64 Inch non-metallic Braid 1-4/0 5/64 Inch covering Synthetic Heat- 14-10 2/64 Inch 8 3/64 Inch Heat- S1S Resistant 6-2 4/64 Inch None Resistant Rubber 1-4/0 5/64 Inch Mineral- Insulated MI Magnesium 16-4 50 Mils mapper Metal- Oxide 3-250 MCM 55 Mils Sheathed 14-10 3/64 Inch 8-2 4/64 Inch Silicone- Silicone 1-4/0 5/64 Inch Asbestos Asbestos SA Rubber 213-500 6/64 Inch or glass 501-1000 7/64 Inch 1001-2000 8/64 Inch Fluorinated 14-10 20 Mils FEP Ethylene 8-2 30 Mils None Fluorinated Propylene Ethylene 14-8 14 Mils Glass braid Propylene Fluorinated FEPB Ethylene Asbestos Propylene 6-2 14 Mils braid 14-8 3/64 Inch 6-2 4/64 Inch Varnished V Varnished 1-4/0 5/64 Inch Non-metallic Cambric Cambric 213-500 6/64 Inch covering or 500-1000 7/64 Inch lead-sheath 1001-2000 8/64 Inch Asbestos and AVA Impregnated (Dimen.in Mils) AVA- Varnished and Asbestos and AVA AVL asbestos Cambric AVL Varnished 1st 2nd 2nd braid or Asb. VC Asb. Asb. Cambric 14-8 (solid glass only) ..— 30 20 25 14-8 10 30 15 25 AVL-lead 6-2 15 30 20 25 sheath 1-4/0 ....20 30 30 30 213-500 .. 25 40 40 40 501-1000 . 30 40 40 40 1001-2000 30 50 50 50 For insulated aluminum conductors, the minimum size is No. 12 AWG. See Tables 310-14 and 310-15. 70-96 NATIONAL ELECTRICAL CODE Table 310-2(b)—Continued Trade Type Thickness of Outer Name Letter Insulation Insulation Covering VC Asb. 18-8 30 20 Flame- 6-2 40 30 retardant, 1-4/0 40 40 cotton braid (switchboard wiring) 2nd Asb. VC Asb. Asbestos and Impregnated 14-8 10 30 15 Varnished AVB Asbestos and 6-2 15 30 20 Flame- Cambric Varnished 1-4/0 20 30 30 retardant, Cambric 213-500 ...25 40 40 cotton braid 501-1000 .. 30 40 40 1001-2000 . 30 50 50 Asbestos A Asbestos 14 30 Mils Without as- 12-8 40 Mils bestos braid 14 30 Mils With asbestos Asbestos AA Asbestos 12-8 30 Mils braid or 6-2 40 Mils glass 1-4/0 60 Mils Asbestos AI Impregnated 14 30 Mils Without as- Asbestos 12-8 40 Mils bestos braid Sol. Str. 14 30 Mils 30 Mils 12-8 30 Mils 40 Mils Asbestos AIA Impregnated 6-2 40 Mils 60 Mils With asbestos Asbestos 1-4/0 60 Mils 75 Mils braid or 213-500 90 Mils glass 501-1000 105 Mils Paper Paper Lead sheath The nonmetallic covering over individual rubber-covered conductors of aluminum sheathed cable and of lead-sheathed or multiple-conductor cable is not required to be flame retardant. For metal-clad cable,see Section 334-2. For nonmetallic-sheathed cable, see Section 336-2. For Type OF cable, see Section 339-1.For aluminum sheathed cable,see Section 331-9. For insulated aluminum conductors, the minimum size is No. 12 AWG. See Tables 310-14 and 310-15. (Continued from page 88) mark, or other distinctive marking by which the organization responsi- ble for the product may be identified. The marking shall also include the type letter or letters as specified in Article 310, Table 310-2(b) and Articles 336, 338 and 339,the size AWG or circular mils and the maxi- mum voltage on the following types of wire and cable rated 600 volts or less: ARTICLE 310—CONDUCTORS 70-97 (1) Single conductor only, rubber insulated and thermoplastic in- sulated for General Wiring. (2) Nonmetallic Sheathed Cable. (3) Service-Entrance Cable. (4) Underground Feeder and Branch Circuit Cable. All other types of wire and cable,flexible cords,fixture wires, switch- board wires, and any of the above types with a metallic covering are not required to have a marking on the surface. (e) Classification. In addition to the type letters specified in Table 310-2(b),the following letters shall apply: (1) A type letter or letters used alone indicates a single insulated conductor. (2) The letter "D" used as a suffix indicates a twin wire with two insulated conductors laid parallel under an outer nonmetallic covering. (3) The letter "M" used as a suffix indicates an assembly of two or more insulated conductors twisted together under an outer nonme- tallic covering. (4) The letter "L" used as a suffix indicates an outer covering of lead. (5) Voltage. Type letters, when used alone, indicate conductors for use at not more than 600 volts. Conductors for use at higher volt- ages shall be indicated by adding numerical suffixes to the type letters as follows: 10—for use at not more than 1000 volts. 20—for use at not more than 2000 volts. 30—for use at not more than 3000 volts. 40—for use at not more than 4000 volts. 50—for use at not more than 5000 volts. The working voltages referred to in the Table are the operating voltages between phases of single and two-phase systems, and three-phase systems with grounded or ungrounded neutral. (6) All NEC standard conductors shall be examined and tested at the factory and,if approved,shall be labeled before shipment. (f) Identification of Insulation. All rubber-insulated conductors and all thermoplastic-insulated conductors, No. 18 and larger, shall have a readily recognizable durable marking to indicate the type of insulation; except that single-conductor, code-rubber insulated conductors having a lead sheath; and multi-conductor cables, metal-clad cable, and non- metallic-sheathed cable having code-rubber or nonmoisture-resistant thermoplastic-insulated conductors,need not be so marked. (g) Identified Conductors. Single insulated conductors of No. 6 or smaller, intended for use as identified conductors of circuits shall have an outer identification of a white or natural gray color. Twin and twisted-pair conductors and three-conductor cables shall have one con- ductor, and four-conductor cables shall have at least one conductor identified in this manner. Multiple conductor flat cable No. 4 AWG or I larger may employ an external ridge on the identified conductor. 70-98 NATIONAL ELECTRICAL CODE Exception No. 1—Multiple-conductor varnished cloth insulated cables. Exception No.2—Fixture wires as outlined below. Exception No.3—Mineral insulated-metal sheathed cable. For fixture wires the identification shall be as above, or by means of (1) stripes, or (2) by the means described in Sections 400-13 (a), (b), (c), (d) and(e). For aerial cable the identification shall be as above, or by means of a ridge so located on the exterior of the cable as to identify it. Wires having their outer covering finished to show a white or natural gray color but having colored tracer threads in the braid, identifying the source of manufacture,are considered as meeting the provisions of this Section. (h) Unidentified Conductors. Single conductors, intended for use as unidentified conductors, and conductors other than the identified con- ductor in multi-conductor cables, shall be finished to show a color or combination of colors other than, and contrasting with,white or natural gray. The colors contrasting with white or natural gray, may be pro- vided by means of an approved stripe or stripes on black conductors. For identification requirements for conductors larger than No. 6 see Section 200-6(b). (i) Insulation Thickness—Over 600 Volts. The thickness of insula- tion for conductors for use at over 600 volts shall conform to Tables 310-2 (i-1 thru i-4): 310-3. Insulating Materials. (a) The rubber insulations include those made from natural and synthetic rubber,neoprene and other vulcanizable materials. (b) Thermoplastic insulation may stiffen at temperatures below mi- nus 10°C (14°F) and care should be used in its installation at such tem- peratures. It may be deformed when subject to pressure; care should be taken in its installation, as for example, at bushings, or points of support.See Section 373-6(b). 310-4. Temperature Limitations. No conductor shall be used under such conditions that its temperature, even when carrying current, will exceed the temperature specified in Table 310-2(a) for the type of in- sulation involved. 310-5 Wet Locations. Insulated conductors used underground, in con- crete slabs or other masonry in direct contact with earth, in wet loca- tions, or where condensation or accumulation of moisture within the raceway is likely to occur, shall be moisture- and heat-resistant, rubber- covered (Type RHW); moisture-resistant latex rubber (Type RUW); moisture-resistant, thermoplastic-covered (Type TW); moisture- and (Continued on page 101) ARTICLE 310—CONDUCTORS 70-99 Table 310-2(i)(1) Thickness of Rubber Insulation for Rubber-Covered Wire and Cable,in 64ths of an Inch Classification Conductor Size AWG or MCM RH 10 RH 20 RHW 30t RHW 40t RHW 50t 14-12* 4 5 10- 8* 4 5 7 9 10* 6- 2 5 6 8 9 10 1-4/0 6 7 8 9 10 213-500 7 8 9 10 11 501-1000 8 9 9 10 11 1001-2000 9 9 10 11 12 *No. 12 AWG is the minimum conductor size for aluminum and No. 8 AWG is the minimum conductor size for 5000 volts operation. t Shall be of approved ozone-resistant type for operation at voltages over 2000. Table 310-2(i)(2) Thickness of Varnished-Cambric Insulation for Single-Conductor Cable,in 64ths of an Inch Conductor Size For Voltages Not Exceeding AWG or MCM 1000 Y000 3000 4000 5000 14 4 12 4 5 10 4 5 6 8-2 4 5 6 7 9 1-4/0 5 6 6 7 9 213-500 6 6 7 8 10 501-1000 7 7 7 8 10 1001-2000 8 8 8 9 10 70-100 NATIONAL ELECTRICAL CODE Table 310-2(i)(3) Thickness of Varnished-Cambric Insulation for Multiple-Conductor Cable,in 64ths of an Inch For Voltages Not Exceeding Conductor Size AWG or MCM 1000 2000 3000 4000 5000 C B C B C B C B C B 14 4 0 .. .. .. .. .. .. .. .. 12 4 0 5 0 .. .. .. . . .. .. 10 4 0 5 0 5 2 8-2 4 0 5 0 5 2 6 3 6 4 1-4/0 5 0 6 0 6 2 6 3 6 4 213-500 6 0 6 0 6 2 6 3 7 4 501-1000 6 2 6 2 6 3 6 4 7 4 1001-2000 7 2 7 2 7 3 7 4 7 5 The thickness given in columns headed "C" are for the insulation on the individual conductors. Those given in the columns headed "B" are for the thickness of the overall belt of insulation. Table 310-2(i)(4) Thickness of Asbestos and Varnished-Cambric Insulation for Single-Conductor Cable, Types AVA,AVB and AVL,in Mils 1st Wall Vanished Cambric Asbestos Conductor Asbestos 2nd Wall AWG or MCM For Voltages Not Exceeding 1000-5000 1000 2000 3000 4000 5000 1000-5000 14-2 15 45 60 80 100 120 25 1-4/0 20 45 60 80 100 120 30 213-500 25 45 60 80 100 120 40 501-1000 30 45 60 80 100 120 40 1001-2000 30 55 75 95 115 140 50 1 ARTICLE 310—CONDUCTORS 70-101 (Continued from page 98) heat-resistant, thermoplastic-covered (Type THW);moisture-and heat- resistant thermoplastic (Type THWN); moisture- and heat-resistant cross-linked thermosetting polyethylene (Type XHHW); lead covered; aluminum sheathed cable (Type ALS); mineral insulated-metal sheathed (Type MI);or of a type approved for the purpose. Such conductors are not suitable for direct burial in the earth unless of a type specifically approved for the purpose. 310-6. Buried Conductors. Cables of one or more conductors for direct burial in the earth shall be of a type approved for the purpose and use, such as Types USE and UF.Where single conductor cables are installed, all conductors of each service, feeder, sub-feeder or branch circuit, in- cluding the neutral conductor, shall be run continuously in the same trench or raceway.Supplementary mechanical protection,such as a cov- ering board,concrete pad,raceway,etc.,may be required by the author- ity having jurisdiction.See Section 339-3(c). 310-7. Corrosive Conditions. Conductors exposed to oils, greases, va- pors, gases, fumes, liquids or other substances having a deleterious ef- fect upon the conductor or insulation shall be of a type approved for the purpose. 310-8. Minimum Size of Conductors. Conductors, whether solid or stranded, shall not be smaller than No. 14, except for printing press control circuits; as provided for flexible cords in Section 400-7; for fix- ture wire in Section 410-18; for fractional horsepower motors in Sec- tion 430-22; for cranes and hoists in Section 610-14; for elevator con- trol and signal circuits in Section 620-12; and for remote-control, low energy power,low-voltage power and signal circuits in Section 725-13. 310-9. Stranded Conductors. Except when used as bus bars or in Type MI Cable, conductors No. 6 and larger, installed in raceways, shall be stranded. 310-10. Conductors in Multiple. Conductors in sizes 1/0 and larger may be run in multiple provided the arrangement is such as to assure equal division of total current among all conductors involved. All of the multiple conductors shall be of the same length, of the same con- ductor material, circular-mil area, same insulation type and terminated in the same manner. Where run in separate raceways or cables, the raceways or cables shall have the same physical characteristics. When conductors are used in multiple, space in enclosures should be given consideration. 310-11. Ampacity Reduction Factors. Where more than three conduc- tors are installed in a raceway or assembled into one or more cables the ampacity of each conductor shall be reduced in accordance with Note 8 to Tables 310-12 through 310-15. 70-102 NATIONAL ELECTRICAL CODE Notes To Tables 310-12 through 310-15. Ampacity. The maximum, continuous, ampacities of copper conductors are given in Tables 310-12 and 310-13. The ampacities of aluminum con- ductors are given in Tables 310-14 and 310-15. 1. Explanation of Tables. For ex- able operating temperature; although planation of Type Letters, and for insulation can be used in a room recognized size of conductors for the temperature approaching its maxi- various conductor insulations, see mum allowable operating tempera- Sections 310-2 and 310-3. For in- ture limit if the current is reduced in stallation requirements, see Section accordance with the Correction Fac- 310-1 through 310-7,and the various tors for different room temperatures Articles of this Code. For flexible as shown in the Correction Factor cords see Tables 400-9 and 400-11. Table,Note 15. 2. Application of Tables. For 8. More Than Three Conductors open wiring on insulators and for in a Raceway or Cable. Tables 310- concealed knob-and-tube work, the 12 and 310-14 give the allowable allowable ampacities of Tables 310- ampacities for not more than three 13 and 310-15 shall be used. For all conductors in a raceway or cable. other recognized wiring methods, Where the number of conductors in the allowable ampacities of Tables a raceway or cable exceeds three, 310-12 and 310-14 shall be used, un- the allowable ampacity of each con- less otherwise provided in this Code. ductor shall be reduced as shown in 3. Aluminum Conductors. For the following Table: aluminum conductors, the allowable Per Cent of Values in ampacities shall be in accordance Number of Tables 310-12 and with Tables 310-14 and 310-15. Conductors 310-14 4. Bare Conductors. Where bare 4 to 6 80 conductors are used with insulated 5 to 42 60 conductors, their allowable ampac- 43 5 and above 52 0 ities shall be limited to that permit- ted for the insulated conductors of Exception No. 1—When conduc- the same size. tors of different systems, as provided 5. Type MI Cable. The tempera- in Section 300-3, are installed in a ture limitation on which the am- common raceway the derating factors pacities of Type MI cable are based, shown above apply to the number of is determined by the insulating ma- Power and Lighting (Articles 210, terials used in the end seal.Termina- 215, 220 and 230) conductors only. tion fittings incorporating unimpreg- Where the number of conductors nated organic insulating materials in a raceway or cable exceeds three, are limited to 85°C.operation. or where single conductors or multi- 6. Ultimate Insulation Tempera- conductor cables are stacked or bun- ture. In no case shall conductors be dled without maintaining spacing as associated together in such a way required in Article 318 and are not with respect to the kind of circuit, installed in raceways, the individual the wiring method employed, or the ampacity of each conductor shall be number of conductors,that the limit- reduced as shown in the above table. ing temperature of the conductors Exception No. 2 — The derating will be exceeded. factors of Sections 210-23(b) and 7. Use of Conductors With Higher 220-2 (second paragraph) do not Operating Temperatures. Where the apply when the above derating fac- room temperature is within 10 de- tors are also required. i grees C of the maximum allowable 9. Where Type XHHW cross- l operating temperature of the insula- linked thermosetting polyethylene in- tion, it is desirable to use an insula- sulated wire is used in wet locations, tion with a higher maximum allow- the allowable ampacities shall be that ARTICLE 310-CONDUCTORS 70-103 of Column 3 in Tables 310-12 counted in determining ampacities as through 310-15. Where used in dry provided in Note 8. locations, the allowable ampacities Where the major portion of the load con- shall be that of Column 4 in Tables sists of electric discharge lighting there may 310-12 through 310-15. be harmonic currents present in the neu- tral conductor which may be equal to the 10. Overcurrent Protection.Where phase currents, thus the neutral could be the standard ratings and settings of consideredductor. to be a current-carrying con- overcurrent devices do not corre- spond with the ratings and settings 12. Voltage Drop. The allowable allowed for conductors, the next ampacities in Tables 310-12 through higher standard rating and setting 310-15 are based on temperature may be used. alone and do not take voltage drop into consideration. Exception -Except as limited in Section 240-5. 13. Deterioration of Insulation. It should be noted that even the best 11. Neutral Conductor. (a) A grades of rubber insulation will de- neutral conductor which carries only teriorate in time, so eventually will the unbalanced current from other need to be replaced. conductors, as in the case of nor- 14. Aluminum Sheathed Cable. mally balanced circuits of three or more conductors, shall not be The ampacities of Type ALS cable counted in determining ampacities are determined by the temperature as provided for in Note 8. limitation of the insulated conduc- tors incorporated within the cable. (b) In a 3-wire circuit consisting Hence the ampacities of aluminum of two phase wires and the neutral of sheathed cable may be determined a 4-wire, 3-phase WYE connected from the columns in Tables 310-12 system, a common conductor carries and 310-14 applicable to the type of approximately the same current as insulated conductors employed with- the other conductors and shall be in the cable.See Note 9. 15. Correction Factors. Ambient Temps.Over 30°C. 86°F. 60°C 75°C 85°C 90°C 110°C 125°C 200°C C. F. (140°F) (167°F) (185°F) (194°F) (230°F) (257°F) (392°F) 40 104 .82 .88 .90 .90 .94 .95 .... 45 113 .71 .82 .85 .85 .90 .92 .... 50 122 .58 .75 .80 .80 .87 .89 .... 55 131 .41 .67 .74 .74 .83 .86 .... 60 140 .... .58 .67 .67 .79 .83 .91 70 158 .... .35 .52 .52 .71 .76 .87 75 167 .... .... .43 .43 .66 .72 .86 80 176 .... .... .30 .30 .61 .69 .84 90 194 .... .... .... .... .50 .61 .80 100 212 .... .... .... .... .... .51 .77 120 248 .... .... .... .... .69 140 284 .... .... .... .... .59 70-104 NATIONAL ELECTRICAL CODE Table 310-12. Allowable Ampacities of Insulated Copper Conductors Not More than Three Conductors in Raceway or Cable or Direct Burial (Based on Ambient Temperature of 30° C. 86°F.) i Size Temperature Rating of Conductor.See Table 310-2(a) AWG 60°C 75°C 85°C 90°C 110°C 125°C 200°C MCM (140°F) (167°F) (185°F) (194°F) (230°F) (257°F) (392°F) , TYPES TYPES TYPES TYPES TYPES TYPES TYPES RUW RH, V, TA, AVA, AI A (14-2), RHW, MI TBS,SA, AVL (14-8), (14-8), T, RUH AVB, AIA AA, TW (14-2), SIS, FEP* THW, FEP, FEPB* THWN, FEPB, XHHW, RHH, THW-MTW THHN, XHHW** 14 15 15 25 25 t 30 30 30 12 20 20 30 30 t 35 40 40 10 30 30 40 40 t 45 50 55 8 40 45 50 50 60 65 70 6 55 65 70 70 80 85 95 4 70 85 90 90 105 115 120 3 80 100 105 105 120 130 145 2 95 115 120 120 135 145 165 1 110 130 140 140 160 170 190 0 125 150 155 155 190 200 225 00 145 175 185 185 215 230 250 000 165 200 210 210 245 265 285 0000 195 230 235 235 275 310 340 250 215 255 270 270 315 335 .... 300 240 285 300 300 345 380 .... 350 260 310 325 325 390 420 .... 400 280 335 360 360 420 450 .... 500 320 380 405 405 470 500 .... 600 355 420 455 455 525 545 .... 700 385 460 490 490 560 600 .... 750 400 475 500 500 580 620 .... 800 410 490 515 515 600 640 .... 900 435 520 555 555 .... .... .... 1000 455 545 585 585 680 730 .... 1250 495 590 645 645 .... .... .... 1500 520 625 700 700 785 .... .... 1750 545 650 735 735 .... .... .... 2000 560 665 775 775 840 .... .... *Special use only.See Table 310-2(a). **For dry locations only.See Table 310-2(a). These ampacities relate only to conductors described in Table 310-2(a). t The ampacities for Types FEP, FEPB, RHH, THHN, and XHHW con- ductors for sizes AWG 14, 12 and 10 shall be the same as designated for 75°C conductors in this Table. For ambient temperatures over 30°C,see Correction Factors,Note-15. m ARTICLE 310—CONDUCTORS 70-105 Table 310-13. Allowable Ampacities of Insulated Copper Conductors Single Conductor in Free Air (Based on Ambient Temperature of 30°C. 86°F.) Size Temperature Rating of Conductor.See Table 310-2(a) AWG 60°C 75°C 85°C 90°C 110°C 125°C 200°C MCM (140°F) (167°F) (185°F) (194°F) (230°F) (257°F) (392°F) TYPES TYPES TYPES TYPES TYPES TYPES TYPES Bare RUW RH, V, TA, AVA, AI A and (14-2), RHW, MI TBS, AVL (14-8), (14-8), Covered T, RUH SA, AIA AA, Conduc- TW (14-2), AVB, FEP* tors THW, SIS, FEPB* THWN FEP, XHHW FEPB, RHH, I THHN, XHHW** 14 20 20 30 30 t 40 40 45 30 12 25 25 40 40 t 50 50 55 40 10 40 40 55 55 t 65 70 75 55 8 55 65 70 70 85 90 100 70 6 80 95 100 100 120 125 135 100 4 105 125 135 135 160 170 180 130 3 120 145 155 155 180 195 210 150 2 140 170 180 180 210 225 240 175 1 165 195 210 210 245 265 280 205 0 195 230 245 245 285 305 325 235 00 225 265 285 285 330 355 370 275 000 260 310 330 330 385 410 430 320 0000 300 360 385 385 445 475 510 370 250 340 405 425 425 495 530 .... 410 300 375 445 480 480 555 590 .... 460 350 420 505 530 530 610 655 .... 510 400 455 545 575 575 665 710 .... 555 500 515 620 660 660 765 815 .... 630 600 575 690 740 740 855 910 .... 710 700 630 755 815 815 940 1005 .... 780 750 655 785 845 845 980 1045 .... 810 800 680 815 880 880 1020 1085 .... 845 900 730 870 940 940 .... .. .... 905 1000 780 935 1000 1000 1165 1240 .... 965 1250 890 1065 1130 1130 .... .... .... .... 1500 980 1175 1260 1260 1450 .... .... 1215 1750 1070 1280 1370 1370 .... .... .... .... 2000 1155 1385 1470 1470 1715 .... .... 1405 *Special use only.See Table 310-2(a). **For dry locations only.See Table 310-2(a). These ampacities relate only to conductors described in Table 310-2(a). t The ampacities for Types FEP, FEPB, RHH, THHN, and XHHW con- ductors for sizes AWG 14, 12 and 10 shall be the same as designated for 75°C conductors in this Table. For ambient temperatures over 30°C,see Correction Factors,Note 15. 70-106 NATIONAL ELECTRICAL CODE Table 310-14. Allowable Ampacities of Insulated Aluminum Conductors Not More than Three Conductors in Raceway or Cable or Direct Burial (Based on Ambient Temperature of 30°C. 86°F.) Size Temperature Rating of Conductor.See Table 310-2(a) AWG 60°C 75°C 85°C 90°C 110°C 125°C 200°C MCM (140°F) (167°F) (185°F) (194°F) (230°F) (257°F) (392°F) TYPES TYPES TYPES TYPES TYPES TYPES TYPES RUW RH, V, TA, AVA, AI A (12-2), RHW, MI TBS, AVL (12-8), (12-8), T, RUH SA, AIA AA TW (12-2), AVB, THW, SIS, THWN RHH XHHW THHN XHHW** 12 15 15 25 25 t 25 30 30 10 25 25 30 30 t 35 40 45 8 30 40 40 40 45 50 55 6 40 50 55 55 60 65 75 4 55 65 70 70 80 90 95 3 65 75 80 80 95 100 115 *2 75 90 95 95 105 115 130 *1 85 100 110 110 125 135 150 *0 100 120 125 125 150 160 180 *00 115 135 145 145 170 180 200 *000 130 155 165 165 195 210 225 *0000 155 180 185 185 215 245 270 250 170 205 215 215 250 270 .... 300 190 230 240 240 275 305 .... 350 210 250 260 260 310 335 .... 400 225 270 290 290 335 360 .... 500 260 310 330 330 380 405 .... 600 285 340 370 370 425 440 .... 700 310 375 395 395 455 485 .... 750 320 385 405 405 470 500 .... 800 330 395 415 415 485 520 .... 900 355 425 455 455 .... .... .... 1000 375 445 480 480 560 600 .... 1250 405 485 530 530 .... .... 1500 435 520 580 580 650 .... .... 1750 455 545 615 615 .... .... .... 2000 470 560 650 650 705 .... .... These ampacities relate only to conductors described in Table 310-2(a). *For three wire, single phase service, the allowable ampacity of RH, RHH, RHW, and THW aluminum conductors shall be for sizes #2-100 Amp., #1-110 Amp., #1/0-125 Amp., #2/0-150 Amp., #3/0-170 Amp. and #4/0-200 Amp. **For dry locations only.See Table 310-2(a). t The ampacities for Types RHH,THHN,and XHHW conductors for sizes AWG 12 and 10 shall be the same as designated for 75°C conductors in this Table For ambient temperatures over 30°C,see Correction Factors,Note 15. ARTICLE 310—CONDUCTORS 70-107 Table 310-15. Allowable Ampacities of Insulated Aluminum Conductors Single Conductor in Free Air (Based on Ambient Temperature of 30°C. 86°F.) Size Temperature Rating of Conductor.See Table 310-2(a) AWG 60°C 75°C 85°C 90°C 110°C 125°C 200°C MCM (140°F) (167°F) (185°F) (194°F) (230°F) (257°F) (392°F) TYPES TYPES TYPES TYPES TYPES TYPES TYPES Bare RUW RH, V, TA, AVA, AI A and (12-2), RHW, MI TBS, AVL (12-8), (12-8), overed T, RUH SA, AIA AA onduc- TW (12-2), AVB, THW SIS, tors THWN RHH, XI-IHW THHN, XHHW* 12 20 20 30 30 t 40 40 45 30 10 30 30 45 45 t 50 55 60 45 8 45 55 55 55 65 70 80 55 6 60 75 80 80 95 100 105 80 4 80 100 105 105 125 135 140 100 3 95 115 120 120 140 150 165 115 2 110 135 140 140 165 175 185 135 1 130 155 165 165 190 205 220 160 0 150 180 190 190 220 240 255 185 00 175 210 220 220 255 275 290 215 000 200 240 255 255 300 320 335 250 0000 230 280 300 300 345 370 400 290 250 265 315 330 330 385 415 .... 320 300 290 350 375 375 435 460 .... 360 350 330 395 415 415 475 510 .... 400 400 355 425 450 450 520 555 .... 435 500 405 485 515 515 595 635 .... 490 600 455 545 585 585 675 720 .... 560 700 500 595 645 645 745 795 .... 615 750 515 620 670 670 775 825 .... 640 800 535 645 695 695 805 855 .... 670 900 580 700 750 750 .... .... .... 725 1000 625 750 800 800 930 990 .... 770 1250 710 855 905 905 .... .... .... .... 1500 795 950 1020 1020 1175 .... .... 985 1750 875 1050 1125 1125 .... .... .... .... 2000 960 1150 1220 1220 1425 .... .... 1165 These ampacities relate only to conductors described in Table 310-2(a). *For dry locations only.See Table 310-2(a). t The ampacities for Types RHH,THHN,and XHHW conductors for sizes AWG 12 and 10 shall be the same as designated for 75°C conductors in this Table. For ambient temperatures over 30°C,see Correction Factors,Note 15. 70-108 NATIONAL ELECTRICAL CODE 310-20 Simplified Wiring Table. The Simplified Wiring Table, Table 310-21, may be used for the selection of feeder and branch circuit con- 4 ductor sizes and insulation types only under the conditions stated in this Section. The Simplified Wiring Table shall be used only when a demand factor of 80 per cent or less exists. (a) Application of Table 310-21. (1) Determine load amperes, either continuous or noncontinuous. [Sec.310-20(b).] (2) Select conductor sizes from Table 310-21. (3) Determine ambient temperature. Use 30°C (86°F) except where higher ambients may be expected as covered in Section 310-20(c). (4) Select wire insulation type from Table 310-20(c) and Section 310-2(a). Table 310-20(c). Typical Ambient Temperatures Minimum Rating of Required Location Temperature Conductor Insulation Well ventilated, 30°C (86°F) *(See note below) normally heated buildings Buildings with 45°C(113°F) 75°C(167°F) such major heat sources as power stations or in- dustrial processes Poorly ventilated 45°C(113°F) 75°C (167°F) spaces such as attics Furnaces and boiler rooms (min.) 40°C(104°F) 75°C(167°F) (max.) 60°C(140°F) 90°C(194°F) Outdoors in shade in air 40°C(104°F) 75°C(167°F) In thermal insula- tion 45°C(113°F) 75°C(167°F) Direct solar exposure 45°C(113°F) 75°C (167°F) Places above 60°C(140°F) 110°C(230°F) *Note: 60°C for up to and including No. 8 AWG copper and up to and including No. 6 AWG aluminum. 75°C for over No. 8 AWG copper and No.6 AWG aluminum. ARTICLE 310—CONDUCTORS 70-109 (b) Loads. (1) Continuous. Continuous loads are expected to continue for three hours or longer[see Section 210-23(b).] (2) Noncontinuous. Loads are noncontinuous where 67 per cent or less of the load is expected to be continuous. Table 310-21. Simplified Wiring Table (See Section 310-20 for use) Conductor Size*-6 or Fewer Conductors in Raceway or Cable Copper Aluminum Am- Non-Cont. Continuous Non-Cont. Continuous peres AWG MCM AWG MCM AWG MCM AWG MCM 15 14 14 12 12 20 12 12 10 10 25 10 10 8 8 30 10 10 8 8 35 8 8 6 6 40 8 8 6 6 45 6 6 4 4 50 6 6 4 4 60 4 4 4 4 70 4 4 3 3 80 3 3 3 2 90 3 2 2 1 100 2 1 1 0 110 1 0 0 2/0 125 1 0 2/0 3/0 150 0 2/0 3/0 4/0 175 2/0 3/0 4/0 250 200 3/0 4/0 250 300 225 4/0 250 300 350 250 250 300 350 400 300 350 400 400 750 350 400 500 500 1000 400 500 750 750 450 750 1000 1000 500 750 1000 600 1000 * Neutral conductors shall be treated in accordance with Note 11—Neu- tral Conductors of Notes to Tables 310-12 through 310-15. 70-110 NATIONAL ELECTRICAL CODE (c) Ambient Temperature. Ambient temperature is the temperature of the medium, such as air, water or earth, into which the heat of the conductor is dissipated. Ambient temperatures vary and values typical of the installation condition shall be used for determining the type of conductor insulation when applying the Simplified Wiring Table. See Table 310-20(c). (d) Conductors in Air. For ampacities of single conductors in air, use Tables 310-13 and 310-15. 310-21. Conductor Ampacity. In Table 310-21 the values of amperes apply to actual diversified continuous or noncontinuous connected loads. This Table shall not be used to determine conductor ampacity;use Tables 310-12 to 310-15 for this purpose. ARTICLE 318 — CONTINUOUS RIGID CABLE SUPPORTS 318-1. Definition. A continuous rigid cable support is a unit or an as- sembly of units or sections, and associated fittings, made of metal or other noncombustible materials forming a continuous rigid structure used to support cables. Continuous rigid cable supports include ladders, troughs,channels,and other similar structures. It is not the intent of this Article to require that cables be supported by continuous rigid cable supports or to recognize the use of conduc- tors described in Article 310 in continuous rigid cable supports for general wiring. 318-2. Use. (a) Continuous rigid cable supports may be used as the mechanical support for only the following wiring methods under the conditions de- tailed in the Article for each wiring method:(1)Mineral-insulated metal- sheathed cables, (Article 330), (2) Aluminum sheathed cable, (Article 331), (3) Metal-clad cable, (Article 334), (4) Nonmetallic sheathed cable, (Article 336), (5) Multiple conductor service-entrance cables, (Article 338), (6) Multiple conductor underground feeder and branch circuit cable, (Article 339), (7) Any approved conduit or raceway with its contained conductors. (b) Continuous rigid cable supports may be used as the mechanical support for factory-assembled,multiconductor control,signal,and power cables, which are specifically approved for installation in Continuous Rigid Cable Supports, in fire-resistive or non-combustible construction, but shall not be used (1) in hoistways, (2) where the cables supported are subject to severe physical damage, (3) in areas having readily com- bustible contents as determined by the authority enforcing this Code. Continuous Rigid Cable Supports may be used to support cables in hazardous locations when the cables are specifically approved for such use. (Refer to Sections 501-4, 502-4,and 503-3.) 318-3. Construction. Continuous Rigid Cable Supports shall be ap- proved for the purpose and shall comply with the following: ARTICLE 318—CABLE SUPPORTS 70-111 (1) Shall have suitable strength and rigidity to provide adequate support for all contained wiring. (2) Shall not present sharp edges, burrs or projections injurious to the insulation or jackets of the wiring. (3) If made of metal, shall be adequately protected against cor- rosion or shall be made of corrosion-resistant material. (4) Shall have side rails or equivalent structural members. (5) Shall include fittings for changes in direction and elevation of runs. 318-4. Installation. (a) Continuous Rigid Cable Supports shall be installed as a complete support system. (b) Each run of continuous rigid cable support shall be complete be- fore the installation of cables. (c) Continuous rigid cable supports shall be mechanically connected to any enclosure or raceway into which the cables contained in the continuous rigid cable support extend or terminate. (d) In portions of runs where additional physical protection is re- quired, noncombustible covers or enclosures providing the required protection shall be used. (e) Installations involving different electrical systems shall comply with Section 300-3 and, where separation is required, the separation shall be a solid noncombustible partition or compartment. Where ca- bles, as permitted by Section 318-2(b), are installed in the same con- tinuous rigid cable support as the cables permitted by Section 318-2 (a),the requirements of this section shall apply. (f) When continuous rigid cable supports are installed in tiers, the minimum vertical clearance between tiers shall be 12 inches. - (g) Continuous rigid cable supports may extend transversely through partitions or walls, other than fire walls, provided the section of the support within the wall is continuous and unventilated. See Section 300-21. Exception: Where an opening in a partition or wall provides two inches minimum clearance above and on both sides, the continuous rigid cable support may be of a ventilated type. (h) Continuous rigid cable supports may extend vertically through dry floors and platforms provided the continuous rigid cable support is totally enclosed where it passes through the floor or platform open- ing and for a distance of six feet above the floor or platform to provide protection from physical injury.See Section 300-21. 70-112 NATIONAL ELECTRICAL CODE (i) Continuous rigid cable supports may extend vertically through floors and platforms in wet locations where (1) there are curbs or other suitable means to prevent water flow through the floor or platform opening and (2) the continuous rigid cable support is totally enclosed where it passes through the floor or platform opening and for a distance of six feet above the floor or platform to provide protection from physi- cal injury.See Section 300-21. (j) Cable splices and cable taps shall be made only in junction boxes or fittings approved for the purpose. (k) In other than horizontal runs, and where side rails do not pro- vide adequate containment of the cables, they shall be fastened se- curely to transverse members of the continuous rigid cable support. (I) Where continuous rigid cable supports are located adjacent to one another an adequate working space of 24 inches minimum should be maintained on one side of each continuous rigid cable support, or where grouped in rows adjacent to each other a minimum working space of 32 inches should be maintained over each continuous rigid cable support. (m) Except as provided in Section 318-4(g), a minimum vertical clearance of 6 inches should be maintained from the top of the con- tinuous rigid cable support to all ceilings, beams, and other obstructions. 318-5. Grounding. All metal sections of continuous rigid cable sup- ports and fittings shall be bonded and effectively grounded to provide a continuous circuit for fault current. A continuous rigid cable support system shall not be used either as a grounded circuit conductor or as an equipment grounding conductor.See Section 250-33. 318-6. Ampacity. The ampacities of cables installed in continuous rigid cable supports shall be as follows: (a) Where cables containing not more than three current-carrying conductors are installed in ventilated continuous rigid cable supports and spacing is maintained at from one-quarter to one cable diameter, the factors of Table 318-6 (a) shall be applied to the ampacities of the cables used. Table 318-6(a) Factors for Cables with Maintained Spacing Number of Horizontally Cables 1 2 3 4 5 6 Vertically 1 1.00 0.93 0.87 0.84 0.83 0.82 2 0.89 0.83 0.79 0.76 0.75 0.74 3 0.80 0.76 0.72 0.70 0.69 0.68 4 0.77 0.72 0.68 0.67 0.66 0.65 5 0.75 0.70 0.66 0.65 0.64 0.63 6 0.74 0.69 0.64 0.63 0.62 0.61 ARTICLE 320—OPEN WIRING 70-113 (b) The ampacities of cables shall be in accordance with the require- ments of Note 8 of Notes to Tables 310-12 through 310-15 where (1) cables are not spaced, (2) spacing is maintained between cables of more than three current-carrying conductors, or (3) unventilated con- tinuous rigid cable supports are used. ARTICLE 320—OPEN WIRING ON INSULATORS 320-1. Definition. Open wiring is a wiring method using cleats, knobs, tubes and flexible tubing for the protection and support of in- sulated conductors run in or on buildings, and not concealed by the building structure. 320-2. Use. (a) Open wiring on insulators may be used for exposed work, either inside or outside building; in dry or wet locations; where subject to corrosive vapors such as covered by Article 480; for services as covered by Article 230, provided the requirements of this Article are satisfied. (b) Open wiring on insulators shall not be used (1) in commercial garages, (2) in theaters, (3) in motion-picture studios, (4) in hoistways, and (5) in hazardous locations,except in storage compartments of Class III locations as provided in Section 503-3(b). 320-3. Other Articles. In addition to the provisions of this Article, open wiring shall conform to the other applicable provisions of this Code.See especially Articles 300 and 730. 320-4. Conductors. The type of conductors shall conform to Article 310. Only single conductors shall be used. (a) The allowable ampacities of insulated conductors as shown in Article 310 shall apply to open wiring on insulators. 320-5. Supports. (a) Conductors shall not be in contact with any object other than their insulating supports. They shall be rigidly supported on noncom- bustible,nonabsorptive insulating material as follows: (1) Under ordinary circumstances, supports for wiring over flat surfaces shall be not more than 41/2 feet apart. Where the conductors are likely to be disturbed, the distance between supports shall be short- ened sufficiently to provide adequate support for conductors; (2) Conductors shall be supported within 6 inches of a tap; (3) Conductors shall not be dead ended at a rosette, lampholder, or receptacle unless the last support is within 12 inches of the device. (b) The following exceptions to the provisions of Section 320-5(a) may be permitted: Exception No. 1. For use of nonmetallic flexible tubing, see Sec- tion 320-7. Exception No. 2. Conductors of No. 8 or larger installed in the open across open spaces where not likely to be disturbed, may be sup- 70-114 NATIONAL ELECTRICAL CODE ported at distances not greater than 15 feet provided that approved noncombustible, nonabsorptive insulating separators assuring not less than 21/2-inch separation between conductors, are installed at inter- vals of not over 41/2 feet. Exception No.3.In buildings of mill construction where not likely to be disturbed, feeders in the open, not smaller than No. 8, may be separated about six inches and installed direct from timber to timber, being supported from each timber only. (c) When nails are used to mount knobs they shall not be smaller than 10 penny. When screws are used to mount knobs, or when nails or screws are used to mount cleats, they shall be of a length sufficient to penetrate the wood to a depth equal to at least one-half the height of the knob and fully the thickness of the cleat. Cushion washers shall be used with nails. 320-6. Conductor Separation. Open conductors shall be separated as follows: (a) For voltage not exceeding 300 volts between conductors, 21 inches from each other and shall be separated from the surface wired over at least 1/2 inch in dry locations. (b) For voltages of 301 to 600 volts between conductors, 4 inches from each other and shall be separated from surface wired over at least 1 inch. (c) In damp or wet locations, a separation of at least 1 inch from the surface wired over shall be maintained for all voltages. 320-7. Flexible Nonmetallic Tubing. In dry locations, when not ex- posed to severe physical damage, conductors may be separately en- cased in flexible tubing. Tubing shall be in continuous length not ex- ceeding 15 feet, and secured to the surface wired over by straps spaced not exceeding 41 feet apart. 320-8. Tie Wires. No. 8 or larger conductors supported on solid knobs shall be securely tied thereto. Tie wires shall have a covering equivalent to conductors which they confine. 320-9. Passing Through Walls and Floors. Open conductors shall be separated from contact with walls, floors, timbers or partitions through which they pass by tubes or bushings of noncombustible, nonabsorp- tive insulating material. Where the bushing is shorter than the hole, a waterproof sleeve of noninductive material shall be inserted in the hole and an insulating bushing slipped into the sleeve at either end in such a manner as to keep the conductors absolutely out of contact with the sleeve. Each conductor must be carried through a separate tube or sleeve. 320-10. Separation from Metal Work. Open conductors shall be sep- arated at least 2 inches from metallic conduit, piping, or other con- ducting material, and from any exposed lighting, power or signal con- ductor, or shall be separated therefrom by a continuous and firmly fixed nonconductor additional to the insulation of the conductor. Where any insulating tube is used, it shall be secured at the ends. De- viation from this requirement may, when necessary, be allowed by the authority enforcing this Code. ARTICLE 320—OPEN WIRING 70-115 320-11. Separation from Piping in Damp Locations. Open conductors located close to water pipes or tanks, or in other damp locations, shall be so placed that an air space will be permanently maintained between them and pipes which they cross. Where practicable, conductors shall be installed over,rather than under, pipes upon which moisture is likely to gather or which may leak. 320-12. Protection from Physical Damage. Where open conductors cross ceiling joists and wall studs, and are exposed to physical dam- age, they shall be protected by one of the following methods. Conduc- tors within 7 feet from the floor shall be considered exposed to physi- cal damage. (a) By guard strips not less than %s inch in thickness and at least as high as the insulating supports, placed on each side of and close to the wiring. (b) By a substantial running board at least 1/2 inch thick back of the conductors with side protections. Running boards shall extend at least 1 inch outside the conductors, but not more than 2 inches and the protecting sides shall be at least 2 inches high and at least 7/8 inch thick. (c) By boxing made as above and furnished with cover kept at least 1 inch away from the conductors within. Where protecting vertical conductors on side walls the boxing shall be closed at the top and the holes through which the conductors pass shall be bushed. (d) By rigid metal conduit or electrical metallic tubing, in which case the rules of Articles 346 or 348 shall apply; or by metal piping, in which case the conductors shall be encased in continuous lengths of approved flexible tubing. The conductors passing through metal en- closures shall be so grouped that current in both directions is approxi- mately equal. 320-13. In Accessible Attics. Conductors in unfinished attics or roof spaces shall be installed in accordance with the provisions of Section 324-8. 320-14. Entering Spaces Subject to Dampness, Wetness or Corrosive Vapors. Conductors entering or leaving locations subject to dampness, wetness or corrosive vapors shall have drip loops formed on them and shall then pass upward and inward from the outside of buildings, or from the damp, wet, or corrosive location, through noncombustible, nonabsorptive insulating tubes.See also Sections 230-49 and 730-21. 320-15. Switches. (a) Surface-type snap switches shall be mounted in accordance with the provisions of Section 380-10. Metal boxes are not required. See Section 380-3. (b) Other types of switches shall be installed in accordance with the provisions of Section 380-3. 70-116 NATIONAL ELECTRICAL CODE ARTICLE 324 — CONCEALED KNOB-AND-TUBE WORK 324-1. Definition. Concealed knob-and-tube wiring is a wiring method using knobs, tubes and flexible nonmetallic tubing for the protection and support of insulated conductors concealed in hollow spaces of walls and ceilings of buildings. 324-2. Use. Concealed knob-and-tube work may be used in the hol- low spaces of walls and ceilings. It shall not be used (1) in commercial garages, (2) in theaters, except as provided in Section 520-4, (3) in motion-picture studios,nor (4) in hazardous locations. 324-3. Other Articles. In addition to the provisions of this Article, concealed knob-and-tube wiring shall conform to the other applicable provisions of this Code.See especially Article 300. 324-4. Conductors. Only single conductors shall be used.The ampacity and type of conductor shall conform to Article 310. 324-5. Supports. Conductors shall be supported at intervals not ex- ceeding 41/2 feet by knobs or tubes of noncombustible, nonabsorptive, insulating material. There shall be a knob within 6 inches of each side of each tap or splice. Tie wires shall comply with Section 320-8. Where such support is impracticable and the conductors are in a dry location, they may be fished when separately enclosed in flexible nonmetallic tub- ing extending in continuous lengths from one support to the next or to a box,or from one box to another. 324-6. Conductor Separation. (a) Conductors shall be separated at least 3 inches and maintained at least 1 inch from the surface wired over. (b) At distributing centers, meters, outlets, switches or other places where space is limited and the 3-inch separation cannot be maintained, each conductor shall be encased in a continuous length of flexible tub- ing. (c) Where practicable, conductors shall be run singly on separate joists,rafters or studding. 324-7. Separation from Other Objects and Protection. Conductors shall be separated from other conductors and objects as follows: (a) The provisions as to rigid supporting and clearance from foreign wires and other objects, as specified for open wiring in Sections 320-9, 320-10, 320-11,and 320-15,shall be complied with. (b) Conductors passing through wood cross members in plastered partitions shall be protected by an additional noncombustible, nonab- sorptive insulating tube extending at least 3 inches above the member. 324-8. In Unfinished Attics and Roof Spaces. Conductors in unfinished attics or roof spaces shall comply with the following: (a) Conductors in unfinished attics and roof spaces shall be run through or on the sides of joists, studs and rafters, except in attics and roof spaces having head room at all points of less than 3 feet in build- ings completed before the wiring is installed. ARTICLE 328—BARE-CONDUCTOR FEEDERS 70-117 (b) Where conductors in accessible unfinished attics or roof spaces reached by stairway or permanent ladder are run through bored holes in floor joists or through bored holes in studs or rafters within 7 feet of the floor or floor joists, such conductors shall be protected by substan- tial running boards extending at least 1 inch on each side of the con- ductors and securely fastened in place. (c) Where carried along the sides of rafters, studs or floor joists, neither running boards nor guard strips will be required. 324-9. Boxes of Insulating Material. Nonmetallic outlet boxes may be used as provided in Sections 370-3 and 370-7. 324-10. Switches. See Sections 380-3 and 380-10. 324-11. Splices. Splices shall be made only where close to knobs or tubes using solder or specially approved splicing devices. In line or strain splices shall not be used. ARTICLE 328—BARE-CONDUCTOR FEEDERS 328-1. Use. By special permission, bare conductors installed in ac- cordance with the provisions of Sections 300-1 to 300-22 inclusive and in accordance with the provisions of the following Sections 328-2 to 328-7 inclusive may be used for feeders only. Such bare conductors may be installed only in a chase, channel or shaft of noncombustible material in a building of fire-resistive construction; and only where the voltage between conductors does not exceed 600 volts. Bare conductors shall not be used in damp or wet locations, nor in any hazardous loca- tion, nor where subject to corrosive vapor, except in storage-battery rooms as provided in Section 480-7. 328-2. Size and Capacity of Copper Conductors. The maximum per- missible current shall be 1000 amperes per square inch of cross-sec- tional area of conductor in unventilated enclosures, and 1200 amperes per square inch in ventilated enclosures. These provisions are not in- tended to apply to equipment such as controls and switchgear. 328-3. Branch Taps. Branch taps from bare-conductor feeders may be installed as specified in Section 240-15; provided that the mechani- cal protection specified by Exceptions No. 5 and 6 of Section 240-15 shall not be required for that portion of the conductor located in the chase,channel or shaft. 328-4. Accessibility. The conductors shall not be accessible to other than qualified persons. 328-5. Supports. Conductors shall be supported as follows: (a) Conductors shall be supported on noncombustible, nonabsorp- tive insulating supports of adequate mechanical strength. (b) Conductors shall be so supported that a separation between con- ductors, and between conductors and ground, of not less than that specified in Section 384-26 will be maintained under all conditions of operation. 70-118 NATIONAL ELECTRICAL CODE 328-6. Fire Cutoffs. Where floors are pierced, suitable cutoffs against vertical travel of fire shall be provided.See also Section 300-21. 328-7. Special Safeguards. In addition to the provisions of the pre- ceding sections, the authority enforcing this Code may require other safeguards in view of special conditions that may be met in a particular installation. ARTICLE 330—MINERAL INSULATED-METAL SHEATHED CABLE Type MI A. General 330-1. Definition and Construction. For the purpose of this Article, mineral insulated-metal sheathed Type MI cable is a cable in which one or more electrical conductors are insulated with a highly com- pressed refractory mineral insulation and enclosed in a liquidtight and gastight metallic tube sheathing. It shall be used with approved fittings for terminating and connecting to boxes,outlets and other equipment. 330-2. Use. Mineral insulated-metal sheathed cable may be used for services, feeders and branch circuits in both exposed and concealed work, in dry or wet locations; in Class I, Class II, and Class III hazard- ous locations as noted in the appropriate Articles; for under plaster ex- tensions as provided in Article 344; and embedded in plaster finish on brick or other masonry. It may be used where exposed to weather or continuous moisture, for underground runs and embedded in masonry, concrete or fill, in buildings in course of construction or where exposed to oil, gasoline, or other conditions not having a deteriorating effect on the metal sheath. The sheath of mineral insulated-metal sheathed cable exposed to destructive corrosive conditions, such as some types of cin- der fill,shall be protected by materials suitable for those conditions. 330-3. Other Articles. In addition to the provisions of this Article, the installation of mineral insulated-metal sheathed cable shall comply with the other applicable provisions of this Code. See especially Article 300. B. Installation 330-4. Supports. Mineral insulated-metal sheathed cable shall be se- curely supported by approved staples, straps, hangers or similar fit- tings, so designed and installed as not to injure the cable. Cable shall be secured at intervals not exceeding 6 feet except where cable is fished. 330-5. Through Studs,Joists and Rafters. See Section 300-8. 330-6. Wet Locations. See Section 300-5. 330-7. Bends. All bends shall be so made that the cable will not be damaged and the radius of the curve of the inner edge of any bend shall be not less than 5 times the diameter of the cable. ARTICLE 331—ALUMINUM SHEATHED CABLE 70-119 330-8. Terminating Seal. At all points where mineral insulated-metal sheathed cable terminates an approved seal shall be provided imme- diately after stripping to prevent entrance of moisture into the mineral insulation. The conductors extending beyond the sheath shall be in- sulated with an approved insulating material. 330-9. Fittings. When Type MI cable is connected to boxes or equip- ment, the fittings shall be approved"for the conditions of service. When single conductor Type MI cables enter metal boxes through separate openings,refer to Section 300-20. 330-10. Insulation Resistance. The completed wiring system shall be tested for insulation resistance in accordance with Section 110-20. C. Construction Specifications 330-11. General. Type MI Cable for 600 volts shall conform to the following: (a) Conductors. The conductors are solid copper and have cross sectional areas corresponding to the standard American Wire Gage sizes. (b) Insulation. The insulation is a highly compressed refractory mineral which provides proper spacing for the conductors. (c) Outer Sheath. The outer sheath shall be of a continuous copper construction to provide mechanical protection and a moisture seal, and an adequate path for grounding purposes. ARTICLE 331—ALUMINUM SHEATHED CABLE Type ALS A. General 331-1. Definition and Construction. Aluminum sheathed type ALS cable is a factory assembled cable consisting of one or more insulated conductors enclosed in an impervious, continuous, closely fitting tube of aluminum. It shall be used with approved fittings for terminating and connecting to boxes,outlets and other equipment. 331-2. Use. Aluminum sheathed cable may be used in both exposed and concealed work, in dry or wet locations. The sheath of aluminum sheathed cable exposed to destructive corrosive conditions such as en- vironments containing strong chlorides or caustic alkalis, or where vapors of chlorine or hydrochloric acid are present or where the cable is installed underground, shall be protected by materials suitable for those conditions.See Section 300-5. Aluminum sheathed cable and fittings shall not be embedded or buried directly in concrete or used in areas subject to severe corrosive influences unless suitable supplemental corrosion protection is provided. See Section 310-6. 70-120 NATIONAL ELECTRICAL CODE 331-3. Other Articles. In addition to the provisions of this Article, the installation of aluminum sheathed cable shall comply with the other applicable provisions of this Code.See especially Article 300. B. Installations 331-4. Supports. Aluminum sheathed cable shall be securely sup- ported by staples, straps, hangers, or similar fittings so designed and installed as not to injure the cable. Cable shall be secured at intervals not exceeding 6 feet except where the cable is fished. 331-5. Through Studs,Joists and Rafters. See Section 300-8. 331-6. Wet Locations. See Section 300-5. 331-7. Bends. All bends shall be so made that the cable will not be damaged and the radius of the curve on the inner edge of any bend shall be not less than: (a) Ten times the external diameter of the sheath for cable not more than 3/4 inch in external diameter. (b) Twelve times the external diameter of the sheath for cable more than 3/4 inch but not more than 11 inches in external diameter;and (c) Fifteen times the external diameter of the sheath for cable more than 1 1 inches in external diameter. 331-8. Fittings. When aluminum sheathed cable is connected to boxes or equipment, the fittings shall be approved for the conditions of serv- ice. When single conductor aluminum sheathed cables enter metal boxes through separate openings refer to Section 300-20. C. Construction 331-9. General. Type ALS cable shall conform to the following: (a) Conductors. The conductors shall be copper or electrical con- ductor (EC) grade aluminum,solid or stranded. (b) Insulation. The insulation shall be a type listed in Table 310-2(b). (c) Insulation Covering. The covering over the insulation shall be the same as permitted for lead sheathed cable or multiple conductor cable. (d) Outer Sheath. The outer sheath shall be of a continuous, closely fitting tube of aluminum to provide mechanical protection, a moisture seal and an adequate path for equipment grounding purposes and shall conform with provisions of Section 331-2. The sheath shall not be used as a current-carrying conductor. ARTICLE 334—METAL-CLAD CABLE Type MC and AC Series 334-1. Definition. A metal-clad cable is a fabricated assembly of in- sulated conductors in a flexible metallic enclosure.See Section 334-4. ARTICLE 334—METAL-CLAD CABLE 70-121 334-2. Voltage. See Section 300-2. For systems in excess of 600 volts see Article 710. 334-3. Marking. The provisions of Section 310-2 shall apply, except that AC cable shall have ready identification of the maker by distinctive external markers in the cable sheath throughout its entire length. 334-4. Construction. Metal-clad cable shall be an approved cable of Type MC or AC Series, with acceptable metal covering. The insulated conductors shall conform with Section 334-5. (a) Type MC. Type MC cables are power cables limited in size, for the voltages of this article,to conductors of No. 4 AWG and larger for copper and No. 2 AWG and larger for aluminum.The metal enclosures shall be either a covering of interlocking metal tape, or an impervious, close fitting, corrugated tube. Supplemental protection of an outer cov- ering of corrosion-resistant material shall be required where such pro- tection is needed. See Section 300-5. The cables shall provide adequate path for grounding purposes. (b) Type AC. Type AC cables are branch circuit and feeder cables with armor of flexible metal tape. Cables of the AC type, except ACL, shall have an internal bonding strip of copper or aluminum, in intimate contact with the armor for its entire length. 334-5. Conductors. Conductors for metal-clad cable shall conform with the following: (a) Type MC. For cables of Type MC, insulated conductors shall be of a type listed in Table 310-2(b) for rubber, thermoplastic, var- nished cloth, asbestos-varnished cloth, or of a type especially approved for the purpose. (b) Type AC. For cables of Type AC, insulated conductors shall be of a type listed in Table 310-2(b). In addition, the conductors shall have an over-all moisture-resistant and fire-retardant fibrous covering; for Type ACT, a moisture-resistant fibrous covering is required only on the individual conductors. 334-6. Use. Except where otherwise specified elsewhere in this Code, and where not subject to physical damage, metal-clad cable may be in- stalled for branch circuits and feeders in both exposed and concealed work as follows: (a) Type MC. This type of power cable may be used in partially protected areas, such as in continuous rigid cable supports and the like, in dry locations and when any of the following conditions are met it may be used in wet locations: (1) The metallic covering is impervious to moisture. (2) A lead sheath or moisture impervious jacket is provided un- der the metal covering. (3) The insulated conductors under the metallic covering are ap- proved for use in wet locations. See Section 300-5. (b) Type AC. Metal-clad cable of the AC type may be used in dry locations; for under plaster extensions as provided in Article 344; and 70-122 NATIONAL ELECTRICAL CODE embedded in plaster finish on brick or other masonry, except in damp or wet locations. This cable may be run or fished in the air voids of masonry block or tile walls;where such walls are exposed or subject to excessive moisture or dampness or are below grade line, Type ACL cable shall be used. This cable shall contain lead-covered conductors (Type ACL), if used where exposed to the weather or to continuous moisture, for underground runs and embedded in masonry, concrete or fill in buildings in course of construction, or where exposed to oil, or other conditions having a deteriorating effect on the insulation. Type AC metal-clad cable shall not be used where prohibited elsewhere in this Code,including (1) in theatres,except as provided in Section 520-4; (2) in motion-picture studios; (3) in any hazardous locations; (4) where exposed to corrosive fumes or vapors; (5) on cranes or hoists,except as provided in Section 610-11 Exception No. 3; (6) in storage battery rooms; (7) in hoistways or on elevators, except as provided in Section 620-21;or (8) commercial garages where prohibited in Article 511. 334-7. Other Articles. In addition to the provisions of this Article, metal-clad cable shall conform to other applicable provisions of this Code.See especially Article 300. 334-8. Supports. Metal-clad cable shall be secured by approved sta- ples, straps, hangers or similar fittings so designed and installed as not to injure the cable. (a) Type MC cable shall be secured at intervals not exceeding six feet, and within two feet from every box or fitting, except where cable is fished. Cable may be installed on metal racks, trays, troughs, or con- tinuous rigid cable supports grounded as required by Article 250. The cables shall be separated from each other by a distance of not less than one-quarter of a cable diameter. There shall be no more than one layer of cables on a rack or other support member; each cable so installed shall be supported at intervals not exceeding six feet and within two feet from every box or fitting, and each cable shall be attached to the support at intervals of not more than ten feet horizontally and two feet vertically. (b) Type AC cable shall be secured at intervals of not exceeding 41 feet and within 12 inches from every outlet box or fitting, except where cable is fished and except lengths of not over 24 inches at terminals where flexibility is necessary. 334-9. Bends. All bends shall be so made that the cable will not be injured, and the radius of the curve of the inner edge of any bend shall not be less than 7 times the diameter of Type MC cable nor 5 times the diameter of Type AC cable. 334-10. Boxes and Fittings. (a) At all points where Type MC metal-clad cable terminates, suit- able fittings designed for use with the particular wiring cable and the conditions of service,shall be used. (b) At all points where the armor of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and in addition, an approved insulating bushing or its equivalent ap- ARTICLE 336—NONMETALLIC SHEATHED CABLE 70-123 proved protection shall be provided between the conductors and the armor. The connector or clamp by which the metal-clad cable is fas- tened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. This bushing is not required with lead-covered cables which shall be so installed that the lead sheath will be visible for inspection. Where change is made from metal-clad cable to other cable or raceway wiring methods, a box shall be installed at junction point as required in Section 300-15. 334-11. Through Studs,Joists and Rafters. See Section 300-8. 334-12. Exposed Work. Exposed runs of cable shall closely follow the surface of the building finish or of running boards,except: (a) Lengths of not more than 24 inches at terminals where flexibility is necessary. (b) Where suitably supported in accordance with Section 334-8(a). (c) On the underside of floor joists in basements where supported at each joist and so located as not to be subject to physical damage. 334-13. In Accessible Attics. Type AC cables in accessible attics or roof spaces shall be installed as follows: (a) Where run across the top of floor joists, or within 7 feet of floor or floor joists across the face of rafters or studding, in attics and roof spaces which are accessible, the cable shall be protected'by substantial guard strips which are at least as high as the cable. Where this space is not accessible by permanent stairs or ladders,protection will only be re- quired within 6 feet of the nearest edge of scuttle hole or attic entrance. (b) Where cable is carried along the sides of rafters, studs or floor joists,neither guard strips nor running boards shall be required. ARTICLE 336—NONMETALLIC SHEATHED CABLE Types NM and NMC 336-1. Definition. A nonmetallic sheathed cable is an assembly of two or more insulated conductors having an outer sheath of moisture-re- sistant,flame-retardant,nonmetallic material. 336-2. Construction. Nonmetallic sheathed cable shall be an approved Type NM or NMC in sizes No. 14 through 2 AWG with copper con- ductors and in sizes No. 12 through 2 with aluminum conductors. In ad- dition to the insulated conductors, the cable may have an approved size of uninsulated or bare conductor for grounding purposes only. (a) Type NM. The conductors shall comply with the requirements for the type of conductor used. Over-all fibrous coverings shall have a flame-retardant and moisture-resistant finish. (b) Type NMC. The cable shall be of a type approved for the pur- pose. The over-all covering shall be flame-retardant, moisture-resistant, fungus-resistant and corrosion-resistant. 70-124 NATIONAL ELECTRICAL CODE (c) Marking. In addition to the provisions of Section 310-2, the ca- ble shall have a distinctive marking on the exterior for its entire length specifying cable type. 336-3. Use. Nonmetallic sheathed cable may be installed for both ex- posed and concealed work as follows: (a) Type NM. This type of nonmetallic sheathed cable may be in- stalled for both exposed and concealed work in normally dry locations. It may be installed or fished in air voids in masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness. Type NM cable shall not be installed where exposed to cor- rosive fumes or vapors; nor shall it be imbedded in masonry, concrete, fill or plaster;nor run in shallow chase in masonry or concrete and cov- ered with plaster or similar finish. (b) Moisture and Corrosion-Resistant Type NMC. This type of non- metallic sheathed cable may be installed for both exposed and con- cealed work in dry, moist, damp or corrosive locations, and in outside and inside walls of masonry block or tile. Where embedded in plaster or run in a shallow chase in masonry walls and covered with plaster within 2 inches of the finished surface, it shall be protected against damage from nails by a cover of corrosion-resistant coated steel at least 1/16 inch in thickness and 3/4 inch wide in the chase or under the final surface finish. (c) Uses Not Permissible for Either Type NM or NMC Nonmetallic Sheathed Cable. These types shall not be used as: (1) service-entrance cable, (2) in commercial garages, (3) in theatres except as provided in Section 520-4, (4) in motion picture studios, (5) in storage battery rooms, (6) in hoistways, (7) in any hazardous location, (8) embedded in poured cement,concrete or aggregate. 336-4. Other Articles. In addition to the provisions of this Article, installations of nonmetallic sheathed cable shall conform to the other applicable provisions of this Code.See especially Article 300. 336-5. Supports. Nonmetallic sheathed cable shall be secured by ap- proved staples, straps, or similar fittings, so designed and installed as not to injure the cable. Cable shall be secured in place at intervals not exceeding 41/2 feet and within 12 inches from every cabinet, box or fitting, except that in concealed work in finished buildings or finished panels for prefabricated buildings where such supporting is impractica- ble,the cable may be fished between points of access. 336-6. Exposed Work—General. In exposed work, except as provided in Sections 336-8 and 336-9,the cable shall be installed as follows: (a) The cable shall closely follow the surface of the building finish or of running boards. (b) It shall be protected from physical damage where necessary, by conduit, pipe, guard strips or other means. Where passing through a floor the cable shall be enclosed in rigid metal conduit or metal pipe ex- tending at least 6 inches above the floor. 336-7. Through Studs,Joists and Rafters. See Section 300-8. ARTICLE 338—SERVICE-ENTRANCE CABLE 70-125 336-8. In Unfinished Basements. Where the cable is run at angles with joists in unfinished basements, assemblies not smaller than two No. 6 or three No. 8 conductors may be secured directly to the lower edges of the joists; smaller assemblies shall either be run through bored holes in the joists or on running boards. Where run parallel to joists, cable of any size shall be secured to the sides or face of the joists. 336-9. In Accessible Attics. Cable in accessible attics or roof spaces shall also conform with Section 334-13. 336-10. Bends. Bends in cable shall be so made, and other handling shall be such, that the protective coverings of the cable will not be in- jured, and no bend shall have a radius less than 5 times the diameter of the cable. 336-11. Devices of Insulating Material. Switch, outlet, and tap devices of insulating material may be used without boxes in exposed cable wiring, and for concealed work for rewiring in existing buildings where the cable is concealed and fished. Openings in such devices shall form a close fit around the outer covering of the cable and the device shall fully enclose that part of the cable from which any part of the cover- ing has been removed. Where connections to conductors are by binding screw terminals, there shall be available as many terminals as conductors, unless cables are clamped within the structure and terminals are of a type approved for multiple conductors. 336-12. Boxes of Insulating Material. Nonmetallic outlet boxes ap- proved for the purpose may be used as provided in Section 370-3. ARTICLE 338—SERVICE-ENTRANCE CABLE Types SE and USE 338-1. Definition. Service-entrance cable is a conductor assembly pro- vided with a suitable over-all covering, primarily used for services and of the following types. When consisting of two or more conductors, one may be without individual insulation. (a) Type SE, having a flame-retardant, moisture-resistant covering, but not required to have inherent protection against mechanical abuse. (b) Type USE, recognized for underground use, having a moisture- resistant covering, but not required to have a flame-retardant covering or inherent protection against mechanical abuse.Single conductor cables having rubber insulation specifically approved for the purpose do not require an outer covering. 338-2. Use as Service Entrance Conductors. Service-entrance cable used as service-entrance conductors shall be installed as required by Article 230. 338-3. Use as Branch Circuit or Feeders. (a) Type SE, service-entrance cables may be used in interior wiring 70-126 NATIONAL ELECTRICAL CODE systems where all of the circuit conductors of the cable are of the rub- ber-covered or thermoplastic type. (b) Type SE, service-entrance cables without individual insulation on the grounded circuit conductor shall not be used as a branch circuit or as a feeder within a building, except a cable which has a final nonmetallic outer covering and when supplied by alternating current at not exceed- ing 150 volts to ground,may be used: (1) As a branch circuit to supply only a range, wall-mounted oven, counter-mounted cooking unit, or clothes dryer as covered in Section 250-60, or (2) as a feeder to supply only other buildings on the same premises. It shall not be used as a feeder terminating within the same building in which it originates. The above provisions do not intend to deny the use of service-entrance cable for interior use when the fully insulated conductors are used for cir- cuit wiring and the uninsulated conductor is used for equipment grounding purposes. (c) Type SE, service-entrance cable used to supply appliances shall not be subject to conductor temperatures in excess of the temperature specified for the type of insulation involved. 338-4. Installation Methods. (a) In addition to the provisions of this Article, Type SE service-en- trance cable used for interior wiring shall comply with the applicable provisions of Article 300. (b) Unarmored cable shall be installed in accordance with the ap- plicable provisions of Article 336. (c) Cables through studs,joists and rafters shall be installed as re- quired in Section 300-8. 338-5. Marking. Service-entrance cable shall conform with the mark- ing required in Section 310-2. Cable with the neutral conductor smaller than the ungrounded conductors shall be so marked. ARTICLE 339—UNDERGROUND FEEDER AND BRANCH CIRCUIT CABLE Type UF 339-1. Description and Marking. (a) Description. Underground feeder and branch circuit cable shall be an approved Type UF cable in sizes No. 14 to No. 4/0 AWG, in- clusive. The conductors shall be Types TW, RHW, or other conduc- tors approved for the purpose. In addition to the insulated conductors, the cable may have an approved size of uninsulated or bare conductor for grounding purposes only. The over-all covering shall be flame- retardant, moisture-resistant, fungus-resistant and corrosive-resistant, and suitable for direct burial in the earth. (b) Marking. In addition to the provisions of Section 310-2, the cable shall have a distinctive marking on the exterior for its entire length specifying cable type. ARTICLE 342—NONMETALLIC EXTENSIONS 70-127 339-2. Other Articles. In addition to the provisions of this Article, installations of underground feeder and branch circuit cable (Type UF) shall comply with other applicable provisions of this Code. See especially Article 300,and Section 310-2(b). 339-3. Use. (a) Underground feeder and branch circuit cable may be used un- derground, including direct burial in the earth, as feeder or branch cir- cuit cable when provided with overcurrent protection of the rated ampacity as required in Section 339-4. (b) Where single conductor cables are installed, all cables of the feeder circuit, sub-feeder circuit, or branch circuit, including the neu- tral conductor, if any, shall be run together in the same trench or race- way. (c)A minimum depth of 18 inches shall be maintained for conductors and cables buried directly in the earth.This depth may be reduced to 12 inches provided supplemental protective covering such as a 2 inch con- crete pad, metal raceway, pipe or other suitable protection is used. (d) Type UF cable may be used for interior wiring in wet, dry, or corrosive locations under the recognized wiring methods of this Code, and when installed as nonmetallic sheathed cable it shall conform with the installation provisions of Article 336 and shall be of the multiple conductor type, except where recognized under the provisions of Sec- tion 424-43. Type UF cable supported by continuous rigid cable sup- ports shall be of the multiple conductor type. (e) This type of cable shall not be used: (1) as service-entrance ca- bles; (2) in commercial garages;,(3) in theaters except as provided in Section 520-4; (4) in motion picture studios; (5) in storage battery rooms; (6) in hoistways; (7) in any hazardous location; (8) embedded in poured cement, concrete or aggregate, except where recognized in Article 422; (9) when exposed to direct rays of the sun, unless ap- proved for the purpose. 339-4. Overcurrent Protection. Overcurrent protection shall be pro- vided in accordance with provisions of Section 240-5. 339-5. Rated Ampacity. The ampacities of conductors in Type UF cable shall be according to Tables 310-12 and 310-14. ARTICLE 342—NONMETALLIC EXTENSIONS 342-1. Description. Nonmetallic extensions are an assembly of two insulated conductors within a nonmetallic jacket or an extruded ther- moplastic covering. The classification includes both surface extensions, intended for mounting directly on the surface of walls or ceilings, and aerial cable, containing a supporting messenger cable as an integral part of the cable assembly. 342-2. Other Articles. In addition to the provisions of this Article, nonmetallic extensions shall conform to other applicable provisions of this Code. 70-128 NATIONAL ELECTRICAL CODE 342-3. Use Permitted. Nonmetallic extensions may be used only where all of the following conditions are met: (a) The extension is from an existing outlet on a 15 or 20 ampere branch circuit in conformity with the requirements of Article 210. (b) The extension is run exposed and in a dry location. (c) For nonmetallic surface extensions, the building is occupied for residential or office purposes. (d) For aerial cable, the building is occupied for industrial pur- poses, and the nature of the occupancy requires a highly flexible means for connecting equipment. 342-4. Use Prohibited. Nonmetallic extensions shall not be installed: (a) As aerial cable to substitute for one of the general wiring meth- ods specified by this Code. (b) In unfinished basements,attics,or roof spaces. (c) Where voltage between conductors exceeds 150 volts for non- metallic surface extension and 300 volts for aerial cable. (d) Where subject to corrosive vapors. (e) Where run through a floor or partition, or outside the room in which it originates. 342-5. Splices and Taps. Extensions shall consist of a continuous un- broken length of the assembly, without splices, and without exposed conductors between fittings. Taps may be made where approved fittings completely covering the tap connections are used. Aerial cable and its tap connectors shall be provided with an approved means for polariza- tion.Receptacle type tap connectors shall be of the locking type. 342-6. Fittings. Each run shall terminate in a fitting which covers the end of the assembly.All fittings and devices shall be of a type approved for the purpose. 342-7. Installation. Nonmetallic extensions shall be installed in con- formity with the following requirements: (a) Nonmetallic Surface Extensions. (1) One or more extensions may be run in any direction from an existing outlet,but not on the floor or within 2 inches from the floor. (2) Nonmetallic surface extensions shall be secured in place by approved means at intervals not exceeding 8 inches, except that where connection to the supplying outlet is made by means of an attachment plug the first fastening may be placed 12 inches or less from the plug. There shall be at least one fastening between each two adjacent outlets supplied. An extension shall be attached only to woodwork or plaster finish, and shall not be in contact with any metal work or other con- ductive material except with metal plates on receptacles. (3) A bend which reduces the normal spacing between the conduc- tors shall be covered with a cap to protect the assembly from physical damage. ARTICLE 344—UNDERPLASTER EXTENSIONS 70-129 (b) Aerial Cable. (1) Aerial cable shall be supported by its messenger cable, securely attached at each end with approved clamps and turnbuckles. Interme- diate supports shall be provided at not more than 20 foot intervals. Cable tension shall be adjusted to eliminate excessive sag. The cable shall have a clearance of not less than 2 inches from steel structural members or other conductive material. (2) Aerial cable shall have a clearance of not less than 10 feet above floor areas accessible to pedestrian traffic, and not less than 14 feet above floor areas accessible to vehicular traffic. (3) Cable suspended over work benches, not accessible to pedes- trian traffic, shall have a clearance of not less than 8 feet above the floor. (4) Aerial cable may serve to support lighting fixtures when the total load on the supporting messenger cable does not exceed that for which the assembly is intended. (5) The supporting messenger cable, when conforming to the ap- plicable provisions of Article 250 and when properly identified as a grounding conductor, may be used for the grounding of equipment. The messenger cable shall not be used as a branch circuit conductor. ARTICLE 344—UNDERPLASTER EXTENSIONS 344-1. Use. An underplaster extension installed as permitted by this Article, may be used only for extending an existing branch circuit in a building of fire-resistive construction. 344-2. Materials. Such extensions shall be run in rigid or flexible con- duit, Type AC metal-clad cable, electrical metallic tubing, Type MI cable or metal raceways approved for the purpose. Standard sizes of conduit, cable, tubing and raceways shall be used except that for a single conductor only conduit or tubing having not less than 5/16 inch inside diameter, single-conductor Type AC metal-clad cable or single conductor Type MI cable may be used. 344-3. Box and Fittings. See Article 370. 344-4. Installation. An underplaster extension shall be laid on the face of masonry or other material and buried in the plaster finish of ceilings or walls. The methods of installation of the raceway or cable for such extension shall be as specified elsewhere in this Code for the particular type of material used. 344-5. Extension to Another Floor. No such extension shall extend beyond the floor on which it originates unless installed in a standard size of rigid metal conduit, electrical metallic tubing, Type AC metal- clad cable,or MI cable. 70-130 NATIONAL ELECTRICAL CODE ARTICLE 346—RIGID METAL CONDUIT Note: Where conduit is threaded in the field, it is assumed that a stand- ard conduit cutting die providing 3/ inch taper per foot will be employed. 346-1. Use. Rigid metal conduit may be used under all atmospheric conditions and occupancies, except that ferrous raceways and fittings protected from corrosion solely by enamel may be used only indoors and in occupancies not subject to severe corrosive influences. Where practicable dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of galvanic action. Unless made of a material judged suitable for the condition, or un- less corrosion protection approved for the condition is provided, ferrous !! or non-ferrous metallic conduit, elbows, couplings, and fittings shall not be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences. 346-2. Other Articles. Installations of rigid metal conduit shall comply with the provisions of the applicable Sections of Article 300. A. Installation 346-3. Cinder Fill. Conduit, unless of corrosion-resistant material suitable for the purpose shall not be used in or under cinder fill where subject to permanent moisture unless protected on all sides by a layer of noncinder concrete at least 2 inches thick or unless the conduit is at least 18 inches under the fill. 346-4. Wet Locations. All supports, bolts, straps, screws, etc., shall be of corrosion-resistant materials or protected against corrosion by approved corrosion-resistant materials. See Section 300-5. 346-5. Minimum Size. No conduit smaller than l inch, electrical trade size, shall be used, except as provided for underplaster extensions in Article 344, and for enclosing the leads of motors as permitted in Section 430-145(b). 346-6. Number of Conductors in Conduit. The number of conductors permitted in a single conduit shall be as follows: (a) New Work: (1) Where conductors are all of the same size, use Tables 1 and 2 of Chapter 9. (2) Where conductors are of various sizes to be used in combina- tion,use Tables 3 and 4 of Chapter 9 and the dimensions in Columns 3, 5, 7, 9, or 11 of Table 5 of Chapter 9. Where bare conductors are per- mitted by other Sections of this Code, the dimensions for bare conduc- tors in Table 8 of Chapter 9 may be used. (b) Rewiring Existing Conduits: (1) For rewiring existing conduits where conductors are all of the same size use Table 1A of Chapter 9. ARTICLE 346—RIGID METAL CONDUIT 70-131 (2) Where conductors are of various sizes to-be used in combina- tion use Tables 3 and 4 of Chapter 9, and the dimensions of Columns 3,5,7, 9,or 11 of Table 5,Chapter 9. Where bare conductors are permitted by other Sections of this Code, the dimensions for bare conductors in Table 8 of Chapter 9 may be used. 346-7. Reaming. All cut ends of conduits shall be reamed to remove rough edges. 346-8. Bushings. Where a conduit enters a box or other fitting, a bushing shall be provided to protect the wire from abrasion unless the design of the box or fitting is such as to afford equivalent protection. See Section 373-6(b) for the protection of conductors at bushings. 346-9. Couplings and Connectors. (a) Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be of the concrete-tight type, or where installed in wet locations, shall be of the raintight type. (b) Running threads shall not be used on conduit for connection at couplings. 346-10. Bends — How Made. Bends of rigid conduit shall be so made that the conduit will not be injured, and that the internal diameter of the conduit will not be effectively reduced. The radius of the curve of the inner edge of any field bend shall not be less than shown in Table 346-10(a). Exception: For field bends for conductors without lead sheath and made with a single operation (one shot) bending machine designed for the purpose, the minimum radius may be in accordance with Table 346-10(b). Table 346-10(a) Radius of Conduit Bends Conductors Conductors Size of Without With Conduit Lead Sheath Lead Sheath 1/2 in. 4 in. 6 in. 3/4 in. 5 in. 8 in. 1 in. 6 in. 11 in. 11/4 in. 8 in. 14 in. 11/2 in. 10 in. 16 in. 2 in. 12 in. 21 in. 21/2 in. 15 in. 25 in. 3 in. 18 in. 31 in. 31/2 in. 21 in. 36 in. 4 in. 24 in. 40 in. 41 in. 27 in. 45 in. 5 in. 30 in. 50 in. 6 in. 36 in. 61 in. 70-132 NATIONAL ELECTRICAL CODE Table 346-10(b) Radius of Conduit Bends Size of Radius to Conduit Center of Conduit 1 in. 4 in. 3/4 in. 41/2 in. 1 in. 53/4 in. 11/4 in. 71/4 in. 11 in. 81/4 in. 2 in. 91/2 in. 21 in. 101/2 in. 3 in. 13 in. 31 in. 15 in. 4 in. 16 in. 41/2 in. 20 in. 5 in. 24 in. 6 in. 30 in. 346-11. Bends— Number in One Run. A run of conduit between outlet and outlet, between fitting and fitting, or between outlet and fitting shall not contain more than the equivalent of 4 quarter bends (360 degrees, total), including those bends located immediately at the outlet or fitting. 346-12. Supports. Rigid metal conduit shall be installed as a complete system as provided in Article 300 and shall be securely fastened in place. Conduit shall be firmly fastened within 3 feet of each outlet box, junction box, cabinet, or fitting. Conduit shall be supported at least every ten feet except that straight runs of rigid conduit made up with approved threaded couplings may be secured in accordance with Table 346-12, provided such fastening prevents transmission of stresses to terminus when conduit is deflected between supports. Table 346-12. Supports for Rigid Metal Conduit Maximum distance between rigid metal Conduit Size conduit supports (Inches) (feet) 1/2—3/4 10 1 12 11/4-1/h 14 2-21/2 16 3 and larger 20 ARTICLE 347—RIGID NONMETALLIC CONDUIT 70-133 346-13. Boxes and Fittings. See Article 370. B. Construction Specifications 346-14. General. Rigid metal conduit shall conform to the following: (a) Rigid conduit as shipped shall be in standard lengths of 10 feet including coupling, one coupling to be furnished with each length. Each length shall be reamed and threaded on each end. For specific applica- tions or uses, lengths shorter or longer than 10 feet, with or without couplings,may be shipped. (b) Nonferrous conduit of corrosion-resistant material shall have suitable markings. (c) Each length shall be clearly and durably identified in every 10 feet as required in the first sentence of Section 110-21. ARTICLE 347—RIGID NONMETALLIC CONDUIT 347-1. Description. The provisions of this Article shall apply to a type of conduit and fittings of suitable nonmetallic material which is resist- ant to moisture and chemical atmospheres. For use above ground, it shall also be flame retardant, resistant to impact and crushing, shall re- sist distortion due to heat under conditions likely to be encountered in service and shall be resistant to low temperature and sunlight effects. For use underground, the material shall be acceptably resistant to moisture and corrosive agents and shall be of sufficient strength to withstand abuse, such as by impact and crushing, in handling and dur- ing installation. Where intended for direct burial, without encasement in concrete, the material shall also be capable of withstanding con- tinued loading which is likely to be encountered after installation. Materials which have been recognized as having suitable physical charac- teristics when properly formed and treated include fiber, asbestos cement, soapstone, rigid polyvinyl chloride and high density polyethylene for under- ground use and rigid polyvinyl chloride for use above ground. 347-2. Use Permitted. Rigid nonmetallic conduit and fittings ap- proved for the purpose may be used under the following conditions and where the potential is 600 volts or less except as noted in Section 347-3. (a) Direct earth burial not less than 18 inches below the surface. If less than 18 inches it shall be encased in not less than 2 inches of con- crete. (b) In concrete walls,floors and ceilings. (c) In locations subject to severe corrosive influences as set forth in Section 300-5 and where subject to chemicals for which the materials are specifically approved. (d) Cinder fill. (e) Wet Locations. In portions of dairies, laundries, canneries or other wet locations and in locations where walls are frequently washed, 70-134 NATIONAL ELECTRICAL CODE the entire conduit system including boxes and fittings used therewith shall be so installed and equipped as to prevent water from entering the conduit. All supports, bolts, straps, screws, etc., shall be of corrosion- resistant materials or protected against corrosion by approved corro- sion-resistant materials. (f) In dry and damp locations not prohibited by Section 347-3. 347-3. Use Prohibited. Rigid nonmetallic conduit shall not be used: (a) In hazardous locations except as covered in Sections 514-8 and 515-5. (b) In the concealed spaces of combustible construction. (c) For the support of fixtures or other equipment. (d) Where subject to physical damage unless approved for the pur- pose. (e) Where subject to ambient temperatures exceeding those for which the conduit had been approved. (f) For conductors whose insulation temperature limitations would exceed those for which the conduit had been approved. (g) For potentials exceeding 600 volts unless encased in not less than 2 inches of concrete. (h) In the sunlight unless approved for the purpose. 347-4. Other Articles. Installation of rigid nonmetallic conduit shall comply with provisions of the applicable sections of Article 300. A. Installations 347-5. Trimming. All cut ends shall be trimmed inside and outside to remove rough edges. 347-6. Joints. All joints between lengths of conduit, and between conduit and couplings, fittings and boxes shall be made by a method specifically approved for the purpose. Table 347-8 Support of Rigid Nonmetallic Conduit Conduit Size Maximum Spacing between Supports Inches Feet 1-3/a 4 1-2 5 21-3 6 3' —5 7 6 8 ARTICLE 347—RIGID NONMETALLIC CONDUIT 70-135 347-8. Supports. Rigid nonmetallic conduit shall be adequately sup- ported as required in Table 347-8. In addition, there shall be a support within 4 feet of each box,cabinet or other conduit termination. 347-9. Expansion Joints. Expansion joints for rigid nonmetallic con- duit shall be provided where required to compensate for thermal ex- pansion and contraction. 347-10. Minimum Size. No conduit smaller than 1/2 inch electrical trade size shall be used. 347-11. Number of Conductors. The number of conductors permitted in a single conduit shall be as follows: (a) New Work: (1) Where conductors are all of the same size, Tables 1 and 2 of Chapter 9. (2) Where conductors are of various sizes to be used in combina- tion, use Tables 3 and 4 of Chapter 9 and the dimensions of conductors in Columns 3, 5, 7, 9, or 11 of Table 5 of Chapter 9. Where bare con- ductors are permitted by other Sections of this Code, the dimensions for bare conductors in Table 8 of Chapter 9 may be used. (3) When equipment grounding is required by Article 250, a sep- arate grounding conductor shall be installed in the conduit. (b) Rewiring Existing Conduits: (1) For rewiring existing conduits where conductors are all of the same size use Table 1A of Chapter 9. (2) Where conductors are of various sizes to be used in combina- tion use Tables 3 and 4 of Chapter 9 and the dimensions of Columns 3, 5, 7, 9 or 11 of Table 5, Chapter 9. Where bare conductors are per- mitted by other Sections of this Code, the dimensions for bare conduc- tors in Table 8 of Chapter 9 may be used. 347-12. Bushings. Where a conduit enters a box or other fitting, a bushing or adapter shall be provided to protect the wire from abrasion unless the design of the box or fitting is such as to provide equivalent protection. See Section 373-6(b) for the protection of conductors at bushings. 347-13. Bends, How Made. Bends of rigid nonmetallic conduit shall be so made that the conduit will not be injured and that the internal diameter of the conduit will not he effectively reduced. Field bends shall be made only with bending equipment specifically approved for the purpose, and the radius of the curve of the inner edge of such bends shall be not less than shown in Table 346-10(a). 347-14. Bends, Number in One Run. A run of conduit between outlet and outlet, between fitting and fitting or between outlet and fitting shall not contain more than the equivalent of four quarter bends (360°) total including those bends located immediately at the outlet or fitting. 347-15. Boxes and Fittings. See Article 370. 70-136 NATIONAL ELECTRICAL CODE B. Construction Specifications 347-16. General. Rigid nonmetallic conduit shall conform to the fol- lowing: (a) Rigid nonmetallic polyvinyl chloride conduit as shipped shall be in standard lengths of 10 feet including couplings, one coupling to be furnished with each length. For specific applications or uses, lengths shorter or longer than 10 feet with or without couplings may be shipped. (b) High density polyethylene conduit as shipped shall be in standard lengths of 10 feet. One threaded coupling shall be furnished with each threaded length of high density polyethylene conduit. For specific ap- plications or uses, lengths shorter or longer than 10 feet with or without it couplings may be shipped. (c) Each length of nonmetallic conduit shall be clearly and durably marked at least every ten feet as required in the first sentence of Section 110-21. The type of material shall also be included in the marking un- less it is visually identifiable. For conduit recognized for use above ground these markings shall be permanent. For conduit limited to underground use only, these mark- ings shall be sufficiently durable to remain legible until the material is installed. ARTICLE 348—ELECTRICAL METALLIC TUBING 348-1. Use. Electrical metallic tubing may be used for both exposed and concealed work. Electrical metallic tubing protected from cor- rosion solely by enamel shall not be used. Electrical metallic tubing shall not be used (1) where during installation or afterward, it will be subject to severe physical damage; (2) in cinder concrete or fill where subject to permanent moisture unless protected on all sides by a layer of noncinder concrete at least 2 inches thick or unless the tubing is at least 18 inches under the fill. Where practicable, the use of dissimilar metals throughout the system shall be avoided to eliminate the possibil- ity of galvanic action. Unless made of a material judged suitable for the condition, or un- less corrosion protection approved for the condition is provided, ferrous or nonferrous electrical metallic tubing, elbows, couplings and fittings shall not be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences. 348-2. Other Articles. Installations of electrical metallic tubing shall comply with the provisions of the applicable sections of Article 300. A. Installation 348-4. Wet Locations. All supports, bolts, straps, screws, etc. shall be of corrosion-resistant materials or protected against corrosion by ap- proved corrosion-resistant materials.See Section 300-5. ARTICLE 348—ELECTRICAL METALLIC TUBING 70-137 348-5. Minimum and Maximum Sizes. No tubing smaller than I/z inch, electrical trade size, shall be used except as provided for underplaster extensions in Article 344 and for enclosing the leads of motors as per- mitted in Section 430-145(b). The maximum size of tubing shall be the 4-inch electrical trade size. 348-6. Number of Conductors in Tubing. One tubing shall not contain more conductors than as provided in Section 346-6. 348-7. Threads. Tubing shall not be coupled together nor connected to boxes, fittings, or cabinets by means of threads in the wall of the tub- ing, except by fittings approved for the purpose.Threads shall not be of the standard pipe thread dimensions. 348-8. Couplings and Connectors. Threadless couplings and connec- tors used with tubing shall be made up tight. Where buried in masonry or concrete, they shall be concrete-tight type, or where installed in wet locations,shall be of the raintight type. 348-9. Bends— How Made. Bends in the tubing shall be so made that the tubing will not be injured and that the internal diameter of the tub- ing will not be effectively reduced. The radius of the curve of the inner edge of any field bend shall not be less than shown in Table 346-10(a). Exception:For field bends made with a bending machine designed for the purpose, the minimum radius may be in accordance with the dimen- sions of Table 346-10(b). 348-10. Bends— Number in One Run. A run of electrical metallic tub- ing between outlet and outlet, between fitting and fitting, or between outlet and fitting, shall not contain more than the equivalent of four quarter bends (360 degrees, total), including those bends located imme- diately at the outlet or fitting. 348-11. Reaming. All cut ends of electrical metallic tubing shall be reamed to remove rough edges. 348-12. Supports. Electrical metallic tubing shall be installed as a complete system as provided in Article 300 and shall be securely fas- tened in place at least every 10 feet and within 3 feet of each outlet box, junction box,cabinet,or fitting. 348-13. Boxes and Fittings. See Article 370. B. Construction Specifications 348-14. General. Electrical metallic tubing shall conform to the fol- lowing: (a) Cross Section. The tubing, and elbows and bends for use with the tubing,shall have a circular cross section. (b) Finish. Tubing shall have such a finish or treatment of outer surfaces as will provide an approved durable means of readily distin- guishing it,after installation,from rigid conduit. (c) Connectors. Where the tubing is coupled together by threads, the connector shall be so designed as to prevent bending of the tubing at any part of the thread. 70-138 NATIONAL ELECTRICAL CODE ARTICLE 350—FLEXIBLE METAL CONDUIT 350-1. Other Articles. Installations of flexible metal conduit shall comply with the appropriate (or applicable) provisions of Articles 300, 334,and 346. 350-2. Use. Flexible metal conduit shall not be used (1) in wet loca- tions, unless conductors are of the lead-covered type or of other type specially approved for the conditions; (2) in hoistways, except as pro- vided in Section 620-21; (3) in storage-battery rooms; (4) in any hazard- ous location except as permitted in Sections 501-4(b), 502-4 and 503-3; nor (5) where rubber-covered conductors are exposed to oil, gasoline, or other materials having a deteriorating effect on rubber. 350-3. Minimum Size. No flexible metal conduit less than one-half inch electrical trade size shall be used except (1) as permitted for un- derplaster extensions by Section 344-2; (2) as permitted for motors by I Section 430-145(b);and (3) for connection not over 72 inches in length, or longer on approved assemblies, to equipment where the use of one- half inch or larger size flexible metal conduit is not practicable, in which case flexible metal conduit of three-eighth inch electrical trade size may be used. Table 350-3. Maximum Number of Conductors in 3/4 inch Flexible Metal Conduit Types TF,T,TW,THHN, Size Types Type THWN,XHHW, AWG RF-2,RH RHW RUF,RUW 18 4 — 8 16 3 — 6 14 3 2 5 12 2 2 4 10 — — 3 350-4. Supports. When flexible metal conduit is installed it shall be secured by approved means at intervals not exceeding 41h feet and within 12 inches on each side of every outlet box or fitting,except where flexible conduit is fished,and except for lengths of not over 36 inches at terminals where flexibility is necessary. 350-5. Grounding. Flexible metal conduit may be used as a ground- ing means where both the conduit and the fittings are approved for the purpose. ARTICLE 351—LIQUIDTIGHT FLEXIBLE METAL CONDUIT 70-139 ARTICLE 351—LIQUIDTIGHT FLEXIBLE METAL CONDUIT 351-1. Purpose. Liquidtight flexible metal conduit is not intended as a general purpose raceway material. The provisions of this Article shall apply to a type of flexible conduit having an outer liquidtight jacket and employed with suitable terminal fittings approved for the purpose. 351-2. Use. The use of this wiring material shall be restricted as fol- lows: (a) For the connection of motors or portable and stationary equip- ment where flexibility of connection is required. (b) Liquidtight flexible metal conduit shall not be used under the fol- lowing conditions: (1) where subject to physical damage; (2) where in contact with rapidly moving parts; (3) under conditions such that its temperature, with or without enclosed conductors carrying current, is above 60°C (140°F); (4) in any hazardous location,except as described in Section 501-4(b) and Sections 502-4 and 503-3, unless it is specially approved for such use. 351-3. Maximum Size. The maximum size of liquidtight flexible metal conduit shall not exceed 3 inch electrical trade size. 351-4. Conductor Size. The maximum size of conductor installed in liquidtight flexible metal conduit shall not exceed the values shown in Table 351-4. Table 351-4. Maximum Conductor Size in Liquidtight Flexible Metal Conduit Trade Size of Conduit Size of Conductor N inch 16 Awg 1/2 inch 12 Awg 3/ inch 8 Awg 1 inch 6 Awg 11/4 inch 2 Awg 11 inch 1 Awg 2 inch 00 Awg 21/2 inch 0000 Awg 3 inch 350 MCM Liquidtight flexible metallic conduit in sizes 11/2 inch and larger shall be bonded in accordance with Section 250-79 unless specifically ap- proved for use without a separate bond. 70-140 NATIONAL ELECTRICAL CODE ARTICLE 352—SURFACE RACEWAYS Metal Raceways 352-1. Use. Surface metal raceways may be installed in dry locations. They shall not be used (1) where concealed, except that metal race- ways approved for the purpose may be used for underplaster exten- sions; (2) where subject to severe physical damage unless approved for the purpose; (3) where the voltage is 300 volts or more between con- ductors unless the metal has a thickness of not less than .040 inch; (4) where subject to corrosive vapors; (5) in hoistways; nor (6) in any hazardous location. 352-2. Other Articles. Installations of surface metal raceways shall comply with the applicable provisions of Article 300. A. Installation 352-3. Size of Conductors. No conductor larger than that for which the raceway is designed shall be installed in surface metal raceway. 352-4. Number of Conductors in Raceways. The number of con- ductors installed in any raceway shall be no greater than the number for which the raceway is designed. to 352-5. Extension Through Walls and Floors. Except in multioutlet as- semblies, raceways may be extended through dry walls, dry partitions and dry floors,if in unbroken lengths where passing through. 352-6. Combination Raceways. Where combination metal raceways are used both for signal and for lighting and power circuits,the different systems shall be run in separate compartments, identified by sharply contrasting colors of the interior finish, and the same relative position of compartments shall be maintained throughout the premises. B. Construction Specifications 352-7. General. Surface metal raceways shall be of such construction as will distinguish them from other raceways. Surface metal raceways and their elbows, couplings, and similar fittings shall be so designed that the sections can be electrically and mechanically coupled together, while protecting the wires from abrasion. Holes for screws or bolts in- side the raceway shall be so designed that when screws or bolts are in place their heads will be flush with the metal surface. Nonmetallic Raceways 352-21. Description. The provisions of the following Sections of this Article shall apply to a type of surface nonmetallic raceway and fittings of suitable nonmetallic material which is resistant to moisture and chemical atmospheres. It shall also be flame retardant, resistant to im- pact and crushing, shall resist distortion due to heat under conditions likely to be encountered in service and shall be resistant to low tem- perature effects. ARTICLE 353—MULTIOUTLET ASSEMBLY 70-141 352-22. Use. Surface nonmetallic raceways may be installed in dry locations. They shall not be used (1) where concealed; (2) where sub- ject to severe physical damage unless approved for the purpose; (3) where the voltage is 300 volts or more between conductors; (4) in hoistways; (5) in any hazardous location; (6) where subject to am- bient temperatures exceeding 50°C; nor (7) for conductors whose in- sulation temperature exceeds 75°C. 352-23. Other Articles. Installations of surface nonmetallic raceways shall comply with the applicable provisions of Article 300. A. Installation 352-24. Size of Conductors. No conductor larger than that for which the raceway is designed shall be installed in surface nonmetallic race- way. 352-25. Number of Conductors in Raceways. The number of conduc- tors installed in any raceway shall be no greater than the number for which the raceway is designed. 352-26. Combination Raceways. Where combination nonmetallic raceways are used both for signal and for lighting and power circuits, the different systems shall be run in separate compartments, identified by printed legend or by sharply contrasting colors of the interior finish, and the same relative position of compartments shall be maintained throughout the premises. B. Construction Specifications 352-27. General. Surface nonmetallic raceways shall be of such con- struction as will distinguish them from other raceways. Surface non- metallic raceways and their elbows, couplings, and similar fittings shall be so designed that the sections can be mechanically coupled together, while protecting the wires from abrasion. Holes for screws or bolts in- side the raceway shall be so designed that when screws or bolts are in place their heads will be flush with the nonmetallic surface. ARTICLE 353—MULTIOUTLET ASSEMBLY 353-1. Other Articles. Installations of multioutlet assembly shall com- ply with applicable provisions of Article 300. See definition in Article 100. 353-2. Use. Multioutlet assembly may be installed in dry locations. It shall not be installed (1) where concealed, except that the back and sides of metal multioutlet assembly may be surrounded by the building finish and nonmetallic multioutlet assembly may be recessed in the base- board; (2) where subject to severe physical damage unless approved for the purpose; (3) where the voltage is 300 volts or more between conduc- tors unless assembly is of metal having a thickness of not less than .040 inch; (4) where subject to corrosive vapors; (5) in hoistways;nor(6) in any hazardous locations. 70-142 NATIONAL ELECTRICAL CODE 353-3. Metal Multioutlet Assembly Through Dry Partitions. Metal multi- outlet assembly may be extended through (not run within) dry parti- tions, providing arrangements are made for removing the cap or cover on all exposed portions and no outlet is located within the parti- tions. ARTICLE 354—UNDERFLOOR RACEWAYS 354-1. Other Articles. Installations of underfloor raceways shall com- ply with the applicable provisions of Article 300. 354-2. Use. Underfloor raceways may be installed beneath the surface of concrete or other flooring material, or in office occupancies, where laid flush with the concrete floor and covered with linoleum or equiva- lent floor covering. Underfloor raceways shall not be installed (1) where subject to corrosive vapors nor (2) in any hazardous location. Unless made of a material judged suitable for the condition, or unless corro- sion protection approved for the condition is provided, ferrous or non- ferrous metallic underfloor raceways, junction boxes, and fittings shall not be installed in concrete; or in areas subject to severe corrosive in- fluences. 354-3. Covering. Raceway coverings shall conform to the following: (a) Raceways Not Over 4 Inches Wide. Half-round raceways not over 4 inches in width, and,except as permitted in (c) flat-top raceways not over 4 inches in width, shall have not less than 3/a inch of concrete or wood above the raceway. (b) Raceways Over 4 Inches Wide but Not Over 8 Inches Wide. Flat top raceways over 4 but not over 8 inches wide with a minimum of 1 inch spacing between raceways shall be covered with concrete to a depth of not less than 1 inch. Raceways spaced less than 1 inch apart shall be covered with concrete to a depth of 11/z inches. (c) Raceways Flush With Concrete. Approved flush raceways with re- movable covers may be laid flush with the floor surface. Such approved raceways shall be so designed that the cover plates will provide ade- quate mechanical protection and rigidity equivalent to junction box covers. 354-4. Size of Conductors. No conductor larger than that for which the raceway is designed shall be installed in underfloor raceways. 354-5. Number of Conductors in Raceway. The combined cross-sec- tional area of all conductors shall not exceed 40 per cent of the interior area of the raceway; except that where the raceway contains only ar- mored cable or nonmetallic sheathed cable,these requirements shall not apply. 354-6. Splices and Taps. Splices and taps shall be made only in junc • - tion boxes. For the purposes of this Section, so-called loop wiring (continuous, unbroken conductor connecting the individual outlets) is not considered to be a splice or tap. ARTICLE 356—CELLULAR METAL FLOOR RACEWAYS 70-143 354-7. Discontinued Outlets. When an outlet is abandoned, discontin- ued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conduc- tors such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways. 354-8. Laid in Straight Lines. Underfloor raceways shall be laid so that a straight line from the center of one junction box to the center of the next junction box will coincide with the center line of the raceway system. Raceways shall be firmly held in place to prevent disturbing this alignment during construction. 354-9. Markers at Ends. At every end of line of raceway, and at other locations where the location of the raceway is not apparent, a suitable number of markers shall be installed extending through the floor for fu- ture location of inserts and for system identification. 354-10. Dead Ends. Dead ends of raceways shall be closed. 354-11. Low Points. Where practicable, raceways and their fittings shall be so arranged as to avoid low points that may form traps for wa- ter. 354-12. Fittings at Angles. Where raceways are run at other than right angles,special fittings shall be provided. 354-13. Junction Boxes. Junction boxes shall be leveled to the floor grade and sealed against the entrance of water. Junction boxes used with metal raceways shall be metal and shall be electrically continuous with the raceways. 354-14. Inserts. Inserts shall be leveled to the floor grade and sealed against the entrance of water. Inserts used with metal raceways shall be metal and shall be electrically continuous with the raceway. Inserts set in or on fiber raceways before the floor is laid shall be mechanically secured to the raceway. Inserts set in fiber raceways after the floor is laid shall be screwed into the raceway. In cutting through the raceway wall and setting inserts, chips and other dirt shall not be allowed to fall into the raceway, and tools shall be used which are so designed as to prevent the tool from entering the raceway and injuring conductors that may be in place. 354-15. Connections to Cabinets and Wall Outlets. Connections be- tween raceways and distribution centers and wall outlets shall be made by means of rigid or flexible metal conduit or by means of fittings approved for the purpose. ARTICLE 356—CELLULAR METAL FLOOR RACEWAYS 356-1. Definitions. For the purposes of this Article, a "cellular metal floor raceway" shall be defined as the hollow spaces of cellular metal floors, together with suitable fittings, which may be approved as en- closures for electrical conductors; a "cell" shall be defined as a single, 70-144 NATIONAL ELECTRICAL CODE enclosed tubular space in a cellular metal floor member, the axis of the cell being parallel to the axis of the metal floor member; a "header" shall be defined as a transverse raceway for electrical conductors, pro- viding access to predetermined cells of a cellular metal floor, thereby permitting the installation of electrical conductors from a distribution center to the cells. 356-2. Use. Conductors shall not be installed in cellular metal floor raceways (1) where subject to corrosive vapor; (2) in any hazardous lo- cation;nor (3) in commercial garages,except for supplying ceiling out- lets or extensions to the area below the floor but not above. No electric conductors shall be installed in any cell or header which contains a pipe for steam,water,air,gas,drainage,or other service than electrical. 356-3. Other Articles. Installations of conductors in the raceways of cellular metal floor shall comply with the applicable provisions of Ar- ticle 300. A. Installation 356-4. Size of Conductors. No conductor larger than No. 0 shall be installed,except by special permission. 356-5. Number of Conductors in Raceway. The total cross-sectional area of all conductors in a header or in an individual cell shall not ex- ceed 40 per cent of the cross-sectional area of the header or cell in which they are located; except that where the raceway contains only Type AC metal-clad cable or nonmetallic sheathed cable, these require- ments shall not apply. 356-6. Splices and Taps. Splices and taps shall be made only in header access units or junction boxes. 356-7. Discontinued Outlets. When an outlet is discontinued, the con- ductors supplying the outlet shall be removed from the raceway. 356-8. Markers. A suitable number of markers shall be installed ex- tending through the floor for the future locating of cells and for system identification. 356-9. Junction Boxes. Junction boxes shall be levelled to the floor grade and sealed against the entrance of water. Junction boxes used with these raceways shall be of metal and shall be electrically continu- ous with the raceway. 356-10. Inserts. Inserts shall be levelled to the floor grade and sealed against the entrance of water. Inserts shall be of metal and shall be elec- trically continuous with the raceway. In cutting through the cell wall and setting inserts, chips and other dirt shall not be allowed to fall into the raceway, and tools shall be used which are designed to prevent the tool from entering the cell and injuring the conductors. 356-11. Connection to Cabinets and Extensions from Cells. Connections to cabinets and extensions from cells to outlets shall be made by means of rigid or flexible conduit or by means of fittings approved for the pur- pose. B. Construction Specifications 356-12. General. Cellular metal floor raceways shall be so constructed that adequate electrical and mechanical continuity of the complete sys- ARTICLE 357—STRUCTURAL RACEWAYS 70-145 tern will be secured. They shall provide a complete enclosure for the conductors. The interior surfaces shall be free from burrs and sharp edges, and surfaces over which conductors are drawn shall be smooth. Suitable bushings or fittings having smooth rounded edges shall be pro- vided where conductors pass. ARTICLE 357—STRUCTURAL RACEWAYS 357-1. Definitions. Structural raceways are formed steel members ap- proved for the installation of electrical wires or cables within them. (a) Vertical members used for studs or columns shall be tubes or channels. (b) Horizontal headers used as beams or top plates shall be provided with suitable covers,end closers,and fittings. 357-2. Use. Structural raceways used to enclose electrical conductors shall be used only in single-family dwellings. 357-3. Other Articles. Installation of conductors in structural race- ways shall comply with the applicable provisions of Article 300. A. Installation 357-4. Openings in Vertical Members. Vertical members may have openings provided in them for the purpose of installing wiring devices. Vertical members may be concealed. Openings in vertical members shall provide access to wiring. The size of such openings shall comply with the provisions of Section 300-15 and Article 370. Wiring devices may be installed in openings in vertical members without the use of individual boxes, provided that the back and sides of each device are surrounded by terminal barriers. 357-5. Horizontal Headers. Horizontal headers shall be securely fas- tened to vertical members. 357-6. Number of Conductors in Raceway. Structural raceways shall not contain more than 20 current-carrying conductors at any cross- section, and the total cross-sectional areas of all contained conductors shall not exceed 20 per cent of the interior cross-section. 357-7. Splices and Taps. Splices and taps shall be made only in hori- zontal headers, or junction boxes. The conductors including splices and taps shall not fill the structural raceway to more than 75 per cent of its area at that point. All splices and taps shall be made and insulated by approved methods. 357-8. Size of Conductors. No conductor larger than Number 6 AWG shall be installed in vertical or horizontal members. 357-9. Accessibility. The covers of the horizontal members shall be accessible after installation and shall not be obstructed by the wall fin- ish. 70-146 NATIONAL ELECTRICAL CODE } 357-10. Fittings. Fittings shall be designed and installed to prevent physical damage to electrical conductors. Fittings shall be free from burrs and sharp edges. 357-11. Extensions from vertical structural members. Extensions from vertical structural members shall be made with rigid or flexible metal conduit, electrical metallic tubing, surface metal raceway or metal- clad cable. 357-12. Dead Ends. Dead ends of structural raceways shall be closed. 357-13. Installation of Electrical Devices. The installation of switches, receptacles, and outlets shall be in accordance with the requirements of Articles 380 and 410,except as otherwise permitted in this Article. 357-14. Grounding. All elements of structural raceway systems shall be bonded and effectively grounded. B. Construction Specifications 357-15. Marking. Structural raceways and fittings shall be marked with the manufacturer's name,trademark,or identification symbol. 357-16. General. All metal components shall be properly coated to prevent corrosion. The interior shall be free from sharp edges and burrs. The structural raceway systems shall be constructed to provide electrical and mechanical continuity of the complete system. They shall provide a complete enclosure for the conductors. Enclosures shall be approved for the purpose. ARTICLE 358—CELLULAR CONCRETE FLOOR RACEWAYS 358-1. Scope. Approved precast cellular concrete floor raceways shall comply with the applicable requirements of Article 300, and shall also comply with the provisions of Sections 358-2 to 358-11 inclusive. For the purpose of this Article, "precast cellular concrete floor raceways" shall be defined as the hollow spaces in floors constructed of precast cellular concrete slabs, together with suitable metal fittings designed to provide access to the floor cells in an approved manner. A "cell" shall be defined as a single, enclosed tubular space in a floor made of precast cellular concrete slabs, the direction of the cell being parallel to the di- rection of the floor member. "Header ducts" shall be defined as trans- verse metal raceways for electrical conductors, furnishing access to predetermined cells of a precast cellular concrete floor, thus providing for the installation of electrical conductors from a distribution center to the floor cells. 358-2. Use. Conductors shall not be installed in precast cellular con- crete floor raceways (1) where subject to corrosive vapor; (2) in hazard- ous locations;nor (3) in commercial garages,except for supplying ceil- ing outlets or extensions to the area below the floor but not above. No electrical conductors shall be installed in any cell or header which con- ARTICLE 358—CELLULAR CONCRETE FLOOR RACEWAYS 70-147 tains a pipe for steam, water, air, gas, drainage, or any service other than electrical. 358-3. Header Duct. The header duct shall be installed in a straight line, at right angles to the cells. The header duct shall be mechanically secured to the top of the precast cellular concrete floor. The end joints shall be closed by metallic closure fittings and sealed against the pene- tration of water. The header duct shall be electrically continuous throughout its entire length and shall be electrically bonded to the en- closure of the distribution center. 358-4. Connection to Cabinets and Other Enclosures. Connection from header duct to cabinets and other enclosures shall be made by means of metallic duct and fittings approved for the purpose. 358-5. Junction Boxes. Junction boxes shall be levelled to the floor grade and sealed against the entrance of water. Junction boxes shall be of metal and shall be mechanically and electrically continuous with the header ducts. 358-6. Markers. Each hidden access point between a header and a cell intended for future use shall be provided with a marker extending through the floor covering. A suitable number of markers shall be in- stalled, extending through the floor covering, to locate the cells and to provide system identification. 358-7. Inserts. Inserts shall be levelled to the floor grade and sealed against the entrance of water. Inserts shall be of metal and shall be fitted with receptacles of the grounded type. A ground conductor shall connect the insert receptacles to a positive ground connection provided on the header duct. In cutting through the cell wall for setting inserts or other purposes (such as providing access openings between header duct and cells) chips and other dirt shall not be allowed to fall into the race- way, and the tool used shall be so designed as to prevent the tool from entering the cell and injuring the conductors. 358-8. Size of Conductors. No conductor larger than No. 0 shall be installed,except by special permission. 358-9. Number of Conductors. The total cross-sectional area of all con- ductors in a header or in an individual cell shall not exceed 40 per cent of the cross-sectional area of the header or cell in which they are located; except that where the raceway contains only Type AC metal-clad cable or nonmetallic sheathed cable,these requirements shall not apply. 358-10. Splices and Taps. Splices and taps shall be made only in header duct access units or junction boxes. 358-11. Discontinued Outlets. When an outlet is discontinued, the conductors supplying the outlet shall be removed from the header and cell. 70-148 NATIONAL ELECTRICAL CODE ARTICLE 362—WIREWAYS 362-1. Definition. Wireways are sheet-metal troughs with hinged or removable covers for housing and protecting electrical wires and cable and in which conductors are laid in place after the wireway has been installed as a complete system. 362-2. Use. Wireways may be installed only for exposed work. Wire- ways intended for outdoor use shall be of approved raintight construc- tion.Wireways shall not be installed: (1) where subject to severe physi- cal damage or corrosive vapor; nor (2) in any hazardous location ex- cept Class II,Division 2.See Section 502-4(b). 362-3. Other Articles. Installations of wireways shall comply with the applicable provisions of Article 300. 362-4. Size of Conductors. No conductor larger than that for which the wireway is designed shall be installed in any wireway. 362-5. Number of Conductors. Wireways shall not contain more than 30 current carrying conductors at any cross section. The sum of the cross-sectional areas of all contained conductors at any cross-section of a wireway shall not exceed 20 per cent of the interior cross-sectional area of the wireway. Exception No. 1.See Section 620-32. The correction factors specified in Note 8 to Tables 310-12 through 310-15 are not applicable to the foregoing. Exception No. 2. Conductors for signal circuits or controller con- ductors between a motor and its starter and used only for starting duty shall not be considered as current carrying conductors. Exception No. 3. When the correction factors specified in Note 8 of Tables 310-12 through 310-15 are applied, no limit on the number of current-carrying conductors is needed, but the sum of the cross sec- tional areas of all contained conductors at any cross section of the wire- way shall not exceed 20 per cent of the interior cross-sectional area of the wireway. Exception No.4.See Section 520-5. 362-6. Splices and Taps. Splices and taps, made and insulated by ap- proved methods, may be located within the wireway provided they are accessible. The conductors, including splices and taps, shall not fill the wireway to more than 75 per cent of its area at that point. 362-7. Supports. Wireways shall be securely supported at intervals not exceeding 5 feet, unless specially approved for supports at greater intervals, but in no case shall the distance between supports exceed 10 feet. Exception: Vertical runs of wireways shall be securely supported at intervals not exceeding 15 feet and shall have not more than one joint between supports.Adjoining wireway sections shall be securely fastened I together to provide a rigid joint. 1 i ARTICLE 364—BUSWAYS 70-149 362-8. Extension Through Walls. Wireways may extend transversely through walls if in unbroken lengths where passing through. 362-9. Dead Ends. Dead ends of wireways shall be closed. 362-10. Extensions From Wireways. Extensions from wireways shall be made with rigid or flexible metal conduit, electrical metallic tubing, surface metal raceway or metal-clad cable. 362-11. Marking. Wireways shall be marked so that their manufac- turer's name or trademark will be visible after installation. ARTICLE 364—BUSWAYS 364-1. Other Articles. Installations of busways shall comply with the applicable provisions of Article 300. 364-2. Use. Busways may be installed only for exposed work. Bus- ways shall not be installed (1) where subject to severe physical damage or corrosive vapors; (2) in hoistways; (3) in any hazardous location; nor (4) outdoors or in wet or damp locations unless specially approved for the purpose. Busways may be used for service-entrance conductors. See Section 230-44. It is recommended that where secondary systems are operated un- grounded, a combination ground detector and potentializer plug be used as an auxiliary fitting for busway systems to establish a definite potential dif- ference between the bus-bars and the grounded casing of the busways. This will serve to drain off any static.or other charge from the entire busway system including its connected apparatus, supply and branch circuit con- ductors. 364-3. Support. Busways shall be securely supported at intervals not exceeding 5 feet, unless specially approved for supports at greater in- tervals, but in no case shall the distance between supports exceed 10 feet. Where a busway is installed in a vertical position, the supports for the bus-bars shall be designed for vertical installation. 364-4. Extension Through Walls. Busways may extend transversely through dry walls if in unbroken lengths where passing through. Bus- ways may extend vertically through dry floors when totally enclosed (unventilated) where passing through and for a minimum distance of six feet above the floor to provide adequate protection from physical damage. 364-5. Dead Ends. A dead end of a busway shall be closed. 364-7. Branches from Busways. Branches from busways shall be made with busways or with rigid or flexible metal conduit, electrical metallic tubing, surface metal raceway, metal-clad cable or with suitable cord assemblies approved for hard usage for portable equipment or for the connection of stationary equipment to facilitate their interchange. 364-8. Overcurrent Protection. Overcurrent protection shall be pro- vided in accordance with Sections 364-9 to 364-13 inclusive. 70-150 NATIONAL ELECTRICAL CODE 364-9. Rating of Overcurrent Protection — Feeders and Sub-Feeders. Where the allowable current rating of the busway does not correspond to a standard rating of the overcurrent device, the next higher rating may be used. 364-10. Reduction in Size of Busway. Overcurrent protection may be omitted at points where busways are reduced in size, provided that the smaller busway does not extend more than 50 feet and has a current rating at least equal to one-third the rating or setting of the overcurrent device next back on the line, and provided further that such busway is free from contact with combustible material. 364-11. Branch Circuits. Where a busway is used as a feeder, devices or plug-in connections for tapping off branch-circuits from the busway shall contain the overcurrent devices required for the protection of the branch circuits. Exception No. 1. For overcurrent protection of taps, see Section 240-15. Exception No. 2. For fixed or semi-fixed lighting fixtures, the branch circuit overcurrent device may be part of the fixture cord plug on cord- connected fixtures. Exception No. 3. Where fixtures without cords are plugged directly into the busway,the overcurrent device may be mounted on the fixture. 364-12. Rating of Overcurrent Protection — Branch Circuits. A busway may be used as a branch circuit of any one of the types described in Article 210. When so used, the rating or setting of the overcurrent de- vice protecting the busway shall determine the ampere rating of the branch circuit, and the circuit shall in all respects conform with the re- quirements of Article 210 that apply to branch circuits of that rating. 364-13. Length of Busways Used as Branch Circuits. Busways which are used as branch circuits and which are so designed that loads can be connected at any point shall be limited to such lengths as will provide that in normal use the circuits will not be overloaded. In general, the length of such run in feet should not exceed three times the ampere rating of the branch circuit. 364-14. Marking. Busways shall be marked with the voltage and cur- rent rating for which they are designed, and with the manufacturer's name or trademark in such manner as to be visible after installation. ARTICLE 365—CABLEBUS 365-1. Definition. Cablebus is an approved assembly of insulated con- ductors mounted in spaced relationship in a ventilated metal protective supporting structure including fittings, conductor terminations. Cable- bus may be used at any voltage or current for which the spaced con- ductors are rated. Cablebus is ordinarily assembled at the point of installation, from com- ponents furnished or specified by the manufacturer. ARTICLE 365—CABLEBUS 70-151 365-2. Use. Cablebus shall be installed only for exposed work. Cable- bus installed outdoors or in corrosive, wet or damp locations shall be approved for the purpose.Cablebus shall not be installed in hoistways or in hazardous locations unless specifically approved for such use. Cable- bus may be used for branch circuits,feeders and services. Approved cablebus framework where adequately bonded may be used as the equipment grounding conductor for branch circuits and feeders. 365-3. Conductors. (a) Types of Conductor. The current carrying conductors in cable- bus shall have an insulation rating of 75°C or better of an approved type and suitable for the application in accordance with Articles 310 and 710. (b) Ampacity of Conductors. The ampacity of conductors in cable- bus shall be in accordance with Tables 310-13 and 310-15. (c) Size and Number of Conductors. The size and number of con- ductors shall be that for which the cablebus is designed, and in no case smaller than 1/0 AWG. (d) Conductor Supports. The insulated conductors shall be supported on blocks or other mounting means designed for the purpose. The individual conductors in a cablebus shall be supported at inter- vals not greater than 3 feet for horizontal runs and 11/z feet for vertical runs. Vertical and horizontal spacing between supported conductors shall be not less than one conductor diameter at the points of support. 365-5. Overcurrent Protection. When the allowable current rating of the cablebus conductors does not correspond to a standard rating of the overcurrent device, the next higher rated overcurrent device may be used. 365-6. Support. (a) Cablebus shall be securely supported at intervals not exceeding 12 feet. (b) Cablebus may extend transversely through partitions or walls, other than fire walls, provided the section within the wall is continuous, protected against physical damage and unventilated. (c) Except where fire stops are required, cablebus may extend ver- tically through dry floors and platforms, provided the cablebus is totally enclosed at the point where it passes through the floor or platform and for a distance of six feet above the floor or platform. (d) Except where fire stops are required, cablebus may extend ver- tically through floors and platforms in wet locations where (1) there are curbs or other suitable means to prevent waterflow through the floor or platform opening and (2) where the cablebus is totally en- closed at the point where it passes through the floor or platform and for a distance of six feet above the floor or platform. 365-7 Fittings. (a) Cablebus system shall provide approved fittings for: (1) Changes in horizontal or vertical direction of the run. (2) Dead ends. 70-152 NATIONAL ELECTRICAL CODE (3) Terminations in or on connected apparatus or equipment or the enclosures for such equipment. (4) Additional physical protection where required such as guards for severe mechanical exposure. 365-8. Conductor Terminations. Approved terminating means shall be used for connections to cablebus conductors. 365-9. Grounding. Sections of cablebus shall be electrically bonded either by inherent design of the mechanical joints or by applied bonding means.See Section 250-75. A cablebus installation shall be grounded in accordance with the re- quirements of Sections 250-32 and 250-33. 365-10. Marking. Each section of cablebus shall be marked with the manufacturer's name or trade designation and the maximum diameter, number, voltage rating and ampacity of the conductors to be installed. Markings shall be so located as to be visible after installation. ARTICLE 370—OUTLET, SWITCH AND JUNCTION BOXES, AND FITTINGS A. Scope and General 370-1. Scope. The provisions of this Article shall apply to the instal- lation of outlet, switch and junction boxes, and fittings as required by Section 300-15. Installations in hazardous locations shall conform to Articles 500 to 517 inclusive. 370-2. Round Boxes. Round boxes shall not be used where conduits or connectors requiring the use of locknuts or bushings are to be con- nected to the side of the box. 370-3. Nonmetallic Boxes. Nonmetallic boxes approved for the pur- pose may be used only with open wiring on insulators, concealed knob- and-tube work, nonmetallic sheathed cable, and with approved non- metallic conduit. 370-4. Metallic Boxes. Where used with knob-and-tube work or non- metallic sheathed cable, and mounted on metal or metal lath ceilings or walls, such boxes shall be insulated from their supports and from the metal or metal lath,or shall be grounded. B. Installation 370-5. Damp or Wet Locations. In damp or wet locations, boxes and fittings shall be so placed or equipped as to prevent moisture or water from entering and accumulating within the box or fitting. Boxes and fittings installed in wet locations shall be weatherproof. For boxes in floors,see Section 410-53. It is recommended that approved boxes of nonconductive material be used with nonmetallic sheathed cable or approved nonmetallic conduit when such cable or conduit is used in locations where there is likely to be occa- sional moisture present such as in dairy barns. ARTICLE 370—BOXES AND FITTINGS 70-153 370-6. Number of Conductors in a Box. Boxes shall be of sufficient size to provide free space for all conductors enclosed in the box. The provisions of this Section shall not apply to terminal housings supplied with motors.See Section 430-12. Section 370-6(a and b) does not apply to conductors used for rewiring existing raceways as referred to in Table 3,Chapter 9. (a) The maximum number of conductors, including grounding con- ductors, but not counting fixture wires,permitted in outlet and junction boxes shall be as in Tables 370-6(a-1 and-2) with the exceptions noted. Tables 370-6(a-1 and -2) apply where no fittings or devices, such as fixture studs, cable clamps, hickeys, switches or receptacles are con- tained in the box. Where one or more fixture studs, cable clamps, or hickeys are contained in the box, the number of conductors shall be one less than shown in the Tables, with a further deduction of one con- ductor for one or several flush devices mounted on the same strap. A conductor running through the box is counted as one conductor and each conductor originating outside the box and terminating inside the box is counted as one conductor. Conductors of which no part leaves the box are not to be counted in the above computation. If single flush boxes are ganged, and each section is occupied by a flush device or combination of flush devices on the same strap, the limitations will apply to each section individually. Table 370-6(a-1). Deep Boxes Box Dimensions, Cubic Maximum Number of Conductors Inches Inch Trade Size Cap. No.14 No.12 No.10 No.8 31/4 x 11/z Octagonal 10.9 5 4 4 3 31/ix112 " 11.9 5 5 4 3 4x11/ 64 17.1 8 7 6 5 4x21/2 66 23.6 11 10 9 7 4 x 11/2 Square 22.6 11 10 9 7 4x21/2 " 31.9 15 14 12 10 4 11/16 x 116 Square 32.2 16 14 12 10 4 11/16 x 21/2 " 46.4 23 20 18 15 3x2x11/z Device 7.9 3 3 3 2 3x2x2 10.7 5 4 4 3 3x2x21/4 66 11.3 5 5 4 3 3x2x21h 64 13 6 5 5 4 3x2x23 44 14.6 7 6 5 4 3x2x31 18.3 9 8 7 6 4x21/sx11/i 11.1 5 4 4 3 4 x 21/2 x 1%s " 13.9 6 6 5 4 4x212 x21/2 " 15.6 7 6 6 5 See Section 370-18 where boxes are used as pull and junction boxes. 70-154 NATIONAL ELECTRICAL CODE Table 370-6(a-2). Shallow Boxes Maximum Number of Conductors Box Dimensions, Inches Trade Size No.14 No.12 No.10 31/4 4 4 3 4 6 6 4 11/4 x 4 Square 9 7 6 4 11/16 8 6 6 Any box less than 11/2 inch deep is considered to be a shallow box. (b) For combinations or conductor sizes not shown in the above Tables,Table 370-6(b) shall apply. Table 370-6(b). Volume Required Per Conductor Size of Free Space Within Box Conductor for Each Conductor No. 14 2. cubic inches No. 12 2.25 cubic inches No. 10 2.5 cubic inches No. 8 3. cubic inches No. 6 5. cubic inches (c) Boxes, other than those described in Tables 370-6(a) (1) and 370-6(a) (2),shall be durably and legibly marked by the manufacturer with their cubic inch content. All boxes shall be durably and legibly marked with the manufacturer's name or trademark. 370-7. Conductors Entering Boxes or Fittings. Conductors entering boxes or fittings shall be protected from abrasion, and shall conform to the following: (a) Openings to Be Closed. Openings through which conductors enter shall be adequately closed. (b) Metal Boxes and Fittings. Where metal outlet boxes or fittings are installed with open wiring or concealed knob-and-tube work, con- ductors shall enter through insulating bushings or, in dry places, through flexible tubing extending from the last insulating support and firmly secured to the box or fitting. Where raceway or cable is installed with metal outlet boxes or fittings,the raceway or cable shall be secured to such boxes and fittings. (c) Nonmetallic Boxes. Where nonmetallic boxes are used with open wiring or concealed knob-and-tube work, the conductors shall en- ter through individual holes. Where flexible tubing is used to encase the conductor, the tubing shall extend from the last insulating support and may be run into the box or terminate at the wall of the box. If non- metallic sheathed cable is used, the cable assembly shall enter the box through a knockout opening. Clamping of individual conductors or ca- bles to the box is not required where supported within 8 inches of the ARTICLE 370—BOXES AND FITTINGS 70-155 box. Where nonmetallic conduit is installed with nonmetallic boxes or fittings, the conduit shall be secured to such boxes and fittings in an ap- proved manner. 370-8. Unused Openings. Unused openings in boxes and fittings shall be effectively closed to afford protection substantially equivalent to that of the wall of the box or fitting. Metal plugs or plates used with non- metallic boxes or fittings shall be recessed at least 1/4 inch from the outer surface. 370-9. Boxes Enclosing Flush Devices. Boxes used to enclose flush de- vices shall be of such design that the devices will be completely en- closed on back and sides, and that substantial support for the devices will be provided. Screws for supporting the box shall not be used in at- tachment of the device contained therein. 370-10. In Wall or Ceiling. In walls or ceilings of concrete, tile or other noncombustible material, boxes and fittings shall be so installed that the front edge of the box or fitting will not set back of the finished surface more than 1/4 inch. In walls and ceilings constructed of wood or other combustible material, outlet boxes and fittings shall be flush with the finished surface or project therefrom. 370-11. Repairing Plaster. Except on walls or ceilings of concrete, tile or other noncombustible material, a plaster surface which is broken or incomplete shall be repaired so that there will be no gaps or open spaces at the edge of the box or fitting. 370-12. Exposed Extensions. In making an exposed extension from an existing outlet of concealed wiring, a box, extension ring or blank cover shall be mounted over the original box and electrically and mechanically secured to it. The extension shall then be connected to this box in the manner prescribed for the method of wiring employed in making the extension. 370-13. Supports. Boxes shall be securely and rigidly fastened to the surface upon which they are mounted,or securely and rigidly embedded in concrete or masonry. Except as otherwise provided in this Section, boxes shall be supported from a structural member of the building either directly or by using a substantial and approved metallic or wooden brace. If of wood the brace shall not be less than nominal 1 inch thickness. If of metal it shall be corrosion resistant and shall be not less than 0.0239 inch thick (No.24 MSG). Where mounted in new walls in which no structural members are provided or in existing walls in previously occupied buildings, boxes less than 100 cubic inches in size, specifically approved for the purpose, shall be affixed with approved anchors or clamps so as to provide a rigid and secure installation. Threaded boxes or fittings less than 100 cubic inches in size, which do not contain devices or support fixtures may be considered adequately supported if two or more conduits are threaded into the box wrench- tight and are supported within three feet of the box on two or more sides as is required by this Section. 370-14. Depth of Outlet Boxes for Concealed Work. Outlet boxes for concealed work shall have an internal depth of at least 11 inches, ex- 70-156 NATIONAL ELECTRICAL CODE cept that where the installation of such a box will result in injury to the building structure or is impracticable, a box not less than lh inch in- ternal depth may be installed. 370-15. Covers and Canopies. In completed installations each outlet box shall be provided with a cover unless a fixture canopy is used. (a) Nonmetallic covers and plates or metallic covers and plates may be used with nonmetallic outlet boxes. When metallic covers or plates are used, they shall comply with the grounding requirements of Section 250-42. See Section 410-95. (b) Where a fixture canopy or pan is used, any combustible wall or ceiling finish exposed between the edge of the canopy or pan and the outlet box shall be covered with noncombustible material. (c) Covers of outlet boxes having holes through which flexible cord pendants pass, shall be provided with bushings designed for the purpose or shall have smooth, well-rounded surfaces on which the cords may bear.So-called hard-rubber or composition bushings shall not be used. 370-16. Fastened to Gas Pipes. Outlet boxes used where gas outlets are present shall be so fastened to the gas pipes as to be mechanically secure. 370-17. Boxes at Lighting Fixture Outlets. Boxes used at outlets for lighting fixtures shall be designed for the purpose. At every outlet used exclusively for lighting, the box shall be so designed or installed that a lighting fixture may be attached. 370-18. Pull and Junction Boxes. Pull and junction boxes shall con- form to the following: (a) Minimum Size. For raceways of 1 inch trade size and larger, containing conductors of No. 6 or larger, and for cables* containing conductors of No. 6 or larger, the minimum dimensions of a pull or junction box installed in a raceway or cable run shall conform to the following: (1) Straight Pulls. In straight pulls the length of the box shall be not less than 8 times the trade diameter of the largest raceway. (2) Angle or U Pulls. Where angle or U pulls are made, the dis- tance between each raceway entry inside the box and the opposite wall of the box shall not be less than 6 times the trade diameter of the larg- est raceway. This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries on the same wall of the box. The distance between raceway entries en- closing the same conductor shall not be less than 6 times the trade di- ameter of the larger raceway. (3) Boxes of lesser dimensions than those required in sub-sections (1) and (2) of this Section may be used for installations of combina- *When transposing cable size into raceway size in (1) and (2) above, the minimum trade size raceway required for the number and size of conductors in the cable shall be used. ARTICLE 370—BOXES AND FITTINGS 70-157 tions of conductors which are less than the maximum conduit fill (of conduits being used) permitted by Table 1, Chapter 9, provided the box has been approved for and is permanently marked with the maximum number of conductors and the maximum AWG size permitted. Exception: Terminal housings supplied with motors which shall com- ply with the provisions of Section 430-12. (b) Conductors in Pull or Junction Boxes. In pull boxes or junction boxes having any dimension over 6 feet, all conductors shall be cabled or racked up in an approved manner. See Section 373-6(b) for insulation of conductors at bushings. (c) Covers. All pull boxes, junction boxes and fittings shall be pro- vided with covers approved for the purpose. Where metallic covers are used, they shall comply with the grounding requirements of Section 250-42. 370-19. Junction, Pull and Outlet Boxes Be Accessible. Junction, pull and outlet boxes shall be so installed that the wiring contained in them may be rendered accessible without removing any part of the building, sidewalks or paving. C. Construction Specifications 370-20. Metallic Outlet, Switch and Junction Boxes and Fittings. Out- let, switch and junction boxes and fittings, when of metal, shall conform to the following: (a) Corrosion-Resistant. Metallic boxes and fittings, unless of cor- rosion-resistant metal, shall be well galvanized, enameled, or otherwise properly coated,inside and out,to prevent corrosion. See Section 300-5 for limitation in the use of boxes and fittings protected from corrosion solely by enamel. It is recommended that the protective coating be of conductive material, such as cadmium,tin or zinc,in order to secure better electrical contact. (b) Thickness of Metal. Sheet metal boxes and fittings not over 100 cubic inches in size shall be made from metal not less than 0.067 inch thick (No. 14 MSG). Cast metal boxes shall have a wall thickness not less than 1/9 inch, except that boxes of malleable iron shall have a wall thickness of not less than 3/32 inch. (c) Boxes Over 100 Cubic Inches. Boxes of over 100 cubic inches in size shall be composed of metal and shall conform to the requirements for cabinets and cutout boxes, except that the covers may consist of single flat sheets secured to the box proper by screws, or bolts instead of hinges. Boxes having covers of this form are for use only for enclos- ing joints in conductors or to facilitate the drawing in of wires and ca- bles. They are not intended to enclose switches, cutouts or other con- trol devices. 370-21. Covers. Metal covers shall be of a thickness not less than that specified for the walls of the box or fitting of the same material and with which they are designed to be used, or shall be lined with firmly attached insulating material not less than 1/32 inch in thickness. Covers of porcelain or other approved insulating material may be used when 70-158 NATIONAL ELECTRICAL CODE of such form and thickness as to afford the requisite protection and strength. 370-22. Bushings. Covers of outlet boxes and outlet fittings having holes through which flexible cord pendants may pass, shall be provided with approved bushings or shall have smooth, well-rounded surfaces, upon which the cord may bear. Where conductors other than flexible cord may pass through a metal cover, there shall be provided a sep- arate hole for each wire, said hole being equipped with a bushing of suitable insulating material. 370-23. Nonmetallic Boxes. Provisions for supports, or other mount- ing means, for nonmetallic boxes, shall be outside of the box, or the box shall be so constructed as to prevent contact between the conduc- tors in the box and the supporting screws. ARTICLE 373—CABINETS AND CUTOUT BOXES 373-1. Scope. The provisions of this Article shall apply to the installa- tion of cabinets and cutout boxes. Installations in hazardous locations shall conform to the provisions of Articles 500 to 517 inclusive. A. Installation 373-2. Damp or Wet Locations. In damp or wet locations,cabinets and cutout boxes of the surface type shall be so placed or equipped as to prevent moisture or water from entering and accumulating within the cabinet or cutout box, and shall be mounted so there is at least 1/a inch air space between the enclosure and the wall or other supporting sur- face. Cabinets or cutout boxes installed in wet locations shall be weatherproof. It is recommended that boxes of nonconductive material be used with nonmetallic sheathed cable when such cable is used in locations where there is likely to be moisture present. 373-3. Position in Wall. In walls of concrete, tile, or other noncom- bustible material, cabinets shall be so installed that the front edge of the cabinet will not set back of the finished surface more than '/a inch. In walls constructed of wood or other combustible material, cabinets shall be flush with the finished surface or project therefrom. 373-4. Unused Openings. Unused openings in cabinet or cutout boxes shall be effectively closed to afford protection substantially equiv- alent to that of the wall of the cabinet or cutout box. Where metal plugs or plates are used with nonmetallic cabinets or cutout boxes, they shall be recessed at least 1/a inch from the outer surface. 373-5. Conductors Entering Cabinets or Cutout Boxes. Conductors en- tering cabinets or cutout boxes shall be protected from abrasion and shall conform to the following: (a) Openings to Be Closed. Openings through which conductors en- ter shall be adequately closed. ARTICLE 373—CABINETS AND CUTOUT BOXES 70-159 (b) Metal Cabinets and Cutout Boxes. Where metal cabinets or cut- out boxes are installed with open wiring or concealed knob-and-tube work, conductors shall enter through insulating bushings or, in dry places, through flexible tubing extending from the last insulating sup- port and firmly secured to the cabinet or cutout box. 373-6. Deflection of Conductors. Conductors entering or leaving cabi- nets or cutout boxes and the like shall conform to the following: (a) Width of Gutters. Conductors shall not be deflected within a cabinet unless a gutter having a width in accordance with Table 373- 6(a) is provided. Table 373-6(a)—Minimum Bending Space in Inches AWG or Circular-Mil Wires per Terminal Size of Wire 1 2 3 4 5 Not 14-8 Specified — — — — 6 1-1/z — — — — 4-3 2 — — — — 2 21/a — — — — 1 3 — — 0-00 31 — — — — 000—0000 4 6 8 — — 250 MCM 41 6 8 10 — 300-350 MCM 5 8 10 12 — 400-500 MCM 6 8 10 12 14 600-700 MCM 8 10 12 14 16 750-900 MCM 8 — — — — 1,000-1,250 MCM 10 — — — — 1,500-2,000 MCM 12 — — — — NOTE: The distance shall be measured in a straight line from the end of the lug or wire connector (in the direction that the wire leaves the terminal) to the wall or barrier. (b) Insulation at Bushings. Where ungrounded conductors of No. 4 or larger enter a raceway in a cabinet, pull box, junction box, or auxiliary gutter,the conductors shall be protected by a substantial bush- ing providing a smoothly rounded insulating surface, unless the con- ductors are separated from the raceway fitting by substantial insulat- ing material securely fastened in place. Where conduit bushings are constructed wholly of insulating material, a locknut shall be installed both inside and outside the enclosure to which the conduit is attached. 373-7. Space in Enclosures. Cabinets and cutout boxes shall conform to the following: (a) To Accommodate Conductors. Cabinets and cutout boxes shall be selected which have sufficient space to accommodate all conductors installed in them without crowding. 70-160 NATIONAL ELECTRICAL CODE ti 373-8. Enclosures for Switches or Overcurrent Devices. Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless designs suitable for the purpose are employed to provide adequate space for this purpose. 373-9. Side or Back Wiring Spaces or Gutters. Cabinets and cutout boxes shall be provided with back wiring spaces, gutters, or wiring corn- partments as required by Section 373-11(c and d). B. Construction Specifications 373-10. Material. Cabinets and cutout boxes shall conform to the fol- lowing: (a) Metal Cabinets and Boxes. Metal cabinets and cutout boxes shall be well galvanized,plated with cadmium or other approved metal- lic finish, enameled, or otherwise properly coated, inside and out, to prevent corrosion. It is recommended that the protective coating be of conductive material, such as cadmium,tin or zinc,in order to secure better electrical contact. (b) Strength. The design and construction of cabinets and cutout boxes shall be such as to secure ample strength and rigidity. If con- structed of sheet steel, the metal shall be of not less than No. 16 USS gage (.0598 inch) in thickness. (c) Composition Cabinets. Composition cabinets shall be submitted for approval prior to installation. 373-11. Spacing. The spacing within cabinets and cutout boxes shall conform to the following: (a) General. The spacing within cabinets and cutout boxes shall be sufficient to provide ample room for the distribution of wires and cables placed in them, and for a separation between metal parts of devices and apparatus mounted within them as follows: (1) Base. There shall be an air space of at least 1/16 inch, except at points of support, between the base of the device and the wall of any metal cabinet or cutout box in which the device is mounted. (2) Doors. There shall be an air space of at least 1 inch between any live metal part (including live metal parts of enclosed fuses) and the door, unless the door is lined with an approved insulating material or is of a thickness of metal not less than No. 12 USS gage (.1046 inch),when the air space shall be not less than 1 inch. (3) Doors and Walls — Link Fuses. There shall be a space of at least 2 inches between open link fuses and metal-lined walls or metal, metal-lined or glass-paneled doors. (4) Live Parts. Except as noted above, there shall be an air space of at least 1 inch between the walls, back, gutter partition, if of metal, or door of any cabinet or cutout box and the nearest exposed current- carrying part of devices mounted within the cabinet where the potentials do not exceed 250 volts. This spacing shall be increased to at least one inch where the potentials exceed 250 volts. ARTICLE 374—AUXILIARY GUTTERS 70-161 (b) Switch Clearance. Cabinets and cutout boxes shall be deep enough to allow the closing of the doors when 30-ampere branch-cir- cuit panelboard switches are in any position, or when combination cutout switches are in any position, or when other single-throw switches are opened as far as their construction will permit. (c) Wiring Space. Cabinets and cutout boxes which contain de- vices or apparatus connected within the cabinet or box to more than 8 conductors, including those of branch circuits, meter loops, sub-feeder circuits,power circuits and similar circuits, but not including the supply circuit or a continuation thereof, shall have back wiring spaces or one or more side wiring spaces,side gutters or wiring compartments. (d) Wiring Space — Enclosure. Side wiring spaces, side gutters or side wiring compartments of cabinets and cutout boxes shall be ren- dered tight enclosures by means of covers, barriers or partitions ex- tending from the bases of the devices, contained in the cabinet, to the door, frame, or sides of the cabinet; provided, however, that where the enclosure contains only those conductors which are led from the cabi- net at points directly opposite their terminal connections to devices within the cabinet, such covers, barriers or partitions may be omitted. Partially enclosed back wiring spaces shall be provided with covers to complete enclosure. Wiring spaces that are required by Section 373- 11(c) and which are exposed when doors are open, shall be provided with covers to complete the enclosure. ARTICLE 374—AUXILIARY GUTTERS 374-1. Purpose. Auxiliary gutters, used to supplement wiring spaces at meter centers, distribution centers, switchboards and similar points of wiring systems, may enclose conductors or bus-bars, but shall not be used to enclose switches,overcurrent devices,appliances or other similar equipment. 374-2. Extension Beyond Equipment. An auxiliary gutter shall not extend a greater distance than 30 feet beyond the equipment which it supplements except in elevator work. Any extension beyond this dis- tance shall comply with the provisions for wireways in Article 362 or with the provisions for busways in Article 364. 374-3. Supports. Gutters shall be supported throughout their entire length at intervals not exceeding 5 feet. 374-4. Covers. Covers shall be securely fastened to the gutter. 374-5. Number of Conductors. Auxiliary gutters shall not contain more than 30 conductors at any cross section unless the conductors are for signal circuits or are controller conductors between a motor and its starter and used only for starting duty. The sum of the cross-sectional areas of all contained conductors at any cross section of an auxiliary gutter shall not exceed 20 per cent of the interior cross-sectional area of the gutter. For elevators see Section 620-35. 70-162 NATIONAL ELECTRICAL CODE 374-6. Ampacity of Conductors. The ampacities of insulated copper and aluminum conductors are given in Tables 310-12 and 310-14 re- spectively. The correction factors specified in Note 8 of these tables shall not apply to conductors in auxiliary gutters. The current carried continuously in bare copper bars in auxiliary gutters shall not exceed 1000 amperes per square inch of cross section of the conductor. For aluminum bars the current carried continuously shall not exceed 700 amperes per square inch of cross section of the conductor. 374-7. Clearance of Bare Live Parts. Bare conductors shall be securely and rigidly supported so that the minimum clearance between bare cur- rent-carrying metal parts of opposite polarities mounted on the same surface shall be not less than 2 inches,nor less than 1 inch for parts that are held free in the air.A clearance not less than 1 inch shall be secured between bare current-carrying metal parts and any metal surface. Ade- quate provisions shall be made for the expansion and contraction of bus-bars. 374-8. Splices and Taps. Splices and taps shall conform to the fol- lowing: (a) Splices or taps, made and insulated by approved methods, may be located within gutters when they are accessible by means of re- movable covers or doors. The conductors, including splices and taps, shall not fill the gutter to more than 75 per cent of its area. (b) Taps from bare conductors shall leave the gutter opposite their terminal connections and conductors shall not be brought in contact with uninsulated current-carrying parts of opposite polarity. (c) All taps shall be suitably identified at the gutter as to the circuit or equipment which they supply. (d) Tap connections from conductors in auxiliary gutters shall be provided with overcurrent protection in conformity with the provisions of Section 240-15. 374-9. Construction and Installation. Auxiliary gutters shall be con- structed in accordance with the following: (a) Gutters shall be so constructed and installed that adequate elec- trical and mechanical continuity of the complete system will be se- cured. (b) Gutters shall be of substantial construction and shall provide a complete enclosure for the contained conductors. All surfaces, both in- terior and exterior, shall be suitably protected from corrosion. Corner joints shall be made tight and where the assembly is held together by rivets or bolts,these shall be spaced not more than 12 inches apart. (c) Suitable bushings, shields or fittings having smooth rounded edges shall be provided where conductors pass between gutters, through par- titions, around bends, between gutters and cabinets or junction boxes and at other locations where necessary to prevent abrasion of the in- sulation of the conductors. (d) Gutters shall be constructed of sheet metal of thicknesses not less than in the following table: ARTICLE 380—SWITCHES 70-163 Table 374-9(d) Maximum Width of the Widest Surface of Gutters Thickness(Manufacturers Standard Gage) Up to and including 6 inches No. 16;0.0598 inch Over 6 in.and not over 18 in. No. 14;0.0747 inch Over 18 in.and not over 30 in. No. 12;0.1046 inch Over 30 inches No. 10;0.1345 inch (e) Where insulated conductors are deflected within the auxiliary gutter, either at the ends or where conduits, fittings or other raceways enter or leave the gutter, or where the direction of the gutter is deflected greater than 30 degrees, dimensions corresponding to Section 373-6 shall apply. (f) Auxiliary gutters intended for outdoor use shall be of approved raintight construction. ARTICLE 380—SWITCHES A. Installation 380-1. Grounded Conductors. No switch or circuit breaker shall dis- connect the grounded conductor of a circuit unless the switch or cir- cuit breaker simultaneously disconnects the ungrounded conductor or conductors, or unless the switch or circuit breaker is so arranged that the grounded conductor cannot be disconnected until the ungrounded conductor or conductors have first been disconnected. 380-2. Three-Way and Four-Way Switches. Three-way and four-way switches shall be so wired that all switching is done only in the un- grounded circuit conductor. Wiring between switches and outlets shall, where in metal enclosures, be run with both polarities in the same en- closure. 380-3. Enclosures. Switches and circuit breakers shall be of the ex- ternally operable type enclosed in metal boxes or cabinets, except pen- dant and surface type snap switches and knife switches mounted on an open face switchboard or panelboard. 380-4. Wet Locations. A switch or circuit breaker in a wet location or outside of a building shall be enclosed in a weatherproof enclosure or cabinet installed to conform to Section 373-2. 380-5. Time Switches, Flashers, and Similar Devices. Time switches, flashers, and similar devices need not be of the externally operable type.They shall be enclosed in metal boxes or cabinets except: Exception No. 1. Where mounted on switchboards or control panels. Exception No.2. Where enclosed in approved individual housings. 380-6. Position of Knife Switches. Single-throw knife switches shall be so placed that gravity will not tend to close them. Double-throw knife 70-164 NATIONAL ELECTRICAL CODE switches may be mounted so that the throw will be either vertical or horizontal as preferred, but where the throw be vertical a locking de- vice shall be provided which will insure the blades remaining in the open position when so set. 380-7. Connection of Knife Switches. Knife switches, unless of the double-throw type, shall be so connected that the blades are dead when the switch is in the open position. 380-8. Accessibility and Grouping. Switches and circuit breakers, so far as practicable,shall be readily accessible and shall be grouped. Snap switches shall not be grouped or ganged in outlet boxes unless they can be so arranged that the voltage between exposed live metal parts of adjacent switches does not exceed 300 volts. 380-9. Covers of Flush Snap Switches. Flush snap switches, that are mounted in ungrounded metal boxes and located within reach of con- ducting floors or other conducting surfaces, shall be provided with covers of nonconducting, noncombustible material. Metallic faceplates shall be of ferrous metal not less than 0.030 inch in thickness or of nonferrous metal not less than 0.040 inch in thickness. Faceplates of insulating material shall be noncombustible and not less than 0.10 inch in thickness but may be less than 0.10 inch in thickness if formed or reinforced to provide adequate mechanical strength. 380-10. Mounting of Surface-Type Snap Switches. Snap switches used with open wiring on insulators shall be mounted on sub-bases of in- sulating material which will separate the conductors at least lh inch from the surface wired over. 380-11. Circuit Breakers as Switches. A circuit breaker operable di- rectly by applying the hand to a lever or handle may serve as a switch provided it has the number of poles required for such switch. 380-12. Grounding of Enclosures. Enclosures for switches or circuit breakers on circuits of over 150 volts to ground shall be grounded in the manner specified in Article 250, except where accessible to quali- fied operators only. 380-13. Knife Switches. (a) Knife switches rated for more than 1200 amperes at 250 volts or less, and for more than 600 amperes at 251 to 600 volts, shall be used only as isolating switches and shall not be opened under load. (b) To interrupt currents greater than 1200 amperes at 250 volts or less, or 600 amperes at 251 to 600 volts, a circuit breaker or a switch of special design approved for such purpose shall be used. (c) Knife switches of lower rating may be used as general-use switches and may be opened under load. (d) Motor-circuit switches (see Definition) may be of the knife- switch type. 380-14. Rating of Snap Switches. Snap switches installed for the fol- lowing types of loads shall be rated as follows: (a) Noninductive Loads. For noninductive loads other than tungs- ten-filament lamps, switches shall have an ampere rating not less than the ampere rating of the load. ARTICLE 384—SWITCHBOARDS AND PANELBOARDS 70-165 (b) Tungsten Filament Loads. For tungsten-filament lamp load and for combined tungsten-filament and noninductive loads, switches shall be "T" rated or, where on alternating-current circuits, may be a gen- eral use alternating-current snap switch. Exception. A switch that is not "T" rated may be installed to con- trol such loads provided all three of the following qualifications are satisfied: (1) Where switches are used in branch circuit wiring systems in private homes; in rooms in multiple-occupancy dwellings used only as living quarters by tenants;in private hospital or hotel rooms;or in simi- lar locations but not in public rooms or places of assembly;and (2) Only where such a switch controls permanently connected fix- tures or lighting outlets in one room only, or in one continuous hall- way where the lighting fixtures may be located at different levels, or on porches or in attics or basements not used for assembly purposes; and (3) The switch is rated at not less than 10A, 125V;5A, 250V;or for the 4-way types,5A,125 V;2A,250V. (c) Inductive Loads. Switches controlling inductive loads shall have an ampere rating twice the ampere rating of the load unless they are of a type approved as part of an assembly or for the purpose employed. On alternating-current circuits, general use alternating-current snap switches may be used to control inductive loads other than motors not exceeding the ampere rating of the switch. For switches on signs and outline lighting,see Section 600-2. For switches controlling motors,see Sections 430-83,430-109 and 430-110. B. Construction Specifications 380-15. Marking. Switches shall be marked with the current and voltage and, if horsepower rated, the maximum rating for which they are designed. 380-16. 600-Volt Knife Switches. Auxiliary contacts of a renewable or quick-break type or the equivalent, shall be provided on all 600-volt knife switches designed for use in breaking currents over 200 amperes. It is recommended that such auxiliary contacts be provided on all direct- current switches rated at over 250 volts. 380-17. Fused Switches. A fused switch shall not have fuses in parallel. ARTICLE 384—SWITCHBOARDS AND PANELBOARDS 384-1. Scope. The requirements of this Article shall apply to all switchboards, panelboards, and distribution boards installed for the control of light and power circuits. 70-166 NATIONAL ELECTRICAL CODE Exception No. 1. Switchboards in utility company operated central stations or substations, which directly control energy derived from generators or transforming devices. Exception No. 2. Switchboards or portions thereof used exclusively to control signal circuits operated by batteries. The requirements of this Article shall apply to battery-charging pan- els where current is taken from light or power circuits. 384-2. Application of Other Articles. Switches, circuit breakers and overcurrent devices used on switchboards, panelboards and distribution boards, the boards and their enclosures, shall conform to the require- ments of Articles 240, 250, 370, 380 and other Articles which apply. Switchboards and panelboards in hazardous locations shall conform to the requirements of Articles 500 to 517 inclusive. 384-3. Support and Arrangement of Bus-bars and Conductors. (a) Conductors and bus-bars on a switchboard, panelboard or con- trol board shall be so located as to be free from physical damage and shall be held firmly in place. (b) The arrangement of bus-bars and conductors shall be such as to avoid overheating due to inductive effects. (c) Each switchboard, switchboard section or panelboard, if used as service equipment, shall be provided with an equipment grounding means placed within the service disconnect section for connecting the grounded circuit conductor on its supply side to the switchboard or panelboard frame.The equipment grounding means shall not be smaller than called for in Table 250-95 nor smaller than No. 8 AWG copper conductor or approved equivalent. A. Switchboards 384-4. Location of Switchboards. Switchboards which have any ex- posed live parts shall be located in permanently dry locations and then only where under competent supervision and accessible only to quali- fied persons. 384-5. Wet Locations. Where a switchboard is in a wet location or outside of a building, it shall be enclosed in a weatherproof enclosure or cabinet installed to conform to Section 373-2. 384-6. Location Relative to Easily Ignitible Material. Switchboards shall be so placed as to reduce to a minimum the probability of com- municating fire to adjacent easily ignitible material. 384-7. Clearance from Ceiling. Switchboards shall not be built up to a nonfireproof ceiling, a space of 3 feet being left between the ceiling and the board, unless an adequate fireproof shield is provided between the board and the ceiling. 384-8. Clearance Back of Switchboard. Clearances around switchboards shall conform to the provisions for Working Space about Electrical Equipment as specified in Section 110-16 of this Code. 384-9. Conductor Covering. Insulated conductors where closely grouped, as on the rear of switchboards, shall each have a flame-re- ARTICLE 384—SWITCHBOARDS AND PANELBOARDS 70-167 tardant outer covering. The conductor covering shall be stripped back a sufficient distance from the terminals so as to not make contact with them. Insulated conductors used for instrument and control wiring on the back of switchboards shall be flame-retardant, either inherently or by means of an outer covering, such as one of the following types: RH,RHH,RHW,V, ALS,AVA,AVB,SIS,T,TA, TBS, TW,THHN, THWN, THW, MI, XHHW, or other types specifically approved for the purpose. 384-11. Grounding Switchboard Frames. Switchboard frames and structures supporting switching equipment shall be grounded, except that frames of direct-current single-polarity switchboards need not be grounded if effectively insulated. 384-12. Grounding of Instruments, Relays, Meters and Instrument Trans- formers on Switchboards. Instruments, relays, meters and instrument transformers located on switchboards shall be grounded as specified in Sections 250-121 to 250-125. B. Panelboards 384-13. General. All panelboards shall have a rating not less than the minimum feeder capacity required for the load as computed from Ar- ticle 220. Panelboards shall be durably marked by the manufacturer with the voltage and the current rating and the number of phases for which they are designed and with the manufacturer's name or trade- mark in such a manner as to be visible after installation, without dis- turbing the interior parts or wiring. 384-14. Lighting and Appliance Branch Circuit Panelboard. For the purposes of this Article, a lighting and appliance branch circuit panel- board is one having more than 10 per cent of its overcurrent devices rated 30 amperes or less,for which neutral connections are provided. 384-15. Number of Overcurrent Devices on One Panelboard. Not more than 42 overcurrent devices (other than those provided for in the mains) of a lighting and appliance branch circuit panelboard shall be installed in any one cabinet or cutout box. A lighting and appliance branch circuit panelboard shall be pro- vided with physical means to prevent the installation of more overcur- rent devices than that number for which the panelboard was designed, rated and approved. For the purposes of this Article a two-pole circuit breaker shall be considered two overcurrent devices; a three-pole breaker shall be con- sidered three overcurrent devices. • 384-16. Overcurrent Protection. (a) Each lighting and appliance branch circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard. Exception No. 1. Individual protection for a lighting and appliance panelboard is not required when the panelboard feeder has overcur- rent protection not greater than that of the panelboard. 70-168 NATIONAL ELECTRICAL CODE Exception No. 2. Individual protection for lighting and appliance branch circuit panelboards is not required where such panelboards are used as service equipment in supplying an individual residential oc- cupancy and where any bus supplying 15 or 20 ampere circuits is pro- tected on the supply side by an overcurrent device. (b) Panelboards equipped with snap switches rated at 30 amperes or less,shall have overcurrent protection not in excess of 200 amperes. (c) The total load on any overcurrent device located in a panelboard shall not exceed 80% of its rating where in normal operation the load will continue for 3 hours or more. Exception. Except where the assembly including the overcurrent de- vice is approved for continuous duty at 100 per cent of its rating. 384-17. Panelboards in Damp or Wet Locations. Panelboards in damp or wet locations shall be installed in conformity to Section 373-2. 384-18. Enclosure. Panelboards shall be mounted in cabinets or cut- out boxes. 384-19. Relative Arrangement of Switches and Fuses. Panelboards having switches on the load side of any type of fuses shall not be in- stalled except for use as service equipment as provided in Section 230-94. C. Construction Specifications 384-20. Panels. The panels of switchboards shall be made of mois- ture-resistant,noncombustible material. 384-21. Bus-bars. Bus-bars may be of bare metal provided they are rigidly mounted. 384-22. Protection of Instrument Circuits. Instruments, pilot lights, potential transformers, and other switchboard devices with potential coils, except where the operation of the overcurrent device might in- troduce a hazard in the operation of devices, shall be supplied by a cir- cuit that is protected by standard overcurrent devices of a rating not greater than 15 amperes, except that for ratings of 2 amperes or less special types of enclosed fuses may be used. 384-23. Component Parts. Switches, fuses, and fuseholders used on panelboards shall conform to the requirements of Articles 240 and 380 so far as they apply. 384-24. Knife Switches. Knife switches shall be so arranged that the blades, when exposed during operation, will be dead when the switches are open. 384-25. Color-Coding. On switchboards or panelboards that are pro- vided with color markings to indicate the main bus-bars to which branch circuit bus-bars are connected, the colors shall conform to the color coding of Section 210-5. 384-26. Spacings. Except at switches and circuit breakers, the dis- tance between bare metal parts, bus-bars, etc., shall be not less than specified in the following Table: ARTICLE 390—PREFABRICATED BUILDINGS 70-169 Table 384-26. Spacings Between Bare Metal Parts Opposite Opposite Polarity Polarity When When Mounted on Held the Same Free *Live Parts Surface in Air to Ground Not over 125 volts 3/a inch lh inch th inch Not over 250 volts 11/4 inch 3Aa inch lh inch Not over 600 volts 2 inches 1 inch 1 inch *For spacing between live parts and doors of cabinets, see Section 373- 11(a) (1), (2), (3) and (4). It should be noted that the above distances are the minimum allowable, and it is recommended that greater distances be provided wherever the con- ditions will permit. At switches, enclosed fuses, etc., parts of the same polarity may be placed as close together as convenience in handling will allow, unless close proximity causes excessive heating. 384-27. Grounding of Panelboards. Panelboard cabinets shall be grounded in the manner specified in Section 250-113. Approved means for equipment grounding conductors shall be provided and secured to the cabinet interior for the attachment of all the feeder and branch circuit equipment grounding conductors, when the panelboard is used with nonmetallic raceway or cable wiring. The equipment grounding terminal bar shall be bonded to the panelboard cabinet but shall not be connected to the insulated neutral bar except at service equipment as permitted in Section 250-52. ARTICLE 390—PREFABRICATED BUILDINGS 390-1. Scope. The intent and purpose of the following sections is to define approved methods for the wiring of prefabricated building sec- tions, panels, or units designed for later erection or assembly as integral parts of buildings whether wired in the process of manufacture or at the site of erection or assembly. 390-2. Wiring Methods. Only wiring methods recognized in this Code shall be used. 390-3. Code Provisions to Apply. The provisions of this Code shall apply for the type of wiring method used and the type of construction employed. 70-170 Chapter 4. Equipment for General Use ARTICLE 400—FLEXIBLE CORDS AND CABLES A. General and Types 400-1. General. Flexible cords and cables and their associated fittings shall be suitable for the conditions of use and location. 400-2. Types. Cords of the several types shall conform to the descrip- tions of Table 400-11. Types of flexible cords other than those listed in Table 400-11 and other uses for types listed in the Table, shall be the subject of special investigations and shall not be used before being ap- proved. B. Use and Installation 400-3. Use. (a) Flexible cord may be used only for (1) pendants; (2) wiring of fixtures; (3) connection of portable lamps or appliances; (4) elevator cables; (5) wiring of cranes and hoists; (6) connection of stationary equipment to facilitate their frequent interchange; or (7) prevention of the transmission of noise or vibration;or (8) facilitating the removal or disconnection of fixed or stationary appliances for maintenance or re- pair. (b) Where used as permitted in Sub-sections (a) (3), (a) (6), and (a) (8) of this Section,each flexible cord shall be equipped with an at- tachment plug and shall be energized from an approved receptacle out- let. 400-4. Prohibited Uses. Except where installed in accordance with Article 645, flexible cord shall not be used (1) as a substitute for the fixed wiring of a structure; (2) where run through holes in walls, ceil- ings, or floors; (3) where run through doorways, windows, or similar openings; (4) where attached to building surfaces; or (5) where con- cealed behind building walls,ceilings,or floors. 400-5. Splices. Flexible cord shall be used only in continuous lengths without splice or tap. 400-6. Cords in Show-Windows and Show-Cases. Flexible cord used in show-windows and show-cases shall be of types S, SO, SJ, SJO, ST, STO, SJT, SJTO and AFS, except for the wiring of chain supported fixtures, and for supplying current to portable lamps and other mer- chandise for exhibition purposes. 400-7. Minimum Size. Flexible cords shall not be smaller than No. 18, except that tinsel cords, or cords having equivalent characteristics, of smaller size may be approved for use with specific appliances. 400-8. Insulation—Over 300 Volts. Where the voltage between any two conductors exceeds 300, but does not exceed 600, flexible cord of No. 10 and smaller shall have rubber or thermoplastic insulation on the (Continued on page 172) -k ARTICLE 400—FLEXIBLE CORDS AND CABLES 70-171 Table 400-9(b). Ampacity of Flexible Cord Table 400-9(b) gives the allowable ampacity for not more than three current-carrying conductors in a cord. If the number of current-carry- ing conductors in a cord is from four to six, the allowable ampacity of each conductor shall be reduced to 80 per cent of the values for not more than three current-carrying conductors in the Table. A conductor used for equipment grounding and a neutral conductor which carries only the unbalanced current from other conductors, as in the case of normally balanced circuits of three or more conductors, are not con- sidered to be current-carrying conductors. Where a single conductor is used for both equipment grounding and to carry unbalanced current from other conductors, it shall be considered to be a current-carrying conductor. (See Section 250-60.) (Based on Ambient Temperature of 30°C(86°F).See Section 400-9 and Table 400-11) Size Rubber Rubber Types Types Types Cotton Types PO, C, PD, AFS, AVPO Types TP, TS E, EO, EN, AFSJ, AVPD CFPD* AWG S, SO, SRD, HC, Thermo- Si, SJO, SV, HPD, Asbestos plastic SVO, SP HSJ, Types Types - HSJO, AFC* TPT, Thermo- HS, AFPD* TSP plastic Types HSO, ET, ETP, ST, STO, HPN SRDT, SJT, SVHT SJTO, SVT SVTO, SPT At Bt 27** 0.5 18 . . 7 10 10 17 6 17 .. 12 16 . . 10 13 15 22 8 15 .. .. 17 .. 14 .. 15 18 20 28 17 12 .. 20 25 30 36 23 10 . . 25 30 35 47 28 8 . . 35 40 . . . . 6 45 55 .. . . 4 . . 60 70 . . .. . . 2 . . 80 95 . . .. . . *These types are used almost exclusively in fixtures where they are ex- posed to high temperatures and ampere ratings are assigned accordingly. **Tinsel Cord. t The ampacities under sub-heading A in Column 3 are applicable to three conductor cords and four conductor cords connected to utilization equipment, with three conductors carrying current. The ampacities under sub-heading B in Column 3 are applicable to two conductor cords and three conductor cords connected to the utilization equipment,with two conductors carrying current. NOTE 1. Ultimate Insulation Temperature. In no case shall conductors be associated together in such way with respect to the kind of circuit, the wiring method employed,or the number of conductors,that the limiting temperature of the conductors will be exceeded. NOTE 2. SVHT made only in No. 18 and 17 AWG sizes. 70-172 NATIONAL ELECTRICAL CODE (Continued from page 170) individual conductors at least 3/64 inch in thickness, unless type S, SO, ST or STO cord is used. 400-9. Overcurrent Protection and Ampacities of Flexible Cords. (a) Overcurrent Protection. Flexible cords not smaller than No. 18, and tinsel cords, or cords having equivalent characteristics, of smaller size approved for use with specific appliances, shall be considered as protected against overcurrent by the overcurrent devices described in Section 240-5. Cords shall be not smaller than required in Table 400-9 (b) for the rated current of the connected equipment. 400-10. Pull at Joints and Terminals. Flexible cords shall be so con- nected to devices and to fittings that tension will not be transmitted to joints or terminal screws. This shall be accomplished by a knot in the cord, winding with tape, by a special fitting designed for that purpose, or by other approved means which will prevent a pull on the cord from being directly transmitted to joints or terminal screws. • Notes to Table 400-11 1. Except for Types P0-1, P0-2, cations subject to excessive moisture PO, SP-1, SP-2, SPT-1, SPT-2, TP, or corrosive vapors or gases. Where TPT, and AVPO,individual conduc- steel supporting fillers are used, they tors are twisted together. shall run straight through the center 2. Type P0-1 is for use only with of the cable assembly and shall not portable lamps, portable radio re- be cabled with the copper strands of ceiving appliances, portable clocks any conductor. and similar appliances which are not Types E, EO, and EN Cables may liable to be moved frequently and incorporate in the construction No. where appearance is a consideration. 20 Gauge Conductors formed as a 3. Types TP, TPT, TS, and TST pair,and covered with suitable metal- are suitable for use in lengths not lic shielding for telephone circuits. exceeding eight feet when attached The insulation of the conductors may directly, or by means of a special be rubber or thermoplastic of thick- type of plug, to a portable appli- ness specified for Type E and EO ance rated at 50 watts or less and of Cables.The shield shall have its own such nature that extreme flexibility protective covering. This component of the cord is essential. may be incorporated in any layer of 4. Rubber-filled or varnished cam- the cable assembly,and shall not run bric tapes may be substituted for the straight through the center. inner braids. 7. A third conductor in these ca- 5. Types S, SO, and ST are suit- bles is for grounding purposes only. able for use on theater stages, in ga- 8. The individual conductors of rages and elsewhere, where flexible all cords except those of heat-resist- cords are permitted by this Code. ant cords (Types AFC,AFPD,AFS, 6. Traveling cables for operating, AFSJ, AVPO, AVPD and CFPD) control and signal circuits may have shall have a rubber or thermoplastic one or more nonmetallic fillers or insulation, except that the grounding may have a supporting filler of conductor where used,shall be in ac- stranded steel wires having its own cordance with Paragraph 400-14(b). protective braid or cover. Cables ex- A rubber compound shall be vulcan- ceeding 100 feet in length shall have ized except for heater cords (Types steel supporting fillers, except in lo- HC,HPD and HSJ). ARTICLE 400—FLEXIBLE CORDS AND CABLES 70-173 voq -0 W '000 '- c0 17004 -a to ... 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U a k�. .. z O � 0� P. 0 o0 0 ¢ I ¢ x x x x x x Z(/) 0 S.. 0 Z Ua ° b Ua ~ m ti 0 U 0 cd 0 F. t. a`ni U -x "Cl -0xo ° 0 A ai 0 0 COau 8 - `do z r .0 a)�, id .n yU xxU d o ay•„ a) p U al o a x x � a. cn ARTICLE 400—FLEXIBLE CORDS AND CA ke 70-177 2 ) �` \0 ky ct\ G } Z CA� \\ j\ P. / ]; { / § ; i 2 � a§ a§ 3 = e2 ea Ba / ! k/ el 0... ° ° § �§ § /° z $ o & [ {/ \ // 7 jam\ CO CO , § m= >th ;f"k j 0 j 0 ]Qa2 i45j \QG/ 2 \ \ \) d § \ /i4/ + + \/� k s k ' { f�{ Bc 0 s o t ( , e� ± E 0 / �\// \ {} i)\ 2/ / \ \/)/ƒ //ƒ f0 00 0 0 0 0 0 0 j / \ � \( � k\ \\ ®� � \_04 0 \ 2 a/ \ 0 00 o ) / k N N N N j § 5 \ - I \ - 00 - ] / < < Cl) \ /� 4 0 / ! r'0 \ § « /\j / %]\ @± \ 777 0X / eQ \/ { § ku 2 crl 70-178 NATIONAL ELECTRICAL CODE 0 0 0 ^0 -0 N O O x � � � COx za xa za 41a x co a.= a C •-. �U a>T 0az g d) o) 8 N 0 c b o 0 dwat "" c 0 ti dwai ^ :; 0 u oog ;? a, . 0 oo � a� „ Ti, 0 d 0 e.41z 0 o 8xz to 2 13.4z FOa: y Oz[-,:;� FOrx v� E'er., `O N ° 0 0 O W-0 p >,° + . m � cC z4 CO CO 0 0 w R.' RS O 6 0 O v Ea .0 N 0 S °. E-71 a E-, , a O 0 V 6., O-0 O Z c0 O E u N .0 e0 '7 « N3 i as a ° b U ° 0.« a' a �" �. 2 W Z W z Z E. co O e y E a Z h e I-. 0 y 0 0 I z WU ARTICLE 400—FLEXIBLE CORDS AND CABLES 70-179 C. Construction Specifications 400-12. Labels. Flexible cords shall be examined and tested at the factory and shall be labeled before shipment. 400-13. Grounded Conductor Identification. One conductor of flexible cords which is intended to be used as a grounded circuit conductor shall have a continuous marker readily distinguishing it from the other con- ductor or conductors. The identification shall consist of one of the fol- lowing: (a) Colored Braid. A braid finished to show a white or natural gray color and the braid on the other conductor or conductors finished to show a readily distinguishable solid color or colors. (b) Tracer in Braid. A tracer in a braid of any color contrasting with that of the braid and no tracer in the braid of the other conductor or conductors. No tracer shall be used in the braid of any conductor of a flexible cord which contains a conductor having a braid finished to show white or natural gray,except, in the case of Types C, PD and PO cords having the braids on the individual conductors finished to show white or natural gray. In such C, PD and PO cords the identifying marker may consist of the solid white or natural gray finish on one conductor provided there is a colored tracer in the braid of each other conductor. (c) Colored Insulation. A white or natural gray insulation on one conductor and insulation of a readily distinguishable color or colors on the other conductor or conductors for cords having no braids on the individual conductors (except cords which have insulation on the in- dividual conductors integral with the jacket). The insulation may be covered with an outer finish to provide the desired color. (d) Colored Separator. A white or natural gray separator on one conductor and a separator of a readily distinguishable solid color on the other conductor or conductors of cords having insulation on the individual conductors integral with the jacket. (e) Tinned Conductors. One conductor having the individual strands tinned and the other conductor or conductors having the individual strands untinned for cords having insulation on the individual conduc- tors integral with the jacket. (f) Surface Marking. A stripe, ridge or groove so located on the exterior of the cord as to identify one conductor for cords having in- sulation on the individual conductors integral with the jacket. 400-14. Grounding Conductor Identification. A conductor intended to be used as a grounding conductor shall have a continuous identifying marker readily distinguishing it from the other conductor or conduc- tors. Conductors having a continuous green color or a continuous green color with one or more yellow stripes shall not be used for other than grounding purposes. The identifying marker shall consist of one of the following: (a) Colored Braid. A braid finished to show a continuous green color or a continuous green color with one or more yellow stripes. 70-180 NATIONAL ELECTRICAL CODE (b) Colored Insulation or Covering. For cords having no braids on the individual conductors, an insulation of a continuous green color or a continuous green color with one or more yellow stripes. 400-15. Insulation Thickness. The nominal thickness of rubber or ther- moplastic conductor insulation in Types TS, TST, P0-1, SV, SVT, and SVHT shall be not less than 1/64 inch. The nominal thickness of rubber insulation in Types HC,HPD,HSJ,and HS shall be not less than 1/64 inch for the Nos. 18-16 AWG sizes, and not less than 2/64 inch for the Nos. 14-12 AWG sizes. For heater cord other than Types HC and HPN,the all Neoprene insulation shall be 2/64 inch for No. 18 and No. 16 AWG sizes and 3/64 inch for No. 14 and No. 12 AWG sizes. The nominal thickness of the thermoplastic insulation in Type ET and ETP elevator cable shall be not less than 20 mils for the No. 18 and No. 16 AWG size and not less than 1/32 inch for the No. 14 AWG size. The nominal thickness of the rubber insulation in Types E, EO, and EN elevator cables shall be not less than 20 mils for the No. 18 and 16 AWG sizes and not less than 2/64 inch for the No. 14 AWG size for ratings not exceeding 300 volts. The nominal thickness of latex- rubber insulation, when employed, in Types SJ, SJO, S and SO shall be not less than 15 mils for the Nos. 18-16 AWG sizes and not less than 18 mils for the No. 14 AWG and larger sizes. The nominal thickness of conductor insulation in Types PO,SP-2,SPT-2, HPN, SRD, and SRDT shall be not less than 3/64 inch.The nominal thickness of thermoplastic insulation in Type SPT-3 shall be not less than 4/64 inch for sizes 18- 16 and 5/64 inch for No. 14, 6/64 inch for No. 12 and 7/64 inch for ' No. 10 AWG. For other types, the minimum nominal thickness of rub- ber or thermoplastic conductor insulation shall be as follows: size AWG 27, and 18 to 16-2/64 inch; 14 to 10-3/64 inch; 8 to 2-4/64 inch. 400-16. Attached to Receptacle Plugs. Where a flexible cord is pro- vided with a grounding conductor and equipped with an attachment plug,the plug shall comply with Paragraphs 250-59(a and b). ARTICLE 402—FIXTURE WIRES 402-1. Use. Fixture wires are designed for installation in lighting fix- tures and in similar equipment where enclosed or protected and not subject to bending or twisting in use. Also, they are used for connecting lighting fixtures to the conductors of the circuit that supplies the fixtures. For application in lighting fixtures,see Article 410. IFixture wires are not intended for installation as branch circuit conductors, except as permitted in Article 725. ' 402-2. Minimum Size. Fixture wires shall not be smaller than No. 18. 402-3. Insulation. (a) The rubber insulations include those made from natural and synthetic rubber, neoprene and other vulcanized materials. Thermoplastic insulation may stiffen at temperatures below minus 10°C. (14°F.) and care should be used in its installation at such temperatures. It ARTICLE 402—FIXTURE WIRES 70-181 may be deformed when subject to pressure; care should be taken in its in- stallation, as for example, at bushings, or points of support. See Section 373-6(b). (b) No conductor shall be used under such conditions that its tem- perature, even when carrying current, will exceed the temperature specified in Table 310-2(a) for the type of insulation involved. Table 402-4. Allowable Ampacity of Fixture Wire (Based on Ambient Temperature of 30°C.,86°F.) Size AWG Fixture Wire Thermoplastic Types TF, TFF,TFN,TFFN Cotton Type CF* Asbestos Type AF* Silicone Rubber Types Rubber Types SF-1*,SF-2*,SFF-1*,SFF-2* RF-1,RF-2,FF-1, Fluorinated Ethylene FF-2,RFH-1,RFH-2, Propylene Types PF*, FFH-1,FFH-2 PGF*,PFF*,PGFF* 18 5 6 16 7 8 14 17 *These types are used almost exclusively in fixtures where they are ex- posed to high temperatures and ampere ratings are assigned accordingly. Ultimate Insulation Temperature. In no case shall conductors be associated together in such a way with respect to the kind of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of the conductors will be exceeded. 402-5. Overcurrent Protection. See Section 240-5.Exception No.3. 70-182 NATIONAL ELECTRICAL CODE Table 402-6. Fixture Wire Trade Type Thickness of Outer Name Letter Insulation Insulation Covering RF-1 Code Rubber 18 1/64 Inch Nonmetallic Rubber-Coy- Covering ered Fixture Wire Solid or Code Rubber 18-16 2/64 Inch 7-Strand RF-2 Nonmetallic Latex Rubber 18-16 18 Mils Covering Rubber-Coy- FF-1 Code Rubber 18 1/64 Inch Nonmetallic vered Fixture Covering Wire Flexible Stranding Code Rubber 18-16 2/64 Inch Nonmetallic FF-2 Covering Latex Rubber 18-16 18 Mils Heat Resist- RFH-1 Heat-Resist- Nonmetallic ant Rubber- ant Rubber 18 1/64 Inch Covering Covered Fix- ture Wire Heat-Resist- Solid or RFH-2 ant Rubber 18-16 2/64 Inch 7-Strand Nonmetallic Heat-Resist- Covering ant Latex 18-16 18 Mils Rubber Heat Resist- FFH-1 Heat-Resist- Nonmetallic ant Rubber- ant Rubber 18 1/64 Inch Covering Covered Fix- ture Wire Heat-Resist- Nonmetallic Flexible ant Rubber 18-16 2/64 Inch Covering Stranding FFH-2 Heat-Resist- ant Latex Rubber 18-16 18 Mils Thermoplas- tic-Covered Fixture Wire TF Thermoplas- 18-16 2/64 Inch None —Solid or tic Stranded Thermoplas- tic-Covered Fixture Wire TFF Thermoplas- None —Flexible tic 18-16 2/64 Inch Stranding Heat Resist- ant Thermo- plastic-Coy- TFN Thermoplas- Nylon ered Fixture tic 18-16 15 Mils Jacketed Wire—Solid or Stranded ARTICLE 402—FIXTURE WIRES 70-183 Table 402-6(Continued) Trade Type Thickness of Outer Name Letter Insulation Insulation Covering Heat Resist- ant Thermo- plastic-Coy- TFFN Thermoplas- Nylon ered Fixture tic 18-16 15 Mils Jacketed Wire—Flexi- ble Stranded Cotton-Cov- ered,Heat- CF Impregnated None Resistant, Cotton 18-14 2/64 Inch Fixture Wire Asbestos- Covered, Heat-Resist- AF Impregnated None ant,Fixture Asbestos 18-14 2/64 Inch Wire Silicone In- SF-1 Silicone Nonmetallic sulated Fix- Rubber 18 1/64 Inch Covering ture Wire Solid or SF-2 Silicone Nonmetallic 7-Strand Rubber 18-14 1/32 Inch Covering Silicone In- SFF-1 Silicone Nonmetallic sulated Fix- Rubber 18 1/64 Inch Covering ture Wire Flexible SFF-2 Silicone Nonmetallic Stranding Rubber 18-14 1/32 Inch Covering Fluorinated Fluorinated 18-14 20 Mils None Ethylene PF Ethylene Propylene Propylene Fixture Wire PGF Solid or 7 18-14 14 Mils Glass Strand Braid Fluorinated Fluorinated 18-14 20 Mils None Ethylene PFF Ethylene Propylene Propylene Fixture Wire PGFF Flexible 18-14 14 Mils Glass Stranding Braid 70-184 NATIONAL ELECTRICAL CODE ARTICLE 410 — LIGHTING FIXTURES, LAMPHOLDERS, LAMPS, RECEPTACLES AND ROSETTES A. General 410-1. Scope. Lighting fixtures, lampholders, pendants, receptacles, and rosettes, incandescent filament lamps, arc lamps, electric discharge lamps, the wiring and equipment forming part of such lamps, fixtures and lighting installations shall conform to the provisions of this Article, except as otherwise provided in this Code. 410-2. Application to Other Articles. Equipment for use in hazardous locations shall conform to Articles 500 to 517. 410-3. Live Parts. Fixtures, lampholders, lamps, rosettes and recepta- cles shall have no live parts normally exposed to contact, except in the case of cleat-type lampholders, receptacles and rosettes which are lo- cated at least 8 feet above the floor. Lampholders, receptacles and switches which have exposed accessible terminals shall not be installed in metal fixture canopies or in open bases of portable table or floor lamps. B. Provisions for Fixture Locations 410-4. Fixtures in Damp,Wet or Corrosive Locations. (a) Fixtures installed in damp or wet locations shall be approved for such locations and shall be so constructed or installed that water can- not enter or accumulate in wireways, lampholders or other electrical parts. All fixtures installed in wet locations shall be marked, "Suitable for Wet Locations." All fixtures installed in damp locations shall be marked, "Suitable for Wet Locations" or "Suitable for Damp Loca- tions." Installations undergroti d or in concrete slabs or masonry in direct contact with the earth, and loca�ions subject to saturation with water or other liquids, such as locations' exposed to weather and unprotected, vehicle washing areas, and like locations, are considered to be wet locations with respect to the above requirement. Interior locations protected from weather but subject to moderate degrees of moisture, such as basements, some barns, some cold storage warehouses and the like, and partially protected locations under canopies, marquees, roofed open porches, and the like, are considered to be damp locations with respect to the above requirement. (b) Fixtures installed in corrosive locations shall be of a type ap- proved for such locations. See Section 210-21 (b) for receptacles in fixtures. 410-5. Fixtures near Combustible Material. Fixtures shall be so con- structed, or installed, or equipped with shades or guards that combusti- ble material will not be subjected to temperatures in excess of 90° C (194° F). 410-6. Fixtures over Combustible Material. Lampholders installed over highly combustible material shall be of the unswitched type and ARTICLE 410—LIGHTING FIXTURES, ETC. 70-185 unless an individual switch is provided for each fixture, shall be lo- cated at least 8 feet above the floor, or shall be otherwise so located or guarded that the lamps cannot be readily removed or damaged. 410-7. Fixtures in Show-Windows. Externally wired fixtures shall not be used in a show-window. Exception: Fixtures of the chain-supported type may be externally wired. 410-8. Fixtures in Clothes Closets. (a) A fixture in a clothes closet shall be installed: (1) On the wall above the closet door, provided the clearance from the fixture to a storage area where combustible material may be stored within the closet is not less than 18 inches,or (2) On the ceiling or wall over an area which is unobstructed to the floor, maintaining an 18-inch clearance upward and horizontally from the fixture to a storage area where combustible material may be stored within the closet. NOTE: A flush recessed fixture equipped with a solid lens is consid- ered to be outside the closet area. (b) Pendants shall not be installed in clothes closets. 410-9. Space for Cove Lighting. Coves shall have adequate space and shall be so located that lamps and equipment can be properly installed and maintained. C. Provisions at Fixture Outlet Boxes,Canopies and Pans 410-10. Space for Conductors. Canopies and outlet boxes taken to- gether shall provide adequate space so that fixture conductors and their connecting devices may be properly installed. 410-11. Temperature Limit of Conductors in Outlet Boxes. Fixtures shall be of such construction or so installed that the conductors in out- let boxes shall not be subjected to temperatures greater than that for which the conductors are approved. Branch circuit wiring shall not be passed through an outlet box that is an integral part of an incandescent fixture unless the fixture is ap- proved for the purpose. 410-12. Outlet Boxes to be Covered. In a completed installation, each outlet box shall be provided with a cover unless covered by means of a fixture canopy,lampholder,receptacle,rosette,or similar device. 410-13. Covering of Combustible Material at Outlet Boxes. Any com- bustible wall or ceiling finish exposed between the edge of a fixture canopy or pan and an outlet box shall be covered with noncombustible material. 410-14. Connection of Electric Discharge Lighting Fixtures. Electric dis- charge lighting fixtures when supported independently of the outlet box shall be connected through metal raceways, metal-clad cable or non- metallic sheathed cable. This requirement may be waived when cord equipped fixtures are suspended directly below the outlet box and the 70-186 NATIONAL ELECTRICAL CODE exposed cord is not subject to strain or physical damage. Such cord equipped fixtures shall terminate at the outer end of the cord in a grounding type attachment plug (cap) or busway plug. Fixtures may be connected in accordance with Section 364-11. D. Fixture Supports 410-15. Supports—General. Fixtures, lampholders, rosettes and re- ceptacles shall be securely supported. A fixture which weighs more than 6 lbs.or exceeds 16 inches in any dimension shall not be supported by the screw shell of a lampholder. 410-16. Means of Support. Where the outlet box or fitting will pro- vide adequate support, a fixture shall be attached thereto; otherwise a fixture shall be supported as required by Section 370-13. A fixture which weighs more than 50 lbs. shall be supported independently of the outlet box. E. Wiring of Fixtures 410-17. Fixture Wiring—General. Wiring on or within fixtures shall be neatly arranged and shall not be exposed to physical damage. Excess wiring shall be avoided. Conductors shall be so arranged that they shall not be subjected to temperatures above those for which they are ap- proved. 410-18. Conductor Size. Fixture conductors shall not be smaller than No. 18 AWG. 410-19. Conductor Insulation. (a) Fixtures shall be wired with conductors having insulation suit- able for the current, voltage, and temperature to which the conductors will be subjected. (b) Where fixtures are installed in damp, wet, or corrosive locations, conductors shall be of a type approved for such locations. (c) For ampacity of fixture wire,see Table 402-4. (d) For maximum operating temperature and voltage limitation of fixture wires,see Section 310-2. 410-20. Conductors for Certain Conditions. (a) Fixtures provided with Mogul base screw-shell lampholders and operating at not more than 300 volts between conductors shall be wired with Type AF, SF-1, SF-2, SFF-1, SFF-2, PF, PGF, PFF, or PGFF fixture wire. (b) Fixtures provided with other than Mogul base screw shell lamp- holders and operating at not more than 300 volts between conductors shall be wired with Type AF, SF-1, SF-2, PF, PGF, PFF, PGFF fix- ture wire or Type AFC,or AFPD flexible cord. Exception No. 1. Where temperatures do not exceed 90°C (194°F), Type CF, TFN and TFFN fixture wire or Type CFPD, flexi- ble cord may be used. Exception No. 2. Where temperatures exceed 60°C (140°F) but are not higher than 75°C (167°F) Type RH and RHW rubber-covered wire, Type RFH-1, RFH-2, FFH-1, and FFH-2 fixture wires may be used. ARTICLE 410—LIGHTING FIXTURES, ETC. 70-187 Exception No. 3. Where temperatures do not exceed 60° C (140° F), Type T thermoplastic wire, Types TF and TFF fixture wire, and Types RF-1,RF-2,FF-1,FF-2 fixture wires may be used, including use in fixtures of decorative type on which lamps of not over 60-watt rating are used in connection with imitation candles. See Sections 402-6 and 310-2 for fixture wires and conductors; also, Table 400-9(b) for flexible cords. 410-21. Conductors for Movable Parts. (a) Stranded conductor shall be used for wiring on fixture chains and on other movable or flexible parts. (b) Conductors shall be so arranged that the weight of the fixture or movable parts will not put a tension on the conductors. 410-22. Pendant Conductors for Incandescent Filament Lamps. (a) Pendant lampholders with permanently attached leads, where used in other than festoon wiring, shall be hung from separate stranded rubber-covered conductors which are soldered directly to the circuit conductors but supported independently thereof. (b) Such pendant conductors shall be not smaller than No. 14 AWG for heavy-duty or medium-base screw-shell lampholders, nor, except for approved Christmas tree and decorative lighting outfits, smaller than No. 18 AWG for intermediate or candelabra-base lampholders. (c) Pendant conductors longer than 3 feet shall be twisted together where not cabled in an approved assembly. 410-23. Protection of Conductors and Insulation. (a) Conductors shall be secured in a manner that will not tend to cut or abrade the insulation. (b) Conductor insulation shall be protected from abrasion where it passes through metal. (c) Individual showcases, other than fixed, may be connected by flex- ible cord to permanently installed receptacles, and groups of not more than six such showcases may be coupled together by flexible cord and separable locking-type connectors with one of the group connected by flexible cord to a permanently installed receptacle. The installation shall comply with the following requirements: (1) Flexible cord shall be hardservice type, having conductors not smaller than the branch circuit conductors, having ampacity at least equal to the branch circuit overcurrent device, and having an equipment grounding-conductor.See Table 250-95. (2) Receptacles, connectors and plugs (caps) shall be of an ap- proved grounding type rated 15 or 20 amperes. (3) Flexible cords shall be secured to the undersides of showcases so that: (a) Wiring will not be exposed to mechanical damage. (b) Will allow a separation between cases not in excess of two inches, nor more than 12 inches between the first case and the supply receptacle. 70-188 NATIONAL ELECTRICAL CODE (c) The free lead at the end of a group of showcases will have a female fitting not extending beyond the case. (4) Equipment other than showcases shall not be electrically con- nected to showcases. (5) Standpipes of floor receptacles shall allow floor cleaning equip- ment to be operated without damage to receptacles. 410-24. Conductor Protection at Lampholders. Where a metal lamp- holder is attached to a flexible cord, the inlet shall be equipped with an insulating bushing which, if threaded, shall not be smaller than nominal 3/8 inch pipe size. The cord hole shall be of a size appropriate for the cord and all burrs and fins removed in order to provide a smooth bearing surface for the cord. Bushings having holes 9/32 inch in diameter are suitable for use with plain pendant cord and holes 13/32 inch in diameter with reinforced cord. 410-25. Connections,Splices and Taps. (a) Fixtures shall be so installed that the connections between the fixture conductors and the circuit conductors may be inspected without requiring the disconnection of any part of the wiring, unless the fixture is connected by means of a plug and receptacle. (b) Splices and taps shall not be located within fixture arms or stems. (c) No unnecessary splices or taps shall be made within or on a fix- ture. (d) For approved means of making connections, see Sections 110-14 and 110-15. 410-26. Fixture Raceways. Fixtures shall not be used as a raceway for circuit conductors unless the fixtures meet the requirements for ap- proved raceways, except that the conductors of the single branch cir- cuit supplying the fixtures may be carried through as follows: Exception No. 1. An installation of fixtures approved for end to end assembly to form a continuous raceway,or Exception No. 2. Fixtures which are connected together by approved wiring methods. Branch circuit conductors within 3 inches of a ballast within the bal- last compartment shall be recognized for use at temperatures not lower than 90° C. (194°F.), such as Type RHH, THHN, FEP, FEPB, SA, XHHW and AVA.See Table 310-2(a) for Type THW—MTW. 410-27. Polarization of Fixtures. Fixtures shall be so wired that the screw-shells of lampholders will be connected to the same fixture or circuit conductor or terminal. For polarity identification of conductors to screw-shells of lampholders,see Section 200-8. F. Construction of Fixtures 410-28. Combustible Shades and Enclosures. Adequate air space shall be provided between lamps and shades or other enclosures of combusti- ble material. ARTICLE 410—LIGHTING FIXTURES, ETC. 70-189 410-29. Fixture Rating. (a) All fixtures requiring ballasts or transformers shall be plainly marked with their electrical rating and the manufacturer's name, trade- mark or other suitable means of identification. (b) The electrical rating shall include the voltage and frequency, and shall indicate the current rating of the unit including the ballast, transformer or auto-transformer. 410-30. Design and Material. Fixtures shall be constructed of metal, wood, or other approved material and shall be so designed and assem- bled as to secure requisite mechanical strength and rigidity. Wireways, including the entrances thereto, shall be such that conductors may be drawn in and withdrawn without injury. 410-31. Nonmetallic Fixtures. In all fixtures not made entirely of metal, wireways shall be lined with metal unless approved armored or lead-covered conductors with suitable fittings are used. 410-32. Mechanical Strength. (a) Tubing used for arms and stems where provided with cut threads shall be not less than 0.040 inch in thickness and when provided with rolled (pressed) threads shall be not less than 0.025 inch in thickness. Arms and other parts shall be fastened to prevent turning. (b) Metal canopies supporting lampholders, shades, etc., exceeding 8 lbs., or incorporating attachment plug receptacles, shall be not less than 0.020 inch in thickness. Other canopies shall be not less than 0.016 inch when made of steel and not less than 0.020 inch when of other metals. (c) Pull type canopy switches shall not be inserted in the rims of metal canopies which are less than 0.025 inch in thickness unless the rims are reinforced by the turning of a bead or the equivalent. Pull type canopy switches, whether mounted in the rims or elsewhere in sheet metal canopies, shall be located not more than 3 i/2 inches from the cen- ter of the canopy. Double set screws, double canopy rings, a screw ring, or equal method shall be used where the canopy supports a pull type switch or pendant receptacle. The above thickness requirements apply to measurements made on finished (formed) canopies. 410-33. Wiring Space. Bodies of fixtures, including portable lamps, shall provide ample space for splices and taps and for the installation of devices, if any. Splice compartments shall be of nonabsorptive, non- combustible material. 410-34. Fixture Studs. Fixture studs which are not parts of outlet boxes, hickeys, tripods, and crowfeet shall be made of steel, malleable iron,or other approved material. 410-35. Insulating Joints. Insulating joints shall be composed of ma- terials especially approved for the purpose. Those which are not de- signed to be mounted with screws or bolts shall have a substantial exte- rior metal casing,insulated from both screw connections. 410-36. Portable Lamps. Portable table and floor lamps and fan mo- tors on ceiling fixtures may be wired with approved rubber-covered 70-190 NATIONAL ELECTRICAL CODE conductors,provided the wiring is not located so as to be subject to un- due heating from lamps. 410-37. Portable Handlamps. Handlamps of the portable type sup- plied through flexible cords shall be of the molded composition or other type approved for the purpose. Metal-shell paper-lined lampholders shall not be used. Handlamps shall be equipped with a handle. Where subject to physical damage or where lamps may come in contact with combustible material, handlamps shall be equipped with a substantial guard attached to the lampholder or the handle. For garages,see Section 511-6. 410-38. Cord Bushings. A bushing or the equivalent shall be provided where flexible cord enters the base or stem of a portable lamp. The bushing shall be of insulating material unless a jacketed type of cord is used. 410-39. Tests. All wiring shall be free from short-circuits and grounds, and shall be tested for these defects prior to being connected to the circuit. 410-40. Live Parts. Exposed live parts within porcelain fixtures shall be suitably recessed and so located as to make it improbable that wires will come in contact with them. There shall be a spacing of at least V2 inch between live parts and the mounting plane of the fixture. G. Installation of Lampholders 410-41. Screw-Shell Type. Lampholders of the screw-shell type shall be installed for use as lampholders only. 410-42. Double-Pole Switched Lampholders. Where used on unidenti- fied 2-wire circuits tapped from the ungrounded conductors of multi- wire circuits, the switching device of lampholders of the switched type shall simultaneously disconnect both conductors of the circuit. See Sec- tion 200-5. 410-43. Lampholders in Damp or Wet Locations. Lampholders in- stalled in damp or wet locations shall be of the weatherproof type. H. Construction of Lampholders 410-44. Insulation. The outer metal shell and the cap shall be lined with insulating material which shall prevent the shell and cap from be- coming a part of the circuit. The lining shall not extend beyond the metal shell more than 1/2 inch, but shall prevent any current-carrying part of the lamp base from being exposed when a lamp is in the lamp- holding device. 410-45. Lead Wires. Lead wires, furnished as a part of weatherproof lampholders and intended to be exposed after installation, shall be of approved, stranded, rubber-covered conductors, not less than No. 14 gage (No. 18 gage for candelabra sockets), and shall be sealed in place or otherwise made raintight. 410-46. Switched Lampholders. Switched lampholders shall be of such construction that the switching mechanism interrupts the electrical con- nection to the center contact. The switching mechanism may also in- ARTICLE 410—LIGHTING FIXTURES, ETC. 70-191 terrupt the electrical connection to the screw shell when connection to the center contact is simultaneously interrupted. J. Lamps 410-49. Bases, Incandescent Lamps. An incandescent lamp for gen- eral use on lighting branch circuits shall not be equipped with a Me- dium base when rated over 300 watts, nor with a Mogul base when rated over 1,500 watts. Above 1,500 watts, special approved bases or other devices shall be used. 410-50. Enclosures, Mercury-Vapor Lamp Auxiliary Equipment. Re- sistors or regulators for mercury-vapor lamps shall be enclosed in non- combustible cases and treated as sources of heat. 410-51. Arc Lamps. Arc lamps used in theaters shall conform to Section 520-61, and arc lamps used in projection machines shall con- form to Section 540-20. Arc lamps used on constant-current systems shall conform to the general requirements of Article 710. K. Receptacles,Cord Connectors and Attachment Plugs(Caps) 410-52. Rating and Type. (a) Receptacles installed for the attachment of portable cords shall be rated at not less than 15 amperes, 125 volts, or 10 amperes, 250 volts,and shall be of a type not suitable for use as lampholders. (b) Metallic faceplates shall be of ferrous metal not less than 0.030 inch in thickness or of nonferrous metal not less than 0.040 inch in thickness. Faceplates of insulating material shall be noncombustible and not less than 0.10 inch in thickness but may be less than 0.10 inch in thickness if formed or reinforced to provide adequate mechanical strength. 410-53. Receptacles in Floors. Receptacles located in floors shall be enclosed in floor boxes especially approved for the purpose. Exception: Where such receptacles are located in elevated floors of show-windows or other locations and when the, authority enforcing this Code judges them to be free from physical damage, moisture and dirt, the standard approved type of flush receptacle box may be used. 410-54. Receptacles in Damp or Wet Locations. Receptacles installed in damp or wet locations shall be of the weatherproof type. 410-55. Grounding Type Receptacles, Adapters, Cord Connectors and Attachment Plugs. (a) Receptacles,cord connectors and attachment plugs of the ground- ing type shall be provided with one fixed grounding member in addition to the circuit members. Exception: The grounding contacting member of grounding type at- tachment plugs on the power supply cords of portable hand-held, hand- guided or hand-supported tools or appliances may be of the movable self-restoring type on circuits operating at not to exceed 150 volts be- tween any two conductors nor 150 volts between any conductor and ground. 70-192 NATIONAL ELECTRICAL CODE (b) Grounding type receptacles, adapters,cord connectors and attach- ment plugs shall have a means for connection of a grounding conductor to the grounding member. A terminal for connection to the grounding member shall be designated by: (1) A hexagonal headed or shaped terminal screw or nut, not readily removable,and green colored;or (2) A pressure wire connector which has a green colored body (a wire barrel);or (3) A similar green colored connection device or conductor in the case of adapters. (c) In no case shall a grounding terminal or grounding type device be used for purposes other than grounding. (d) Grounding type attachment plugs and mating cord connectors and receptacles shall be so designed that the grounding connection is made before the current-carrying connections. Grounding type devices shall be designed so grounding members of attachment plugs cannot be brought into contact with current-carrying parts of receptacles or cord connectors. L. Rosettes 410-57. Approved Types. (a) Fusible rosettes shall not be installed. (b) Separable rosettes which make possible a change in polarity shall not be used. 410-58. Rosettes in Damp or Wet Locations. Rosettes installed in damp or wet locations shall be of the weatherproof type. 410-59. Rating. Rosettes shall be rated at 660 watts, 250 volts, with a maximum current rating of 6 amperes. 410-60. Rosettes for Exposed Wiring. When designed for use with ex- posed wiring, rosettes shall be provided with bases which shall have at least two holes for supporting screws, shall be high enough to keep the wires and terminals at least 1/2 inch from the surface wired over, and shall have a porcelain lug under each terminal to prevent the rosette being placed over projections which would reduce the separation to less than l inch. 410-61. Rosettes for Use with Boxes or Raceways. When designed for use with conduit boxes or wire raceways, rosette bases shall be high enough to keep wires and terminals at least 3/8 inch from the surface wired over. M. Special Provisions for Flush and Recessed Fixtures 410-62. Approved Type. Fixtures which are installed in recessed cavi- ties in walls or ceilings shall be of an approved type and shall conform to Sections 410-63 to 410-70 inclusive. 410-63. Temperature. (a) Fixtures shall be so constructed or installed that adjacent com- bustible material will not be subjected to temperatures in excess of 90°C (194°F). ARTICLE 410—LIGHTING FIXTURES, ETC. 70-193 (b) Where a fixture is recessed in fire-resistant material in a building of fire-resistant construction, a temperature higher than 90°C (194°F), but not higher than 150°C (302°F) is acceptable if the fixture is plainly marked that it is approved for that service. 410-64. Clearance. Recessed portions of enclosures, other than at points of support, shall be spaced at least 1/2 inch from combustible material and thermal insulation. 410-65. Wiring. (a) Conductors having insulation suitable for the temperature en- countered shall be used. (b) Fixtures having branch circuit terminal connections which op- erate at temperatures higher than 60°C (140°F) shall have circuit con- ductors as described in Sections 410-65 (b-1 and b-2): (1) Branch circuit conductors having an insulation suitable for the temperature encountered may be run directly to the fixture. (2) Tap connection conductors having an insulation suitable for the temperature encountered shall be run from the fixture terminal con- nection to an outlet box placed at least one foot from the fixture. Such a tap shall extend for at least four feet but not more than six feet and shall be in a suitable metal raceway. N. Construction,Flush and Recessed Fixtures 410-66. Temperature. Fixtures shall be so constructed that adjacent combustible material will not be subject to temperatures in excess of 90°C (194°F). 410-67. Enclosure. Sheet metal enclosures shall be protected against corrosion by galvanizing, plating, or other equivalent heat-resisting coating,and shall not be less than No.22 USS gage. 410-68. Lamp Wattage Marking. Incandescent lamp fixtures shall be marked to indicate the maximum allowable wattage of lamps. The markings shall be permanently installed, in letters at least 1/a inch high, and located where visible during relamping. 410-69. Solder Prohibited. No solder shall be used in the construc- tion of the fixture box. 410-70. Lampholders. Lampholders of the screw-shell type shall be of porcelain unless specially approved for the purpose. Cements, where used,shall be of the high-heat type. P. Special Provisions for Electric Discharge Lighting Systems of 1,000 Volts or Less 410-71. General. (a) Equipment for use with electric discharge lighting systems and designed for an open-circuit voltage of 1,000 volts or less shall be of a type approved for such service. (b) The terminals of an electric discharge lamp shall be considered as alive where any lamp terminal is connected to a potential of more than 300 volts. 70-194 NATIONAL ELECTRICAL CODE (c) Transformers of the oil-filled type shall not be used. (d) In addition to complying with the general requirements for light- ing fixtures,such equipment shall conform to Part P of this Article. (e) Fluorescent fixtures for indoor installations shall incorporate ballast protection. Exception: Fluorescent fixtures for indoor installations need not in- corporate ballast protection when they employ simple reactance type ballasts. 410-72. Direct-Current Equipment. Fixtures installed on direct-current circuits shall be equipped with auxiliary equipment and resistors es- pecially designed and approved for direct-current operation and the fixtures shall be so marked. 410-73. Voltages—Dwelling Occupancies. (a) Equipment having an open-circuit voltage of more than 1000 volts shall not be installed in dwelling occupancies. (b) Equipment having an open-circuit voltage of more than 300 volts shall not be installed in dwelling occupancies unless such equipment is so designed that there shall be no exposed live parts when lamps are being inserted,are in place,or are being removed. 410-74. Fixture Mounting. (a) Exposed Ballasts. Fixtures having exposed ballasts or trans- formers shall be so installed that such ballasts or transformers shall not be in contact with combustible material. (b) Combustible Low-Density Cellulose Fiberboard. Where a fixture containing a ballast is to be installed on combustible low-density cel- lulose fiberboard it shall,where surface mounted: (1) Be approved for this condition,or (2) Be spaced not less than 11/2 inches from the surface of the fiberboard. (3) Where such fixtures are partially or wholly recessed, the pro- visions of Sections 410-62 to 410-70 shall apply. Combustible low-density cellulose fiberboard is considered to include sheets, panels and tiles which have a density of 20 pounds per cubic foot or less, and which are formed of bonded plant fiber material; but does not in- clude solid or laminated wood, nor fiberboard which has a density in excess of 20 pounds per cubic foot or is an approved material which has been in- tegrally treated with fire retarding chemicals to the degree that the flame spread in any plane of the material will not exceed twenty-five as determined by the method of NFPA No. 255,ASTM Designation E-84 or U.L.No.723. 410-75. Auxiliary Equipment Not Integral with Fixture. (a) Auxiliary equipment, including reactors, capacitors, resistors, and similar equipment, where not installed as part of a lighting fixture assembly shall be enclosed in accessible, permanently installed metal cabinets. (b) Where display cases are not permanently installed, no portion of a secondary circuit may be included in more than a single case. ARTICLE 410—LIGHTING FIXTURES, ETC. 70-195 (c) Ballasts approved for separate mounting and for direct connec- tion to an approved wiring system need not be separately enclosed. 410-76. Auto-Transformers. An auto-transformer which is used as part of a ballast for supplying lighting units and which raises the volt- age to more than 300 volts shall be supplied only by a grounded system. 410-77. Switches. Snap switches shall conform to Section 380-14. Q. Special Provisions for Electric Discharge Lighting Systems of More Than 1,000 Volts 410-78. General. (a) Equipment for use with electric discharge lighting systems and designed for an open-circuit voltage of more than 1,000 volts shall be of a type approved for such service. (b) The terminal of an electric discharge lamp shall be considered as alive when any lamp terminal is connected to a potential of more than 300 volts. (e) In addition to complying with the general requirements for light- ing fixtures, such equipment shall conform to Sections 410-78 to 410- 90 inclusive. For signs and outline lighting,see Article 600. 410-79. Control. (a) Fixtures or lamp installations shall be controlled either singly or in groups by an externally operable switch or circuit breaker which shall open all ungrounded primary conductors. (b) The switch or circuit breaker shall be located within sight of the fixtures or lamps, or it may be located elsewhere if it is provided with means for locking in the open position. 410-80. Lamp Terminals and Lampholders. Parts which must be re- moved for lamp replacement shall be hinged or fastened by an ap- proved means. Lamps or lampholders or both shall be so designed that there shall be no exposed live parts when lamps are being inserted or are being removed. 410-81. Transformer Ratings. Transformers and ballasts shall have a secondary open-circuit voltage of not more than 15,000 volts with an allowance on test of 1,000 volts additional. The secondary current rat- ing shall be not more than 120 milli-amperes when the open circuit voltage is more than 7500 volts, and not more than 240 milli-amperes when the open circuit voltage is 7500 volts or less. 410-82. Transformer Type. Transformers shall be of an approved enclosed type. Transformers of other than the askarel insulated or dry type shall not be used. 410-83. Transformer Secondary Connections. (a) The high-voltage windings of transformers shall not be con- nected in series or in parallel, except that for two transformers, each having one end of its high-voltage winding grounded and connected to the enclosure, the high-voltage windings may be connected in series to form the equivalent of a mid-point grounded transformer. 70-196 NATIONAL ELECTRICAL CODE (b) The grounded ends shall be connected by an insulated conduc- I for not smaller than No. 14 AWG. 410-84. Transformer Locations. (a) Transformers shall be accessible after installation. 1 (b) The transformers should be installed as near to the lamps as practicable to keep the secondary conductors as short as possible. (c) Transformers shall be so located that adjacent combustible ma- terials will not be subjected to temperatures in excess of 90° C (194° F). 410-85. Transformer Loading. The lamps connected to any trans- former shall be of such length and characteristics as not to cause a con- dition of continuous over-voltage on the transformer. 410-86. Wiring Method. Secondary Conductors. Approved gas-tube sign cable suitable for the voltage of the circuit shall be used. For in- stallation of conductors,see Section 600-31. 410-87. Lamp Supports. Lamps shall be adequately supported as re- quired in Section 600-33. 410-88. Exposure to Damage. Lamps shall not be located where nor- mally exposed to physical damage. 410-89. Marking. Each fixture or each secondary circuit of tubing having an open-circuit voltage of more than 1,000 volts shall have a clearly legible marking in letters not less than 1/4 inch high reading "Caution volts." The voltage indicated shall be the rated open-circuit voltage. 410-90. Switches. Snap switches shall conform to Section 380-14. R. Grounding 410-91. General. Fixtures and lighting equipment shall be grounded as provided in Sections 410-92 to 410-96 inclusive. 410-92. Metallic Wiring Systems. Metal fixtures installed on outlets wired with grounded metal raceway or grounded Type AC metal-clad cable shall be grounded. 410-93. Nonmetallic Wiring Systems. Metal fixtures installed on out- lets wired with knob-and-tube work, or nonmetallic sheathed cable, on circuits operating at 150 volts or less to ground,shall be grounded. Exception No. 1. Fixtures mounted on metal or metal lath ceilings or walls may he insulated from their supports and from the metal lath by the use of insulating joints or fixture supports and canopy insulators. See Section 410-95. Exception No. 2. Fixtures not mounted on metal or metal lath ceil- ings or walls need not be insulated or grounded.See Section 410-95. Fixtures made of insulating materials, and lampholders with shells of insulating material, are recommended for use with wiring systems that do not afford a ready means for grounding the exposed noncurrent-carrying parts of fixtures and lampholders. ARTICLE 422—APPLIANCES 70-197 410-94. Equipment of More Than 150 Volts to Ground. (a) Metal fixtures, transformers and transformer enclosures on cir- cuits operating at more than 150 volts to ground shall be grounded. (b) Other exposed metal parts shall be grounded unless they are in- sulated from ground and other conducting surfaces and are inaccessible to unqualified persons, except that lamp tie wires, mounting screws, clips and decorative bands on glass lamps spaced not less than 1 i inches from lamp terminals need not be grounded. 410-95. Equipment Near Grounded Surfaces. (a) Ungrounded metal lighting fixtures, lampholders and face plates shall not be installed in contact with conducting surfaces nor within 8 feet vertically or 5 feet horizontally of laundry tubs, bath tubs, shower baths, plumbing fixtures, steam pipes or other grounded metal work or grounded surfaces. (b) Metal pull chains used at these locations shall be provided with insulating links. 410-96. Methods of Grounding. Equipment shall be considered as grounded where mechanically connected in a permanent and effective manner to metal raceway, the armor of Type AC metal-clad cable, the grounding conductor in nonmetallic sheathed cable, or to a sepa- rate grounding conductor not smaller than No. 14, provided that the raceway, armor, or grounding conductor is grounded in a manner spec- ified in Article 250. ARTICLE 422--APPLIANCES A. General 422-1. Scope. This Article shall apply to electric appliances used in any occupancy. 422-2. Live Parts. Appliances shall have no live parts normally ex- posed to contact, except for toasters, grills or other appliances in which the current-carrying parts at high temperatures are necessarily exposed. 422-3. Motor-operated Appliances. The requirements of this Article covering motor-operated appliances amend and supersede correspond- ing requirements in Article 430. B. Branch Circuit Requirements 422-5. Branch Circuit Ampacity. The provisions of this Section specify sizes of conductors capable of carrying appliance current without over- heating under the conditions specified (see Article 210). They are not intended to apply to conductors which form an integral part of the ap- pliance. (a) The branch circuit ampacity of an individual branch circuit shall not be less than the marked ampere rating of the appliance or the marked ampacity rating of an appliance having combined loads (see Section 422-32). Exception No. 1.For household cooking appliances, see Table 220-5. 70-198 NATIONAL ELECTRICAL CODE Exception No.2.For motor-operated appliances not having a marked ampacity rating the branch circuit ampacity shall be in accordance with Part B of Article 430. Exception No. 3. Except as noted in Section 210-23(b), Exception No. 1, an appliance, other than a motor-operated appliance, which is continuously loaded, the branch circuit ampacity shall not be less than 125 per cent of the marked rating. (b) For branch circuits supplying appliance and other loads, the am- pacity rating shall be determined in accordance with Section 210-24. 422-6. Branch Circuit Overcurrent Protection. Branch circuits shall be protected in accordance with Section 240-5. Exception No. 1. When the branch circuit supplies a single non- motor-operated appliance rated at 10 amperes or more, the overcurrent device rating shall not exceed 150 per cent of the appliance rating. Exception No. 2. When there is a protective device rating marked on an appliance, the branch circuit overcurrent device rating shall not ex- ceed the protective device rating marked on the appliance. C. Installation of Appliances 422-8. Flexible Cords. Flexible cords used to connect appliances shall comply with the following: (a) Heater Cords Required. All smoothing irons and portable elec- trically heated appliances rated at more than 50 watts and which pro- duce temperatures in excess of 121°C (250°F) on surfaces with which the cord is liable to be in contact shall be provided with one of the types of approved heater cords listed in Table 400-11. (b) Other Heating Appliances. All other portable electrically heated appliances shall be connected with one of the approved types of cord listed in Table 400-11, selected in accordance with the usage specified in that Table. (c) Other Appliances. Flexible cord may be used for: (1) connec- tion of portable appliances; (2) connection of stationary appliances to facilitate their frequent interchange or prevention of the transmission of noise or vibration; or (3) facilitating the removal or disconnection of fixed appliances for maintenance or repair. 422-9. Portable Immersion Heaters. Electric heaters of the portable immersion type shall be so constructed and installed that current-carry- ing parts are effectively insulated from electrical contact with the sub- stance in which immersed. The authority having jurisdiction may make exception of special applications of apparatus where suitable precaution- ary measures are followed. 422-10. Protection of Combustible Material. Each electrically heated appliance that is obviously intended by size, weight and service to be located in a fixed position shall be so placed as to provide ample pro- tection between the appliance and adjacent combustible material. 422-11. Stands for Portable Appliances. Each smoothing iron and other portable electrically heated appliance which is intended to be ap- ARTICLE 422—APPLIANCES 70-199 plied to combustible material shall be equipped with an approved stand, which may be a separate piece of equipment or may be a part of the appliance. 422-12. Signals for Heated Appliances. In other than residence occu- pancies, each electrically heated appliance, or group of electrically heated appliances, intended to be applied to combustible material, shall be installed in connection with a signal unless the appliance is provided with an integral temperature-limiting device. 422-13. Flatirons. Electrically heated smoothing irons intended for use in residences shall be equipped with approved temperature-limiting means. 422-14. Water Heaters. Each water heater shall be equipped with temperature-limiting means in addition to the control thermostat to dis- connect all ungrounded conductors, and such means shall be: (1) in- stalled to sense maximum water temperature; (2) trip-free, manually reset, or it shall use a replacement element; (3) in addition to any other devices protecting the tank against excessive temperature or pres- sure,or both. 422-15. Infrared Lamp Industrial Heating Appliances. (a) Infrared heating lamps rated at 300 watts or less may be used with lampholders of the medium-base, unswitched porcelain type, or other types approved for the purpose. (b) Screw-shell lampholders shall not be used with infrared lamps over 300 watts rating unless the lampholders are especially approved for the purpose. (c) Lampholders may be connected to any of the branch circuits of Article 210 and, in industrial occupancies, may be operated in series on circuits of more than 150 volts to ground provided the voltage rating of the lampholders is not less than the circuit voltage. Each section panel or strip carrying a number of infrared lamphold- ers (including the internal wiring of such section, panel or strip) is con- sidered an appliance. The terminal connection block of each such as- sembly is deemed an individual outlet. 422-16. Grounding. Metal frames of portable, stationary and fixed electrically heated appliances, operating on circuits above 150 volts to ground, shall be grounded in the manner specified in Article 250; pro- vided, however, that where this is impracticable, grounding may be omitted by special permission, in which case the frames shall be per- manently and effectively insulated from the ground. Refrigerators, freezers and air conditioners shall comply with the re- quirements of Sections 250-42,43 and 45. It is recommended that the frames be grounded in all cases. For methods of grounding frames of electric ranges and clothes dryers,see Sections 250-57 and 250-60. 422-17. Wall-mounted Ovens and Counter-mounted Cooking Units. (a) Wall-mounted ovens and counter-mounted cooking units com- plete with provisions for mounting and for making electrical connec- tions shall be considered as fixed appliances. 70-200 NATIONAL ELECTRICAL CODE (b) A separable connector or a plug and receptacle combination in the supply line to an oven or cooking unit used only for ease in serv- icing or for installation shall: (1) Not be installed as the disconnecting means required by Sec- tion 422-20; (2) Be approved for the temperature of the space in which it is located. D. Control and Protection of Appliances 422-20. Disconnecting Means. Each appliance shall be provided with a means for disconnection from all ungrounded conductors as required by the following Sections.Where an appliance is supplied by more than one source the disconnecting means shall be grouped and identified. 422.21. Disconnection of Fixed Appliances. (a) For fixed appliances rated at not over 300 volt amperes or '/s hp. the branch circuit overcurrent device may serve as the disconnection means. (b) For fixed appliances of greater rating the branch circuit switch or circuit breaker may, where readily accessible to the user of the appli- ance,serve as the disconnecting means. 422-22. Disconnection of Portable Appliances. (a) For portable appliances a separable connector or an attachment plug and receptacle may serve as the disconnecting means, (b) The rating of a receptacle or of a separable connector shall not be less than the rating of any appliance connected thereto, except that demand factors authorized elsewhere in this Code may be applied. (c) Attachment plugs and connectors shall conform to the following: (1) Live Parts. They shall be so constructed and installed as to guard against inadvertent contact with live parts. (2) Interrupting Capacity. They shall be capable of interrupting their rated current without hazard to the operator. (3) Interchangeability. They shall be so designed that they will not fit into receptacles of lesser rating. 422-23. Disconnection of Stationary Appliances. (a) For stationary appliances rated at not over 300 volt amperes or 1 horsepower,the branch-circuit overcurrent device may serve as the dis- connecting means. (b) For stationary appliances of greater rating the branch-circuit switch or circuit breaker may,where readily accessible to the user of the appliance,serve as the disconnecting means. (c) For cord-connected appliances such as freestanding household- type ranges and clothes dryers, a separable connector or an attach- ment plug and receptacle may serve as the disconnecting means. At- tachment plugs and connectors shall conform to Section 422-22(c). ARTICLE 422—APPLIANCES 70-201 For household electric ranges,a plug and receptacle connection at the rear base of a range, if it is accessible from the front by removal of a drawer, is considered as meeting the intent of this rule. 422-24. Unit Switches as Disconnecting Means. Unit switches which are a part of an appliance shall not be considered as taking the place of the disconnecting means required by Part D (Control and Protection of Ap- pliances) of this Article, unless there are other means for disconnection as follows: (a) Multi-Family Dwellings. In multi-family (more than two) dwell- ings, the disconnecting means shall be within the apartment, or on the same floor as the apartment in which the appliance is installed, and may control lamps and other appliances. (b) Two-Family Dwellings. In two-family dwellings, the disconnect- ing means may be outside the apartment in which the appliance is in- stalled. This will permit an individual switch for the apartment to be used. (c) Single-Family Dwellings. In single-family dwellings, the service disconnecting means may be used. (d) Other Occupancies. In other occupancies, the branch-circuit switch or circuit breaker, where readily accessible to the user of the appliance,may be used for this purpose. 422-25. Switch and Circuit Breaker to be Indicating. Switches and cir- cuit breakers used as disconnecting means shall be of the indicating type. 422-26. Location of Disconnecting Means for Motor-driven Appliances. When a switch or circuit breaker serves as the disconnecting means for a stationary or fixed motor-driven appliance of more than 1/s horse- power, it shall be located within sight of the motor controller or shall be capable of being locked in the open position. 422-27. Overcurrent Protection. (a) Appliances shall be considered as protected against overcurrent when supplied by branch circuits as specified in Sections 422-5 and 422-6. Exception: Motors of motor-operated appliances shall be provided with overload protection in accordance with Part C of Article 430. When appliance protective devices separate from the appliance are required, data for selection of these devices shall be marked on the appliance. The minimum marking shall be that specified in Section 430-7. (b) A household type appliance with surface heating elements and which has a maximum demand of more than 60 amperes as calculated in accordance with Table 220-5 shall have its power supply subdivided into two or more circuits, each of which is provided with overcurrent protection rated at not more than 50 amperes. (c) Infrared lamp heating appliances shall have overcurrent protec- tion not exceeding 50 amperes. (d) Open-coil or exposed sheathed-coil types of surface heating ele- ments in commercial type heating appliances shall be protected by over- current protection devices which are rated at not more than 50 amperes. 70-202 NATIONAL ELECTRICAL CODE E. Marking of Appliances 422-30. Nameplate. (a) Each electric appliance shall be provided with a nameplate,giving the identifying name and the rating in volts and amperes, or in volts and watts unless marked in accordance with Section 422-32. When the appliance is to be used on a specific frequency or frequencies, it shall be so marked. Where motor overload protection external to the appliance is re- quired, the appliance shall be so marked. See Section 422-27(a) Excep- tion. (b) This marking shall be located so as to be visible or easily accessi- ble after installation. 422-31. Marking of Heating Elements. All replaceable heating elements rated more than one ampere which are a part of an appliance shall be legibly marked with the rating in volts and amperes, or in volts and watts. 422-32. Appliance Consisting of Motors and Other Loads. The mark- ing on an appliance shall specify the rating of the motor in volts and amperes, and the additional load (heaters, lights, etc.) in volts and watts or amperes. Exception No. 1—Portable Appliances. Exception No. 2 —Fixed or stationary appliances employing a mo- tor 1/20 hp or less. F. Provisions for Room Air-conditioning Units 422-40. General. The provisions of Sections 422-41 to -43 inclusive shall apply to electrically energized room air-conditioning units which control temperature and humidity. For the purpose of these Sections a room air-conditioner is an alternating-current hermetic type air-cooled window,console or in-wall air-conditioner which is installed in the con- ditioned room. It covers equipment rated not greater than 250 volts, single phase. It also applies to such an air-conditioner, if it has provi- sions for heating. 422-41. Grounding. See Sections 250-42,43 and 45. 422-42. Branch Circuit Requirements. (a) The total marked rating of motor-operated air-conditioning equip- ment shall not exceed 80 per cent of the rating of a branch circuit which does not supply lighting units or other appliances. (b) The total marked rating of air-conditioning equipment shall not exceed 50 per cent of the rating of a branch circuit where lighting units or other appliances are also supplied. (c) The nameplate marking of a room air-conditioner shall be used in determining the branch circuit requirements, and each unit shall be considered as a single-motor unit unless the nameplate is otherwise marked. When marked to indicate two or more motors, see Section 430-53. 422-43. Disconnecting Means. A separable connector or an attach- ment plug and receptacle may serve as the disconnecting means. ARTICLE 424—FIXED ELECTRIC SPACE HEATING 70-203 422-44. Supply Cords. Where flexible cords are used to supply air conditioning equipment the length of such cords shall not exceed: (1) 10 feet for nominal 125 volt rating, and (2) 6 feet for nominal 250 volt rating. ARTICLE 424—FIXED ELECTRIC SPACE HEATING EQUIPMENT A. General 424-1. Scope. The requirements of this Article shall apply to fixed equipment used for space heating. It also covers fixed outdoor electric de-icing and snow melting installations.Equipment shall be of a type ap- proved for the purpose and location where installed. For the purpose of this Article, heating equipment may be heating cable, unit heaters, boilers, central systems, or other approved fixed heating equipment. This Article does not cover process heating and room air-conditioning. 424-2. Application of Other Articles. All requirements of the National Electrical Code shall apply where applicable. Fixed electric heating equipment for use in hazardous locations shall be installed to conform with Articles 500 through 517 inclusive.Motor driven fan forced heaters with motors over 1 horsepower shall also comply with Article 430. 424-3. (a) Branch Circuit Requirements. Fixed heating equipment shall be supplied by branch circuits rated 15, 20 or 30 amperes. An in- dividual branch circuit may supply any load. Exception:Fixed infra-red heating equipment may be supplied from branch circuits rated not more than 50 amperes as provided in Section 424-23. (b) Branch Circuit Sizing. Fixed space heating equipment shall be considered as a continuous load for sizing branch circuits. The ampacity of branch circuit conductors supplying fixed space heat- ing equipment consisting of resistance elements with or without a motor shall be calculated on the basis of 125 per cent of the total load of the motors and the heaters. The ampacity of the branch circuit conductors supplying fixed space heating equipment consisting of mechanical refrigeration with or with- out resistance'units shall be calculated as provided for in Section 430-25. B. Installation 424-9. General. All heating equipment shall be installed in an ap- proved manner. 424-10. Special Type Heaters. Fixed electrical space heating systems employing methods of installation other than covered by this Article may be used only by special permission. 424-11. Supply Conductors. Equipment requiring supply conductors with over 60°C insulation shall be clearly and permanently marked. 70-204 NATIONAL ELECTRICAL CODE This marking shall be plainly visible after installation and may be ad- jacent to the field connection box. 424-12. Locations. (a) Fixed space heating equipment shall not be used where exposed to severe physical damage unless adequately protected. (b) Heaters and related equipment installed in damp or wet locations shall be approved for such locations and shall be constructed and in- stalled so that water cannot enter or accumulate in wireways, electrical components or duct work. NOTE: See Section 110-11. 424-13. Spacing from Combustible Materials. Heating equipment shall be installed to provide the required spacing between the equipment and adjacent combustible material, unless it has been found to be ac- ceptable when installed in direct contact with combustible material. 424-14. Grounding. All exposed metal parts of fixed space heating equipment liable to become energized shall be grounded as required in Article 250. C. Control and Protection of Fixed Electric Space Heating Equipment 424-19. Disconnection Means. All fixed electric space heating equip- ment shall be provided with a means for disconnection from all un- grounded conductors. Where heating equipment is supplied by more than one source, the disconnecting means shall be grouped and iden- tified. (a) For fixed heating equipment rated at not over 300 volt-amperes or '/s horsepower, the branch circuit overcurrent device may serve as the disconnecting means. (b) For fixed heating equipment of greater rating, the branch circuit switch or circuit breaker may,where readily accessible to the user of the equipment,serve as the disconnecting means. (c) Motor Driven Heating Equipment—See Part H,Article 430. (d) Unit Switches as Disconnecting Means. Unit switches with a marked"off"position, which are part of a fixed heater, that disconnect all ungrounded conductors may be used as the disconnecting means re- quired by this Article when other means for disconnection are provided in the following types of occupancies: (1) Multi-Family Dwellings. In multi-family (more than two) dwellings, the other disconnecting means shall be within the apartment, or on the same floor as the apartment in which the fixed heater is in- stalled,and may also control lamps and appliances. (2) Two-Family Dwellings. In two-family dwellings, the other dis- connecting means may be located either inside or outside of the apart- ment in which the fixed heater is installed. (3) Single-Family Dwellings. In single-family dwellings, the serv- ice disconnecting means may be the other disconnecting means. (4) Other Occupancies. In other occupancies, the branch circuit switch or circuit breaker, where readily accessible to the user of the fixed heater,may be used for the other disconnecting means. ARTICLE 424—FIXED ELECTRIC SPACE HEATING 70-205 424-20. Location of Disconnecting Means for Motor-Driven Heating Equipment. A switch or circuit breaker which serves as the disconnect- ing means for a motor-driven heater having a motor more than Vs horsepower shall be located within sight of the motor controller or shall be capable of being locked in the open position. 424-21. Controllers and Disconnecting Means. (a) Thermostats and thermostatically controlled switching devices which indicate an off position and which interrupt line current shall open all ungrounded conductors when the control device is in this off position. (b) Thermostats and thermostatically controlled switching devices which do not have an off position are not required to open all un- grounded conductors. (c) Remote control thermostats do not need to meet the requirements of paragraphs (a) and (b). These devices shall not serve as the discon- necting means. (d) Switching devices consisting of combined thermostats and manu- ally controlled switches which serve both as controllers and disconnect- ing means shall: (1) Open all ungrounded conductors when manually placed in the off position. (2) Be so designed that the circuit cannot be energized automati- cally after the device has been manually placed in the off position. 424-22. Switch and Circuit Breaker to be Indicating. Switches and cir- cuit breakers used as disconnecting means shall be of the indicating type. 424-23. Overcurrent Protection. (a) Heating equipment, other than such motor-operated equipment as required by Article 430 to have additional overcurrent protection, shall be considered as protected against overcurrent when supplied by one of the circuits of Article 210 and in accordance with the require- ments therein specified. (b) Infrared heating equipment shall have overcurrent protection not exceeding 50 amperes. (c) Space heating equipment employing resistance type heating ele- ments rated more than 48 amperes shall have the heating elements sub- divided. Each subdivided circuit shall not exceed 48 amperes and shall be protected at not more than 60 amperes. Where protection is within or on the heater enclosure, overcurrent protection shall be suitable for branch circuit protection meeting acces- sibility requirements of Section 424-65 but not meeting readily acces- sibility requirements of branch circuit protection. D. Marking of Heating Equipment 424-28. Name Plate. Each unit of heating equipment shall be pro- vided with a name plate giving the identifying name and the normal rating in volts and amperes,or in volts and watts. 70-206 NATIONAL ELECTRICAL CODE Heating equipment intended for use qn alternating current only or direct current only shall be marked to so indicate. The marking of equipment consisting of motors over 1 horsepower and other loads shall specify the rating of the motor in volts, amperes, and frequency, and the heating load in volts and watts or amperes. 424-29. Marking of Heating Elements. All heating elements which are replaceable in the field, and are a part of an electric heater shall be legibly marked with the ratings in volts and amperes, or in volts and watts. E. Cables and Panels 424-34. Heating Cable Construction. Heating cable shall be furnished complete with factory assembled nonheating leads at least 7 feet in length. 424-35. Marking of Heating Cables and Panels. Each unit shall be marked with the identifying name or identification symbol, catalog number,ratings in volts and watts or amperes. (a) Heating Cables. Each unit length of heating cable shall have a permanent legible marking on each nonheating lead located within 3 inches of the terminal end. The lead wire shall have the following color identification: 120 volt nominal, yellow; 208 volt nominal, blue; 240 volt nominal,red;and 277 volt nominal,brown. (b) Heating Panels. Permanent marking in a location that is readily visible prior to building finishing shall be provided. 424-36. Clearances of Wiring in Ceilings. (a) Wiring located above heated ceilings shall be spaced not less than 2 inches above the heated ceiling and shall be considered as operating at an ambient of 50°C. The ampacities of conductors shall be computed on the basis of the correction factors given in Note 15 to Tables 310-12 through 310-15. Exception: Wiring located above heated ceilings and over thermal insulation having a minimum thickness of 2 inches requires no correc- tion for temperature. 424-37. Clearances of Branch Circuit Wiring in Walls. (a) Where located in exterior walls,wiring shall be located outside the thermal insulation. (b) Where located in interior walls or partitions, wiring shall be con- sidered as operating at an ambient of 40°C (104°F); and the ampacities of conductors shall be computed on the basis of the correction factors given in Note 15 to Tables 310-12 through 310-15. 424-38. Area Restrictions. (a) Heating cables and panels shall not extend beyond the room or area in which they originate. (b) Cables and panels shall not be installed in closets, over walls or partitions that extend to the ceiling, or over cabinets whose clearance from the ceiling is less than the minimum horizontal dimension of the cabinet to the nearest cabinet edge that is open to the room or area. Exception: Isolated single runs of cable may pass over partitions where they are embedded. ARTICLE 424—FIXED ELECTRIC SPACE HEATING 70-207 (c) This provision shall not prevent the use of cable or panels in closet ceilings as low temperature heat sources to control relative humid- ity, provided they are used only in those portions of the ceiling which are unobstructed to the floor by shelves,or other permanent fixtures. 424-39. Clearance from Other Objects and Openings. Panel and cables shall be separated at least 8 inches from the edge of outlet boxes and junction boxes that are to be used for mounting surface lighting fixtures. Two inches shall be provided from recessed fixtures and their trims,ven- tilating openings and other such openings in room surfaces. Sufficient area shall be provided to assure that no heating cable or panel will be covered by other surface mounted lighting units. 424-40. Splices. Embedded cables may be spliced only where neces- sary and only by approved means, and in no case shall the length of the heating cable be altered. 424-41. Installation of Heating Cables on Dry Board, in Plaster and on Concrete Ceilings. (a) Cables shall not be installed in walls. Exception:Isolated single runs of cable may run down a vertical sur- face to reach a dropped ceiling. (b) Adjacent runs of cable not exceeding 23/4 watts per foot shall be installed not less than 11/2 inches on centers. (c) Heating cables may be applied only to gypsum board, plaster lath or other fire-resistant material. With metal lath or other electrical con- ducting surface, a coat of plaster shall be applied to completely separate the metal lath or conducting surface from the cable. (See also Section 424-41(f).) (d) All the heating cables, the splice between the heating cable and nonheating leads, and 3 inch minimum of the nonheating lead at the splice shall be embedded in plaster or dry board in the same manner as the heating cable. (e) The entire ceiling surface shall have a finish of thermally non- insulating sand plaster having a nominal thickness of 1/2 inch, or other specially approved non-insulating material applied according to spec- ified thickness and directions. (f) Cables shall be secured at intervals not exceeding 16 inches by means of approved stapling, tape, plaster, nonmetallic spreaders or other approved means. Staples or metal fasteners which straddle the cable shall not be used with metal lath or other electrical conducting surface. (g) In dry board installations, the entire ceiling below the heating cable shall be covered with gypsum board not exceeding 1/2 inch thick- ness.The void between the upper layer of gypsum board,plaster lath or other fire resistant material and the surface layer of gypsum board shall be completely filled with thermally conducting non-shrinking plaster or other approved material of equivalent thermal conductivity. (h) Cables shall be kept free from contact with metal or other elec- trical conducting surfaces. 70-208 NATIONAL ELECTRICAL CODE (i) In dry board applications, cable shall be installed parallel to the joist,leaving a clear space centered under the joist of 21 inches (width) between centers of adjacent runs of cable. Crossing of joist by cable shall be kept to a minimum and should be at the ends of the room. Sur- face layer of gypsum board shall be mounted so that the nails or other fastenings do not pierce the heating cable. 424-42. Finished Ceilings. Finished ceilings may be covered with paint,wallpaper or other approved surface finishes. 424-43. Installation of Nonheating Leads of Cables and Panels. (a) Nonheating leads of cables and panels shall be installed in ac- cordance with approved wiring methods from the junction box to a location within the ceiling. Such installations may be single conductors in approved raceways, single or multi-conductor Type UF, Type NMC, Type MI,or other approved conductors. (b) Not less than 6 inches of nonheating leads shall be free within the junction box. The marking of the leads shall be visible in the junction box. (c) Excess leads shall not be cut but shall be secured to the underside of the ceiling and embedded in plaster or other approved material, leaving only a length sufficient to reach the junction box with not less than 6 inches of free lead within the box. 424-44. Installation of Panels or Cables in Concrete or Poured Masonry Floors. (a) Panels or heating units shall not exceed 33 watts per square foot of heated area or 161/2 watts per linear foot of cable. (b) The spacing between adjacent runs of cable shall not be less than 1 inch on centers. (c) Cables shall be secured in place by nonmetallic frames or spread- ers or other approved means while the concrete or other finish is ap- plied. Cables, units, and panels shall not be installed where they bridge ex- pansion joints unless protected from expansion and contraction. (d) Spacings shall be maintained between the heating cable and metal embedded in the floor. Exception: Grounded metal-clad cable may be in contact with metal embedded in the floor. (e) Leads shall be protected where they leave the floor by rigid metal conduit,electrical metallic tubing,or by other approved means. (f) Bushings or approved fittings shall be used where the leads emerge within the floor slab. 424-45. Tests During and After Installation. (a) Embedded cable installations shall be made with due care to pre- vent damage to the cable assembly and shall be inspected and approved before cables are covered or concealed. (b) Cables should be tested for insulation resistance after plastering the ceiling or the pouring of floors. ARTICLE 424—FIXED ELECTRIC SPACE HEATING 70-209 • 424-46. Panels—General. Sections 424-46 to 48 cover only heating panels of less than 25 watts per square foot assembled together in the field to form a heating installation in one room or area using approved methods of interconnection. Such an installation shall be connected by a recognized wiring method. 424-47. Panels to be Complete Units. Panels shall be installed as com- plete units unless approved for field cutting in a recognized manner. 424-48. Installation. Panels shall be installed in an approved manner. Nails, staples, or other electrically conducting fasteners shall not be used where they penetrate current-carrying parts. Exception: Insulated fasteners may be used with systems for which they are recognized. F. Duct Heaters 424-57. General. The provisions in Part F shall apply to any heater mounted in the air stream of a forced air system where the air moving unit is not provided as an integral part of the equipment. 424-58. Approval. Heaters installed in an air duct shall be approved for the purpose and installed in the approved manner. 424-59. Air Flow. Means shall be provided to assure uniform and adequate air flow over the face of the heater. Heaters installed near (within 4 feet) a fan outlet, elbows, baffle plates or other obstruction in duct work may require turning vanes, pressure plates or other devices on the inlet side of the duct heater to assure an even distribu- tion of air over the face of the heater. 424-60. Elevated Inlet Temperature. Duct heaters intended for use with elevated inlet air temperature (such as heat pumps) shall be ap- proved for the purpose and so marked. 424-61. Installation of Duct Heaters with Heat Pumps and Air Condition- ers. Heat pumps and air conditioners having duct heaters closer than 4 feet to the heat pump or air conditioner shall be approved for such installation and so marked. 424-62. Condensation. Duct heaters used with air conditioners or other air cooling equipment which may result in condensation of mois- ture shall be approved for use with air conditioners. 424-63. Fan Circuit Interlock. Means should be provided to insure that the fan circuit is energized when the first heater circuit is energized. 424-64. Limit Controls. Each duct heater shall be provided with an in- tegral approved automatic reset temperature limiting control or con- trollers to de-energize the circuit or circuits. In addition, an integral independent supplementary control or con- trollers shall be provided in each duct heater which will disconnect a sufficient number of conductors to interrupt current flow. This device shall be manually resettable or replaceable. 424-65. Location of Disconnecting Means. Duct heater controller equipment shall be accessible with the disconnecting means installed at or within sight of the controller. 424-66. Installation. See NFPA Pamphlets Nos.90A and 90B. 70-210 NATIONAL ELECTRICAL CODE G. Special Provisions for Fixed Outdoor Electric De-Icing and Snow Melting Installations 424-71. General. (a) The provisions of Part G shall apply to electrically energized heating units, panels and cables, embedded in poured masonry or as- phalt driveways,walks,steps,and other areas. (b) In addition to complying with the general requirements for fixed heating equipment,such equipment shall comply with Part G. (c) Equipment for use with electric de-icing and snow melting sys- tems shall be of a type approved for such service. (d) Electrical heating systems employing methods of construction or installation other than covered by Part G may be used only by special permission. 424-72. Use. (a) De-icing and snow melting equipment shall be installed only in the specific materials for which they are approved. (b) De-icing and snow melting units shall not be used where exposed to severe physical damage,unless adequately protected. 424-73. Complete Units. (a) Units,panels, and cables shall be installed in their complete sizes or lengths as supplied by the manufacturer. Exception:By special permission of the authority having jurisdiction. (b) Units which are shortened, or from which the marking name plates are missing shall not be installed except that the non-heating lead may be shortened if the marking specified in Section 424-77 is retained. (c) Units shall be suitable for use with approved wiring systems. 424-74. Non-Heating Leads. Non-heating leads on the cables, panels, or units shall be furnished as part of the factory assembly. The leads shall consist of conductors and wiring approved for general use,or other wiring approved for the purpose. 424-75. Installation of Heating Cables, Units,or Panels. (a) The operating characteristics of embedded assemblies of heating equipment depend upon the specific materials involved and therefore embedded equipment should be installed as designed for use in such materials. (b) Panels or heating units shall not exceed 120 watts per square foot of heated area. (c) The spacing between adjacent cable runs is dependent upon the rating of the cable,and shall be not less than 1 inch on centers. (d) Units,panels,and cables shall be installed either: (1) On a substantial asphalt or masonry base at least 2 inches thick and have at least 1 i/2 inches of asphalt or masonry applied over the units,panels,or cables,or (2) They may be installed over other approved bases and embedded within 31/2 inches of masonry or asphalt but not less than one inch from the top surface. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-211 (e) Cables shall be secured in place by frames or spreaders, or other approved means,while the masonry or asphalt finish is applied. (f) Cables, units, and panels shall not be installed where they bridge expansion joints unless adequately protected from expansion and con- traction. 424-76. Installation of Non-Heating Leads. (a) Non-heating leads having a grounding sheath or braid may be embedded in masonry or asphalt similar to the heating cable without additional protection. (b) All but 1 to 6 inches of non-heating leads of Type TW and other approved types not having a grounding sheath shall be enclosed in con- duit, electrical metallic tubing or other raceways, within the asphalt or masonry and the distance from the factory splice to the raceway shall be not less than one inch nor more than 6 inches. (c) Insulating bushings shall be used in the asphalt or masonry where leads enter conduit,tubing,or raceway. (d) Leads shall be protected in expansion joints and where they emerge from masonry or asphalt by conduit, electrical metallic tubing or other raceways. (e) Not less than 6 inches of non-heating leads shall be within the junction box. 424-77. Marking. Each heating unit, panel, and cable shall be legibly marked within 3 inches of each end of the non-heating lead with the identification symbol, catalog number, and rating in volts and watts or amperes. 424-78. Junction Boxes. All splices other than factory splices shall be made in properly installed boxes approved for the location. 424-79. Grounding. (a) Grounding means such as copper braid, lead or copper sheath, or other approved means shall be provided as part of the heating section of the approved cable,panel,or unit. (b) All noncurrent-carrying parts which are liable to become ener- gized shall be bonded together and positively connected to a continuous (unbroken) No. 14 AWG or larger covered copper wire sized in ac- cordance with Table 250-95 extending to the distribution panelboard. Where the bonding conductor is subject to physical damage it shall be at least No. 10 AWG copper. 424-80. Tests. Embedded heating installation shall be inspected and approved before being covered. ARTICLE 430—MOTORS, MOTOR CIRCUITS AND CONTROLLERS A. General 430-1.(a). Motor Feeder and Branch Circuits. (See Diagram 430-1(a). (b) General. The following general requirements cover provisions for motors, motor circuits, and controllers which do not properly fall into the other parts of this Article. 70-212 NATIONAL ELECTRICAL CODE Diagram 430-1(a) Genera/• Par/A Requirements for over 600vo/ts- • • • • • Part J Protection of /iveparts a//voltages- • • •Part K Grounding - - • • • R3rt L Tab/es • - - Part M Motor Feeder To `uvo/y Part 8 Sec.430-23and430 24 430-25and430-26 Motor Feeder ri❑ Part E Overcurrent protection Part E Motor Disconnecting ° Means Part H Motor Branch Circuit Overcurrent protection Part Motor Circuit Conduct Part1 Motor Controller Part G Motor Contra/Circuits ct Part F Motor Running Overcurrentprotecfion n Part C Motor - Part A Inherent Protection ( (vl .' Part C Secondary Contra//er Part 8 Secondary Conductors ❑ Sec.430-23 Secondary Resistor ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-213 430-3. Part Winding Motors. A part-winding-start induction or syn- chronous motor is one arranged for starting by first energizing part of its primary (armature) winding and, subsequently, energizing the re- mainder of this winding in one or more steps. The purpose is to reduce the initial values of the starting current drawn or the starting torque developed by the motor. A standard part-winding-start induction mo- tor is arranged so that one-half of its primary winding can be energized initially and, subsequently, the remaining half can be energized, both halves then carrying the same current. A sealed "hermetic type" re- frigeration compressor motor is not to be considered a standard part- winding-start induction motor. When separate overcurrent devices are used with a standard part- winding-start induction motor, each half of the motor winding shall be individually protected in accordance with Sections 430-32 and 430-37, except that the trip current shall be one-half that specified. Each motor winding connection shall have short circuit and ground fault protection rated at not more than one-half that specified by Sec- tion 430-52 except that a single device having this half rating may be used for both windings if this will allow the motor to start. 430-4. In Sight From. Where in this Article it is specified that some equipment shall be "in sight from" another equipment, it means that the equipment must be visible and not more than 50 feet distant. 430-5. Other Articles. Motors and controllers shall also comply with the applicable provisions of the following: Capacitors Section 460-9 Cranes and Hoists Article 610 Elevators, Dumbwaiters, Escalators, and Moving Walks Article 620 Garages, Aircraft Hangars, Gasoline Dispensing and Service Stations,Bulk Storage Plants,Finishing Processes and Flammable Anesthetics....Articles 511, 513, 514, 515, 516, and 517 Hazardous Locations Articles 500-503 Metalworking Machine Tools Article 670 Motion-picture Projectors Sections 540-12, 540-17 Motion-picture Studios Article 530 Organs Section 650-3 Resistors and Reactors Article 470 Theaters Section 520-48 430-6. Ampacity Determination. Ampacities shall be determined as follows: (a) General Motor Applications. Except as noted in Sections 430-6 (b), and 430-6(c) whenever the current rating of a motor is used to determine the ampacity of conductors, switches, branch-circuit over- current devices, etc., the values given in Tables 430-147, 430-148, 430- 149, and 430-150, including notes, shall be used instead of actual cur- rent rating marked on the motor nameplate. Separate motor running overcurrent protection shall be based on the motor nameplate current rating. When a motor is marked in amperes, but not horsepower, the horsepower rating shall be assumed to be that corresponding to the value given in Tables 430-147, 430-148, 430-149, and 430-150 inter- polated if necessary. Exception: For multispeed motors, see Sections 430-22(a) and 430- 52. 70-214 NATIONAL ELECTRICAL CODE (b) Sealed (Hermetic Type) Motor-Compressors. For sealed (her- metic-type) motor compressors, the full-load current marked on the nameplate of the equipment in which the compressor is employed shall be used to determine the ampacity of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit overcurrent protection, and the motor-running protection. Where no full-load cur- rent rating is shown on the equipment nameplate, the full-load current shown on the compressor nameplate shall be used. For disconnecting means and controllers,see also Sections 430-83 and 430-110. (c) Torque Motors. For torque motors the rated current shall be locked-rotor current and this nameplate current shall be used to deter- mine the ampacity of the branch-circuit conductors (see Sections 430-22 and 430-24) and motor operating overcurrent protection. For motor controllers and disconnecting means, see Section 430-83, Exception 4 and Section 430-110. 430-7. Marking on Motors and Multimotor Equipment. (a) Usual Motor Applications. A motor shall be marked with the following information: (1) Maker's name. (2) Rated volts and full-load amperes. (3) Rated full-load speed. (4) Rated temperature rise or the insulation system class and rated ambient temperature. (5) Time rating. (6) Rated horsepower if 1/2 horsepower or more. (7) Code letter if an alternating-current motor rated 1/2 horsepower or more (see Section 430-7(b). (8) Secondary volts and full-load amperes if a wound-rotor induc- tion motor. A multispeed motor, except a shaded-pole or permanent-split capaci- tor motor, shall be marked with the amperes and horsepower at each speed. A motor provided with a thermal protector complying with Sec- tion 430-32 (a-2) or 430-32(c-2) shall be marked "Thermally Pro- tected." A motor complying with Section 430-32(c-4) shall be marked "Impedance Protected." The time rating shall be 5, 15, 30, or 60 minutes,or continuous. Exception No. 1. On motors of arc welders, the horsepower rating may be omitted. Exception No. 2. On polyphase wound-rotor motors the code letter shall be omitted. (b) Locked Rotor Indicating Code Letters: Code letters marked on motor nameplates to show motor input with locked rotor shall be in accordance with Table 430-7(b). The code letter indicating motor input with locked rotor must be in an individual block on the nameplate, properly designated. This code letter is to be used for determining branch-circuit overcurrent protec- tion by reference to Table 430-152, as provided in Section 430-52. ARTICLE 430-MOTOR CIRCUITS AND CONTROLLERS 70-215 Table 430-7(b). Locked Rotor Indicating Code Letters Kilovolt-Amperes Code per Horsepower Letter with Locked Rotor A 0 - 3.14 B 3.15 - 3.54 C 3.55 - 3.99 D 4.0 - 4.49 E 4.5 - 4.99 F 5.0 - 5.59 G 5.6 - 6.29 H 6.3 - 7.09 J 7.1 - 7.99 K 8.0 - 8.99 L 9.0 - 9.99 M 10.0 - 11.19 N 11.2 - 12.49 P 12.5 - 13.99 R 14.0 - 15.99 S 16.0 - 17.99 T 18.0 - 19.99 U 20.0 - 22.39 ✓ 22.4 - and up The above table is an adopted standard of the National Electrical Manu- facturers Association. (1) Multi-speed motors shall be marked with the code letter desig- nating the locked-rotor KVA per horsepower for the highest speed at which the motor can be started, except constant horsepower motors which shall be marked with the code letter giving the highest locked- rotor KVA per horsepower. (2) Single-speed motors starting on Y connection and running on delta connections shall be marked with a code letter corresponding to the locked-rotor KVA per horsepower for the Y connection. (3) Dual-voltage motors which have a different locked-rotor KVA per horsepower on the two voltages shall be marked with the code let- ter for the voltage giving the highest locked-rotor KVA per horse- power. (4) Motors with 60- and 50-cycle ratings shall be marked with a code letter designating the locked rotor KVA per horsepower on 60 cycles. (5) Part-winding-start motors shall be marked with a code letter designating the locked-rotor KVA per horsepower that is based upon the locked-rotor current for the full winding of the motor. (c) Sealed (Hermetic-Type) Motor-Compressors. A sealed (hermetic- type) motor-compressor shall be marked with the following informa- tion: 70-216 NATIONAL ELECTRICAL CODE (1) The manufacturer's name,trademark,or symbol. (2) The voltage,phase,and frequency. (3) The full-load current. (4) The locked-rotor current if a polyphase motor or if a single phase motor having a full-load current more than 4.5 amperes at 230 volts or 9 amperes at 115 volts. (5) The words "Thermally Protected" if a thermal protector inte- gral with the motor-compressor is provided. Exception: The full-load current may be marked on the nameplate of the equipment in which the compressor is used, provided such marking for multi-compressor equipment indicates the specific motor-compres- sor with which the marking is associated. (d) Torque Motors. Torque motors are rated for operation at stand- still and shall be marked in accordance with paragraph (a) except that locked rotor torque shall replace horsepower. (e) Multimotor and Combination Load Equipment. Multimotor and combination load equipment shall be provided with a visible nameplate marked with the maker's name, the rating in volts, frequency and num- ber of phases, minimum circuit ampacity, and the maximum rating of the circuit protective device. The ampacity shall be calculated by using Section 430-25 and counting all of the motors and other loads which will be operated at the same time. The protective device rating shall not exceed the value calculated by using Section 430-53(c) (3). Multimotor equipment for use on two or more circuits shall be marked with the above information for each circuit. When the equipment is not factory wired and the individual name- plates of motors and other loads are visible after assembly of the equip- ment,these nameplates may serve as the required marking. 430-8. Marking on Controllers. A controller shall be marked with the maker's name or identification, the voltage, the current or horsepower rating, and such other data as may be needed to properly indicate the motors for which it is suitable. A controller which includes motor run- ning overcurrent protection, when suitable for group motor application shall be marked with the motor running overcurrent protection and the maximum branch circuit overcurrent protection for such applications. Combination controllers employing adjustable instantaneous circuit breakers (without time delay) shall be clearly marked to indicate the ampere settings of the adjustable trip element. Where a controller is built in as an integral part of a motor or of a motor- generator set,the controller need not be individually marked when the neces- sary data is on the motor nameplate. For controllers which are an integral part of equipment approved as a unit, the above marking may be on the equipment nameplate. 430-9. Marking at Terminals. Terminals of motors and controllers shall be suitably marked or colored where necessary to indicate the proper connections. 430-10. Wiring Space in Enclosures. Enclosures for controllers and disconnecting means for motors shall not be used as junction boxes, ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-217 auxiliary gutters, or raceways for conductors feeding through or tap- ping off to the other apparatus unless designs are employed which pro- vide adequate space for this purpose. 430-11. Protection Against Liquids. Suitable guards or enclosures shall be provided to protect exposed current-carrying parts of motors and the insulation of motor leads where installed directly under equip- ment, or in other locations where dripping or spraying oil, water, or other injurious liquid may occur, unless the motor is designed for the existing conditions. 430-12. Motor Terminal Housings. (a) When motors are provided with terminal housings, the housings shall be of metal and of substantial construction. Exception:In other than hazardous locations, substantial non-metal- lic, non-burning housings may be used on motors larger than 34 inches in diameter provided internal grounding means between the machine frame and the conduit connection is incorporated within the housing. See USA Standard Method of Test for Flammability of Rigid Plastics over 0.127CM (0.050 inch) in thickness,K65.21-1965 for non-burning test. (b) When these terminal housings enclose wire-to-wire connections, they shall have minimum dimensions and usable volumes in accordance with the following: Table 430-12(b). Terminal Housing—Wire to Wire Connections Cover Opening, Usable Minimum Volume, Dimension, Minimum, Hp Inches Cubic Inches 1 and smaller* 1% 71/2 11 ,2and3t 13/4 12 5 and 71 2 16 10 and 15 21/a 221 20 and 25 2%s 33 30 and 40 3 44 50 and 60 31/2 721/2 75 and 100 31/2 100 125 and 150 6 216 *For motors rated 1 horsepower and smaller and with the terminal housing partially or wholly integral with the frame or end shield, the volume of the terminal housing shall be not less than 0.8 cubic inch per wire-to-wire connection. The minimum cover opening dimension is not specified. tFor motors rated 11/, 2 and 3 horsepower and with the terminal housing partially or wholly integral with the frame or end shield, the volume of the terminal housing shall be not less than 1.0 cubic inch per wire-to-wire connection. The minimum cover opening dimension is not specified. 70-218 NATIONAL ELECTRICAL CODE (c) When these terminal housings enclose rigidly mounted motor ter- minals, the terminal housing shall be of sufficient size to provide mini- mum terminal spacings and usable volumes in accordance with the fol- lowing: Table 430-12(c)(1). Terminal Spacings—Fixed Terminals Minimum Spacing,Inches Between Line Between Terminals and Other Line Uninsulated Metal Volts Terminals Parts 250 or less IA '/a 251 to 600,Incl. 3/8 3/8 Table 430-12(c)(2). Usable Volumes—Fixed Terminals Power Supply Minimum Usable Volume per Conductor Power Supply Conductor, Size,Awg Cubic Inches 14 1.0 12 and 10 11/4 8and6 21A (d) For larger wire sizes or when motors are installed as a part of factory-wired equipment, without additional connection being required at the motor terminal housing during equipment installation, the ter- minal housing shall be of ample size to make connections, but the fore- going provisions for the volumes of terminal housings need not apply. 430-13. Bushing. Where wires pass through an opening in an en- closure, conduit box or barrier, a bushing shall be used to protect the conductors from the edges of the openings having sharp edges. The bushing shall have smooth, well-rounded surfaces where it may be in contact with the conductors. If used where there may be a presence of oils, greases, or other contaminants, the bushing shall be made of ma- terial not deleteriously affected. For conductors,see Section 310-7. 430-14. Location of Motors. (a) Ventilation and Maintenance. Motors shall be located so that adequate ventilation is provided and so that maintenance such as lubri- cation of bearings and replacing of brushes can be readily accom- plished. (b) Open Motors. Open motors having commutators or collector rings shall be located or protected so that sparks cannot reach adjacent combustible material. This does not prohibit the installation of these motors on wooden floors or supports. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-219 430-16. Overheating from Dust Accumulations. In locations where dust or flying material will collect on or in motors in such quantities as to seriously interfere with the ventilation or cooling of motors, and thereby caused dangerous temperatures, suitable types of enclosed motors which will not overheat under the prevailing conditions, shall be used. Especially severe conditions may require the use of enclosed pipe ventilated motors, or enclosure in separate dust-tight rooms, properly ventilated from a source of clean air. 430-17. Highest Rated (Largest) Motor. In determining compliance with Sections 430-24, 430-53(b), 430-53(c), and 430-62(a), the high- est rated (largest) motor shall be considered to be that motor which has the highest rated full-load current. For other than sealed (hermetic- type) motor-compressors, the full-load current used to determine the highest rated motor shall be the equivalent value corresponding to the motor horsepower rating selected from Tables 430-147, 430-148, 430- 149,and 430-150. B. Motor Circuit Conductors 430-21. General. The provisions of Part B specify sizes of conductors capable of carrying the motor current without overheating under the conditions specified. Table 430-22 (a-Exception). Duty Cycle Service Percentages of Nameplate Current Rating 5- 15- 30&60 Con- Classification of Service Minute Minute Minute tinuous Rated Rated Rated Rated Motor Motor Motor Motor Short-Time Duty Operating valves,raising or lowering rolls,etc. 110 120 150 Intermittent Duty Freight and passenger elevators,tool heads, pumps, drawbridges, turn- tables, single-operator arc welders for manual welding, etc. 85 85 90* 140 Periodic Duty Rolls, ore and coal-handling ma- chines, etc. 85 90 95 140 Varying Duty 110 120 150 200 *This figure also applies for conductors which supply a motor-generator single-operator arc welder which has a 60 per cent duty cycle rating. Any motor application is considered to be for continuous duty unless the nature of the apparatus which it drives is such that the motor will not operate continuously with load under any condition of use. For long runs, it may be necessary in order to avoid excessive voltage drop,to use conductors of sizes larger than the minimum sizes selected from Tables 310-12 to 310-15 inclusive. See Example No. 8,Ch. 9, and Diagram in Section 430-1. 70-220 NATIONAL ELECTRICAL CODE (a) The provisions of Articles 250, 300, and 310 are not intended to apply to conductors which form an integral part of approved equipment, or to integral conductors of motors, motor controllers, and the like. See Sections 300-1(d) and 310-1(c). 430-22. Single Motor. (a) Branch-circuit conductors supplying a single motor shall have an ampacity not less than 125 per cent of the motor full-load current rating. In case of a multispeed motor, the selection of branch circuit con- ductors on the line side of the controller shall be based on the high- est of the full load current ratings shown on the motor name plate; selection of branch circuit conductors between the controller and the motor, which are energized for that particular speed, shall be based on the current rating for that speed. Exception:Conductors for a motor used for short-time, intermittent, periodic, or varying duty shall have an ampacity not less than the per- centage of the motor nameplate current rating as shown in Table 430- 22 (a-Exception) unless the authority having jurisdiction grants special permission for conductors of smaller size. (b) The conductors between a stationary motor rated one horse- power or less, and the separate terminal enclosures permitted in Section 430-145(b) may be smaller than No. 14 but not smaller than No. 18, provided they have an ampacity as specified above. 430-23. Wound-Rotor Secondary. (a) For continuous duty the conductors connecting the secondary of a wound-rotor alternating-current motor to its controller shall have an ampacity which is not less than 125 per cent of the full-load second- ary current of the motor. (b) For other than continuous duty, these conductors shall have an ampacity, in per cent of full load secondary current, not less than that specified in Table 430-22 (a-Exception). (c) Where the secondary resistor is separate from the controller, the ampacity of the conductors between controller and resistor shall be not less than that given in Table 430-23 (c). Table 430-23(c). Secondary Conductor Ampacity of Wire in Resistor Duty Classification Per Cent of Full-Load Secondary Current Light starting duty 35 Heavy starting duty 45 Extra heavy starting duty 55 Light intermittent duty 65 Medium intermittent duty 75 Heavy intermittent duty 85 Continuous duty 110 ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-221 430-24. Conductors Supplying Several Motors. Conductors supplying two or more motors shall have an ampacity equal to the sum of the full load current rating of all the motors plus 25 per cent of the highest rated motor in the group. Where one or more motors of the group are used on short time in- termittent, periodic, or varying duty, the ampacity of the conductors shall be calculated as follows: (a) Determine the needed ampacity for each motor used for other than continuous duty from Table 430-22(a-Exception). (b) Determine the needed ampacity for each continuous duty motor based on 100 per cent motor full load current rating. (c) Multiply the largest single motor ampacity determined from (a) or (b) by 1.25. Add all other motor ampacities from (a) and (b) and select the conductor for this total ampacity. Exception: When the circuitry is so interlocked as to prevent the start- ing and running of a second motor or group of motors, the conductor size shall be determined from the larger motor or group of motors that is to be operated at a given time. See Example No.8,Chapter 9. 430-25. Supply Conductors. (a) Combination Load. Conductors supplying a motor load, and in addition a lighting or appliance load as computed from Article 220 and other applicable Sections, shall have an ampacity sufficient for the light- ing or appliance load plus the required capacity for the motor load de- termined in accordance with Section 430-24, or, for a single motor, in accordance with Section 430-22. (b) Multimotor and Combination Load Equipment. The ampacity of the conductors supplying multimotor and combination load equipment shall not be less than the minimum circuit ampacity marked on the equipment in accordance with Section 430-7(e). 430-26. Feeder Demand-Factor. Where a reduced heating of the con- ductors results from motors operating on duty-cycle, intermittently, or from all motors not operating at one time the authority having jurisdic- tion may grant permission for feeder conductors to be of a capacity less than specified in the Sections 430-24 and 430-25, provided the con- ductor is of sufficient ampacity for the maximum load determined by the sizes and number of motors supplied and the character of their loads and duties. 430-27. Capacitors with Motors: For provisions covering conductors where capacitors are installed on motor circuits, see Sections 460-7, 460-8,460-9. C. Motor and Branch Circuit Running Overcurrent(Overload)Protection 430-31. General. The provisions of Part C specify overcurrent de- vices intended to protect the motors, the motor-control apparatus, and the branch-circuit conductors against excessive heating due to motor overloads or failure to start. 70-222 NATIONAL ELECTRICAL CODE (a) Overload in electrical apparatus is an operating overcurrent which, when it persists for a sufficient length of time, would cause damage or dangerous overheating of the apparatus. It does not include short circuits or ground faults. (b) These provisions shall not be interpreted as requiring overcurrent protection where it might introduce additional or increased hazards as in the case of fire pumps [see NFPA Standard for Centrifugal Fire Pumps (No.20)]. 430-32. Continuous Duty Motors. (a) More Than One Horsepower. Each continuous duty motor rated more than one horsepower shall be protected against running over- current by one of the following means: (1) A separate overcurrent device which is responsive to motor cur- rent. This device shall be rated or selected to trip at no more than the following per cent of the motor full-load current rating: Motors with a marked service factor not less than 1.15 125% Motors with a marked temperature rise not over 40°C 125% Sealed (hermetic-type) motor compressors overload relays 140% other devices 125% All other motors 115% For a multispeed motor, each winding connection shall be con- sidered separately. This value may be modified as permitted by Section 430-34. When a separate motor running-overcurrent device is so con- nected that it does not carry the total current designated on the motor nameplate, such as for wye-delta starting, the proper percentage of nameplate current applying to the selection or setting of the overcurrent device shall be clearly designated on the equipment or the manufac- turer's selection table shall take this into account. (2) A thermal protector integral with the motor, approved for use with the motor which it protects on the basis that it will prevent dan- gerous overheating of the motor due to overload or failure to start. If the motor current interrupting device is separate from the motor and its control circuit is operated by a protective device integral with the motor, it shall be so arranged that the opening of the control circuit will result in interruption of current to the motor. (3) For motors larger than 1500 horsepower, a protective device employing embedded temperature detectors which cause current to the motor to be interruped when the motor attains a temperature rise greater than marked on the nameplate in an ambient of 40°C. Standards for the application of embedded temperature detectors are given in the USA Standards for Rotating Electrical Machinery,USAS C50.2- 1955 and C50.4-1965. I (b) One Horsepower or Less,Manually Started. (1) Each continuous duty motor rated at one horsepower or less which is not permanently installed, is manually started and is within sight from the controller location, shall be considered as protected ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-223 against overcurrent by the overcurrent device protecting the conductors of the branch circuit.This branch circuit overcurrent device shall not be larger than that specified in Part D, of Article 430, except that any such motor may be used at 125 volts or less on a branch circuit protected at 20 amperes. (2) Any such motor which is not in sight from the controller loca- tion shall be protected as specified in Section 430-32(c). Any motor rated at one horsepower or less which is permanently installed, shall be protected in accordance with Section 430-32(c). (c) One Horsepower or Less, Automatically Started. Any motor of one horsepower or less which is started automatically shall be protected against overcurrent by the use of one of the following means: (1) A separate overcurrent device which is responsive to motor current. This device shall be rated or selected to trip at no more than the following per cent of the motor full-load current rating: Motors with a marked service factor not less than 1.15 125% Motors with a marked temperature rise not over 40°C 125% Sealed (hermetic-type) motor compressors overload relays 140% other devices 125% All other motors 115% For a multispeed motor, each winding connection shall be con- sidered separately. This value may be modified as permitted by Section 430-34. (2) A thermal protector integral with the motor, approved for use with the motor which it protects on the basis that it will prevent dan- gerous overheating of the motor due to overload or failure to start. Where the motor current interrupting device is separate from the mo- tor and its control circuit is operated by a protective device integral with the motor, it shall be so arranged that the opening of the control circuit will result in interruption of current to the motor. (3) The motor shall be considered as being properly protected where it is part of an approved assembly which does not normally subject the motor to overloads and which is also equipped with other safety controls (such as the safety combustion controls of a domestic oil burner) which protect the motor against damage due to stalled rotor current. Where such protective equipment is used it shall be indicated on the nameplate of the assembly where it will be visible after installa- tion. (4) In case the impedance of the motor windings is sufficient to prevent overheating due to failure to start, the motor may be protected as specified in Section 430-32(b) (1) for manually started motors. Many alternating-current motors of less than 1/20 horsepower, such as clock motors, series motors, etc., and also some larger motors such as torque motors, come within this classification. It does not in- clude split-phase motors having automatic switches to disconnect the starting windings. (d) Wound-Rotor Secondaries. The secondary circuits of wound- rotor alternating-current motors, including conductors, controllers, 70-224 NATIONAL ELECTRICAL CODE resistors, etc., shall be considered as protected against overcurrent by the motor-running overcurrent device. 430-33. Intermittent and Similar Duty. A motor used for a condition of service which is inherently short time, intermittent, periodic, or varying duty, as illustrated by Table 430-22 (a-Exception), shall be considered as protected against overcurrent by the branch-circuit over- current device, provided the overcurrent protection does not exceed that specified in Tables 430-152 and 430-153. Any motor application shall be considered to be for continuous duty unless the nature of the apparatus which it drives shall be such that the motor cannot operate continuously with load under any condition of use. 430-34. Selection or Setting of Protective Device. Where the values specified for motor-running overcurrent protection in Sections 430-32 (a-1) and 430-32 (c-1) do not correspond to the standard sizes or ratings of fuses, non-adjustable circuit breakers, thermal cutouts, ther- mal relays, the heating elements of thermal trip motor switches, or the possible settings of adjustable circuit breakers adequate to carry the load, the next higher size, rating, or setting may be used, but not higher than the following per cent of motor full-load current rating: Motors with a marked service factor not less than 1.15 140% Motors with a marked temperature rise not over 40°C 140% Sealed (hermetic-type) compressor motors 140% All other motors 130% In case it is not shunted during the starting period of the motor (see Section 430-35), the protective device shall have sufficient time delay to permit the motor to start and accelerate its load. 430-35. Shunting During Starting Period. (a) In the case of a motor that is manually started (including start- ing with a magnetic starter having push-button control), the running overcurrent protection may be shunted or cut out of circuit during the starting period of the motor, provided the device by which the over- current protection is shunted or cut out cannot be left in the starting position, and fuses or time-delay circuit breakers rated or set at not over 400 per cent of the full-load current of the motor, are so located in the circuit as to be operative during the starting period of the motor. (b) The motor-running overcurrent protection shall not be shunted or cut out during the starting period if the motor is automatically started. 430-36. Fuses—In Which Conductor. Where fuses are used for motor- running protection, a fuse shall be inserted in each ungrounded con- ductor. Exception: A fuse shall also be inserted in a grounded conductor under the circumstances set forth in the note following Table 430-37. 430-37. Devices Other Than Fuses—In Which Conductor. Where de- vices other than fuses are used for motor-running overload protection, Table 430-37 shall govern the minimum allowable number and loca- tion of overcurrent units such as trip coils,relays,or thermal cutouts. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-225 Table 430-37—Running Overcurrent Units Number and location of overcurrent units,such Kind of Motor Supply System as trip coils,relays or thermal cutouts 1-phase A.C. 2-wire, 1-phase A.C.or 1 in either conductor or D.C. D.C.ungrounded 1-phase A.C. 2-wire, 1-phase A.C.or tin ungrounded conduc- or D.C. D.C.,one conductor tor grounded I-phase A.C. 3-wire, 1-phase A.C.or 1 in either ungrounded or D..C. D.C.,grounded-neutral conductor 2-phase A.C. 3-wire,2-phase A.C., 2,one in each phase ungrounded 2-phase A.C. 3-wire,2-phase A.C.,one 2 in ungrounded conduc- conductor grounded tors 2-phase A.C. 4-wire,2-phase A.C. 2,one per phase in un- grounded or ungrounded grounded conductors 2-phase A.C. 5-wire,2-phase, A.C. 2,one per phase in any grounded neutral or ungrounded phase wire ungrounded 3-phase A.C. 3-wire, 3-phase A.C., *2 in any 2 conductors ungrounded 3-phase A.C. 3-wire,3-phase A.C.,one *2 in ungrounded conduc- conductor grounded tors 3-phase A.C. 3-wire,3-phase A.C. *2 in any 2 conductors grounded-neutral 3-phase A.C. 4-wire,3-phase A.C. *2 in any 2 conductors grounded-neutral or except the neutral ungrounded *Note: Three running overcurrent units shall be used where three- phase motors are installed in isolated, inaccessible, or unattended loca- tions,unless the motor is protected by other approved means. UNATTENDED (Definition): Lacking the presence of a person (not necessarily an electrician) capable of exercising responsible control of the motor under consideration. Such a person need not be in sight of the motor at all times but must be available for opening the motor cir- cuit in the event of motor overheating. 70-226 NATIONAL ELECTRICAL CODE 430-38. Number of Conductors Opened by Overcurrent Device. Motor- running protective devices, other than fuses, thermal cutouts, or ther- mal protectors, shall simultaneously open a sufficient number of un- grounded conductors to interrupt current flow to the motor. 430-39. Motor Controller as Running Overcurrent Protection. A motor controller may also serve as the running overcurrent device where the number of overcurrent units complies with Section 430-37 and where these overcurrent units are operative in both the starting and running position in the case of a direct-current motor, and in the running posi- tion in the case of an alternating-current motor. When a nonautomatic motor controller serves as the running overcurrent device, it is rec- ommended that all ungrounded conductors be opened. 430-40. Thermal Cutouts and Overload Relays. Thermal cutouts, over- load relays, and other devices for motor-running protection which are not capable of opening short circuits, shall be protected by fuses or circuit breakers with ratings or settings in accordance with Section 430-52, unless approved for group installation and marked to indicate the maximum size of fuse or time limit circuit breaker by which they must be protected. Exception: The fuse size marking may be located on the nameplate of approved equipment in which the thermal cutout or relay is used. For instantaneous circuit breakers,see Section 430-52. 430-42. Motors on General Purpose Branch Circuits. Overcurrent pro- tection for motors used on general purpose branch circuits as permit- ted in Article 210,shall be provided as follows: (a) One or more motors without individual running overcurrent protection may be connected to general purpose branch circuits only where the limiting conditions specified for each of two or more mo- tors in Section 430-53(a) are complied with. (b) Motors of larger ratings than specified in Section 430-53(a) may be connected to general purpose branch circuits only in case each mo- tor is protected by running overcurrent protection selected to protect the motor as specified in Section 430-32. Both the controller and the motor-running overcurrent device shall be approved for group in- stallation with the protective device of the branch circuit to which the motor is connected.See Section 430-53. (c) Where a motor is connected to a branch circuit by means of a plug and receptacle, and individual running overcurrent protection is omitted as provided in Section 430-42(a), a rating of the plug and receptacle shall not exceed 15 amperes at 125 volts or 10 amperes at 250 volts. Where individual overcurrent protection is required as pro- vided in Section 430-42(b) for a motor or motor-operated appliance provided with an attachment plug for attaching to the branch circuit through a receptacle, the running overcurrent device shall be an in- tegral part of the motor or of the appliance. The rating of the plug and receptacle shall be assumed to determine the rating of the circuit to which the motor may be connected,as provided in Article 210. (d) The overcurrent device protecting a branch circuit to which a motor or motor-operated appliance is connected shall have sufficient time delay to permit the motor to start and accelerate its load. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-227 430-43. Automatic Restarting. A motor-running protective device which can restart a motor automatically after overcurrent tripping shall not be installed unless approved for use with the motor which it protects. A motor which can restart automatically after shutdown shall not be installed so that its automatic restarting can result in injury to persons. D. Motor Branch Circuit Short Circuit and Ground Fault Protection 430-51. General. The provisions of Part D specify overcurrent de- vices intended to protect the motor branch circuit conductors, the mo- tor control apparatus, and the motors against overcurrent due to short circuits or grounds. They are in addition to or amendatory of the pro- visions of Article 240. 430-52. Rating or Setting for Individual Motor Circuit. The motor branch circuit overcurrent device shall be capable of carrying the start- ing current of the motor. Short circuit and ground fault overcurrent protection shall be considered as being obtained when the overcurrent device has a rating or setting not exceeding the values given in Table 430-152 or 430-153. An instantaneous trip circuit breaker (without time delay) shall be used only if adjustable and if part of a combina- tion controller having overcurrent protection in each conductor and the combination is especially approved for the purpose. Exception: Where the overcurrent protection specified in the tables is not sufficient for the starting current of the motor: a. The rating or setting of a fuse or time limit circuit breaker may be increased but shall in no case exceed 225 per cent of the full load cur- rent for sealed hermetic compressor motors of 400 kva locked rotor or less, nor more than 400 per cent for all other motors. b. The setting of an instantaneous trip circuit breaker (without time delay) may be increased over 700 per cent but shall in no case exceed 1300 per cent of the motor full load current. c. Torque motor branch circuits shall be protected at the motor name- plate current rating.See Section 240-5(a),Exceptions Nos. 1 and 2. For a multispeed motor, a single short circuit and ground fault pro- tective device may be used for one or more windings of the motor pro- vided the rating of the protective device does not exceed the above applicable percentage of the name plate rating of the smallest winding protected. Where maximum protective device ratings shown on manufacturer's heater table for use with a motor controller are less than 15 amperes, the protective device rating shall not exceed the manufacturer's values marked on the equipment. See Example No. 8,Chapter 9,and Diagram in Section 430-1. 430-53. Several Motors on One Branch Circuit. Two or more motors may be connected to the same branch circuit under any of the following conditions: (a) Several motors each not exceeding 1 hp in rating may be used on a branch circuit protected at not more than 20 amperes at 125 volts or 70-228 NATIONAL ELECTRICAL CODE less, or 15 amperes at 600 volts or less, provided that all of the follow- ing conditions are met: (1) The full-load rating of each motor shall not exceed six (6) amperes. (2) The rating of the branch circuit protective device marked on any of the controllers shall not be exceeded. (3) Individual running overcurrent protection shall conform to Section 430-32. (b) If the branch circuit protective device is selected not to exceed that allowed by Section 430-52 for the motor of the smallest rating, two or more motors each having individual running overcurrent protection may be connected to a branch circuit when it can be determined that branch circuit protective device will not open under the most severe normal conditions of service which might be encountered. (c) Except as provided for in Section 430-53(d), two or more mo- tors of any rating, each having individual running overcurrent protec- tion,may be connected to one branch circuit provided all of the follow- ing conditions are complied with: (1) Each motor-running overcurrent device must be approved for group installation with a specified maximum rating of fuse and/or cir- cuit breaker. (2) Each motor controller must be approved for group installation with a specified maximum rating of fuse and/or circuit breaker. (3) Each circuit breaker must be of the time limit type and ap- proved for group installation. (4) The branch circuit shall be protected by fuses or time limit cir- cuit breakers having a rating not exceeding that specified in Section 430-52 for the largest motor connected to the branch circuit plus an amount equal to the sum of the full load current ratings of all other motors connected to the circuit. (5) The branch circuit fuses or time limit circuit breakers must not be larger than allowed by Section 430-40 for the thermal cutout or relay protecting the smallest motor of the group. (6) The conductors of any tap supplying a single motor need not have individual branch circuit protection, provided they comply with either of the following: (1) no conductor to the motor shall have an ampacity less than that of the branch circuit conductors, or (2) no conductor to the motor shall have an ampacity less than one-third that of the branch circuit conductors, with a minimum in accordance with Section 430-22; the conductors to the motor-running protective device being not more than 25 feet long and being protected from physical damage. (d) For the purpose of this Section, a room air conditioner shall be treated as a single motor unit in determining its branch circuit require- ments when all of the following conditions are met: (1) The unit is cord connected. (2) Its rating is not more than 40 amperes full-load current and 250 volts,single phase. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-229 (3) Total full-load current is shown on the unit nameplate rather than that of individual motor currents. (4) The rating of the branch circuit protective device does not ex- ceed the ampacity of the branch circuit conductors or the rating of the receptacle,whichever is less.See Section 422-40. 430-54. Multi-Motor and Combination Load Equipment. The rating of the branch circuit protective device for multimotor and combination load equipment shall not exceed the rating marked on the equipment in accordance with Section 430-7(e). 430-55. Combined Overcurrent Protection. Motor-branch-circuit over- current protection and motor-running overcurrent protection may be combined in a single overcurrent device when the rating or setting of the device provides the running overcurrent protection specified in Sec- tion 430-32. 430-56. Overcurrent Devices—In Which Conductor. Overcurrent devices shall comply with the provisions of Section 240-11. 430-57. Size of Fuseholder. Where fuses are used for motor-branch- circuit protection, the fuseholders shall not be of a smaller size than re- quired to accommodate the fuses specified by Sections 430-152 and 430-153. Exception: Where fuses having time delay appropriate for the start- ing characteristics of the motor are used, fuseholders of smaller size than specified in Sections 430-152 and 430-153 may be used. 430-58. Rating of Circuit Breaker. A circuit breaker for motor-branch- circuit protection shall have a current rating in accordance with Sections 430-52 and 430-110. 430-59. Feeder Taps in Inaccessible Location. If the location of the connection of a tap to the feeder conductors is not accessible, the mo- tor-branch-circuit overcurrent device may be placed where it will be accessible,provided the conductors between the tap and the overcurrent device have the same ampacity as the feeder, or provided they have an ampacity of at least 1/3 that of the feeder and are not more than 25 feet long and are protected from physical damage. 430-60. Selection or Setting of Protective Device. In case the values for branch circuit protective devices determined by Table 430-152 or 430- 153 do not correspond to the standard sizes or ratings of fuses, non- adjustable circuit breakers, or thermal devices, or possible settings of adjustable circuit breakers adequate to carry the load, the next higher size, rating or setting may be used. See Section 240-5(b) for Standard Ratings. E. Motor-Feeder Short-Circuit and Ground Fault Protection 430-61. General. The provisions of Part E specify overcurrent de- vices intended to protect feeder conductors supplying motors against overcurrents due to short circuits or grounds. 430-62. Rating or Setting—Motor Load. (a) A feeder which supplies a specific fixed motor load and consist- ing of conductor sizes based on Section 430-24 shall be provided with overcurrent protection which shall not be greater than the largest rating 70-230 NATIONAL ELECTRICAL CODE or setting of the branch-circuit protective device, for any motor of the group (based on Tables 430-152 and 430-153), plus the sum of the full-load currents of the other motors of the group. Where two or more motors of equal horsepower rating are the larg- est in the group, one of these motors shall be considered as the largest for the above calculations. Where two or more motors of a group must be started simultaneously, it may be necessary to install larger feeder conductors and correspondingly larger ratings or settings of feeder overcurrent protection. See Example No. 8,Chapter 9. (b) For large capacity installations, where heavy capacity feeders , are installed to provide for future additions or changes, the feeder over- current protection may be based on the rated ampacity of the feeder conductors. 430-63. Rating or Setting—Power and Light Loads. Where a feeder supplies a motor load, and in addition a lighting or a lighting and ap- pliance load, the feeder overcurrent protective device may have a rating or setting sufficient to carry the lighting or the lighting and appliance load as determined in accordance with Articles 210 and 220, plus, for a single motor, the rating permitted by Section 430-52, and for two or more motors,the rating permitted by Section 430-62. F. Motor Control Circuits 430-71. General. Part F contains modifications of the general re- quirements and applies to the particular conditions of motor control circuits. CONTROL CIRCUIT (Definition): The control circuit of a control ap- paratus or system is the circuit which carries the electric signals direct- ing the performance of the controller, but does not carry the main power circuit. 430-72. Overcurrent Protection. Conductors of control circuits shall be protected against overcurrent in accordance with Section 240-5(a), Exception No. 5. Exception. Such conductors shall be considered as being properly protected by the branch-circuit overcurrent devices under any one of the following conditions: (1) Where the rating or setting of the branch-circuit overcurrent device is not more than 500 per cent of the ampacity of the control- circuit conductors. (2) Where the controlled device and the point of control (start and stop buttons, pressure switch, thermostatic switch, etc.) are both located on the same machine and the control circuit does not extend beyond the machine and the branch circuit overcurrent device is a fuse or time limit circuit breaker. (3) Where the opening of the control circuit would create a haz- ard; as for example, the control circuit of fire-pump motors, and the like. 430-73. Mechanical Protection of Conductor. Where damage to a con- trol circuit would constitute a hazard, all conductors of such remote- ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-231 control circuit shall be installed in a raceway or be otherwise suitably protected from physical damage outside the control device itself. When one side of the control circuit is grounded, the control circuit shall be so arranged that an accidental ground in the remote control de- vices will not start the motor. 430-74. Disconnection. (a) Control circuits shall be so arranged that they will be discon- nected from all sources of supply when the disconnecting means is in the open position. The disconnecting means may consist of two sepa- rate devices, one of which disconnects the motor and the controller from the source of power supply for the motor, and the other, the control circuit from its power supply. Where the two separate devices are used,they shall be located immediately adjacent one to the other. (b) Where a transformer or other device is used to obtain a reduced voltage for the control circuit and is located in the controller, such transformer or other device shall be connected to the load side of the disconnecting means for the control circuit. G. Motor Controllers 430-81. General. The provisions of Part G are intended to require suitable controllers for all motors. (a) Definition. For definition of "Controller," see Article 100. For the purpose of this Article, the term "Controller" includes any switch or device normally used to start and stop the motor. (b) Stationary Motor of 1%a Horsepower or Less. For a stationary motor rated at 1/a horsepower or less, that is normally left running and is so constructed that it cannot be damaged by overload or failure to start, such as clock motors and the like, the branch-circuit overcurrent device may serve as the controller. (c) Portable Motor of 1/3 Horsepower or Less. For a portable mo- tor rated at 1/3 horsepower or less,the controller may be an attachment plug and receptacle. 430-82. Controller Design. (a) Each controller shall be capable of starting and stopping the motor which it controls, and for an alternating-current motor shall be capable of interrupting the stalled-rotor current of the motor. (b) Autotransformer. An autotransformer starter shall provide an off position, a running position, and at least one starting position. It shall be so designed that it cannot rest in the starting position, or in any position which will render inoperative the overcurrent protective device in the circuit. (c) Rheostats. Rheostats shall conform to the following: (1) Internal Connections. Motor-starting rheostats shall be so de- signed that the contact arm cannot be left on intermediate segments. The point or plate on which the arm rests when in the starting position shall have no electrical connection with the resistor. (2) Under-voltage Release, Direct-Current Motors. Motor-starting rheostats for direct-current motors operated from a constant voltage supply shall be equipped with automatic devices which will interrupt 70-232 NATIONAL ELECTRICAL CODE the supply before the speed of the motor has fallen to less than one- third its normal value. 430-83. Rating. The controller shall have a horsepower rating, which shall not be lower than the horsepower rating of the motor, except as follows: Exception No. 1. Stationary Motor of 2 Horsepower or Less. For a stationary motor rated at 2 horsepower or less, and 300 volts or less, the controller may be a general-use switch having an ampere rating at least twice the full-load current rating of the motor. On AC circuits, general use snap switches suitable only for use on AC (not general use AC-DC snap switches) may be used to control a motor rated at 2 horsepower or less and 300 volts or less having a full- load current rating not exceeding 80 per cent of the ampere rating of the switch. Exception No. 2. Circuit Breaker as Controller. A branch circuit circuit breaker, rated in amperes only, may be used as a controller. Where this circuit breaker is also used for overcurrent protection, it shall conform to the appropriate provisions of this Article governing overcurrent protection. Exception No. 3. Sealed (Hermetic-type) Refrigeration Corn pres- sor Motors. The motor controller shall have both a continuous duty full-load current rating, and a locked-rotor current rating, not less than the nameplate full-load current and locked-rotor current, respectively, of the compressor. In case the motor controller is rated in horsepower, but is without one or both of the foregoing current ratings, equivalent currents shall be determined from the rating as follows: Use Tables 430-148, 430-149, or 430-150 to determine the equivalent full-load current rating. Use Table 430-151 to determine the equivalent locked- rotor current rating. A motor controller controlling more than one motor, or a motor and other loads, shall have a continuous duty full-load current rating and a locked-rotor current rating not less than the combined load as deter- mined in accordance with Section 430-110(d). Exception No. 4. Torque Motors. The motor controller shall have a continuous duty full-load current rating not less than the nameplate cur- rent of the motor. In case the motor controller is rated in horsepower, but is without the foregoing current rating, the equivalent current rating shall be determined from the horsepower rating by using Tables 430- 147,430-148,430-149,or 430-150. 430-84. Need Not Open All Conductors. Except when it serves also as a disconnecting means (see Section 430-111), the controller need not open all conductors to the motor. 430-85. In Grounded Conductors. One pole of the controller may be placed in a permanently grounded conductor provided the controller is so designed that the pole in the grounded conductor cannot be opened without simultaneously opening all conductors of the circuit. 430-86. Motor Not in Sight from Controller. Where a motor and the driven machinery are not in sight from the controller location, the in- stallation shall comply with one of the following conditions: ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-233 (a) The controller disconnecting means is capable of being locked in the open position. (b) A manually operable switch which will disconnect the motor from its source of supply is placed within sight from the motor location. 430-87. Number of Motors Served by Each Controller. Each motor shall be provided with an individual controller. Exception:For motors of 600 volts or less a single controller rated at not less than the sum of the horsepower ratings of all of the motors of the group may serve the group of motors under any one of the following conditions: (a) Where a number of motors drive several parts of a single ma- chine or piece of apparatus such as metal and woodworking machines, cranes,hoists,and similar apparatus. (b) Where a group of motors is under the protection of one over- current device as permitted in Section 430-53(a). (c) Where a group of motors is located in a single room within sight from the controller location. 430-88. Adjustable-Speed Motors. Adjustable-speed motors that are controlled by means of field regulation shall be so equipped and con- nected that they cannot be started under weakened field, unless the motor is designed for such starting. 430-89. Speed Limitation. Machines of the following types shall be provided with speed limiting devices: (a) Separately excited direct-current motors. (b) Series motors. (c) Motor-generators and converters which can be driven at excessive speed from the direct-current end, as by a reversal of current or de- crease in load. Exception No. 1. Unless the inherent characteristics of the ma- chines, the system, or the load and the mechanical connection thereto, are such as to safely limit the speed. Exception No. 2. Unless the machine is always under the manual control of a qualified operator. 430-90. Combination Fuseholder and Switch as Controller. The rating of a combination fuseholder and switch used as a motor-controller shall be such that the fuseholder will accommodate the size of fuse specified in Part C, of Article 430, for motor-running overcurrent pro- tection. Exception: Where fuses having time delay appropriate for the start- ing characteristics of the motor are used, fuseholders of smaller size than specified in Part C,of Article 430 may be used. H. Disconnecting Means 430-101. General. The provisions of Part H are intended to require disconnecting means capable of disconnecting motors and controllers from the circuit. See Diagram in Section 430-1. 70-234 NATIONAL ELECTRICAL CODE 430-102. In Sight from Controller Location. A disconnecting means shall be located in sight from the controller location, except as recog- nized in Section 422-26. 430-103. To Disconnect Both Motor and Controller. The disconnecting means shall disconnect the motor and the controller from all un- grounded supply conductors and shall be so designed that no pole can be operated independently. The disconnecting means may be in the same enclosure with the controller.See Section 430-113. 430-104. To Be Indicating. The disconnecting means shall plainly in- dicate whether it is in the open or closed position. 430-105. Grounded Conductors. One pole of the disconnecting means may disconnect a permanently grounded conductor, provided the dis- connecting means is so designed that the pole in the grounded conduc- tor cannot be opened without simultaneously disconnecting all conduc- tors of the circuit. 430-106. Service Switch as Disconnecting Means. Where an installa- tion consists of a single motor, the service switch may serve as the dis- connecting means, provided it conforms to the requirements of this Article,and is within sight from the controller location, except as recog- nized in Section 422-26. 430-107. Readily Accessible. One of the disconnecting means shall be readily accessible. 430-108. Every Switch. Every switch in the motor branch circuit within sight from the controller location shall comply with the require- ments of Part H. 430-109. Type. The disconnecting means shall be a motor-circuit switch,rated in horsepower,or a circuit breaker,except as follows: Exception No. 1. One-Eighth Horsepower or Less. For stationary motors of 1/2 horsepower or less, the branch-circuit overcurrent device may serve as the disconnecting means. Exception No. 2. Two Horsepower or Less. For stationary motors rated at 2 horsepower or less and 300 volts or less, the disconnecting means may be a general-use switch having an ampere rating not less than twice the full-load current rating of the motor. On AC circuits, general use snap switches suitable only for use on AC (not general use AC-DC snap switches) may be used to discon- nect a motor having a full-load current rating not exceeding 80 per cent of the ampere rating of the switch. Exception No. 3. Over Two Horsepower to and Including 50 Horse- power. The separate disconnecting means required for a motor with an autotransformer type of controller may be a general-use switch where all of the following provisions are complied with: (a) The motor drives a generator which is provided with over- current protection. (b) The controller (1) is capable of interrupting the stalled-rotor current of the motor, (2) is provided with a no-voltage release, and ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-235 (3) is provided with running-over-current protection not exceeding 125 per cent of the motor full-load current rating. (c) Separate fuses or a circuit breaker, rated or set at not more than 150 per cent of the motor full-load current, are provided in the motor branch circuit. Exception No. 4. Exceeding 50 Horsepower. For stationary motors rated at more than 50 horsepower, the disconnecting means may be a motor-circuit switch also rated in amperes, a general-use switch, or an isolating switch. Isolation switches for motors exceeding 50 horsepower, not capable of interrupting stalled-rotor currents, shall be plainly marked "Do not open under load." Exception No. 5. Portable Motors. For portable motors an attach- ment plug and receptacle may serve as the disconnecting means. Exception No. 6. Room Air-Conditioners. For room air-conditioners, see Section 422-43. 430-110. Ampacity and Interrupting Capacity. (a) The disconnecting means shall have an ampacity of at least 115 per cent of the full-load current rating of the motor. (b) The disconnecting means for sealed (hermetic-type) refrigera- tion compressors shall be selected on the basis of the nameplate full- load current and locked-rotor current, respectively of the compressor motor as follows: (1) The ampacity shall be at least 115 per cent of the nameplate full-load current. (2) To determine the equivalent horsepower in complying with the requirements of Section 430-109, select the horsepower rating from Tables 430-148, 430-149, and 430-150 corresponding to the full-load current, and also the horsepower rating from Table 430-151 corre- sponding to the locked-rotor current. In case the nameplate full-load current and locked-rotor current do not correspond to the currents shown in Tables in Sections 430-148, 430-149, and 430-150, respec- tively, the horsepower rating corresponding to the next higher value shall be selected. In case two different horsepower ratings are obtained when applying Tables 430-148, 430-149, 430-150, and 430-151, a horsepower rating at least equal to the larger of the two values obtained shall be selected. (c) The disconnecting means for a torque motor shall be selected on the basis of the nameplate current as follows: (1) The ampacity shall be at least 115 per cent of the nameplate current. (2) To determine the equivalent horsepower in complying with the requirements of Section 430-109, select the horsepower rating from Tables 430-147, 430-148, 430-149, or 430-150 corresponding to the motor current. In case the nameplate current does not correspond to a current shown in the Table, the horsepower rating corresponding to the next higher value shall be selected. 70-236 NATIONAL ELECTRICAL CODE (d) Where one or more sealed (hermetic-type) motor-compressors are used together or are used in combination with other motors and/or loads such as resistance heaters and where the combined load may be simultaneous on a single disconnecting means, the rating and ampacity of the combined load is to be determined as follows: (1) The horsepower rating of the disconnecting means shall be de- termined from the summation of all currents, including resistance loads, at the full-load condition and also at the locked-rotor condition. The combined full-load current and the combined locked-rotor current so obtained shall be considered as a single motor for the purpose of this requirement as follows: The full-load current equivalent to the horsepower rating of each motor, other than a sealed (hermetic-type) motor-compressor, shall be selected from Tables 430-148, 430-149, and 430-150. These full-load currents shall be added to the motor-compressor full-load current(s) and to the rating in amperes of other loads to obtain an equivalent full- load current for the combined load. The locked-rotor current equivalent to the horsepower rating of each motor, other than a sealed (hermetic-type) motor compressor, shall be selected from Table 430-151. The locked-rotor currents shall be added to the motor-compressor locked-rotor current(s) and to the rating in amperes of other loads to obtain an equivalent locked-rotor current for the combined load.Where two or more motors and/or other loads cannot be started simultaneously, appropriate combinations of locked-rotor and full-load current may be employed to determine the equivalent locked-rotor current for the simultaneous combined loads. (2) The ampacity of the disconnecting means shall be at least 115 per cent of the summation of all currents at the full-load condition determined in accordance with Section 430-110(d)(1). (3) For small motor-compressors not having the locked-rotor cur- rent marked on the nameplate or for small motors not covered by Tables 430-147 and 430-150, the locked-rotor current shall be assumed to be six times the full-load current.See Section 430-7(c). 430-111. Switch or Circuit Breaker as Both Controller and Disconnect- ing Means. A switch or circuit breaker complying with the provisions of Section 430-83 may serve as both controller and disconnecting means provided it opens all ungrounded conductors to the motor, is protected by an overcurrent device (which may be the branch circuit fuses) which opens all ungrounded conductors to the switch or circuit breaker,and is of one of the following types: (a) An air-break switch, operable directly by applying the hand to a lever or handle. (b) A circuit breaker operable directly by applying the hand to a lever or handle. (c) An oil switch used on a circuit whose rating does not exceed 600 volts or 100 amperes, or by special permission on a circuit exceed- ing this capacity where under expert supervision. The oil switch or circuit breaker specified above may be both power and manually operable. If power operable, provision should be made to lock it in the open position. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-237 The overcurrent device protecting the controller may be part of the controller assembly or may be separate. An autotransformer type of controller is not included above and will require a separate disconnecting means. 430-112. Motors Served by a Single Disconnecting Means. Each mo- tor shall be provided with individual disconnecting means. Exception: For motors of 600 volts or less a single disconnecting means may serve a group of motors under any one of the following conditions: (a) Where a number of motors drive several parts of a single ma- chine or piece of apparatus such as metal and woodworking machines, cranes,and hoists. (b) Where a group of motors is under the protection of one set of overcurrent devices as permitted by Section 430-53(a). (c) Where a group of motors is in a single room within sight from the location of the disconnecting means. The disconnecting means shall have a rating not less than is re- quired by Section 430-109 for a single motor the rating of which equals the sum of the horsepowers or currents of all the motors of the group. 430-113. Energy From More Than One Source. Equipment receiving electrical energy from more than one source shall be provided with dis- connecting means from each source of electrical energy adjacent to the equipment served. Each source may have a separate disconnecting means. J. Requirements for Over 600 Volts 430-121. General. The provisions of Part J recognize the additional hazard due to the use of high voltage.They are in addition to or amend- atory of the other provisions of this article. Other requirements for cir- cuits and equipment operating at more than 600 volts are in Article 710. 430-122. More Than 7500 Volts. Motors operating at more than 7500 volts between conductors shall be installed in fire-resistant motor rooms. 430-123. Motor Running Overcurrent (Overload) Protection. Running overcurrent protection for a motor of over 600 volts shall consist either of a circuit breaker, or of overcurrent units integral with the controller which shall simultaneously open all ungrounded conductors to the mo- tor. The overcurrent device shall have a setting as specified elsewhere in this Article for motor-running overcurrent (overload) protection. 430-124. Short Circuit and Ground Fault Protection. Each motor branch circuit and feeder of more than 600 volts shall be protected against overcurrent by one of the following means: (a) A circuit breaker of suitable rating so arranged that it can be serviced without hazard. (b) Fuses of the oil-filled or other suitable type. Fuses shall be used with suitable disconnecting means or they shall be of a type which can also serve as the disconnecting means. They shall be so arranged that they cannot be re-fused or replaced while they are energized. (c) Differential protection may be employed to protect an alternat- ing-current motor, the motor control apparatus, and the branch-circuit 70-238 NATIONAL ELECTRICAL CODE conductors against overcurrent due to short circuits or grounds. When all these elements are included within the protected zone of a differen- tial protective system, the ratings or settings specified in Section 430- 52 do not apply. DIFFERENTIAL PROTECTIVE SYSTEM (definition): A differential pro- tective system is a combination of two or more sets of current transform- ers and a relay or relays energized from their interconnected second- aries. The primaries of the current transformers are connected on both sides of the equipment to be protected, both ends of the motor phase windings being brought out for this purpose. All of the apparatus and circuits included between the sets of current transformer primaries constitute the protected zone. The current transformer secondaries and the relay elements are so interconnected that the relay elements respond only to a predetermined difference between the currents entering and leaving the protected zone. When actuated, the relay or relays serve to trip the branch-circuit circuit breaker, thus disconnecting the motor, control apparatus in the motor cir- cuit and the branch-circuit conductors from the source of power and, in the case of a synchronous motor,de-energizing its field circuit. 430-126. Disconnecting Means. The circuit breaker or the fuses spec- ified in Section 430-124 may constitute the disconnecting means if they conform to the other applicable requirements of this Article. K. Protection of Live Parts—All Voltages 430-131. General. The provisions of Part K specify that live parts shall be protected in a manner judged adequate to the hazard involved. 430-132. Where Required. Exposed live parts of motors and control- lers operating at 50 volts or more between terminals, shall be guarded against accidental contact by enclosure,or by location as follows: (a) By installation in a room or enclosure which is accessible only to qualified persons; (b) By installation on a suitable balcony, gallery or platform, so ele- vated and arranged as to exclude unqualified persons; (c) By elevation 8 feet or more above the floor; (d) So that it will be protected by a guard rail when the motor oper- ates at 600 volts or less. Exception: Stationary motors having commutators, collectors and brush rigging located inside of motor end brackets and not conduc- tively connected to supply circuits operating at more than 150 volts to ground. 430-133. Guards for Attendants. Where the live parts of motors or controllers operating at more than 150 volts to ground are guarded against accidental contact only by location as specified in Section 430- 132, and where adjustment or other attendance may be necessary dur- ing the operation of the apparatus, suitable insulating mats or plat- J forms shall be provided so that the attendant cannot readily touch live parts unless standing on the mats or platforms. Where necessary, steps and hand-rails should be installed on or about large machines to afford safe access to parts which must be examined or adjusted during opera- tion. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-239 L. Grounding 430-141. General. The provisions of Part L specify the grounding of motor and controller frames to prevent a potential above ground in the event of accidental contact between live parts and frames. Insulation, isolation, or guarding are suitable alternatives to grounding of motors under certain conditions. 430-142. Stationary Motors. The frames of stationary motors shall be grounded where any of the following conditions exist: (a) supplied by means of metal-enclosed wiring. (b) located in a wet place and not isolated nor guarded. (c) in a hazardous location. (See Articles 500 to 517 inclusive.) • (d) the motor operates with any terminal at more than 150 volts to ground. Grounding of the motor frame is preferable, but where the frame of the motor is not grounded, it shall be permanently and effectively in- sulated from the ground. 430-143. Portable Motors. The frames of portable motors which op- erate at more than 150 volts to ground shall be guarded or grounded. See Section 250-45(d) on grounding of portable appliances in other than residential occupancies. It is recommended that the frames of motors which operate at less than 150 volts to ground be grounded where this can be readily accomplished. See Section 250-59(b) for color of grounding conductor. 430-144. Controllers. Controller cases, except those attached to un- grounded portable equipment and except the lined covers of snap switches,shall be grounded regardless of voltage. 430-145. Method of Grounding. Grounding where required shall be done in the manner specified in Article 250. (a) Grounding Through Terminal Housings. Where the wiring to fixed motors is in Type AC metal-clad cable or metal raceways, junc- tion boxes to house motor terminals shall be provided, and the armor of the cable or the metal raceways shall be connected to them in the manner specified in Article 250. (b) Separation of Junction Box from Motor. The junction box re- quired by Section 430-145(a) may be separated from the motor not more than 6 feet provided the leads to the motor are Type AC metal- clad cable or armored cord or are stranded leads enclosed in flexible or rigid conduit or electrical metallic tubing not smaller than 3/8 inch electrical trade size, the armor or raceway being connected both to the motor and to the box.Where stranded leads are used,protected as spec- ified above, they shall not be larger than No. 10, and shall comply with other requirements of the Code for conductors to be used in race- ways. (c) Grounding of Controller Mounted Devices. Instrument transformer secondaries, and exposed noncurrent-carrying metal or other conduc- tive parts or cases of instrument transformers, meters, instruments, and relays shall be grounded as specified in Sections 250-121 through 250- 125. 70-240 NATIONAL ELECTRICAL CODE Table 430-147. Full-Load Currents in Amperes Direct-Current Motors The following values of full-load currents are for motors running at base speed. HP 120V 240V 1/4 2.9 1.5 3.6 1.8 5.2 2.6 3/4 7.4 3.7 1 9.4 4.7 11/2 13.2 6.6 2 17 8.5 3 25 12.2 5 40 20 71/2 58 29 10 76 38 15 55 20 72 25 89 30 106 40 140 50 173 60 206 75 255 100 341 125 425 150 506 200 675 ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-241 Table 430-148. Full-Load Currents in Amperes Single Phase Alternating Current Motors The following values of full-load currents are for motors running at usual speeds and motors with normal torque characteristics. Motors built for es- pecially low speeds or high torques may have higher full-load currents, and multispeed motors will have full load current varying with speed, in which case the nameplate current ratings shall be used. To obtain full-load currents of 208- and 200-volt motors, increase cor- responding 230-volt motor full-load currents by 10 and 15 per cent, respec- tively. The voltages listed are rated motor voltages. Corresponding nominal sys- tem voltages are 110 to 120 and 220 to 240. HP 115V 230V 4.4 2.2 5.8 2.9 y3 7.2 3.6 9.8 4.9 34 13.8 6.9 1 16 8 1' 20 10 2 24 12 3 34 17 5 56 28 71 80 40 10 100 50 70-242 NATIONAL ELECTRICAL CODE Table 430-149. Full-Load Current Two-Phase A.C.Motors(4-wire) The following values of full-load current are for motors running at speeds usual for belted motors and motors with normal torque characteristics. Mo- tors built for especially low speeds or high torques may require more run- ning current, and multispeed motors will have full load current varying with speed, in which case the nameplate current rating shall be used. Cur- rent in common conductor of 2-phase, 3-wire system will be 1.41 times value given. The voltages listed are rated motor voltages. Corresponding nominal sys- tem voltages are 110 to 120,220 to 240,440 to 480 and 550 to 600 volts. Induction Type Synchronous Type Squirrel-Cage and Wound Rotor tUnity Power Factor Amperes Amperes HP 115V 230V 460V 575V 2300V 220V 440V 550V 2300V 1h 4 2 1 .8 3/4 4.8 2.4 1.2 1.0 1 6.4 3.2 1.6 1.3 1I 9 4.5 2.3 1.8 2 11.8 5.9 3 2.4 3 8.3 4.2 3.3 5 13.2 6.6 5.3 7'h 19 9 8 10 24 12 10 15 36 18 14 20 47 23 19 25 59 29 24 47 24 19 30 69 35 28 56 29 23 40 90 45 36 75 37 31 50 113 56 45 94 47 38 60 133 67 53 14 111 56 44 11 75 166 83 66 18 140 70 57 13 100 218 109 87 23 182 93 74 17 125 270 135 108 28 228 114 93 22 150 312 156 125 32 137 110 26 200 416 208 167 43 182 145 35 t For 90 and 80 per cent P.F.the above figures should be multiplied by 1.1 and 1.25 respectively. ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-243 Table 430-150. Full-Load Current* Three-Phase A.C. Motors Induction Type Synchronous Type Squirrel-Cage and Wound Rotor tUnity Power Factor Amperes Amperes HP 115V 230V 460V 575V 2300V 220V 440V 550V 2300V l 4 2 1 .8 3/4 5.6 2.8 1.4 1.1 1 7.2 3.6 1.8 1.4 11 10.4 5.2 2.6 2.1 2 13.6 6.8 3.4 2.7 3 9.6 4.8 3.9 5 15.2 7.6 6.1 71/2 22 11 9 10 28 14 11 15 42 21 17 20 54 27 22 25 68 34 27 54 27 22 30 80 40 32 65 33 26 40 104 52 41 86 43 35 50 130 65 52 108 54 44 60 154 77 62 16 128 64 51 12 75 192 96 77 20 161 81 65 15 100 248 124 99 26 211 106 85 20 125 312 156 125 31 264 i32 106 25 150 360 180 144 37 158 127 30 200 480 240 192 49 210 168 40 For full-load currents of 208- and 200-volt motors, increase the corre- sponding 230 volt motor full-load current by 10 and 15 per cent,respectively. *These values of full-load current are for motors running at speeds usual for belted motors and motors with normal torque characteristics. Mo- tors built for especially low speeds or high torques may require more run- ning current, and multispeed motors will have full load current varying with speed,in which case the nameplate current rating shall be used. t For 90 and 80 per cent P. F. the above figures shall be multiplied by 1.1 and 1.25 respectively. The voltages listed are rated motor voltages. Corresponding nominal sys- tem voltages are 110 to 120,220 to 240,440 to 480 and 550 to 600 volts. 70-244 NATIONAL ELECTRICAL CODE Table 430-151. Locked-Rotor Current Conversion Table As Determined from Horsepower and Voltage Rating For Use Only With Section 430-83,Exception No. 3,and 430-110(b) Conversion Table Motor Locked-Rotor Current Amperes Max HP Rating Single Phase Two or Three Phase 115 V 230 V 115 V 230 V 460 V 575 V ' 58.8 29.4 24 12 6 4.8 3/4 82.8 41.4 33.6 16.8 8.4 6.6 1 96 48 42 21 10.8 8.4 1 1 120 60 60 30 15 12 2 144 72 78 39 19.8 15.6 3 204 102 — 54 27 24 5 336 168 — 90 45 36 7' 480 240 — 132 66 54 10 600 300 — 162 84 66 15 — — — 240 120 96 20 — — — 312 156 126 25 — — — 384 192 156 30 — — — 468 234 186 40 — — — 624 312 246 50 — — — 750 378 300 60 — — — 900 450 360 75 — — — 1110 558 444 100 — — — 1476 738 588 125 — — — 1860 930 744 150 — — — 2160 1080 864 200 — — — 2880 1440 1152 ARTICLE 430—MOTOR CIRCUITS AND CONTROLLERS 70-245 Table 430-152. Maximum Rating or Setting of Motor Branch Circuit Protective Devices for Motors Marked with a Code Letter Indicating Locked Rotor KVA Per Cent of Full-Load Current Circuit Breaker Setting Type of Motor Fuse Rating Instan- Time taneous Limit Type Type All AC single-phase and polyphase squirrel cage and synchronous motors with full-voltage, resistor or reactor starting: Code Letter A 150 700 150 Code Letter B to E 250 700 200 Code Letter F to V 300 700 250 All AC squirrel cage and synchro- nous motors with auto-trans- former starting: Code Letter A 150 700 150 Code Letter B to E 200 700 200 Code Letter F to V 250 700 200 For certain exceptions to the values specified see Sections 430-52 and 430- 54. The values given in the last column also cover the ratings of nonadjust- able, time-limit types of circuit breakers which may also be modified as in Section 430-52. Synchronous motors of the low-torque, low-speed type (usually 450 RPM or lower), such as are used to drive reciprocating compressors, pumps, etc., which start up unloaded, do not require a fuse rating or circuit breaker set- ting in excess of 200 per cent of full-load current. For motors not marked with a Code Letter,see Table 430-153. 70-246 NATIONAL ELECTRICAL CODE Table 430-153. Maximum Rating or Setting of Motor Branch Circuit Protective Devices for Motors not Marked with a Code Letter Indicating Locked Rotor KVA Per Cent of Full-Load Current Circuit Breaker Setting Type of Motor Fuse Rating Instan- Time taneous Limit Type Type Single-phase, all types 300 700 250 Squirrel-cage and synchronous (full-voltage,resistor and reactor starting) 300 700 250 Squirrel-cage and synchronous (auto-transformer starting) Not more than 30 amperes 250 700 200 More than 30 amperes 200 700 200 High-reactance squirrel-cage Not more than 30 amperes 250 700 250 More than 30 amperes 200 700 200 Wound-rotor 150 700 150 Direct-current Not more than 50 H.P 150 250 150 More than 50 H.P. 150 175 150 Sealed(Hermetic Type) Refrigeration Compressor* 400 KVA locked-rotor or less **175 **175 For certain exceptions to the values specified see Sections 430-52, and 430- 59. The values given in the last column also cover the ratings of nonadjust- able, time-limit types of circuit breakers which may also be modified as in Section 430-52. Synchronous motors of the low-torque low-speed type (usually 450 RPM or lower) such as are used to drive reciprocating compressors, pumps, etc., which start up unloaded, do not require a fuse rating or circuit breaker set- ting in excess of 200 per cent of full-load current. For motors marked with a Code Letter,see Table 430-152. *The locked rotor KVA is the product of the motor voltage and the motor locked rotor current (LRA) given on the motor nameplate divided by 1,000 for single-phase motors,or divided by 580 for 3-phase motors. **This value may be increased to 225 per cent if necessary to permit start- ing. ARTICLE 445—GENERATORS 70-247 ARTICLE 445—GENERATORS 445-1. Location. Generators shall be located in dry places, and also so as to meet the requirements for motors in Section 430-14. Genera- tors installed in hazardous locations as described in Articles 500-503, or in other locations as described in Articles 510-517, 520, 530, and 665,shall also comply with the provisions of those Articles. It is recommended that waterproof covers be provided for use in emer- gency. 445-2. Marking. Each generator shall be provided with a nameplate giving the maker's name, the rating in kilowatts or kilovolt-amperes, the normal volts and amperes corresponding to the rating, and the rev- olutions per minute. 445-3. Drip Pans. Generators shall be provided with suitable drip pans if required by the authority having jurisdiction. 445-4. Overcurrent Protection. (a) Constant-Potential Generators. Constant-potential generators, except alternating-current generators and their exciters, shall be pro- tected from excessive current by circuit breakers or fuses. (b) Two-Wire Generators. Two-wire, direct-current generators may have overcurrent protection in one conductor only if the overcurrent device is actuated by the entire current generated, except that in the shunt field.The overcurrent device shall not open the shunt field. (c) 65 Volts or Less. Generators operating at 65 volts or less and driven by individual motors shall be considered as protected by the overcurrent device protecting the motor if these devices will operate when the generators are delivering not more than 150 per cent of their full-load rated current. (d) Balancer Sets. Two-wire, direct-current generators used in con- junction with balancer sets to obtain neutrals for 3-wire systems shall be equipped with overcurrent devices which will disconnect the 3-wire system in the case of excessive unbalancing of voltages or currents. (e) 3-Wire, Direct-Current Generators. Three-wire, direct-current generators, whether compound or shunt wound, shall be equipped with overcurrent devices, one in each armature lead, and so connected as to be actuated by the entire current from the armature. Such overcur- rent devices shall consist either of a double-pole, double-coil circuit breaker, or of a 4-pole circuit breaker connected in the main and equalizer leads and tripped by two overcurrent devices, one in each armature lead. Such protective devices shall be so interlocked that no one pole can be opened without simultaneously disconnecting both leads of the armature from the system. 445-5. Size of Conductors. The conductors from the generator termi- nals to supplied equipment shall have an ampacity not less than 115 per cent of the nameplate current rating of the generator. Neutral con- ductors shall be the same size as the conductors of the outside legs. 70-248 NATIONAL ELECTRICAL CODE 445-6. Protection of Live Parts. Live parts of generators of more than 150 volts to ground shall not be exposed to accidental contact where ac- cessible to unqualified persons. 445-7. Guards for Attendants. Where necessary for the safety of at- tendants the provisions of Section 430-133 shall be complied with. 445-8. Grounding. If a generator operates at a terminal voltage in excess of 150 volts to ground, the frame shall be grounded in the man- ner specified in Article 250. If the frame is not grounded, it shall be permanently and effectively insulated from the ground. 445-9. Bushings. Where wires pass through an opening in an enclo- sure,conduit box, or barrier, a bushing shall be used to protect the con- ductors from the edges of the opening having sharp edges. The bushing shall have smooth, well rounded surfaces where it may be in contact with the conductors. If used where there may be a presence of oils, grease, or other contaminants, the bushing shall be made of a material not deleteriously affected. ARTICLE 450—TRANSFORMERS AND TRANS- FORMER VAULTS (Including Secondary Ties) 450-1. Application. This Article applies to the installation of all trans- formers except: Exception No. 1.Current transformers. Exception No. 2. Dry-type transformers which constitute a com- ponent part of other apparatus and which conform to the requirements for such apparatus. Exception No.3. Transformers which are an integral part of an X-ray or high frequency apparatus. Exception No. 4. Transformers used with Class 1 low-voltage power circuits or Class 2 remote control low energy power and signal circuits which shall conform to Article 725. Exception No. 5. Transformers for sign and outline lighting which shall conform to Article 600. Exception No. 6. Transformers for electric discharge lighting which shall conform to Article 410. This Article applies to the installation of transformers in hazardous locations except as modified by Article 500. Supplementary rules are found also in Article 710, Circuits and Equip- ment Operating at More than 600 Volts Between Conductors; and Service Installations Over 600 Volts as referred to in Article 230. A. General Provisions 450-2. Location. Transformers and transformer vaults shall be readily accessible to qualified personnel for inspection and maintenance. The ARTICLE 450—TRANSFORMERS AND VAULTS 70-249 location of oil insulated transformers and transformer vaults is covered in Sections 450-24, 450-25, and 450-41; dry type transformers in Sec- tion 450-21 and askarel insulated in Section 450-23. 450-3. Overcurrent Protection. Overcurrent protection shall conform to the following. As used in this Section, the word "transformer"means a transformer or polyphase bank of two or three single phase trans- formers operating as a unit. (a) Primary Side. Each transformer shall be protected by an in- dividual overcurrent device in the primary connection, rated or set at not more than 250 per cent of the rated primary current of the trans- former, except that an individual overcurrent device is not required when the primary circuit overcurrent device provides the protection specified in this Section, and except as provided in Section 450-3(b). (b) Primary and Secondary Side. A transformer having an over- current device in the secondary connection, rated or set at not more than 250 per cent of the rated secondary current of the transformer, or a transformer equipped with a coordinated thermal overload protection by the manufacturer, is not required to have an individual overcurrent device in the primary connection provided the primary feeder overcur- rent device is rated or set to open at a current value not more than six times the rated current of the transformer for transformers having not more than six per cent impedance, and not more than four times rated current of the transformer for transformers having more than six but not more than ten per cent impedance. (c) Potential (Voltage) Transformers. Potential transformers should be protected with primary fuses. The fuse rating should not exceed 10 amperes for circuits of 600 volts or less, and 3 amperes for circuits of more than 600 volts. A resistor should be connected in series with high tension fuses when necessary to limit the possible short-circuit current to a value within the interrupting capacity of the fuse. 450-5. Secondary Ties. As used in this Section, the word "trans- former" means a transformer or a bank of transformers operating as a unit. A secondary tie is a circuit operating at 600 volts or less between phases which connects two power sources or power supply points, such as the secondaries of two transformers. The tie may consist of one or more conductors per phase. (a) Tie Circuits. Tie circuits shall be provided at each end with over- current protection as required in Article 240 of this Code, except un- der the conditions described in Sections 450-5 (a-1 and a-2), in which cases the overcurrent protection may be in accordance with Section 450-5 (a-3). (1) Loads at Transformer Supply Points Only. Where all loads are connected at the transformer supply points at each end of the tie and overcurrent protection is not provided in accordance with Article 240, the rated ampacity of the tie shall be not less than 67 per cent of the rated secondary current of the largest transformer connected to the secondary tie system. (2) Loads Connected Between Transformer Supply Points. Where load is connected to the tie at any point between transformer supply 70-250 NATIONAL ELECTRICAL CODE points and overcurrent protection is not provided in accordance with Article 240, the rated ampacity of the tie shall be not less than 100 per cent of the rated secondary current of the largest transformer connected to the secondary tie system except as otherwise provided in Section 450-5 (a-4). (3) Tie Circuit Protection. Under the conditions described in Sec- tions 450-5(a-1 and 2), both ends of each tie conductor shall be equipped with a protective device which will open at a predetermined temperature of the tie conductor under short circuit conditions. This protection shall consist of one of the following: (1) a fusible link ca- ble connector, terminal or lug, commonly known as a limiter, each be- ing of a size corresponding with that of the conductor and of approved construction and characteristics according to the operating voltage and the type of insulation on the tie conductors, or (2) automatic circuit breakers actuated by devices having comparable current-time charac- teristics. (4) Interconnection of Phase Conductors Between Transformer Sup- ply Points. Where the tie consists of more than one conductor per phase, the conductors of each phase shall be interconnected in order to establish a load supply point, and the protection specified in Section 450-5(a-3) shall be provided in each tie conductor at this point, except as follows: Exception: Loads may be connected to the individual conductors of a multiple-conductor tie without interconnecting the conductors of each phase and without the protection specified in Section 450-5(a-3) at load connection points provided; the tie conductors of each phase have a combined capacity not less than 133 per cent of the rated secondary current of the largest transformer connected to the secondary tie sys- tem; the total load of such taps does not exceed the rated secondary current of the largest transformer;the loads are equally divided on each phase and on the individual conductors of each phase as far as prac- ticable. (5) Tie Circuit Control. Where the operating voltage exceeds 150 volts to ground, secondary ties provided with limiters shall have a switch at each end which when open will de-energize the associated tie conductors and limiters. The current rating of the switch shall be not less than the rated current of the conductors connected to the switch. It shall be capable of opening its rated current, and it shall be con- structed so that it will not open under the magnetic forces resulting from short-circuit current. (b) Overcurrent Protection for Secondary Connections. When sec- ondary ties are used an overcurrent device rated or set at not more than 250 per cent of the rated secondary current of the transformers shall be provided in the secondary connections of each transformer, and in addition an automatic circuit breaker actuated by a reverse-cur- rent relay set to open the circuit at not more than the rated secondary current of the transformer shall be provided in the secondary connec- tion of each transformer. 450-6. Parallel Operation. Transformers may be operated in parallel and switched as a unit provided that the overcurrent protection for each transformer meets the requirements of 450-3. ARTICLE 450—TRANSFORMERS AND VAULTS 70-251 To obtain balanced division of load current, both transformers should have the same rated per cent impedance and be operated on the same voltage- ratio tap. 450-7. Guarding. Transformers shall be guarded as follows: (a) Mechanical Protection. Appropriate provisions shall be made to minimize the possibility of damage to transformers from external causes where the transformers are located where they are exposed to physical damage. (b) Case or Enclosure. Dry-type transformers shall be provided with a noncombustible moisture-resistant case or enclosure which will pro- vide reasonable protection against the accidental insertion of foreign objects. (c) Exposed Live Parts. The transformer installation shall conform with the provisions for guarding of live parts in Section 110-16. (d) Voltage Warning. The operating voltage of exposed live parts of transformer installations shall be indicated by signs or visible mark- ings on the equipment or structures. 450-8. Grounding. Exposed noncurrent carrying metal parts of trans- former installations including fences, guards, etc., shall be grounded where required under the conditions and in the manner prescribed for electrical equipment and other exposed metal parts in Article 250. 450-9. Marking. Each transformer shall be provided with a name- plate giving the name of the manufacturer; rated kilovolt-amperes, frequency, primary and secondary voltage; and the amount and kind of insulating liquid where used and the transformer rating exceeds 25 kva. Where Class B insulation is used in the construction of dry-type transformers rated more than 100 kva, the nameplate shall indicate the temperature rise for this insulation system. B. Specific Provisions Applicable to Different Types of Transformers 450-21. Dry-Type Transformers Installed Indoors. Transformers rated 1121 kva or less shall have a separation of at least 12 inches from combustible material unless separated therefrom by a fire-resistant heat-insulating barrier, or unless of a rating not exceeding 600 volts and completely enclosed except for ventilating openings. Transformers of more than 1121/ kva rating shall be installed in a transformer room of fire-resistant construction unless they are con- structed with 80° C rise (Class B) or 150° C rise (Class H) insulation, and are separated from combustible material not less than 6 feet hori- zontally and 12 feet vertically or are separated therefrom by a fire- resistant heat-insulating barrier. Transformers rated more than 35,000 volts shall be installed in a vault.See Part C of this Article. 450-23. Askarel-Insulated Transformers Installed Indoors. Askarel-in- sulated transformers rated in excess of 25 kva shall be furnished with a pressure-relief vent. Where installed in a poorly ventilated place they shall be furnished with a means for absorbing any gases generated by 70-252 NATIONAL ELECTRICAL CODE arcing inside the case, or the pressure relief vent shall be connected to a chimney or flue which will carry such gases outside the building. As- karel-insulated transformers rated more than 35,000 volts shall be in- stalled in a vault. 450-24. Oil-Insulated Transformers Installed Indoors. Oil-insulated transformers shall be installed in a vault constructed as specified in this Article except as follows: (a) Not Over 1121/2 kva Total Capacity. The provisions for trans- former vaults specified in Part C of this Article apply except that the vault may be constructed of reinforced concrete not less than 4 inches thick. (b) Not Over 600 Volts. A vault is not required provided suitable arrangements are made where necessary to prevent a transformer oil fire igniting other materials, and the total transformer capacity in one location does not exceed 10 kva in a section of the building classified as combustible, or 75 kva where the surrounding structure is classified as fire-resistant construction. (c) Furnace Transformers. Electric furnace transformers of a total rating not exceeding 75 kva may be installed without a vault in a build- ing or room of fire-resistant construction provided suitable arrange- ments are made to prevent a transformer oil fire spreading to other combustible material. (d) Detached Buildings. Transformers may be installed in a build- ing which does not conform with the provisions specified in this Code for transformer vaults, provided neither the building nor its contents present a fire hazard to any other building or property, and provided the building is used only in supplying electric service and the interior is accessible only to qualified persons. 450-25. Oil-Insulated Transformers Installed Outdoors. Combustible material, combustible buildings and parts of buildings, fire escapes, door and window openings shall be safeguarded from fires originating in oil-insulated transformers installed on, attached to, or adjacent to a building or combustible material. Space separations, fire-resistant bar- riers, automatic water spray systems and enclosures which confine the oil of a ruptured transformer tank are recognized safeguards. One or more of these safeguards shall be applied according to the degree of hazard involved in cases where the transformer installation presents a fire hazard. Oil enclosures may consist of fire-resistant dikes, curbed areas or basins, or trenches filled with coarse crushed stone. Oil en- closures shall be provided with trapped drains in cases where the ex- posure and the quantity of oil involved are such that removal of oil is important. C. Provisions for Transformer Vaults 450-41. Location. Vaults shall be located where they can be ventilated to the outside air without using flues or ducts wherever such an ar- rangement is practicable. 450-42. Walls, Roof, and Floor. The walls and roofs of vaults shall be constructed of reinforced concrete, brick, load bearing tile, concrete block, or other fire resistive constructions which have adequate struc- ARTICLE 450—TRANSFORMERS AND VAULTS 70-253 tural strength for the conditions, and a minimum fire resistance of 21 hours according to ASTM Standard El19-67; Fire Tests of Building Construction and Materials; (NFPA No. 251). The floors of vaults in contact with the earth shall be of concrete not less than 4 inches thick but when the vault is constructed with a vacant space or other stories below it, the floor shall have adequate structural strength for the load imposed thereon and a minimum fire resistance of 21/2 hours. 450-43. Doorways.Vault doorways shall be protected as follows: (a) Type of Door. Each doorway leading into a building shall be pro- vided with a tight-fitting door of a type approved for openings in Class A situations as defined in the NFPA Standard for the Installation of Fire Doors and Windows, No. 80 (National Fire Codes, Vol. 4). The authority enforcing this Code may require such a door for an exterior wall opening or on each side of an interior wall opening where condi- tions warrant. (b) Sills. A door sill or curb of sufficient height to confine within the vault the oil from the largest transformer shall be provided and in no case shall the height be less than 4 inches. (c) Locks. Entrance doors shall be equipped with locks, and doors shall be kept locked, access being allowed only to qualified persons. Locks and latches shall be so arranged that the door may be readily and quickly opened from the inside. 450-44. Ventilation. The ventilation shall be adequate to prevent a transformer temperature in excess of the values prescribed in USAS C57.12.00-1965. 450-45. Ventilation Openings. When required by Section 450-44, openings for ventilation shall be provided in accordance with the fol- lowing: (a) Location. Ventilation openings shall be located as far away as possible from doors, windows, fire escapes, and combustible mate- rial. (b) Arrangement. Vaults ventilated by natural circulation of air may have roughly half of the total area of openings required for ven- tilation in one or more openings near the floor and the remainder in one or more openings in the roof or in the sidewalls near the roof; or all of the area required for ventilation may be provided in one or more openings in or near the roof. (c) Size. In the case of vaults ventilated to an outdoor area without using ducts or flues the combined net area of all ventilating openings after deducting the area occupied by screens, gratings, or louvers, shall be not less than 3 square inches per kva of transformer capacity in service, except that the net area shall be not less than 1 square foot for any capacity under 50 kva. (d) Covering. Ventilation openings shall be covered with durable gratings, screens, or louvers, according to the treatment required in or- der to avoid unsafe conditions. (e) Dampers. Where automatic dampers are used in the ventilation openings of vaults containing oil-insulated transformers, the actuating 70-254 NATIONAL ELECTRICAL CODE device should be made to function at a temperature resulting from fire and not at a temperature which might prevail as a result of an over- heated transformer or bank of transformers.Automatic dampers should be so designed and constructed to minimize the possibility of acci- dental closing. (f) Ducts. Ventilating ducts shall be constructed of fire-resistant material. 450-46. Drainage. Where practicable, vaults containing more than 100 kva transformer capacity shall be provided with a drain or other means which will carry off any accumulation of oil or water in the vault unless local conditions make this impracticable. The floor shall be pitched to the drain when provided. 450-47. Water Pipes and Accessories. Any pipe or duct systems for- eign to the electrical installation should not enter or pass through a transformer vault. Where the presence of such foreign systems cannot be avoided, appurtenances thereto which require maintenance at regu- lar intervals shall not be located inside the vault.Arrangements shall be made where necessary to avoid possible trouble from condensation, leaks and breaks in such foreign systems. Piping or other facilities pro- vided for fire protection or for water-cooled transformers are not deemed to be foreign to the electrical installation. 450-48. Storage in Vaults. Materials shall not be stored in trans- former vaults. ARTICLE 460—CAPACITORS 460-1. Application. This Article applies to installation of capacitors on electric circuits in or on buildings. Exception No. 1. Capacitors that are components of other apparatus shall conform to the requirements for such apparatus. Exception No. 2. Capacitors in hazardous locations shall comply with additional requirements in Articles 500-517. 460-2. Location. An installation of capacitors in which any single unit contains more than three gallons of combustible liquid shall be in a vault conforming to Part C of Article 450. 460-3. Mechanical Protection. Capacitors shall be protected from physical damage by location or by suitable fences, barriers or other enclosures. 460-4. Cases and Supports. Capacitors shall be provided with non- combustible cases and supports. 460-5. Transformers Used with Capacitors. Transformers that are components of capacitor installations and are used for the purpose of connecting the capacitor to a power circuit shall be installed in accord- ance with Article 450. The kva rating shall not be less than 135 per cent of the capacitor rating in kvar. ARTICLE 460—CAPACITORS 70-255 460-6. Drainage of Stored Charge. Capacitors shall be provided with a means of draining the stored charge. (a) Time of Discharge. The residual voltage of a capacitor shall be reduced to 50 volts or less within one minute after the capacitor is disconnected from the source of supply in the case of capacitors rated 600 volts or less and in five minutes in the case of capacitors rated more than 600 volts. (b) Means of Discharge. The discharge circuit shall be either per- manently connected to the terminals of the capacitor or capacitor bank, or provided with automatic means of connecting it to the terminals of the capacitor bank on removal of voltage from the line. Manual means of switching or connecting the discharge circuit shall not be used. The windings of motors, of transformers, or of other equipment directly connected to capacitors without a switch or overcurrent device inter- posed,constitutes a suitable discharge means. 460-7. Power Factor Correction — Motor Circuit. The total kvar rating of capacitors which are connected on the load side of a motor con- troller shall not exceed the value required to raise the no-load power factor of the motor to unity. 460-8. Conductor Rating. (a) The ampacity of capacitor circuit conductors shall be not less than 135 per cent of the rated current of the capacitor. The ampacity of conductors which connect a capacitor to the terminals of a motor or to motor circuit conductors, shall be not less than one-third the am- pacity of the motor circuit conductors but not less than 135 per cent of the rated current of the capacitor. (b) Overcurrent Protection. (1) An overcurrent device shall be provided in each ungrounded conductor. Exception: A separate overcurrent device is not required on the load-side of a motor running overcurrent device. (2) The rating or setting of the overcurrent device shall be as low as practicable. (c) Disconnecting Means. (1) A disconnecting means shall be provided in each ungrounded conductor. Exception: A separate disconnecting means is not required for a capacitor connected on the load side of a motor overcurrent device. (2) The disconnecting device need not open all ungrounded con- ductors simultaneously. (3) The disconnecting device may be used for disconnecting the capacitor from the line as a regular operating procedure. (4) The continuous ampacity of the disconnecting device shall be not less than 135 per cent of the rated current of the capacitor. 460-9. Rating or Setting of the Motor-Running Overcurrent Device. Where a motor installation includes a capacitor connected on the load 70-256 NATIONAL ELECTRICAL CODE side of the motor-running overcurrent device, and the overcurrent de- vice used can be adjusted, the rating or setting of the motor overcurrent device shall be determined as provided in Section 430-32, except that instead of using the full-load rated current of the motor as provided in that Section a lower value corresponding with the improved power- factor of the motor circuit shall be used. Section 430-22 applies with respect to the rating of the motor circuit conductors. 460-10. Grounding. Capacitor cases shall be grounded in accordance with Article 250. 460-11. Guarding. All live parts of capacitors which are connected to circuits of more than 600 volts between conductors and are acces- sible to unqualified persons, shall be enclosed or isolated. For isolation by elevation,see Section 710-34(f). 460-12. Marking. Each capacitor shall be provided with a nameplate giving the maker's name, rated voltage, frequency, kvar, or amperes, number of phases, and if filled with a combustible liquid, the amount of liquid in gallons. When filled with a nonflammable liquid, the nameplate shall so state. The nameplate shall also indicate if a capaci- tor has a discharge device inside the case. ARTICLE 470—RESISTORS AND REACTORS For Rheostats see Section 430-82. 470-1. Location. Resistors and reactors shall not be placed where ex- posed to physical damage. Where in the immediate vicinity of easily ignitible material they shall be of the oil-immersed type or shall be en- closed in metal boxes or cabinets. See Article 500 for Hazardous Loca- tions. 470-2. Space Separation. Unless attached to a switchboard or other noncombustible material, or unless mounted as provided in Section 470-3, resistors and reactors shall be separated from combustible ma- terial by a distance of not less than 1 foot. 470-3. On or In a Proximity to Combustible Material. Where placed within a distance of 1 foot from combustible material, resistors and re- actors shall be installed as follows: (a) Slab or Panel. They shall be attached to a slab or panel of non- combustible, nonabsorptive material such as slate, soapstone, or mar- ble. (b) Size of Slab. The slab shall extend beyond the edges of the device and shall have a thickness proportioned to the size and weight of the device but shall not be less than 1/2 inch thick. (c) Supports. The slab shall be secured in position by supports in- dependent of those fastening the device to the slab. Bolts which support the device shall be countersunk at least 1/a inch below the rear surface of the slab and shall be covered with insulating material. ARTICLE 480—BATTERIES 70-257 470-4. Contacts. Fixed and movable contacts shall be so designed that arcing will be kept at a minimum. 470-5. Reactor Materials. Reactors shall be composed of noncom- bustible materials,and shall be mounted on noncombustible bases. 470-6. Mounting. Enclosures when mounted on plain surfaces shall make contact with such surfaces only at the point of support, an air space of at least 1/a inch being maintained between the enclosures and surfaces. 470-7. Conductor Insulation. Insulated conductors used for connec- tion between resistance elements and controllers shall be suitable for an operating temperature of not less than 90°C (194°F). For elevator motor starting service,see Section 620-11(a). Exception: For motor starting service other conductor insulations may be used. 470-8. Incandescent Lamps as Resistors. Incandescent lamps may be used as protective resistors for automatic controllers, or may by special permission be used as resistors in series with other devices and shall conform to the following: (a) Mounting. They shall be mounted in porcelain receptacles on noncombustible supports. (b) Voltage. They shall be so arranged that they cannot have im- pressed upon them a voltage greater than that for which they are rated. (c) Nameplate. They shall be provided with a nameplate, perma- nently attached, giving the wattage and voltage of the lamp to be used in each receptacle. (d) Not Carry Main Current. They shall not carry or control the main current nor constitute the regulating resistance of the device. ARTICLE 480—STORAGE BATTERIES 480-1. Scope. The provisions of this Article shall apply to all station- ary installations of storage batteries using acid or alkali as the electro- lyte and consisting of a number of cells connected in series with a nom- inal voltage in excess of 16 volts. 480-2. Definition of Nominal Battery Voltage. The nominal battery voltage shall be calculated on the basis of 2.0 volts per cell for the lead- acid type,and 1.2 volts per cell for the alkali type. 480-3. Wiring and Apparatus Supplied from Batteries. Wiring, ap- pliances, and apparatus supplied from storage batteries shall be subject to the requirements of this Code applying to wiring, appliances, and apparatus operating at the same voltage, except as otherwise provided for communication systems in Article 800. 480-4. Insulation of Batteries of Not Over 250 Volts. The provisions of this Section shall apply to storage batteries having the cells so con- 70-258 NATIONAL ELECTRICAL CODE nected as to operate at a nominal battery voltage not exceeding 250 volts. (a) Lead-Acid Batteries. Cells in lead-lined wood tanks, where the number of cells in series does not exceed 25, shall be supported indi- vidually on glass or glazed porcelain insulators. Where the number of the cells in series exceeds 25, the cells shall be supported individually on oil insulators. (b) Alkali-Type Batteries. Cells of the alkali type in jars made of conducting material shall be installed in trays of nonconducting mate- rial, with not over 20 cells in a series circuit in any one such tray, or the cells may be supported singly or in groups on porcelain or other suitable insulators. (c) Unsealed Jars. Cells in unsealed jars made of nonconductive material shall be assembled in trays of glass or supported on glass or glazed porcelain insulators; or, where installed on a rack, shall be sup- ported singly or in groups on glass or other suitable insulators. (d) Sealed Rubber Jars. Cells in sealed rubber or composition con- tainers shall require no additional insulating support where the total nominal voltage of all cells in series does not exceed 150 volts. Where the total voltage exceeds 150 volts, batteries shall be sectionalized into groups of 150 volts or less and each group shall have the individual cells installed in trays or on racks.Where trays or racks are required for this type of cell, such trays or racks shall be supported on glass or glazed porcelain insulators or oil-type insulators. (e) Sealed Glass or Plastic Jars. Cells in sealed glass jars or in sealed jars of approved heat resistant plastic, with or without wood trays,require no additional insulation. 480-5. Insulation of Batteries of Over 250 Volts. The provisions of Section 480-4 shall apply to storage batteries having the cells so con- nected as to operate at a nominal voltage exceeding 250 volts and, in addition, the provisions of this section shall also apply to such batteries. Cells shall be installed in groups having a total nominal voltage of not over 250 volts,in trays or on racks supported on oil insulators. Exception No. 1. Where each individual cell, or sub-group in the tray or rack, is supported on oil insulators, no additional insulation for the group need be provided. Exception No. 2. Cells of not over 10 ampere-hour capacity in sealed glass jars may be grouped in trays, the total nominal voltage of all cells in such group not to exceed 250 volts, and each such tray to be sup- ported on glass or glazed porcelain insulators, the trays being mounted on racks supported on oil insulators with a total nominal voltage of not over 500 volts for all cells in series on each such insulated rack. Maximum protection is secured by sectionalizing high-voltage batteries into cell groups insulated from each other. 480-6. Racks and Trays. Racks and trays shall conform to the follow- ing: (a) Racks. Racks, as required in this Article, refer to frames de- signed to support cells or trays.They shall be substantial,and made of: ARTICLE 480—BATTERIES 70-259 (1) Wood, so treated as to be resistant to deteriorating action by the electrolyte;or (2) Metal, so treated as to be resistant to deteriorating action by the electrolyte, and provided with nonconducting members directly sup- porting the cells or with suitable insulating material on conducting members;or (3) Other similar suitable construction. (b) Trays. Trays refer to frames such as crates or shallow boxes usually of wood or other nonconducting material, so constructed or treated as to be resistant to deteriorating action by the electrolyte. 480-7. Battery Rooms. Battery rooms shall conform to the following: (a) Use. Separate battery rooms or enclosures shall be required only for batteries in unsealed jars and tanks where the aggregate ca- pacity at the 8-hour discharge rate exceeds 5 kilowatt hours. (b) Ventilation. Provision shall be made for sufficient diffusion and ventilation of the gases from the battery to prevent the accumulation of an explosive mixture in the battery room. (c) Wiring Method. In storage battery rooms, bare conductors, open wiring, Type MI cable, type ALS cable, or conductors in rigid conduit or electrical metallic tubing shall be used as the wiring method. Rigid metal conduit, or electrical metallic tubing, where used, shall be of corrosion-resistant material or shall be suitably protected from corro- sion. (d) Varnished-Cambric Conductors. Varnished-cambric-covered con- ductors,Type V,shall not be used. (e) Bare Conductors. Bare conductors shall not be taped. (f) Terminals. Where metal raceway or other metallic covering is used in the battery room, at least 12 inches of the conductor at the end connected to a cell terminal shall be free from the raceway or metallic covering and shall be bushed by a substantial glazed insulating bush- ing. The end of the raceway shall be sealed tightly to resist the entrance of electrolyte by spray or by creepage. Sealing compound, rubber in- sulating tape or other suitable material shall be used for this purpose. 70-260 Chapter 5. Special Occupancies ARTICLE 500—HAZARDOUS LOCATIONS 500-1. Scope. The provisions of Articles 500-503 apply to locations in which the authority having jurisdiction judges the apparatus and wir- ing to be subject to the conditions indicated by the following classifica- tions. It is intended that each room, section or area (including motor and generator rooms, and rooms for the enclosure of control equip- ment) shall be considered individually in determining its classification. Except as modified in Articles 500-503, all other applicable rules con- tained in. this Code shall apply to electrical apparatus and wiring in- stalled in hazardous locations. For definitions of "approved" and "explosion-proof" as used in these Articles, refer to Article 100; "dust- ignition-proof"is defined in Section 502-1. Equipment and associated wiring approved as intrinsically safe may be installed in any hazardous location for which it is approved, and the provisions of Articles 500-517 need not apply to such installation. Intrinsically safe equipment and wiring are incapable of releasing suf- ficient electrical energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture. Abnormal con- ditions will include accidental damage to any part of the equipment or wiring, insulation or other failure of electrical components, application of over-voltage, adjustment and maintenance operations, and other similar conditions. Through the exercise of ingenuity in the layout of electrical installations for hazardous locations, it is frequently possible to locate much of the equipment in less hazardous or in nonhazardous areas and thus to reduce the amount of special equipment required. In some cases, hazards may be reduced or hazardous areas limited or eliminated by adequate positive- pressure ventilation from a source of clean air in conjunction with effective safeguards against ventilation failure. It is recommended that the authority having jurisdiction be consulted before such layouts are prepared. It is rec- ommended also that the authority having jurisdiction be familiar with such recorded industrial experience as well as with such standards of the National Fire Protection Association as may be of use in the classification of various areas with respect to hazard. For further information see NFPA No. 30, Flammable and Combustible Liquids Code; No. 32, Standard for Dry Cleaning Plants; No. 35M, Organic Coatings Manufacture; and No. 36, Standard for Solvent Extraction Plants. For recommendations for protection against static electricity hazards, refer to the standards of the National Fire Protection Association on this subject. Where rigid conduit is used in hazardous locations, it is necessary to have all threaded joints made up wrench tight to minimize sparking when fault current flows through the conduit system. Where it is impractical to make a threaded joint tight,a bonding jumper should be utilized. All conduit referred to herein shall be threaded with standard conduit cutting die which provides 3/4 inch taper per foot. Such conduit shall be ARTICLE 500—HAZARDOUS LOCATIONS 70-261 made up wrench tight to minimize sparking when fault current flows through the conduit system. Where it is impractical to make a threaded joint tight,a bonding jumper shall be utilized. 500-2. Special Precaution. The intent of Articles 500-503 is to require a form of construction of equipment, and of installation that will insure safe performance under conditions of proper use and maintenance. It, therefore, is assumed that inspection authorities and users will exercise more than ordinary care with regard to installation and maintenance. The characteristics of various atmospheric mixtures of hazardous gases, vapors and dusts depend on the specific hazardous material in- volved. It is necessary therefore that equipment be approved not only for the class of location but also for the specific gas, vapor or dust that will be present. For purposes of testing and approval, various atmospheric mixtures have been grouped on the basis of their hazardous characteristics, and facilities have been made available for testing and approval of equipment for use in the following atmospheric groups: Group A,Atmospheres containing acetylene; Group B, Atmospheres containing hydrogen, or gases or vapors of equiv- alent hazard such as manufactured gas; Group C, Atmospheres containing ethyl ether vapors, ethylene, or cyclo- propane; Group D, Atmospheres containing gasoline, hexane, naphtha, benzine, butane, propane, alcohol, acetone, benzol, lacquer solvent vapors, or natural gas; Group E, Atmospheres containing metal dust, including aluminum mag- nesium,and their commerical alloys,and other metals of similarly hazardous characteristics. Group F,Atmospheres containing carbon black,coal or coke dust; Group G,Atmospheres containing flour,starch,or grain dusts. See Tentative Interim Amendment No. 146 at back of book. 500-3. Specific Occupancies. See Articles 510 to 517 inclusive for rules applying to garages, aircraft hangars, gasoline dispensing and serv- ice stations, bulk storage plants, finishing processes, and flammable anesthetics. 500-4. Class I Locations. Class I locations are those in which flam- mable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitible mixtures. Class I locations shall include the following: (a) Class I, Division 1. Locations (1) in which hazardous concen- trations of flammable gases or vapors exist continuously, intermittently, or periodically under normal operating conditions, (2) in which haz- ardous concentrations of such gases or vapors may exist frequently be- cause of repair or maintenance operations or because of leakage, or (3) in which breakdown or faulty operation of equipment or proc- esses which might release hazardous concentrations of flammable gases or vapors,might also cause simultaneous failure of electrical equipment. 70-262 NATIONAL ELECTRICAL CODE This classification usually includes locations where volatile flammable liquids or liquefied flammable gases are transferred from one container to another; interiors of spray booths and areas in the vicinity of spraying and painting operations where volatile flammable solvents are used; locations containing open tanks or vats of volatile flammable liquids; drying rooms or compartments for the evaporation of flammable solvents; locations con- taining fat and oil extraction apparatus using volatile flammable solvents; portions of cleaning and dyeing plants where hazardous liquids are used; gas generator rooms and other portions of gas manufacturing plants where flam- mable gas may escape; inadequately ventilated pump rooms for flammable gas or for volatile flammable liquids; the interiors of refrigerators and freez- ers in which volatile, flammable materials are stored in open, lightly stop- pered, or easily ruptured containers, and all other locations where hazard- ous concentrations of flammable vapors or gases are likely to occur in the course of normal operations. (b) Class I, Division 2. Locations (1) in which volatile flammable liquids or flammable gases are handled, processed or used, but in which the hazardous liquids, vapors or gases will normally be confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown of such containers or sys- tems, or in case of abnormal operation of equipment, (2) in which hazardous concentrations of gases or vapors are normally prevented by positive mechanical ventilation, but which might become hazardous through failure or abnormal operation of the ventilating equipment, or (3) which are adjacent to Class I, Division 1 locations, and to which hazardous concentrations of gases or vapors might occasionally be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided. This classification usually includes locations where volatile flammable liquids or flammable gases or vapors are used, but which, in the judgment of the authority having jurisdiction,would become hazardous only in case of an accident or of some unusual operating condition. The quantity of hazardous material that might escape in case of accident, the adequacy of ventilating equipment, the total area involved, and the record of the industry or business with respect to explosions or fires are all factors that should re- ceive consideration in determining the classification and extent of each hazardous area. Piping without valves, checks, meters and similar devices would not ordinarily be deemed to introduce a hazardous condition even though used for hazardous liquids or gases. Locations used for the storage of hazardous liquids or of liquefied or compressed gases in sealed containers would not normally be considered hazardous unless subject to other hazardous con- ditions also. Electrical conduits and their associated enclosures separated from process fluids by a single seal or barrier shall be classed as Division 2 locations if the outside of conduit and enclosures is a nonhazardous area. 500-5. Class II Locations. Class II locations are those which are haz- ardous because of the presence of combustible dust. Class II locations shall include the following: (a) Class II, Division 1. Locations (1) in which combustible dust is or may be in suspension in the air continuously, intermittently, or pe- ARTICLE 500—HAZARDOUS LOCATIONS 70-263 riodically under normal operating conditions, in quantities sufficient to produce explosive or ignitible mixtures, (2) where mechanical failure or abnormal operation of machinery or equipment might cause such mixtures to be produced, and might also provide a source of ignition through simultaneous failure of electrical equipment, operation of protection devices, or from other causes, or (3) in which dusts of an electrically conducting nature may be present. This classification usually includes the working areas of grain handling and storage plants; rooms containing grinders or pulverizers, cleaners, graders, scalpers, open conveyors or spouts, open bins or hoppers, mixers or blenders, automatic or hopper scales, packing machinery, elevator heads and boots, stock distributors, dust and stock collectors (except all-metal collectors vented to the outside), and all similar dust producing machinery and equipment in grain processing plants, starch plants, sugar pulverizing plants, malting plants, hay grinding plants, and other occupancies of similar nature; coal pulverizing plants (except where the pulverizing equipment is essentially dust-tight); all working areas where metal dusts and powders are produced, processed, handled, packed or stored (except in tight con- tainers); and all other similar locations where combustible dust may,under normal operating conditions, be present in the air in quantities sufficient to produce explosive or ignitible mixtures. Combustible dusts which are electrically nonconducting include dusts produced in the handling and processing of grain and grain products, pulverized sugar and cocoa, dried egg and milk powders, pulverized spices, starch and pastes, potato and woodflour, oil meal from beans and seed, dried hay, and other organic materials which may produce combustible dusts when processed or handled. Electrically conducting nonmetallic dusts include dusts from pulverized coal,coke and charcoal.Dusts containing mag- nesium or aluminum are particularly hazardous and every precaution must be taken to avoid ignition and explosion. (b) Class II, Division 2. Locations in which combustible dust will not normally be in suspension in the air, or will not be likely to be thrown into suspension by the normal operation of equipment or ap- paratus, in quantities sufficient to produce explosive or ignitible mix- tures, but (1) where deposits or accumulations of such dust may be sufficient to interfere with the safe dissipation of heat from electrical equipment or apparatus, or (2) where such deposits or accumulations of dust on, in, or in the vicinity of electrical equipment might be ig- nited by arcs,sparks or burning material from such equipment. Locations where dangerous concentrations of suspended dust would not be likely, but where dust accumulations might form on, or in the vicinity of electrical equipment, would include rooms and areas containing only closed spouting and conveyors, closed bins or hoppers, or machines and equipment from which appreciable quantities of dust would escape only under ab- normal operating conditions; rooms or areas adjacent to locations de- scribed in Section 500-5(a), and into which explosive or ignitible concentra- tions of suspended dust might be communicated only under abnormal operating conditions; rooms or areas where the formation of explosive or ignitible concentrations of suspended dust is prevented by the operation of effective dust control equipment; warehouses and shipping rooms where dust producing materials are stored or handled only in bags or containers; and other similar locations. 500-6. Class III Locations. Class III locations are those which are haz- ardous because of the presence of easily ignitible fibers or flyings, but 70-264 NATIONAL ELECTRICAL CODE in which such fibers or flyings are not likely to be in suspension in air in quantities sufficient to produce ignitible mixtures. Class III locations shall include the following: (a) Class III, Division 1. Locations in which easily ignitible fibers or materials producing combustible flyings are handled, manufactured or used. Such locations usually include some parts of rayon, cotton and other textile mills; combustible fiber manufacturing and processing plants; cotton gins and cotton-seed mills; flax processing plants; clothing manufacturing plants; woodworking plants; and establishments and industries involving similar hazardous processes or conditions. Easily ignitible fibers and flyings include rayon, cotton (including cotton linters and cotton waste), sisal or henequen, istle, jute, hemp, tow, cocoa fiber, oakum, baled waste kapok, Spanish moss, excelsior and other ma- terials of similar nature. (b) Class III, Division 2. Locations in which easily ignitible fibers are stored or handled (except in process of manufacture). ARTICLE 501—CLASS I INSTALLATIONS— HAZARDOUS LOCATIONS 501-1. General. The general rules of this Code shall apply to the in- stallation of electrical wiring and equipment in locations classified as Class I under Section 500-4 except as modified by this Article. 501-2. Transformers and Capacitors. The installation of transformers and capacitors shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, transform- ers and capacitors shall conform to the following: (1) Containing a Liquid that Will Burn. Transformers and capac- itors containing a liquid that will burn shall be installed only in approved vaults, which shall conform to Sections 450-41 to 450-48 in- clusive, and in addition, (1) there shall be no door or other com- municating opening between the vault and the hazardous area, (2) ample ventilation shall be provided for the continuous removal of haz- ardous gases or vapor, (3) vent openings or ducts shall lead to a safe location outside of buildings, and (4) vent ducts and openings shall be of sufficient area to relieve explosion pressures within the vault, and all portions of vent ducts within the buildings shall be of reinforced concrete construction. (2) Not Containing a Liquid that Will Burn. Transformers and capacitors which do not contain a liquid that will burn shall (1) be installed in vaults conforming to the requirements of Section 501-2(a- 1),or (2) be approved for Class I locations (explosion-proof). (b) Class I, Division 2. In Class I, Division 2 locations, transform- ers and capacitors shall conform to Sections 450-21 to 450-25 inclu- sive. ARTICLE 501—CLASS I INSTALLATIONS 70-265 501-3. Meters, Instruments and Relays. The installation of meters, in- struments and relays shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 location, meters, in- struments and relays, including kilowatt-hour meters, instrument trans- formers and resistors, rectifiers and thermionic tubes, shall be provided with enclosures approved for Class I locations. (b) Class I, Division 2. In Class I, Division 2 locations, meters, in- struments and relays shall conform to the following: (1) Contacts. Switches and circuit-breakers, and make and break contacts of push buttons, relays, and alarm bells or horns, shall have enclosures approved for Class I locations, unless general purpose en- closures are provided, and current interrupting contacts are (1) im- mersed in oil, (2) enclosed within a chamber hermetically sealed against the entrance of gases or vapors, or (3) in circuits which under normal conditions do not release sufficient energy to ignite a specific hazardous atmospheric mixture. (2) Resistors and Similar Equipment. Resistors, resistance devices, thermionic tubes, and rectifiers, which are used in or in connection with meters, instruments and relays, shall conform to Section 501-3(a), except that enclosures may be of general purpose type when such equipment is without make and break or sliding contacts (other than as provided in Section 501-3(b) (1) above) and when the maximum op- erating temperature of any exposed surface will not exceed eighty per cent (80%) of the ignition temperature in degrees Centigrade of the gas or vapor involved as determined by ASTM test procedure (Designa- tion D286-30). (3) Without Make or Break Contacts. Transformer windings, im- pedance coils, solenoids and other windings which do not incorporate sliding or make and break contacts shall be provided with enclosures which may be of the general purpose type. (4) General Purpose Assemblies. Where an assembly is made up of components for which general purpose enclosures are acceptable under Sections 501-3(b-1, 2, 3), a single general purpose enclosure is acceptable for the assembly. Where such an assembly includes any of the equipment described in Section 501-3(b-2) the maximum obtain- able surface temperature of any component of the assembly shall be clearly and permanently indicated on the outside of the enclosure. (5) Fuses. Where general purpose enclosures are permitted un- der Sections 501-3(b), (1), (2), (3), (4), fuses for overcurrent protection of the instrument circuits may be mounted in general pur- pose enclosures provided such fuses do not exceed 3 ampere rating at 120 volts and provided each such fuse is preceded by a switch conform- ing to Section 501-3(b)(1). (6) Connections. To facilitate replacements, process control in- struments may be connected through flexible cord, attachment plug and receptacle,provided; 1. a switch conforming to Section 501-3(b) (1) is provided so that the plug is not depended on to interrupt current,and 2. current does not exceed 3 amperes at 120 volts,and 70-266 NATIONAL ELECTRICAL CODE 3. power supply cord does not exceed 3 feet, is of a type approved for extra hard usage or for hard usage if protected by location and is supplied through a plug and receptacle of the locking and grounding type,and 4. only necessary receptacles are provided,and 5. the receptacle carries a label warning against unplugging under load. 501-4. Wiring Methods. Wiring methods shall conform to the follow- ing: (a) Class I, Division 1. In Class I, Division 1 locations, threaded rigid metal conduit or Type MI cable with termination fittings approved for the location shall be the wiring method employed.All boxes,fittings, and joints shall be threaded for connection to conduit or cable termina- tions, and shall be explosion-proof. Threaded joints shall be made up with at least five threads fully engaged. Type MI cable shall be installed and supported in a manner to avoid tensile stress at the termination fit- tings. Where necessary to employ flexible connections, as at motor terminals, flexible fittings approved for Class I locations (explosion- proof) shall be used. (b) Class I, Division 2. In Class I, Division 2 locations, threaded rigid metal conduit or Types MI, MC or ALS cable with approved ter- mination fittings shall be the wiring method employed. Type MI, MC or ALS cable shall be installed in a manner to avoid tensile stress at the termination fittings. Boxes, fittings and joints need not be explosion proof except as required by Sections 501-5(b) (1) and (2). Where provision must be made for limited flexibility, as at motor terminals, flexible metal fittings, flexible metal conduit with approved fittings, or flexible cord approved for extra hard usage and provided with ap- proved bushed fittings shall be used. An additional conductor for grounding shall be included in the flexible cord unless other acceptable means of grounding are provided. 501-5. Sealing and Drainage. Seals are provided in conduit and ca- ble systems to prevent the passage of gases, vapors or flames from one portion of the electrical installation to another through the conduit. Such communication through Type MI cable is inherently prevented by construction of the cable, but sealing compound is used in cable termination fittings to exclude moisture and other fluids from the cable insulation, and shall be of a type approved for the conditions of use. Seals in conduit and cable systems shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, seals shall be located as follows: (1) In each conduit run entering an enclosure for switches, circuit breakers, fuses, relays, resistors or other apparatus which may pro- duce arcs, sparks or high temperatures. Seals shall be placed as close as practicable and in no case more than 18 inches from such enclosures. There shall be no junction box or similar enclosure in the conduit run between the sealing fitting and the apparatus enclosure. (2) In each conduit run of 2-inch size or larger entering the en- closure or fitting housing terminals, splices or taps, and within 18 inches of such enclosure or fitting. ARTICLE 501—CLASS I INSTALLATIONS 70-267 Where two or more enclosures for which seals are required under Sec- tions 501-5(a-1, 2) are connected by nipples or by runs of conduit not more than 36 inches long, a single seal in each such nipple connection or run of conduit would be sufficient if located not more than 18 inches from either enclosure. Ordinary conduit fittings of the "L," "T" or "Cross" type would not usually be classed as enclosures when not larger than the trade size of the conduit. (3) In each conduit run leaving the Class I, Division 1 hazardous area. The sealing fitting may be located on either side of the boundary of such hazardous area, but shall be so designed and installed that any gases or vapors which may enter the conduit system, within the Divi- sion 1 hazardous area, will not enter or be communicated to the conduit beyond the seal. There shall be no union, coupling, box or fitting in the conduit between the sealing fitting and the point at which the con- duit leaves the Division 1 hazardous area. (b) Class I, Division 2. In Class I, Division 2 locations, seals shall be located as follows: (1) For connections to enclosures which are required to be ap- proved for Class I locations, seals shall be provided in conformance to , Sections 501-5(a-1, 2). All portions of the conduit run or nipple be- tween the seal and such enclosure shall conform to Section 501-4(a). (2) In each conduit run passing from the Class I, Division 2 haz- ardous area into a nonhazardous area. The sealing fitting may be lo- cated on either side of the boundary of such hazardous area, but shall be so designed and installed that any gases or vapors which may enter the conduit system, within the Division 2 hazardous area,will not enter or be communicated to the conduit beyond the seal. Rigid conduit shall be used between the sealing fitting and the point at which the conduit leaves the hazardous area, and a threaded connection shall be used at the sealing fitting. There shall be no union, coupling, box or fitting in the conduit between the sealing fitting and the point at which the con- duit leaves the hazardous area. (c) Class I, Divisions 1 and 2. Where seals are required, they shall conform to the following: (1) Fittings. Enclosures for connections or for equipment shall be provided with approved integral means for sealing, or sealing fittings approved for Class I locations shall be used. Sealing fittings shall be accessible. (2) Compound. Sealing compound shall be approved for the pur- pose, shall not be affected by the surrounding atmosphere or liquids, and shall not have a melting point of less than 93°C. (200°F.). (3) Thickness of Compound. In the completed seal, the minimum thickness of the sealing compound shall be not less than the trade size of the conduit,and in no case less than 5/s inch. (4) Splices and Taps. Splices and taps shall not be made in fit- tings intended only for sealing with compound, nor shall other fittings in which splices or taps are made be filled with compound. 70-268 NATIONAL ELECTRICAL CODE (5) Assemblies. In an assembly where equipment which may produce arcs, sparks or high temperatures is located in a compartment separate from the compartment containing splices or taps, and an in- tegral seal is provided where conductors pass from one compartment to the other, the entire assembly shall be approved for Class I locations. Seals in conduit connections to the compartment containing splices or taps shall be provided in Class I,Division 1 locations where required by Section 501-5(a-2). (d) Drainage. (1) Control Equipment. Where there is probability that liquid or other condensed vapor may be trapped within enclosures for control equipment or at any point in the raceway system, approved means shall be provided to prevent accumulation or to permit periodic draining of such liquid or condensed vapor. (2) Motors and Generators. Where the authority having jurisdic- tion judges that there is probability that liquid or condensed vapor may accumulate within motors or generators,joints and conduit systems shall be arranged to minimize entrance of liquid. If means to prevent accumulation or to permit periodic draining are judged necessary, such means shall be provided at the time of manufacture, and shall be deemed an integral part of the machine. (3) Canned Pumps, Process Connections for Flow, Pressure or Anal- ysis Measurement, Etc., frequently depend upon a single seal diaphragm or tube to prevent process fluids from entering the electrical conduit system. An additional approved seal or barrier shall be provided with an adequate drain between the seals in such a manner that leaks would be obvious. See also the last paragraph of footnote in Section 500-4 (b). 501-6. Switches, Circuit Breakers, Motor Controllers and Fuses. Switches, circuit breakers, motor controllers and fuses shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, switches, circuit breakers, motor controllers and fuses, including push buttons, relays and similar devices, shall be provided with enclosures, and the enclosure in each case together with the enclosed apparatus shall be approved as a complete assembly for use in Class I locations. (b) Class I, Division 2. Switches, circuit breakers, motor controllers and fuses in Class I, Division 2 locations shall conform to the follow- ing: (1) Type Required. Circuit breakers, motor controllers and switches intended to interrupt current in the normal performance of the function for which they are installed shall be provided with enclo- sures approved for Class I locations, unless general purpose enclosures are provided and (1) the interruption of current occurs within a cham- ber hermetically sealed against the entrance of gases and vapors, or (2) the current interrupting contacts are oil-immersed and the device is approved for locations of this class and division. This includes service and branch circuit switches and circuit breakers; motor controllers, including push buttons, pilot switches, relays and motor- ARTICLE 501—CLASS I INSTALLATIONS 70-269 overload protective devices; and switches and circuit breakers for the con- trol of lighting and appliance circuits. Oil-immersed circuit breakers and controllers of ordinary general use type may not confine completely the arc produced in the interruption of heavy overloads, and specific approval for locations of this class and division is therefore necessary. (2) Isolating Switches. Enclosures for disconnecting and isolat- ing switches without fuses and which are not intended to interrupt current may be of general purpose type. (3) Fuses. For the protection of motors, appliances and lamps, except as provided in Section 501-6(b-4), (1) standard plug or car- tridge fuses may be used provided they are placed within enclosures approved for the purpose and for the location, or (2) fuses of a type in which the operating element is immersed in oil or other approved liquid, or is enclosed within a chamber hermetically sealed against the entrance of gases and vapors may be used provided they are approved for the purpose and are placed within general purpose enclosures. (4) Fuses or Circuit Breakers for Overcurrent Protection. When not more than 10 sets of approved enclosed fuses, or not more than 10 circuit breakers which are not intended to be used as switches for the interruption of Current, are installed for branch or feeder circuit pro- tection in any one room, area or section of this class and division, the enclosures for such fuses or circuit breakers may be of general purpose type, provided the fuses or circuit breakers are for the protection of cir- cuits or feeders supplying lamps in fixed positions only. A set of fuses is construed to mean a group containing as many fuses as are required to perform a single protective function in a circuit. For ex- ample, a group of 3 fuses protecting an ungrounded three-phase circuit, and a single fuse protecting the ungrounded conductor of an identified two-wire single-phase circuit, would each be considered as a set of fuses. Fuses con- forming to Section 501-6(b-3) need not be included in counting the 10 sets of fuses permitted in general purpose enclosures. 501-7. Control Transformers and Resistors. Transformers, impedance coils and resistors used as or in conjunction with control equipment for motors,generators and appliances shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, transform- ers, impedance coils and resistors, together with any switching mech- anism associated with them, shall be provided with enclosures approved for Class I locations (explosion-proof). (b) Class I, Division 2. In Class I, Division 2 locations, control transformers and resistors shall conform to the following: (1) Switching Mechanisms. Switching mechanisms used in con- junction with transformers, impedance coils and resistors shall con- form to Section 501-6(b). (2) Coils and Windings. Enclosures for windings of transformers, solenoids or impedance coils may be of the general purpose types. (3) Resistors. Resistors shall be provided with enclosures and the assembly shall be approved for Class I locations, unless resistance is nonvariable and maximum operating temperature, in degrees Centi- grade, will not exceed eighty per cent (80%) of the ignition tempera- 70-270 NATIONAL ELECTRICAL CODE tura of the gas or vapor involved as determined by ASTM test proce- dure (Designation D 286-30). 501-8. Motors and Generators. Motors and generators shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, motors, generators and other rotating electrical machinery shall be (1) ap- proved for Class I locations (explosion-proof), or (2) of the totally enclosed type supplied with positive-pressure ventilation from a source of clean air With discharge to a safe area, so arranged to prevent ener- gizing of the machine until ventilation has been established and the enclosure has been purged with at least ten (10) volumes of air, and also arranged to automatically de-energize the equipment when the air supply fails, or (3) of the totally enclosed inert-gas-filled type sup- plied with a suitable reliable source of inert gas for pressuring the en- closure, with devices provided to insure a positive pressure in the en- closure and arranged to automatically de-energize the equipment when the gas supply fails. Totally enclosed motors of types (2) or (3) shall have no external surface with an operating temperature in degrees Centigrade in excess of eighty per cent (80%) of the ignition tempera- ture of the gas or vapor involved, as determined by ASTM test proce- dure (Designation: D-286-30). Appropriate devices shall also be pro- vided to detect any increase in temperature of the motor beyond design limits and automatically de-energize the equipment. Auxiliary equip- ment shall be of a type approved for the location in which it is in- stalled. (b) Class I, Division 2. In Class I, Division 2 locations, motors, generators and other rotating electrical machinery in which are em- ployed sliding contacts, centrifugal or other types of switching mech- anism (including motor overcurrent devices), or integral resistance de- vices,either while starting or while running, shall be approved for Class I locations (explosion-proof), unless such sliding contacts, switching mechanisms and resistance devices are provided with enclosures ap- proved for such locations. This rule does not prohibit installation of open or nonexplosion-proof enclosed motors, such as squirrel cage induction motors, without brushes. switching mechanism,etc.,in Class I,Division 2 locations. 501-9. Lighting Fixtures. Lamps shall be installed in fixtures which shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, lighting fix- tures shall conform to the following: (1) Approved Fixtures. Each fixture shall be approved as a com- plete assembly for locations of this class, and shall be clearly marked to indicate the maximum wattage of lamps for which it is approved. Fixtures intended for portable use shall be specifically approved as a complete assembly for that use. (2) Physical Damage. Each fixture shall be protected against physical damage by a suitable guard or by location. (3) Pendant Fixtures. Pendant fixtures shall be suspended by and supplied through threaded rigid conduit stems and threaded joints ARTICLE 501—CLASS I INSTALLATIONS 70-271 shall be provided with set-screws or other effective means to prevent loosening. For stems longer than 12 inches, permanent and effective bracing against lateral displacement shall be provided at a level not more than 12 inches above the lower end of the stem, or flexibility in the form of a fitting or flexible connector approved for the purpose and for the location shall be provided not more than 12 inches from the point of attachment to the supporting box or fitting. (4) Supports. Boxes, box assemblies or fittings used for the sup- port of lighting fixtures shall be approved for the purpose and for Class I locations. (b) Class I, Division 2. In Class I, Division 2 locations, lighting fix- tures shall conform to the following: (1) Portable Lamps. Portable lamps shall conform to Section 501-9(a-1). (2) Fixed Lighting. Lighting fixtures for fixed lighting shall be protected from physical damage by suitable guards or by location. Where there is danger that falling sparks or hot metal from lamps or fixtures might ignite localized concentrations of flammable vapors or gases, suitable enclosures or other effective protective means shall be provided. Where lamps are of a size or type which may, under normal operating conditions, reach surface temperatures exceeding eighty per cent (80%) of the ignition temperature in degrees Centigrade of the gas or vapor involved, as determined by ASTM test procedure (Des- ignation D 286-30),fixtures shall conform to Section 501-9(a-1). (3) Pendant Fixtures. Pendant fixtures shall be suspended by threaded rigid conduit stems or by other approved means. For rigid stems longer than 12 inches, permanent and effective bracing against lateral displacement shall be provided at a level not more than 12 inches above the lower 'end of the stem, or flexibility in the form of a fitting or flexible connector approved for the purpose shall be provided not more than 12 inches from the point of attachment to the supporting box or fitting. (4) Supports. Boxes, box assemblies, or fittings used for the sup- port of lighting fixtures shall be approved for the purpose. (5) Switches. Switches which are a part of an assembled fixture or of an individual lampholder shall conform to the requirements of Section 501-6(b-1). (6) Starting Equipment. Starting and control equipment for mer- cury-vapor and fluorescent lamps shall conform to the requirements of Section 501-7(b). 501-10. Utilization Equipment, Fixed and Portable. Utilization equip- ment,fixed and portable,shall conform to the following: (a) Class I, Division 1. In Class I, Division 1 locations, utilization equipment, including electrically-heated and motor-driven equipment shall be approved for Class I locations. (b) Class I, Division 2. In Class I, Division 2 locations, utilization equipment,fixed and portable, shall conform to the following: 70-272 NATIONAL ELECTRICAL CODE (1) Heaters. Electrically heated utilization equipment shall be approved for Class I locations. (2) Motors. Motors of motor-driven utilization equipment shall conform to Section 501-8(b). (3) Switches, Circuit Breakers, and Fuses. Switches, circuit break- ers and fuses shall conform to Section 501-6(b). 501-11. Flexible Cords, Class I, Divisions 1 and 2. A flexible cord may be used only for connection between a portable lamp or other portable utilization equipment and the fixed portion of its supply cir- cuit and where used shall (1) be of a type approved for extra hard usage, (2) contain, in addition to the conductors of the circuit, a grounding conductor conforming to Section 400-13, (3) be connected to terminals or to supply conductors in an approved manner, (4) be supported by clamps or by other suitable means in such a manner that there will be no tension on the terminal connections, and (5) suitable seals shall be provided where the flexible cord enters boxes, fittings or enclosures of explosion-proof type. Refer to Section 501-13 when flexible cords are exposed to liquids having a deleterious effect on the conductor insulation. 501-12. Receptacles and Attachment Plugs, Class I, Divisions 1 and 2. Receptacles and attachment plugs shall be of the type providing for connection to the grounding conductor of the flexible cord, and shall be approved for Class I locations, except as provided in Section 501-3(b)(6). 501-13. Conductor Insulation Class I, Divisions 1 and 2. Where con- densed vapors or liquids may collect on or come in contact with the in- sulation on conductors, such insulation shall be of a type approved for use under such conditions or the insulation shall be protected by a sheath of lead or by other approved means. 501-14. Signal, Alarm, Remote-control and Communication Systems. Signal, alarm, remote-control and communication systems shall con- form to the following: (a) Class I, Division 1. In Class I, Division 1 locations, all appa- ratus and equipment of signalling, alarm, remote-control and com- munication systems, irrespective of voltage, shall be approved for Class I locations, and all wiring shall conform to Sections 501-4(a) and 501-5(a and c). (b) Class I, Division 2. In Class I, Division 2 locations, signal, alarm, remote-control and communication systems shall conform to the following: (1) Contacts. Switches and circuit breakers, and make and break contacts of push buttons, relays, and alarm bells or horns, shall have enclosures approved for Class I locations, unless general purpose en- closures are provided and current interrupting contacts are (1) im- mersed in oil, or (2) enclosed within a chamber hermetically sealed against the entrance of gases or vapors, or (3) in circuits which under normal conditions do not release sufficient energy to ignite a specific hazardous atmospheric mixture. ARTICLE 501—CLASS I INSTALLATIONS 70-273 (2) Resistors and Similar Equipment. Resistors, resistance de- vices, thermionic tubes and rectifiers shall conform to Section 501-3 (b-2). (3) Protectors. Enclosures which may be of general purpose type shall be provided for lightning protective devices and for fuses. (4) All wiring shall conform to Section 501-4.(b) and 501-5.(b) and (c). 501-15. Live Parts, Class I, Divisions 1 and 2. There shall be no ex- posed live parts. 501-16. Grounding, Class I, Divisions 1 and 2. Wiring and equip- ment shall be grounded in conformity with the following: (a) Exposed Parts. The exposed noncurrent-carrying metal parts of equipment such as the frames or metal exteriors of motors, fixed or portable lamps or other utilization equipment, lighting fixtures, cabi- nets, cases, and conduit, shall be grounded as specified in Article 250 of this Code. (b) Bonding. The locknut-bushing and double-locknut types of con- tacts shall not be depended upon for bonding purposes, but bonding jumpers with proper fittings or other approved means shall be used.Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, etc. between hazardous areas and the point of grounding for service equipment. Where flexible conduit is used as permitted in Section 501-4(b), bonding jumpers with proper fittings shall be pro- vided around such conduit. (c) Lightning Protection. Each ungrounded service conductor of a wiring system in a Class I location, when supplied from an overhead line in an area where lightning disturbances are prevalent, shall be pro- tected by a lightning protective device of proper type. Lightning pro- tective devices shall be connected to the service conductors on the sup- ply side of the service disconnecting means, and shall be bonded to the raceway system at the service entrance. Also refer to Section 502-3. (d) Grounded Service Conductor Bonded to Raceway. Wiring in a Class I location, when supplied from a grounded alternating current supply system in which a grounded conductor is a part of the service, shall have the grounded service conductor bonded to the raceway sys- tem and to the grounding conductor for the raceway system. The bond- ing connection to the grounded service conductor shall be made on the supply side of the service disconnecting means. (e) Transformer Ground Bonded to Raceway. Wiring in a Class I location, when supplied from a grounded alternating current supply system in which no grounded conductor is a part of the service, shall be provided with a metallic connection between the supply system ground and the raceway system at the service entrance. The metallic connection shall have an ampacity not less than 1/5 that of the service conductors, and shall in no case be smaller than No. 10 when of soft copper,or No. 12 when of medium or hard-drawn copper. 70-274 NATIONAL ELECTRICAL CODE (f) Multiple Grounds. Where, in the application of Section 250-21, it is necessary to abandon one or more grounding connections to avoid objectionable passage of current over the grounding conductors, the connection required in Section 501-16(d and e) shall not be abandoned while any other grounding connection remains connected to the supply system. ARTICLE 502—CLASS II INSTALLATIONS— HAZARDOUS LOCATIONS 502-1. General. The general rules of this Code shall apply to the in- stallation of electrical wiring and apparatus in locations classified as Class II under Section 500-5 except as modified by this Article. "Dust-ignition-proof," as used in this Article, shall mean enclosed in a manner which will exclude ignitible amounts of dusts or amounts which might affect performance or rating and which, when installation and protection are in conformahce with this Code, will not permit arcs, sparks or heat otherwise generated or liberated inside of the enclosure, to cause ignition of exterior accumulations or atmospheric suspensions of a specified dust on or in the vicinity of the enclosure. Equipment installed in Class II locations shall be able to function at full rating without developing surface temperatures high enough to cause excessive dehydration or gradual carbonization of any organic dust deposits that may occur. Dust which is carbonized or is excessively dry is highly susceptible to spontaneous ignition. In general, maximum surface temperatures under actual operating conditions shall not exceed 165°C. (329°F.) for equipment which is not subject to overloading, and 120°C. (248°F.) for equipment such as motors, power transform- ers,etc.,which may be overloaded. Equipment and wiring of the type defined in Article 100 as explosion- proof is not required in Class II locations, and may not be acceptable unless approved for such locations. 502-2. Transformers and Capacitors. The installation of transformers and capacitors shall conform to the following: (a) Class II, Division 1. In Class II, Division 1 locations, transform- ers and capacitors shall conform to the following: (1) Containing a Liquid that Will Burn. Transformers and ca- pacitors containing a liquid that will burn shall be installed only in ap- proved vaults conforming to Sections 450-41 to 450-48 inclusive, and in addition (1) door or other openings communicating with the haz- ardous area shall have self-closing fire doors on both sides of the wall, and the doors shall be carefully fitted and provided with suitable seals (such as weather stripping) to minimize the entrance of dust into the vault, (2) vent openings and ducts shall communicate only with the outside air, and (3) suitable pressure-relief openings communicating with the outside air shall be provided. ARTICLE 502—CLASS II INSTALLATIONS 70-275 (2) Not Containing a Liquid that Will Burn. Transformers and capacitors which do not contain a liquid that will burn shall (1) be installed in vaults conforming to Sections 450-41 to 450-48 inclusive, or (2) be approved as a complete assembly including terminal connec- tions for Class II locations. (3) Metal Dusts. No transformer or capacitor shall be installed in a location where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be present. (b) Class II, Division 2. In Class II, Division 2 locations, transform- ers and capacitors shall conform to the following: (1) Containing a Liquid that Will Burn. Transformers and capac- itors containing a liquid that will burn shall be installed in vaults con- forming to Sections 450-41 to 450-48 inclusive. (2) Containing Askarel. Transformers containing askarel and rated in excess of 25 kva shall (1) be provided with pressure-relief vents, (2) be provided with means for absorbing any gases generated by arcing inside the case, or the pressure-relief vents shall be connected to a chimney or flue which will carry such gases outside the building and (3) have an air space of not less than 6 inches between the trans- former cases and any adjacent combustible material. (3) Dry-Type Transformers. Dry-type transformers shall be in- stalled in vaults or shall (1) have their windings and terminal connec- tions enclosed in tight metal housings without ventilating or other openings,and (2)operate at voltages not exceeding 600 volts. 502-3. Surge Protection, Class II, Divisions 1 and 2. In geographical locations where lightning disturbances are prevalent, wiring systems in Class II locations shall, when supplied from overhead lines, be suitably protected against high-voltage surges. This protection shall include suitable lightning protective devices, interconnection of all grounds, and surge-protective capacitors. Interconnection of all grounds shall include grounds for primary and secondary lightning protective devices, secondary system grounds if any, and grounds of conduit and equipment of the interior wiring sys- tem. For ungrounded secondary systems, secondary lightning protec- tive devices may be provided both at the service and at the point where the secondary system receives its supply, and the intervening second- ary conductors may be accepted as the metallic connection between the secondary protective devices, provided grounds for the primary and secondary devices are metallically interconnected at the supply end of the secondary system and the secondary devices are grounded to the raceway system at the load end of the secondary system. Surge protective capacitors shall be of a type especially designed for the duty, shall be connected to each ungrounded service conductor, and shall be grounded to the interior conduit system. Capacitors shall be protected by 30-ampere fuses of suitable type and voltage rating, or by automatic circuit breakers of suitable type and rating and shall be connected to the supply conductors on the supply side of the service dis- connecting means. 70-276 NATIONAL ELECTRICAL CODE 502-4. Wiring Methods. Wiring methods shall conform to the fol- lowing: (a) Class II, Division 1. In Class II, Division 1 locations, threaded rigid metal conduit or Type MI cable with termination fittings approved for the location shall be the wiring method employed. Type MI cable shall be installed and supported in a manner to avoid tensile stress at the termination fittings. (1) Fittings and Boxes. Fittings and boxes shall be provided with threaded bosses for connection to conduit or cable terminations, shall have close fitting covers, and shall have no openings (such as holes for attachment screws) through which dust might enter, or through which sparks or burning material might escape. Fittings and boxes in which taps, joints or terminal connections are made, or which are used in lo- cations where dusts are of an electrically conducting nature shall be dust-ignition-proof and approved for Class II locations. (2) Flexible Connections. Where necessary to employ flexible connections, dust-tight flexible connectors, flexible metal conduit with approved fittings, or flexible cord approved for extra-hard usage and provided with bushed fittings shall be used, except that where dusts are of an electrically conducting nature, flexible metal conduit shall not be used, and flexible cords shall be provided with dust-tight seals at both ends. An additional conductor for grounding shall be provided in the flexible cord unless other acceptable means of grounding is provided. Where flexible connections are subject to oil or other corrosive condi- tions, the insulation of the conductors shall be of a type approved for the condition or shall be protected by means of a suitable sheath. (b) Class II, Division 2. In Class II, Division 2 locations, rigid metal conduit,electrical metallic tubing, or Types MI, MC or ALS cable with approved termination fittings or dusttight wireways shall be the wiring method employed. (1) Wireways, and Fittings and Boxes. Wireways, and fittings and boxes in which taps, joints or terminal connections are made, shall be designed to minimize the entrance of dust, and (1) shall be provided with telescoping or close fitting covers, or other effective means to pre- vent the escape of sparks or burning material, and (2) shall have no openings (such as holes for attachment screws) through which, after installation, sparks or burning material might escape, or through which adjacent combustible material might be ignited. (2) Flexible Connections. Where flexible connections are neces- sary the provisions of Section 502-4(a-2) shall apply. 502-5. Sealing, Class II, Divisions 1 and 2. Where a raceway provides communication between an enclosure which is required to be dust- ignition-proof and one which is not, suitable means shall be provided to prevent the entrance of dust into the dust-ignition-proof enclosure through the raceway. This means may be (1) a permanent and effec- tive seal, (2) a horizontal section not less than 10 feet long in the race- way, or (3) a vertical section of raceway not less than 5 feet long and extending downward from the dust-ignition-proof enclosure. Sealing fittings shall be accessible. ARTICLE 502—CLASS II INSTALLATIONS 70_277 502-6. Switches, Circuit Breakers, Motor Controllers, and Fuses. Switches, circuit breakers, motor controllers and fuses shall conform to the following: (a) Class II, Division 1. In Class II, Division 1 locations, switches, circuit breakers, motor controllers and fuses shall conform to the fol- lowing: (1) Type Required. Switches, circuit breakers, motor controllers and fuses, including push buttons, relays and similar devices, which are intended to interrupt current in the normal performance of the func- tion for which they are installed, or which are installed where dusts of an electrically conducting nature may be present, shall be provided with dust-ignition-proof enclosures which, together with the enclosed apparatus in each case, shall be approved as a complete assembly for Class II locations. This includes service and branch circuit fuses, switches and circuit break- ers, motor controllers (including push buttons, pilot switches, relays, and motor overload protective devices), and switches, fuses and circuit breakers for the control and protection of lighting and appliance circuits. (2) Isolating Switches. Disconnecting and isolating switches con- taining no fuses and not intended to interrupt current, and which are not installed where dusts may be of an electrically conducting nature, shall be provided with tight metal enclosures which shall be designed to minimize the entrance of dust, and which shall (1) be equipped with telescoping or close fitting covers, or with other effective means to pre- vent the escape of sparks or burning material, and (2) have no openings (such as holes for attachment screws) through which, after installation, sparks or burning material might escape, or through which exterior accumulations of dust or adjacent combustible material might be ignited. (3) Metal Dusts. In locations where dust from magnesium, alu- minum, aluminum bronze powders, or other metals of similarly haz- ardous characteristics may be present, fuses, switches, motor control- lers and circuit breakers shall have enclosures specifically approved for such locations. (b) Class II, Division 2. In Class II, Division 2 locations, enclosures for fuses, switches, circuit breakers and motor controllers including push buttons, relays and similar devices, shall conform to the require- ments of Section 502-6(a-2). 502-7. Control Transformers and Resistors. Transformers, solenoids, impedance coils and resistors used as or in conjunction with control equipment for motors, generators and appliances shall conform to the following: (a) Class II, Division 1. In Class II, Division 1 locations, control transformers, solenoids, impedance coils and resistors, and any over- current devices or switching mechanisms associated with them shall have dust-ignition-proof enclosures approved for Class II locations. No control transformer, impedance coil or resistor shall be installed in a location where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be 70-278 NATIONAL ELECTRICAL CODE present unless provided with an enclosure specifically approved for such locations. (b) Class II, Division 2. In Class II, Division 2 locations, transform- ers and resistors shall conform to the following: (1) Switching Mechanisms. Switching mechanisms (including overcurrent devices) associated with control transformers, solenoids, I impedance coils and resistors, shall be provided with enclosures con- forming to Section 502-6(a-2). (2) Coils and Winding. Where not located in the same enclosure with switching mechanisms, control transformers, solenoids and im- pedance coils shall be provided with tight metal housings without ventilating openings. (3) Resistors. Resitors and resistance devices shall have dust- ignition-proof enclosures approved for Class II locations, except that where the maximum normal operating temperature of the resistor will not exceed 120°C. (248°F.) nonadjustable resistors and resistors which are part of an automatically timed starting sequence may have enclos- ures conforming to Section 502-7(b-2). 502-8. Motors and Generators. Motors and generators shall conform to the following: (a) Class II, Division 1. In Class II, Division 1 locations, motors, generators and other rotating electrical machinery should be dust-igni- tion-proof or totally enclosed pipe ventilated and shall be approved for Class II locations. (b) Class II, Division 2. Motors, generators and other rotating elec- trical machinery shall be dust-ignition-proof or totally enclosed pipe ventilated. Exception:If the authority having jurisdiction believes accumulations of non-conducting, nonabrasive dust will be moderate, and if machines can be easily reached for routine cleaning and maintenance, the follow- ing may be installed: Standard open-type machines without sliding contacts, centrifugal or other types of switching mechanism (including motor overcurrent de- vices) or integral resistance devices. Standard open-type machines with such contacts, switching mecha- nisms or resistance devices enclosed within tight metal housings with- out ventilating or other openings. Self-cleaning textile motors of the squirrel-cage type. 502-9. Ventilating Piping. Vent pipes for motors, generators or other rotating electrical machinery, or for enclosures for electrical apparatus or equipment, shall be of metal not lighter than No. 24 USS gage, or of equally substantial noncombustible material, and shall (1) lead di- rectly to a source of clean air outside of buildings, (2) be screened at the outer ends to prevent the entrance of small animals or birds, (3) be protected against physical damage and against rusting or other cor- rosive influences. In addition, vent pipes shall conform to the follow- ing: ARTICLE 502—CLASS II INSTALLATIONS 70-479 (a) Class II, Division 1. In Class II, Division 1 locations, vent pipes, including their connections to motors or to the dust-ignition-proof en- closures for other equipment or apparatus, shall be dust-tight through- out their length. For metal pipes, seams and joints shall be (1) riveted (or bolted) and soldered, (2) welded, or (3) rendered dust-tight by some other equally effective means. (b) Class II, Division 2. In Class II, Division 2 locations, vent pipes and their connections shall be sufficiently tight to prevent the entrance of appreciable quantities of dust into the ventilated equipment or en- closure, and to prevent the escape of sparks, flame or burning material which might ignite dust accumulations or combustible material in the vicinity. For metal pipes, lock seams and riveted or welded joints may be used, and tight-fitting slip joints may be used where some flexibility is necessary as at connections to motors. 502-10. Utilization Equipment, Fixed and Portable. Utilization equip- ment,fixed and portable, shall conform to the following: (a) Class II, Division 1. In Class II, Division 1 locations, utiliza- tion equipment, including electrically heated and motor-driven equip- - ment, shall be dust-ignition-proof approved for Class II locations. Where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be present, such equipment shall be specifically approved for such locations. (b) Class II, Division 2. In Class II, Division 2, locations, utilization equipment,fixed and portable,shall conform to the following: (1) Heaters. Electrically heated utilization equipment shall be dust-ignition-proof approved for Class II locations. (2) Motors. Motors of motor-driven utilization equipment shall conform to Section 502-8(b). (3) Switches, Circuit Breakers and Fuses. Enclosures for switches, circuit breakers,and fuses shall conform to Section 502-6(a-2). (4) Transformers, Impedance Coils and Resistors. Transformers, solenoids, impedance coils and resistors shall conform to Section 502-7(b). 502-11. Lighting Fixtures. Lamps shall be installed in fixtures which shall conform to the following: (a) Class II, Division 1. In Class II, Division 1 locations, lighting fixtures for fixed and portable lighting shall conform to the following: (1) Approved Fixtures. Each fixture shall be dust-ignition-proof and approved for Class II locations, and shall be clearly marked to in- dicate the maximum wattage of the lamp for which it is approved. In locations where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be present, fixtures for fixed or portable lighting, and all auxiliary equip- ment,shall be specifically approved for such locations. (2) Physical Damage. Each fixture shall be protected against physical damage by a suitable guard or by location. 70-280 NATIONAL ELECTRICAL CODE (3) Pendant Fixtures. Pendant fixtures shall be suspended by threaded rigid conduit stems or chains with approved fittings, or by other approved means. For rigid stems longer than 12 inches perma- nent and effective bracing against lateral displacement shall be provided at a level not more than 12 inches above the lower end of the stem, or flexibility in the form of a fitting or a flexible connector approved for the purpose and for the location shall be provided not more than 12 inches from the point of attachment to the supporting box or fitting. Threaded joints shall be provided with set-screws or other effective means to prevent loosening. Where wiring between an outlet box or fitting and a pendant fixture is not enclosed in conduit, flexible cord ap- proved for hard usage shall be used, and suitable seals shall be pro- vided where the cord enters the fixture and the outlet box or fitting. Flexible cord shall not serve as the supporting means for a fixture. (4) Supports. Boxes, box assemblies or fittings used for the sup- port of lighting fixtures shall be approved for the purpose and for Class II locations. (b) Class II, Division 2. In Class II, Division 2 locations, lighting fixtures shall conform to the following: (1) Portable Lamps. Portable lamps shall be dust-ignition-proof and approved for Class II locations. They shall be clearly marked to indicate the maximum wattage of lamps for which they are approved. (2) Fixed Lighting. Lighting fixtures for fixed lighting, when not of a type approved for Class II locations, shall provide enclosures for lamps and lampholders which shall be designed to minimize the de- posit of dust on lamps and to prevent the escape of sparks,burning ma- terial or hot metal. Each fixture shall be clearly marked to indicate the maximum wattage of lamp which may be used without exceeding a maximum exposed surface temperature of 165°C. (329°F.) under nor- mal conditions of use. (3) Physical Damage. Lighting fixtures for fixed lighting shall be protected from physical damage by suitable guards or by location. (4) Pendant Fixtures. Pendant fixtures shall be suspended by threaded rigid conduit stems or chains with approved fittings, or by other approved means. For rigid stems longer than 12 inches perma- nent and effective bracing against lateral displacement shall be pro- vided at a level not more than 12 inches above the lower end of the stem, or flexibility in the form of a fitting or a flexible connector ap- proved for the purpose shall be provided not more than 12 inches from the point of attachment to the supporting box or fitting. When wiring between an outlet box or fitting and a pendant fixture is not enclosed in conduit, flexible cord approved for hard usage shall be used. Flexi- ble cord shall not serve as the supporting means for a fixture. (5) Supports. Boxes, box assemblies and fittings used for the sup- port of lighting fixtures shall be approved for that purpose. (6) Electric Discharge Lamps. Starting and control equipment for mercury vapor and fluorescent lamps shall conform to the requirement of Section 502-7(b). ARTICLE 502—CLASS II INSTALLATIONS 70-281 502-12. Flexible Cords, Class II, Divisions 1 and 2. Flexible cords used in Class II locations shall (1) be of a type approved for extra hard usage, (2) contain, in addition to the conductors of the circuit, a grounding conductor conforming to Section 400-13, (3) be connected to terminals or to supply conductors in an approved manner, (4) be supported by clamps or by other suitable means in such a manner that there will be no tension on the terminal connections, and (5) be pro- vided with suitable seals to prevent the entrance of dust where the flex- ible cord enters boxes or fittings which are required to be dust-ignition- proof. 502-13. Receptacles and Attachment Plugs. (a) Class II, Division 1. In Class II, Division 1 locations, recepta- cles and attachment plugs shall be of the type providing for connection to the grounding conductor of the flexible cord, and shall be dust-igni- tion-proof approved for Class II locations. (b) Class II, Division 2. In Class II, Division 2 locations, receptacles and attachment plugs shall be of the type providing for connection to the grounding conductor of the flexible cord and shall be so designed that connection to the supply circuit cannot be made or broken while live parts are exposed. 502-14. Signal, Alarm, Remote-Control, and Local Loud-Speaker Inter- communication Systems. Signal, alarm, remote-control and local loud- speaker intercommunication systems shall conform to the following: Refer to Article 800 for rules governing the installation of communication circuits as defined in Article 100. (a) Class II, Division 1. In Class II, Division 1 locations, signal, alarm, remote-control and local loud-speaker intercommunication sys- tems shall conform to the following: (1) Wiring Method. Where accidental damage or breakdown of insulation might cause arcs, sparks or high temperatures, rigid metal conduit, electrical metallic tubing, or Type MI cable with approved termination fittings shall be the wiring method employed. For conduit or electrical metallic tubing, the number of conductors shall be limited only by the requirement that the cross-sectional area of all conductors shall not exceed 40 per cent of the area of the raceway. Where limited flexibility is desirable or where exposure to physical damage is not severe,flexible cord approved for extra-hard usage may be used. (2) Contacts. Switches, circuit breakers, relays, contactors and fuses which may interrupt other than voice currents, and current- breaking contacts for bells, horns, howlers, sirens and other devices in which sparks or arcs may be produced, shall be provided with enclos- ures approved for the location, unless current-breaking contacts are immersed in oil, or unless the interruption of current occurs within a chamber sealed against the entrance of dust, in which case enclosures may be of general purpose type. (3) Resistors and Similar Equipment. Resistors, transformers and choke coils which may carry other than voice currents, and rectifiers, thermionic tubes, and other heat generating equipment or apparatus 70-282 NATIONAL ELECTRICAL CODE shall be provided with dust-ignition-proof enclosures approved for Class II locations. (4) Rotating Machinery. Motors, generators and other rotating electrical machinery shall conform to Section 502-8(a). (5) Electrical Conducting Dusts. Where dusts are of an electrically conducting nature, all wiring and equipment shall be approved for Class II locations. (6) Metal Dusts. Where dust from magnesium, aluminum, alumi- num bronze powders, or other metals of similarly hazardous charac- teristics may be present, all apparatus and equipment shall be specifi- cally approved for such conditions. (b) Class II, Division 2. In Class II, Division 2 locations, signal, alarm, remote-control and local loudspeaker intercommunication sys- tems shall conform to the following: (1) Contacts. Enclosures shall conform to Section 502-14(a-2) or contacts shall have tight metal enclosures designed to minimize the entrance of dust, and shall have telescoping or tight fitting covers and no openings through which, after installation, sparks or burning ma- terial might escape. (2) Transformers and Similar Equipment. The windings and terminal connections of transformers and choke coils shall be provided with tight metal enclosures without ventilating openings. (3) Resistors and Similar Equipment. Resistors, resistance de- vices, thermionic tubes, and rectifiers shall conform to Section 502-14 (a-3) except that enclosures for thermionic tubes, nonadjustable re- sistors or rectifiers for which maximum operating temperature will not exceed 120°C. (248°F.) may be of general purpose type. (4) Rotating Machinery. Motors, generators and other rotating electrical machinery shall conform to Section 502-8(b). 502-15. Live Parts, Class II, Divisions 1 and 2. There shall be no ex- posed live parts. 502-16. Grounding, Class II, Divisions 1 and 2. Wiring and equip- ment shall be grounded in conformity with the following: (a) Exposed Parts. The exposed noncurrent-carrying metal parts of equipment such as the frames or metal exteriors of motors, fixed or portable lamps or other utilization equipment, lighting fixtures, cabi- nets, cases, and conduit, shall be grounded as specified in Article 250 of this Code. (b) Bonding. The locknut-bushing and double-locknut types of con- tact shall not be depended upon for bonding purposes, but bonding jumpers with proper fittings, or other approved means shall be used. Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, etc., between hazardous areas and the point of grounding for service equipment. Where flexible conduit is used as per- mitted in Section 502-4, bonding jumpers with proper fittings shall be provided around such conduit. (c) Lightning Protection. Each ungrounded service conductor of a wiring system in a Class II location, when supplied from an un- ARTICLE 503—CLASS III INSTALLATIONS 70-283 grounded overhead electrical supply system in an area where lightning disturbances are prevalent, shall be protected by a lightning protective device of proper type. Lightning protective devices shall be connected to the service conductors on the supply side of the service disconnecting means, and shall be bonded to the raceway system at the service en- trance. (d) Grounded Service Conductor Bonded to Raceway. Wiring in a Class II location, when supplied from a grounded alternating-current supply system in which a grounded conductor is a part of the service, shall have the grounded service conductor bonded to the raceway sys- tem and to the grounding conductor for the raceway system.The bond- ing connection to the grounded service conductor shall be made on the supply side of the service disconnecting means. (e) Transformer Ground Bonded to Raceway. Wiring in a Class II location, where supplied from a grounded alternating-current supply system in which no grounded conductor is a part of the service, shall be provided with a metallic connection between the supply system ground and the raceway system at the service entrance. The metallic connec- tion shall have an ampacity not less than 1/5 that of the service con- - ductors, and shall in no case be smaller than No. 10 when of soft cop- per,or No. 12 when of medium or hard-drawn copper. (f) Multiple Grounds. Where, in the application of Section 250-21, it is necessary to abandon one or more grounding connections to avoid objectionable passage of current over the grounding conductors, the connection required in Section 502-16(d or e) shall not be aban- doned while any other grounding connection remains connected to the supply system. ARTICLE 503—CLASS III INSTALLATIONS— HAZARDOUS LOCATIONS 503-1. General. The general rules of this Code shall apply to the in- stallation of electrical wiring and apparatus in locations classified as Class III under Section 500-6 except as modified by this Article. Equipment installed in Class III locations shall be able to function at full rating without developing surface temperatures high enough to cause excessive dehydration or gradual carbonization of accumulated fibers or flyings. Organic material which is carbonized or is excessively dry is highly susceptible to spontaneous ignition. In general, maximum surface temperatures under operating conditions shall not exceed 165°C. (329°F.) for equipment which is not subject to overloading, and 120°C. (248°F.) for equipment such as motors, power transformers, etc.,which may be overloaded. 503-2. Transformers and Capacitors, Class III, Divisions 1 and 2. Transformers and capacitors shall conform to Section 502-2(b). 503-3. Wiring Methods. Wiring methods shall conform to the fol- lowing: 70-284 NATIONAL ELECTRICAL CODE (a) Class III,Division 1. In Class III,Division 1 locations,rigid metal conduit, or approved Type MI, MC or ALS cables shall be the wiring method employed. (1) Boxes and Fittings. Fittings and boxes in which taps, joints or terminal connections are made shall (1) be provided with telescoping or close fitting covers, or other effective means to prevent the escape of sparks or burning material, and (2) shall have no openings (such as holes for attachment screws) through which, after installation, sparks or burning material might escape, or through which adjacent combusti- ble material might be ignited. (2) Flexible Connections. Where flexible connections are neces- sary the provisions of Section 502-4(a-2) shall apply. (b) Class III, Division 2. In Class III, Division 2 locations, the wiring method shall conform to Section 503-3(a), except that in sec- tions, compartments or areas used solely for storage and containing no machinery, open wiring on insulators may be employed when in- stalled to conform to Article 320, but only on condition that protection as required by Section 320-12 be provided where conductors are not run in roof spaces,and well out of reach of sources of physical damage. 503-4. Switches, Circuit Breakers, Motor Controllers and Fuses, Class III, Divisions 1 and 2. Switches, circuit breakers, motor controllers and fuses, including push buttons, relays and similar devices, shall be provided with tight metal enclosures designed to minimize entrance of fibers and flyings, and which shall (1) be equipped with telescoping or close fitting covers, or with other effective means to prevent escape of sparks or burning material, and (2) have no openings (such as holes for attachment screws) through which, after installation, sparks or burning material might escape, or through which exterior accumulations of fi- bers or flyings or adjacent combustible material might be ignited. 503-5. Control Transformers and Resistors, Class III, Divisions 1 and 2. Transformers, impedance coils and resistors used as or in conjunction with control equipment for motors, generators and appliances, shall • conform to Section 502-7(b), with the exception that, in Class III, Di- vision 1 locations, when these devices are in the same enclosure with switching devices of such control equipment, and are used only for • starting or short time duty, the enclosure shall conform to the require- ments of Section 503-4. 503-6. Motors and Generators. Motors and Generators shall conform to the following: (a) Class III, Division 1. In Class III, Division 1 locations, motors, generators, and other rotating electrical machinery shall be totally enclosed not ventilated, totally enclosed pipe ventilated, or totally en- closed fan-cooled, except that in locations where, in the judgment of the authority having jurisdiction, only moderate accumulations of lint and flyings will be likely to collect on, in, or in the vicinity of a rotating electrical machine, and where such machine is readily accessible for routine cleaning and maintenance, self-cleaning textile motors of the squirrel-cage type, standard open type machines without sliding con- tacts, centrifugal or other types of switching mechanism (including ARTICLE 503—CLASS III INSTALLATIONS 70-285 motor overload devices), or standard open type machines having such contacts, switching mechanisms or resistance devices enclosed within tight metal housings without ventilating or other openings, may be in- stalled. (b) Class Ill, Division 2. In Class III, Division 2 locations, motors, generators, and other rotating electrical machinery shall be totally en- closed not ventilated, totally enclosed pipe ventilated, or totally en- closed fan-cooled. (c) Partially Enclosed Type, Class III, Divisions 1 and 2. Motors, gen- erators or other rotating electrical machinery of the partially enclosed or splash-proof type shall not be installed in Class III locations. 503-7. Ventilating Piping, Class III, Divisions 1 and 2. Vent pipes for motors, generators or other rotating electrical machinery, or for en- closures for electrical apparatus or equipment, shall be of metal not lighter than No. 24 USS gage, or of equally substantial noncombusti- ble material, and shall (1) lead directly to a source of clean air outside of buildings, (2) be screened at the outer ends to prevent the entrance of small animals or birds, (3) be protected against physical damage and against rusting or other corrosive influences, and (4) vent pipes and their connections shall be sufficiently tight to prevent the entrance of appreciable quantities of fibers or flyings into the ventilated equip- ment or enclosure, and to prevent the escape of sparks, flame or burn- ing material which might ignite accumulations of fibers or flyings or combustible material in the vicinity. For metal pipes, lock seams and riveted or welded joints may be used, and tight fitting slip joints may be used where some flexibility is necessary as at connections to motors. 503-8. Utilization Equipment, Fixed and Portable, Class III, Divisions 1 and 2. Utilization equipment shall conform to the following: (a) Heaters. Electrically heated utilization equipment shall be ap- proved for Class III locations. (b) Motors. Motors of motor-driven utilization equipment shall conform to Section 503-6(b).Utilization equipment which may be read- ily moved from one location to another should conform to requirements for the most hazardous location. (c) Switches, Circuit Breakers, Motor Controllers and Fuses. Switches, circuit breakers, motor controllers and fuses shall conform to Section 503-4. 503-9. Lighting Fixtures, Class III, Divisions 1 and 2. Lamps shall be installed in fixtures which shall conform to the following: (a) Fixed Lighting. Lighting fixtures for fixed lighting shall provide enclosures for lamps and lampholders which shall be designed to mini- mize entrance of fibers and flyings, and to prevent the escape of sparks, burning material or hot metal. Each fixture shall be clearly marked to show wattage of lamp which may be used without exceeding a maxi- mum exposed surface temperature of 165°C. (329°F.) under operating conditions of use. (b) Physical Damage. A fixture which may be exposed to physical damage shall be protected by a suitable guard. 70-286 NATIONAL ELECTRICAL CODE (c) Pendant Fixtures. Pendant fixtures shall be suspended by stems of threaded rigid conduit or threaded metal tubing of equivalent thick- ness. For stems longer than 12 inches, permanent and effective bracing against lateral displacement shall be provided at a level not more than 12 inches above the lower end of the stem, or flexibility in the form of a fitting or a flexible connector approved for the purpose shall be pro- vided not more than 12 inches from the point of attachment to the supporting box or fitting. (d) Supports. Boxes, box assemblies or fittings used for the support of lighting fixtures shall be of a type approved for the purpose. (e) Portable Lamps. Portable lamps shall be equipped with handles and protected with substantial guards, and lampholders shall be of un- switched type with no exposed metal parts and without provision for receiving attachment plugs. In all other respects, portable lamps shall conform to Section 503-9(a). 503-10. Flexible Cords, Class III, Divisions 1 and 2. Flexible cords shall conform to Section 502-12. 503-11. Receptacles and Attachment Plugs, Class III, Divisions 1 and 2. Receptacles and attachment plugs shall conform to Section 502-13(b). 503-12. Signal, Alarm, Remote-Control and Local Loud-Speaker Inter- communication Systems, Class III, Divisions 1 and 2. Signal, alarm, re- mote-control and local loudspeaker intercommunication systems shall conform to Section 502-14(a). 503-13. Electric Cranes and Hoists, and Similar Equipment, Class III, Di- visions 1 and 2. Where installed for operation over combustible fibers or accumulations of flyings, traveling cranes and hoists for material handling, traveling cleaners for textile machinery, and similar equip- ment shall conform to the following: (a) Power supply to contact conductors shall be isolated from all other systems and shall be ungrounded, and shall be equipped with an acceptable recording ground detector which will give an alarm and will automatically de-energize the contact conductors in case of a fault to ground, or with an acceptable ground fault indicator which will give a visual and audible alarm, and maintain the alarm as long as power is supplied to the system and the ground fault remains. (b) Contact conductors shall be so located or guarded as to be in- accessible to other than authorized persons, and shall be protected against accidental contact with foreign objects. (c) Current collectors shall be arranged or guarded to confine nor- mal sparking and to prevent escape of sparks or hot particles. To re- duce sparking, two or more separate surfaces of contact shall be pro- vided for each contact conductor. Reliable means shall be provided to keep contact conductors and current collectors free of accumulations of lint or flyings. (d) Control equipment shall conform to Sections 503-4 and 503-5. It is recommended that where the distance of travel permits, current to the crane be supplied through flexible cord approved for extra hard usage and equipped with approved type of reel or takeup device. ARTICLE 511—COMMERCIAL GARAGES 70-287 503-14. Electric Trucks. Electric trucks shall conform to NFPA Stan- dard for the Use, Maintenance and Operation of Industrial Trucks (No. 505). 503-15. Storage-Battery Charging Equipment, Class III, Divisions 1 and 2. Storage-battery charging equipment shall be located in separate rooms built or lined with substantial noncombustible materials so con- structed as to adequately exclude flyings or lint, and shall be well ven- tilated. 503-16. Live Parts, Class III, Divisions 1 and 2. There shall be no ex- posed live parts except as provided in Section 503-13. 503-17. Grounding, Class III, Divisions 1 and 2. Wiring and equip- ment shall be grounded in conformity with Section 502-16. ARTICLE 510—HAZARDOUS LOCATIONS—SPECIFIC 510-1. Scope. The provisions of Articles 511 to 517 inclusive shall apply to occupancies or parts of occupancies which are or may be hazardous because of atmospheric concentrations of hazardous gases or vapors, or because of deposits or accumulations of materials which may be readily ignitible. It is the intent to assist the authority having jurisdic- tion in the classification of areas with respect to hazardous conditions which may or may not require construction and equipment conforming to Articles 501 to 503 inclusive, and to set forth such additional special requirements as are applicable to the specific occupancy. 510-2. General. The general rules of this Code shall apply to the in- stallation of electrical wiring and equipment in occupancies within the scope of Articles 511 to 517 inclusive, except as such rules are modi- fied in those articles. Where unusual conditions exist in a specific oc- cupancy, the authority having jurisdiction shall judge with respect to the application of specific rules. It is recommended that the authority having jurisdiction be familiar with National Fire Protection Association standards applying to occupancies in- cluded within the scope of Articles 511.to 517 inclusive. ARTICLE 511—COMMERCIAL GARAGES, REPAIR AND STORAGE 511-1. Scope. These occupancies shall include locations used for serv- ice and repair operations in connection with self-propelled vehicles (including passenger automobiles, buses, trucks, tractors, etc.) in which volatile flammable liquids or flammable gases are used for fuel or power, and locations in which more than three such vehicles are or may be stored at one time. For further information regarding classification of garages, refer to the NFPA Standard for Garages (No. 88). 70-288 NATIONAL ELECTRICAL CODE 511-2. Hazardous Areas. Classification under Article 500. (a) For each floor at or above grade, the entire area up to a level 18 inches above the floor shall be considered to be a Class I, Division 2 location. (b) For each floor below grade, the entire area up to a level 18 inches above the bottom of outside doors or other openings which are at or above grade level shall be considered to be Class I, Division 2 lo- cation. Where adequate positive-pressure ventilation is provided, the authority having jurisdiction may judge that the hazardous location extends up to a level of only 18 inches above each such floor. (c) Any pit or depression below floor level shall be considered to be a Class I, Division 2 location which shall extend up to said floor level, except that any unventilated pit or depression may be judged by the authority having jurisdiction to be a Class I,Division 1 location. (d) Adjacent areas in which hazardous vapors are not likely to be released such as stock rooms, switchboard rooms and other similar lo- cations, having floors elevated at least 18 inches above adjacent ga- rage floor, or separated therefrom by tight curbs or partitions at least 18 inches high,shall not be classed as hazardous. 511-3. Wiring and Equipment in Hazardous Areas. Within hazardous areas as defined in Section 511-2, wiring and equipment shall conform to applicable provisions of Article 501. 511-4. Sealing. Approved seals conforming to the requirements of Section 501-5 shall be provided, and Section 501-5(b-2) shall apply to horizontal as well as to vertical boundaries of the defined hazardous areas. Raceways embedded in a masonry floor or buried beneath a floor shall be considered to be within the hazardous area above the floor if any connections or extensions lead into or through such area. 511-5. Wiring in Spaces Above Hazardous Areas. (a) All fixed wiring shall be in metallic raceways or shall be Type MI or Type ALS cable. Cellular metal floor raceways may be used only for supplying ceiling outlets or extensions to the area below the floor, but such raceways shall have no connections leading into or through any hazardous area above the floor. No electrical conductor shall be installed in any cell, header or duct which contains a pipe for steam, water,air,gas,drainage,or other service except electrical. (b) For pendants, flexible cord suitable for the type of service and approved for hard usage shall be used. (c) For connection of portable lamps, motors or other utilization equipment, flexible cord suitable for the type of service and approved for extra hard usage shall be used. (d) When a circuit which supplies portables or pendants includes an identified grounded conductor as provided in Article 200, recepta- cles, attachment plugs, connectors, and similar devices shall be of po- larized type, and the identified conductor of the flexible cord shall be connected to the screw shell of any lampholder or to the identified terminal of any utilization equipment supplied. ARTICLE 511—COMMERCIAL GARAGES 70-289 (e) When a pendant is used to supply a portable lamp or utilization equipment, the female portion of a polarized pin-plug connector or equivalent shall be attached to the lower end of the pendant, and the male portion shall be attached to the cord for the portable. The con- nector shall be designed to break apart readily in any position, and shall be suspended at a level not less than that specified in Section 511-2. Attachment plug receptacles in fixed position shall be located above the level specified in Section 511-2. 511-6. Equipment Above Hazardous Areas. (a) Equipment which is less than 12 feet above the floor level, and which may produce arcs, sparks or particles of hot metal, such as cut- outs, switches, charging panels, generators, motors or other equipment (excluding receptacles,lamps and lampholders) having make and break or sliding contacts,shall be of the totally enclosed type or so constructed as to prevent escape of sparks or hot metal particles. (b) Lamps and lampholders for fixed lighting which are located over lanes through which vehicles are commonly driven or which may other- wise be exposed to physical damage, shall be located not less than 12 feet above floor level unless of totally enclosed type or so constructed as to prevent escape of sparks or hot metal particles. (c) Portable lamps shall be equipped with handle, lampholder, hook and substantial guard attached to the lampholder or handle. All ex- terior surfaces which might come in contact with battery terminals, wiring terminals, or other objects shall be of nonconducting material or shall be effectively protected with insulation. Lampholders shall be of unswitched type, and shall not provide means for plug-in of attach- ment plugs. Outer shell shall be of moulded composition or other ma- terial approved for the purpose, and metal-shell, lined lampholders, either of switched or unswitched type, shall not be used. Unless the lamp and its cord are supported or arranged in such a manner that they cannot be used in the hazardous areas classified in Section 511-2, they shall be of a type approved for such hazardous locations. 511-7. Battery-Charging Equipment. Battery chargers and their con- trol equipment, and batteries being charged shall not be located within hazardous areas classified in Section 511-2. Tables, racks, trays, and wiring shall,in addition,conform to the provisions of Article 480. 511-8. Electric Vehicle Charging. (a) Flexible cords used for charging shall be suitable for the type of service and approved for extra hard usage. Their ampacity shall be adequate for the charging current. (b) Connectors shall have a 'ating not less than the ampacity of the cord,and in no case less than 50 amperes. (c) Connectors shall be so designed and installed that they will break apart readily at any position of the charging cable, and live parts shall be guarded from accidental contact. No connector shall be located within a hazardous area defined in Section 511-2. (d) Where plugs are provided for direct connection to vehicles, the point of connection shall not be within a hazardous area as defined in 70-290 NATIONAL ELECTRICAL CODE Section 511-2, and where the cord is suspended from overhead, it shall be so arranged that the lowest point of sag is at least 6 inches above the floor. Where the vehicle is equipped with an approved plug which will readily pull apart, and where an automatic arrangement is provided to pull both cord and plug beyond the range of physical damage, no addi- tional connector is required in the cable or at the outlet. ARTICLE 512—RESIDENTIAL STORAGE GARAGES 512-1. Definition. A residential storage garage is a building or room in which not more than three vehicles of the types described in Section 511-1 are or may be stored, but which will not normally be used for other than minor service or repair operations on such stored vehicles. 512-2. At or Above Grade. Where the lowest floor is at or above adjacent ground or driveway level, and where there is at least one out- side door at or below floor level, the garage area shall not be classed as a hazardous location. 512-3. Below Grade. Where the lowest floor is below adjacent ground or driveway level,the following shall apply: (a) The entire area of the garage or of any enclosed space which in- cludes the garage shall be classified as a Class I, Division 2 location up to a level 18 inches above the garage floor.All electrical equipment and wiring within such hazardous location shall conform to applicable pro- visions of Article 501. (b) Wiring and equipment above the defined hazardous location shall conform to the requirements of this Code for nonhazardous loca- tions. (c) Adjacent areas in which hazardous vapors or gases are not likely to be released, and having floors elevated at least 18 inches above the garage floor, or separated therefrom by tight curbs or partitions at least 18 inches high,shall not be classed as hazardous. ARTICLE 513—AIRCRAFT HANGARS 513-1. Definition. This occupancy shall include locations used for storage or servicing of aircraft in which gasoline, jet fuels, or other volatile flammable liquids, or flammable gases, are used, but shall not include such locations when used exclusively for aircraft which have never contained such liquids or gases, or which have been drained and properly purged. 513-2. Hazardous Areas. Classification under Article 500. (a) Any pit or depression below the level of the hangar floor shall be considered to be a Class I, Division 1 location which shall extend up to said floor level. ARTICLE 513—AIRCRAFT HANGARS 70-291 (b) The entire area of the hangar including any adjacent and com- municating areas not suitably cut off from the hangar shall be consid- ered to be a Class I, Division 2 location up to a level 18 inches above the floor. (c) The area within 5 feet horizontally from aircraft power plants, aircraft fuel tanks or aircraft structures containing fuel shall be con- sidered to be a Class I, Division 2 hazardous location which shall ex- tend upward from the floor to a level 5 feet above the upper surface of wings and of engine enclosures. (d) Adjacent areas in which hazardous vapors are not likely to be released such as stock rooms, electrical control rooms, and other simi- lar locations, should not be classed as hazardous when adequately ven- tilated and when effectively cut off from the hangar itself by walls or partitions. 513-3. Wiring and Equipment in Hazardous Areas. All fixed and port- able wiring and equipment which is or may be installed or operated within any of the hazardous locations defined in Section 513-2 shall conform to applicable provisions of Article 501. All wiring installed in or under the hangar floor shall conform to the requirements for Class I, Division 1. When such wiring is located in vaults, pits, or ducts, ade- quate drainage shall be provided, and the wiring shall not be placed within the same compartment with any other service except piped com- pressed air. Attachment plugs and receptacles in hazardous locations shall be explosion-proof or shall be so designed that they cannot be energized while the connections are being made or broken. 513-4. Wiring Not Within Hazardous Areas. (a) All fixed wiring in a hangar, but not within a hazardous area as defined in Section 513-2, shall be installed in metallic raceways or shall be Type MI or Type ALS cable, except that wiring in nonhazardous lo- cations as defined in Section 513-2(d) may be of any type recognized in Chapter 3 of this Code. (b) For pendants, flexible cord suitable for the type of service and approved for hard usage shall be used. Each such cord shall include a separate grounding conductor. (c) For portable utilization equipment and lamps, flexible cord suit- able for the type of service and approved for extra hard usage shall be used.Each such cord shall include a separate grounding conductor. (d) Where a circuit which supplies portables or pendants includes an identified grounded conductor as provided in Article 200, recepta- cles, attachment plugs, connectors, and similar devices shall be of po- larized type, and the identified conductor of the flexible cord shall be connected to the screw shell of any lampholder or to the identified terminal of any utilization equipment supplied. Acceptable means shall be provided for maintaining continuity of the grounding conductor between the fixed raceway system and the noncurrent-carrying metallic portions of pendant fixtures, portable lamps, and portable utilization equipment. 70-292 NATIONAL ELECTRICAL CODE 513-5. Equipment not Within Hazardous Areas. (a) In locations other than those described in Section 513-2, equip- ment which is less than 10 feet above wings and engine enclosures of aircraft and which may produce arcs, sparks or particles of hot metal, such as lamps and lampholders for fixed lighting, cutouts, switches, re- ceptacles, charging panels, generators, motors, or other equipment hav- ing make and break or sliding contacts, shall be of totally enclosed type or so constructed as to prevent escape of sparks or hot metal particles, except that equipment in areas described in Section 513-2(d) may be of general purpose type. (b) Lampholders of metal shell, fiber-lined types shall not be used for fixed incandescent lighting. (c) Portable lamps which are or may be used within a hangar shall be approved for Class I locations. (d) Portable utilization equipment which is or may be used within a hangar shall be of a type suitable for use in Class I, Division 2 loca- tions. 513-6. Stanchions,Rostrums and Docks. (a) Electric wiring, outlets and equipment (including lamps) on or attached to stanchions, rostrums or docks which are located or likely to be located in a hazardous area as defined in Section 513-2(c) shall con- form to the requirements for Class I,Division 2 locations. (b) Where stanchions, rostrums, or docks are not located or likely to be located in a hazardous area as defined in Section 513-2(c),wiring and equipment shall conform to Sections 513-4 and 513-5, except that such wiring and equipment not more than 18 inches above the floor in , any position shall conform to Section 513-6(a). Receptacles and attach- ment plugs shall be of locking type which will not break apart readily. (c) Mobile stanchions with electrical equipment conforming to Sec- tion 513-6(b) shall carry at least one permanently affixed warning sign to read: "WARNING — KEEP 5 FEET CLEAR OF AIRCRAFT ENGINES AND FUEL TANK AREAS." 513-7. Sealing. Approved seals shall be provided in conformance with Section 501-5 and Section 501-5(a-3) and 501-5(b-2) and shall ap- ply to horizontal as well as to vertical boundaries of the defined haz- ardous areas.Raceways embedded in a masonry floor or buried beneath a floor shall be considered to be within the hazardous area above the floor when any connections or extensions lead into or through such area. 513-8. Aircraft Electrical Systems. Aircraft electrical systems should be de-energized when the aircraft is stored in a hangar, and, whenever possible,while the aircraft is undergoing maintenance. 513-9. Aircraft Battery—Charging and Equipment. (a) Aircraft batteries should not be charged when installed in an aircraft located inside or partially inside a hangar. (b) Battery chargers and their control equipment shall not be lo- cated or operated within any of the hazardous areas defined in Section ARTICLE 513—AIRCRAFT HANGARS 70-293 513-2, and should preferably be located in a separate building or in an area such as described in Section 513-2(d). Mobile chargers shall carry at least one permanently affixed warning sign to read: "WARNING— KEEP 5 FEET CLEAR OF AIRCRAFT ENGINES AND FUEL TANK AREAS." Tables, racks, trays, and wiring shall not be located within a hazardous area, and shall, in addition, conform to the provi- sions of Article 480. 513-10. External Power Sources for Energizing Aircraft. (a) Aircraft energizers shall be so designed and mounted that all electrical equipment and fixed wiring will be at least 18 inches above floor level and shall not be operated in a hazardous area as defined in Section 513-2(c). (b) Mobile energizers shall carry at least one permanently affixed warning sign to read: "WARNING — KEEP 5 FEET CLEAR OF AIRCRAFT ENGINES AND FUEL TANK AREAS." (c) Aircraft energizers should be equipped with polarized external power plugs and should have automatic controls to isolate the ground power unit electrically from the aircraft in case excessive voltage is generated by the grounding power unit. (d) Flexible cords for aircraft energizers and ground support equip- ment shall be approved for the type of service and extra hard usage and shall include a ground conductor. 513-11. Mobile Servicing Equipment with Electrical Components. (a) Mobile servicing equipment (such as vacuum cleaners, air com- pressors, air movers, etc.) having electrical wiring and equipment not suitable for Class I, Division 2 locations shall be so designed and mounted that all such fixed wiring and equipment will be at least 18 inches above the floor. Such mobile equipment shall not be operated within the hazardous areas defined in Section 513-2(c) and shall carry at least one permanently affixed warning sign to read: "WARNING — KEEP 5 FEET CLEAR OF AIRCRAFT ENGINES AND FUEL TANK AREAS." (b) Flexible cords for mobile equipment shall be suitable for the type of service and approved for extra hard usage, and shall include a grounding conductor. Attachment plugs and receptacles shall be ap- proved for the location in which they are installed, and shall provide for connection of the grounding conductor to the raceway system. (c) Equipment not of a type suitable for Class I, Division 2 loca- tions should not be operated in areas where maintenance operations likely to release hazardous vapors are in progress. 513-12. Grounding. All metallic raceways, and all noncurrent-carry- ing metallic portions of fixed or portable equipment, regardless of voltage,shall be grounded as provided in Article 250. 70-294 NATIONAL ELECTRICAL CODE ARTICLE 514—GASOLINE DISPENSING AND SERVICE STATIONS 514-1. Definitions. This classification shall include locations where gasoline or other volatile flammable liquids or liquefied flammable gases are transferred to the fuel tanks (including auxiliary fuel tanks) of self- propelled vehicles. Other areas used as lubritoriums, service rooms and repair rooms, and offices, salesrooms, compressor rooms and similar locations shall conform to Articles 510 and 511 with respect to electrical wiring and equipment. Where the authority having jurisdiction can satisfactorily determine that flammable liquids having a flash point below 100°F such as gasoline will not be handled,he may classify such an area as nonhazardous. For further information regarding safeguards for gasoline dispensing and service stations see NFPA Flammable and Combustible Liquids Code (No. 30). 514-2. Hazardous Areas. (a) The space within the dispenser up to 4 feet from its base and the space within 18 inches extending horizontally from the dispenser up to 4 feet from its base shall be considered a Class I, Division 1 location. This classification shall also apply to any space below the dispenser which may contain electrical wiring or equipment. (b) In an outside location, any area (excluding Class I, Division 1, but including buildings not suitably cut off) within 20 feet horizontally from the exterior enclosure of any dispensing pump shall be considered a Class I, Division 2 location which will extend to a level 18 inches above driveway or ground level. (c) In an outside location, any area (excluding Class I, Division 1, but including buildings not suitably cut off) within 10 feet horizontally from any tank fill-pipe shall be considered a Class I, Division 2 loca- tion which shall extend upward to a level 18 inches above driveway ' or ground level. (d) Electrical wiring and equipment, any portion of which is below the surface of areas defined as Class I, Division 1 or Division 2 in 514-2(a), (b), (c) above shall be considered to be within a Class I Division 1 location which shall extend at least to the point of emer- gence above grade. (e) The spherical volume within a 3 foot radius from point of dis- charge of any tank vent-pipe shall be considered a Class I, Division I location and the volume between three foot to five foot radius from point of d,scharge of a vent shall be considered a Class I, Division 2 location. For any vent that does not discharge upward, the cylindrical volume below both the Division 1 and 2 locations extending to the ground shall be considered a Class I, Division 2 location. The hazard- ous area shall not extend beyond an unpierced wall. ARTICLE 515—BULK-STORAGE PLANTS 70-295 (f) In addition to the requirements of Section 514-1 the area within any pit or space below grade in a lubrication room shall be considered a Class I, Division 1 location. The area within the entire lubrication room up to 18 inches above the floor or grade, and the area within 3 feet measured in any direction from the dispensing point of a hand- operated unit dispensing Class I liquids shall be considered a Class I, Division 2 location. 514-3. Wiring and Equipment Within Hazardous Areas. All electrical equipment and wiring within the hazardous areas defined in Section 514-2 shall conform to applicable provisions of Article 501. Exception:Except as permitted in Section 514-8. For special requirements for conductor insulation,see Section 501-13. 514-4. Wiring and Equipment Above Hazardous Areas. Wiring and equipment above hazardous areas defined in Section 514-2 shall con- form to Sections 511-5 and 511-6. 514-5. Circuit Disconnects. Each circuit leading to or through a dis- pensing pump shall be provided with a switch or other acceptable means to disconnect simultaneously from the source of supply all con- ductors of the circuit including the grounded neutral,if any. 514-6. Sealing. (a) An approved seal shall be provided in each conduit run entering or leaving a dispenser or any cavities or enclosures in direct communi- cation therewith. The sealing fitting shall be the first fitting after the conduit emerges from the earth or concrete. (b) Additional seals shall be provided in conformance with Section 501-5 and Sections 501-5(a-3) and 501-5(b-2) shall apply to horizontal as well as to vertical boundaries of the defined hazardous areas. 514-7. Grounding. Metallic portions of dispensing pumps, metallic raceways, and all noncurrent-carrying portions of electrical equipment, regardless of voltage,shall be grounded as provided in Article 250. 514-8. Underground Wiring. Underground wiring shall be installed in rigid metal conduit, or, where buried under not less than 2 feet of earth, may be installed in nonmetallic conduit conforming to the re- quirements of Article 347. Where nonmetallic conduit is used, a grounding conductor shall be included to provide for metallic con- tinuity of the raceway system and for grounding of noncurrent-carry- ing metallic parts of equipment. ARTICLE 515—BULK-STORAGE PLANTS 515-1. Definition. This designation shall include locations where gas- oline or other volatile flammable liquids are stored in tanks having an aggregate capacity of one carload or more, and from which such prod- ucts are distributed (usually by tank truck). 515-2. Hazardous Areas. (a) Pumps,Bleeders,Withdrawal Fittings,Meters and Similar Devices. (1) Adequately ventilated indoor areas containing pumps, bleeders, withdrawal fittings, meters and similar devices which are located in 70-296 NATIONAL ELECTRICAL CODE pipe lines handling flammable liquids under pressure shall be consid- ered as Class I, Division 2 locations within a 5 foot distance extending in all directions from the exterior surface of such devices. The Class I, Division 2 location shall also extend 25 feet horizontally from any sur- face of these devices and extend upward to 3 feet above floor or grade level. See Flammable and Combustible Liquids Code, NFPA No. 30, for dis- cussion of factors influencing adequacy of ventilation required to prevent formation of hazardous vapor-air mixtures. (2) Inadequately ventilated indoor areas containing pumps, bleeders, withdrawal fittings, meters and similar devices which are located in pipe lines handling flammable liquids under pressure shall be consid- ered as Class I, Division 1 locations within a 5 foot distance extending in all directions from the exterior surface of such devices. The Class I, Division 1 location shall also extend 25 feet horizontally from any sur- face of the devices and extend upward to 3 feet above floor or grade level. (3) Outdoor areas containing pumps, bleeders, withdrawal fittings, meters and similar devices which are located in pipe lines handling flammable liquids under pressure shall be considered as Class I, Divi- sion 2 locations within a 3 foot distance extending in all directions from the exterior surface of such devices. The Class I, Division 2 location shall also extend up to 18 inches above grade level within 10 feet hori- zontally from any surface of the devices. (b) Transfer of Flammable Liquids to Individual Containers. (1) In outdoor areas or where positive and reliable mechanical ven- tilation is provided in indoor areas in which flammable liquids are transferred to individual containers, such areas shall be considered to be a Class I, Division 1 location within 3 feet of the vent or fill opening ' extending in all directions and a Class I, Division 2 location within the area extending between a 3 foot and 5 foot radius from the vent or fill opening extending in all directions, and including the area within a horizontal radius of 10 feet from the vent or fill opening and extending to a height of 18 inches above floor or grade levels. See Flammable and Combustible Liquids Code, NFPA No. 30, for dis- cussion of factors influencing adequacy and reliability of mechanical venti- lation required to prevent formation of hazardous vapor-air mixtures. (2) When positive and reliable mechanical ventilation is not pro- vided in indoor areas in which flammable liquids are transferred to in- dividual containers, such areas shall be considered to be a Class I, Di- vision 1 location. (c) Loading and Unloading of Tank Vehicles and Tank Cars in Outside Locations. (1) The area extending 3 feet in all directions from the dome when loading through an open dome or from the vent when loading through a closed dome with atmospheric venting shall be considered a Class I, Division 1 location. (2) The area extending between a 3 foot and 5 foot radius from the dome when loading through an open dome or from the vent when ARTICLE 515—BULK-STORAGE PLANTS 70-297 loading through a closed dome with atmospheric venting shall be con- sidered a Class I,Division 2 location. (3) The area extending within 3 feet in all directions from a fixed connection used in bottom loading or unloading, loading through a closed dome with atmospheric venting, or loading through a closed dome with a vapor recovery system, shall be considered a Class I, Di- vision 2 location. In the case of bottom loading or unloading this clas- sification shall also be applied to the area within a 10 foot radius from point of connection and extending 18 inches above grade. In deciding upon extent of hazardous area, consideration should be given to the total area within which loading and unloading operation may occur such as racks,platforms,driveways,etc. (d) Aboveground Tanks. (1) The area above the roof and within the shell of a floating roof type tank shall be considered a Class I,Division 1 location. (2) For all types of aboveground tanks the area within 10 feet from the shell, ends and roof of other than a floating roof shall be considered a Class I, Division 2 location. Where dikes are provided the area inside the dike and extending upward to the top of the dike shall be considered to be a Class I,Division 2 location. (3) The area within 5 feet of a vent opening and extending in all directions shall be considered a Class I,Division 1 location. (4) The area between 5 and 10 feet of a vent opening and extend- ing in all directions shall be considered a Class I,Division 2 location. For underground tanks see Article 514. (e) Pits. (1) Any pit or depression, any part of which lies within a Division 1 or Division 2 location as defined herein, shall be considered a Class I, Division 1 location unless provided with positive and reliable mechan- ical ventilation. (2) Any such areas when provided with positive and reliable me- chanical ventilation shall be considered a Class I,Division 2 location. See Flammable and Combustible Liquids Code, NFPA No. 30, for dis- cussion of factors pertaining to positive and reliable mechanical ventilation required to prevent formulation of hazardous vapor-air mixtures. (3) Any pit or depression not within a Division 1 or Division 2 location as defined herein, but which contains piping, valves or fittings shall be classified as a Class I,Division 2 location. (f) Storage and Repair Garages for Tank Vehicles shall be considered to be Class I, Division 2 locations up to 18 inches above floor or grade level unless in the judgment of the authority enforcing this Code condi- tions warrant more severe classification or a greater extent of the hazardous area. (g) Office Buildings, Boiler Rooms and Other Similar Locations which are outside the limits of hazardous areas as defined herein, and which are not used for handling or storage of volatile flammable liquids or containers for such liquids, shall not be considered to be hazardous lo- cations. 70-298 NATIONAL ELECTRICAL CODE 515-3. Wiring and Equipment Within Hazardous Areas. All electrical wiring and equipment within the hazardous areas defined in Section 515-2 shall conform to applicable provisions of Article 501. Exception:Except as permitted in Section 515-5. 515-4. Wiring and Equipment Above Hazardous Areas. All fixed wiring above hazardous areas shall be in metallic raceways or shall be Type ALS cable. Fixed equipment which may produce arcs, sparks or particles of hot metal, such as lamps and lampholders for fixed light- ing, cutouts, switches, receptacles, motors, or other equipment having make and break or sliding contacts, shall be of totally enclosed type or so constructed as to prevent escape of sparks or hot metal particles. Portable lamps or utilization equipment, and their flexible cords shall conform to the provisions of Article 501 for the class of location above which they are connected or used. 515-5. Underground Wiring. (a) Underground wiring shall be installed in rigid metal conduit, or, where buried under not less than 2 feet of earth, may be installed in nonmetallic conduit or duct, or in the form of cable approved for the purpose.Where cable is used, it shall be enclosed in rigid metal conduit from the point of lowest buried cable level to the point of connection to the aboveground raceway. (b) Conductor insulation shall conform to Section 501-13 of Article 501. (c) Where cable with nonmetallic sheath or nonmetallic conduit is used, an additional grounding conductor shall be included to provide for metallic continuity of the raceway system and for grounding of noncurrent-carrying metallic parts of equipment. 515-6. Sealing. Approved seals shall be provided in conformance with Section 501-5 and Sections 501-5(a-3) and 501-5(b-2) shall apply to horizontal as well as to vertical boundaries of the defined hazardous areas. Buried raceways under defined hazardous areas shall be consid- ered to be within such areas. 515-7. Gasoline Dispensing. Where gasoline dispensing is carried on in conjunction with bulk station operations, applicable provisions of Article 514 shall apply. 515-8. Grounding. All metallic raceways, and all noncurrent-carry- ing metallic portions of electrical equipment shall be grounded as pro- vided in Article 250. ARTICLE 516—FINISHING PROCESSES 516-1. Definition. This Article shall apply to locations where paints, lacquers or other flammable finishes are regularly or frequently applied by spraying, dipping, brushing or by other means, and where volatile flammable solvents or thinners are used or where readily ignitible de- posits or residues from such paints,lacquers or finishes may occur. For further information regarding safeguards for,finishing processes, see the NFPA Standard for Spray Finishing Using Flammable and Combustible ARTICLE 516—FINISHING PROCESSES 70-299 Materials (No. 33) and the NFPA Standard for Dip Tanks Containing Flammable or Combustible Liquids (No.34). 516-2. Hazardous Areas. Classification with respect to flammable va- pors.For deposits and residues,see Section 516-3. (a) The interiors of spray booths and their exhaust ducts, all space within 20 feet horizontally in any direction from spraying operations more extensive than touch-up spraying and not conducted within spray booths, all space within 20 feet horizontally in any direction from dip tanks and their drain boards, and all other spaces where hazardous concentrations of flammable vapors are likely to occur, shall be con- sidered to be Class I,Division 1 locations. (b) All space within 20 feet horizontally in any direction from the open face of a spray booth, and all space within the room but beyond the limits for Class I, Division 1 as defined in Section 516-2(a) for ex- tensive open spraying, for dip tanks and drain boards and for other hazardous operations, shall be considered to be Class I, Division 2 loca- tions unless the authority having jurisdiction judges otherwise. (c) Adjacent areas which are cut off from the defined hazardous areas by tight partitions without communicating openings, and within which hazardous vapors are not likely to be released, shall be classed as nonhazardous unless the authority having jurisdiction judges other- wise. (d) Drying and baking areas provided with positive mechanical ven- tilation adequate to prevent formation of flammable concentrations of vapors, and provided with effective interlocks to de-energize all elec- tric equipment (other than equipment approved for Class I locations) in case the ventilating equipment is inoperative, may be classed as nonhazardous when the authority having jurisdiction so judges. 516-3. Wiring and Equipment in Hazardous Areas. (a) All electrical wiring and equipment within the hazardous areas defined in Section 516-2 shall conform to applicable provisions of Article 501. (b) Unless approved for both readily ignitible deposits and the flam- mable vapor location, no electrical equipment shall be installed or used where it may be subject to hazardous accumulations of readily ignitible deposits or residues, except that wiring in rigid conduit or in threaded boxes or fittings containing no taps, splices or terminal con- nections may be installed in such locations. Type MI cable without fit- tings or boxes may be used. (c) Illumination of readily ignitible areas through panels of glass or other transparent or translucent material is permissible only where: (a) fixed lighting units are used as the source of illumination, (b) the panel effectively isolates the hazardous area from the area in which the light- ing unit is located, (c) the lighting unit is approved for its specific lo- cation, (d.) the panel is of a material or is so protected that breakage will be unlikely and (e) the arrangement is such that normal accumu- lations of hazardous residue on the surface of the panel will not be raised to a dangerous temperature by radiation or conduction from the source of illumination. 70-300 NATIONAL ELECTRICAL CODE (d) Portable electric lamps or other utilization equipment shall not be used within a hazardous area during operation of the finishing proc- ess. When such lamps or utilization equipment are used during cleaning or repairing operations, they shall be of a type approved for Class I locations,and all exposed metal parts shall be effectively grounded. (e) Electrostatic spraying or detearing equipment shall be installed and used only as provided in Section 516-4. For more details,see NFPA No.33. 516-4. Fixed Electrostatic Equipment. Where electrostatic spraying and detearing equipment is installed, such equipment shall be of approved type, and shall conform to the following requirements. (a) No transformers, power packs, control apparatus, or other elec- trical portion of the equipment (except high voltage grids and their connections) shall be installed in any of the hazardous areas defined in Section 516-2 unless of a type approved for the location. (b) High voltage grids or electrodes shall be located in suitable non- combustible booths or enclosures provided with adequate mechanical ventilation, shall be rigidly supported and of substantial construction, and shall be effectively insulated from ground by means of nonporous noncombustible insulators. (c) High voltage leads shall be effectively and permanently supported on suitable insulators, shall be effectively guarded against accidental contact or grounding, and shall be provided with automatic means for discharging any residual charge to ground when the supply voltage is interrupted. (d) Goods being processed shall be supported on conveyors in such a manner that minimum clearance between goods and high voltage grids or conductors cannot be less than twice the sparking distance. A conspicuous sign indicating the sparking distance shall be permanently posted near the equipment. (e) Approved automatic controls which will operate without time de- lay to disconnect the power supply and to signal the operator in case of (a) stoppage of ventilating fans or failure of ventilating equipment from any cause, (b) stoppage of the conveyor carrying goods through the high voltage field, (c) occurrence of a ground or of an imminent ground at any point on the high voltage system, or (d) reduction of clearance below that specified in Section 516-4(d). (f) Adequate fencing, railings or guards which are electrically con- ducting and effectively grounded shall be provided for safe isolation of the process, and signs shall be permanently posted designating the process zone as dangerous because of high voltage. 516-5. Electrostatic Hand Spraying Equipment. Electrostatic hand spray apparatus and devices used in connection with paint spraying operations shall be of approved types and shall conform to the following require- ments: (a) The equipment shall be so designed that the maximum surface temperature of the equipment in the spraying area cannot exceed ARTICLE 516—FINISHING PROCESSES 70-301 150°F. under any condition. The high voltage circuits shall be designed so as to be intrinsically safe and not produce a spark of sufficient in- tensity to ignite any vapor-air mixtures nor result in appreciable shock hazard upon coming in contact with a grounded object. The electro- statically charged exposed elements of the hand gun shall be capable of being energized only by a switch which also controls the paint supply. (b) Transformers, power packs, control apparatus, and all other elec- trical portion of the equipment, with the exception of the hand gun itself and its connections to the power supply, shall be located outside of the hazardous area. (c) The handle of the spraying gun shall be electrically connected to ground by a metallic connection and be so constructed that the opera- tor in normal operating position is in intimate electrical contact with the grounded handle. This requirement is to prevent build-up of a static charge on the operator's body. (d) All electrically conductive objects in the spraying area shall be adequately grounded. This requirement shall apply to paint containers, wash cans and any other objects or devices in the area. The equipment shall carry a prominent permanently installed warning regarding the necessity for this grounding feature. (e) Objects being painted shall be maintained in metallic contact with the conveyor or other grounded support. Hooks shall be regularly cleaned to insure this contact and areas of contact shall be sharp points or knife edges where possible. Points of support of the object shall be concealed from random spray where feasible and where the objects be- ing sprayed are supported from a conveyor, the point of attachment to the conveyor shall be so located as to not collect spray material during normal operation. (f) The spraying operation shall take place within a spray area which is adequately ventilated to remove solvent vapors released from the op- eration. The electrical equipment shall be so interlocked with the ven- tilation of spraying area that the equipment cannot be operated unless the ventilation fans are in operation. 516-6. Wiring and Equipment Above Hazardous Areas. (a) All fixed wiring above hazardous areas shall be in metallic race- ways or shall be Type MI cable or Type ALS cable. Cellular metal floor raceways may be used only for supplying ceiling outlets or ex- tensions to the area below the floor of a hazardous area, but such race- ways shall have no connections leading into or through the hazardous area above the floor unless suitable seals are provided. No electrical conductor shall be installed in any cell, header or duct which contains a pipe for steam, water, air, gas, drainage, or for other service except electrical. (b) Equipment which may produce arcs, sparks or particles of hot metal, such as lamps and lampholders for fixed lighting, cutouts, switches, receptacles, motors or other equipment having make and break or sliding contacts, where installed above a hazardous area or above an area where freshly finished goods are handled, shall be of 70-302 NATIONAL ELECTRICAL CODE totally enclosed type or so constructed as to prevent escape of sparks or hot metal particles. 516-7. Grounding. All metallic raceways, and all noncurrent-carry- ing metallic portions of fixed or portable equipment, regardless of voltage, shall be grounded as provided in Article 250. ARTICLE 517—FLAMMABLE ANESTHETICS 517-1. Definitions. (a) Flammable anesthetics are gases or vapors such as cyclopro- pane, divinyl ether, ethyl chloride, ethyl ether, and ethylene, which may form flammable or explosive mixtures with air, oxygen, or nitrous oxide. (b) For the purpose of this Article, anesthetizing locations are areas in hospitals in which flammable anesthetics are or may be administered to patients. Such locations will include operating rooms, delivery rooms and anesthesia rooms, and will also include any corridors, utility rooms or other areas which are or may be used for administering flammable anesthetics to patients. Recovery rooms are not classed as anesthetizing locations unless used for administering flammable anesthetics. For further information regarding safeguards for hospital operating rooms,see the NFPA Code for the Use of Flammable Anesthetics (No.56). 517-2. Hazardous Areas. (a) Any room or space in which flammable anesthetics or volatile flammable disinfecting agents are stored shall be considered to be a Class I,Division 1 location throughout. (b) In an anesthetizing location as defined in Section 517-1, the en- tire area shall be considered to be a Class I, Division 1 location which shall extend upward to a level 5 feet above the floor. 517-3. Wiring and Equipment Within Hazardous Areas. (a) In hazardous areas as defined in Section 517-2, all fixed wiring and equipment, and all portable equipment, including lamps and other utilization equipment, operating at more than 8 volts between conduc- tors, shall conform to the requirements of Sections 501-1 to 501-15 in- clusive and of Sections 501-16 (a) and (b) for Class I, Division 1 loca- tions, and all such equipment shall be specifically approved for the { hazardous atmospheres involved. (b) Where a box, fitting or enclosure is partially but not entirely within a hazardous area, the hazardous area shall be considered to be extended to include the entire box,fitting or enclosure. (c) Flexible cords which are or may be used in hazardous areas for connection to portable utilization equipment, including lamps operat- ing at more than 8 volts between conductors shall be of a type ap- proved for extra hard usage, shall be of ample length, and shall include an additional conductor for grounding. A storage device for the flexi- ARTICLE 517—FLAMMABLE ANESTHETICS 70-303 ble cord shall be provided, and shall not subject the cord to bending at a radius of less than 3 inches. (d) Receptacles and attachment plugs shall be of the type with pro- vision for connection of the grounding conductor, and where located within a hazardous area, shall be approved for Class I location. Single phase, 125 volt receptacles and attachment plugs shall be of the type recognized in Section 2438 of NFPA Code for the Use of Flammable Anesthetics (No. 56). 517-4. Wiring and Equipment Above Hazardous Areas. (a) Wiring above a hazardous area as defined in Section 517-2(b) shall be installed in metal raceways or shall be Type MI cable or Type ALS cable. (b) Equipment which may produce arcs, sparks or particles of hot metal, such as lamps and lampholders for fixed lighting less than 8 feet above the floor, cutouts, switches, receptacles, generators, motors, or other equipment having make and break or sliding contacts, shall be of totally enclosed type or so constructed as to prevent escape of sparks or hot metal particles. (c) Surgical and other lighting fixtures shall conform to Section 501-9(b), except that surface temperature limitations set forth in Sec- tion 501-9(b-2) shall not apply, and except that integral or pendant switches which are located above and cannot be lowered into the hazardous area need not be explosion-proof. 517-5. Sealing. Approved seals shall be provided in conformance with Section 501-5, and 501-5(a-3) and shall apply to horizontal as well as to vertical boundaries of the defined hazardous areas. Exception. Seals may be located within 18 inches of the point at which a conduit emerges from a wall forming the boundary of an anes- thetizing location if all of the following conditions are met. (1) The junction box switch or receptacle contains a seal-off device between the arcing contacts and the conduit. (2) The conduit is continuous (without coupling or fitting) between the junction box and the sealing fitting within 18 inches of the point where the conduit emerges from the wall. 517-6. Circuits in Anesthetizing Locations. (a) Except as provided in Section 517-6(e), each circuit within or partially within an anesthetizing location as defined in Section 517-1(b) shall be controlled by a switch having a disconnecting pole in each cir- cuit conductor, and shall be supplied from an ungrounded distribution system which shall be isolated from any distribution system supplying areas other than anesthetizing locations. Such isolation may be ob- tained by means of one or more transformers having no electrical connection between primary and secondary windings, by means of mo- tor generator sets,or by means of suitably isolated batteries. (b) Circuits supplying primaries of isolating transformers shall op- erate at not more than 300 volts between conductors, and shall be pro- vided with proper overcurrent protection. Secondary voltage of such 70-304 NATIONAL ELECTRICAL CODE transformers shall not exceed 300 volts between conductors, and all circuits supplied from such secondaries shall be ungrounded and shall have an approved overcurrent device of proper rating in each conduc- tor. Circuits supplied from batteries or from generators or motor-gen- erator sets shall be ungrounded, and shall be protected against over- current in the same manner as transformer secondary circuits. (c) Transformers, motor-generator sets, batteries and battery charg- ers, together with their overcurrent devices shall be installed in non- hazardous locations, and shall conform to the requirements of this Code for such locations. (d) In addition to the usual control and protective devices, the un- grounded system shall be provided with an approved ground contact indicator so arranged that a green signal lamp conspicuously visible to persons in the anesthetizing location remains lighted while the sys- tem is isolated from ground. An adjacent red signal lamp and an audi- ble warning signal shall be energized when any conductor of the system becomes grounded through a resistance or a capacitive reactance of any value up to at least 60,000 ohms. The current through the ground indicator to the ground shall not exceed 2 milliamperes. The indicator and associated signals shall not be installed within a hazardous area. For maintenance tests of the ground indicator, see Section 3422 of the NFPA Code for the Use of Flammable Anesthetics (No.56). (e) Branch circuits supplying only fixed lighting fixtures above the hazardous location other than surgical lighting fixtures or supplying only approved permanently installed X-ray equipment which complies with Section 2434 of the NFPA Code for the Use of Flammable Anes- thetics (No. 56) may be supplied by a conventional grounded system, provided: (a) wiring for grounded and ungrounded circuits does not occupy the same raceways; (b) the lighting fixtures and the X-ray equip- ment (except the enclosed X-ray tube and the metal-enclosed high voltage leads to the tube) are located at least eight feet above the floor or outside the anesthetizing location; and (c) switches for the grounded circuits are located outside of the anesthetizing location. NOTE: Remote control stations for remote control switches may be in- stalled in the anesthetizing location if the remote control circuit is energized from the ungrounded distribution system. 517-7. Low Voltage Equipment and Instruments. (a) Electrical apparatus and equipment used within a hazardous area, and which has exposed current-carrying elements or which is fre- quently in contact with the bodies of persons, shall be designed to op- erate at 8 volts or less unless it is entirely surrounded by a metallic casing or sheath. Power supply shall be ungrounded, and shall be elec- trically isolated from all circuits of higher voltage. (b) Where a low voltage unit receives current from an individual transformer located within a hazardous area, the flexible cord shall con- form to Section 517-3(d), the core and case of the transformer shall be effectively grounded, and the transformer shall be approved for Class I locations. (c) Where low voltage units within a hazardous area are supplied with current from a common source, such as a transformer, motor- ARTICLE 520—THEATERS AND ASSEMBLY HALLS 70-305 generator set, or storage battery, such common source shall be installed in a nonhazardous location. Where located or used within a hazardous area, receptacles and attachment plugs shall be approved for Class I locations. Plugs shall be so designed that they cannot be inserted into receptacles for higher voltage. Flexible cords shall be of adequate length and ampacity, and shall be approved for extra hard usage. An extra conductor for grounding is not required. (d) Low voltage equipment and wiring (including flexible cords) shall be protected from dangerous overcurrents by suitable overcurrent devices or by inherent current limiting characteristics of the source of supply.Overcurrent devices shall not be installed in a hazardous area. (e) Resistance or impedance devices may be used to control low voltage units but shall not be used to limit maximum input voltage. Where a low voltage unit includes a switch or other make and break or sliding contact, or where it includes a resistor or resistance device which may under any operating condition reach a surface temperature exceeding eighty per cent (80%) of the lowest ignition temperature in degrees Centigrade (as determined by ASTM test procedure — Desig- nation D286-30) of the gases or vapors that may be present, the unit shall be of a type approved for Class I locations. 517-8. Other Equipment. (a) Suction, pressure, or insufflation equipment involving electrical elements, and located or used within a hazardous area shall be ap- proved for Class I locations. (b) X-ray equipment installed or operated in an anesthetizing loca- tion as defined in Section 517-1(b) shall be provided with approved means for preventing accumulation of electrostatic charges. All control devices, switches, relays, meters, and transformers shall be totally en- closed, and where installed or operated within a hazardous area, shall be approved for Class I locations. High voltage wiring shall be effec- tively insulated from ground and adequately guarded against accidental contact. (c) Equipment for generating high frequency currents or voltages used in electrocautery, diathermy, television, etc., where installed or used in an anesthetizing location, shall conform to Sections 517-3 and 517-4. 517-9. Grounding. In any hazardous area, all metallic raceways, and all noncurrent-carrying metallic portions of fixed or portable equip- ment (except equipment operating at not more than 8 volts between conductors) shall be grounded as provided in Sections 501-16 (a) and (b). ARTICLE 520—THEATERS AND ASSEMBLY HALLS A. General 520-1. Scope. The requirements of this Article shall apply to all buildings, or part of a building, designed, intended, or used for drama- tic, operatic, motion-picture or other shows, and night clubs, dance 70-306 NATIONAL ELECTRICAL CODE halls, armories, sporting arenas, bowling alleys, public auditoriums, television studios and like buildings used for public assembly. 520-2. Motion-Picture Projectors. Motion-picture equipment and its installation and use shall comply with Article 540. 520-3. Sound Reproduction. Sound-reproducing equipment and its in- stallation shall comply with Article 640. 520-4. Wiring Method. The wiring method shall be metal raceways, Type ALS cable or Type MI cable except as follows: Exception No. 1. As provided in Article 640, Sound Reproduction, in Article 800, Communication Circuits, and in Article 725 for Class 2 Remote Control and Signal Circuits. Exception No. 2. Where the area intended for public assembly has a capacity of less than 200 persons, Type AC metal-clad cable as pro- vided in Article 334 may be used, or for concealed work, concealed knob-and-tube work or nonmetallic sheathed cable as provided in Ar- ticles 324 and 336 may also be used. For recommendations for determination of population capacity, refer to Life Safety Code (NFPA No. 101). Exception No. 3. The wiring for stage set lighting and stage effects and other wiring which is not fixed as to location shall be done with approved portable cables and approved flexible cords. 520-5. Number of Conductors in Raceway. The number of conduc- tors permitted in any metal conduit or electrical metallic tubing for border or stage pocket circuits or for remote control conductors shall not exceed that shown in Table 1 of Chapter 9. When contained within a wireway, the sum of the cross sectional areas of all contained con- ductors at any cross section shall not exceed 20 per cent of the interior cross sectional area of the wireway. The 30 conductor limitation of Section 362-5 shall not apply. 520-6. Enclosing and Guarding Live Parts. Live parts shall be enclosed or guarded to prevent accidental contact by persons and objects. All switches shall be of the externally operable type. Rheostats shall be placed in approved cases or cabinets which enclose all live parts, hav- ing only the operating handles exposed. B. Fixed Stage Switchboard 520-21. Dead Front. Stage switchboards shall be of the dead-front type. 520-22. Guarding Back of Switchboard. Stage switchboards having exposed live parts on the back of such boards shall be enclosed by the building walls, wire mesh grills, or by other approved methods. The entrance to this enclosure shall be by means of a self-closing door. 520-23. Control and Overcurrent Protection of Receptacle Circuits. Means shall be provided at the stage switchboard for the control and individual overcurrent protection of branch circuits to stage and gal- lery receptacles used for portable stage equipment. 520-24. Metal Hood. A stage switchboard that is not completely en- closed dead-front and dead-rear or recessed into a wall shall be pro- ARTICLE 520—THEATERS AND ASSEMBLY HALLS 70-307 vided with a metal hood extending the full length of the board to pro- tect all equipment on the board from falling objects. 520-25. Dimmers. Dimmers shall conform to the following: (a) Disconnection and Overcurrent Protection. Where dimmers are installed in ungrounded conductors, each dimmer shall have overcur- rent protection not greater than 125 per cent of the dimmer rating, and shall be disconnected from all ungrounded conductors when the mas- ter or individual switch or circuit-breaker supplying such dimmer is in the open position. (b) Resistance or Reactor Type Dimmers. Resistance or series re- actor type dimmers may be placed in either the grounded or the un- grounded conductor of the circuit. Where designed to open either the supply circuit to the dimmer or the circuit controlled by it, the dimmer shall then comply with Section 380-1. It is recommended that resistance or reactor type dimmers be placed in the grounded neutral conductor of the circuit provided they do not open the circuit. (c) Auto-Transformer Type Dimmers. The circuit supplying an auto-transformer type dimmer shall not exceed 150 volts between conductors.The grounded conductor shall be common to the input and output circuits.See Section 200-4. C. Stage Equipment—Fixed 520-41. Circuit Loads. Footlights, border lights, and proscenium side lights shall be so arranged that no branch circuit supplying such equip- ment will carry a load exceeding 20 amperes; provided that where heavy-duty lampholders only are used, such circuits may conform to the provisions of Article 210 for circuits supplying heavy-duty lamp- holders. 520-42. Conductor Insulation. Foot, border, proscenium, or portable strip light fixtures shall be wired with conductors having insulation suitable for the temperatures at which the conductors will be operated and not less than 125 °C (257°F).See Table 310-2(a). 520-43. Footlights. (a) Where metal trough construction is employed for footlights, the trough containing the circuit conductors shall be made of sheet metal not lighter than No.20 USS gage (.0359 inch in thickness) treated to prevent oxidation. Lampholder terminals shall be kept at least 1/2 inch from the metal of the trough. The circuit conductors shall be soldered to the lampholder terminals. (b) Where the metal trough construction specified in Section 520- 43(a) is not used, footlights shall consist of individual outlets with lampholders, wired with rigid or flexible metal conduit, Type ALS ca- ble or Type MI cable. The circuit conductors shall be soldered to the lampholder terminals. Disappearing footlights shall be so arranged that the current supply shall be automatically disconnected when the foot- lights are replaced in the recess designed therefor. 70-308 NATIONAL ELECTRICAL CODE 520-44. Borders and Proscenium Sidelights. (a) Borders and proscenium sidelights shall be constructed as pre- scribed in Section 520-43, shall be suitably stayed and supported, and shall be so designed that the flanges of the reflectors or other adequate guards will protect the lamps from mechanical injury and from acci- dental contact with scenery or other combustible material. (b) Cables for Border Lights. Cables for supply to border lights shall be types S, SO, or ST flexible cord. See Table 400-11. The cables shall be suitably supported. Such cables shall be employed only where flexible conductors are necessary. 520-45. Receptacles. Receptacles intended for the supply of arc lamps shall have not less than 50 amperes capacity and shall be supplied by conductors not smaller than No. 6. Receptacles intended for the supply of incandescent lamps shall have not less than 20 amperes capacity and shall be supplied by conductors not smaller than No. 12. Plugs for arc and incandescent receptacles shall not be interchangeable. 520-46. Stage Pockets. Receptacles intended for the connection of portable stage lighting equipment shall be mounted in suitable pockets or enclosures, and shall comply with the requirements of Section 520- 45. 520-47. Lamps in Scene Docks. Lamps installed in scene docks shall be so located and guarded as to be free from mechanical injury and provide an air space of not less than 2 inches between such lamps and any combustible material. 520-48. Curtain Motors. Curtain motors having brushes or sliding contacts shall comply with one of the following conditions: (a) Be of the totally enclosed, enclosed-fan-cooled, or enclosed-pipe- ventilated types. (b) Be enclosed in separate rooms or housings built of noncombus- tible materials so constructed as to exclude flyings or lint, and properly ventilated from a source of clean air. (c) Have brush or sliding-contact end of motor enclosed by solid metal covers. (d) Have brushes or sliding contacts enclosed in substantial, tight, metal housings. (e) Have the upper half of brush or sliding-contact end of the motor enclosed by a wire screen or perforated metal and the lower half en- closed by solid metal covers. (f) Have wire screens or perforated metal placed at the commutator or brush ends. No dimension of any opening in the wire screen or perforated metal shall exceed .05 inch, regardless of the shape of the opening and of the material used. 520-49. Flue-Damper Control. Where stage flue dampers are released by an electrical device, the circuit operating the latter shall be normally closed and shall be controlled by at least two externally operable switches, one switch being placed at the electrician's station and the other where designated by the authority having jurisdiction. The device ARTICLE 520—THEATERS AND ASSEMBLY HALLS 70-309 shall be designed for the full voltage of the circuit to which it is con- nected, no resistance being inserted. The device shall be located in the loft above the scenery and shall be enclosed in a suitable iron box having a tight,self-closing door. D. Portable Switchboards on Stage 520-51. Supply. Portable switchboards shall be supplied only from outlets especially provided for this purpose. Such outlets shall include externally operable, enclosed fused switches or circuit breakers mounted on the stage wall or at the switchboard in locations readily accessible from the stage floor. 520-52. Overcurrent Protection. Circuits from portable switchboards directly supplying equipment containing incandescent lamps of not over 300 watts shall be protected by overcurrent devices having a rating or setting of not more than 20 amperes. Circuits for lampholders over 300 watts may be used where overcurrent protection conforms to the provisions of Article 210. Other circuits shall be provided with overcurrent devices with a rating or setting not higher than the current required for the connected load. 520-53. Construction. Portable switchboards for use on stages shall comply with the following: (a) Enclosure. Portable switchboards shall be placed within an en- closure of substantial construction which may be so arranged that the enclosure is open during operation. Enclosures of wood shall be com- pletely lined with sheet metal of not less than No. 24 USS gage (.0239 inch), and shall be well galvanized, enamelled, or otherwise properly coated to prevent corrosion or be of a corrosion-resistant material. (b) Live Parts. Except as provided for dimmer face plates in Sec- tion 520-53(e),there shall be no exposed live parts within the enclosure. (c) Switches and Circuit Breakers. All switches and circuit breakers shall be of the externally operable,enclosed type. (d) Circuit Protection. Overcurrent devices shall be provided in each ungrounded conductor of every circuit supplied through the switchboard. Enclosures shall be provided for all overcurrent devices in addition to the switchboard enclosure. (e) Dimmers. The terminals of dimmers shall be provided with en- closures, and dimmer face plates shall be so arranged that accidental contact cannot be readily made with the face-plate contacts. (f) Interior Conductors. All conductors within the switchboard en- closure shall be stranded and, except for cables feeding to or from the switchboard, shall be asbestos-covered type AA or other types approved for a maximum operating temperature of 200°C (392°F). Each con- ductor shall have an ampacity at least equal to the rating of the circuit breaker, switch or fuse which it supplies, except for conductors for in- candescent lamp circuits having overcurrent protection not exceeding 20 amperes. Conductors shall be enclosed in metal troughs or securely fastened in position and shall be bushed where they pass through metal. (g) Pilot Light. A pilot light shall be provided within the enclosure and shall be so connected to the circuit supplying the board that the 70-310 NATIONAL ELECTRICAL CODE opening of the master switch will not cut off the supply to the lamp. This lamp shall be on an independent circuit having overcurrent pro- tection of a rating or setting of not more than 15 amperes. (h) Supply Connections. The supply to a portable switchboard shall be by means of flexible cord (types S, SO or ST) terminating within the switchboard enclosure or in an externally operable fused master switch or circuit breaker. The supply cable shall have sufficient am- pacity to carry the total load on the switchboard and shall be protected by overcurrent devices. (i) Cable Arrangement. Cables shall be protected by bushings where they pass through enclosures and shall be so arranged that tension on the cable will not be transmitted to the connections. (j) Terminals. Terminals to which stage cables are connected shall be so located as to permit convenient access to the terminals. At termi- nals not provided with approved pressure connectors the following con- struction shall be employed: (1) For conductors of No. 10 or larger,solder lugs shall be used. (2) For conductors smaller than No. 10, the strands shall be sol- dered together where connected to clamps or binding screws not spe- cifically approved as pressure connectors. E. Stage Equipment—Portable 520-61. Arc Lamps. The construction of arc lamps shall be approved by the authorities having jurisdiction. 520-62. Portable Plugging Boxes. Portable plugging boxes shall con- form to the following: (a) Enclosure. The construction shall be such that no current- carrying part will be exposed. (b) Receptacles and Overcurrent Protection. Each receptacle shall have a rating of not less than 30 amperes, and shall have overcurrent protection which shall be installed in an enclosure equipped with self- closing doors. (c) Busbars and Terminals. Busbars shall have an ampacity equal to the sum of the ampere ratings of all the receptacles. Lugs shall be provided for the connection of the master cable. 520-63. Lights on Scenery. (a) Brackets on scenery shall be wired internally and the fixture stem shall be carried through to the back of the scenery where a bush- ing shall be placed on the end of the stem, except that externally wired brackets or other fixtures may be used when wired with cords de- signed for hard usage which shall extend through scenery and with- out joint or splice in canopy of fixture back and terminate in an ap- proved type stage connector located within 18 inches of the fixture, unless such location is impractical. (b) Fixtures shall be securely fastened in place. 520-64. Portable Strips. Portable strips shall be constructed in ac- cordance with the requirements for border lights and proscenium side ARTICLE 520—THEATERS AND ASSEMBLY HALLS 70-311 lights in Section 520-44(a). The supply cable shall be protected by bushings where it passes through metal and shall be so arranged that tension on the cable will not be transmitted to the connections. See Section 520-42 for wiring of portable strips. 520-65. Festoons. Joints in festoon wiring shall be staggered where practicable. Lamps enclosed in lanterns or similar devices of combus- tible material shall be equipped with approved guards. 520-66. Special Effects. Electrical devices used for simulating light- ning, waterfalls, and the like, shall be so constructed and located that flames, sparks, or hot particles cannot come in contact with combustible material. 520-67. Cable Connectors. Cable connectors for flexible conductors shall be so constructed that tension on the cord or cable will not be transmitted to the connections. See Section 400-9. The female half of the connector shall be attached to the line end of the cord or cable. 520-68. Conductors for Portables. Flexible conductors used to supply portable stage equipment shall be Types S, SO or ST, except that re- inforced cord may be used to supply stand lamps where the cord is not liable to severe physical damage and is protected by an overcurrent protection rated at not over 20 amperes. F. Dressing Rooms 520-71. Pendant Lampholders. Pendant lampholders shall not be in- stalled in dressing rooms. 520-72. Lamp Guards. All incandescent lamps in dressing rooms, where less than 8 feet from the floor, shall be equipped with open-end guards riveted to the outlet box cover or otherwise sealed or locked in place. 520-73. Switches Required. All lights and receptacles in dressing rooms shall be controlled by wall switches installed in the dressing rooms.Each switch controlling receptacles shall be provided with a pilot light to indicate when the receptacle or receptacles are energized. G. Grounding 520-81. Grounding. All metal raceways shall be grounded. The metal frames and enclosures of equipment including border lights shall be grounded, except the frames and enclosures of portable equipment on grounded circuits operating at not over 150 volts to ground and not within reach of grounded surfaces. Grounding, when employed, shall be done in the manner specified in Article 250. 70-312 NATIONAL ELECTRICAL CODE ARTICLE 530—MOTION-PICTURE STUDIOS AND SIMILAR LOCATIONS A. General 530-1. Scope. The requirements of this Article shall apply to television studios (except as covered in Section 520-1), motion-picture studios, exchange, factory, laboratory, stage, or a portion of the building in which motion-picture films more than Vs inch in width are manufac- tured, exposed, developed, printed, cut, edited, rewound, repaired or stored. For the purpose of this Article, a motion-picture studio is one in which photographic film is used to record action. A television studio shall mean one which employs the use of electronic cameras only. For recommendations for protection against cellulose nitrate film hazards refer to NFPA Standard for the Storage and Handling of Cellulose Nitrate Motion Picture Film (No.40). B. Stage or Set 530-11. Permanent Wiring. The permanent wiring shall be Type ALS cable,Type MI cable or in approved metal raceways. Exception. Communication circuits, and sound recording and re- producing equipment may be wired as permitted by the articles cover- ing those installations. (See Articles 640 and 800). 530-12. Portable Wiring. The wiring for stage set lighting and stage effects, and other wiring which is not fixed as to location, shall be done with approved portable cables and approved flexible cords. This re- quirement shall not apply to portable lamps or other electrical equip- ment used as properties in a motion picture set, on a studio stage or lot,or on location. 530-13. Stage Lighting and Effects Control. Switches used for studio stage set lighting and effects (on the stages and lots and on location) shall be of the externally operable type. When contactors are used as the disconnecting means for fuses, an individual externally operable type switch (such as a tumbler switch) for the control of each contac- tor, shall be located at a distance of not more than six feet from the contactor,in addition to remote control switches. Exception. A single externally operable switch may be used to si- multaneously disconnect all the contactors on any one location board, where located at a distance of not more than 6 feet from the location board. 530-14. Plugging Boxes. Each receptacle of plugging boxes shall have an ampacity of not less than 30 amperes. 530-15. Enclosing and Guarding Live Parts. (a) Live parts shall be enclosed or guarded to prevent accidental contact by persons and objects. (b) All switches shall be of the externally operable type. ARTICLE 530—MOTION-PICTURE STUDIOS 70-313 (c) Rheostats shall be placed in approved cases or cabinets which enclose all live parts,having only the operating handles exposed. (d) Current-carrying parts of "bull-switches," "location boards," "spiders," and plugging boxes shall be so enclosed, guarded, or located that persons cannot accidentally come into contact with them or bring conducting materials into contact with them. 530-16. Portable Lamps. Portable lamps and work lights shall be equipped with approved portable cords, approved composition or metal-sheathed porcelain sockets and substantial guards. Exception. The requirements of this Section shall not apply to port- able lamps used as properties in a motion picture set or television stage set,on a studio stage or lot, or on location. 530-17. Portable Arc Lamps. Portable arc lamps shall be substantially constructed. The arc shall be provided with an enclosure designed to retain sparks and carbons and to prevent persons or materials from coming into contact with the arc or bare live parts. The enclosures shall be ventilated.All switches shall be of the externally operable type. 530-18. Overcurrent Protection—Short Time Rating.* (a) General. Automatic overcurrent protective devices (circuit breakers or fuses) for feeders, and subfeeders for moving-picture stu- dio stage set lighting and the stage cables for such stage set lighting,shall be rated or set to operate at not more than 400 per cent of the values given in Tables 310-12 and 400-9. *Special consideration is given to motion-picture studios because filming periods are of only a few minutes duration and are rarely longer than 10 minutes. (b) Feeders. The feeders from the substations to the stages shall be protected by means of overcurrent devices having suitable ampacity (generally located in the substation). The overcurrent devices may be double-pole, or two single-pole gang-operated devices may be used. There need be no pole or overcurrent coil in the neutral conductor. The overcurrent device setting for each feeder shall not exceed 400 per cent of the ampacity of the feeder, as given in Table 310-12 for the kind of insulation used. (c) "Location Boards." Overcurrent protection (fuses or circuit breakers) shall be provided at the "location boards." The fuses in the "location boards" shall be not larger in rating than 400 per cent of the ampacity of the cables between the "location boards" and the plugging boxes. (d) Plugging Boxes. Where plugging boxes are not provided with overcurrent protective devices, each cable or cord smaller than No. 8 supplied through a plugging box shall be attached to the plugging box by means of a plug containing two cartridge fuses or a circuit breaker. The rating of the fuses or the setting of the circuit breaker shall be not more than 400 per cent of the safe ampacity of the cables or cords as given in Tables 310-12, 310-13 and 400-8 for the kind of insulation used. (e) Lighting. Work-lights, stand-lamps, and fixtures shall be con- nected to plugging boxes by means of plugs containing two cartridge 70-314 NATIONAL ELECTRICAL CODE fuses not larger than 20 amperes, or they may be connected to special outlets on circuits protected by fuses or circuit-breaker settings of not more than 20 amperes. Plug fuses shall not be used unless they are on the load side of the fuse or circuit breakers on the"location boards." 530-19. Sizing of Feeder Conductors: Television Studio Sets. (a) General. The demand factors listed in Table 530-19(a) may be applied to that portion of the maximum possible connected load for studio or stage set lighting for all permanently installed feeders between substations and stages and to all permanently installed subfeeders be- tween the main stage switchboard and stage distribution centers or location boards. Table 530-19(a). Demand Factors for Stage Set Lighting Total Stage Set Lighting Feeder Demand Load(Wattage) Factor First 50,000 or less at 100% Next 50,001 to 100,000 at 75% Next 100,001 to 200,000 at 60% All over 200,000 50% (b) Portable Feeders. A demand factor of 50 per cent of maximum possible connected load may be applied to all portable feeders. 530-20. Grounding. Conduit, armored cable or metal raceways, and all noncurrent-carrying metal parts of appliances, devices and equip- ment shall be grounded as prescribed in Article 250. This shall not ap- ply to pendant and portable lamps, nor to stage lighting and stage sound equipment, nor to other portable or semiportable special stage equipment,operating at not more than 150 volts to ground. C. Dressing Rooms 530-31. Dressing Rooms. Fixed wiring in dressing rooms shall be in- stalled in accordance with wiring methods covered in Chapter 3. Wir- ing for portable dressing rooms shall be of an approved type. D. Viewing,Cutting and Patching Tables 530-41. Lamps at Tables. Only approved composition or metal- sheathed porcelain keyless lampholders, equipped with suitable means to guard lamps from physical damage and from film and film scrap, shall be used at patching,viewing and cutting tables. E. Film Storage Vaults 530-51. Lamps in Cellulose Nitrate Film Storage Vaults. Lamps in cel- lulose nitrate film storage vaults shall be rigid fixtures of the glass en- closed and gasketed type. Lamps shall be controlled by a switch hav- ing a pole in each ungrounded conductor. This switch shall be located outside of the vault and provided with a pilot light to indicate whether the switch is on or off. This switch shall disconnect from all sources of supply all ungrounded conductors terminating in any outlet in the vault. ARTICLE 540—MOTION-PICTURE PROJECTORS 70-315 530-52. Motors and Other Electrical Equipment in Film Storage Vaults. No electric motors, heaters, portable lights, or other portable electric equipment shall be located in the film storage vaults. F. Substations 530-61. Substations. Wiring and equipment above 600 volts shall con- form to Article 710. 530-62. Low-Voltage Switchboards. On 600 volts or less switch- boards shall conform to Article 384. 530-63. Overcurrent Protection of DC Generators. Three-wire DC gen- erators shall have protection consisting of overcurrent devices having current ratings or settings in accordance with the generator rating. The overcurrent protective devices may be single-pole or two-pole and need not have a pole or over-current coil in the neutral lead (whether it is grounded or ungrounded). 530-64. Working Space and Guarding. Working space and guarding in permanent fixed substations shall conform to Sections 110-16 and 110-17. For guarding of live parts on motors and generators, see Sec- tion 430-11 and 430-14. Switchboards for voltage of not more than 250 volts DC between conductors when located in substations or switch- board rooms accessible to qualified persons only need not be dead- front. 530-65. Portable Substations. Wiring and equipment in portable sub- stations shall conform to the sections applying to installations in perma- nent fixed substations, but, due to the limited space available, the work- ing spaces may be reduced, provided that the equipment shall be so arranged that the operator may do his work safely, and so that other persons in the vicinity cannot accidentally come into contact with current-carrying parts or bring conducting objects into contact with them while they are energized. 530-66. Grounding at Substations. Noncurrent-carrying metal parts shall be grounded except the frames of DC circuit breakers installed on switchboards. ARTICLE 540—MOTION-PICTURE PROJECTORS A. General 540-1. Scope. This Article applies to motion-picture projectors and associated equipment of the Professional and Nonprofessional Types. B. Equipment and Projectors of the Professional Type 540-10. Professional Projector — Definition. The professional projec- tor employs a 35-millimeter film which is 13/s inch wide and has on each edge 5.4 perforations per inch. Wider film such as 70-millimeter may be employed. 540-11. Enclosure. The professional type of projector, such as is com- monly used in theaters and motion-picture houses, shall be located in 70-316 NATIONAL ELECTRICAL CODE an approved enclosure. Such enclosure shall not be considered as a hazardous location as defined in Article 500. 540-12. Motor-Driven Projectors. Motor-driven projectors shall be ap- proved for the purpose as an assembly or shall comply with all of the following conditions: (a) An approved projector shall be used. (b) An approved projector lamp shall be used. (c) Motors shall be so designed or guarded as to prevent ignition of film by sparks or arcs. (d) Projectors shall be in charge of a qualified operator. 540-13. Conductor Size. Conductors supplying outlets for arc projec- tors of the professional type shall not be smaller than No. 8 and shall be of sufficient size for the projector employed. Conductors for in- candescent type projectors shall conform to normal wiring standards as provided in Section 210-25. 540-14. Conductors on Lamps and Hot Equipment. Asbestos cov- ered conductors type AA or other types of insulated conductors having a maximum operating temperature of 200°C (392°F) shall be used on all lamps or other equipment where the ambient temperature at the conductors as installed will exceed 50°C (122°F). 540-15. Flexible Cords. Cords approved for hard service in Table 400-11 shall be used on portable equipment. 540-16. Lamp Guards. Incandescent lamps in projection rooms or booths shall be provided with an approved lamp guard unless otherwise protected by noncombustible shades or other enclosures. 540-17. Location of Equipment. Motor-generator sets, transformers, rectifiers, rheostats, and similar equipment, for the supply or control of current to arc lamps on projectors shall, if practicable, be located in separate rooms. Where placed in the projector room, they shall be so located or guarded that arcs or sparks cannot come in contact with film, and motor-generator sets shall have the commutator end or ends protected as provided in Section 520-48. 540-18. Construction and Ventilation. It is recommended that the authority having jurisdiction over the construction and ventilation of rooms for professional type projectors refer to the NFPA Standard for the Storage and Handling of Cellulose Nitrate Motion Picture Film (NFPA No.40). 540-19. Equipment Prohibited. Switches, overcurrent devices, or other equipment not normally required or used for projectors, sound reproduction, flood, or other special effect lamps or other equipment shall not be installed in such booths or rooms. Exception. Remote-control switches for the control of auditorium lights or a switch for the motor operating the curtain at the motion- picture screen. 540-20. Approval. Projectors and enclosures for arc or incandescent lamps, rectifiers, transformers, rheostats, and similar equipment, shall be of an approved type. ARTICLE 550—MOBILE HOMES 70-317 540-21. Marking. Projectors and other equipment as set forth in Sec- tion 540-20 shall be marked with the name or trademark of the maker and with the voltage and current for which they are designed. 540-22. Rewinding, Examination and Storage of Extra Films. It is rec- ommended that the authority having jurisdiction refer to the NFPA Standard for the Storage and Handling of Cellulose Nitrate Motion Pic- ture Film(NFPA No.40). See Sections 530-51 and 530-52.Also see Section 530-41 for viewing tables. C. Nonprofessional Type Projectors 540-30. Definition. The nonprofessional projector employs film other than that used on professional type projectors. 540-31. Booth Not Required. Projectors of the nonprofessional or min- iature type,when employing only approved slow-burning (cellulose ace- tate or equivalent) film,may be operated without a booth. 540-32. Approval. Projectors, lamp enclosures, and current-control- ling devices and similar devices shall be approved as component parts of the projector equipment. 540-33. Source of Illumination. The source of illumination shall be a lamp or a type approved for stereopticon use or for motion-picture pro- jection. 540-34. Marking. Projectors shall be marked with name or trademark of the maker, with the current and voltage for which they are designed, and for projectors of this type using the standard 35-millimeter film, with the wording"For use with slow-burning films only." 540-35. Nonprofessional Film Marking. The slow-burning (cellulose acetate or equivalent) film shall have a permanent distinctive marker for its entire length identifying the manufacturer and the slow-burning character of the film stock. D. Sound Recording and Reproduction 540-50. Sound Recording and Reproduction. Sound recording and re- production equipment shall comply with Article 640. ARTICLE 550—MOBILE HOMES 550-1. Scope. (a) The provisions of this Article cover the electric conductors and equipment installed within or on mobile homes and also the conductors that connect mobile homes to a supply of electricity. Wherever the requirements of other Articles of the National Elec- trical Code and Article 550 differ, the requirements of Article 550 shall apply. (b) A mobile home not intended as a dwelling unit, as for example, equipped for sleeping purposes only, contractor's on-site offices, con- struction job dormitories, mobile studio dressing rooms, banks, clinics, 70-318 NATIONAL ELECTRICAL CODE mobile stores or intended for the display or demonstration of merchan- dise or machinery, shall not be required to meet the provisions of this Article pertaining to the number or capacity of circuits required. It shall, however, meet all other applicable requirements of this Article if provided with an electrical installation intended to be energized from a 115 volt or 115/230 volt AC power supply system. (c) The provisions of this Article apply to mobile homes intended for connection to a wiring system nominally rated 115/230 volts, 3-wire AC,with grounded neutral. 550-2. Definition. Mobile Home: a vehicular, portable structure built on a chassis and designed to be used without a permanent foundation as a dwelling when connected to indicated utilities. 550-3. Power Supply. The mobile home service equipment shall be located adjacent to the mobile home and not mounted in or on the mo- bile home. The power supply to the mobile home shall be feeder circuits con- sisting of not more than two mobile home supply cords each rated 50 amperes or permanently installed circuits. Exception: A mobile home that is factory-equipped with gas or oil- fired central heating equipment and cooking appliances may be provi- ded with a mobile home supply cord rated 40 amperes,minimum. (a) Each such mobile home supply cord shall be approved for the purpose and have four conductors, one of which shall be identified by a continuous green color or a continuous green color with one or more yellow stripes. The attachment plug, connectors and mating receptacles shall be of a 3-pole,4-wire grounding type covered by American Stand- ard—C73 Attachment Plugs and Receptacles. The mobile home power-supply cord shall be permanently attached to the mobile home distribution panel.A suitable clamp or the equivalent shall be provided at the distribution panel to afford strain relief for the cord to prevent strain from being transmitted to the terminals. The power supply cord shall be not less than 21 feet nor more than 261 feet long. (b) Second Supply Cord. Where the calculated load of the mobile home is in excess of 50 amperes, or where a separately metered appli- ance is installed in the mobile home, a second 50-ampere mobile home supply cord shall be installed. Where two cord supply systems are in- stalled, they shall not be interconnected on either the line side or the load side except that the grounding circuits and grounding means shall be electrically interconnected. (c) Permanent Wiring. Where the calculated load exceeds 100 am- peres or where a permanent feeder is used the supply shall be by means of four permanently installed conductors in an approved wiring method, one conductor being identified by a continuous green color or a con- tinuous green color with one or more yellow stripes. See Tentative Interim Amendment No. 148 at back of book. 550-4. Disconnecting Means and Branch Circuit Protective Equipment. The branch circuit equipment may be combined with the disconnecting ARTICLE 550—MOBILE HOMES 70-319 means as a single assembly. Such a combination may be designated as a distribution panel. Plug fuses and fuseholders shall be tamper-resistant, type "S," en- closed in dead-front fuse panels. (a) Disconnecting Means. Disconnecting means shall be provided in each mobile home and shall be approved service entrance equipment consisting of circuit-breakers or a switch and fuses and their accessories installed in a readily accessible location near the point of entrance of the supply cord or conductors into the mobile home. This equipment shall contain a solderless type of grounding connector or bar for the purposes of grounding with sufficient terminals for all grounding conductors. The neutral bar termination of the grounded circuit conductors shall be insulated. The disconnecting equipment shall have a rating suitable for the connected load. Where two power supply cords are installed disconnecting means shall be provided for each cord and may be combined in a single equip- ment but without electrical interconnections other than for grounding purposes. A distribution panel main circuit-breaker shall be rated 50 amperes and employ a 2-pole circuit breaker rated 40 amperes for a 40-ampere supply cord, or 50 amperes for a 50-ampere supply cord. A distribu- tion panel employing a disconnect switch and fuses shall be rated 60 amperes and shall employ a single 2-pole 60-ampere fuseholder with 40- or 50-ampere main fuses for 40- or 50-ampere supply cords, re- spectively. The outside of the distribution panel shall be plainly marked with the fuse size. The main circuit breakers or fuses shall be plainly marked"Main." (b) Branch Circuit Protective Equipment. Branch circuit distribution equipment shall be installed in each mobile home and shall include overcurrent protection for each branch circuit consisting of either cir- cuit breakers or fuses. Where circuit breakers are provided for branch-circuit protection, 230-volt circuits shall be protected by 2-pole common or companion trip,or handle-tied paired circuit breakers. The branch-circuit overcurrent devices shall be rated: (1) not more than the circuit conductors;and (2) not more than 150 per cent of the rating of a single appliance rated 10 amperes or more;but (3) not more than the fuse size marked on the air conditioner or other motor-operated appliance. (c) Electrical Nameplates. A metal nameplate on the outside adja- cent to the supply cord entrance shall read, "This Mobile Home is Wired for 115/230 Volt, 3-wire, 60 Cycle Supply. Supply Cord 40 (or 50) amp." The voltage marking may read 120/240 Volts instead of 115/230 Volts. 550-5. Branch Circuits. The number of branch circuits required shall be determined in accordance with the following: 70-320 NATIONAL ELECTRICAL CODE (a) Lighting. Based on 3 watts per square foot times outside di- mensions of the mobile home (hitch excluded) divided by 115 volts to determine number of 15 or 20 ampere lighting area circuits,e.g., 3 X Length X Width —No.of 15 (or 20) ampere circuits. 115 X 15 (or 20) (b) Portable Appliances. There shall be a minimum of two 20 am- pere branch circuits for receptacle outlets in the kitchen area, which may supply other receptacle outlets in the dining, laundry, and patio areas.These circuits shall supply only portable appliances. (c) General Appliances. (Including Furnace, Water Heater, Range, and Central or Room Air Conditioner, Etc.) There shall be one or more circuits of adequate rating in accordance with the following: (1) Ampere rating of fixed appliances not over 50 per cent of cir- cuit rating if lighting outlets (receptacles, other than kitchen, dining area,and laundry,considered as lighting outlets) are on same circuit; (2) For fixed appliances on a circuit without lighting outlets, the sum of rated amperes shall not exceed the branch-circuit rating for other than motor loads or 80 per cent of the branch-circuit rating for air conditioning or other motor loads; (3) The rating of a single portable appliance on a circuit having no other outlets shall not exceed 80 per cent of the circuit rating; (4) The rating of range branch circuit shall be based on the range demand as specified for ranges in Section 550-11 (b) (5). For the laundry branch circuit,see Section 220-3(b). 550-6. Receptacle Outlets. (a) All receptacle outlets: (1) shall be of grounding type; (2) shall be installed according to Section 210-7;and (3) except when supplying specific appliances, receptacles shall be parallel blade, 15-ampere, 125-volt,either single or duplex. (b) There shall be an individual outlet of the grounding type for each cord-connected fixed appliance installed. (c) Except in the bath and hall areas, receptacle outlets shall be in- stalled at all wall spaces 2 feet wide or more, so that no point along the floor line is more than 6 feet, measured horizontally,from an outlet in that space. Except as explained in the following, receptacle outlets are not required for wall spaces occupied by kitchen or wardrobe cabi- nets. In addition,a receptacle outlet shall be installed: (1) Over counter tops in the kitchen (at least one on each side of the sink if counter tops are on each side); (2) Adjacent to the refrigerator and free-standing gas-range space; (3) At counter top spaces for built-in vanities; (4) At counter top spaces under wall-mounted cabinets. ARTICLE 550—MOBILE HOMES 70-321 (d) Receptacle outlets shall not be installed within or adjacent to a shower or bathtub space. 550-7. Fixtures and Appliances. (a) Water heaters, refrigerators, air conditioning equipment, ranges, electric heaters, washers, dryers and other like appliances shall be of an approved type and shall be connected in an approved manner and securely fastened in position. (See Section 550-9 for provisions on grounding.) (b) (1) Specifically approved pendant-type fixtures or pendant cords may be installed in mobile homes. (2) If a lighting fixture is provided over a bathtub or in a shower stall,it shall be of the approved enclosed and gasketed type. (3) Switches shall not be located inside the tub or shower space. 550-8. Wiring Methods and Materials. Except as specifically limited in this Section the wiring methods and materials included in the Na- tional Electrical Code shall be used in mobile homes. (a) Nonmetallic outlet boxes are acceptable only with nonmetallic sheathed cable. (b) Nonmetallic cable located 15 inches or less above the floor, if exposed, shall be protected from physical damage by covering boards, guard strips, or conduit. Cable likely to be damaged by stowage shall be so protected in all cases. (c) Metal-clad and nonmetallic cables may be passed through the cen- ters of the wide side of 2 by 4 studs. However, they shall be protected where they pass through 2 by 2 studs or at other studs or frames where the cable or armor would be less than 11/2 inches from the inside or outside surface. Steel plates on each side of the cable, or a tube, with not less than No. 16 manufacturer's standard gage wall thickness, are required to protect the cable. These plates or tubes shall be securely held in place. (d) Where metallic faceplates are used they shall be effectively grounded. (e) If the range, clothes dryer, or similar appliance is connected by metal-clad cable or flexible conduit, a length of free cable or conduit should be provided to permit moving the appliance. The cable or flexi- ble conduit should be adequately secured to the wall. Clearance space behind a range may provide the required protection when a range is connected by Type SE cable. When used, Type SE cable shall have an identified and insulated neutral plus an equipment grounding conduc- tor. Nonmetallic cable (Type NM) shall not be used to connect a range. (f) Rigid metal conduit shall be provided with a locknut inside and outside the box, and a conduit bushing shall be used on the inside. Inside ends of the conduit shall be reamed. (g) Switches shall be rated as follows: (1) For lighting circuits, switches shall have a 10-ampere 125 volt rating;or higher,if needed for the connected load. 70-322 NATIONAL ELECTRICAL CODE (2) For motors or other loads, switches shall have ampere or horsepower ratings or both adequate for loads controlled. (An "AC general use"snap switch may control a motor 2 horsepower or less with full-load current not over 80 per cent of the switch ampere rating.) (h) At least 4 inches of free conductor shall be left at each outlet box except where conductors are intended to loop without joints. (i) Under Chassis Wiring (Exposed to Weather). (1) When outdoor or under chassis wiring is exposed to moisture and physical damage it shall be protected by rigid metal conduit or liquid-tight flexible metal conduit, except electrical metallic tubing may be used when closely routed against frames and equipment enclosures. (2) The conductors shall be Type NMC,TW,or equivalent. 550-9. Grounding. Grounding of both electrical and non-electrical metal parts in a mo- bile home is through connection to a grounding bus in the mobile home distribution panel. The grounding bus is grounded through the green- colored conductor in the supply cord or the feeder wiring to the service ground in the service entrance equipment located adjacent to the mo- bile home location.Neither the frame of the mobile home nor the frame of any appliance may be connected to the neutral conductor in the mo- bile home. (a) Insulated Neutral. (1) The grounded circuit conductor (neutral) shall be insulated from the grounding conductors and from equipment enclosures and other grounded parts. The grounded (neutral) circuit terminals in the distribution panel and in ranges, clothes dryers, counter-mounted cook- ing units, and wall-mounted ovens are to be insulated from the equip- ment enclosure. Bonding screws, straps, or buses in the distribution panel or in appliances are to be removed and discarded. (2) Connection of ranges and clothes dryers shall be made with 4 conductor cord and 3-pole, 4-wire grounding type plugs, or by ar- mored cable or conductors enclosed in flexible steel conduit. (b) Equipment Grounding Means. (1) The green-colored grounding wire in the supply cord or perma- nent feeder wiring shall be connected to the grounding bus in the dis- tribution panel or disconnecting means. (2) The chassis shall be grounded. The grounding conductor may be solid or stranded, insulated or bare, and shall be an armored ground- ing conductor or routed in conduit if No. 8 AWG. The conductor, if No. 6 AWG or larger, may be run without metal covering. The grounding conductor shall be connected between distribution panel grounding terminal and a terminal on the chassis. Grounding termi- nals shall be of the solderless type and approved as pressure terminal connectors recognized for the wire size employed. (3) In the electrical system, all exposed metal parts, enclosures, frames, lamp fixture canopies, etc., shall be effectively bonded to the grounding terminal or enclosure of the distribution panel. ARTICLE 550—MOBILE HOMES 70-323 (4) Cord-connected appliances, such as washing machines, clothes dryers, refrigerators, and the electrical system of gas ranges, etc., shall be grounded by means of an approved cord with grounding conductor and grounding type plug. (c) Grounding of Non-current-carrying Metal Parts. All major ex- posed metal parts that may become energized, including the water, gas and waste plumbing, the roof and outer metallic covering, the chas- sis and metallic circulating air ducts, shall be effectively bonded to the grounding terminal or enclosure of the distribution panel or to the metal chassis. See Section 550-9 (b) (2) for bonding of the chassis to the dis- tribution panel grounding terminal. 550-10. Testing. Dielectric Strength Test. The wiring of each mobile home shall be subjected to a 1-minute, 900-volt, dielectric strength test (with all switches closed) between live parts (including neutral) and the mobile home ground. Alternatively, the test may be performed at 1,088 volts for 1 second. This test shall be performed after branch cir- cuits are complete and after fixtures or appliances are installed. Exception: Fixtures or appliances which are approved shall not be required to withstand the dielectric strength test. 550-11. Calculations. The following method is to be employed in computing the supply cord and distribution panel load for each power supply assembly for each mobile home in lieu of the procedure shown in Article 220 and is based on 3-wire, 115/230 volt supply with 115 volt loads balanced between the two legs of the 3-wire system. (a) Lighting and Small Appliance Load: Lighting Watts: Length times width of mobile home (outside di- mensions,exclusive of hitch) times 3 watts per square foot;e.g., Length X width X 3 = lighting watts. Small appliance Watts: Number of circuits times 1,500 watts for each 20-ampere appliance receptacle circuit (see definition of Appli- ance,Portable with note);e.g., Number of circuits X 1,500= small appliance watts. Total: Lighting watts plus small appliance = total watts. First 3,000 total watts at 100 per cent plus remainder at 35 per cent = watts to be divided by 230 volts to obtain current (amperes) per leg. (b) Total load for determining power supply is the summation of: (1) Lighting and small appliance load as calculated in Section 550-11(a). (2) Name plate amperes for motors and heater loads (exhaust fans,air conditioners,* electric,gas,or oil heating).** * Omit smaller of these two, except include blower motor if used as air conditioner evaporator motor. **When an air conditioner is not installed and a 40-ampere power supply cord is provided,allow 15 amperes per leg for air conditioning. (3) 25% of current of largest motor in(2). 70-324 NATIONAL ELECTRICAL CODE (4) Total of nameplate amperes for: Disposal, Dishwasher, Water heater,Clothes dryer,Wall-mounted oven,Cooking units. Where number of these appliances exceeds three use 75% of total. (5) Derive amperes for free standing range (as distinguished from separate ovens and cooking units) by dividing values below by 230 volts. Name Plate Rating Use 10,000 w X or less 80 per cent of rating 10,001-12,500 w 8,000 w 12,501-13,500 w 8,400 w 13,501-14,500 w 8,800 w 14,501-15,500 w 9,200 w 15,501-16,500 w 9,600 w 16,501-17,500 w 10,000 w (6) If outlets or circuits are provided for other than factory in- stalled appliances include the anticipated load. See following Example for illustration of application of this calcula- tion. Example A mobile home is 70 X 10 feet and has two portable appliance circuits, a 1000 watt 230 volt heater, a 200 watt 115 volt exhaust fan,a 400 watt 115 volt dishwasher and a 7000 watt electric range. Lighting and small appliance load Lighting 70 X 10 X 3 = 2100 watts Small appliance 1500 X 2 = 3000 watts 5100 watts 1st 3000 watts at 100% 3000 Remainder (5,100—3,000 = 2,100) at 35% 735 3735 3735 = 16 amperes per leg 230 1000 watt (heater) ± 230= 4.4 amp 200 watt (fan) - 115 = 1.7 amp 400 watt (dishwasher) ± 115 = 3.5 amp 7000 watt (range) x .8 ± 230= 24. amp Amperes per leg A B Lighting and appliances 16 16 Heater (230 volt) 4 4 Fan (115 volt) 2 — Dishwasher (115 volt) — 4 Range 24 24 Totals 46 48 Based on the higher current calculated for either leg, use one 50- ampere supply cord. ARTICLE 551—TRAVEL TRAILERS 70-325 ARTICLE 551—TRAVEL TRAILERS 551-1. Scope. (a) The provisions of this Article cover the electric conductors and equipment installed within or on Travel Trailers and also on conductors that connect them to a supply of electricity. Wherever the requirements of other Articles of the National Elec- trical Code and Article 551 differ, the requirements of Article 551 shall apply. (b) A Travel Trailer not intended as a dwelling unit, as for example, for use as a mobile store, an office, a schoolroom or designed for the display or demonstration of merchandise or machinery shall not be required to meet the provisions of this Article pertaining to the num- ber or capacity of circuits required. It shall, however, meet all other applicable requirements of this Article if provided with an electrical in- stallation intended to be energized from a 115 volt, AC power supply system. (c) The provisions of this Article apply to the electrical equipment and materials of Travel Trailers intended for connection to a wiring system nominally rated 115 volts,2 wire,AC,with a grounded neutral. 551-2. Definition. Travel Trailer: A vehicular portable structure built on a chassis, designed to be used as a temporary dwelling for travel, recreational, and vacation use, and when factory equipped for the road it shall have a body width not exceeding 8 feet, and a body length not exceeding 32 feet. 551-3. Power Supply. The Travel Trailer service equipment shall be located adjacent to the Travel Trailer parking location and not mounted in or on the Travel Trailer. (a) The power supply to the Travel Trailer shall be a feeder circuit supply cord approved for the purpose rated 15, 20 or 30 amperes, 115 volts, and shall have three conductors, one of which shall be identified by a continuous green color or a continuous green color with one or more yellow stripes. The attachment plug, connectors and mating re- ceptacles shall be of a 2-pole, 3-wire grounding type covered by Amer- ican Standard C73 Attachment Plugs and Receptacles. (b) The supply cord shall be not less than 20 feet nor more than 261/2 feet long and shall be either separable or permanently attached. (1) Separable Cord Set. When a separable cord set, consisting of a cord, male and female fittings, is provided by the travel trailer manufacturer, the travel trailer shall be equipped with a permanently mounted, approved, male recessed-type attachment plug (motor base receptacle) wired directly to the distribution panel in an approved manner by means of approved service cable. The supply end of the cord set shall be equipped with an attachment plug of the type de- scribed in Section 551-3 (a). 70-326 NATIONAL ELECTRICAL CODE (2) Permanently Connected Power Cord. The cord shall be con- nected directly to the terminals of the distribution panel and provided with means to prevent strain from being transmitted to the terminals. The supply end of the cord shall be equipped with an attachment plug of the type described in Section 551-3(a). (d) Supply Cords shall be as follows: (1) 15 ampere No. 14/3 AWG for travel trailers which have a single 15 ampere general purpose branch circuit and gas or oil-fired heating and cooking appliance. (2) 20 ampere No. 12/3 AWG for travel trailers which have a single 20 ampere general purpose branch circuit and gas or oil-fired heating and cooking appliance. (3) 30 ampere No. 10/3 AWG for travel trailers with branch cir- cuits in accordance with Section 551-5 (b). 551-4. Disconnecting Means and Branch Circuit Protective Equipment. The branch circuit equipment may be combined with the disconnecting means as a single assembly. Such a combination may be designated as a distribution panel. Plug fuses and fuseholders shall be tamper-resistant, type "S" en- closed in dead-front fuse panels. (a) Disconnecting Means. Disconnecting means shall be provided in each travel trailer and shall be approved service entrance equipment consisting of circuit-breakers or a switch and fuses and their acces- sories installed in a readily accessible location near the point of entrance of the supply cord or conductors into the travel trailer. This equipment shall contain a solderless type of grounding connector or bar for the purposes of grounding with sufficient terminals for all grounding con- ductors. The neutral bar termination of the grounded circuit conductors shall be insulated. The disconnecting equipment shall have a rating suitable for the connected load. Travel trailers in which only a single branch circuit is installed may use a branch-circuit breaker or pull-out type of fuse- holder as disconnecting means if approved for use as service equipment. (b) Branch Circuit Protective Equipment. Branch circuit distribution equipment shall be installed in each travel trailer and shall include over- current protection for each branch circuit consisting of either circuit breakers or fuses. The branch-circuit overcurrent devices shall be rated: (1) not more than the circuit conductors;and (2) not more than 150 per cent of the rating of a single appliance rated 10 amperes or more. (c) Labeling at Electrical Entrance. Each travel trailer shall have permartently affixed to the exterior skin, at or near the point of en- trance of the power supply cord,a metal tag reading: "This travel trailer is wired for 110/125 volt AC service. Do not connect to higher volt- age." ARTICLE 551—TRAVEL TRAILERS 70-327 551-5. Branch Circuits. (a) Travel trailers with not more than six general appliance and re- ceptacle outlets combined shall have not less than either: (1) One general purpose (lighting) branch circuit, 15 amperes, No. 14 AWG circuit,to supply these outlets,or (2) One general purpose (lighting and appliance) branch circuit, 20 amperes, No. 12 AWG circuit, to supply these outlets, provided that the total rating of fixed appliances connected to this circuit shall not exceed 5 amperes or 600 watts. Note: Travel trailers wired in accordance with this Section shall not be equipped with fixed electric heating or cooking appliances. (b) Travel trailers with more than six general appliance and recep- tacle outlets combined shall have not less than: (1) One general purpose (lighting and appliance) branch circuit, 20 amperes or No. 12 gage conductors, minimum, which shall supply current to lighting outlets and receptacles only (shall not supply re- ceptacles in cooking and dining areas) and may supply fixed or porta- ble appliances such as electric water heaters. The total rating of such fixed or factory installed appliances shall not exceed 9 amperes or 1,000 watts,and (2) One appliance branch circuit, as follows: 20 amperes, No. 12 gage conductors, minimum, which shall supply current to receptacle outlets only in cooking and dining areas. 551-6. Receptacle Outlets. (a) All receptacle outlets; (1) shall be of the grounding type; (2) shall be installed according to Section 210-7; and (3) shall be of the parallel blade, 15 ampere, 125 volt type either single or duplex. (b) There shall be an individual outlet of the grounding type for each cord-connected fixed appliance installed. (c) Except in the bath area, receptacle outlets shall be installed at all wall spaces 2 feet wide or more, so that no point along the floor line is more than 6 feet, measured horizontally, from an outlet in that space. Except as explained in the following, receptacle outlets are not required for wall spaces that are partially or fully occupied by kitchen cabinets,wardrobes,built-in furniture,or similar facilities. In addition,a receptacle outlet shall be installed: (1) Over counter tops in the kitchen and dining area. (2) Adjacent to the refrigerator space, except when a gas-operated refrigerator containing no electrical circuit is factory installed. (3) Adjacent to a gas range space, except when a gas cooking ap- pliance containing no electrical circuit is factory installed. (4) At counter top spaces for built-in vanities. (d) No receptacle outlet shall be provided adjacent to a shower or bathtub. 70-328 NATIONAL ELECTRICAL CODE 551-7. Fixtures and Appliances. (a) Fixed Appliances: (1) All fixed appliances shall be of an approved type and shall be connected in an approved manner and securely fastened in position. (See Section 551-9 for provisions on grounding.) (b) Lighting Fixtures: (1) Pendant-type fixtures or pendant cords shall not be installed. (2) If a lighting fixture is provided over a bathtub or in a shower stall,it shall be of the approved enclosed and gasketed type. (3) Switches shall not be located inside the tub or shower space. 551-8. Wiring Methods and Materials. Except as specifically limited in this section, the wiring methods and materials included in the Na- tional Electrical Code shall be used in Travel Trailers. (a) Nonmetallic outlet boxes are acceptable only with nonmetallic sheathed cable. (b) Nonmetallic cable located 15 inches or less above the floor, if ex- posed, shall be protected from physical damage by covering boards, guard strips, or conduit. Cable likely to be damaged by stowage shall be so protected in all cases. (c) Metal-clad and nonmetallic cables may be passed through the cen- ters of the wide side of 2 by 4 studs. However, they shall be protected where they pass through 2 by 2 studs or at other studs or frames where the cable or armor would be less than 11/2 inches from the inside or outside surface. Steel plates on each side of the cable, or a tube, with not less than No. 16 manufacturer's standard gage wall thickness, are required to protect the cable. These plates or tubes shall be securely held in place. When the thickness of studs or frames makes it imprac- tical or impossible to use metal plates or tubes, particular care shall be exercised in the design and production of the travel trailer so as to avoid contacting the cables with nails, screws, or other fasteners, such care in design shall include appropriate routing of the cables through studs or frames at locations where the likelihood of their being con- tacted by nails, screws, or other fasteners subsequent to production is remote. (d) Where metallic faceplates are used they shall be effectively grounded. (e) Switches shall be rated as follows: (1) For lighting circuits, switches shall have a 10-ampere, 125 volt rating;or higher,if needed for the connected load. (2) For motors or other loads, switches shall have ampere or horsepower ratings or both adequate for loads controlled. (An "AC general use" snap switch may control a motor 2 horsepower or less with full-load current not over 80 per cent of the switch ampere rat- ing.) (f) At least 4 inches of free conductor shall be left at each outlet box except where conductors are intended to loop without joints. (g) Under Chassis Wiring (Exposed to Weather). ARTICLE 551—TRAVEL TRAILERS 70-329 (1) When outdoor or under chassis wiring is exposed to moisture and physical damage it shall be protected by rigid metal conduit or liquid-tight flexible metal conduit, except electrical metallic tubing may be used when closely routed against frames and equipment enclosures. (2) The conductors shall be type NMC,TW,or equivalent. 551-9. Grounding. Grounding of both electrical and non-electrical metal parts in a Travel Trailer is through connection to a grounding bus in the Travel Trailer distribution panel. The grounding bus is grounded through the green-colored conductor in the supply cord or the feeder wiring to the service ground in the service entrance equipment located adjacent to the Travel Trailer location. Neither the frame of the Travel Trailer nor the frame of any appliance may be connected to the neutral conductor in the Travel Trailer. (a) Insulated Neutral. The ground circuit conductor (neutral) shall be insulated from the grounding conductors and from equipment en- closures and other grounded parts. The grounded (neutral) circuit terminals in the distribution panel and in countermounted cooking units are to be insulated from the equipment enclosure. Bonding screws, straps or buses in the distribution panel or in appliances are to be re- moved and discarded. (b) Equipment Grounding Means. (1) The green-colored grounding wire in the supply cord or perma- nent feeder wiring shall be connected to the grounding bus in the dis- tribution panel or disconnecting means. (2) The chassis shall be grounded. The grounding conductor may be solid or stranded, insulated or bare, and shall be an armored grounding conductor or routed in conduit if No. 10 AWG. The con- ductor, if No. 8 AWG stranded or larger, may be run without metal covering. The grounding conductor shall be connected between distribu- tion panel grounding terminal and a terminal on the chassis. Grounding terminals shall be of the solderless type and approved as pressure termi- nal conductors recognized for the wire size employed. The grounding conductors shall be routed so as not to be exposed to physical damage; protection can be afforded by following the configuration of the chassis. (3) In the electrical system, all exposed metal parts, enclosures, frames, lamp fixture canopies, etc., shall be effectively bonded to the grounding terminal or enclosure of the distribution panel. (4) Cord-connected appliances, such as refrigerators, and the electrical system of gas ranges, shall be grounded by means of an ap- proved cord with grounding conductor and grounding type plug. (c) Grounding of Noncurrent-Carrying Metal Parts. All major ex- posed metal parts that may become energized, including the water, gas, and waste plumbing, the roof and outer metallic covering, the chassis and metallic circulating air ducts, shall be effectively bonded to the grounding terminal or enclosure of the distribution panel or to the metal chassis.See Section 551-9 (b) (2). 70-330 NATIONAL ELECTRICAL CODE 551-10. Testing. Dielectric Strength: The wiring of each Travel Trailer shall be capable of withstanding, without breakdown, for a period of 1 minute, the application of an alternating potential of 900 volts between live parts and noncurrent-carrying metal parts. Fixtures or permanently installed appliances shall not be required to withstand the dielectric test if they have been approved. ARTICLE 555—BOAT HARBOR WIRING 555-1. Voltage Drop Requirements. See Section 215-3. 555-2. Branch Circuit and Feeder Calculations. (a) Branch Circuits. Each receptacle outlet for boats shall be on a separate branch circuit having conductors not smaller than No. 12 AWG. (b) Feeder and Service. The ampacity for feeder and service con- ductors supplying floating or permanently supported structures shall be calculated on the basis of a minimum of 25 watts per lineal foot of slip or dock space for boat outlet circuits plus lighting and other loads. Minimum feeder conductor size shall be No. 10 AWG. Minimum serv- ice conductor size shall be No. 8 AWG. 555-3. Wiring Method. The wiring method shall be rigid metal con- duit or rigid nonmetallic conduit. Exception No. 1. Where flexibility is required the wiring method shall be other approved types. Exception No. 2. As permitted in Article 730 for outside branch cir- cuits and feeders. 555-4. Clearance Over Water. Wiring over navigable waterways shall be approved by the authority in charge of the specific waterway. 555-5. Receptacles. Receptacles and matching plugs shall be of the grounding type and have ratings suitable for the purpose. See USA Standard C-73 for recommended configurations. 555-6. Grounding. Metallic raceways and metallic boxes shall not be 11 depended upon for grounding. A continuous insulated copper conduc- tor sized in accordance with Section 250-95, but not smaller than No. 12 AWG, shall be provided for a grounding conductor from outlet boxes to the service ground. 70-331 Chapter 6. Special Equipment ARTICLE 600—ELECTRIC SIGNS AND OUTLINE LIGHTING A. General 600-1. Scope. The provisions of this Article shall apply to the in- stallation of conductors and equipment for electric signs and outline lighting as defined in Article 100. 600-2. Disconnect Required. Each outline lighting installation, and each sign of other than the portable type, shall be controlled by an ex- ternally operable switch or breaker which will open all ungrounded conductors and shall be suitable for conditions of installation, such as exposure to the weather. (a) In Sight of Sign. The switch or breaker required by Section 600-2 shall be within sight of the sign or outline lighting which it con- trols or may be located elsewhere when capable of being locked in the open position. (b) Control Switch Rating. Switches, flashers, and similar devices controlling transformers shall be either of a type approved for the pur- pose, or have a current rating not less than twice the current rating of the transformers. On alternating-current circuits, general use alternat- ing-current snap switches may be used to control inductive loads other than motors, not exceeding the ampere rating of switch. See Section 380-14. 600-5. Grounding. (a) Signs, troughs, tube terminal boxes and other metal frames shall be grounded in the manner specified in Article 250 of this Code, unless they are insulated from ground and from other conducting surfaces and are inaccessible to unauthorized persons. (b) Isolated noncurrent-carrying metal parts of outline lighting may be bonded by No. 14 conductors and grounded in accordance with Article 250. (c) Signs of the portable incandescent or fluorescent-lamp type in which the open circuit voltage does not exceed 150 volts to ground are not required to be grounded. 600-6. Load of Branch Circuit. Circuits shall be so arranged that the load imposed by outlets, lamps, and transformers connected to them, shall in no case exceed the rating of the branch circuit. Circuits which supply lamps, ballasts, and transformers or combina- tions thereof may be rated not to exceed 20 amperes. Circuits containing electric discharge lighting transformers exclusively shall not be rated in excess of 30 amperes. 70-332 NATIONAL ELECTRICAL CODE 600-7. Marking. (a) Signs shall be marked with the maker's name, and for incan- descent-lamp signs with the number of lampholders, and for electric discharge signs with input amperes at full load and input voltage. The marking of the sign shall be visible for inspection after installation. (b) Transformers shall be marked with the maker's name, and trans- formers for electric discharge signs shall be marked with the input rating in amperes or volt-amperes, the input voltage and the open-cir- cuit high-tension voltage. 600-8. Enclosures. Enclosures for signs and outline lighting shall con- form to the following: (a) Conductors and Terminals. Conductors and terminals in sign boxes, cabinets, and outline troughs shall be enclosed, except the sup- ply leads. (b) Cutouts, Flashers, Etc. Cutouts, flashers, and similar devices shall be enclosed in metal boxes the doors of which shall be arranged so that they can be opened without removing obstructions or finished parts of the enclosure. (c) Strength. Enclosures shall have ample strength and rigidity. (d) Material. Except for portable signs of the indoor type, signs and outline lighting shall be constructed of metal or other noncombus- tible material. Wood may be used for external decoration if placed not less than 2 inches from the nearest lampholder or current-carrying part. (e) Minimum Thickness — Enclosure Metal. Sheet copper shall be at least 20 ounce (0.028 inch). Sheet steel may be of No. 28 USS gage (.0149 inch) except that for outline lighting and for electric discharge signs sheet steel shall be of No.24 USS gage(.0239 inch),unless ribbed, corrugated or embossed over its entire surface, when it may be of No. 26 USS gage (.0179 inch). (f) Protection of Metal. All steel parts of enclosures shall be gal- vanized or otherwise protected from corrosion. (g) Enclosures Exposed to the Weather. Enclosures for outside use shall be weatherproof and shall have an ample number of drain holes, each not larger than 1/2 inch or smaller than 1/4 inch.Wiring connections shall not be made through the bottoms of enclosures exposed to the weather unless the enclosures are of the raintight type. B. Signs and Outline Lighting—600 Volts or Less 600-21. Installation of Conductors. Conductors shall be installed as follows: (a) Wiring Method. Conductors shall be installed as open conduc- tors on insulators, in rigid metal conduit, flexible metal conduit, elec- trical metallic tubing, metal-clad cable, metal troughing, Type ALS cable or Type MI cable. (b) Insulation and Size. Conductors shall be of a type approved for general use and shall be no smaller than No. 14. ARTICLE 600—ELECTRIC SIGNS 70-333 Exception No. 1. Conductors in portable signs, short leads perma- nently attached to lampholders or ballasts, and leads in wiring chan- nels which are permanently attached to electric discharge lampholders or electric discharge ballasts and which are not longer than 8 feet may be smaller than No. 14 but shall not be smaller than No. 18 and shall be of a type approved for the purpose. Exception No. 2. Conductors, for signs with multiple incandescent lamps requiring one conductor from a control to one or more lamps whose total load does not exceed 250 watts, may be smaller than No. 14 but shall not be smaller than No. 18 if in an approved cable assem- bly of two or more conductors. (c) Exposed to the Weather. Conductors in raceways, armored ca- ble or enclosures exposed to the weather, shall be of the lead-covered type or other type specially approved for the conditions, except where rigid conduit, electrical metallic tubing or enclosures are made raintight and arranged to drain. (d) Number of Conductors in Raceway. Number of conductors in raceway for sign flashers may be in accordance with Table 1 of Chap- ter 9. (e) Open Conductors. Open conductors on insulators shall comply with the provisions of Sections 300-2 to 300-22 inclusive, and, if out- doors, Article 730, except that the separation between conductors need be only 2 inches. Exception: Open conductors may be supported by lampholders lo- cated not more than 1 foot apart. (f) Conductors Soldered to Terminals. Where the conductors are fastened to lampholders other than of the pin type, they shall be sol- dered to the terminals and the exposed parts of conductors and termi- nals shall be treated to prevent corrosion. Where the conductors are fastened to pin-type lampholders which protect the terminals from the entrance of water, and which have been found acceptable for sign use, the conductors shall be of the stranded type but need not be soldered to the terminals. 600-22. Lampholders. Lampholders shall be of the unswitched type having bodies of suitable insulating material and shall be so constructed and installed as to prevent turning. Miniature lampholders shall not be employed for outdoor signs and outline lighting. C. Signs and Outline Lighting—Exceeding 600 Volts 600-31. Installation of Conductors. Conductors shall be installed as follows: (a) Wiring Method. Conductors shall be installed as open work, as concealed conductors on insulators, in rigid or flexible metal conduit, or in electrical metallic tubing. (b) Insulation and Size. Conductors shall be of a type approved for the purpose and for the voltage of the circuit and shall be not smaller than No. 14. 70-334 NATIONAL ELECTRICAL CODE Exception No. 1. Leads in wiring channels which are permanently attached to electric discharge lampholders or electric discharge ballasts and which are not longer than 8 feet may be smaller than No. 14 but shall not be smaller than No. 18 and shall be of a type approved for the purpose. Exception No. 2. Leads in show-window displays or small portable signs that run from the line ends of the tubing to the secondary wind- ings of the transformer where they are permanently attached within the transformer enclosure and which are not longer than eight (8) feet may be smaller than No. 14, but shall not be smaller than No. 18 and shall be of a type approved for the purpose. (c) Bends in Conductors. Sharp bends in the conductors shall be avoided. (d) Open Conductors — Indoors. Open conductors indoors shall be mounted on noncombustible, nonabsorptive insulators. Insulators of porcelain shall be glazed on all exposed surfaces. A separation of at least 11/2 inches shall be maintained between conductors and between conductors and other objects. Conductors shall not be located where subject to physical damage. (e) Concealed Conductors on Insulators — Indoors. Concealed con- ductors on insulators shall be separated from each other and from all objects other than the insulators on which they are mounted by a spac- ing of not less than 11/2 inches for voltages above 10,000 volts, and not less than 1 inch for voltages of 10,000 or less. They shall be in- stalled in channels lined with noncombustible material and used for no other purpose, except that the primary circuit conductors may be in the same channel. The insulators shall be of noncombustible, nonab- sorptive material. (f) Conductors in Raceways. Where the conductors are covered with lead or other metal sheathing, the covering shall extend beyond the end of the raceway, and the surface of the cable shall not be injured where the covering terminates. (1) In damp or wet locations, the insulation on all conductors shall extend beyond the metal covering or raceway at least 4 inches for voltages over 10,000, 3 inches for voltages over 5,000 but not exceed- ing 10,000,and 2 inches for voltages of 5,000 or less. (2) In dry locations the insulation shall extend beyond the end of the metal covering or raceways not less than 21/2 inches for voltages over 10,000, 2 inches for voltages over 5,000 but not exceeding 10,000, and 11/2 inches for voltages of 5,000 or less. (3) For conductors at grounded midpoint terminals, no spacing is required. (4) A metal raceway containing a single conductor from one sec- ondary terminal of a transformer shall not exceed twenty feet in length. (g) Open Conductors — Outdoors. Open conductors outdoors shall be mounted on noncombustible, nonabsorptive insulators. Insulators of porcelain shall be glazed on all exposed surfaces. A separation of at least two inches shall be maintained between conductors, and between conductors and other objects. ARTICLE 600—ELECTRIC SIGNS 70-335 Where subject to physical damage, or where within reach from ground, roof, or window, conductors shall be enclosed in raceways or suitably guarded. Where guarded, a spacing of not less than 11/2 inches shall be maintained between conductors and the enclosure un- less the enclosure is nonconducting and noncombustible. (h) Show Windows and Similar Locations. Conductors that hang freely in the air, away from combustible material, and where not sub- ject to physical damage, as in some show-window displays, need not be otherwise protected. (i) Conductors may be run from the ends of tubing to the grounded midpoint of transformers specifically designed for the purpose and provided with terminals at the midpoint. Where such connections are made to the transformer grounded midpoint, the connections be- tween the high-voltage terminals of the transformer and the line ends of the tubing shall be as short as possible. 600-32. Transformers. Transformers shall comply with the following: (a) Voltage. The transformer secondary open-circuit voltage shall not exceed 15,000 volts with an allowance on test of 1000 volts addi- tional. In end-grounded transformers the secondary, open-circuit volt- age shall not exceed 7,500 volts with an allowance on test of 500 volts additional. (b) Type. Transformers shall be of a type approved for the pur- pose and shall be limited in rating to a maximum of 4,500 volt-amperes. Open core-and-coil type transformers shall be limited to 5,000 volts with an allowance on test of 500 volts, and to indoor applications in small portable signs. Transformers for outline lighting installations shall have secondary current ratings not in excess of 30 milliamperes except where they and all wiring connected to them are installed in accordance with the pro- visions of Article 410 for electric discharge lighting of the same voltage. (c) Exposed to Weather. Transformers used outdoors shall be of the weatherproof type or shall be protected from the weather by en- closure in the sign body or in a separate metal box. (d) Transformer Secondary Connections. The high-voltage windings of transformers shall not be connected in parallel; and Shall not be con- nected in series, except that two transformers each having one end of its high-voltage winding connected to the metal enclosure may have their high-voltage windings connected in series to form the equivalent of a midpoint grounded transformer. The grounded ends shall be con- nected by insulated conductors not smaller than No. 14. Exception: Transformers for small portable signs, show windows, and similar locations that are equipped with leads permanently attached to the secondary winding within the transformer enclosure and that do not extend more than eight (8) feet beyond the enclosure for attach- ing to the line ends of the tubing may have leads smaller than No. 14, but shall not be smaller than No. 18 and shall be of a type approved for the purpose. 70-336 NATIONAL ELECTRICAL CODE (e) Accessibility. Transformers shall be accessible. 600-33. Electric Discharge Tubing. Electric discharge tubing shall con- form to the following: (a) Design. The tubing shall be of such length and design as not to cause a continuous over-voltage on the transformer. (b) Support. Tubing shall be adequately supported on noncombus- tible, nonabsorptive supports. Tubing supports should, where practi- cable,be adjustable. (c) Contact with Flammable Material and Other Surfaces. The tub- ing shall be free from contact with flammable material and shall be located where not normally exposed to physical damage.Where operat- ing in excess of 7,500 volts, the tubing shall be supported on noncom- bustible, nonabsorptive, insulating supports which maintain a spacing of not less than V4 inch between the tubing and the nearest surface. 600-34. Terminals and Electrode Receptacles for Electric Discharge Tub- ing. Terminals and electrode receptacles for electric discharge tub- ing shall comply with the following: (a) Terminals. Terminals of the tubing shall be inaccessible to un- qualified persons and isolated from combustible material and grounded metal or shall be enclosed. Where enclosed they shall be separated from grounded metal and combustible material by noncombustible, nonab- sorptive, insulating material approved for the purpose or by 11/2 inches of air. Terminals shall be relieved from stress by the independent sup- port of the tubing. (b) Tube Connections Other Than With Receptacles. Where tubes do not terminate in receptacles designed for the purpose, all live parts of tube terminals and conductors shall be so supported as to maintain a separation of at least 11/2 inches between conductors or between con- ductors and any grounded metal. (c) Receptacles. Electrode receptacles for the tubing shall be of noncombustible, nonabsorptive insulating material approved for the purpose. (d) Bushings. Where electrodes enter the enclosure of outdoor signs or of an indoor sign operating at a voltage in excess of 7,500 volts, bushings shall be used unless receptacles are provided or the sign is wired with bare wire mounted on approved supports which maintain the tubing in proper position. Bushings shall be of noncombustible, nonabsorptive material. Where bare wiring is used, the conductor shall be not less than No. 14 solid copper, shall be supported so as to prevent sagging and lessening of the spacing required elsewhere in this Article, and electrode terminal assemblies shall be of an approved type and sup- ported not more than 6 inches from the electrode terminals. (e) Show Windows. In the exposed type of show-window signs, terminals shall be (1) enclosed by receptacles approved for the purpose or (2) where hanging in air, free from grounded surfaces, enclosed in sleeves of vulcanized fiber, phenolic composition, or other suitable ma- terial which overlaps all live parts by at least 1/2 inch. ARTICLE 610—CRANES AND HOISTS 70-337 (f) Receptacles and Bushing Seals. A flexible, nonconducting seal may be used to close the opening between the tubing and the recep- tacle or bushing against the entrance of dust or moisture. This seal shall not be in contact with grounded conductive material and shall not be depended upon for the insulation of the tubing. (g) Enclosures of Metal. Enclosures of metal for electrodes shall be of not less than No.24 USS gage (.0239 inch) sheet metal. (h) Enclosures of Insulating Material. Enclosures of insulating ma- terial shall be noncombustible, nonabsorptive and approved for the voltage of the circuit. 600-35. Switches on Doors. Doors or covers giving access to unin- sulated parts of indoor signs or outline lighting exceeding 600 volts and accessible to the general public, shall either be provided with in- terlock switches which on the opening of the doors or covers discon- nect the primary circuit, or shall be so fastened that the use of the other than ordinary tools will be necessary to open them. ARTICLE 610—CRANES AND HOISTS A. Scope and Use 610-1. Scope. The provisions of this Article shall apply to the installa- tion of cranes, crane runways, hoists, and monorails, and shall be addi- tional to, or amendatory of, the requirements prescribed in Articles 100 to 480,inclusive,of this Code. For definition of various kinds of cranes and hoists see American Standard Safety Code for Cranes,Derricks,and Hoists,ASA B30.2-1943. 610-2. Particular Locations. (a) Ignitible Material Hazards. Installations in hazardous locations shall comply with the provisions of Section 503-13. (b) Combustible Materials. Where a crane operates over readily combustible material, the resistors shall be placed in a well-ventilated cabinet composed of noncombustible material so constructed that it will not emit flames or molten metal. Exception: Resistors may be located in a cage or cab constructed of noncombustible material which encloses the sides of the cage or cab from the floor to a point at least 6 inches above the top of the resistors. B. Wiring 610-11. Wiring Method. Conductors shall be enclosed in raceways or be Type ALS cable or Type MI cable. Exception No. 1. Bare Conductors. Bare conductors used as contact conductors. Exception No. 2. Open Conductors. Short lengths of open conduc- tors at resistors,collectors,and other equipment. 70-338 NATIONAL ELECTRICAL CODE Exception No. 3. Flexible Connections. Where flexible connections are necessary to motors and similar equipment, flexible metal conduit, liquidtight flexible metal conduit, metal-clad cable, multiple conductor rubber-covered cable or an approved nonmetallic enclosure may be employed. Exception No. 4. Pendant Push-Button Stations. Where multiple conductor cable is used with a suspended push-button station, the sta- tion must be supported in some satisfactory manner that will protect the electrical conductors against strain. 610-12. Raceway Terminal Fittings. Conductors leaving raceways shall comply with the provisions of Section 300-16. 610-13. Types of Conductors. Conductors shall be of the rubber-cov- ered or the thermoplastic type except: Exception No. 1.Contact Conductors. Contact conductors along run- ways, crane bridges and monorails may be bare and may be of hard drawn copper, or aluminum, or steel in the form of tees, angles, tee rails,or other stiff shapes. Exception No. 2. Flexible Conductors. Flexible conductors may be used to convey current and where practicable, cable reels or take-up devices may be employed. Exception No.3. Varnished Cambric Conductors. Varnished-cambric conductors (Type V) or asbestos varnished cambric (Types AV and AVB) may be used in dry locations. Exception No.4. Type MI Cable. Type MI cable may be used in wet or dry locations within its specified temperature ratings. Exception No. 5. Exposed to High Temperatures. Conductors ex- posed to external heat or connected to resistors shall have an insulation approved for the temperature and location as specified in Section 310-2. Where conductors not having a flame-resistant outer covering are grouped together,the group shall be covered with a flame-resistant tape. 610-14. Conductors (a) Ampacity. The allowable ampacities of conductors shall be as shown in Table 610-14(a). For the ampacities of conductors between controllers and resistors,see Section 430-23. (b) Minimum. Conductors shall not be smaller than No. 14. Exception: No. 16 may be used for crane and hoist motor and con- trol circuits only when the application meets Section 610-14(a) am- pacity,and provided the conductors are protected against physical dam- age. (c) Contact Conductors. The size of contact wires shall be not less than the following: Distance between end Size of strain insulators wire 0-30 feet No. 6 31-60 feet No. 4 over 60 feet No. 2 ARTICLE 610—CRANES AND HOISTS 70-339 O• a Q U 4+ C 00v,0 ,, l-000' V'-m0 '0 NO,DOV O fa, E ' t O00 ONV,DO,r, QAm,-+7 OO'nmO W •�N Nm7V v,N00000,0 N.r Q M C r N U Qo .0•^ h F M C oov,Om m0„Ovnml� O,v,O,N NV,O,OOv, �' tU. m t,0N O,ON ,ON mNm,n 7,n.-+,0 7"" , 0) C .-� ,--, NNmm V vi'0 O N 00 0 ( cn cc� 00 0 y * o w a3 = 2 x and-,,,'0 O�,Omv'r-0N, oCrO ,.0mD,O0,m0� U M . • ` ax O . - ,-• NNmm -'0N -000, O ❑ u 0 wX E o U wz m c �� R w • N a_ w F 30 p a w= 7Q .--„OO,m mv-,.-.-,0000 ..,n on O� Or-Nm OHO Y U u E-� C mm7,0 000,r.m�v, VO.-, OO,V0,DN _ 4 a'a Q 0 NNmm V V w-or F•, LK C C T� C4 al C a N . Eo a y a Y w a o o 0) o u 3 .5 = o _0 N,OmmO '0 t N.-.Ov, mN-,O. ON'000v,N E N x .--�Nm V,O 00 O..-- 'ON m0OV'O N00 t000D� •O E 3x 0 • , •-� NNmm 7vl,O,D N00 O 0 O 0 --r " WOW xk 0 .O -a 0 U R.'Z '0) C F 6 E ax >• f 7 +• 6 C w M Y • 0 F3 E O, 0o,, ,D,n00t-m ONOO Vv,0000OO ,Nm7rv, [-00ONm� O,N00O ‘Dv,00mO,D .4.4.01 x O .--� .. N N m m V V v,,D,O '0 O s F cC •0 i•. m d N o• ,n 5. c+, 0 c+, E E 000 v,O CO hv,OO O,n OO v,v,OO OO 00 y Q NNmv N000 .-+rn 00NNm m7r,roo'O O� NNM m r V ON U �g as U F V) o F 0 �V] a g F .. n... EOO,,nv, Nv,NCNC Ov,0 0 OOO,nv,O 0—U O •--NNm7 v,,Or-OOOm ,00,70, v-, ,0-,0N ..7r o o -- ,-,NN m7'C',v,,O ".-w a. •OVD N M ct,4;AOU a 0p nz-. h OF° N.0 ,07NOoo ,0.- mN.r 0000 000000 •� _O'B co Ov-,O v,O 0 ca op C Q •--�•--�•-• 0 0 N cm m V V v, y• cdO '0C �w o oHi- 70-340 NATIONAL ELECTRICAL CODE (d) Calculation of Motor Load. The ampacity of the power supply conductors on the crane shall be not less than the combined short time full load ampere rating of the largest motor or group of motors for any single crane motion plus 50 per cent of the combined short time full load ampere rating of the next largest motor or group of motors. (e) Other Loads. Additional loads, such as heating, lighting, and air conditioning, shall be provided for by application of the appropriate sections of this Code. 610-15. Common Return. Where a crane or hoist is operated by more than one motor, a common-return conductor of proper ampacity may be used. C. Contact Conductors 610-21. Installation of Contact Conductors. Bare contact conductors shall conform to the following: (a) Contact Wires. Wires that are used as contact conductors shall be secured at the ends by means of approved strain insulators and shall be so mounted on approved insulators that the extreme limit of displace- ment of the wire will not bring the latter within less than 11/2 inches from the surface wired over. (b) Supports Along Runways. Main contact conductors carried along runways shall be supported on insulating supports placed at in- tervals not exceeding 20 feet, and these supports shall be insulating except for grounded rail conductors as provided in Section 610-21(e). Such conductors shall be separated not less than 6 inches except for monorail hoists where a spacing of not less than 3 inches may be used. Where necessary, intervals between insulating supports may be in- creased up to 40 feet, the separation between conductors being in- creased proportionately. (c) Supports on Bridges. Bridge contact conductors shall be kept at least 21 inches apart and, where the span exceeds 80 feet, insulating saddles shall be placed at intervals not exceeding 50 feet. It is recommended that the distance between wires be greater than 21/2 inches where practicable. (d) Supports for Rigid Conductors. Conductors along runways and crane bridges, which are of the rigid type specified in Section 610-13, Exception No. 1, shall be carried on insulating supports spaced at in- tervals of not more than 80 times the vertical dimension of the conduc- tor, but in no case greater than 15 feet, and spaced apart sufficiently to give a clear electrical separation of conductors or adjacent collectors of not less than 1 inch. Hardwood supports covered with, or impregnated with, insulating paint shall be acceptable insulators. (e) Track as Circuit Conductor. Monorail, tramrail or crane-runway tracks may be used as a conductor of current for one phase of a three- phase alternating-current system furnishing power to the carrier, crane or trolley,provided all of the following conditions are fulfilled: (1) The conductors for supplying the other two phases of the power supply shall be insulated. ARTICLE 610—CRANES AND HOISTS 70-341 (2) The power for all phases shall be obtained from an insulating transformer. (3) The voltage shall not exceed 300 volts. (4) The rail serving as a conductor shall be effectively grounded at the transformer and may also be grounded by the fittings used for the suspension or attachment of the rail to a building or structure. (f) Electrical Continuity of Contact Conductors. All sections of bare rigid contact conductors shall be mechanically joined to provide a con- tinuous electrical connection. (g) Not to Supply Other Equipment. Contact conductors shall not be used as feeders for any equipment other than the crane or cranes which they are primarily designed to serve. (h) Locating or Guarding Contact Conductors. Contact conductors shall be located or guarded in such a manner that unqualified persons cannot inadvertently touch energized current-carrying parts. 610-22. Collectors. Collectors shall be so designed as to reduce to a minimum sparking between them and the contact conductor, and when operated in rooms used for the storage of easily ignitible combustible fibers and materials the requirements of Section 503-13 shall be com- plied with. D. Control 610-31. Runway Conductor Disconnecting Means. A disconnecting means shall be provided between the runway contact conductors and the power supply. Such disconnecting means shall consist of a motor- circuit switch or circuit breaker, except that a general-use switch may be used when the disconnecting means is provided in accordance with Section 610-32. This disconnecting means shall be readily accessible and operable from the ground, shall be arranged to be locked in the open position, shall open all ungrounded conductors simultaneously, and shall be placed within sight of the crane or hoist and the runway contact conductors. 610-32. Disconnecting Means for Crane. A motor-circuit switch or cir- cuit breaker shall be provided in the leads from the runway contact conductors on all bridge cranes. Where this disconnecting means is not readily accessible from the crane operating station, means shall be pro- vided at the crane operating station to open the power circuit to the crane motors. 610-33. Rating of Disconnecting Means for Crane. On both alternat- ing-current and direct-current crane protective panels, the continuous ampacity of the switch or circuit breaker required by Section 610- 32, and mainline contactors, shall be not less than 50 per cent of the combined short-time ampacities of the motors, nor less than 75 per cent of the sum of the short-time ampacities of the motors required for any single crane motion. 610-34. Limit Switch. A limit switch shall be provided for upper limit of travel of crane hoists. 70-342 NATIONAL ELECTRICAL CODE E. Overcurrent Protection 610-41. Contact Conductors. The main contact conductors shall be protected by an overcurrent device. 610-42. Crane Motors. Where more than one motor is employed on a crane, each motor shall have individual overcurrent protection as provided in Article 430, except that where two motors operate a single hoist,carriage, truck, or bridge, and are controlled as a unit by one con- troller, the pair of motors with their leads may be protected by a single overcurrent device. F. Grounding 610-51. Grounding. All exposed metal parts of cranes, hoists, and accessories, including pendant controls, shall be metallically joined to- gether into a continuous electrical conductor so that the entire crane or hoist will be grounded on installation in accordance with Article 250. Moving parts, other than removable accessories or attachments having metal-to-metal bearing surfaces, i.e., such as bridge wheels running on a track, shall be considered to be electrically connected to each other through the bearing surfaces for grounding purposes. ARTICLE 620—ELEVATORS, DUMBWAITERS, ESCALATORS, AND MOVING WALKS A. Scope and General 620-1. Scope. This Article shall apply to electrical equipment and wiring used in connection with elevators, dumbwaiters, escalators, and moving walks. 620-2. Voltage Limitations. The nominal voltage used for elevator, dumbwaiter, escalator, and moving walk operating control and signal circuits, operating equipment, driving machine motors, machine brakes, and motor-generator sets shall not exceed the following: (a) For operating control and signal circuits and related equipment including door operator motors: 300 volts except that higher potentials may be used for frequencies of 25 through 60 cycles alternating cur- rent or for direct current provided the current in the system cannot, under any conditions, exceed 8 milliamperes for alternating current or 30 milliamperes for direct current. (b) Driving machine motors, machine brakes, and motor-generator sets: 600 volts, except that higher potentials may be used for driving motors of motor-generator sets. 620-3. Live Parts Enclosed. All live parts of electrical apparatus in the hoistways, at the landings, or in or on the cars of elevators and dumb- waiters or in the wellways or the landings of escalators or moving walks shall be enclosed to protect against accidental contact. ARTICLE 620—ELEVATORS, DUMBWAITERS 70-343 B. Conductors 620-11. Insulation of Conductors. The insulation of conductors in- stalled in connection with elevators, dumbwaiters, escalators and mov- ing walks,shall comply with the following: (a) Control Panel Wiring. Conductors from panels to main circuit resistors shall be flame-retardant and suitable for a temperature of not less than 90°C. (194°F.) All other wiring on control panels shall be flame-retardant,moisture-resistant. (b) Traveling Cables. Traveling cables used as flexible connections between the elevator or dumbwaiter car and the raceway shall be Type E,EN,EO,ET,or ETP elevator cable or other approved types and shall have a flame-retardant,moisture-resistant outer covering. (c) Other Wiring. All conductors in the raceways and in or on the cars of elevators and dumbwaiters and in the wellways of escalators and moving walks and in the machine room of elevators, dumbwaiters, escalators and moving walks shall have flame-retardant and moisture- resistant insulation. (d) Thickness of Insulation. The thickness of the insulation of all conductors shall be suitable for the voltage to which the conductors are subjected. 620-12. Minimum Size of Conductors. The minimum size of conduc- tors used for elevator, dumbwaiter, escalator, and moving walk wiring, except for conductors which form an integral part of control equip- ment,shall be as follows: (a) Traveling Cables. (1) For lighting circuits: No. 14, except that No. 20 or larger con- ductors may be used in parallel provided the ampacity is equivalent to at least that of No. 14 wire. (2) Operating control and signal circuits: No. 20. (b) Other Wiring. All operating control and signal circuits: No.20. 620-13. Motor Circuit Conductors. Conductors supplying elevator, dumbwaiter, escalator, or moving walk motors shall have an ampacity conforming to (a), (b) and (c) below based on the nameplate current rating of the motors. With generator field control, the ampacity shall be based on the nameplate current rating of the driving motor of the motor-generator set which supplies power to the elevator motor. The heating of conductors depends on root mean square current values which, with generator field control, are reflected by the nameplate current rating of the motor-generator set driving motor rather than by the rating of the elevator motor which represents actual but short time and intermittent full-load current values. (a) Conductors Supplying a Single Motor. Conductors supplying a single motor shall have an ampacity in conformance with Section 430- 22,Table 430-22 (a-Exception). (b) Conductors Supplying Several Motors. Conductors supplying several motors shall have an ampacity of not less than 125 per cent of the nameplate current rating of the highest rated motor in the group 70-344 NATIONAL ELECTRICAL CODE plus the sum of the nameplate current ratings of the remainder of the motors in the group. (c) Feeder Demand Factor. Feeder conductors of less capacity than required by (b) above may be furnished subject to the requirements of Section 430-26. C. Wiring 620-21. Wiring Methods. Conductors located in hoistways and esca- lators and moving walk wellways, in or on cars and machine and con- trol rooms, not including the traveling cables connecting the car and hoistway wiring, shall be installed in rigid conduit, electrical metallic tubing, metal wireways, Type ALS cable or Type MI cable subject to the following exceptions: Exception No. 1. Flexible conduit or Type AC metal-clad cable may be used in hoistways and in escalator and moving walk wellways be- tween risers and limit switches, interlocks, operating buttons, and sim- ilar devices. Exception No. 2. Short runs of flexible conduit or Type AC metal- clad cable may be used on cars where so located as to be free from oil and if securely fastened in place. Exception No. 3. Types S, SO, and ST cords may be used as flexible connections between the fixed wiring on the car and the switches on car doors or gates. Exception No. 4. Conductors between control panels and machine motors, machine brakes, and motor generator sets, not exceeding six feet in length, may be grouped together and taped or corded without being installed in a raceway provided the taping or cording is painted with an insulating paint. Such cable groups shall be supported at inter- vals of not more than three feet and so located as to be free from phys- ical damage. Where motor generators and machine motors are located adjacent to or underneath control equipment, and are provided with extra length terminal leads not exceeding six feet in length, such leads may be ex- tended to connect directly to controller terminal studs without regard to the carrying capacity requirements of Articles 430 and 445. Auxili- ary gutters may be used in machine and control rooms between con- trollers,starters and similar apparatus. D. Installation of Conductors 620-31. Raceway Terminal Fittings. Conductors leaving raceways shall comply with the provisions of Section 300-16. In no case shall the raceway terminate less than 6 inches from the floor. 620-32. Metal Wireways. Section 362-5 shall not apply to wireways. The sum of the cross sectional area of the individual conductors in a metallic wireway shall not be more than 50 per cent of the interior cross sectional area of the wireway. Vertical runs of wireways shall be securely supported at intervals not exceeding 15 feet and shall have not more than one joint between sup- ARTICLE 620—ELEVATORS, DUMBWAITERS 70-345 ports. Adjoining wireway sections shall be securely fastened together to provide a rigid joint. 620-33. Number of Conductors in Other Raceways. The number of operating and control circuit conductors in other raceways may be in accordance with Table 1 of Chapter 9. 620-34. Supports. Supports for Type ALS cable or conductor race- ways in the hoistway or escalator or moving walk wellway shall be se- curely fastened to the guide rail or to the hoistway or wellway con- struction. 620-35. Auxiliary Gutters (Wiring Troughs). Auxiliary gutters shall not be subject to the restrictions of Section 374-2 as to length or of Sec- tion 374-5 as to number of conductors. 620-36. Different Systems in One Raceway or Traveling Cable. Con- ductors for operating, control, power, signal, and light circuits of 600 volts or less may be run in the same traveling cable or raceway sys- tem provided that all conductors are insulated for the maximum voltage found in the cables or raceway system and all live parts of the equip- ment are insulated from ground for this maximum voltage. Such a trav- eling cable or raceway may also include a pair of telephone conduc- tors for the car telephone provided such conductors are insulated for the maximum voltage found in the cable or raceway system. 620-37. Foreign Wires. Main feeders for supplying power to elevators and dumbwaiters shall be installed outside the hoistway, except in exist- ing structures subject to special permission of the enforcing authority. Only such electrical wiring, conduit and cable used directly in connec- tion with the elevator or dumbwaiter, including wiring for signals, for communication with the car, for lighting and ventilating the car and wiring for low voltage fire detecting systems for the hoistways, may be installed inside the hoistway. E. Traveling Cables 620-41. Suspension. Traveling cables shall be so suspended at the car and hoistway end as to reduce the strain on the individual copper con- ductors to a minimum. Cables exceeding 100 feet in length and which have steel support- ing fillers shall be suspended directly by the steel supporting fillers. Where nonmetallic fillers are used, the cables shall be suspended by looping the cables around the supports. 620-42. Hazardous Locations. In hazardous locations, traveling ca- bles shall be Type EO and shall be secured to explosion proof cabi- nets by heavy-duty rubber-bushed threaded connector bushings sealed off at the enclosure as provided in Section 501-5. 620-43. Location of and Protection for Cables. Traveling cable sup- ports shall be so located as to reduce to a minimum the possibility of damage due to the cables coming in contact with the hoistway construc- tion or equipment in the hoistway. Where necessary, suitable guards shall be provided to protect the cables against damage. 70-346 NATIONAL ELECTRICAL CODE F. Control 620-51. Disconnecting Means. There shall be in addition to the ele- vator controller, a means for disconnecting all conductors of the cir- cuit to the elevator motor, or in the case of generator field control, to the motor of the motor-generator set which supplies current to the ele- vator motor. (a) Type. The disconnecting means shall be an enclosed externally operable motor circuit switch or circuit breaker arranged to be locked in the open position. (b) Location. It shall be located adjacent to and be visible from the elevator machine, unless a disconnect switch in the control circuit of the motor-generator set is placed adjacent to and is visible from the elevator machine. 620-52. Electrical Equipment in Garages and Similar Occupancies. Electrical equipment and wiring used for elevators, dumbwaiters, es- calators, and moving walks in garages shall conform to the require- ments of Article 511. Wiring and equipment located under the car plat- form shall be considered as being located in the hazardous area. 620-53. Phase Protection. Elevators driven by polyphase alternating current machine motors shall be provided with means to prevent start- ing of the elevator motor when: (a) The phase rotation is in the wrong direction,or (b) There is a failure in any phase. G. Overcurrent Protection 620-61. Overcurrent Protection. Overcurrent protection shall be pro- vided as follows: (a) Control and Operating Circuits. Control and operating circuits and signal circuits shall be protected against overcurrent in accordance with the requirements of Section 725-18. (b) Motors. (1) Duty on elevator and dumbwaiter driving machine motors and driving motors of motor generators used with generator field control shall be classed as intermittent. Such motors shall be protected against overcurrent in accordance with Section 430-33. (2) Duty on escalator and moving walk driving machine motors shall be classed as continuous. Such motors shall be protected against overcurrent in accordance with Section 430-32. (3) Elevator, dumbwaiter, escalator, and moving walk driving ma- chine motors and driving motors of motor generator sets shall be pro- tected against running overcurrent as provided in Table 430-37, except that no more than two overcurrent protective units shall be required. H. Machine Room 620-71. Guarding Equipment. Elevator, dumbwaiter, escalator, and moving walk driving machines, motor generator sets, controllers and auxiliary control equipment shall be installed in a space secured against unauthorized access. ARTICLE 620—ELEVATORS, DUMBWAITERS 70-347 Such equipment may be located in rooms or spaces containing other equipment essential to the operation of the building provided it is sepa- rated therefrom by a substantial metal grill enclosure of a design which will reject a ball two inches in diameter and is at least six feet high equipped with a self-closing and self-locking door. It is not intended to prohibit the installation of dumbwaiter, esca- lator, or moving walk controllers outside the spaces herein specified, provided they are enclosed in cabinets with doors or removable panels capable of being locked in the closed position; nor is it intended to pre- vent the installation of dumbwaiter controllers within the hoistway without cabinets, provided removable or hinged panels capable of be- ing locked in the closed position are installed in the hoistway enclo- sures to provide access to the controllers. 620-72. Clearance Around Control Panels. There shall be provided sufficient clear working space around control panels to provide safe and convenient access to all live parts of the equipment necessary for maintenance and adjustment. The minimum clear working space about live parts on control panels shall not be less than set forth in Section 620-72(a and b) unless otherwise specified. (a) Elevator and Dumbwaiter Panels. (1) In the front-30 inches to live panel parts. (2) In the rear-24 inches to live panel parts. (3) On one side of a panel or a group of panels-18 inches except this clearance can be waived if there is a clear passageway, not less than 18 inches wide at any point, from the front to the rear of the panel or panels. It shall be permissible to mount control panels on, over or against the hoisting machine or motor generator set or to place auxiliary control equipment in the front or rear of control panels provided the clearances to the live parts are not less than specified and provided there is safe ac- cess to the front and/or back of the controller from at least one side. Where control panels are mounted in cabinets with swing doors or removable panels, sufficient clear space shall be provided to fully open the doors or remove the panels. (b) Escalator and Moving Walk Control Panels. The minimum working clearance for escalator and moving walk control panels shall be as specified in Section 620-72(a) provided that where the control panel is mounted in the same space as the escalator or moving walk drive machine and the clearances specified cannot be provided, they may be waived where the entire panel is arranged so that it can be read- ily removed from the machine space and is provided with flexible leads to all external connections. Where control panels are not located in the same space as the drive machine they shall be so located in cabinets with doors or removable panels capable of being locked in the closed position. Such cabinets may be mounted in the balustrading on the side away from the moving steps or moving treadway. 70-348 NATIONAL ELECTRICAL CODE J. Grounding 620-81. Metal Raceways Attached to Cars. Conduit, Type ALS cable or Type AC metal-clad cable attached to elevator cars shall be bonded to grounded metal parts of the car with which they come in contact. 620-82. Electric Elevators. For electric elevators, the frames of all mo- tors, elevator machines, controllers and the metal enclosures for all electrical devices in or on the car or in the hoistway shall be grounded. 620-83. Nonelectric Elevators. For elevators other than electric, when any electrical conductors are attached to the car, the metal frame of the car,where normally accessible to persons,shall be grounded. 620-84. Hand-Operated Cables. All hand-operated metallic shifting ropes or cables shall be grounded. 620-85. Inherent Ground. Equipment mounted on members of the structural metal frame of a building shall be deemed to be grounded. Metal car frames supported by metal hoisting cables attached to or run- ning over sheaves or drums of elevator machines shall be deemed to be grounded when the machine is grounded in accordance with Article 250. K. Overspeed 620-91. Overspeed Protection for DC Elevators. Under overhauling load conditions, means shall be provided on the load side of each elevator power disconnecting means to prevent the elevator from at- taining a speed equal to the governor tripping speed or a speed in ex- cess of 125 per cent of the elevator rated speed,whichever is the lesser. 620-92. Motor Generator Overspeed Device. Motor generators driven by direct current motors and used to supply direct current for the op- eration of elevator machine motors shall be provided with speed limit- ing devices as required by Section 430-89(c), which will prevent the elevator from attaining at any time a speed of more than 125 per cent of its rated speed. ARTICLE 630—ELECTRIC WELDERS A. General 630-1. Scope. This Article covers electric arc welding,resistance weld- ing apparatus, and other similar welding equipment that is connected to an electrical supply system. 630-2. Other Articles. This Article amplifies or modifies parts of Chap- ters 1 to 4 inclusive of this Code in order to properly cover the operat- ing conditions to which electric welder installations are subjected. Ac- cordingly, the appropriate provisions of Chapters 1 to 4 inclusive apply to the component parts of electric welder installations except as other- wise provided in this Article. ARTICLE 630—ELECTRIC WELDERS 70-349 B. AC Transformer and DC Rectifier Arc Welders 630-11. Ampacities of Supply Conductors. The ampacities of conduc- tors shall be as follows: (a) Individual Welders. The rated ampacities of the supply conduc- tors shall be not less than the current values determined by multiplying the rated primary current in amperes, given on the welder nameplate, and the following factor based upon the duty cycle or time rating of the welders: Rated Per Cent Duty Cycle of Welders Multiplying Factor 20 or less 0.45 30 0.55 40 0.63 50 0.71 60 0.78 70 0.84 80 0.89 90 0.95 100 1.00 For a welder having a time rating of one hour,the multiplying factor shall be 0.75. (b) Group of Welders. The rated ampacities of conductors which sup- ply a group of welders may be less than the sum of the currents, as de- termined in accordance with Section 630-11 (a) of the welders supplied. The conductor rating shall be determined in each case according to the welder loading based on the use to be made of each welder and the allowance permissible in the event that all the welders supplied by the conductors will not be in use at the same time. The load value used for each welder shall take into account both the magnitude and the dura- tion of the load while the welder is in use. Conductor ratings based on 100 per cent of the current, as determined in accordance with Section 630-11(a), of the two largest welders, 85 per cent for the third largest welder, 70 per cent for the fourth largest welder, and 60 per cent for all the remaining welders, should provide an ample mar- gin of safety under high production conditions with respect to the maximum permissible temperature of the conductors. Percentage values lower than those given are permissible in cases where the work is such that a high op- erating duty cycle for individual welders is impossible. 630-12. Overcurrent Protection. Overcurrent protection shall be as provided in Sections 630-12 (a) and (b). Where the nearest standard rating of the overcurrent device used is under the value specified in this Section, or where the rating or setting specified results in unnecessary opening of the overcurrent device, the next higher rating or setting may be used. (a) For Welders. Each welder shall have overcurrent protection rated or set at not more than 200 per cent of the rated primary current of the welder, except that an overcurrent device is not required for a welder having supply conductors protected by an overcurrent device rated or set at not more than 200 per cent of the rated primary current of the welder. 70-350 NATIONAL ELECTRICAL CODE (b) For Conductors. Conductors which supply one or more welders shall be protected by an overcurrent device rated or set at not more than 200 per cent of the conductor rating. 630-13. Disconnect Means. A disconnect means shall be provided in the supply connection of each welder which is not equipped with a dis- connect mounted as an integral part of the welder. The disconnect means shall be a switch or circuit breaker and its rating shall be not less than that necessary to accommodate overcur- rent protection as specified under Section 630-12. 630-14. Marking. A nameplate giving the following information shall be provided: name of manufacturer; frequency; primary voltage; rated primary current; maximum open-circuit secondary voltage; rated sec- ondary current; basis of rating, i.e., the duty cycle, number of phases, 60-minute rating. C. Motor-Generator Arc Welders 630-21. Other Sections Which Apply. Motor-generator arc welder in- stallations are covered by the appropriate Sections of Chapters 1 to 4 inclusive applicable to conductors, motors, generators and associated equipment. Referring specifically to the motor supply connections, the following Sections apply in addition to such other provisions as may be applicable. Conductor rating, Sections 430-22 and 430-26. Overcurrent protection for motors, Section 430-33; for conductors, Section 430-52. Controllers, Sections 430-7, 430-8 and 430-83. Disconnecting means, Section 430-111. D. Resistance Welders 630-31. Ampacities of Supply Conductors. The ampacities of the sup- ply conductors necessary to limit the voltage drop to a value permissible for the satisfactory performance of the welder are usually greater than that required to prevent overheating as prescribed in Section 630-31 (a) and (b). (a) Individual Welders. The rated ampacities for conductors for in- dividual welders shall conform to the following: (1) Varying Operations. The rated ampacities of the supply con- ductors for a welder which may be operated at different times at differ- ent values of primary current or duty cycle shall be not less than 70 per cent of the rated primary current for seam and automatically fed welders, and 50 per cent of the rated primary current for manually op- erated nonautomatic welders. (2) Specific Operation. The rated ampacities of the supply con- ductors for a welder wired for a specific operation for which the actual primary current and duty cycle are known and remain unchanged shall be not less than the product of the actual primary current and the mul- tiplier given below for the duty cycle at which the welder will be op- erated. Duty Cycle (per cent) 50 40 30 25 20 15 10 7.5 5.0 or less Multiplier 71 .63 .55 .50 .45 .39 .32 .27 .22 ARTICLE 630—ELECTRIC WELDERS 70-351 (b) Groups of Welders. The rated ampacities of conductors which supply two or more welders shall be not less than the sum of the value obtained as explained in Section 630-31(a) for the largest welder sup- plied, and 60 per cent of the values obtained as explained in Section 630-31(a) for all the other welders supplied. (c) Explanation of Terms. (1) The rated primary current is the rated kva multiplied by 1,000 and divided by the rated primary voltage,using values given on the nameplate. (2) The actual primary current is the current drawn from the supply circuit during each welder operation at the particular heat tap and control setting used. (3) The duty cycle is the percentage of the time during which the welder is loaded. For in- stance, a spot welder supplied by a 60-cycle system (216,000 cycles per hour) making four hundred 15-cycle welds per hour would have a duty cycle of 2.8 per cent (400 multiplied by 15, divided by 216,000, multi- plied by 100).A seam welder operating 2 cycles"on" and 2 cycles"off" would have a duty cycle of 50 per cent. 630-32. Overcurrent Protection. Overcurrent protection shall be as provided in Section 630-32 (a) and (b). Where the nearest standard rating of the overcurrent device used is under the value specified in this Section, or where the rating or setting specified results in unnecessary opening of the overcurrent device,the next higher rating or setting may be used. (a) For Welders. Each welder shall have an overcurrent device rated or set at not more than 300 per cent of the rated primary current of the welder, except that an overcurrent device is not required for a welder having a supply circuit protected by an overcurrent device rated or set at not more than 300 per cent of the rated primary current of the welder. (b) For Conductors. Conductors which supply one or more welders shall be protected by an overcurrent device rated or set at not more than 300 per cent of the conductor rating. 630-33. Disconnecting Means. A switch or circuit breaker shall be provided by which each welder and its control equipment can be iso- lated from the supply circuit. The ampacity of this disconnecting means shall be not less than the supply conductor rating determined as ex- plained in this Article. The supply circuit switch may be used as the welder disconnecting means where the circuit supplies only one welder. 630-34. Marking. A nameplate giving the following information shall be provided: name of manufacturer, frequency, primary voltage, rated kva at 50 per cent duty cycle, maximum and minimum open-circuit sec- ondary voltage, short-circuit secondary current at maximum secondary voltage and specified throat and gap setting. 70-352 NATIONAL ELECTRICAL CODE ARTICLE 640—SOUND-RECORDING AND SIMILAR EQUIPMENT 640-1. Scope. This Article shall apply to installations of equipment and wiring used for sound-recording and reproduction, centralized dis- tribution of sound, public address, speech-input systems and electronic organs. 640-2. Application of Other Articles. (a) Except as modified by this Article, wiring and equipment from source of power to and between devices connected to the interior wir- ing systems shall comply with the requirements of Chapters 1 to 4, in- clusive,of this Code. (b) Wiring and equipment for public-address, speech-input, radio- frequency, audio-frequency systems, and amplifying equipment asso- ciated with radio receiving stations in centralized distribution systems, shall comply with Article 725. 640-3. Number of Conductors in Raceway. The number of conductors in a conduit or other raceway shall comply with Tables 1 to 7 inclusive of Chapter 9 except as follows: Exception No. 1. Special permission may be granted for the installa- tion of two 2-conductor lead-covered cables in 3/4-inch conduit, pro- vided the cross-sectional area of each cable does not exceed .11 square inch. Exception No. 2. Special permission may be granted for the installa- tion of two 2-conductor No. 19 lead-covered cables in 1/2-inch con- duit, provided the sum of the cross-sectional areas of the cables does not exceed 32 per cent of the internal cross-sectional area of the con- duit. 640-4. Wireways and Auxiliary Gutters. (a) Wireways and auxiliary gutters shall comply with the require- ments of Articles 362 and 374. (b) Where used for sound-recording and reproduction the following exceptions are made: Exception No. 1.Number of Conductors in Raceway. Conductors in wireways or gutters shall not fill the raceway to more than 75 per cent of its depth. Exception No. 2. Auxiliary-Gutter Covers. Where the cover of aux- iliary gutters is flush with the flooring and is subject to the moving of heavy objects it shall be of steel at least 1A inch in thickness; where not subject to moving of heavy objects, as in the rear of patch or other equipment panels, the cover shall be at least No. 10 USS gage (0.1345 inch). Exception No. 3. Metal-Trough Raceways. Metal-trough raceways may be installed in concealed places provided they are run in a straight ARTICLE 640—SOUND-RECORDING, SIMILAR EQUIPMENT 70-353 line between outlets or junction boxes. Covers of boxes must be acces- sible. Edges of metal must be rounded at outlet or junction boxes and all rough projections smoothed to prevent abrasion of insulation or conductors. Raceways made of sections shall be bonded and grounded as prescribed in Section 250-76. Exception No. 4. Grounding Wireways and Auxiliary Gutters. Metal wireways and auxiliary gutters shall be grounded in accordance with the requirements of Article 250. Where the wireway or auxiliary gutter does not contain power supply wires, the grounding conductor need not be larger than No. 14 copper or its equivalent. Where the wireway or auxiliary gutter contains power supply wires, the grounding conduc- tor shall not be smaller than the size called for in Section 250-95. 640-5. Conductors. Amplifier output circuits carrying audio-program signals of 70 volts or less and whose open circuit voltage will not ex- ceed 100 volts,may employ Class 2 wiring as covered in Article 725. The above is based on amplifiers whose open-circuit voltage will not ex- ceed 100 volts when driven with a signal at any frequency from 60 to 100 cps sufficient to produce rated output (70.7 volts) into its rated load. This also accepts the known fact that the average program material is 12 db below the amplifier rating—thus the average RMS voltage for an open-circuit 70 volt output would be only 25 volts. 640-6. Grouping of Conductors. Conductors of different systems grouped in the same conduit or other metallic enclosure, or in portable cords or cables,shall comply with the following requirements: (a) Power-Supply Conductors. Power-supply conductors shall be properly indicated and shall be used solely for supplying power to the equipment to which the other conductors are connected. (b) Leads to Motor-Generator or Rotary Converter. Input leads to a motor-generator or rotary converter shall be run separately from the output leads. (c) Conductor Insulation. The conductors shall be insulated indi- vidually, or collectively in groups, by insulation at least equivalent to that on the power-supply and other conductors. Exception: Where the power-supply and other conductors are sepa- rated by a lead sheath or other continuous metallic covering. 640-7. Flexible Cords. Flexible cords and cables shall be of types S, SJ, ST, SJO, and SJT or other types specifically approved for the pur- 1 pose for which they are to be used. The conductors of flexible cords, other than power-supply conductors, may be of a size not smaller than No. 26 provided such conductors are not in direct electrical connection with the power-supply conductors and are equipped with current-limit- ing means so that the maximum power under any condition will not ex- ceed 150 watts. 640-8. Terminals. Terminals shall be marked to show their proper connections. Terminals for conductors other than power-supply con- ductors shall be separated from the terminals of the power-supply con- ductors by a spacing at least as great as the spacing between power- supply terminals of opposite polarity. 4 70-354 NATIONAL ELECTRICAL CODE 640-9. Storage Batteries. Storage batteries shall comply with the fol- lowing: (a) Installation. Storage batteries shall be installed in accordance with Article 480. (b) Conductor Insulation. Storage-battery leads shall be rubber- covered or thermoplastic-covered. 640-10. Overcurrent Protection of "A", "B" and "C" Circuits. Over- current protection shall be provided as follows: (a) "A" circuit, where supplied by branch-lighting circuits, or by storage batteries of more than 20-ampere-hour capacity, shall have overcurrent protection not exceeding 15 amperes. (b) `B" circuits shall have overcurrent protection not exceeding one ampere. The overcurrent protection shall be placed in each positive lead. (c) "C" circuits where supplied from branch lighting circuits or from storage batteries of more than 20 ampere-hour capacity shall have overcurrent protection not exceeding one ampere. (d) Overcurrent devices shall be located as near as practicable to the battery. 640-11. Amplifiers and Rectifiers—Type. (a) They shall be suitably housed and shall be of a type approved for the purpose unless otherwise expressly permitted by the authority having jurisdiction. (b) Amplifiers and rectifiers shall be so located as to be readily acces- sible. (c) Amplifiers and rectifiers shall be so located as to provide suffi- cient ventilation to prevent undue temperature rise within the housing. 640-12. Hazardous Locations. Equipment used in hazardous locations shall be specifically approved for the purpose. 640-13. Protection Against Physical Damage. Amplifiers, rectifiers, loud-speakers and other equipment shall be so located or protected as to guard against physical damage such as might result in fire or per- sonal hazard. ARTICLE 645—DATA PROCESSING SYSTEMS For further information see NFPA Standard for the Protection of Elec- tronic Computer/Data Processing Equipment(No. 75). 645-1. Scope. The provisions of this Article shall apply to equipment, power supply wiring, equipment interconnecting wiring, and grounding of data processing systems including data communications equipment used as a terminal unit. ARTICLE 645—DATA PROCESSING SYSTEMS 70-355 645-2. Supply Circuits and Interconnecting Cables. (a) The branch circuit conductors to which one or more units of a data processing system are connected to a source of supply shall have an ampacity not less than 125 per cent of the total connected load. (b) The data processing system may be connected by means of com- puter cable or flexible cord and attachment plug cap or cord set assem- bly specifically approved as a part of the data processing system. Sepa- rate units may be interconnected by means of flexible cords and cables specifically approved as part of the data processing system. When run on the surface of the floor they shall be protected against physical damage. (c) The power and communication supply cables and interconnecting cables may be installed under a raised floor provided: (1) The raised floor is of suitable construction. See NFPA No. 75. (2) The supply conductors to receptacles are in rigid conduit, elec- trical metallic tubing, flexible metal conduit, Type MI mineral insu- lated metal sheathed cable,or Type ALS aluminum sheathed cable. (3) Ventilation in the underfloor area is used for the data process- ing equipment and data processing area only. 645-3. Disconnecting Means. In addition to any integral individual disconnect switches for components or other units of the data process- ing system,disconnecting means shall be provided as follows: (a) In Data Processing Rooms. The disconnecting means shall dis- connect the ventilation system serving that room and the power to all electrical equipment in the room except lighting and shall be controlled from locations readily accessible to the operator and at designated exit doors from the data processing room. (b) In General Building Areas. The disconnecting means shall dis- connect all interconnected data processing equipment in the area and shall be controlled from a location readily accessible to the operator. 645-4. Grounding. All exposed noncurrent-carrying metal parts of a data processing system shall be grounded in accordance with Article 250. 645-5. Marking. Each unit of a data processing system which is in- tended to be supplied by a branch circuit shall be provided with a manu- facturers nameplate, which shall also include the rating in volts, the operating frequency,and the total load in amperes. 70-356 NATIONAL ELECTRICAL CODE ARTICLE 650—ORGANS 650-1. General. This Article shall apply to those electric circuits and parts of electrically operated organs which are employed for the con- trol of the sounding apparatus and keyboards. Electronic organs shall comply with the appropriate provisions of Article 640. 650-2. Source of Energy. The source of energy shall have a potential of not over 15 volts and shall be a self-excited generator, a two-coil transformer type rectifier or a primary battery. 650-3. Insulation—Grounding. The generator shall be effectively in- sulated from the ground and from the motor driving it, or both the gen- erator and the motor frames shall be grounded in the manner pre- scribed in Article 250. 650-4. Conductors. Conductors shall comply with the following: (a) Size. No conductor shall be smaller than No. 26, and the common-return conductor shall be not smaller than No. 14. (b) Insulation. Conductors shall have rubber, thermoplastic, as- bestos, cotton, or silk insulation, except the common-return conductor which shall be rubber-covered, thermoplastic, asbestos-covered (Types AA, AI, or AIA). The cotton or silk may be saturated with paraffin if desired. (c) Conductors to Be Cabled. Except the common-return conductor, and conductors inside the organ proper, the organ sections and the or- gan console, conductors shall be cabled. The common-return conduc- tor may be placed under an additional covering enclosing both cable and return conductor, or may be installed as a separate conductor and may be in contact with the cable. (d) Cable Covering. The cable shall be provided with one or more braided outer coverings, provided that a tape may be used in place of an inner braid. Where not installed in metal raceways the outer braid shall be flame-retardant or shall be covered with a closely wound fire- proof tape. 650-5. Installation of Conductors. Cables shall be securely fastened in place and may be attached directly to the organ structure without in- sulating supports. Cables shall not be placed in contact with other con- ductors. 650-6. Overcurrent Protection. Circuits shall be so arranged that all conductors, except the main supply conductors and the common-return conductor, shall be protected from overcurrent by an overcurrent de- vice of not greater than 15-ampere rating. ARTICLE 660—X-RAY EQUIPMENT 70-357 ARTICLE 660—X-RAY EQUIPMENT A.Scope and Installation 660-1. Scope. The provisions of this Article shall apply to all X-ray equipment operating at any frequency or voltage for medical or indus- trial use,or for any other purpose. Nothing in this Article shall be construed as specifying safeguards against the useful beam or stray X-ray radiation. Recommendations for radiation protection by the National Council on Radiation Protection and Measurements are published as Reports of the Na- tional Council on Radiation Protection and Measurement. These reports are obtainable from NCRP Publications,P.O.Box 4867,Washington,D.C.,20008. Definitions: PORTABLE—X-ray equipment designed to be hand-carried. MOBILE—X-ray equipment mounted on a permanent base with wheels and/or casters for moving while completely assembled. TRANSPORTABLE—X-ray equipment to be installed in a vehicle or that may be readily disassembled for transport in a vehicle. LONG TIME RATING—A long time rating is the rating based on an operating interval of five minutes or longer. MOMENTARY RATING—A momentary rating is the rating based on an operating interval that does not exceed five seconds. 660-2. Hazardous Locations. Unless approved for the location, X-ray and related equipment shall not be installed or operated in hazardous locations.See Article 517. 660-3. Connection to Supply Circuit. (a) Fixed and Stationary Equipment. Fixed and stationary X-ray equipment shall be connected to the power supply by means of a wiring method meeting the general requirements of this Code, except that equipment properly supplied by branch circuits not larger than a 30- ampere branch circuit may be supplied through suitable plug and hard service cable or cord. (b) Portable and Transportable. Individual branch circuits shall not be required for portable,mobile,and transportable medical X-ray equip- ment requiring a capacity not exceeding 60 amperes. Receptacles in- stalled on 60 ampere branch circuits shall be of a special configuration approved for use with medical X-ray equipment. Portable and mobile types of X-ray equipment of any capacity shall be supplied through a suitable plug and hard service cable or cord. Transportable X-ray equipment of any capacity may be connected to its power supply by suitable connections and hard service cable or cord. (c) More than 600 Volt Supply. Circuits and equipment operated on a supply circuit of more than 600 volts shall comply with the provisions of Article 710. 70-358 NATIONAL ELECTRICAL CODE 660-4. Disconnecting Means. A disconnecting means' of adequate ca- pacity for at least 50 per cent of the input required for the momentary rating or 100 per cent of the input required for the long time rating of the X-ray equipment whichever is greater shall be provided in the sup- ply circuit and it shall be operable from a location readily accessible from the X-ray control. For equipment requiring 125 volt line fuses of 30 amperes or less, a plug and receptacle of proper size and of an ap- proved make may serve as a disconnecting means. Disconnecting means shall not be required for portable X-ray equipment of any capacity which complies with Section 660-11. 660-5. Branch Circuit and Overcurrent Protection Requirements. Fifty per cent of the momentary rating or 100 per cent of the long time rating of the X-ray equipment whichever is greater shall be used in determining the ampacity requirements for branch circuits and overcurrent protec- tion devices. The ampacities of the branch circuit conductors and the ratings of discon- necting means and overcurrent protection for X-ray equipment is usually recommended by the manufacturer for the specific installation. 660-6. Wiring Terminals. Unless provided with a permanently at- tached cord or a cord set, X-ray equipment shall be provided with suit- able wiring terminals or leads for the connection of conductors of at least the size required by the input load corresponding to the long time rating of the equipment. 660-7. Number of Conductors in Raceway. The number of control circuit conductors installed in a raceway may be in accordance with Table 1 of Chapter 9. 660-8. Shockproof Installations. All equipment used on new installa- tions of X-ray equipment, or used or reconditioned equipment moved to and reinstalled at a new location,shall be of the approved shockproof type. B. Control 660-9. Fixed and Stationary Equipment. (a) Separate Control Device. A separate control device in addition to the disconnecting means, shall be incorporated in the X-ray control supply or in the primary circuit to the high voltage transformer. This device shall be a part of the X-ray equipment, but may be located in a separate enclosure immediately adjacent to the X-ray control unit. (b) Protective Device. A protective device which may be incorpo- rated into the separate control device, shall be provided to control the load resulting from failures in the high voltage circuit. 660-11. Portable Equipment. Portable equipment shall comply with Section 660-9, but the manually controlled device shall be located in or on the equipment. 660-12. General. (a) Radiographic Type. There shall be provided a timer or auto- matic exposure terminating device and also a switch of a type which opens automatically except when held closed by the operator. ARTICLE 660—X-RAY EQUIPMENT 70-359 (b) Fluoroscopic Type. A switch shall be provided which shall be designed to open automatically except when held closed by the opera- tor. (c) Therapy. A timer or automatic exposure terminating device shall be provided which is not of the repeating type. C. Industrial Equipment 660-13. Industrial X-ray Equipment. (a) Radiographic and Fluoroscopic Types. A switch which shall be designed to open automatically except when held closed by the oper- ator, or a timer, shall be provided except on equipment or installations effectively enclosed or provided with interlocks to prevent ready access to live current-carrying parts during operation. (b) Industrial or Laboratory Equipment — Diffraction or Irradiation Types. Positive indication of energization by pilot lights, readable meter deflections or equivalent means shall be provided except on equipment or installations effectively enclosed or provided with inter- locks to prevent ready access to live current-carrying parts during op- eration. 660-14. Independent Control. Where more than one piece of equip- ment is operated from the same high-voltage circuit, each piece or each group of equipment as a unit shall be provided with a high-voltage switch or equivalent disconnecting means. This disconnecting means shall be constructed, enclosed, or located so as to avoid contact by per- sons with its live parts. D. Transformers and Capacitors 660-15. General. Transformers and capacitors which are part of an X-ray equipment shall not be required to conform to the requirements of Articles 450 and 460 of this Code. 660-16. Capacitors. Capacitors shall be mounted within enclosures of grounded metal or insulating material. E. Guarding and Grounding 660-17. General. (a) High Voltage Parts. All high voltage parts, including X-ray tubes, shall be mounted within grounded enclosures. Either air, oil, gas or other suitable insulating media may be used to insulate the high voltage from the grounded enclosure. The connections from the high voltage equipment to X-ray tubes and other high voltage components shall be made with high voltage cables of the shockproof type. (b) Low Voltage Cables. Low voltage connecting cables to oil filled units such as transformers, condensers, oil coolers, and high voltage switches which are not completely sealed shall be of the oil resistant type. 660-18. Grounding. Noncurrent-carrying metal parts of X-ray and associated equipment (controls, tables, X-ray tube stands, transformer • 70-360 NATIONAL ELECTRICAL CODE tanks, shockproof cables, X-ray tube heads, etc.) shall be grounded in the manner prescribed in Article 250. (a) Portables. Portable equipment shall be provided with an ap- proved grounding type plug. ARTICLE 665—INDUCTION AND DIELECTRIC HEATING EQUIPMENT A. Scope and General 665-1. Scope. The provisions of this Article shall apply to the con- struction and installation of induction and dielectric heating equipment and accessories for industrial, scientific and medical applications, but not for appliances. 665-2. Definitions. The term "heating equipment" as used in this Article includes any equipment used for heating purposes whose heat is generated by induction or dielectric methods. Induction heating is the heating of a nominally conducting material due to its own PR losses when the material is placed in a varying electro- magnetic field. Dielectric heating is the heating of a nominally insulating material due to its own dielectric losses when the material is placed in a vary- ing electric field. The term "therapeutic high frequency equipment" as used in this Article shall be understood to mean generating equipment capable of producing alternating currents having frequencies greater than those frequencies which elicit neuromuscular response. In order to comply with the above, the output frequency of the therapeutic high frequency equipment shall not be less than 2 megacycles. 665-3. Application of Other Articles. Wiring from the source of power to the heating equipment shall comply with the Code Chapters 1 to 4 inclusive. Circuits and equipment operating on a supply circuit of more than 600 volts shall comply with the provisions of Article 710. 665-4. Hazardous Locations. Induction and dielectric heating equip- ment shall not be installed in hazardous locations as defined in Article 500 unless the equipment and wiring is designed and approved for the locations. B. Motor-Generator Equipment 665-5. Scope. Motor generator equipment shall include all rotating equipment designed to operate from an AC or DC motor, or by me- chanical drive from a prime mover, producing an alternating current of any frequency for induction and/or dielectric heating. 665-6. Ampacities of Supply Conductors. Ampacities of supply con- ductors shall be determined by Article 430 of this Code. ARTICLE 665—INDUCTION, DIELECTRIC HEATING 70-361 665-7. Overcurrent Protection. Overcurrent protection shall be pro- vided as specified in Article 430 of this Code for the electrical supply circuit. 665-8. Disconnecting Means. The disconnecting means shall be pro- vided as specified in Article 430 of this code. A readily accessible disconnecting means shall be provided by which each heating equipment can be isolated from the supplying circuit. The ampacity of this disconnecting means shall be not less than the name- plate current rating of the equipment. The supply circuit disconnect means may be used as a heating equipment disconnecting means where the circuit supplies only one equipment. 665-9. Output Circuit Definition. The output circuit shall include all high frequency output components external to the generator, including contactors, transformers, bus-bars, and transmission lines. The same definition shall apply to all off line frequencies obtained from motor generators,or generators used with induction heating loads. 665-10. Output Circuits. Output circuits shall conform to the follow- ing: (a) Generator Output. The output circuit shall be isolated from ground, except for the capacitive coupling inherent in the generator, which, in effect causes the generator terminals to have voltages from terminal to ground that are equal. When rated at more than 500 volts, the output circuit shall incor- porate a DC ground protector unit. The DC impressed on the output circuit shall not exceed 30 volts and shall not exceed a current capabil- ity of 5 milliamperes. An isolating transformer for matching the load and the source may be used in the output circuit wherein the secondary is not at DC ground potential. (b) Component Interconnections. The various components required for a complete induction heating equipment installation shall be con- nected by properly protected multiconductor cable, bus bar, or coaxial cable. Cables shall be installed in non-ferrous conduit raceways. Bus bar shall be protected where required by nonferrous enclosures. 665-11. Control-Enclosures. Low frequency AC or DC may be used in the control portion of the heating equipment. This shall be limited to a value of 150 volts. Solid or stranded wire, properly sized in No. 18 AWG or larger shall be used. Sixty cycle components may be used to control HF when properly rated by the induction heating equipment manufacturer. Electronic circuits utilizing solid state devices and tubes may use printed circuits or wire sizes, properly sized smaller than No. 18 AWG. 665-12. Remote Control (a) When remote controls are used for applying power, a "Local- Remote" switch shall be provided and interlocked so as to prevent the possibility of applying power from other than one selected control point or points. 70-362 NATIONAL ELECTRICAL CODE (b) Switches operated by foot pressure shall be provided with a shield over the contact button to avoid accidental closing. C. Equipment Other Than Motor Generator 665-13. Scope. Equipment other than motor generator includes all static multipliers and oscillator type units utilizing vacuum tubes and/or solid state devices. The equipment shall be capable of converting AC, or DC to a frequency suitable for induction and/or dielectric heating. 665-14. Ampacities of Supply Conductors. Ampacities of supply con- ductors shall be determined as follows: (a) The ampacity of the circuit shall be not less than the nameplate current rating of the equipment. (b) The ampacities of conductors supplying two or more equipments shall be not less than the sum of nameplate current ratings on all equipment except as follows: Where, when supplying two or more equipments from the same feeder, simultaneous operation of said equipments is not possible, the ampacity of the feeder shall be not less than the sum of the nameplate currents for the largest group of ma- chines capable of simultaneous operation, plus 100 per cent of the standby currents of the remaining machines supplied. 665-15. Overcurrent Protection. Overcurrent protection shall be pro- vided as specified in Article 430 for the equipment as a whole. This overcurrent protection shall be provided separately or as a part of the equipment. 665-16. Disconnecting Means. A readily accessible disconnecting means shall be provided by which each heating equipment can be isolated from the supplying circuit. The ampacity of this disconnecting means shall not be less than the nameplate current rating of the equip- ment. The supply circuit disconnect means may be used for disconnect- ing the heating equipment where the circuit supplies only one equip- ment. 665-17. Output Circuit Definition. The output circuit shall include all high frequency output components external to the converting device including contactors, transformers, bus-bars, and transmission lines. The same definition shall apply to all off line frequencies obtained from the converting device, or devices used with induction and/or dielec- tric heating loads. 665-18. Output Circuits. Output circuits shall conform to the follow- ing: (a) Converter Output. The output circuit (direct or coupled) shall be at DC ground potential. (b) Converter and Applicator Connection. When the connections between the converter and the work applicator exceed two feet in length the connections shall be enclosed or guarded with noncombustible ma- terial. 665-19. Line Frequency in Converter Equipment Output. Commercial frequencies of 25 to 60 cycle alternating current output may be cou- pled for control purposes, but shall be limited to a value of 150 volts available only during periods of circuit operation. ARTICLE 665—INDUCTION, DIELECTRIC HEATING 70-363 665-20. Keying. Where high-speed keying circuits dependent on the effect of "oscillator blocking" are employed, the peak R.F. output volt- age during the blocked portion of the cycle shall not exceed 100 volts in units employing R.F.converters. 665-21. Remote Control. (a) When remote controls are used for applying power, a "Local Re- mote"switch shall be provided and interlocked so as to prevent the pos- sibility of applying power from other than one selected control point or points. (b) Switches operated by foot pressure shall be provided with a shield over the contact button to avoid accidental closing. D. Guarding and Grounding 665-22. Enclosures. The converting apparatus (including the DC line) and high frequency electrical circuits (excluding the output circuits and remote control circuits), shall be completely contained in an en- closure or enclosures of noncombustible material. 665-23. Panel Controls. All panel controls shall be of "dead front" construction. 665-24. Access to Internal Equipment. Doors or detachable panels may be employed for internal access. Where doors are used giving access to voltages from 500 to 1000 volts AC or DC, either door locks shall be provided or interlocking shall be installed with the choice of precaution optional. Where doors are used giving access to voltages above 1000 volts AC or DC, either mechanical lockouts, with a disconnect means to prevent access until voltage is removed from the cubicle, or both door interlocking and mechanical door locks shall be provided. Detachable panels not normally used for access to such parts shall be fastened in a manner which will make them inconvenient to remove. 665-25. Warning Labels. "Danger" labels shall be attached on the equipment, and shall be plainly visible even when doors are opened or panels are removed from compartments containing voltages above 250 volts AC or DC. 665-26. Capacitors. When capacitors in excess of 0.1 Mfd. are used in DC circuits, either as rectifier filter components, or suppressors, etc., having circuit voltages exceeding 230 volts above ground, bleeder resistors or grounding switches shall be used as grounding devices. The time of discharge shall be in accordance with Section 460-6 (a). Where auxiliary rectifiers are used with filter capacitors in the output for bias supplies, tube keyers, etc., bleeder resistors shall be used even though the DC voltage may not exceed 230 volts. 665-27. Work Applicator Shielding. Protective cages or adequate shielding shall be used to guard work applicators other than induction heating coils. Induction heating coils may be protected by insulation and/or refractory materials. Interlock switches shall be used on all hinged access doors, sliding panels or other easy access to the appli- cator. All interlock switches shall be connected in such a manner as to 70-364 NATIONAL ELECTRICAL CODE remove all power from the applicator when any one of the access doors or panels is open. Interlocks on access doors or panels are not required when the applicator is an induction heating coil at DC ground poten- tial or operating at less than 150 volts AC. 665-28. Grounding and Bonding. Grounds and/or inter-unit bonding shall be used wherever required for circuit operation and for limiting to a safe value radio frequency potentials between all exposed noncur- rent-carrying parts of the equipment and earth ground, also between all equipment parts and surrounding objects and between such objects and earth ground. Such grounding and bonding shall be installed in accord- ance with Article 250 of this Code. 665-29. Marking. Each heating equipment shall be provided with a nameplate, giving the manufacturer's name and model identification, and the following input data: line volts, frequency, number of phases, maximum current,full load KVA and full load power factor. E. Therapeutic Equipment 665-30. Installation. (a) Where portability is not essential,equipment shall be permanently installed in accordance with Chapters 1 to 3 inclusive of this Code. (b) Where portability is essential, the power supply cord shall be a three-conductor hard service type with an ampacity not less than the marked rating of the equipment. One conductor having a continuous green color or a continuous green color with a yellow stripe insulation shall be used solely for equipment grounding. The cord shall terminate in an approved grounding attachment-plug cap as described in Section 250-59(b). 665-31. Applicators for Therapeutic Equipment. Application of the high frequency power to the patient may be made by means of an elec- tric field or of an induction field. Current-carrying parts of applicators shall be so insulated or enclosed that reliable isolation of the patient shall be assured. 665-32. Enclosure. The converting apparatus including the DC line, and high frequency electrical circuits, but excluding the line cord for portable units and the output circuits, shall be contained in an enclosure of noncombustible material. 665-33. Panel Controls. All panel controls shall be of "dead front" construction. 665-34. Access to Internal Equipment. Access shall be through panels not conveniently removable. Panels which need removal for access to fuses, tubes, adjustments, overload reset devices, internal tap switches, and the like,shall be labeled to indicate danger if and when removed,or shall be provided with suitable electrical interlock devices. ARTICLE 670—METALWORKING MACHINE TOOLS 70-365 ARTICLE 670—METALWORKING MACHINE TOOLS For further information see NFPA Standard on Metalworking Machine Tools(No.79). 670-1. Scope. The provisions of this Article apply to the size and overcurrent protection of supply conductors to metalworking machine tools and to the nameplate data required on each such tool. 670-2. Definition of Metalworking Machine Tools. For the purpose of this Article,metalworking machine tools are defined as follows: (a) A metal-cutting machine tool is a power driven machine, not portable by hand,used for the purpose of removing metal. (b) A metal-forming machine tool is a power driven machine, not portable by hand, used to press, forge, emboss, hammer, blank, or shear metal. 670-3. Machine Tool Nameplate Data. A permanent nameplate listing supply voltage, phase, frequency, full load currents (see note), ampere rating of largest motor, short circuit interrupting capacity of the ma- chine overcurrent protective device if furnished, and diagram number shall be attached to the control equipment enclosure or machine where plainly visible after installation. NOTE 1. The full load current shall be not less than the sum of the full load currents required for all motors and other equipment which may be in operation at the same time under normal conditions of use. Where unusual type loads, duty-cycles, etc., require oversized conduc- tors, the required capacity shall be included in the marked "full load current." NOTE 2. Where more than one incoming supply circuit is to be pro- vided,the nameplate shall state the above information for each circuit. 670-4. Conductors Supplying a Machine Tool. (a) The supply circuit conductor shall have an ampacity of not less than the marked full load current rating plus 25 per cent of the full load current rating of the highest rated motor as indicated on the name- plate. For the protection of supply conductors to the machine tool, re- fer to Section 240-5. (b) A machine tool conforming with NFPA No. 79 shall be consid- ered individual unit equipment. It is provided with a disconnecting means and may be supplied by branch circuits protected by either fuses or circuit breakers. (c) The disconnecting means may or may not incorporate overcur- rent protection. Where the machine tool nameplate is marked "Over- current protection provided at machine supply terminals," the supply conductors are to be considered either as feeders, or taps as covered by Section 240-15. "Overcurrent protection provided at machine supply terminals" means that provision has been made in the machine tool for each set of supply con- ductors to terminate in a single circuit breaker or set of fuses. 70-366 NATIONAL ELECTRICAL CODE ARTICLE 680—SWIMMING POOLS 680-1. Scope. The provisions of this Article apply to the construction and installation of electric wiring for equipment in or adjacent to swim- ming pools, to metallic appurtenances in or within 5 feet of the pool, and to the auxiliary equipment such as pumps, filters and similar equip- ment. No electric appliances or wiring shall be installed in the water or in the enclosing walls of a swimming pool, except as provided for in this Article. 680-2. Approval of Equipment. All equipment shall be approved for the purpose. 680-3. Application of Other Articles. Except as modified by this Ar- ticle, wiring and equipment in or adjacent to swimming pools shall comply with the applicable requirements of Chapters 1 to 4, inclusive, of this Code. See Article 720 for low voltage lighting. 680-4. Lighting. (a) The provisions of this Section apply to lighting fixtures installed below the pool surface. (b) No lighting fixture shall be installed for operation at more than 150 volts between conductors. (c) Lighting fixtures mounted in walls shall be installed with the top of the fixture lens at least 18 inches below the normal water level of the pool. A lighting fixture facing upward shall have the lens adequately guarded to prevent contact by any person. (d) All exposed noncurrent-carrying metal parts of lighting fixtures shall be grounded. The fixture shall be secured and grounded to the forming shell by a positive locking device which will assure a low resist- ance contact and which will require a tool to remove the fixture from the forming shell. Definition. A forming shell is a metal housing designed to contain a lighting fixture assembly for mounting into a swimming pool structure. The forming shell provides a bond between the raceway and the non- current-carrying metal parts of the fixture. (e) Fixtures approved for the purpose may be installed outside the walls of the pool in closed recesses which are adequately drained and accessible for maintenance. (f) Approved metal forming shells shall be installed for the mounting of all wet niche underwater fixtures and shall be equipped with provi- sions for threaded conduit entries. A rigid conduit of brass or other ap- proved corrosion-resistant metal shall extend from the forming shell to a suitable junction box located as provided in Section 680-5. Metal parts of the fixture and forming shell in contact with the pool water shall be of brass or other approved corrosion-resistant metal. (g) Underwater lighting fixtures supplied either directly from a branch circuit or by a transformer meeting the requirements of Section ARTICLE 680—SWIMMING POOLS 70-367 680-4(h) shall perform reliably under any likely combination of fault conditions so that there is no shock hazard. Compliance with this re- quirement shall be assured by one of the following: (1) The design and construction of the fixtures;or (2) The use of a ground-fault circuit interrupter. Definition. A ground-fault circuit-interrupter is a device whose func- tion is to interrupt the electric circuit to the load when a fault current to ground exceeds some predetermined value that is less than that re- quired to operate the overcurrent protective device of the supply circuit. (3) Other acceptable means. (h) Transformers used for the supply of fixtures, together with the transformer enclosure, shall be approved for the purpose. The trans- formers shall be a two-winding type having a grounded metal barrier between the primary and secondary voltage windings. (i) The end of the flexible cord jacket and the flexible cord conductor terminations within a fixture shall be covered with or encapsulated in a suitable potting compound to prevent the entry of water into the fixture through the cord or its conductors. In addition, the grounding connec- tion within a fixture shall be similarly treated to protect such connection from the deteriorating effect of pool water in the event of water entry into the fixture. (I) Conductors on the load side of a ground-fault circuit-interrupter or of a transformer, used to comply with the provisions of Section 680- 4(g),shall be kept entirely independent of all other wiring and electrical equipment. 680-5. Junction Boxes and Transformer Enclosures. (a) Junction boxes installed on the supply side of conduits extending to underwater pool lights shall be provided with threaded hubs for con- duit connection. The box that is directly connected to the conduit ex- tending to the underwater pool light shall be located not less than 8 inches, measured from the inside of the bottom of the box above the ground level, pool deck, or maximum pool water level, whichever pro- vides the greatest elevation. The junction box shall be located not less than 4 feet from the perimeter of the pool unless separated from the pool by a fence, wall or other permanent barrier. Junction boxes mounted above the grade of the finished walkway around the pool shall not be located in the walkway unless afforded additional protec- tion such as by location under diving boards, adjacent to fixed struc- tures, and the like. Junction boxes shall be of corrosion-resistant ma- terial. There shall be electrical continuity between every connected conduit and the grounding terminals by means of copper, brass, or other approved corrosion-resistant metal that is integral with the box. (b) An enclosure for a transformer, ground-fault circuit interrupter or other device shall be located not less than 12 inches, measured from the inside bottom of the enclosure to the ground level, pool deck, or maximum pool water level, whichever provides the greatest elevation. The enclosure shall be located not less than 4 feet from the perimeter of the pool unless separated from the pool by a fence,wall or other perma- 70-368 NATIONAL ELECTRICAL CODE nent barrier. These enclosures mounted above the grade of the finished walkway around the pool shall not be located in the walkway unless afforded additional protection such as by location under diving boards, adjacent to fixed structures, and the like. Where these enclosures are installed on supply side of conduits extending to underwater pool lights, they shall be of corrosion-resistant material. There shall be electrical continuity between every connected conduit and the grounding termi- nals by means of copper, brass, or other approved corrosion-resistant metal that is integral with the enclosure. (c) Boxes shall be provided with means for independently terminat- ing not less than two grounding conductors. 680-6. Attachment Plug Receptacles. No attachment plug receptacles shall be installed within 10 feet of the inside walls of the swimming pool. Exception: Attachment plug receptacles of other than the standard 15 ampere parallel slot type may be installed where an integral part of the lighting fixture assembly and where used for the installation, main- tenance,or servicing of the fixture. NOTE: In determining the 10-foot dimension, the distance to be measured is the shortest path which the supply cord of an appliance connected to the receptacle would follow without piercing a building floor, wall or ceiling. It is recommended that all attachment plug receptacles in the area adjacent to the swimming pool be installed on a circuit protected by a ground-fault circuit-interrupter. 680-7. Grounding. (a) The following parts shall be bonded together by a copper conduc- tor not smaller than No. 8 AWG: (1) Pool reinforcing steel,metal parts of ladders,diving boards and their supports, and the like, and metal parts of electrical equipment associated with the pool water circulating system. Exception No. 1: The usual steel tie wires are considered suitable for bonding the reinforcing steel together and welding or special clamp- ing will not be required. Exception No. 2:Structural reinforcing steel may be used as a com- mon bonding grid for non-electrical parts where connections can be made in accordance with Section 250-113. (2) All fixed metallic parts that are within 5 feet of the inside walls of the swimming pool and that are not separated from the pool area by a permanent barrier. (b) Where the swimming pool lighting is supplied directly from a panelboard, which is part of the service equipment, an insulated un- broken No. 12 AWG copper wire shall be installed as the grounding conductor from the underwater light fixture junction box to the service equipment ground terminal. The grounding conductor shall be installed with the circuit conductors in an approved rigid metallic or rigid non- metallic conduit. Where the swimming pool lighting is supplied by a panelboard remote from the service equipment, an insulated copper grounding conductor ARTICLE 680—SWIMMING POOLS 70-369 sized in accordance with Section 250-95, but not smaller than No. 12 AWG, shall be installed between the panelboard and the service equip- ment grounding terminal. In addition, an insulated unbroken No. 12 AWG copper grounding conductor shall be installed with the circuit conductors in an approved rigid metallic or rigid nonmetallic conduit from the underwater light fixture junction box to the panelboard ground terminal. Exception: Where the swimming pool lighting is supplied from exist- ing panelboards, the grounding conductor may be terminated in an ap- proved manner provided that the panelboard is properly grounded to the service equipment with an insulated copper conductor in a conduit or cable assembly. (c) Metallic raceways shall not be depended upon for grounding ex- cept between the forming shell and the junction box. Where exposed to pool water and in other corrosive areas such as a pump house or adja- cent to water treating and other equipment, the grounding of the non- current-carrying metal parts shall be by means of an insulated copper conductor sized in accordance with Section 250-95 and not smaller than No. 12 AWG. 680-8. Methods of Grounding and Bonding. (a) Metal wiring enclosures shall be grounded in accordance with Article 250,in addition to other requirements of this Article. (b) In addition to other requirements of this Article, lighting fixtures that are supplied by flexible cord or cable shall have all exposed non- current-carrying metal parts grounded by means of an insulated ground- ing conductor that is an integral part of the cord or cable. This ground- ing conductor shall be connected to a grounding terminal in the supply junction box. This conductor shall be equal in size to the supply con- ductors but not smaller than No. 16 AWG. 680-9. Clearances. Service drop conductors and any other open over- head wiring shall not be installed above the swimming pool or surround- ing area extending 10 feet horizontally from the pool edge, or diving structure,observation stands,towers or platforms. 70-370 Chapter 7. Special Conditions ARTICLE 700—EMERGENCY SYSTEMS A. General 700-1. Scope. The provisions of this Article apply to the installation, operation and maintenance of circuits, systems and equipment intended to supply illumination and power in the event of failure of the normal supply or in the event of accident to elements of a system supplying power and illumination essential for safety to life and property where such systems or circuits are legally required by Municipal, State, Fed- eral or other Codes,or by any governmental agency having jurisdiction. Emergency systems are generally installed in places of assembly where artificial illumination is required, such as buildings subject to oc- cupancy by large numbers of persons, hotels, theaters, sports arenas, hospitals and similar institutions. Emergency systems may provide power for such functions as essential refrigeration, operation of me- chanical breathing apparatus,ventilation when essential to maintain life, illumination and power for hospital operating rooms,fire alarm systems, fire pumps, industrial processes where current interruption would produce serious hazards,public address systems and similar functions. See NFPA Life Safety Code (NFPA No. 101) for specification of locations where emergency lighting is considered essential to life safety. 700-2. Other Requirements. All requirements of the National Elec- trical Code shall apply to emergency systems, except as modified by this Article. 700-3. Equipment Approval. All equipment shall be approved for use on emergency systems. 700-4. Tests and Maintenance. (a) The authority having jurisdiction shall conduct or witness a test on the complete system upon installation and periodically afterward. (b) Systems shall be tested periodically on a schedule acceptable to the authority having jurisdiction to assure their maintenance in proper operating condition. (c) Where battery systems or unit equipments are involved, includ- ing batteries used for starting or ignition in auxiliary engines, the au- thority having jurisdiction shall require periodic maintenance. (d) A written record shall be kept of such tests and maintenance. 700-5. Capacity. Emergency systems shall have adequate capacity and rating for the emergency operation of all equipment connected to the system. B. Sources of Power 700-6. Systems. Current supply shall be such that in event of failure of the normal supply to or within the building or group of buildings concerned,emergency lighting,or emergency power, or both emergency ARTICLE 700—EMERGENCY SYSTEMS 70-371 lighting and power, will be immediately available. The supply system for emergency purposes may comprise one or more of the types of system covered in Section 700-7 to Section 700-10. Unit equipments in accordance with Section 700-22 shall satisfy the applicable require- ments of this Article. Consideration must be given to the type of service to be rendered, whether of short time duration, as for exit lights of a theater, or of long duration as for supplying emergency power and lighting due to a long period of current failure from trouble either inside or outside the build- ing, as in the case of a hospital. Assignment of degree of reliability of the recognized emergency supply system depends upon the careful evaluation of the variables at each particu- lar installation. 700-7. Storage Battery. One service, in accordance with Article 230, and a storage battery of suitable rating and capacity to supply and maintain at not less than 91 per cent of system voltage the total load of the circuits supplying emergency lighting and emergency power for a period of at least 1/2 hour. Batteries whether of the acid or alkali type shall be designed and constructed to meet the requirements of emergency service. When of the lead-acid type, this shall include low gravity acid (1.20 to 1.22 SP-GR), relatively thick and rugged plates and separators, and a trans- parent jar. 700-8. Generator Set. One service, in accordance with Article 230, and a generator set driven by some form of prime mover and of suffi- cient capacity and proper rating to supply circuits carrying emergency lighting or lighting and power, with suitable means for automatically starting the prime mover on failure of the normal service. For hospi- tals, the transition time from instant of failure of the normal power source to the emergency generator source shall not exceed ten seconds. See Section 700-4. 700-9. Separate Service. Two services, each in accordance with Arti- cle 230, with separate service drops or laterals, widely separated elec- trically and physically to minimize possibility of simultaneous interrup- tion of supply. 700-10. Connection Ahead of Service Disconnecting Means. Connec- tions on the line side of the main service if sufficiently separated from main service to prevent simultaneous interruption of supply through an occurrence within the building or group of buildings served. 700-11. Auxiliary Source. The requirements of Section 700-5 and Section 700-6 shall also apply to installations where the entire electrical load on a service or sub-service is arranged to be supplied from a sec- ond source. Current supply from a standby power plant shall satisfy the requirements of availability in Section 700-6. 700-12. Derangement Signals. Audible and visual signal devices shall be provided where practicable for the following purposes: (a) To give warning of derangement of the emergency or auxiliary source. 70-372 NATIONAL ELECTRICAL CODE (b) To indicate that the battery or generator set is carrying load. (e) To indicate when battery charger is properly functioning. C. Emergency Circuits for Lighting and Power 700-13. Loads on Emergency Branch Circuits. No appliances and no lamps, other than those specified as required for emergency use shall be supplied by emergency lighting circuits. 700-14. Emergency Illumination;. Emergency illumination shall include all required exit lights and all other lights specified as necessary to pro- vide sufficient illumination. Emergency lighting systems should be so designed and installed that the failure of any individual lighting element, such as the burning out of a light bulb,cannot leave any space in total darkness. 700-15. Circuits for Emergency Lighting. Branch circuits intended to supply emergency lighting shall be so installed as to provide service im- mediately when the normal supply for lighting is interrupted. Such in- stallations shall provide either one of the following: (a) An emergency lighting supply, independent of the general light- ing system with provisions for automatically transferring, by means of devices approved for the purpose, the emergency lights upon the event of failure of the general lighting system supply. (b) Two or more separate and complete systems with independent power supply, each system providing sufficient current for emergency lighting purposes. Unless both systems are used for regular lighting purposes and are both kept lighted, means shall be provided for auto- matically energizing either system upon failure of the other. Either or both systems may be part of the general lighting system of the protected occupancy if circuits supplying lights for emergency illumination are installed in accordance with other sections of this article. 700-16. Circuits for Emergency Power. For branch circuits which sup- ply equipment classed as emergency, there shall be an emergency sup- ply source to which the load will be transferred automatically and im- mediately upon the failure of the normal supply. 700-17. Independent Wiring. Emergency circuit wiring shall be kept entirely independent of all other wiring and equipment and shall not enter the same raceway,box or cabinet with other wiring except: Exception No. 1.In transfer switches. Exception No. 2. In exit or emergency lighting fixtures supplied from two sources. D. Control 700-18. Switch Requirements. The switch or switches installed in emergency lighting circuits shall be so arranged that only authorized persons will have control of emergency lighting except: Exception No. 1. Where two or more single throw switches are con- nected in parallel to control a single circuit, at least one of these switches shall be accessible only to authorized persons. ARTICLE 700—EMERGENCY SYSTEMS 70-373 Exception No. 2. Additional switches which act only to put emer- gency lights into operation but not disconnect them are permissible. Switches connected in series or three and four way switches shall not be used. 700-19. Switch Location. (a) All manual switches for controlling emergency circuits shall be in locations convenient to authorized persons responsible for their ac- tuation. In places of assembly such as theaters a switch for controlling emergency lighting systems shall be located in the lobby or at a place conveniently accessible thereto. (b) In no case shall a control switch for emergency lighting in a thea- ter or motion-picture theater be placed in a motion-picture projection booth or on a stage, except that where multiple switches are provided, one such switch may be installed in such location when so arranged that it can energize,but not disconnect,the circuit. 700-20. Other Switches. (a) Exterior Lights. Those lights on the exterior of the building which are not required for illumination when there is sufficient daylight may be controlled by an automatic light-actuated device approved for the purpose. (b) Hospital Corridors. Switching arrangements to transfer corri- dor lighting in patient areas of hospitals from overhead fixtures to fix- tures designed to provide night lighting may be permitted, provided the switching system is so designed that switches can only select be- tween two sets of fixtures and cannot extinguish both sets at the same time. E. Overcurrent Protection 700-21. Accessibility. The branch circuit overcurrent devices in emergency circuits shall be accessible to authorized persons only. F. Unit Equipments 700-22. Unit Equipments. Where permitted by the authority having jurisdiction, in lieu of other methods specified elsewhere in this Article, individual unit equipments for emergency illumination shall consist of (a) a battery, (b) battery charging means when a storage battery is used, (c) one or more lamps, and (d) a relaying device arranged to energize the lamps automatically upon failure of the normal supply to the building. The batteries shall be of suitable rating and capacity to supply and maintain at not less than 91 per cent of rated lamp voltage the total lamp load associated with the unit for a period of at least 1/2 hour. Storage batteries whether of the acid or alkali type shall be de- signed and constructed to meet the requirements of emergency service. When of the lead-acid type the storage battery shall have a transparent jar. Unit equipments shall be permanently fixed in place (i.e., not port- able) and shall have all wiring to each unit installed in accordance with the requirements of any of the wiring methods in Chapter 3. They shall not be connected by flexible cord. The supply circuit between the 70-374 NATIONAL ELECTRICAL CODE unit equipment and the service, feeders, or the branch circuit wiring shall be installed as required by Section 700-17. Emergency illumina- tion fixtures which obtain power from a unit equipment and are not part of the unit equipment shall be wired to the unit equipment as re- quired by Section 700-17 and by one of the wiring methods of Chapter 3. ARTICLE 710—OVER 600 VOLTS—GENERAL A. General 710-1. Scope. This Article applies in general to all circuits and equip- ment operated at more than 600 volts. For specific installation see the Articles referred to in Section 710-2. 710-2. Installations Covered in Other Articles. Provisions applicable to specific types of installations are included in Article 230, Services; Article 346, Rigid Metal Conduit; Article 347, Rigid Nonmetallic Conduit; Article 430, Motors, Motor Circuits and Controllers; Article 450, Transformers and Transformer Vaults; Article 460, Capacitors; Article 730, Outside Branch Circuits and Feeders; Article 410, Light- ing Fixtures, Lampholders, Lamps, Receptacles and Rosettes; Article 600,Electric Signs and Outline Lighting;Article 660,X-ray Equipment, and Article 665, Inductive and Dielectric Heat Generating Equipment. 710-3. Wiring Methods. (a) Aboveground Conductors. They shall be installed in rigid metal conduit, in other suitable raceways or as open runs of metal armored cable suitable for the use and purpose. In locations accessible to qualified persons only, open runs of non- metallic sheathed cable, bare conductors and bare bus bars may also be used. (b) Underground Conductors. Conductors shall be suitable for the voltage and conditions under which they are installed. Conductors in- stalled in rigid metal conduit or direct burial cable, if of the construc- tion where the energized conductors are surrounded by effectively grounded multiple concentric conductors, closely and evenly spaced circumferentially and meeting the requirements of Section 250-51 shall be buried at least 30 inches deep.Where other wiring methods are used the conductors shall be at a minimum depth of 42 inches and preferably at least 6 inches below other utilities. Exception No. 1. Under streets or roadways—conductor depth may be reduced to 24 inches if installed in rigid metal conduit. Exception No. 2. Airport runways—in airport runways, including adjacent defined areas where trespass is prohibited, cable may be buried no less than 18 inches deep and without raceways or concrete encase- ment. Exception No. 3. Lesser depths for unusual conditions—the above depths may be reduced 12 inches for each additional 2 inches of pro- tective layer of concrete above the conductors. ARTICLE 710—OVER 600 VOLTS—GENERAL 70-375 710-4. Braid-Covered Insulated Conductors — Open Installation. Open runs of braid-covered insulated conductors shall have a flame-retard- ant braid. When the conductors used do not have this protection, a flame-retardant saturant shall be applied to the braid covering after in- stallation. This treated braid covering shall be stripped back a safe distance at conductor terminals, according to the operating voltage. This distance should be not less than one inch for each kilovolt of the conductor-to-ground voltage of the circuit,where practicable. 710-5. Shielding of Solid Dielectric Insulated Conductors. Where solid dielectric-insulated conductors for permanent installations operate at voltages higher than those indicated in Table 710-5 and under the con- ditions mentioned, they shall be of a type having shielding for the pur- pose of confining their dielectric field. Table 710-5 Shielding of Solid Dielectric Insulated Conductors Voltage in Kv(L-L)Above which Shielding is Required Neutral Grounded Neutral Ungrounded Ozone- Ozone- Method of Installation Resistant Resistant Fibrous Jacket Fibrous Jacket Covered Covering Covered Covering In metallic conduit or trough above grade lo- cated indoors and in dry locations Single conductor . ... 2 5* 2 3 Multi-conductor .... 2 5 2 5 Underground ducts and conduits and other wet locations Single conductor .... 2 3** 2 3 Multi-conductor .... 2 5 2 5 On insulators— Only multi-conductor Not required under 5 Kv. 3 5 Directly in soil— Single conductor .... — 3 — 3 Multi-conductor . ... — 5 — 5 * It is presumed that installation conditions will be such as to main- tain a high level of jacket surface resistivity and so minimize the pos- sibility of destructive discharge. Pulling dry or the use of insulating type pulling lubricants will help attain these conditions. Where surface con- tamination cannot be prevented and high surface resistivity cannot be maintained,metallic shielding shall be used at over 3 kv. NOTE: Sheathed single or 3 conductor cables require no shielding for volt- ages 5 kv and less. In the case of portable equipment cables it is good prac- tice to specify shielding for all voltages above 2 kv. **For three single conductor cables, cabled together without overall outer covering,the value is 5 kv. 70-376 NATIONAL ELECTRICAL CODE 710-6. Grounding of Shielding Tape. The metallic shielding or any other static voltage shields on shielded cable shall be stripped back to a safe distance according to the circuit voltage, at all terminations of the shielding, as in potheads and joints. At such points, suitable methods such as the use of potheads, terminators, stress cones or similar devices shall be employed for stress reduction and the metallic shielding tape shall be grounded. 710-7. Grounding. Wiring and equipment installations shall conform with the applicable provisions of Article 250. 710-8. Moisture or Mechanical Protection for Metal Sheathed Cables. Where cable conductors emerge from a metal sheath and where pro- tection against moisture or mechanical injury is necessary, the insula- tion of the conductors shall be protected by a pothead or other ap- proved means. B. Equipment—General Provisions 710-10. Indoor Installations. Indoor electrical equipment installations shall conform with Sections 710-10(a) and (b). (a) In Places Accessible to Unqualified Persons. Electrical installa- tions which are open to unqualified persons shall be made with metal enclosed equipments or shall be enclosed in a vault or in an area access to which is controlled by a lock. Metal-enclosed switch-gear, unit sub- stations, transformers, pull boxes, connection boxes, and other similar associated equipment shall be marked with appropriate caution signs. Openings in ventilated dry-type transformers or similar openings in other equipment shall be designed so that foreign objects inserted through these openings will be deflected from energized parts. (b) In Places Accessible to Qualified Persons Only. Electrical installa- tions shall conform with Sections 710-31 to 710-34 inclusive. 710-11. Outdoor Installations. Outdoor installations having exposed live parts shall be accessible to qualified persons only. Installations are considered to be accessible to qualified persons only where enclosed as provided in Section 710-31 or when isolated by elevation. Live parts are deemed to be isolated by elevation (1) where the clearance to ground and to buildings conforms with Article 730 for outdoor installations, and (2) as provided in Section 710-34(f) for locations accessible to qualified persons only. 710-12. Metal Enclosed Equipments. Installations consisting of metal enclosed equipments such as metal clad switchgear, transformers, and the like, which have no exposed live parts, need not comply with Sec- tion 710-31. Ventilating or similar openings in equipment shall be so designed that foreign objects inserted through these openings will be de- flected from energized parts. Where exposed to physical damage from vehicular traffic suitable guards shall be provided. C. Equipment—Specific Provisions See also references to specific types of installations in Section 710-2. 710-21. Circuit Interrupting Devices. (a) Circuit Breakers. (1) Indoor installations shall consist of metal-enclosed units or ARTICLE 710—OVER 600 VOLTS—GENERAL 70-377 fire-resistant cell-mounted units except that open mounting of circuit breakers is permissible in locations accessible to qualified persons only. (2) Circuit breakers shall be trip-free in all positions. In every in- stallation the circuit breaker rating in respect to closing, carrying or in- terrupting capabilities shall not be less than the short circuit duty at the point of application. (3) Circuit breakers used to control oil-filled transformers should be located outside the transformer vault. (4) Circuit breakers shall have a means of indicating the open and closed position of the breaker at the point(s) from which they may be operated. (5) Oil circuit breakers shall be so arranged or located that adjacent readily combustible structures or materials are safeguarded in an ap- proved manner. Adequate space separation,fire-resistant barriers or en- closures, trenches containing sufficient coarse crushed stone and prop- erly drained oil enclosures such as dikes or basins are recognized as suitable for this purpose. (b) Fuseholders and Fuses. (1) Fuses which expel flame in opening the circuit shall be so de- signed or arranged that they will function properly without hazard to persons or property. (2) Fuseholders shall be designed so that they can be de-energized while replacing a fuse unless the fuse and fuseholder are designed to permit fuse replacement by qualified persons using equipment designed for the purpose without de-energizing the fuseholder. (3) When high voltage fused cutouts are installed in a building or a transformer vault, they shall be of a type designed for use in build- ings. Where such cutouts are not suitable to interrupt the circuit man- ually while carrying full load, an approved switch or contactor shall be provided which is capable of interrupting the entire load. In addi- tion, the cutouts shall be interlocked with the approved interrupter or bear a conspicuous sign reading"Do Not Open Cutout Under Load." The cutouts shall be so located that they may be readily and safely operated and re-fused. Fuses shall be accessible from a clear floor space. (c) Load Interrupters. Load interrupter switches may be used pro- viding suitable fuses or circuit breakers are applied in conjunction with these devices to interrupt fault currents. When these devices are used in combination they shall be so coordinated electrically that they will safely withstand the effects of closing, carrying or interrupting all pos- sible currents up to the assigned maximum short circuit rating. 710-22. Isolating Means. Means shall be provided to completely isolate an item of equipment. The use of isolating switches is not nec- essary where there are other ways of de-energizing the equipment for inspection and repairs such as metal-enclosed switchgear units, and removable truck panels. Isolating switches should be interlocked with the associated circuit interrupting device to prevent their being opened under load, otherwise signs warning against opening them under load 70-378 NATIONAL ELECTRICAL CODE shall be provided. Barriers should be provided on both sides of each pole of indoor open-type isolating switches. A fuseholder and fuse, de- signed for the purpose,may be used as an isolating switch. D. Installations Accessible To Qualified Persons Only 710-31. Enclosure for Electrical Installations. Electrical installations in a vault, room, closet or in an area surrounded by a wall, screen or fence, access to which is controlled by lock and key or other approved means, are considered to be accessible to qualified persons only. The height of the wall, screen or fence should not be less than eight feet over-all, unless designed to provide an equivalent degree of isolation. The type of enclosure used in a given case shall be designed and con- structed according to the nature and degree of the hazard(s) associ- ated with the installation. Article 450 covers minimum construction requirements for oil-filled transformer vaults. Isolation by elevation is covered in Sections 710-11 and 710-34. 710-32. Circuit Conductors. They may be installed in conduit; in duct systems; as metal-clad cable; as bare wire, cable and buses, or as nonmetallic sheathed cables or conductors as provided in Sections 710-3 to 710-6 inclusive. Bare live conductors shall conform with Sections 710-33 and 710-34. Insulators, together with their mounting and conductor attachments, when used as supports for wires, single conductor cables and bus-bars, shall be capable of safely withstanding the maximum magnetic forces which would prevail when two or more conductors of a circuit were subjected to short-circuit current. Open runs of insulated wires and cables, having a bare lead sheath or a braided outer covering, shall be supported in a manner designed to prevent physical damage to the braid or sheath. Supports for lead cov- ered cables shall be designed to prevent electrolysis of the sheath. 710-33. Minimum Space Separation Between Live Parts and Adjacent Surfaces. The minimum indoor air separation between bare live con- ductors and between such conductors and adjacent surfaces shall be not less than the values given below. This Section applies to interior Table 710-33. Minimum Air Separation in Inches,Indoors* Between Bare Live Circuit Between Bare Live Conductors and Voltage,kV Conductors Adjacent Surfaces 2.5 5 4 5.0 6 5 7.5 7 6 15.0 12 7 23.0 15 10 34.5 18 13 46.0 21 17 69.0 31 25 *The values given are the minimum permissible space separation under favorable service conditions. They should be increased under unfavorable service conditions or wherever space limitations permit. ARTICLE 710—OVER 600 VOLTS—GENERAL 70-379 wiring design and construction.It does not apply to the space separation provided in electrical apparatus and wiring devices. 710-34. Work Space and Guarding. (a) Working Space. The minimum clear working space in front of electrical equipment, such as switchboards, control panels, switches, circuit breakers, motor controllers, relays and similar equipment shall not be less than set forth in the following table unless otherwise speci- fied in this Code. Table 710-34(a) Minimum Clear Working Space in Front of Electrical Equipment Voltage to Ground Conditions 1 2 3 601-2500 3 ft. 4 ft. 5 ft. 2501-7500 4 ft. 5 ft. 6 ft. over 7500 5 ft. 6 ft. 9 ft. Where the"Conditions"are as follows: (1) Exposed live parts on one side and no live or grounded parts on the other side of the working space or exposed live parts on both sides effectively guarded by suitable wood or other insulating materials. Insulated wire or insulated bus bars operating at not more than 300 volts shall not be considered live parts. (2) Exposed live parts on one side and grounded parts on the other side. Concrete, brick or tile walls will be considered as grounded sur- faces. (3) Exposed live parts on both sides of the work space (not guarded as provided in Condition 1) with the operator between. Exception: Working space is not required in back of assemblies such as dead-front switchboards or control assemblies when there are no renewable or adjustable parts such as fuses or switches on the back and when all connections are accessible from other locations than the back. (b) Separation from Low-Potential Equipment. When switches, cut- outs or other equipment operating at 600 volts or less are installed in a room or enclosure where there are exposed live parts or exposed wiring operating at more than 600 volts the high potential equipment shall be effectively separated from the space occupied by the low po- tential equipment by a suitable partition,fence,or screen. Exception: Switches or other equipment operating at 600 volts or less and serving only equipment within the high-voltage vault, room or enclosure may be installed in the high-voltage enclosure, room or vault if accessible to qualified persons only. (c) Locked Rooms or Enclosures. The entrances to all buildings, rooms or enclosures containing exposed live parts or exposed conduc- tors operating in excess of 600 volts shall be kept locked, except where such entrances are at all times under the observation of a qualified at- tendant. 70-380 NATIONAL ELECTRICAL CODE Where the voltage exceeds 600 volts permanent and conspicuous warning signs shall be provided, reading substantially as follows: "Warning—High Voltage—Keep Out." (d) Illumination. Adequate illumination shall be provided for all working spaces about electrical equipment. The light outlets shall be so arranged that persons changing lamps or making repairs on the light- ing system will not be endangered by live parts or other equipment. The points of control shall be so located that persons are not liable to come into contact with any live part or moving part of the equip- ment while turning on the lights. (e) Headroom. The minimum headroom above working spaces about switching equipment where there are live parts exposed at any time shall be not less than 61/2 feet. (f) Elevation of Unguarded Live Parts. Unguarded live parts above working space shall be maintained at elevations not less than required by the following table. Table 710-34(f) Elevation of Unguarded Live Parts Above the Working Space Minimum Vertical Clearance of Voltage Between Phases Unguarded Parts Feet Inches 601-6600 8 0 6601-11000 9 0 11001-22000 9 3 22001-33000 9 6 33001-44000 9 10 44001-66000 10 5 66001-88000 11 0 88001-110000 11 7 110001-132000 12 2 ARTICLE 720—CIRCUITS AND EQUIPMENT OPERATING AT LESS THAN 50 VOLTS 720-1. General. This Article shall apply to installations operating at less than 50 volts,direct current or alternating current,except such as are treated in Articles 650 and 725. 720-2. Hazardous Locations. Circuits or equipment coming within the scope of this Article and installed in hazardous locations shall comply with the appropriate provisions of Articles 500-517 inclusive. 720-3. Larger Current at Lower Voltage. Conductors, devices, and equipment shall have current ratings sufficient for the greater current required to deliver equal power at the lower voltage than at usual volt- ages. ARTICLE 725—REMOTE-CONTROL AND SIGNAL CIRCUITS 70-381 720-4. Conductors. Conductors shall be not smaller than No. 12 AWG copper or equivalent, and for appliance branch circuits supplying more than one appliance, or appliance receptacle, conductors shall be not smaller than No. 10 AWG copper or equivalent. 720-5. Lampholders. Standard lampholders of rating not less than 660 watts shall be used. 720-6. Receptacle Rating. Receptacles shall have a rating not less than 15 amperes. 720-7. Receptacles Required. Receptacles of not less than 20-ampere rating shall be provided in kitchens,laundries,and other locations where portable appliances are likely to be used. 720-8. Overcurrent Protection. Overcurrent protection shall comply with the provisions of Article 240. 720-9. Batteries. See Article 480. 720-10. Grounding. See Sections 250-8 and 250-45. ARTICLE 725—REMOTE-CONTROL, LOW- ENERGY POWER, LOW-VOLTAGE POWER, AND SIGNAL CIRCUITS A. Scope and General 725-1. Scope. Provisions of this Article shall apply to remote-control circuits, including low-voltage relay switching, low-energy power cir- cuits, low-voltage circuits, and signal circuits, as defined in Article 100, Definitions. The provisions of this Article are not intended to apply to remote-control, low-energy or signal circuits which form an integral part of a device or ap- pliance. 725-2. Hazardous Locations. Circuits or equipment coming within the scope of this Article and installed in hazardous locations shall also comply with the appropriate provisions of Articles 500-517 inclusive. 725-3. Classification. Remote-control and signal circuits shall be clas- sified as follows: (a) Class 1 Circuits. Control and signal circuits in which power is not limited in accordance with Section 725-31. (b) Class 2 Circuits. Control and signal circuits in which the power is limited in accordance with Section 725-31. 725-4. Low-Energy Power Circuits. Circuits which are neither remote- control nor signal circuits, but which have the power limited in accord- ance with Section 725-31 shall, for the purpose of this Code, be treated as Class 2 remote-control circuits. 70-382 NATIONAL ELECTRICAL CODE 725-5. Low-Voltage Power Circuits. Circuits which are neither remote- control nor signal circuits but which operate at not more than 30 volts, where the current is not limited in accordance with Section 725-31, and which are supplied from a source not exceeding 1000 volt-amperes shall for the purpose of this Code be treated as Class 1 remote-control circuits. 725-6. Safety-Control Devices. Remote-control circuits to safety-con- trol devices, the failure of operation of which would introduce a direct fire or life hazard, shall be considered as Class 1 circuits. Room thermostats, service hot-water temperature regulating devices, and similar controls used in conjunction with electrically controlled domestic heating equipment,are not considered to be safety-control devices. 725-7. Remote-Control and Signal Circuits in Communication Cables. Remote-control and signal circuits, which use conductors in the same cable with communication circuits, shall, for the purpose of this Article, be classified as communication circuits and meet the requirements of Article 800,of this Code. B. Class 1 System 725-11. Wiring Method. Conductors and equipment of Class 1 re- mote-control and signal systems and low voltage power circuits shall be installed in accordance with the requirements of the appropriate Articles in Chapter 3 of this Code, except as provided in Sections 725-12 to 725-15 inclusive. 725-12. Other Articles. The wiring method required in Section 725-11 does not apply where other Articles of this Code specifically permit or , require other methods for remote-control or signal circuits. See Article 620,Elevators,for example. 725-13. Conductor Sizes. Nos. 18 and 16 gage conductors may be used provided they are installed in a raceway or a cable approved for the purpose, or in flexible cords in accordance with the provisions of Article 400. 725-14. Conductor Insulation. Conductors larger than No. 16 shall be thermoplastic-covered Type T, or other approved type. Fixed conduc- tors Nos. 18 and 16 gage shall have an insulation at least equal to that of Type TF thermoplastic-covered fixture wire. Conductors approved for the purpose having insulation of a thickness less than specified above or having other kinds of insulation may be used. 725-15. Number and Ampacities of Conductors in Raceways. (a) Where only remote control or signal circuits are in a raceway, the number of conductors shall be determined in accordance with Sec- tion 300-17. Note 8 to Tables 310-12 through 310-15 shall apply only if such conductors carry continuous loads. (b) Where power supply conductors and Class 1 system conductors are permitted in a raceway in accordance with Section 725-16, Note 8 to Tables 310-12 through 310-15 shall apply as follows: (1) To all conductors when the Class 1 system conductors carry continuous loads and when the total number of conductors are more than three. ARTICLE 725—REMOTE CONTROL AND SIGNAL CIRCUITS 70-383 (2) To the power supply conductors only, when the Class 1 sys- tem conductors do not carry continuous loads and when the number of power supply conductors are more than three. 725-16. Conductors of Different Systems. Conductors of two or more Class 1 remote-control and/or signal circuits may occupy the same en- closure or raceway without regard to whether the individual systems or circuits are alternating or direct current, provided all conductors are insulated for the maximum voltage of any conductor in the enclosure or raceway. Conductors of remote-control, low-energy power and sig- nal circuits, in which the current is limited as for Class 2 systems, shall be considered as Class 1 system conductors for the purpose of this re- quirement if insulated and installed in accordance with the provisions for Class 1 system conductors. Power supply conductors may occupy the same enclosure or raceway with Class 1 system conductors when supplying only equipment to which Class 1 system conductors are connected. 725-17. Mechanical Protection of Remote-Control Circuits. Where dam- age to a remote-control circuit would introduce a hazard as covered in Section 725-6, all conductors of such remote-control circuits shall be installed in conduit, electrical metallic tubing, Type MI cable or be otherwise suitably protected from physical damage. 725-18. Overcurrent Protection. Conductors shall be protected against overcurrent in accordance with the ampacities of Tables 310-12 through 310-15 except as follows: Exception No. 1. Other Articles. Where other Articles of this Code specifically permit or require other overcurrent protection. See Sections 430-72 and 620-61. Exception No. 2. Conductors of Nos. 18 and 16. Conductors of Nos. 18 and 16 shall be considered as protected by overcurrent devices of 20- ampere rating or setting. Exception No. 3. Omission of Overcurrent Protection. In remote- control and signal circuits having main and branch circuits, the branch circuits need not be individually protected against overcurrent where the operating voltage does not exceed 30 volts. 725-19. Location of Overcurrent Protection. Overcurrent devices shall be located at the point where the conductor to be protected receives its supply unless the overcurrent device protecting the larger conductor also protects the smaller conductor in accordance with Tables 310-12 through 310-15. 725-20. Circuits Extending Beyond One Building. Class 1 circuits which. extend aerially beyond one building shall also meet the requirements of Article 730. 725-21. Grounding. Class 1 remote-control and signal circuits and equipment shall be grounded in accordance with Article 250. C. Limitation of Low-Voltage Power Circuit 725-22. Overcurrent Protection. Transformer devices supplying low- voltage power circuits shall be provided with overcurrent protection in 70-384 NATIONAL ELECTRICAL CODE the secondary circuit rated or set at not more than 250 per cent of the rated secondary current of the transformer.Such protection and mount- ing shall be approved for the purpose. Overcurrent protection required shall not be interchangeable with protection of a higher rating. The overcurrent protection may be an integral part of a transformer or other power supply device approved for the purpose. 725-23. Transformer Rating. Transformer devices supplying low-volt- age power circuits shall be approved for the purpose and be restricted in their rated output to not exceeding 1000 volt-amperes and to not exceeding 30 volts. They shall be marked where plainly visible to show their rated output and the voltage to be applied to the circuit. A transformer is considered as meeting the 1000 volt-ampere requirement where the approximate temperature limit is reached at 1000 volt-ampere load. D. Class 2 System Voltage and Current Limits 725-31. Limits of Class 2 Systems. Class 2 remote-control and signal systems, depending on the voltage shall have the current limited as fol- lows: (a) Maximum 15 Volts: 5 Amperes. Circuits in which the open-cir- cuit voltage does not exceed 15 volts and having overcurrent protec- tion of not more than 5-amperes rating. Where the current supply is from a transformer or other device having energy-limiting character- istics and approved for the purpose, or from primary batteries, the overcurrent protection may be omitted. (b) 15 to 30 Volts: 3.2 Amperes. Circuits in which the open-circuit voltage exceeds 15 volts but does not exceed 30 volts and having over- current protection of not more than 3.2 amperes rating. Where the current supply is from a transformer or other device having energy- limiting characteristics and approved for the purpose, or from primary batteries,the overcurrent protection may be omitted. (c) 30 to 60 Volts: 1.6 Amperes. Circuits in which open-circuit voltage exceeds 30 volts but does not exceed 60 volts and having over- current protection of not more than 1.6 amperes rating. Where the current supply is from a transformer or other device having energy- limiting characteristics and approved for the purpose, the overcurrent protection may be omitted. (d) 60 to 150 Volts: 1 Ampere. Circuits in which the open-circuit voltage exceeds 60 volts but does not exceed 150 volts,and having over- current protection of not more than 1-ampere rating,provided that such circuits are equipped with current-limiting means other than overcur- rent protection which will limit the current as a result of a fault to not exceeding 1 ampere. (e) Maximum 150 Volts: 5 Milliamperes. Circuits in which the open circuit voltage does not exceed 150 volts provided that such circuits are equipped with current limiting means, other than overcurrent protec- tion, which are approved for the purpose and which will limit the cur- rent as a result of a fault to not exceeding 5 milliamperes. ARTICLE 725—REMOTE-CONTROL AND SIGNAL CIRCUITS 70-385 725-32. Overcurrent Protection and Mounting. Where current is lim- ited in Class 2 systems by means of overcurrent protection, such pro- tection and its mounting shall be approved for the purpose. Overcur- rent protection required shall not be interchangeable with protection of a higher rating. The overcurrent protection may be an integral part of a transformer or other power supply device approved for the purpose. 725-33. Transformer Rating. Transformer devices supplying Class 2 systems shall be approved for the purpose and be restricted in their rated output to not exceeding 100 volt-amperes. Such devices shall not be paralleled or otherwise interconnected. They shall be marked where plainly visible to show the voltage to be applied to the circuit. A transformer is considered as meeting the 100 volt-ampere requirement if the approximate temperature limit is reached at a 100-volt-ampere load. 725-34. Transformer Leads. The primary leads of transformers sup- plying Class 2 remote-control and signal circuits may be smaller than No. 14 but not smaller than No. 18, provided they are not over 12 inches long, have insulation at least equal to type RF-2 rubber-cov- ered fixture wire,or approved equivalent. E. Installation of Class 2 Remote-Control and Signal Circuits 725-41. On Supply Side of Overcurrent Protection, Transformers or Current-Limiting Devices. Conductors and equipment on supply side of overcurrent protection, transformers or current-limiting devices shall be installed in accordance with the appropriate requirements of Chap- ter 3 of this Code. Transformers or other devices supplied from elec- tric light and power circuits shall be protected by an overcurrent device with a rating or setting not exceeding 20 amperes. 725-42. On Load Side of Overcurrent Protection, Transformer or Current- Limiting Devices. Conductors on load side of overcurrent protection, transformer or current-limiting devices shall be insulated and shall comply with the following: (a) Separation from Other Conductors. Conductors shall be sepa- rated from conductors of electric light and power circuits as follows: (1) Open Conductors. Conductors shall be separated at least two inches from any light or power conductors or Class 1 signal or control circuits not in a raceway nor in metal sheathed, metal-clad, nonmetallic sheathed or Type OF cables unless permanently separated from the con- ductors of the other system by a continuous and firmly fixed non-con- ductor, such as porcelain tubes or flexible tubing, additional to the in- sulation on the wire. (2) In Raceways and Boxes. Conductors of Class 2 remote- control and signal circuits shall not be placed in any raceway, compart- ment, outlet box or similar fitting with conductors for either light and power circuits or Class 1 signal and control.circuits, unless the conduc- tors of the different systems are separated by a partition; provided that this shall not apply to conductors in outlet boxes, junction boxes or similar fittings or compartments where power supply conductors are introduced solely for supplying power to the remote-control or signal 70-386 NATIONAL ELECTRICAL CODE equipment to which the other conductors in the enclosure are con- nected. (See Section 725-16.) (3) In Shafts. Conductors may be run in the same shaft with conductors for light and power where the conductors of the two sys- tems are separated at least 2 inches, or where the conductors of either system are encased in noncombustible tubing. Where the lighting or power conductors are run in a raceway, or in metal sheathed or metal- clad or nonmetallic sheathed or Type OF cables, neither the two inch separation nor the non-combustible tubing is required. In hoistways conductors shall be installed in rigid conduit or electrical metallic tubing except as provided for in Section 620-21,Exception No. 1. (b) Vertical Runs. Conductors in a vertical run in a shaft or parti- tion shall have a fire resistant covering capable of preventing the carry- ing of fire from floor to floor except where conductors are encased in tubing or other outer covering of noncombustible material or are lo- cated in a fireproof shaft having fire stops at each floor. Where 3 or more conductors are used, it is recommended that such con- ductors be grouped under a common braid or covering. (c) Conductor Insulation. Conductor insulation shall comply with the following: (1) 30 Volts or Less. The insulation shall be suitable for the par- ticular application. The kind of insulation for the conductors is not specified in further detail as reliance is placed on current limitation to stop dangerous currents. (2) 30 to 150 Volts Maximum Fault Current 5 Milliamperes. The insulation shall be suitable for the particular application. The kind of insulation for the conductors is not specified in further detail as reliance is placed on current limitation to stop dangerous currents. (3) 30 to 150 Volts. Greater than 5 Milliamperes. Conductors of a cable shall be of solid or stranded copper not smaller than No. 22 AWG, and shall have thermoplastic insulation of not less than 0.012 inch nominal (0.010 inch minimum) thickness. The cable conductors shall have a thermoplastic jacket overall having a nominal thickness of not less than 0.035 inch (0.030 inch minimum). Where the number of conductors in a cable exceeds 4, the thickness of the thermoplastic jacket overall shall be increased so as to provide equivalent performance characteristics. Similarly, where the size of conductors in a cable ex- ceeds No. 16 gage, the thickness of the conductor insulation shall be increased so as to provide equivalent performance characteristics. Two-conductor assemblies of No. 16 gage or smaller, may be in a flat parallel construction with 1/32 inch nominal integral-insulation jacket and an 0.047 inch minimum web. Approved low-energy circuit cable may be used. Other insulation having equivalent performance characteristics may be acceptable. Where single conductors are used they shall be not smaller than No. 18 AWG and shall be insulated in conformity with Section 725-14. ARTICLE 730—OUTSIDE BRANCH CIRCUITS AND FEEDERS 70-387 725-43. Circuits Extending Beyond One Building. Class 2 remote- control and signal circuits which extend beyond one building and are so run as to be subject to accidental contact with light or power conduc- tors operating at a potential exceeding 300 volts, shall also meet the re- quirements of Sections 800-2,800-11 and 800-12. 725-44. Grounding. Class 2 remote-control and signal circuits and equipment shall be grounded in accordance with Article 250. ARTICLE 730—OUTSIDE BRANCH CIRCUITS AND FEEDERS 730-1. Scope. This Article applies to electrical equipment and wiring for the supply of utilization equipment located on or attached to the outside of public and private buildings, or run between buildings, struc- tures or poles on other premises served; but shall not apply to equip- ment or wiring of an electric or communication utility used in the ex- ercise of its function as a utility. 730-2. Application of Other Articles. Application of other Articles, including additional requirements to specific cases of equipment and conductors,are as follows: Articles 200—Polarity Identification. 210—Branch Circuits. 215—Feeders. 230—Services. 250—Grounding. 500—Hazardous Locations,General. 510—Hazardous Locations,Specific. 600—Signs and Outline Lighting. 710—Circuits and Equipment Operating at More than 600 Volts. 725—Remote Control and Signal Circuits. 800—Communication Circuits. 810—Radio and Television Circuits. 730-3. Calculation of Load. (a) Branch Circuits. The load on every outdoor branch circuit is to be determined by the applicable provisions of Article 220. (b) Feeders. The load to be expected on every outdoor feeder is to be determined by the procedure specified in Article 220. 730-4. Conductor Covering. Where within 10 feet of any building or structure, open conductors supported on insulators shall be insulated or covered. Conductors in cables or raceways, except Type MI Cable, shall be of the rubber-covered type or thermoplastic type and in wet lo- cations shall comply with Section 310-5. Conductors for festoon light- ing shall be of the rubber-covered or thermoplastic type. 730-5. Size of Conductors. The ampacity of outdoor branch circuits and feeder conductors shall be according to the rating in Tables 310-12 70-388 NATIONAL ELECTRICAL CODE through 310-15 in order to carry the loads determined under Section 730-3. 730-6. Minimum Size of Conductor. (a) Overhead Spans. Overhead conductors shall not be smaller than No. 10 for spans up to 50 feet in length, and not smaller than No. 8 for longer spans. (b) Festoon Lighting. Overhead conductors for festoon lighting shall not be smaller than No. 12 unless supported by messenger wires. (See Section 730-25.) DEFINITION: Festoon lighting is a string of outdoor lights suspended between two points more than 15 feet apart. (c) Over 600 Volts. Overhead conductors operating at more than 600 volts shall not be smaller than No. 6 when open individual con- ductors nor smaller than No. 8 when in cable. 730-7. Lighting Equipment on Poles or Other Structures. (a) For the supply of lighting equipment installed on a single pole or structure, the branch circuits shall comply with the requirements of Article 210 and Paragraph (c) below. (b) A common neutral may be used for a multiwire branch circuit consisting of the neutral and not more than 8 ungrounded conductors. The ampacity of the neutral conductor shall be not less than the calcu- lated sum of the currents in all ungrounded conductors connected to any one phase of the circuit. (c) Branch circuits supplying only ballasts for permanently installed electric discharge lighting fixtures for area illumination mounted on poles clear of buildings or on other structures may operate at not to ex- ceed 500 volts between conductors,provided: (1) Fixtures on poles are mounted at a height of 22 feet or more and on other structures at a height of 18 feet or more. (2) The wiring system is grounded wherever auto-transformers supplied therefrom raise the voltage to a value greater than the supply circuit voltage. 730-8. Disconnection. (a) For branch circuits as required in Article 210. (b) For feeders as required in Article 215. (At each building supplied by a feeder see Section 230-76.) 730-9. Overcurrent Protection. (a) For branch circuits as required in Article 210. (b) For feeders as required in Article 215. 730-10. Wiring on Buildings. Outside wiring on surfaces of buildings may be installed for circuits when not in excess of 600 volts as open conductors on insulating supports,as multiple-conductor cable approved for the purpose, as aluminum sheathed cable or MI cable, in rigid metal conduit, in busways as provided in Article 364, or in electrical metallic tubing. Circuits of more than 600 volts shall be installed as provided for services in Section 230-101. Circuits for sign and outline lighting shall be installed as provided in Article 600. ARTICLE 730—OUTSIDE BRANCH CIRCUITS AND FEEDERS 70-389 730-11. Circuit Exits and Entrances. Where outside branch and feeder circuits exit from or enter into buildings the installation shall comply with those requirements of Article 230 which apply to service entrance conductors. 730-12. Open Conductor Supports. Open conductors shall be sup- ported on glass or porcelain knobs, racks, brackets, or strain insulators, approved for the purpose. 730-13. Festoon Supports. In spans exceeding 40 feet the conductors shall be supported by a messenger wire supported by approved strain insulators. Conductors or messenger wires shall not be attached to any fire escape,downspout,or plumbing equipment. 730-14. Open Conductor Spacings. Conductors shall conform to the following spacings: (a) Open Conductors Exposed to the Weather. As provided in Sec- tion 230-47. (b) Open Conductors Not Exposed to Weather. As provided in Sec- tion 230-48. (c) Over 600 Volts. As provided in Section 230-101(c). (d) Separation from Other Circuits. Open conductors shall be sep- arated from open conductors of other circuits or systems by not less than 4 inches. (e) Conductors On Poles. Conductors on poles shall have a separa- tion of not less than 1 foot except when placed on racks or brackets. Conductors supported on poles shall provide a horizontal climbing space not less than the following: Power conductors,below communication conductors 30 inches Power conductors alone or above communication conductors: Less than 300 volts 24 inches Exceeding 300 volts 30 inches Communication conductors below power conductors same as power conductors Communication conductors alone or above power conductors no requirement 730-15. Supports Over Buildings. See Section 230-25. 730-16. Point of Attachment to Buildings. See Section 230-26. 730-17. Means of Attachment to Buildings. See Section 230-27. 730-18. Clearance from Ground. Open conductors of not over 600 volts shall conform to the following: 10 feet—above finished grade, sidewalks or from any platform or projection from which they might be reached; 12 feet—over residential driveways and commercial areas such as parking lots and drive-in establishments not subject to truck traffic; 70-390 NATIONAL ELECTRICAL CODE 15 feet—over commercial areas, parking lots, agricultural or other areas subject to truck traffic; 18 feet—over public streets, alleys, roads, and driveways on other than residential property. NOTE: For clearances of conductors of over 600 volts see National Electri- cal Safety Code. 730-19. Clearances from Buildings for Conductors not in Excess of 600 Volts. (a) Clearance Over Roof. Open conductors shall have a clearance of not less than 8 feet from the highest point of roofs over which they pass with the following exceptions: Exception No. 1. Where the voltage between conductors does not exceed 300 volts and the roof has a slope of not less than 4 inches in 12 inches,the clearance may be not less than 3 feet. Exception No. 2. Open conductors of 300 volts or less which do not pass over other than a maximum of 4 feet of the overhang portion of the roof for the purpose of terminating at a through-the-roof raceway or approved support may be maintained at a minimum of 18 inches from any portion of the roof over which they pass. For Service Drop Conductors see Section 230-22(a). (b) Horizontal Clearances. Open conductors not attached to a build- ing shall have a minimum horizontal clearance of 36 inches. (c) Final Spans. Final spans of feeders or branch circuits to build- ings which they supply or from which they are fed may be attached to the building but they shall be kept 3 feet from windows, doors,porches, fire escapes or similar locations. (d) Zone for Fire Ladders. Where buildings exceed 3 stories, or 50 feet in height, overhead lines shall be arranged where practicable so that a clear space (or zone) at least 6 feet wide will be left either ad- jacent to the buildings or beginning not over 8 feet from them, to facili- tate the raising of ladders when necessary for fire fighting. Note: For clearance of conductors over 600 volts, consult National Elec- trical Safety Code. 730-20. Mechanical Protection of Conductors. Mechanical protection of conductors on buildings, structures or poles shall be as provided for services,Section 230-46. 730-21. Conductors Entering Buildings. Conductors entering buildings shall be as provided for services,Sections 230-44, 230-49,and 230-51. 730-22. Multiple Conductor Cables on Exterior Surfaces of Buildings. Multiple conductor cables on exterior surfaces of buildings shall be as provided for service cable,Section 230-50. 730-23. Raceways on Exterior Surfaces of Buildings. Raceways on exterior surfaces of buildings shall be made raintight and suitably drained. 730-24. Underground Circuits. Underground circuits shall be as pro- vided for services,Sections 230-32 and 230-33. ARTICLE 750—STAND-BY POWER SYSTEMS 70-391 730-25. Outdoor Lighting Equipment — Lampholders. Lampholders shall be of molded composition, or other approved material of the weatherproof type, and where they are attached as pendants shall have the connections to the circuit wires staggered. Where lampholders have terminals of a type which puncture the insulation and make contact with the conductors, they shall be attached only to conductors of the stranded type. 730-26. Outdoor Lighting Equipment — Location of Lamps. Location of lamps for outdoor lighting shall be below all live conductors, trans- formers, or other electrical equipment, unless clearances or other safe- guards are provided for relamping operations, or unless the installation is controlled by a disconnecting means which can be locked in the open position. ARTICLE 750—STAND-BY POWER GENERATION SYSTEMS 750-1. Scope. The provisions of this Article apply to the installation, operation, and maintenance of circuits,systems and equipment intended to supply on-site generated power to selected loads (other than those of Article 700 Emergency Systems), automatically or manually, in the event of failure of the normal source of electrical service. Stand-by systems are generally installed to provide an alternate source of electrical energy to serve loads, such as heating and refrigeration sys- tems,communications systems,industrial processes which,when stopped during any power outage, could cause discomfort, serious interruption of the process,or damage to the product or process or the like. The systems covered by this Article shall consist only of those which are permanently installed in their entirety including the prime movers. 750-2. Other Requirements. All applicable requirements of this Code shall apply to the stand-by systems, except as modified by this Article. 750-3. Equipment Approval. All equipment shall be approved for the use intended. 750-4. Tests. The complete system after installation should be test operated as directed by the authority having jurisdiction. 750-5. Generator Set. A generator, driven by and connected to a per- manently installed prime mover shall comprise the generator set. 750-6. Capacity of the System. The stand-by system shall have ade- quate capacity and rating for the operation of all equipment to be sup- plied at one time. 750-7. Controls and Transfer Equipment. Equipment shall be suitable for intended use and be so designed and installed as to prevent the in- advertent interconnection of normal and stand-by sources of supply in any operation of the transfer equipment. 70-392 NATIONAL ELECTRICAL CODE A time delay feature should be provided to avoid short-time opera- tion of the stand-by system. 750-8. Systems Protection. Transfer equipment and wiring associated with the stand-by system shall be provided with suitably rated protective devices. 750-9. Wiring. The stand-by system wiring is not subject to the pro- visions of Section 700-17, and the wiring of this system may occupy the same raceways, boxes, cabinets, and panelboards with other wiring, except that the wiring shall not occupy the same raceways, boxes or cabinets as wiring for Emergency Systems. 70-393 Chapter 8. Communication Systems ARTICLE 800—COMMUNICATION CIRCUITS A. General 800-1. Scope. The provisions of this Article shall apply to telephone, telegraph (except radio), district messenger, fire and burglar alarms and similar central station systems and to telephone systems not con- nected to a central station system but using similar type of equipment, methods of installation and maintenance. Such protective measures as are essential to safeguard these systems un- der the various conditions to which they are subjected are outlined in these rules. For detailed requirements for fire alarm, sprinkler, supervisory, or watch- man systems,see the Standards of the National Fire Protection Association.* B. Protection 800-2. Protective Devices. A protector approved for the purpose shall be provided on each circuit, aerial or underground, so located within the block containing the building served as to be liable to accidental contact with light or power conductors operating at a potential exceed- ing 300 volts, and on each circuit run partly or entirely in aerial wire or cable not confined within a block. The word "block" as used in this Article shall be construed to mean a square or portion of a city, town, or village enclosed by streets and includ- ing the alleys so enclosed but not any street. (a) Location. The protector shall be located in or on the building as near as practicable to the point where the conductors enter. In the case of an underground entrance the protector may be located at the junction of the underground and the aerial wires. (b) Hazardous Locations. The protector shall not be located in any hazardous location as defined in Article 500, nor in the vicinity of eas- ily ignitible material. (c) Protector Requirements. The protector shall be mounted on a noncombustible, nonabsorptive insulating base and shall consist of an arrester between each line conductor and the ground, and a fuse in each line conductor, the fuses protecting the arrester except as spec- ified in Section 800-2(d). The protector terminals shall be plainly marked to indicate line,instrument,and ground. (d) Omission of Fuses. A protector without fuses may be used under any of the following conditions: *The NFPA standards on fire alarm and supervisory systems are pub- lished by the NFPA in the National Fire Codes, Vol. 7 and in separate pam- phlet form by the NFPA(NFPA Nos.71,72A,72B,72C,72D,and 73). 70-394 NATIONAL ELECTRICAL CODE (1) Where circuits enter a building through metal-sheathed cable, or through a nonmetallic sheathed cable having a metal grounding shield between the sheath and the conductor assembly, provided the metal sheath or shield of the cable is effectively grounded and the con- ductors in the cable shall safely fuse at currents less than the ampacity of the protector,and the protector grounding conductor. (2) Where insulated conductors in accordance with Sections 800- 11(c)(1) or 800-11(c)(2) are used to extend circuits to a building from a metal-sheathed cable or from a nonmetallic-sheathed cable having a metal grounding shield between the sheath and the conductor assembly provided the metal sheath or shield is effectively grounded and the conductors in the cable or cable stub shall safely fuse at currents less than the ampacity of the protector, the associated insulated con- ductors,and the protector grounding conductor. (3) Where insulated conductors, in accordance with Sections 800- 11(c)(1) or 800-11(c)(2) are used to extend circuits to a building from other than grounded metal-sheathed or shielded cable, provided (a) the protector is approved for this purpose and (b) the protector grounding conductor is connected to a water pipe electrode or the grounding conductor or grounding electrode of a multi-grounded neutral power system and (c) the connections of the insulated conductors to the exposed plant or the conductors of the exposed plant shall safely fuse at currents less than the ampacity of the protector, the associated insulated conductors,and the protector grounding conductor. (4) Where insulated conductors in accordance with Section 800- 11(c)(1) and (2) are used to extend circuits aerially to a building from an unexposed buried or underground circuit. Effectively grounded means permanently connected to earth through a ground connection of sufficiently low impedance and having sufficient am- pacity to prevent the building up of voltages which may result in undue hazard to connected equipment or to persons. 800-3. Installation of Conductors. Conductors from the protector to the equipment or, where no protector is required, conductors attached to the outside of, or inside the building shall comply with the follow- ing: (a) Separation from Other Conductors. Conductors shall be sepa- rated from conductors of electric light and power circuits as follows: (1) Open Conductors. Conductors shall be separated at least two inches from any light or power conductors or Class 1 signal or control circuits not in a raceway nor in metal sheathed, metal-clad, nonmetallic sheathed or type OF cables unless permanently separated from the con- ductors of the other system by a continuous and firmly fixed nonconduc- tor, additional to the insulation on the wire, such as porcelain tubes or flexible tubing. (2) In Raceways and Boxes. Communication conductors shall not be placed in any raceway, compartment, outlet box, junction box or similar fitting with conductors for light and power circuits or Class 1 signal and control circuits unless the conductors of the different sys- ARTICLE 800—COMMUNICATION CIRCUITS 70-395 tems are separated by a partition; provided that this shall not apply to conductors in outlet boxes, junction boxes or similar fittings or com- partments where such conductors are introduced solely for power sup- ply to communication equipment or for connection to remote-control equipment. (3) In Shafts. Conductors may be run in the same shaft with conductors for light and power provided the conductors of the two systems are separated at least 2 inches, or where the conductors of ei- ther system are encased in noncombustible tubing. Where the lighting or power conductors are run in a raceway, or in metal sheathed or metal-clad or nonmetallic sheathed or Type OF cables, neither the two- inch separation nor the non-combustible tubing is required. (b) Vertical Runs. Conductors bunched together in a vertical run in a shaft shall have a fire-resistant covering capable of preventing the carrying of fire from floor to floor, except where conductors are en- cased in noncombustible tubing or are located in a fireproof shaft hav- ing fire stops at each floor. The conductors referred to in this Section would ordinarily be insulated but the kind of insulation is not specified as reliance is placed on the protec- tive device to stop all dangerous voltages and currents. C. Outside Conductors 800-11. Overhead Conductors. Overhead conductors entering build- ings shall comply with the following: (a) On Poles. Where communication conductors and light or power conductors are supported by the same pole, the following conditions shall be met: (1) Relative Location. The conductors should preferably be lo- cated below the light or power conductors. (2) Attachment to Crossarms. Conductors shall not be attached to a crossarm which carries light or power conductors. (3) Climbing Space. The climbing space through signal con- ductors shall comply with the requirements of Section 730-14. (b) On Roofs. Conductors passing over buildings shall be kept at least 8 feet above any roof which may be readily walked upon, except small auxiliary buildings such as garages and the like. (c) Circuits Requiring Protectors. Circuits which require protectors (see Section 800-2) shall comply with the following: (1) Insulation, Single or Paired Conductors. Each conductor, from the last outdoor support to the protector, shall have 1/32-inch rubber insulation, except that when such conductors are entirely within a block the insulation on the conductor may be less than 1/32 inch, but not less than 1/40 inch in thickness. In addition, the conductor, either individually or over the pair, shall be covered with a substantial fibrous covering or equivalent protection. Conductors approved for the pur- pose having rubber insulation of a thickness less than specified above, or having other kinds of insulation may be used. 70-396 NATIONAL ELECTRICAL CODE (2) Insulation, Cables. Conductors within a cable of the metal- sheathed type,or within a cable having a rubber sheath of at least 1/32- inch thickness and covered with a substantial fibrous covering, may have paper or other suitable insulation. Where the metal or rubber sheath is omitted, each conductor shall be insulated as required in Sec- tion 800-11(c-1), and the bunched conductors shall be covered with a substantial fibrous covering or equivalent covering. (3) On Buildings. Open conductors shall be separated at least 4 inches from light or power conductors not in conduit or cable, unless permanently separated from conductors of the other system by a con- tinuous and firmly fixed nonconductor additional to the insulation on the wires, such as porcelain tubes or flexible tubing. Open conduc- tors exposed to accidental contact with light and power conductors operating at over 300 volts, and attached to buildings, shall be sepa- rated from woodwork by being supported on glass, porcelain or other insulating material approved for the purpose except that such separa- tion is not required where fuses are omitted as provided for in Section 800-2(d) or where conductors approved for the purpose are used to extend circuits to a building from a cable having a grounded metal sheath. (4) Entering Buildings. Where a protector is installed inside the building, the conductors shall enter the building either through a non- combustible, nonabsorptive insulating bushing, or through a metal race- way. The insulating bushing may be omitted where the entering con- ductors (1) are in metal-sheathed cable, (2) pass through masonry, (3) are approved for the purpose and fuses are omitted as provided for in Section 800-2(d), or (4) are approved for the purpose and are used to extend circuits to a building from a cable having a grounded metal sheath. Raceways or bushings shall slope upward from the outside or, where this cannot be done,drip loops shall be formed in the conductors immediately before they enter the building. Raceways shall be equipped with an approved service head. More than one conductor may enter through a single raceway or bushing. Conduits or other metallic race- ways located ahead of the protector shall be grounded. 800-12. Lightning Conductors. Where practicable, a separation of at least six feet shall be maintained between open conductors of com- munication systems on buildings and lightning conductors. D. Underground Circuits 800-21. Underground Circuits. Underground conductors of communi- cation circuits entering buildings shall comply with the following: (a) With Electric Light or Power Conductors. Underground conduc- tom in a duct, handhole, or manhole containing electric light or power conductors, shall be in a section separated from such conductors by means of brick,concrete,or tile partitions. (b) Underground Block Distribution. Where the entire street circuit is run underground and the circuit within the block is so placed as to be free from liability of accidental contact with electric light or power cir- cuits of over 300 volts, the insulation requirements of Section 800-11 (c)(1) and (c)(4) shall not apply, the conductors need not be placed ARTICLE 800—COMMUNICATION CIRCUITS 70-397 on insulating supports and no bushings shall be required where the conductors enter the building. E. Grounding 800-31. Grounding. Equipment shall be grounded as follows: (a) Cable Sheath. The metal sheath of aerial cables entering build- ings which are liable to contact with electric light or power conductors shall be grounded or shall be interrupted close to the entrance to the building by an insulating joint or equivalent device. (b) Protector Ground. The protector ground shall comply with the following: (1) Insulation. The grounding conductor shall have a 1/32-inch rubber insulation and shall be covered by a substantial fibrous cover- ing. Conductors approved for the purpose having less than 1/32-inch rubber insulation or having other kinds of insulation may be used. (2) Size. The grounding conductor shall not be smaller than No. 18 AWG copper or equivalent. (3) Run in Straight Line. The grounding conductor shall be run in as straight a line as practicable to the grounding electrode. (4) Physical Damage. Where necessary, the grounding conductor shall be guarded from physical damage. (5) Electrode. The grounding conductor shall preferably be con- nected to a water pipe electrode. Where a water pipe is not readily available and the grounded conductor of the power service is connected to the water pipe at the building, the protector grounding conductor may be connected to the power service conduit, service equipment en- closures, or grounding conductor of the power service. In the absence of a water pipe, connection may be made to a continuous and extensive underground gas piping system, to an effectively grounded metallic structure, or to a ground rod or pipe driven into permanently damp earth. Steam or hot water pipes, or lightning rod conductors shall not be employed as electrodes for protectors.A driven rod or pipe used for grounding power circuits shall not be used for grounding communica- tion circuits unless the driven rod or pipe is connected to the grounded conductor of a multigrounded neutral power system. The requirements for separate made electrodes for power and lighting system grounds, those for communication systems, and those for a lightning rod in- stallation shall not prohibit the bonding together of all such made electrodes.See Section 250-86. It is recommended that all separate electrodes be bonded together to limit potential differences between them and between their associated wiring sys- tems. (6) Electrode Connection. The grounding conductor shall be at- tached to a pipe electrode by means of a bolted clamp to which the conductor is soldered or otherwise connected in an effective manner. Where a gas pipe electrode is used, connection shall be made between the gas meter and the street main. In every case the connection to the grounding electrode shall be made as close to the earth as practicable. 70-398 NATIONAL ELECTRICAL CODE ARTICLE 810—RADIO AND TELEVISION EQUIPMENT A. General 810-1. Scope. This Article shall apply to radio and television receiv- ing equipment and to amateur radio transmitting and receiving equip- ment, but shall not apply to equipment and antennas used for coupling carrier current to power line conductors. It is recommended that the authority having jurisdiction be freely con- sulted as to the specific methods to be followed in any case of doubt relative to installation of antenna conductors and that the National Electrical Safety Code,Part 5,be followed. 810-2. Application of Other Articles. Wiring from the source of power to and between devices connected to the interior wiring system shall comply with Chapters 1 to 4, inclusive, except as modified by Sections 640-3, 640-4 and 640-5. Wiring for radio-frequency and audio-fre- quency equipment and loud speakers shall comply with Article 640. 810-3. Community Television Antenna. The antenna shall comply with the requirements of this Article. The distribution system shall comply with Article 820. 810-4. Radio Noise Suppressors. Radio interference eliminators, in- terference capacitors or radio noise suppressors connected to power supply leads shall be of a type approved for the purpose. They shall not be exposed to physical damage. B. Receiving Equipment Only Antenna Systems—General 810-11. Material. Antennas and lead-in conductors shall be of hard- drawn copper, bronze, aluminum alloy, copper-clad steel or other high- strength, corrosion-resistant material. Soft-drawn or medium-drawn copper may be used for lead-in conductors where the maximum span between points of support is less than 35 feet. 810-12. Supports. Outdoor antennas and lead-in conductors shall be securely supported. The antennas shall not be attached to the electrical service mast. They shall not be attached to poles or similar structures carrying electric light or power wires or trolley wires of more than 250 volts between conductors. Insulators supporting the antenna conductors shall have sufficient mechanical strength to safely support the conduc- tors.Lead-in conductors shall be securely attached to the antennas. 810-13. Avoidance of Contacts with Conductors of Other Systems. Outdoor antennas and lead-in conductors from an antenna to a build- ing shall not cross over electric light or power circuits and shall be kept well away from all such circuits so as to avoid the possibility of ac- cidental contact. Where proximity to electric light and power service conductors of less than 250 volts between conductors cannot be avoided, the installation shall be such as to provide a clearance of at ARTICLE 810—RADIO AND TV EQUIPMENT 70-399 least two feet. It is recommended that antenna conductors be so in- stalled as not to cross under electric light or power conductors. 810-14. Splices. Splices and joints in antenna spans shall be made with approved splicing devices or by such other means as will not ap- preciably weaken the conductors. Soldering may ordinarily be expected to weaken the conductor. Therefore, the joint should be mechanically secure before soldering. 810-15. Grounding. Masts and metal structures supporting antennas shall be permanently and effectively grounded, without intervening splice or connection. Antenna Systems—Receiving Station 810-16. Size of Wire-Strung Antenna. (a) Outdoor antenna conductors for receiving stations shall be of a size not less than given in Table 810-16(a). (b) Self-Supporting Antennas. Outdoor antennas, such as vertical rods or dipole structures, shall be of noncorrodible materials and of strength suitable to withstand ice and wind loading conditions, and shall be located well away from overhead conductors of electric light and power circuits of over 150 volts to ground so as to avoid the possi- bility of the antenna or structure falling into or making accidental con- tact with such circuits. 810-17. Size of Lead-In. Lead-in conductors from outside antennas for receiving stations, shall, for various maximum open span lengths, be of such size as to have a tensile strength at least as great as that of the con- ductors for antenna as specified in Section 810-16. Where the lead-in consists of two or more conductors which are twisted together or are enclosed in the same covering or are concentric, the conductor size shall, for various maximum open span lengths, be such that the tensile strength of the combination will be at least as great as that of the con- ductors for antennas as specified in Section 810-16. Table 810-16(a) Size of Receiving-Station Outdoor Antenna Conductors Minimum Size of Conductors When Maximum Open Span Length is Material Less than 35 feet to Over 35 feet 150 feet 150 feet Aluminum alloy,hard- drawn copper 19 14 12 Copper-clad steel,bronze or other high strength material 20 17 14 For very long span lengths larger conductors will be required, depending on the length of the span and the ice and wind loading. 70-400 NATIONAL ELECTRICAL CODE 810-18. Clearances. (a) On Buildings Outside. Lead-in conductors attached to buildings shall be so installed that they cannot swing closer than two feet to the conductors of circuits of 250 volts or less between conductors, or ten feet to the conductors of circuits of more than 250 volts between con- ductors, except that in the case of circuits not exceeding 150 volts be- tween conductors, where all conductors involved are supported so as to insure permanent separation, the clearance may be reduced but shall not be less than four inches. The clearance between lead-in conductors and any conductor forming a part of a lightning rod system shall be not less than six feet unless the bonding referred to in Section 250-86 is accomplished. (b) Antennas and Lead-Ins — Indoors. Indoor antennas and in- door lead-ins shall not be run nearer than two inches to conductors of other wiring systems in the premises unless (1) such other conductors are in metal raceways or cable armor,or (2) unless permanently separated from such other conductors by a continuous and firmly fixed nonconductor such as porcelain tubes or flexible tubing. 810-19. Electric Supply Circuits Used in Lieu of Antenna. Where an electric supply circuit is used in lieu of an antenna,the device by which the radio receiving set is connected to the supply circuit shall be spe- cially approved for the purpose. Antenna Discharge Units 810-20. Antenna Discharge Units—Receiving Stations. Each conduc- tor of a lead-in from an outdoor antenna shall be provided with an antenna discharge unit approved for the purpose, except that where the lead-in conductors are enclosed in a continuous metallic shield the antenna discharge unit may be installed to protect the shield or may be omitted where the shield is permanently and effectively grounded. Antenna discharge units shall be located outside the building, or inside the building between the point of entrance of the lead-in and the radio set or transformers,and as near as practicable to the entrance of the con- ductors to the building. The antenna discharge unit shall not be located near combustible material nor in a hazardous location as defined in Arti- cle 500. Grounding Conductors—General 810-21. Material. The grounding conductor shall, unless otherwise specified, be of copper, aluminum, copper-clad steel, bronze, or other corrosion-resistant material. 810-22. Insulation. The grounding conductors may be uninsulated. 810-23. Supports. The grounding conductors shall be securely fas- tened in place and may be directly attached to the surface wired over without the use of insulating supports.Where proper support cannot be provided the size of the grounding conductor shall be increased propor- tionately. ARTICLE 810—RADIO AND TV EQUIPMENT 70-401 810-24. Mechanical Protection. The grounding conductor shall be protected where exposed to physical damage or the size of the ground- ing conductor shall be increased proportionately to compensate for the lack of protection. 810-25. Run in Straight Line. The grounding conductor shall be run in as straight a line as practicable from the antenna mast and/or the an- tenna discharge unit to the grounding electrode. 810-26. Grounding Electrode. The grounding conductor shall be con- nected to a metallic underground water piping system as specified in Section 250-81. Where the building is not supplied with a water system the connection shall be made to the metal frame of the building when effectively grounded or to a grounding electrode as specified in Section 250-83. At a penthouse or similar location the ground conductor may be connected to a water pipe or rigid conduit. Grounding Conductors—Receiving Stations 810-27. Inside or Outside Building. The grounding conductor may be run either inside or outside the building. 810-28. Size. The grounding conductor shall be not smaller than No. 10 copper or No. 8 aluminum or No. 17 copper-clad steel or bronze. 810-29. Common Ground. A single grounding conductor may be used for both protective and operating purposes. Where a single conductor is so used, the ground terminal of the equip- ment should be connected to the ground terminal of the protective device. C. Amateur Transmitting and Receiving Stations Antenna System 810-51. Other Sections. In addition to conforming to the requirements of Part C, antenna systems for amateur transmitting and receiving sta- tions shall also comply with Sections 810-11 to 810-15 inclusive. 810-52. Size of Antenna. Antenna conductors for amateur transmit- ting and receiving stations shall be of a size not less than given in Table 810-52. Table 810-52 Size of Amateur-Station Outdoor Antenna Conductors Minimum Size of Conductors When Maximum Open Span Length Is Material Less than Over 150 feet 150 feet Hard-drawn copper 14 10 Copper-clad steel,bronze or other high strength material 14 12 For very long span length larger conductors will be required, depending on the span length and the ice and wind loadings. 70-402 NATIONAL ELECTRICAL CODE 810-53. Size of Lead-In Conductors. Lead-in conductors for transmit- ting stations shall, for various maximum span lengths, be of a size at least as great as that of conductors for antennas as specified in Section 810-52. 810-54. Clearance on Building. Antenna conductors for transmitting stations, attached to buildings, shall be firmly mounted at least 3 inches clear of the surface of the building on nonabsorptive insulating sup- ports, such as treated pins or brackets, equipped with insulators hav- ing not less than 3-inch creepage and airgap distances. Lead-in con- ductors attached to buildings shall also conform to these requirements, except when they are enclosed in a continuous metallic shield which is permanently and effectively grounded. In this latter case the metallic shield may also be used as a conductor. 810-55. Entrance to Building. Except where protected with a continu- ous metallic shield which is permanently and effectively grounded, lead-in conductors for transmitting stations shall enter buildings by one of the following methods: (a) Through a rigid, noncombustible, nonabsorptive insulating tube or bushing. (b) Through an opening provided for the purpose in which the en- trance conductors are firmly secured so as to provide a clearance of at least 2 inches. (c) Through a drilled window pane. 810-56. Protection Against Accidental Contact. Lead-in conductors to radio transmitters shall be so located or installed as to make accidental contact with them difficult. 810-57. Antenna Discharge Units—Transmitting Stations. Each con- ductor of a lead-in for outdoor antenna shall be provided with an an- tenna discharge unit or other suitable means which will drain static charges from the antenna system. Exception No. 1. Where protected by a continuous metallic shield which is permanently and effectively grounded. Exception No. 2. Where the antenna is permanently and effectively grounded. Grounding Conductors—General 810-58. Other Sections. All grounding conductors for amateur trans- mitting and receiving stations shall comply with Sections 810-21 to 810- 27 inclusive. 810-59. Size of Protective Ground. The protective ground conductor for transmitting stations shall be as large as the lead-in, but not smaller than No. 10 copper,bronze,or copper-clad steel. 810-60. Size of Operating Grounding Conductor. The operating grounding conductor for transmitting stations shall be not less than No. 14 copper or its equivalent. Interior Installation—Transmitting Stations 810-70. Clearance From Other Conductors. Except as provided in Article 640, all conductors inside the building shall be separated at ARTICLE 820—COMMUNITY ANTENNA SYSTEMS 70-403 least 4 inches from the conductors of any other light or signal circuit unless separated therefrom by conduit or some firmly fixed nonconduc- tor such as porcelain tubes or flexible tubing. 810-71. General. Transmitters shall comply with the following: (a) Enclosing. The transmitter shall be enclosed in a metal frame or grille, or separated from the operating space by a barrier or other equivalent means, all metallic parts of which are effectually connected to ground. (b) Grounding of Controls. All external metallic handles and con- trols accessible to the operating personnel shall be effectually grounded. No circuit in excess of 150 volts between conductors should have any parts exposed to direct contact. A complete dead-front type of switchboard is preferred. (c) Interlocks on Doors. All access doors shall be provided with in- terlocks which will disconnect all voltages in excess of 350 volts be- tween conductors when any access door is opened. (d) Audio-Amplifiers. Audio-amplifiers which are located outside the transmitter housing shall be suitably housed and shall be so located as to be readily accessible and adequately ventilated. ARTICLE 820—COMMUNITY ANTENNA TELEVISION AND RADIO DISTRIBUTION SYSTEMS A. General 820-1. Scope. The provisions of this Article shall apply to coaxial cable distribution of radio frequency signals typically employed in Com- munity Antenna Television (CATV) systems. Where the wiring sys- tem employed is other than coaxial, the provisions of Article 800— Communication Circuits shall apply. The coaxial cable may be used to deliver low energy power to equip- ment directly associated with this radio frequency distribution system provided the voltage is not in excess of 60 volts and where the current supply is from a transformer or other device having energy limiting characteristics. 820-2. Material. Coaxial cable used for the radio frequency distribu- tion system shall be suitable for the application. B. Protection 820-3. Ground of Outer Conductive Shield of a Coaxial Cable. Where coaxial cable is exposed to lightning or to accidental contact with lightning arrester conductors or power conductors operating at a potential exceed- ing 300 volts, the outer conductive shield of the coaxial cable shall be grounded at the building premises as close to the point of cable entry as practicable. 70-404 NATIONAL ELECTRICAL CODE (a) Protective Devices for Coaxial Cable. Where the outer conduc- tive shield of a coaxial cable is grounded,no other protective devices are required. (b) Block Distribution. When coaxial cable is so located within a block containing the building or buildings to be served that it is not liable to accidental contact with light or power conductors operating at a poten- tial exceeding 300 volts, the grounding point may be located as close to the point of block entry as practicable. C. Installation of Cable Coaxial cable installation for radio frequency distribution shall com- ply with the following: 820-4. Outside Conductors. Prior to the point of grounding, as defined in Section 820-3. (a) On Poles. On poles,the conductors should preferably be located below the light and power conductors and shall not be attached to a cross arm which carries light or power conductors. (b) Lead-in Clearance. Lead-in or aerial drop cables from a pole or other support including the point of initial attachment to a building or structure shall be kept away from electric light or power circuits so as to avoid the possibility of accidental contact. Where proximity to elec- tric light and power service conductors cannot be avoided, the installa- tion shall be such as to provide clearances of not less than 12 inches from light and power service drops. (c) Over Roofs. Cables passing over buildings shall be at least 8 feet above any roof which is accessible for pedestrian traffic. (d) Between Buildings. Cables extending between buildings,and also the supports or attachment fixtures shall be acceptable for the purpose, and shall have sufficient strength to withstand the loads to which they may be subjected, except that where cable does not have sufficient strength to be self-supporting, it shall be attached to a supporting mes- senger cable which together with the attachment fixtures or supports shall be acceptable for the purpose and shall have sufficient strength to withstand the loads to which they may be subjected. (e) On Buildings. When attached to buildings, cables shall be se- curely fastened in such a manner that they shall be separated from other conductors as follows: (1) Light and Power. The coaxial cable shall have a separation of at least 4 inches from light or power conductors not in conduit or cable, unless permanently separated from conductors of the other system by a continuous and firmly fixed non-conductor additional to the insulation on the wires. (2) Other Communication Systems. Coaxial cable shall be installed so that there will be no unnecessary interference in the maintenance of the separate systems. In no case shall the conductors, cables, messenger strand or equipment of one system cause abrasion to the conductors, cable,messenger strand or equipment of any other system. ARTICLE 820—COMMUNITY ANTENNA SYSTEMS 70-405 (3) Lightning Conductors. Where practicable, a separation of at least 6 feet shall be maintained between any coaxial cable and lightning conductors. 820-5. Entering Buildings. Coaxial cable shall slope upward from the outside where entering a building, or, where this is impracticable, drip loops shall be formed in the cable at the point of entrance. 820-6. Conductors Inside Buildings. Beyond the point of grounding, as defined in Section 820-3, cable installation shall comply with the follow- ing: (a) Light and Power. Coaxial cable shall be separated at least two inches from any light or power conductors or Class 1 signal or control circuits not in a raceway nor in metal sheathed, metal-clad, nonmetallic sheathed or type UF cables unless permanently separated from the con- ductors of the other system by a continuous and firmly fixed nonconduc- tor, additional to the insulation on the wire, such as porcelain tubes or flexible tubing. (b) In Raceways and Boxes. Coaxial cable shall not be placed in any raceway, compartment, outlet box, junction box or other enclosures with conductors for light and power circuits or Class 1 signal and con- trol circuits unless the conductors of the different systems are separated by a permanent partition; provided that this shall not apply to con- ductors in outlet boxes, junction boxes or similar fittings or compart- ments where such conductors are introduced solely for power supply to the coaxial cable system distribution equipment or for power connec- tion to remote control equipment. (c) In Shafts. Coaxial cable may be installed in the same shaft with conductors for light and power provided the conductors of the two sys- tems are separated at least two inches or where the conductors of either system are encased in non-combustible tubing. Where the lighting or power conductors are run in a raceway, or in metal sheathed or metal-clad or nonmetallic sheathed or Type UF cables, neither the two-inch separation nor the non-combustible tubing is required. (d) Vertical Runs. Conductors or coaxial cables bunched together in a vertical run in a shaft shall have a fire resistant covering capable of preventing the carrying of flame from floor to floor except where con- ductors are encased in non-combustible tubing or are located in a fire- proof shaft having fire stops at each floor. (e) Other Conductors. There is no specific separation requirement between Class 2 Signal and Control circuits wired distribution system cables and communication cables or conductors other than the clearance necessary to prevent conflict or abrasion. D. Underground Circuits 820-7. Underground Coaxial Cable. Underground coaxial cable enter- ing buildings shall comply with the following: (a) With Light and Power Conductors. Underground conductors in a duct, pedestal, handhole, or manhole containing electric light or power 70-406 NATIONAL ELECTRICAL CODE conductors shall be in a section permanently separated from such con- ductors by means of a suitable barrier. E. Grounding 820-8. Cable Grounding. Coaxial cable shall be grounded as follows: (a) Ground Circuit. The coaxial cable ground shall comply with the following: (1) Insulation. The grounding conductor shall have a rubber or other suitable kind of insulation. (2) Material. The ground conductor shall be copper or other cor- rosion-resisting conductive material,stranded or solid. (3) Size. The grounding conductor shall not be smaller than No. 18 AWG;it shall have a conductivity approximately equal to that of the outer conductor of the coaxial cable. (4) Run. The grounding conductor shall be run in as straight a line as practicable to the grounding electrode. (5) Physical Protection. Where necessary, the grounding conduc- tor shall be guarded from physical damage. (6) Electrode. The grounding conductor shall preferably be con- nected to a water pipe electrode. Where a water pipe is not readily avail- able and the grounded conductor of the power service is connected to the water pipe at the building, the grounding conductor may be con- nected to the power service conduit, service equipment enclosures, or grounding conductor of the power service. In the absence of a water pipe, connection may be made to a continuous and extensive under- ground gas piping system where permitted, to an effectively grounded metallic structure, or to a ground rod or pipe driven into permanently damp earth. Steam or hot water pipes, or lightning rod conductors shall not be employed as grounding electrodes. A driven rod or pipe used for grounding power circuits shall not be used for grounding unless the driven rod or pipe is connected to the grounded conductor of a multi- grounded neutral power system. The requirements for separate made electrodes for power and lighting system grounds, those for communica- tion systems, and those for a lightning rod installation shall not prohibit the bonding together of all such made electrodes. (7) Electrode Connection. It is recommended that the grounding conductor shall be attached to a pipe electrode by means of a bolted clamp to which the conductor is soldered or otherwise connected in an effective manner.Where a gas pipe electrode is used,connection shall be made between the gas meter and the street main. In every case the con- nection to the grounding electrode shall be made as close to the earth as practicable. 820-9. Equipment Grounding. Unpowered equipment and enclosures or equipment powered by the coaxial cable are deemed to be grounded when connected to the metallic cable shield. F. General 820-10. Prevention of Spread of Fire. Installations shall be so made that the possible spread of fire through fire walls, fire partitions or fire- resistive floors is reduced to a minimum. 70-407 Chapter 9—Tables and Examples A. Tables Where conduit nipples having a maximum length not to exceed six inches are installed between boxes, cabinets, gutters, switch cases and similar enclosures, the conductor fill in such nipples may be increased to not more than 60 per cent of the internal cross-sectional area of the conduit, and note 8 of Tables 310-12 through 310-15 does not apply to this condition. Tables 1, 2 and 3 apply only to complete conduit systems, and do not apply to short sections of conduit used for the protection of exposed wiring from physical damage. 70-408 NATIONAL ELECTRICAL CODE ,0 u .. 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U 0 ° n CHAPTER 9—TABLES 70-411 M ..N,o0et 0340 N mOOO.00,Dvi C et 4 sO vl of M N N N VD'a, 00 vt P M O 00,D et..O T T 00 r 1D h et et et et m N N N ▪ m V nN g Nr.�M m(�[��bhet mm m v,U H ,C MN N N727 N.,Tr r- bh,v,et m m N g NAN 4.f....- Tr ""et MMNN \'C of 4 Qi NN O.b m..O O�r�D vt u'i h V e!Mm NN et N0o viM OO.00 r vi7 MmN .-..... m N et Nr O.00 N 1D vt et M M M M N m..m .. u m— L M C m O oo r-D V et M M N .... .. N.C. ...... .-y N cc pa r•D:::::.........r......... N „" 0• a M N N...... .. C. ^.Y • W •7 M m N ti............ O � H (� N M .. H,j. U ~ W ..S N ..U ..�� eli g c W u° S 0, fa h3Nd U 000 uo y 0N V0008O8OOC88OOO8 NmmMetC NI-MCA * O 1 70-412 NATIONAL ELECTRICAL CODE Table 2. Trade Sizes of Conduit or Tubing for Number of Conductors Lead-Covered Types RI.and RHL-600 V. (See Sections 346-6 and 348-6) Size Number of Number of Number of AWG Single Conductor 2-Conductor 3-Conductor MCM Cables Cables Cables 1 2 3 4 1 2 3 4 1 2 3 4 14 1/2 3/4 3/4 1 3/4 1 1 11 3/4 11/4 11/2 11/2 12 1/2 3/4 3/4 1 3/4 1 11/4 13 1 11/4 11/2 2 10 1/2 3/4 1 1 3/4 11/4 11/4 11/2 1 11/2 2 2 8 l 1 11/4 11/2 1 11/4 11/2 2 1 2 2 21/2 6 3/4 11/4 11/2 11/2 11/4 11/2 2 21 11/4 21/2 3 3 4 3/4 11/4 11 11/2 11/4 2 21 21/2 11 3 3 31/2 3 3/4 11/4 11/2 2 11/4 2 21/2 3 11/2 3 3 31 2 1 11/4 11 2 11/4 2 21 3 11 3 31/2 4 1 1 11/2 2 2 11/2 21 3 31 2 31/2 4 41/2 0 1 2 2 21/2 2 21/2 3 31 2 4 41/2 5 00 1 2 2 21/2 2 3 31/2 4 21/2 4 41/2 5 000 11/4 2 21/2 21/2 2 3 31/2 4 21 41/2 41/2 6 0000 11/4 21/2 21/2 3 21/2 3 31/2 41 3 5 6 6 250 11/4 21 3 3 ... ... . .. ... 3 6 6 ... 300 11/2 3 3 31/2 31/2 6 6 ... 350 11/2 3 3 31/2 31/2 6 6 ... 400 11 3 3 31/2 31/2 6 6 ... 500 11/2 3 31/2 4 ... ... ... ... 4 6 ... 600 2 31/2 4 41/2 . .. ... 700 2 4 4 5 750 2 4 4 5 800 2 4 41 5 900 21/2 4 41/2 5 ... ... ... ... ... 1000 21/2 41/2 41/2 6 ... ... ... ... ... 1250 3 5 5 6 1500 3 5 6 6 1750 3 6 6 2000 31/z 6 6 The above sizes apply to straight runs or with nominal offsets equivalent to not more than two quarter-bends. See Section 346-10 for bends in conduit. CHAPTER 9—TABLES 70-413 Table 3.Combination of Conductors (See Sections 346-6,346-11 and 348-6) For groups or combinations of conductors not included in Table 1, Chapter 9, for new work, or Table IA, Chapter 9, for rewiring,the conduit or tubing shall be of such size that the sum of the cross-sectional areas of the individual conductors will not be more than the percentage of the interior cross-sec- tional area of the conduit or tubing shown in the following table: Percent Area of Conduit or Tubing Number of Conductors 1 2 3 4 Over 4 1. Conductors—New Work 35 25* 25* 25* 25* Types FEP,FEPB,T,TW TF,THW,RUH,RUW,XHHW, THWN,THHN,TFN,PF,PGF 2. Conductors—New Work 53 31 40 40 40 Types RF-2,RFH-2,RH, RHH,RHW 3. Conductors(All Types) 53 31 40 40 40 Rewiring 4. Conductors—Lead Covered 55 30 40 38 35 For ampacity of more than three conductors in a conduit or tubing, see Tables 310-12 through 310-15,Note 8. See Tables 4 through 8, Chapter 9, for dimensions of conductors, conduit and tubing,and raceway. When, in new work, conductors limited to 25 per cent fill are to be in the same conduit or tubing as conductors limited to 40 per cent fill, the com- bined fill shall not be greater than 40 per cent nor shall any conductor size or type, when used with conductors of other size or type, occupy more than its allowable fill when used alone. *The percentage fill for these conductors may be increased to those given in line 2 where the total conductor fill is based on the dimensions for Type RHW conductors as given in Column 3 of Table 5. 1 70-414 NATIONAL ELECTRICAL CODE ^"ov1� °°��a ��8� >0ee01 ...•Nen vvic:O Ti s c O ..OM roo 00 NON toc'o Ue�n .!Nenvll^ NaOoo!` ooO T 7 .i.•Nr af.ONO Ow C C V. Op= = k N.7ON 7e v1,0 T000'0 _ ..Nen0oc O:TO Oen000C 0.0 o'• N n �..Nrvi 000. O •O$4-4,"e... o O O 4.4 � s N O Np T.D.NaD 7.. 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Nm�M7 4vmi '1 O = Q yI YI C a W '0 — ,- EQ -'--* k h 00 O\ h •�p N N ,.00 N O.0N'0 M[N r 00 O * O�.„„ 00 0 m •0 r- •Vl N -•0 N m'O N N 'O 00 OD C p •N •N N m}0 o0 O N .- O m N N r c .�,"r Q¢Q, 0 00 O• 00 00000 O -.• •N N• •N M M d a- FF3a � • v a � b Cr. ON� M 00 VrO F.F a,�UoOm •tea � NN N m m O O 'n'On 1 OM, �A,° U rj K • N*0 coN •00 a •0 •O • co 00 N N, N 0O-.co}N 0 t0 0 co so O. M N •N 00 •'O •'D • coQ. .'O 0 tN 00 V 0,-4 N co •N en •C •N N�O 0o 0 N —'n-.00 ai*0., n.' U O O O O •O O .O .0 --N N M f N xy vx x N O •CO 00 N •a d�R oEu N •�cv . ^.ry :0 :,.0 F 6.R V O 00 On.h 0o M.0 N 00 00 N, 00 ¢A U n Ve vv,v•v• o• o•c ,�•� N enN en-. 0 CD __ '0'0 NN N000000 '0'MN -•, 00p08p -Q- U oo 0 0 0 0 70-416 NATIONAL ELECTRICAL CODE K4AF .. '0 0.,r.•rn enr b T 00 NN N0O Nrr ..• b O m'0 00 0'N o.'0 oar r O. O'0 rn O. N U 00'0 00 e0 0.r N 0.Q0 O ev,v v N a CD.o.•.Cl. rO en'O x Q 0 U .•+N N N x x q 0 y O� ,0... o.en en in 000 00 OOo y QF• r N'0 ut r 00 00 r enO N'0 .G N N a0 00 0' O'-'..•N N N N SO N 00 Q U m v VI ad " c Q 0 U W �a l aW 0 wa cow o•cl 0D o QA U d 3 - N d co • ry z3 o' "• 0 No 0 N a E 00 G FF 00 U v v v v t m Q oz FF arc . •Ncoma 00 QA G u G ; 'e"a 0 ed F• �^ N 00 0,b- '0 N vNi O 0 ONo en 7 O en cC O L�'• 00 v'�N 0,en N 0 N eT N 00 ut r a 0 * 00QP p O vt b s000 O ..N N 00 N0N NN Zy b F[- s.o , w3 o ; . 0 .NT en7TNut 7rN�N f"F 0d O.*0. N ON 00 OroN FO N d.�U —O DO 0. T O •-'N N N N -0-..-!r 00 Q: ,y F^ OA 4 U .. .• -.. .-. ••... 00 .3 aQ � 3 � Ir�1 "rt C1 % en N r O en a O N N 0 .•N h 0' ..-- — x z p 0tC e1NNcn 7 00 N —. en�0 rG.r �-e. coo �i CI *N y.. • a a0 N en 0' T en O r O 0o O W x O v ��00 n�7 �N ooN 0. N b a*w0 0Qg U .•.N N N en •co � x* Q a qx Cr >. x f aax x ° NF o 4 G 0 N• 00 en ut N 0, en eT N rt V..0.•,.0.• C 0 `e'" w m F" A o ,D en en m.-. enao enr en o,r G.•N 0 Z O 00 00 C as:. U 00 a rn o.— N en en.n v, a�00 a o• .m v, , p I; d G O O 00 m0 ppp p pp 4 z •- A .y. .a Q'r U N O 5 S O 8 O N S 8 8 N 8 O O * * .- : Z F CHAPTER 9-TABLES 70-417 Table 6. Dimensions of Lead-Covered Conductors Types RL,RHL,and RUL Single Two Three Size Conductor Conductor Conductor AWG-MCM Diam. Area Diam. Area Diam. Area Inches Sq.Ins. Inches Sq.Ins. Inches Sq.Ins. 14 .28 .062 .28 x .47 .115 .59 .273 12 .29 .066 .31 x .54 .146 .62 .301 10 .35 .096 .35 x .59 .180 .68 .363 8 .41 .132 .41 x .71 .255 .82 .528 6 .49 .188 .49 x .86 .369 .97 .738 4 .55 .237 .54 x .96 .457 1.08 .916 2 .60 .283 .61 x 1.08 .578 1.21 1.146 1 .67 .352 .70 x 1.23 .756 1.38 1.49 0 .71 .396 .74 x 1.32 .859 1.47 1.70 00 .76 .454 .79 x 1.41 .980 1.57 1.94 000 .81 .515 .84 x 1.52 1.123 1.69 2.24 0000 .87 .593 .90 x 1.64 1.302 1.85 2.68 250 .98 .754 2.02 3.20 300 1.04 .85 2.15 3.62 350 1.10 .95 2.26 4.02 400 1.14 1.02 2.40 4.52 500 1.23 1.18 2.59 5.28 Note-No. 14 to No. 8,solid conductors: No. 6 and larger,stranded con- ductors.Data for 2/64-inch insulation not yet compiled. 70-418 NATIONAL ELECTRICAL CODE Table 7. Dimensions of Asbestos-Varnished-Cambric Insulated Conductors Types AVA,AVB,and AVL Type AVA Type AVB Type AVL Size Approx. Approx. Approx. Approx. Approx. Approx. AWG Diam. Area Diam. A.ea Diam. Area MCM Inches Sq.Ins. Inches Sq.Ins. Inches Sq.Ins. 14 .245 .047 .205 .033 .320 .080 12 .265 .055 .225 .040 .340 .091 10 .285 .064 .245 .047 .360 .102 8 .310 .075 .270 .057 .390 .119 6 .395 .122 .345 .094 .430 .145 4 .445 .155 .395 .123 .480 .181 2 .505 .200 .460 .166 .570 .255 1 .585 .268 .540 .229 .620 .300 0 .625 .307 .580 .264 .660 .341 i 00 .670 .353 .625 .307 .705 .390 000 .720 .406 .675 .358 .755 .447 , 0000 .780 .478 .735 .425 .815 .521 250 .885 .616 .855 .572 .955 .715 300 .940 .692 .910 .649 1.010 .800 350 .995 .778 .965 .731 1.060 .885 400 1.040 .850 1.010 .800 1.105 .960 500 1.125 .995 1.095 .945 1.190 1.118 550 1.165 1.065 1.135 1.01 1.265 1.26 600 1.205 1.140 1.175 1.09 1.305 1.34 650 1.240 1.21 1.210 1.15 1.340 1.41 • 700 1.275 1.28 1.245 1.22 1.375 1.49 750 1.310 1.35 1.280 1.29 1.410 1.57 800 1.345 1.42 1.315 1.36 1.440 1.63 850 1.375 1.49 1.345 1.43 1.470 1.70 900 1.405 1.55 1.375 1.49 1.505 1.78 950 1.435 1.62 1.405 1.55 1.535 1.85 1000 1.465 1.69 1.435 1.62 1.565 1.93 Note: No. 14 to No. 8, solid, No. 6 and larger, stranded; except AVL where all sizes are stranded. Varnished-Cambric Insulated Conductors Type V The insulation thickness for varnished-cambric conductors, Type V, is the same as for rubber-covered conductors, Type RH, except for Nos. 14 and 12 which have 3/64-inch insulation for varnished-cambric and 2/64-inch insulation for rubber-covered conductors and for No. 8 which has 3/64-inch insulation for varnished-cambric, and 4/64-inch insulation for rubber- covered conductors. See Table 310-2(b). Tables 1 and 2 may, therefore, be used for the number of varnished-cambric insulated conductors in a conduit or tubing. CHAPTER 9-TABLES 70-419 Table 8.Properties of Conductors D.C.Resistance Concentric Lay Ohms/M Ft. Stranded Bare At 25°C.77°F. Conductors Conductors Alumni- Diam. Copper num Size Area Each *Area AWG Cir. No. Wire Diam. Sq. Bare Tin'd. MCM Mils Wires Inches Inches Inches Cond. Cond. 18 1620 Solid .0403 .0403 .0013 6.51 6.79 10.7 16 2580 Solid .0508 .0508 .0020 4.10 4.26 6.72 14 4110 Solid .0641 .0641 .0032 2.57 2.68 4.22 12 6530 Solid .0808 .0808 .0051 1.62 1.68 2.66 10 10380 Solid .1019 .1019 .0081 1.018 1.06 1.67 8 16510 Solid .1285 .1285 .0130 .6404 .659 1.05 6 26240 7 .0612 .184 .027 .410 .427 .674 4 41740 7 .0772 .232 .042 .259 .269 .424 3 52620 7 .0867 .260 .053 .205 .213 .336 2 66360 7 .0974 .292 .067 .162 .169 .266 1 83690 19 .0664 .332 .087 .129 .134 .211 0 105 600 19 .0745 .372 .109 .102 .106 .168 00 133100 19 .0837 .418 .137 .0811 .0843 .133 000 167 800 19 .0940 .470 .173 .0642 .0668 .105 0000 211600 19 .1055 .528 .219 .0509 .0525 .0836 250 250000 37 .0822 .575 .260 .0431 .0449 .0708 300 300000 37 .0900 .630 .312 .0360 .0374 .0590 350 350000 37 .0973 .681 .364 .0308 .0320 .0505 400 400000 37 .1040 .728 .416 .0270 .0278 .0442 500 500000 37 .1162 .813 .519 .0216 .0222 .0354 600 600000 61 .0992 .893 .626 .0180 .0187 .0295 700 700000 61 .1071 .964 .730 .0154 .0159 .0253 750 750000 61 .1109 .998 .782 .0144 .0148 .0236 800 800000 61 .1145 1.030 .833 .0135 .0139 .0221 900 900000 61 .1215 1.090 .933 .0120 .0123 .0197 1000 1000000 61 .1280 1.150 1.039 .0108 .0111 .0177 1250 1250000 91 .1172 1.289 1.305 .00863 .00888 .0142 1500 1500000 91 .1284 1.410 1.561 .00719 .00740 .0118 1750 1750000 127 .1174 1.526 1.829 .00616 .00634 .0101 2000 2000000 127 .1255 1.630 2.087 .00539 .00555 .00885 *Area given is that of a circle having a diameter equal to the overall dia- meter of a stranded conductor. The values given in the Table are those given in Handbook 100 of the Na- tional Bureau of Standards except that those shown in the 8th column are those given in Specification B33 of the American Society for Testing and Ma- terials, and those shown in the 9th column are those given in Standard No. S-19-81 of the Insulated Power Cable Engineers Association and Standard No.WC3-1964 of the National Electrical Manufacturers Association. The resistance values given in the last three columns are applicable only to direct current. When conductors larger than No. 4/0 are used with al- ternating current the multiplying factors in Table 9, Chapter 9 should be used to compensate for skin effect. 70-420 NATIONAL ELECTRICAL CODE Table 9. Multiplying Factors for Converting DC Resistance to 60 Cycle AC Resistance Multiplying Factor For Nonmetallic Sheathed For Metallic Sheathed Size Cables in Air or Cables or all Cables Nonmetallic Conduit in Metallic Raceways Copper Aluminum Copper Aluminum Up to 3 AWG 1. 1. 1. 1. 2 1. 1. 1.01 1.00 1 1. 1. 1.01 1.00 0 1.001 1.000 1.02 1.00 00 1.001 1.001 1.03 1.00 000 1.002 1.001 1.04 1.01 0000 1.004 1.002 1.05 1.01 250 MCM 1.005 1.002 1.06 1.02 300 MCM 1.006 1.003 1.07 1.02 350 MCM 1.009 1.004 1.08 1.03 400 MCM 1.011 1.005 1.10 1.04 500 MCM 1.018 1.007 1.13 1.06 600 MCM 1.025 1.010 1.16 1.08 700 MCM 1.034 1.013 1.19 1.11 750 MCM 1.039 1.015 1.21 1.12 800 MCM 1.044 1.017 1.22 1.14 1000 MCM 1.067 1.026 1.30 1.19 1250 MCM 1.102 1.040 1.41 1.27 1500 MCM 1.142 1.058 1.53 1.36 1750 MCM 1.185 1.079 1.67 1.46 2000 MCM 1.233 1.100 1.82 1.56 CHAPTER 9—EXAMPLES 70-421 B. Examples Selection of Conductors. In the following examples,the size of conductor has been selected on the basis of the allowable ampacities tabulated in the second column of Table 310-12. If other types of insulated conductors are used, or if the conductors are run open, or with more than three conductors in a raceway, the size of conductor may vary from those shown. Tables 310- 12 through 310-15 and Notes thereto should be consulted in selecting the size of conductor for a particular installation. Voltage. For uniform application of the provisions of Articles 210, 215 and 220 a nominal voltage of 115 and 230 volts shall be used in computing the ampere load on the conductor. Fractions of an Ampere. Except where the computations result in a major fraction of an ampere,such fractions may be dropped. Ranges. For the computation of the range loads in these examples Col- umn A of Table 220-5 has been used. For optional methods, see Columns B and C of Table 220-5. Example No.1. Single Family Dwelling Dwelling has a floor area of 1500 sq. ft. exclusive of unoccupied cellar, unfinished attic,and open porches.It has a 12 kw range. Computed Load (see Section 220-4) General Lighting Load: 1500 sq.ft.at 3 watts per sq.ft. =4500 watts. Minimum Number of Branch Circuits Required (see Section 220-3), General Lighting Load: 4500 _ 115 = 39.1 amperes: or three 15 ampere 2-wire circuits; or two 20 ampere 2-wire circuits Small Appliance Load:Two 2-wire 20 amperes circuits(Section 220-3(b)) Laundry Load:One 2-wire 20 ampere circuit(Section 220-3(b)) Minimum Size Feeders Required (see Section 220-4) Computed Load General Lighting 4500 watts Small Appl. Load 3000 watts Laundry 1500 watts Total (without range) 9000 watts 3000 watts at 100% 3000 watts 9000—3000 = 6000 watts at 35% = 2100 watts Net computed (without range) 5100 watts Range Load (see Table 220-5) 8000 watts Net computed (with range) 13,100 watts For 115/230 volt 3-wire system feeders, 13,100-230 =57 amperes Net computed load exceeds 10 kw. so service conductors shall be 100 amperes (see Section 230-41 Exception No. 1). 70-422 NATIONAL ELECTRICAL CODE Example No.1(a). Single Family Dwelling Same conditions as Example No. 1, plus addition of one 6 ampere 230 volt room air conditioning unit and three 12 ampere 115 volt room air con- ditioning units.See Article 422,Part F. From Example No. 1,feeder current is 57 amperes(3 wire,230 volt) Line A Neutral Line B 57 57 amperes from Example No. 1 6 6 one 230 volt air cond. motor 12 12 two 115 volt air cond. motors 12 one 115 volt air cond. motor 3 3 25% of largest motor (Section 430-24) 78 90 amperes per line Example No. 1(b). Single Family Dwelling Optional Calculation for One-Family Dwelling(Section 220-7) Dwelling has a floor area of 1500 sq. ft. exclusive of unoccupied cellar, unfinished attic and open porches. It has a 12 kw range, a 2.5 kw water heater, a 1.2 kw dishwasher, 9 kw of electric space heating installed in five rooms, a 4.5 kw clothes dryer, and a 6 amp. 230 volt room air conditioning unit. Air conditioner kw is 6 X 230-- 1000 = 1.38 kw 1.38 kw is less than the connected load of 9 kw of space heating; therefore, the air. conditioner load need not be included in the service calculation (see Section 220-4(k)). 1500 sq. ft. at 3 watts 4.5 kw Two 20 amp.appliance outlet circuits at 1500 watts each 3.0 kw Laundry Circuit 1.5 kw Range (at nameplate rating) 12.0 kw Water heater 2.5 kw Dishwasher 1.2 kw Space heating 9.0 kw Clothes dryer 4.5 kw 38.2 kw First 10 kw at 100% = 10.00 kw Remainder at 40% (28.2 kw X .4) = 11.28 kw Calculated load for service size 21.28 kw=21,280 watts 21,280=230=92.5 Therefore,this dwelling may be served by a 100 amperes service. Example No. 1(c). Single Family Dwelling Optional Calculation for One-Family Dwelling(See Section 220-7) Dwelling has a floor area of 1500 sq.ft.exclusive of unoccupied cellar, un- i finished attic and open porches.It has 2 - 20 ampere small appliance circuits, f 1 - 20 ampere laundry circuit, two 4 kw wall-mounted ovens, one 5.1 kw counter-mounted cooking unit, a 4.5 kw water heater, a 1.2 kw dishwasher, a 4.2 kw combination clothes washer and dryer, 6 - 7 ampere 230 volt room air conditioning units and a 1.5 kw permanently installed bathroom space heater. Air conditioning kw calculation Total amperes 6 X 7= 42.00 amperes 25% of largest motor.25 X 7 = 1.75 amperes 43.75 amperes 43.75 X 230 _ 1000= 10. 1 kw of air conditioner load (Example 1(c) Continued Next Page) CHAPTER 9—EXAMPLES 70-423 Example No.1(c)(Continued) Load included at 100% Air conditioning 10.1kw Space heater (omit,see Sect.220-4(k)) Other Load 1500 sq.ft. at 3 watts 4.5 Two 20 amp small appliance circuits • at 1500 watts 3.0 Laundry Circuit 1.5 2 ovens 8. 1 cooking unit 5.1 Water Heater 4.5 Dishwasher 1.2 Washer/Dryer 4.2 Total other load 32.0 1st 10 kw at 100% 10.0 kw Remainder at 40% (22.0 kw X .4) 8.8 kw Total calculated load 28.9 kw = 28,900 watts 28,900_230 = 125.6 amperes(service rating) Example No.2. Small Roadside Fruitstand with No Show Windows A small roadside fruitstand with no show windows has a floor area of 150 square feet. The electrical load consists of general lighting and a 1000 watt flood light.There are no other outlets. Computed Load (Section 220-4) *General Lighting 150 sq.ft.at 3 watts/sq.ft. X 1.25 = 562 watts (3 watts/sq.ft.for stores) 562 watts± 115 = 4.88 amperes One 15 ampere 2-wire branch circuit required (Section 220-3) Minimum Size Service Conductor Required (Section 230-41 Exception No.2) Computed load 562 watts Floodlight load 1000 watts Total load 1562 watts 1562 _ 115 = 13.6 amperes Use No.8 service conductor (Section 230-41 Exception No.2) Use a 30 ampere service switch or breaker (Section 230-71) Example No.3. Store Building A store 50 feet by 60 feet, or 3,000 square feet, has 30 feet of show window. Computed Load (Section 220-4) *General lighting load: 3,000 square feet at 3 watts per square foot X 1.25 11,250 watts **Show window lighting load: 30 feet at 200 watts per foot 6,000 watts Minimum Number of Branch Circuits Required (Section 220-3) ***General lighting load: 11,250 _ 230 = 49 amperes for 3 wire, 115/230 volts; or 98 amperes for 2 wire, 115 volts: (Example 3 Continued Next Page) 70-424 NATIONAL ELECTRICAL CODE Example No.3(Continued) Three 30 ampere,2-wire;and one 15 ampere,2-wire circuits;or Five 20 ampere,2-wire circuits;or Three 20 ampere,-2-wire,and three 15 ampere,2-wire circuits;or Seven 15 ampere,2-wire circuits;or Three 15 ampere,3-wire,and one 15 ampere,2-wire circuits. Special lighting load (show window): (Sections 220-2 Exception No. 2 and 220-4(b)): 6,000 _ 230 = 26 amperes for 3-wire, 115/230 volts; or 52 amperes for 2-wire, 115 volts: Four 15 ampere,2-wire circuits;or Three 20 ampere,2-wire circuits;or Two 15 ampere, 3-wire circuits. Minimum Size Feeders(or Service Conductors) Required (Section 215-2): For 115/230 volt,3-wire system: Ampere load:49 plus 26 = 75 amperes. (Section 220-2): Size of each feeder, No.3 For 115 volt system: Ampere load:98 plus 52 = 150 amperes. (Section 220-2): Size of each feeder, No.3/0 *The above examples assume.that the entire general lighting load is likely to be used for long periods of time and the load is therefore increased by 25 per cent in accordance with Section 220-2. The 25 per cent increase is not applicable to any portion of the load not used for long periods. * If show window load computed as per Section 220-2, the unit load per outlet to be increased 25 per cent. ***The load on each general lighting branch circuit not to exceed 80% of the branch circuit rating(Section 210-23b). Example No.4. Multi-Family Dwelling Multi-family dwelling having a total floor area of 32,000 square feet with 40 apartments. Meters in two banks of 20 each and individual sub-feeders to each apart- ment. One-half of the apartments are equipped with electric ranges of not exceed- ing 12 kw each. Area of each apartment is 800 square feet. Laundry facilities on premises available to all tenants. Add no circuit to individual apartment. Add 1500 watts for each laundry circuit to house load and add to the example as a"house load." Computed Load for Each Apartment(Article 220): General lighting load: 800 square feet at 3 watts per square foot 2,400 watts Special appliance load: Electric range 8,000 watts Minimum Number of Branch Circuits Required for Each Apartment (Section 220-3): General lighting load: 2,400 _ 115 = 21 amperes or two 15 am- pere,2-wire circuits;or two 20 ampere,2-wire circuits. Small appliance load:Two 2-wire circuits of No. 12 wire. (See Sec- tion 220-3 (b)). (Example 4 Continued Next Page) CHAPTER 9-EXAMPLES 70-425 Example No.4(Continued) Range Circuit: 8,000 ± 230 = 34 amperes or a circuit of two No. 8's and one No. 10 as permitted by Section 210-19(c). Minimum Size Sub-Feeder Required for Each Apartment(Section 215-2): Computed load (Article 220): General lighting load 2,400 watts Small appliance load, two 20 ampere circuits 3,000 watts Total computed load (without ranges) 5,400 watts Application of Demand Factor: 3,000 watts at 100% 3,000 watts 2,400 watts at 35% 840 watts Net computed load (without ranges) 3,840 watts Range load 8,000 watts Net computed load (with ranges) 11,840 watts For 115/230 volt,3 wire system (without ranges): Net computed load,3,840_ 230 = 16.7 amperes. Size of each sub-feeder (see Section 215-2). For 115/230 volt,3 wire system (with ranges): Net computed load, 11,840_ 230 = 51.5 amperes. Size of each ungrounded sub-feeder,No.6. Neutral Sub-feeder: Lighting and small appliance load 3,840 watts Range load, 8,000 watts at 70% (see Section 220-4(d)) 5,600 watts Net computed load (neutral) 9,440 watts 9,440= 230 = 41 amperes Size of neutral sub feeder, No.6 Minimum Size Feeders Required from Service Equipment to Meter Bank (For 20 Apartments-10 with Ranges): Total Computed Load: Lighting and small appliance load, 20 X 5,400 108,000 watts Application of Demand Factor: 3,000 watts at 100% 3,000 watts 105,000 watts at 35% 36,750 watts Net computed lighting and small appliance load 39,750 watts Range load, 10 ranges (less than 12 kw; Col. A, Table 220-5) 25,000 watts Net computed load (with ranges) 64,750 watts For 115/230 volt,3 wire system: Net computed load,64,750=- 230 = 282 amperes. Size of each ungrounded feeder to each meter bank: 500,000 c.m. Neutral Feeder: Lighting and small appliance load 39,750 watts Range load: 25,000 watts at 70% (see Section 220-4(d)) 17,500 watts Computed load (neutral) 57,250 watts 57,250_230 = 249 amperes. Further Demand Factor (Section 220-4(d)): 200 amperes at 100% = 200 amperes 49 amperes at 70% = 34 amperes Net computed load (neutral) 234 amperes Size of neutral feeder to each meter bank:300,000 c.m. (Example 4 Continued Next Page) 70-426 NATIONAL ELECTRICAL CODE Example No.4(Continued) Minimum Size Main Feeder(or Service Conductors)Required (For 40 Apartments-20 with Ranges): Total Computed Load: Lighting and small appliance load, 40 X 5,400 216,000 watts Application of Demand Factor: 3,000 watts at 100% 3,000 watts 117,000 watts at 35% 40,950 watts 96,000 watts at 25% 24,000 watts Net computed lighting and small appliance load 67,950 watts Range load, 20 ranges (less than 12 kw, Col. A, Table 220-5) 35,000 watts Net computed load 102,950 watts For 115/230 volt,3 wire system: Net computed load, 102,950- 230 =448 amperes. Size of each ungrounded main feeder: 1,000,000 c.m. Neutral Feeder: Lighting and small appliance load 67,950 watts Range load,35,000 watts at 70% (see Section 220-4(d) ) 24,500 watts Computed load (neutral) 92,450 watts 92,450- 230=402 amperes. Further Demand Factor (see Section 220-4(d)): 200 amperes at 100% = 200 amperes 202 amperes at 70% = 141 amperes Net computed load (neutral) 341 amperes Size of neutral main feeder:600,000 c m. See Tables 310-12 through 310-15,Notes 8 and 12. Example No.4(a). Optional Calculation for Multi-Family Dwelling Multi-family dwelling equipped with electric cooking and space heating or air conditioning and having a total floor area of 32,000 square feet with 40 apartments. Meters in two banks of 20 each plus house metering and individual sub- feeders to each apartment. Each apartment is equipped with an electric range of 8 kw nameplate rating. A common laundry facility available to all tenants (Section 210-22(b) ex- ception 1). Area of each apartment is 800 square feet. Computed Load for each apartment(Article 220) General Lighting Load: 800 square ft.at 3 watts per sq.ft. 2400 watts Electric range 8000 watts Electric heat 6 kw 6000 watts (or air conditioning if larger) Minimum number of Branch Circuits required for each apartment General lighting load 2400 watts _ 115 = 21 amp or two 15 ampere 2-wire circuits or two 20 amp 2-wire circuits. Small appliance load:Two 2-wire circuits of No. 12 (See Section 220-3(b)) Range circuit 8000 watts X 80% -. 230 = 28 amperes on a circuit of three No. 10 as permitted in Column C of Table 220-5 Space Heating 6000 watts_ 230= 26 amperes No.of circuits(See Section 210-24) (Example 4(a)Continued Next Page) CHAPTER 9—EXAMPLES 70-427 Example No.4(a)(Continued) Minimum Size Sub-Feeder required for each Apartment(Section 215-2) Computed load (Article 220): General lighting load 2400 watts Small appliance load,two 20 amp circuits 3000 watts Total computed load (without range and space heating) 5400 watts Application of Demand Factor: 3000 watts at 100% 3000 walls 2400 watts at 35% 840 watts Net computed load (without range and space heating) 3840 watts Range load 6400 watts Space heating Section 220-4(c) 6000 watts Net computed load for individual apartment 16,240 watts For 115/230 volt 3 wire system Net computed load 16,240- 230 = 71 amperes Size of each ungrounded sub-feeder No.3 Neutral Sub-Feeder(Section 220-4(d)) Lighting and small appliance load 3840 watts Range load 6400 watts at 70% (see Section 220-4(d)) 4480 watts Space heating (no neutral)230 Volt 0 watts Net computed load (neutral) 8320 watts 8320_ 230 = 36 amperes Size of neutral sub-feeder No.8 Minimum Size Feeder Required from Service Equipment to Meter Bank for 20 Apart- ments Total Computed Load: Lighting and small appliance load 20 X 5400 .... 108,000 watts Range and space heating load 20 X 14,000 280,000 watts Net computed load (20 apartments) 388,000 watts Net Computed using Optional Calculation (Table 220-9) 388,000 X .38 147,440 watts 147,440_230=641 amperes Size of each ungrounded feeder to each meter bank 2-400 MCM per phase. Neutral Feeder Lighting and small appliance load 108,000 X 38% (Table 220-9) = 41,040 watts Range load 8000 X 20 X 70% = 112,000 watts 112,000 X 38% (Section 220-4(d)) 42,560 watts (Table 220-9) computed load (neutral) 83,600 watts 83,600± 230= 364 amperes Size of neutral feeder to each meter bank 1-500 MCM Minimum Size Mains Feeder Required(less house load) (For 40 Apartments) Total Computed Load: Lighting and small appliance load 40 X 5400 216,000 watts Range and space heating 40 X 14,000 560,000 watts Net computed load (40 apartments) 776,000 watts (Example 4(a) Continued Next Page) 70-428 NATIONAL ELECTRICAL CODE Example No.4(a)(Continued) Net computed using Optional Calculation (Table 220-9) 776,000 X 28% 216,280 watts 216,280- 230 = 940 amperes Size of each ungrounded feeder required 2-750 MCM per phase. Neutral Feeder Lighting and small appliance load 40 X 5400 X 28% (Table 220-9) 60,480 watts Range load 224,000 X 28% (Table 220-9) 62,720 watts Computed load (neutral) Section 220-4(d) 123,200 watts 123,200± 230 = 536 amperes Size of neutral feeder required 2-250 MCM Add to obtain size of service conductors, the entire house load including laundry circuit(s) in accordance with applicable section of Article 220. Example No.5. Calculation of Neutral Feeder (See Section 220-4) The following example illustrates the method of calculating size of neutral feeder for the computed load of a 5-wire, 2-phase system, where it is desired to modify the load in accordance with provisions of Section 220-4. An installation consisting of a computed load of 250 amperes connected between neutral feeder and each ugrounded feeder. Neutral Feeder (maximum unbalance of load 250 amp. X 140% = 350 amperes): 200 amperes (first) at 100% = 200 amperes 150 amperes (excess) at 70% = 105 amperes Computed load 305 amperes Size of neutral feeder:500,000 c.m. Example No.6. Maximum Demand for Range Loads Table 220-5, Column A applies to ranges not over 12 kw. The application of Note 1 to ranges over 12 kw (and not over 27 kw) is illustrated in the following examples: A. Ranges all of same rating. Assume 24 ranges each rated 16 kw. From Column A the maximum demand for 24 ranges of 12 kw rating is 39 kw. 16 kw exceeds 12 kw by 4. 5% X 4= 20% (5% increase for each kw in excess of 12). 39 kw X 20% = 7.8 kw increase. 39+ 7.8 = 46.8 kw:value to be used in selection of feeders. B. Ranges of unequal rating. Assume 5 ranges each rated 11 kw. 2 ranges each rated 12 kw. 20 ranges each rated 13.5 kw. 3 ranges each rated 18 kw. (Example 6 Continued Next Page) CHAPTER 9—EXAMPLES 70-429 Example No.6(Continued) 5 X 12 = 60 Use 12 kw for range rated less than 12. 2 X 12 = 24 20 X 13.5 = 270 3 X 18 = 54 408 kw 408 -30 = 13.6 kw(average to be used for computation) From Column A the demand for 30 ranges of 12 kw rating is 15 + 30 = 45 kw. 13.6 exceeds 12 by 1.6(use 2.). 5% X 2 = 10% (5% increase for each kw in excess of 12). 45 kw X 10% = 4.5 kw increase. 45 +4.5 = 49.5 kw= value to be used in selection of feeders. Example No.7. Ranges on a 3-Phase System (Section 220-4(d)) Thirty ranges rated at 12 kw each are supplied by a 3-phase, 4-wire, 120/208-volt feeder, 10 ranges on each phase. As there are 20 ranges connected to each ungrounded conductor, the load should be calculated on the basis of 20 ranges (or in case of unbalance, twice the maximum number between any two phase wires) since diversity applies only to the number of ranges connected to adjacent phases and not the total. The current in any one conductor will be one-half the total watt load of two adjacent phases divided by the line-to-neutral voltage. In this case, 20 ranges, from Table 220-5 will have a total watt load of 35,000 watts for two phases; therefore, the current in the feeder conductor would be: 17,500_ 120 = 146 amperes. On a three-phase basis the load would be: 3 X 17,500 = 52,500 watts and the current in each feeder conductor- 52,500 = 146 amperes 208 X 1.73 Example No.8. Motors,Conductors,and Overcurrent Protection (See Sections 430-22, 430-24, 430-32, 430-52, 430-62, and Tables 310-12, 430-150,430-152,and 430-153). Determine the size of copper conductors, the motor-running overcurrent protection, the branch circuit protection, and the feeder protection, for one 25-h.p.squirrel-cage induction motor(full-voltage starting,service factor 1.15, Code letter F), and two 30-h.p. wound-rotor induction motors (40°C rise), on a 460-volt,3-phase, 60-cycle per second supply. Conductor Sizes The full-load current of the 25-h.p. motor is 34 amperes (Table 430-150). A full- load current of 34 amperes X 1.25 = 42.5 amperes (Section 430-22) requires a No. 6 conductor with 60°C insulation (Table 310-12). The full-load current of the 30-h.p. motor is 40 amperes (Table 430-150). A full-load current of 40 amperes X 1.25 = 50 amperes (Section 430-22) requires a No. 6 conductor with 60°C insulation (Table 310-12). The feeder conductor capacity will be 125 per cent of 40 plus 40 plus 34, or 124 am- peres (Section 430-24). In accordance with Table 310-12, this would require a No. 0, 60°C feeder conductor. Note. For conductors with 60°C insulation run open in air, or for conductors with temperature ratings other than 60°C,see Tables 310-12 through 310-15. 70-430 NATIONAL ELECTRICAL CODE Overcurrent Protection Running. The 25-h.p. motor, with full-load current of 34 amperes, must have running overcurrent protection of not over 42.5 amperes. The 30-h.p. motor with full-load cur- rent of 40 amperes must have running overcurrent protection of not over 50 amperes. Branch Circuit.The branch circuit of the 25-h.p. motor must have branch-circuit over- current protection of not over 300 per cent for a fuse (Table 430-153) or 3.00 X 34 = 102 amperes. The nearest standard fuse which does not exceed this maximum value is 100 amperes. For the 30-h.p. motor the branch circuit overcurrent protection is 150 per cent (Table 430-152) or 1.50 X 40 = 60 amperes. Where the maximum value of overcurrent pro- tection is not sufficient to start the motor the value for a fuse may be increased to 400 per cent (Section 430-52 Exception (a)). Feeder Circuit. The maximum rating of the feeder overcurrent protection device is based on the sum of the largest branch circuit protective device (100 ampere fuse) plus the sum of the full load currents of the other motors or 100 plus 40 plus 40 = 180 amperes.The nearest standard fuse which does not exceed this value is 175 amperes. 70-431 INDEX AC and DC Conductors in Same Enclo- Ampacities ,300-3(a) Bus-bars, copper, aluminum, in auxiliary AC-DC,General-Use Snap Switches gutters,374-6 Definitions,Switches,Art.100 Conductors,Tables 310-12 thru 310-15 Marking,380-15 Crane and hoist conductors, Table 610- Motors,430-83,Ex. 1 14(a) Ratings,Type loads,380-14 Fixture Wires,Table 402-4 Signs,600-2(b) Flexible Cords,Table 400-9(b) AC-DC Resistance Conversion, Table 9, Anesthetics, Flammable, Art. 517 (see Chap.9 also Hazardous Locations) AC Metal-Clad Cable, (see Metal-Clad Antenna Discharge Systems,810-20 Cable and Art.334) Antenna8Systems, Radio-Television, Art. AC Systems Community TV&Radio Distribution Sys- Conductor to be grounded,250-25 tems,Art.820 Grounding Connections for,250-23 Grounding of,250-5 Appliance(s) (see also Motors,Art.430), In same metallic enclosures,300-20 Art.422 Aecess and Working Space, Electrical Branch-circuit calculations,220-3 Equipment Branch circuits,definition,Art. 100 600 , Branch circuits for,210-24 Over Not over vol0 volts,710-D110-16 Control and protection,422-D Cords, (see Cords,Flexible) Accessible,Readily Accessible Definition,Art. 100 Definitions,Art.100 Disconnecting means,422-20,422-26 Ground connections,250-112(a) Feeder calculations for,220-4 Junction,pull,and outlet boxes,370-19 Fixed,Definition,Art.100 Sealing fittings (see also Hazardous loca- Grounding, fixed and portable, 250-E, tions) 550-9,551-9 Splices and taps in auxiliary gutters, Hazardous locations, (see Hazardous Lo- 374-8(a) cations) Splices and taps in wireways,362-6 Household cooking appliances Structural raceways, 357-9 Demand loads for,Table 220-5 Transformers and vaults,450-2 Installation,422-C Transformers, signs, outline lighting, Load calculations, 220-3, 220-4, Table 600-32(e) 220-5 Unfinished attics, roof spaces, knob-and- Marking,422-E tube wiring,324-8(b) Mobile Homes,in,550-5(b-c),550-7 Atmospheres (see Hazardous Locations) Motor-operated,load,210-23 Aerial Cable, Art. 342 (see Nonmetallic Overcurrent protection,single,210-20(b) Extensions) Overcurrent protection,general,422-27 Portable,definition,Art. 100 Air Conditioning Units,Room,422-F Stationary,definition,Art. 100 Branch-circuit requirements,422-42 Terminals,identification,200-10(e-f) Definition and nameplate marking, 430- Travel Trailers,in,551-5(b),551-7 53(d) Approval,Approved Disconnecting means,422-43 Definition,Art.100 Grounding,422-41 Equipment and Materials, 90-7, 90-8, Aircraft Hangars,Art.513 110-2,500-1,500-2 Air Plenums,Wiring in,300-22 Arc Lamps Airport Runways, Underground Conduc- General,410-51 tors,buried,710-3(b),Ex.2 Portable Remote-Control, Low- Motionge Studios,530-17 Alarm, Signal, Stage Equipment,520-61 energy,(se Low-Haltagezard s Circuits, As) Arcing Parts, Enclosure of (see also 725(see also Hazardous Locations) Enclosures) Alarms,Fire and Burglar,Art.800 General, 110-18 Alternators, (Generators) Art.445 Motors,430-14(b) Aluminum Conductors (see also Con- Arc Welder(s),Art.630 ductors) Arc-Welder Motors,630-C In concrete and earth,300-5(b) (see also Ampacities of Conductors, Table 430-22 Rigid Metal Conduit) (a-Exception) Aluminum Sheathed Cable (Type ALS), Nameplate Marking,430-7(a) Art.331 Arenas,Art.520 Construction,331-C Emergency Lighting, Systems for, Art. General,331-A 700 Installation requirements,33I-B Armored Cable, Art. 334 (see Metal-clad Aluminum Siding,250-44(d) (Note) Cable) 70-432 NATIONAL ELECTRICAL CODE Armories,Art.520 Boat Harbor Wiring,Art.555 Emergency Lighting Systems for,Art.700 Branch Circuit, Feeder Calculations, Arresters, Lightning, Art. 280 (see also 555-2 An BranchDischarge Systems, 810 Branch Circuits,555-2(a) Feeders,Services,555-2(b) Clearances,Over Water,555-4 Askarel Grounding,555-6 Definition,Art. 100 Receptacles,555-5 Transformers,450-23 Voltage Drop,555-1 Assembly Halls,Art.520 Bonding,250-G Emergency Lighting,Art.700 Grounding-type receptacles,250-74 Atmospheric Groups (see Hazardous Lo- Hazardous locations (see Hazardous Lo- cations) cations) 50-79 Attachment Plugs (Caps) (see also Haz- Jumpers,jointed 50-77 ardous Locations) Looselye nt,raceways,50-71 2250-7 Definition,Art. 100 Service equipment,flexible,metal Flexible Cord,on,400-16 Service raceway, metal conduit, Type, 230-63(c) Grounding 410 55 Borders, Proscenium Sidelights, Theaters, I Attics Assembly Halls,520-44 1 Knob and Tube,324-8 Metal-Clad Cable,334-13 Bored Holes Through Studs, Joists, 300- Nonmetallic Sheathed Cable,336-9 8(a) Open Wiring,320-13 Bowling Alleys,Art.520 Auditoriums,Art.520 Emergency Lighting Systems,Art.700 Emergency Lighting,Art.700 Boxes, Outlet, Switch, Pull, and Junction, Automatic,Definition,Art. 100 Art.370(see also Hazardous Loca- tions,Junction Boxes) Autotransformers Accessibility,370-19 Ballast, Electric Discharge Lighting Sys- Concealed,370-14 tems,410-76 Conductors,number in box,370-6 Branch Circuits,200-4 Construction specifications,370-C Motor Starting,430-82(b) Covers,370-15,370-18(c),370-21 Auxiliary Gutters,Art.374 Cutout Ampacities, bare and insulated conduc- Definition,Art. 100 tors,374-6 Installation,Art.373 Clearance,bare live parts,374-7 Damp locations,370-5 Construction,installation,374-9 Depth,370-14 Covers,374-4 Exposed extensions,370-12 Elevator uses,620-35 Gas pipes,fastened to,370-16 Extension beyond equipment,374-2 Grounding,250-E,250-114,300-9 Number of conductors,374-5 Insulating (see nonmetallic) Sound recording,similar equipment,640-4 Junction,pull,size,370-18(a) Splices,taps,374-8 Lighting outlets,370-17,410-C,410-16 Supports,374-3 Metallic,370-4 Nonmetallic, 324-9, 336-12, 370-3, 370-7 Auxiliary Source (c),370-23 Emergency Systems,700-11 Portable,in theaters,520-62 Ballasts, Electric Discharge Lamps, 410-74 Remote Control, signal circuits, 725- (a),410-75 42(a-2) Protection, in fluorescent fixtures, 410-71 Repairing plaster around,370-11 (e) Round, 370-2 Bare Conductor(s) Secured,300-11,370-13 Ampacities, Note 4, Tables 310-12 thru Snap switches over 300 volts not ganged, 380-8 310-15 70-8 Contact conductors, cranes and hoists, Unusedc openings,eayruns,clos 3 -19 610-C Vertical raceway 300 19 Wall, 370-10 Definition,Art. 100 Wet locations,370-5 Dimensions and resistance, Table 8, Where required,300-15 Chap.9 Feeders,Art.328 Branch Circuits,Art.210,220 Sizing conduits for,346-6 Busways,as branch circuits Underground ducts, conduits, grounded Length,364-13 neutral,230-30(a),Exc.2 Overcurrent protection,364-11 Rating,364-12 Basement (Cellars) Calculation of loads,220-2,Part B,Chap. Metal-clad cable,334-12(c) 9 Nonmetallic sheathed cable,336-8 Definition,Art. 100 Batteries,Storage (see Storage Batteries) General provisions,210-A Battery Charging Equipment (see also India-dual,lamps,defin 4 2- Art.100 Infra-red 10-3 Hazardous Locations) Maximum load,210-23 Bell Circuits,Art.725 Mobile homes,550-5 Bends (see Wiring system involved) Motor, on individual branch circuit, 430-B Block, City, Town, Village, Definition, Multiwire,definition,Art.100 800-2,820-3(b) Outside and feeders,Art.730 INDEX 70-433 Branch Circuits(Continued) Cable(s) (Continued) Overcurrent protection,210-20,240-5 Metal-clad,Art.334 Permissible loads,210-24 Mineral Insulated-Metal Sheathed, Art. Table of requirements for,Table 210-25 330 Taps from, 210-19(c), 210-25, 240-5, NM,NMC,Art.342 Ex.3 Nonmetallic Sheathed,Art.336 Through fixtures Nonmetallic Extension,Art.342 Travel trailers,551-5 Secured,300-11,370-7(b), (c) Two or more outlets on,210-24 Service Voltage,permitted rating,210-6 Definition,Art. 100 Voltage drop,210-6(c) Entrance,Art.338 X-ray equipment,660-3,660-5 Splices in Boxes,300-15 Branches from Busways,364-7 Through studs,joists,rafters,300-8 Breaker,Circuit (see Circuit Breakers) Underground,230-D,300-7,310-6 Underground Feeder and Branch Cir- Building,Definition,Art. 100 cult,Art.339 Building Wire (see Conductors) Underplaster Extensions,Art.344 Bulk Storage Plants, Art. 515 (see Haz- Cable End Fittings, changing from cable ardous Locations) to knob and tube,300-16(a) Burglar Alarm Systems,Art.800 Cable Trays (see Continuous Rigid Cable Bushing Supports) Generators,445-9 Cages and Shielding, Protective, Heat Insulating, Lampholders, Attached to Generating Equipment,665-27 flexible cord,410-24 Calculations (see Loads) Motors,430-13 Outlet boxes and fittings,370-22 Canopies Rigid Metal Conduit,346-8 Boxes and Fittings,370-15 Use in lieu of box or terminal fitting, Lighting Fixtures, 300-16(b) Conductors,Space for,410-10 Busways,Art. 364 Cover Branch circuits,364-11 Combustiblebbti Finishes, re- Branches from,364-7 nishes, Covering Dead ends closed,364-5 quired between Canopy and Box, 410-13 Extension thru walls and floors,364-4 Live parts exposed,410-3 Length,as branch circuits,364-13 Marking,364-14 Caps(see Attachment Plug) Overcurrent protection,364-8,364-9,364- Capacitors, Art. 460 (see also Hazardous 12 Locations) Reduction in size,364-10 Connections at Services,230-73 Support,364-3 Draining Charge,460-6 Use,364-2 Induction,Dielectric Heating,665-26 Cabinets and Cutout Boxes,Art.373 X-ray Equip.,660-16 Construction specifications,373-B Capacity,Interrupting,General,110-9 Damp,wet locations,373-2 Cartridge Fuses,240-F Definitions,Art. 100 9 Deflection of conductors,373-6 Disconnection,240-18 Insulation at bushings,373-6(b) Cellars(see Basement) In walls,373-3 Cellular Concrete Floor Raceways, Art. Switch enclosures,no splices,taps,373-8 358 Unused openings,373-4 Connection to Cabinets,358-4 Wiring space,373-9 Definition,358-1 Cablebus,Art.365 Discontinued Outlets,358-11 Conductors,365-3 Header Ducts,358-3 Ampacity,365-3(b) Inserts,358-7 Number,365-3(c) Junction Boxes,358-5 Overcurrent Protection,365-5 Markers,358-6 Size,365-3(c) Number of Conductors,358-9 Supports,365-3(d) Size of Conductors,358-8 Terminations,365-8 Splices,358-10 Types, 365-3(a) Use,358-2 Definition,365-1 Cellular Metal Floor Raceways,Art.356 Fittings,365-7 Connection to Cabinets,356-11 Grounding,365-9 Discontinued Outlets,356-7 Marking,365-10 Definition,356-1 Support,365-6 General,356-12 Conductor,365-3(d) Inserts,356-10 Use,365-2 Junction Boxes,356-9 Cable(s) (see also Heating Cable) Markers,356-8 Armored AC,Art.334 Number of Conductors,356-5 Border Lights, Theaters, Assembly Halls, Size of Conductors,356-4 520-44(b) Use,356-2 Communication, Remote-control, Signal Churches(see Public Assemblies) Circuits,725-7 Cinder Fill Continuous, outlet to outlet,fitting to fit- Metal conduits and electrical metallic tub- ting,300-12 ing,in or under,346-3,348-1 70-434 NATIONAL ELECTRICAL CODE Circuit(s) Climbing Space Branch(see Branch Circuits) Line Conductors on Poles,730-14(e) Burglar Alarm,Art.800 Clock Outlets, Connection to Branch cir- Central Station,Art.800 cuits in dwellings,220-3(b) Communication,Art 800 Clothes Closets,Light Art.100 Fixtures,410-8 Control,Definition,430-71 Clothing Manufacturing Plants, 500-6, Fire Alarm,Art.800 Art.503 (Hazardous Locations) Grounding,Art.250 Code Impedance,110-10 Arrangement,90-3 Less than 50 Volts,Art.720 Definitions,90-4,Art.100,110-3 Grounding,250-8 Enforcement,90-7 More than 600 Volts,Art.710 Examination of Equipment for Safety, Services,230-L 90-8 Motor,Art.430-B Interpretation,90-6,Appendix Power, Signal, Remote-control, Low En- Purpose,90-1 ergy,Art.725 Revisions,90-10 Remote-control,Motors,Controllers,430- Rules,90-5,110-3 F Scope,90-2 Signal Circuits,Art.725 Wiring Planning,90-9 Telegraph,Art.800 Telephone,Art.800 Collectors,Cranes and Hoists,610-22 Theaters, Assembly Halls, etc., Loads, Color Code 520-41 Branch Circuits,210-5 Unidentified,200-5 Grounding conductor, 210-5, 250-57(b), Circuit Breakers, Art. 240 (see also Haz- boa ardous Locations.) Switchboards and Panelboards,384 25 Accessibility and Grouping,380-8 Combustible Dusts (see Hazardous Loca- Circuits Over 600 Volts,230-106,710-21 lions).Art.502 Definition,Art.100 Common Main Grounding Conductor, Disconnection of Grounded Conductors, 250-53 380-1 Enclosures,380-3 Common Grounding Electrode,250-54 General,110-9,240-H Common Neutral Overcurrent Protection Feeders,215-5 Generators,445-4 Outside Wiring,730-7 MTransformers, 430r 50-3430 Communication Circuits,Art.800 38-B Definition,Art.100 Panelboards,384 B Rating,Motor Branch Circuits,430-57 General,800.AGrounding,800-E Rating, Nonadjustable Trip,240-5(a) Ex.No.1,24 Protector Ground,800-31 b Service Overcurrrentent Cable Sheath,800-31(a) Protection,230-90 ( ) Services,Disconnecting Means,230-70 Electrode,800-31(b-5) Over 600 Volts,230-106 Electrode Connection,800-31(b-6) Setting, Adjustible Trip, 240-5(a), Exc. Insulation,800-31(b-1) No.2 Physical Damage,800-31(b-4) Switches,Use as,380-11 Run in Straight Line,800-31(b-3) Wet Locations, in, 380-4 Size,800-31(b-2) Circuit Directory,panelboards,110-22 Outside Overhead Conductors,800-C Circuits Requiring Protection, 800-11 Clamp,Ground,250-116,250-117 Entering Building,800-11(c-4) Class 1 and 2 Circuits, Remote-Control, Insulation,Cables,800-11(c-2) Low-Energy Power,Signal Circuits, Insulation, Single, Paired, 800-11 Art.725 (c-1) Class I, Class II, Class III Locations (see On Buildings,800-11(c-3) Hazardous Locations) Lightning Protection,800-12 Cleaning and Dyeing Plants, Hazardous On Poles,800-11(a) Liquids in,500-4,Art.501 Attachment to Cross Arms,800-11 (a-2) Clean Surfaces, grounding connections, Climbing Space,800-11(a-3) 250-118 Relative Location, Other Conduc- Clearance(s) (see also Enclosures, Isola- tors,800-11(a-1) tion.and Space) Protection,800-B Antennas,810-13,810-18,810-54 Installation,Conductors,800-3 Community Antenna Systems,Art.820 Separation,800-3(a) Conductors, Open, Outside Branch Cir- Open Conductors,800-3(a-1) cuits and Feeders,730-18,730-19 Raceways,Boxes,800-3(a-2) Elevators, Dumbwaiters, Escalators and Shafts,800-3(a-3) Moving Walk Panels,620-72 Vertical Runs,800-3(b) Lighting Fixtures,Flush,Recessed,410-64, Protective Devices,800-2 410-74(b) Hazardous Locations,800-2(b) Live Parts Location,800-2(a) Bare Conductors, Auxiliary Gutters, Omission of Fuses,800-2(d) 374-7 Protector Requirements,800-2(c) Circuits Over 600 Volts,710-D Underground Circuits,800-D Switchboards,Panelboards,384-7,384-8 Circuits,800-21 INDEX 70-435 Communication Circuits (Continued) Conductors (see also Cords, Flexible; and Underground Circuits (Cont.) Fixture Wires) Relative to Other Conductors, 800-21 Aluminum, Ampacities of,Tables 310-14, (a) 310-15 Underground Block Distribution,800-21 Aluminum,Properties of,Table 8,Chap.9 (b) Ampacities, 310-11, Tables 310-12 thru Communication Systems,Chap.8 310-15 Motors,430-B Community Antenna Television and Raceway (More than three in) Note 8, Radio Distribution Systems, Tables 310-12 thru 310-15 Art.820 Amplifier Circuits,640-5 General,820-A,820-F Application,310-2,Table 310-2(a) Material,820-2 Bare,Definition,Art.100 Prevention,Fire Spread,820-10 Boxes and Fittings,Junction,370-6,370-7 Scope 820-1 Branch Circuits,Art.210 Grounding,820-E Buried,310-6 Cable Busways,Art.364 Electrode,Electrode Connection,820- Cabinets and Cutout Boxes,373-5,373-6 8(a-6,7) Capacitor Circuits,460-8 Insulation,820-8(a-1) Cellular Concrete Floor Raceways,Art. Protection,820-8(a-5) 358 Straight Line,820-8(a-4) Cellular Metal Floor Raceways,Art.356 Size,820-8(a-3) Circuit, Equipment,820-9 Less than 50 Volts,Art.720 Installation,820-C Power, Signal, Remote-Control, Low- Entering Buildings,820-5 energy,Art.725 Inside Buildings Over 600 Volts,Art.710 Light and Power,820-6(a) Combinations,Table 3,Chap.9 Other Conductors,820-6(e) Computations of, Examples, Chap. 9, Raceways and Boxes,820-6(b) Part B Shafts,820-6(c) Concealed Knob-and-Tube,Art.324 Vertical,820-6(d) Conduit or Tubing, Number in, 346-6, Outside Buildings Table 350-3,Tables 1,IA,Chap.9 Between Buildings,820-4(d) Construction,General,310-2 Lead-in Conductors,820-4(b) Copper, Ampacities, Tables 310-12, 310- Light and Power Conductors, 820-4 13 (e-1) Copper,Properties,Table 8,Chap.9 Lightning Conductors,820-4(e-3) Cords,Flexible,Art.400 On Poles,820-4(a) Corrosive conditions,310-7 Other Communication Systems,820-4 Covered,Definition,Art.100 (e-2) Cranes and Hoists, 610-B, 610-C, 610-31, Over Roofs,820-4(c) 610-41 Protection,820-B Different Systems,300-3,725-16 Block Distribution,820-3(b) Dimension of Shield,Coaxial Cable Asbestos-Varnished-Cambric Insulated, Grounding,820-3 Table 7,Chap.9 Protective Devices,820-3(a) Lead-covered,Table 6,Chap.9 Underground Circuits,820-D Rubber-covered and Thermoplastic- Coaxial Cable,820-7 covered,Table 5,Chap.9 Light and Power Conductors,820-7(a) Electrical Metallic Tubing,Art.348 Compressors, Refrigeration (see Refrig- Elevators, Dumbwaiters, Escalators, and eration Compressor Motors and Moving Walks,620-B,620-C,620-D controls) Enclosure,Grounding,250-1,250-D Concealed Feeder,Bare,Art.328 Definition,Art.100 Fixture Wires,Art.402 Knob-and-Tube,Art.324 Flame-Retardant Braid, Over 600 volts, Concentric Knockouts, Bonding Jumpers, 710-4 Service,250-72(d) Flexible Metal Conduit,Art.350 Gages,General Provisions,110-6 Concrete General Provisions,110-7 Encased electrodes,250-83(a) Generators,Size,445-5 Metal raceways and equipment in, 300- Grounded 5(b) Alternating Current Systems, 250-23, Conductor Fill,Maximum permitted 250-25,Identification,200-6,200-7 Auxiliary gutters,374-5,374-8 Overcurrent Protection,230-90(b) Cellular concrete floor raceways,358-9 Service,Disconnection,230-70 Cellular metal floor raceways,356-5 Overcurrent Protection,230-90(b) Continuous rigid cable supports (cable Size,Change in,240-13 trays),318-6,Table 318-6(a) Switches,Disconnection,380-1 Electrical metallic tubing,384-6 Use and Identification,Art.200 Flexible Metal conduit, 350-1, 350-3, Grounding,250-J Table 350-3 Connections,250-K Liquidtight flexible metal conduit,351-4 Induction and Dielectric Heating Equip- Rigid metal conduits,346-6 ment Rigid nonmetallic conduits,347-11 Capacity of Supply,665-6 Structural raceways,357-6 Power Supply for Therapeutic Equip- Surface metal raceways,352-4 ment,665-30(b) Wireways,362-5,362-6 Inserting into raceways,300-18 70-436 NATIONAL ELECTRICAL CODE Conductors(Continued) Conductors(Continued) Insulating materials,310-3 Sizes of Insulation,Art.310 Asbestos-Varnished-Cambric Insulated, Fixtures,Flush,Recessed,410-65 Table 7,Chap.9 Hazardous Locations, Class I Instal- Bare Conductor Feeders,328-2 lations,501-13 Cellular Concrete Floor Raceway,358-8 Motion Picture Projectors,540-14 Cellular Metal Floor Raceway,356-4 Resistors and Reactors,470-7 Flexible Metal Conduit,Table 350-3 Theaters,Assembly Halls,etc.,520-42 Lead-covered,Table 6,Chap.9 Insulation at bushings,No.4 and Larger, Liquid-tight Flexible Metal Conduit, 373-6(b) 351-4 Lighting Fixtures,410-E Mineral Insulated-Metal Sheathed Ca- Lightning Rods,Spacing from,250-34 ble,330-11(a) Liquid-Tight Flexible Metallic Conduit, Rubber Covered,Table 5,Chap.9 Art.351 Services,230-B,230-23,230-31,230-41, Metal Enclosures,Spacing from Lightning 230-101(a) Rods,250-34 Signs and Outline Lighting, 600-21(b), Metal-clad Cable,Art.334 600-31(b) Mineral Insulated-Metal Sheathed Cable, Structural Raceways,Art,357-8 Art.330 Surface Metal Raceways,352-3 Minimum size,310-8 Thermoplastic-covered,Table 5,Chap. Motion Picture Projectors,Sizes,540-13 9 Motor Circuits,430-B Underfloor Raceways,354-4 Multioutlet Assembly,Art.353 Wireways,362-4 Nonmetallic Sheathed Cable,Art.336 Sound Recording and Similar Equipment, Nonmetallic Extensions,Art.342 640-3 thru 640-7,640-9(b) Number of,in Storage Batteries,480-7(c) Auxiliary Gutters,374-5 Stranded,310-9 Cellular Concrete Floor Raceways, Support of,in vertical raceways,300-19 358-9 Surface Metal Raceway,Art,352 Cellular Metal Floor Raceways,356-5 Switchboards and Panelboards, 384-3, Continuous Rigid Cable Supports 384-9 (Cable Trays) 318-6, Table 318-6 Temperature Limitations of,310-4 (a) Theaters, Assembly Halls, Portable Stage Electrical Metallic Tubing,348-6 Equipment,520-68 Elevators,620-32,620-33 Underfloor Raceway,Art.354 General Installations,300-17 Underground Feeder and Branch Circuit Metal Conduit,346-6 Cable,Art.339 Remote Control Circuits,725-15 Underplaster Extensions,Art.344 Rigid Flexible Metal Conduit, Table Ungrounded,Overcurrent Protection,240- 350-3 11 Rigid Nonmetallic Conduit,347-11 Ungrounded,Services,230-90(a) Signs and Outline Lighting,600-21(d) Welders,Electric Sound Recording,640-3 Capacity of Supply,630-11,630-31 Structural Raceways,357-6 Overcurrent Protection,630-12(b),630- Surface Metal,352-4 32(b) Surface Metal Raceways,352-4 Wet Locations,310-5 Theaters,Assembly Halls,520-5 Wireways,Art.362 Underfloor Raceways,354-5 Wiring,General,Art.310 Wireways,362-5 X-ray Equipment,660-3,660-7 Organs,650-4,650-5 Conduit Nipples,Note Table 1,Chap.9 Outlet Boxes,Temp.Limits,410-11 Conduit,Rigid Metal,Art.346 Outside Wiring,Art.730 Conduits Over 600urr Volts,t PrArt.c n, Circuits,Mechanical Protection of Remote Overcurrent ble 310-Art.240 and Note control,725-17 10 to Tables 8,Chap.hthru 310-15 Conductors, Number in, Tables 1, 1A, 2 s of,Table 8,ofC 9 and 3,Chap. Raceways, Number Conductors in Dimensions,Tabl 4,Chap. (see n Conductors,Number of,in) Electrical metallic tubing, t.348 Radio and Television Antenna Distribution Systems,Art.820 Flexible,Grounding,Services,230-63(c) Antenna Systems,810-B,810-C Flexible Metal,Art.350 Grounding,810-58 thru 810-60 Liquid-tight Flexible Metal,Art.351 Transmitting Stations,810-70 Metallic,grounding runs 25 ft.,250-33 Railway, Power and Light from, General Outside Wiring,730-10 Provisions,110-19 Rigid Metal,Art.346 Remote Control and Signal Circuits, Art. Rigid nonmetallic,Art.347 725 C catons Rigid Metal Conduit,Art.346 Aluminum,copper conductors,110-14 Selection of,Examples,Chap.9,Part B Cabinets and Extensions Cellular Metal Service (see Service Cable and Service Floor Raceways,356-11 Conductors) Grounding conductor,250-K Service-Entrance,Definition,Art.100 Knife switches,380-7 Service-Entrance,Art.338 Terminals,General Provisions,110-14 Signs and Outline Lighting, Installation, Connectors 600-21,600-31 Boxes,370-7 Simplified Wiring Tables, Tables 310-20, Cable,Theaters,and Assembly Halls,520- 310-21,Sections 310-20,310-21 67 INDEX 70-437 Connectors (Continued) Cords (Continued) Electrical metallic tubing, 348-8, 348-14 Flexible (Cont.) (c) Lampholders, Insulating Bushings,410- Metal-clad cable,334-5 24 Pressure (Solderless), Definition, Art. Lighting Fixtures,410-14 100 Motion-Picture Projectors,540-15 Rigid metallic conduit,346-9 Overcurrent Protection,240-5,400-9 Rigid nonmetallic conduit,347-6 Power and Signal Circuits,Remote-con- Constant-Potential Generators, Art. trol,Low-energy,725-13 445 Prohibited uses,400-4 Overcurrent protection for,445-4(a) Pull at joints and terminals,400 10 Sound Recording, Similar Equipment, Construction Specifications (see listed in Grouping Conductors,640-7 Articles covered) Splices and Taps prohibited,400-5 Continuity Types,Table 400-11 Electrical,metal raceways and cables,250- Tinsel,minimum size,400-7 75,250-76; service equipment,250- Overcurrent Protection,400-9 71,250-72 Uses,400-3 Grounding, metal boxes, grounding-type Corrosion, Protection, metal equipment, receptacles,250-74,250-114 300-5 Mechanical,raceways and cables, 300-12; conductors,300-13 Corrosive Conditions Continuous Duty,Definition,Art.100 Conductor Insulation,310-7 General,110-11 Continuous Load Couplings Applications,210-23(b),220-2,384-16(c) Electrical metallic tubing,348-8 Definition,Art.100 Rigid metal conduit,346-9 Continuous Rigid Cable Supports, Art. Rigid nonmetallic conduit,347-6 318 Running threads at,346-9(b) Ampacity,318-6 Cove Lighting,Space for,410-9 Construction,318-3 Definition,318-1 Covers Extension Through Walls,318-4(g) Auxiliary Gutters,374-4 Grounding,318-5 Boxes and Fittings,370-15 Installation,318-4 Switches,Flush Snap,380-9 Spacing of Cables,Table 318-6(a) Cranes(s),Art.610 Use,318-2 Conductors,610-B,610-C Control (see also Hazardous Locations) Control,610-D Panels,Clearance around,Elevators,620- Flexible Cords,400-3 72 Grounding,250-7,250-43,610-F Remote Hazardous Locations,503-13 Induction and Dielectric Heating Equip- Motors and Controllers, Disconnecting ment,665-12 Means,430-112 Low-Energy Power and Signal Circuits, Overcurrent Protection,610-E Art.725 Cross-Sectional Areas, Overcurrent Protection,240-5 Ex.5 Conductors,Tables 5,6,7,8,Chap.9 X-ray Equipment,660-B Conduits,Table 4,Chap.9 Control Centers Current-Carrying Capacities (see Guarding live parts,110-17 Ampacities) Headroom,110-16(f) Current Limiting Devices (see Circuit Illumination at,110-16(e) Breakers and Fuses) Working spaces,110-16 Curtain Motors, Theaters, Halls, etc., Controller(s) (see also Hazardous Loca- 520-48 lions) Cutout Cases,Grounding,250-43(b) Bases(see Fuseholders) Definition,Art. G10 Box, efinition,Art.1(0 Motor,Art.430.G Boxes and Cabinets,Art.373 Resistors and Reactors Thermal Cutout) Conductor,Insulation,470-7 (see Incandescent Lamps as Resistors,470-8 Cutting Tables,Motion Picture,530-D Welders, Electric, 630-21 Damp Location,Definition,Art.100 Convenience Outlet, (see Receptacles) Damp or Wet Locations Conversion Table, DC to AC con- Boxes and Fittings,370-5 ductor resistances, Table 9, Cabinets and Cutout Boxes,373-2 Chap.9 General,110-11 Lampholders,410-43 Cooking Unit, Counter-Mounted, Lighting Fixtures,410-4 Definition, Art. 100 (see also Open Wiring,320-14 Ranges) (see also Ovens) Overcurrent Protection,Enclosure,240-17 Copper Conductors (see Conductors, Panelboards,384-17 Copper) Receptacles,410-54 Cords (see also Heater Cords) (see also Rosettes,410 58 Hazardous Locations) Damper (Flue), Control, Fixed Stage Flexible Cords,Art.400 Equipment,520-49 Ampacities,Table 400-9(b) Dance Halls,Art.520 70-438 NATIONAL ELECTRICAL CODE Data Processing Systems,Art.645 Direct Burial (Continued) Circuits and Interconnecting Cables,645-2 cable, not less than 18 in. when Disconnecting Means unprotected,339-3(c) General Building Areas,645-3(b) Underground service cable, 230-32(a), Processing Rooms,645-3(a) 310-6 Grounding,645-4 DC Resistance, Conversion to AC Marking,645-5 Resistance,Table 9,Chap.9 Dead Ends DC Systems, Grounding, 250-3, 250-4, Busways,364-5 250-22 Wireways,362-9 Disconnecting Means Dead Front, Stage Switchboards, 520- Appliances,422-D 21 Capacitors,460-8(c) Definitions Cranes,610-D 90-4,Art.100 Definition,Art.100 Deflection of Conductors Elevators,620-51 Auxiliary gutters,374-9(e) Fuses and Thermal Cutouts,240-18 Cabinets and cutout boxes,373-6 Induction and Dielectric Heating Equip- ment,665-8 Deicing and Snow Melting Instal- Mobile Homes,550-4 lotions,424-G Motor and Controllers,430-H,430-126 Complete units required,424-73 Services,230-J General rules,424-71 Connections,Ahead of,230-73 Grounding,424-79 Over 600 Volts,230-103 Installation of heating cables, units, pan- Signs,600-2 els,424-75 Travel Trailers,551-4 Installation of nonheating leads,424-76 Welders,Resistance,630-33 Junction Boxes,424-78 X-ray Equipment,600-4,660-14 Marking of units,424-77 Discontinued Outlets Nonhe74ng leads factory assembled,424- Cellular Concrete Floor Raceways,358-11 Test,424-80 Cellular Metal Floor Raceways,356-7 Use,424-72 Underfloor Raceways,354-7 Delta-Connected, 4-Wire, 3-Phase Sup- Dissimilar Metals, 110-14, 250-116, 346-1, 348-1 ply,Identifying high leg,200-6(c) Door(s),Transformer vaults,45043 Demand Factor (see also Load(s) ),Defi- nition,Art.100 Double Insulated, Appliances and Demand Loads for Household Cook- Tools,250 45 ing Appliances,Table 220-5 Double-Pole, Switched Lampholders, Depth of Boxes, Boxes and Fittings, 370- 410-46 14 Drainage Capacitor charge,460-6 Detached Buildings, Oil-insulated Equipment,501-5(d) transformers in,450-24(d) Oil-insulated outdoor transformers,450-25 Detearing Equipment, Electrostatic, Oil-insulated lightning arresters,280-22 516-4 Raceways,230-101(g) Deteriorating Agencies,General,110-11 Transformer vaults, for, 450-46 Device,Definition,Art.100 Dressing Rooms Diagrams Motion Picture Studios,530-C Feeders,215-6 Theaters,Assembly Halls,etc.,520-F Motor Feeder and Branch Circuits, 430-1 Drip Loops, Conductors Entering Build- (a) ings,230-49 Dielectric Heat Generating Equipment Service heads,230-51 Art. 665 (see Inductive and Drip Pans,Generators,445-3 dielectric Heat Generating Equip.) Driveways Differential Protection Clearance of conductors,730-18(a) Motors over 600 volts,430-124(c) Clearance of service drop,230-26 Swimming pool lighting circuits, 680-4 Protection of service-entrance cables,230- (g-2) 46 Different Systems, Conductors, in Drop,Service,Definition,Art. 100 same enclosure,300-23,725-16 Drop,Voltage,210-6(c),215-3 Dimensions Dry Location, Definition, Art. 100 (see Conductors,Tables 5 thru 7,Chap.9 damp or wet locations) Conduit and Tubing,Percent Area,Table Dryers,Clothes 4,Chap.9 Grounding,250-60 Dimmers,Stage Switchboards, 520-25, 520- Demand factors,Table 220-6 53(e) Dry-Type Transformers,450-21 Dip Tanks,Paint,Art.516 Dual-Voltage Motor, Locked rotor Direct Burial rating,430-7(b-3) Rigid nonmetallic conduit, 24 in., 347-2 Duct(s) (a);Bulk-storage plants,515-5(a); Air Handling,300-21,300-22 service stations,514-8 Bare grounded neutral underground, 230- Underground feeder and branch circuit 30(a),Ex.2 INDEX 70-439 Duct(s) (Continued) Elevators,etc. (Continued) Sealing at building from underground Grounding,250-43(c),620-J system,230-33 Machine Room,620-H Underground services,230-32(a) Overcurrent Protection,620-G Ventilating,300-21,300-22 Overspeed Equipment,620-K Wiring in,300-22 Duct Heaters Emergency Systems, Art. 700 (see also Installation of,424-F Stand-By Power Generation Sys- Dumbwaiters (see Elevators),Art.620 Circuits,700 Crt.750 Connection at Services,230-73,230-74 Dusts (see Hazardous Locations) Dust-Ignition-Proof,502-1 Control,700-D Dustproof,Definition,Art. 100 Power,Supply, y,P 70000-iBon,700-E,700-21 Service Disconnecting Means,230-74 Dust-tight,Definition,Art. 100 Service-drop Conductors,230-2,Exc.2 Duty,Type,Definition,Art. 100 Unit Equipment,700-F Duty Cycle (Welding),630-31 Enamel,Coating of Dwellings (see also Appliances, Boxes, Electrical Metallic Tubing,348-1 General Equipment, Indoor Use Only Branch Circuits, Fixtures, Ground- ing,and similar general categories) Metal Box 300-5(a) s,370-5 Branch Circuit Voltages,210-6(b) Clothes Dryers, Demand Factors, Table Metal Cabinets,373-10(a) 220-6 Removing, for grounding connections, Farm,services,220-4(m) 250-75 Feeder Load, Calculations for, 220-4, Rigid Metal Conduit,346-1 220-7,Exc.1,and 4,Part B,Chap. Enclosed,Definition,Art. 100 9 Enclosure(s) (see also Hazardous Lo- Lighting Loads for,Table 220-2(a) Panelboards as services, 384-16 a 384- cations) ( ). Arcing Parts,General, 110-18 Ranges,Demand Load,Table 220.5 Cabinets, Cutout Boxes, Space, 373-7, 3-11 Receptacle Circuits Required,220-3 b373-is9,s,3 Res ( ) CraneslevatHoists, a 610-2 Receptable Outlets Required,210-22(b) Elevators, Dumbwaiters, Escalators, Elbows, Metallic, Protection from Moving Walks Corrosion,300-5 Live Parts,620-3 Electric Discharge Lighting Machine,Controller,620-H Connection to Fixtures,410-14 Induction and Dielectric Heating,665-22 More than 1 Volr 410- Installations over 600 Volts,710-31 1000 Volts or less,410-P Mercury-Vapor Lamp Aux. Equip., Signs and Outline Lighting,Art.600 410-50 Wiring,Equipment,410-P,410-Q Panelboards, Protection,240-C Electric Welders (see Welders) dioEquip., 384-18- Radio Equip.,810-71(a) Signs, Outline Lighting, 600-8, 600 34(g) Electrical Metallic Tubing,Art.348 Bends,How Made,348-9 (h) Bends,Number in one run,348-10 Switches,380-3 Connectors and couplings,348-8 Grounding, 380-12 Construction Specifications,348-B Energy-Limiting, Class 2 Control and Minimum and maximum sizes,348-5 Signal Circuits,725-31 Number of Conductors in,348-6 Reaming of,348-11 Enforcement,Code,90-7 Supports for,348-12 Equipment (see also separately listed Threads on,348-7 items) Uses permitted for,348-1 Definitions,Art. 100 Wet Locations,in,348-4 Examination of,90-8,110-4 Electrode,Grounding Grounding,250-E Installation,General Provisions,Art. 110 Common, to be Used to Ground Con- ductor Enclosures and Equipment, MoreLesr than 56 600 o,Art.Art.7 250-54 than of, Volts, 710 Concrete encased,250-83(a) Mounting 110-13 Gas Piping as,250-82(b) Sealable,Definition,Art. 100 Made (wire in concrete footing, driven Service,Definition,Art.100 Pipe, Rod, or Buried Plate), 250- Escalators (see Elevators),Art.620 83 Metal Frame of Building as,250-82(a) Examination of Equipment for Metallic Water Piping System,250-81 Safety,90-8 Railway tracks,250-85 Examples (Computations) Chap.9,Part B Resistance to Ground of,250-84 Electrostatic Equipment, Spraying and E Leads sin same enclosure as motor, con- Detearing,Paint,516-4 trol, relay, and ammeter Conduc- Elevators, Dumbwaiters, Escalators, tors,300-3(e) and Moving Walks,Art.620 Overcurrent Protection for, when used Cables,620-E with constant potential AC Gen- Conductors,620-B,620-C,620-D erators,445-4(a) Control,620-F Exhaust Ducts,Wiring in,300-22 70-440 NATIONAL ELECTRICAL CODE Exits,Emergency Lighting for,Art.700 Fire Pump(s) at Services, 230-73, 230- Explosive Atmospheres, Gases, Liquids, C 94(b) Dusts, Ignitible Fibers, Lints and Emergency Power Supply,Art.700 Flyings(see Hazardous Locations) Motors,Overcurrent Protection,430-31 Explosion-Proof, Definition, Art. 100 Rembte-control Circuits,430-72 (see also Hazardous Locations) Service Drops,230-2 Exposed (see also Enclosure) Fire-Stopped Partitions,300-21 Extensions,Boxes,and Fittings,370-12 Firewall(s) Live Parts,Definition,Art.100 Dividing Buildings, Definition of Build- General,110-16 ing,Art.100 Wiring Methods,Definition,Art.100 Wiring Through,300-21 Extension(s) Fitting(s) (see also Wiring Types) Auxiliary Gutters, Beyond Equipment, Boxes and,Art.370 374-2 Definition,Art.100 Boxes and Fittings,Exposed,370-12 Fixed Electric Space Heating Equip- Cellular Concrete Floor Raceways,358-4 ment,Art.424 Cellular Metal Floor Raceways, Con- Cables and Panels,424-E nai Cabinets,356-11 Area Restrictions,424-38 Nonmetallic,Art.342 Clearances,Wiring Underfloor Raceways,354-15 Ceilings,424-36 Wireew ays, ,Art.344 From Wireways, Through Other Objects,Openings,424-39 Walls,424-37 ir Walls,362-8,362-10 Construction,424-34 Externally Operable, Definition, Art. Installation an Finish, Ceilings,424-42 100Cables,424-44 Face Plates, Receptacles, to General,424-48 Grounding,sses 410-95 Nonheating Leads,424-43 Minimum Thicknesses for, 380-9, 410- Marking 52(b) Cables,424-35(a) Factors,Multiplying Panels,424-35(b) Converting DC Resistance to AC re- Panels sistance,Table 9,Chap.9 Complete Units,424-47 Feeder Calculations, General,424-46 Farm B220-4(1)s� Splices,424-40 Tests,424-45 Fe Art.215,Art.220 Control and Protection,424-C Bare Bare CoConductor,Art.328 Controllers,424-21 Calculation of Loads, 220-4, 220-7, Part Disconnecting Means, 424-19, 424-21, B,Chap.9 424-22 Definition,Art. 100 Location,424-20 Farm Buildings,for,220-4(1) Indicating,424-22 Grounding Means,215-7 Motor,Art.430-B Motor Driven Equip., 424-19(c), 430-H Outside Branch Circuits,Art.730 Overcurrent Protection,424-23 Overcurrent Protection Duct Heaters,424-F Motor,430-EStations, Air Flow,424-59 Supply ces le24 Locations, Approval,424-58 Taps i4 Inaccessible Motors, 430-59 Condensation,424-62 Disconnecting means,Location,424-65 Taps, an ft. and 25 ft., 240-15 Excs. 5 Elevated Inlet Temperature,424-60 and 6 Fan Circuit Interlock,424-63 Ferrous Metals, Protection from tor- General,424-57 rosion,300-5 Installation,464-61,464-66 Festoon Lighting, Outside Wiring, Limit Controls,464-64 730-6,730-13 General,424-A Supports,outside Circuits,730-13 Branch Circuits Requirements,424-3(a) Festoons, Portable Stage Equipment, Sizing,424-3(b) 520-65 Installation,424-B Fiber Bushings, AC Cable Ends, 334- Conductors,424-11 10(b) General 424-9 Fibers, Lint, Flyings,, Ignitible (see Grounding,424-14 Hazardous Locations),Art.503 Location Exposed to Physical Damage, 424- Projectors,Motion Art.Picture4 12-(G) in Wet Areas,424-12(b) SStorage,5 Marking,540-34 Spacing,Combustible Materials,424-13 Viewing,o 5i Cutting,54 Patching Special Types,424-10 Tables, 530- Marking,424-D Heating Elements,424-29 Finishing Processes,Art.516 Name Outdoor PDeeI424-28 cing and Snow Melting, Fire Alarms 424-G Circuits,Art.800 Connections at Services, 230-73, 230- General,424-71 424-73 INDEX 70-441 Fixed Electric Space Heating (Cont.) Fuseholders Outdoor De-Icing (Cont.) Cartridge Fuses,240-F Grounding,424-79 Link Fuses,240-G Installation Over 600 Volts,710-21(b) Cables,Units,Panels,424-75 Plug Fuses,240-E Nonheating Leads,424-76 Rating,Motor Controllers,430-90 Junction Boxes,424-78 Type S,240-22 Marking,424-77 Fuses,Art.240 Loca- Tests, 424-80 (see also Hazardous Panels,424-ECrtride tions) Fixed Equipment, Grounding, 250-42 Disconnecting Means,240-18 through 250-44,250-57,250-58 Enclosures,240-C Fixture Stud,Construction,410-34 General,240-6 Fixture Wires,Art.402 Generators,Constant-Potential,445-4(a) GAmpacities,Table 402-4 In oup installation 2 0-14 of motors,430-53(c) Types,Table 402-6 parallel,240-14 Link,240-G Fixtures (see Lighting Fixtures) Location,240-19(a),240-16 Marking,240-20(c),240-22(i),240-23(c), Flame-Retardant Braid, Conductors, More than 600 Volts,710-4 M 240-24(f) Motor-Running Overcurrent Protection, Flammable Anesthetics, Art. 517 (see 430-C also Hazardous Locations) Motor Branch Circuit protection,430-D Plug, Edison-base Type, Classification Flammable Gases and Vapors (see Hazardous Locations) and Marking,240-E Potential (Voltage) Transformers, 450- Flammable Liquids (see Hazardous Lo- 3(c) cations) Ratings,240-6 Flashers, Time Switches, Similar De- Services Over 600 Volts,230-106(c) vices,380-5 Shielding,240-19 Flatirons,Smoothing,422-13 Spaces in Cabinets and Cutout Boxes, Signals required,422-12 373-11(a) Stands for,422-11 Time-delay plug-type in residential oc- cupancies,240-4 cont Temperature-limiting means required, Time-lag, not in control circuits, 240-5, 422-8 Exc.5 Flexible Cords (see Cords, Flexible), Type S,240-22 Art.400 Garage(s) Flexible Metal Conduit,Art.350 Commercial,Art.511 Minimum size,350-3 Definition,Art. 100 Supports,350-4 Elevators,Dumbwaiters,Escalators,Mov- Use,350-2 ing Walks,in,620-52 Floors,Receptacles,410-53 Grounding,Fixed Equip.,250-43 Flue-damper Control, Fixed Stage Residential,Art.512 Equipment,520-49 g Gases (see Hazardous Locations) Fluorescent Lighting Fixtures Gas Pipe Auxiliary equipment, remote from, 410- Grounding uGndin Conductor,ng Elect 250-82(b)ino Grounding Point of Attach- Ballast protection required,410-71(e) ment,250-112(b) Connection of,410-14 Gasoline Bulk-Storage Plants, Art. 515 Load calculations (see also Hazardous Locations) Ampere ratings,ballasts 210-23(b) Gasoline Dispensing and Service Sta- Branch circuits,210-24 tions, Art. 514 (see also Hazard- Raceways,410-26 ous Locations) Snap Switches for,380-14(c) Conductor Insulations where exposed to Special provisions, 1000 Volts or less, gasoline, 501-13 410-P Special provisions, more than 1000 volts, Gages,Conductor,General, 110-6 410-Q General Provisions, Installation of Fluoroscopic Equipment,Art.660 Wiring and Equipment,Art. 110 Footlights, Theaters, Assembly Halls, etc. General Requirements for Wiring 520-43Methods,Art.300 Boxes or Fittins,Forming Shells, Underwater Swim- Changing Raceway,a Cable Outlet,ch t Op nl5 Wir- ming Pool Lighting Fixtures, ing,300-16(a) 680-4 Conductors, Full-load Current,Motors Different Systems,300-3 Alternating Current Inserting in Raceways,300-18 Single Phase,Table 430-148 Insulating Bushings, for Raceways No. Three Phase,Table 430-150 4 or Larger,373-6(b) Two Phase,Table 430-149 Number of,in Raceways,300-17 Direct Current,Table 430-147 Supporting,Vertical Raceways,300-19 Fundamental Rules,90-5 Expansion Joints,Raceways,300-6(b) Furnace, Circuits, Grounding, Trans- Exhaust and Ventilating Ducts, Wiring 300-2formers,Installation,450-24(c) Free Length ofWire at Outlets,300-14 70-442 NATIONAL ELECTRICAL CODE Gen.Reqs.Wiring Methods(Continued) Grounding (Continued) Grounding Metal Enclosures,300-9 DC Systems,250-3,250-4,250-22 Induced Currents in Metal Enclosures, Electrodes,250-H 300-20 Elevators,620-J Mechanical and Electrical Continuity, Enclosures, Metal, Wiring Methods, Conductors,Raceways,Cables,300- 300-9 10,300-12,300-13 Equipment,Cord Connected,250-45 Protection Against Fixed Equipment,250-42,250-43 Corrosion,300-5 Fixtures,Lampholders,etc.,410-R Physical Damage,300-4 Freezers,250-45 Prevention of Fire Spread,300-21 Generators,445-8 Sealing, Raceways, Change in Tempera- Hazardous Locations, 501-16, 502-16, ture,300-6(a) 503-17 Secured in Place, Wiring and Equip- Induction and Dielectric Heating Equip- ment,300-11 ment,665-D Temporary Wiring,300-23 Instrument Transformers, Relays, etc., Through Studs,Joists,Rafters,300-8 250-L Underground Runs,300-7 Isolated Systems,250-26 Voltage Limitations,300-2 Lightning Arresters,250-M Generator(s),Art.445 Location of Connections,250-C,250-K Metal Faceplates 8 ft. Vertically or 5 ft. Balancer Sets,445-4 Horizontally from Grounded Sur- Bushings,445-9 faces,410-95(a) Conductor Sizes,445-5 Metal Enclosures for Conductors,250-33 Drip Pans,445-3 Metal Siding,250-44 Emergency Systems,700-8 Methods,250-F Grounding,250-43,445-8 Mobile Homes,550-9 Guards for Attendants,445-7 More than 600 Volts Between Conduc- Location,445-1 tors,710-6,710-7 Marking,445-2 Motion Picture Studios,530-20,530-66 Overcurrent Protection,445.4 Motors and Controllers,430-L Protection of Live Parts,445-6 Nonelectrical Equipment,250-44 Set,Emergency System,700-8 Organs,650-3 Stand-by Power,Art.750 Portable Equipment,250-45 Goosenecks, Service Cables, Forming Radio and Television, 810-15, 810-21 and Connecting to Service-Drops thru 810-29, 810-58 thru 810-60, 230-51 810-71 Ranges and Similar Appliances,250-60 Ground Receptacles, 250-74, 410-55 (see also Clamps,250-116 Hazardous Locations) Definition,Art.100 Bonding at boxes,250-74,250-114 Voltage to,Definition,Art.100 Branch Circuits must Include Ground- Grounded,Definition,Art.100 ing Conductor for,210-7 Connections to Circuits of Two or Grounded, Effectively, Communica- More Outlets,Minimum and Maxi- tion System, Definition, 800- mum Ratings of,210-21(b) 2(d) (4) Design of,410-55 Grounded Conductor (see also Con- Grounding-Type, 210-7, 250-74, 410-55 ductors) Minimum Rating of,410-52(a) Definition,Art.100 When Required,for New Work and as Replacements,210-21(b) Grounded System, Polarity Identifica- Refrigerators,250-45 tion,200-6 Services,230-63 Grounding,Art.250 Signs and Outline Lighting,600-5 d Recording Equip., 640 4(b), Exc. Sound AC Systems,250-5,250-23,250-25 4 Air Conditioning Units,422-41, 250-45and Swimming Pools,680-7 Antenna (see Grounding, Switchboard Frames,384-12 TV) Switches,380-12 Appliances,422-16 Systems and Circuits,250-A,250-B Bonding,250-G Theaters,Assembly Halls,etc.,520-81 Capacitors,460-10 Tools,Motor Operated,250-45 Circuits,250-A,250-B Transformers,450 8 Less than 50 Volts,720-10 Travel Trailers,551-9 Clothes Washers,Dryers,250-45,250-60 Conductor(s),250-J X-ray Equipment,660-E Connections,250-K,250-113 Grounding Type Attachment Plugs, Definition,Art.100 Design of, and Use with Movable, Enclosures,250-D Self-restoring-type Grounding Mem- Installation,250-92 bers,410-55 Sizes,250-95 Connections,Location,250-C,250-K Grouping, Switches, Circuit Breakers, 380-8 Continuity,250-75 Control Circuits, Class 1, 725-21; Class Group Installation,Motors,430-53 2,725-44 Guarded,Definition,Art. 100 Controls,Radio Equipment,810-71(b)Cranes and Hoists,610-51 Guarding andParts) , Live Guards (see also Enclosures Deicing,Snow Melting Systems,424-79 Circuit BreakerHandles,240-19(b) Dish Washing,250-45 INDEX 70-443 Guarding,Guards (Continued) Hazardous Location(s), Class II, Art. Elevators, Dumbwaiters, Escalators, 502 (Dusts) Moving Walks,620-71 Bonding,502-16(b), (d), (e) Generators,445-7 Circuit Breakers and Fuses,502-6 Handlamps,Portable,410-37 Control Transformers,Resistors,502-7 Lamps Dusts,502 Motion-Picture Projectors,540-16 Flexible Cords,502-12 Theaters, Assembly Halls, Dressing Fuses and Circuit Breakers,502-6 Rooms, etc., 520-44, 520-47, 520 General,502-1 61,520-65,520-71,520-72 Grounding,502-16 Live Parts,General Provisions, 110-17 Lighting Fixtures,502-11 Motion Picture Studios,530-15,530-64 Lightning Protection,502-16(c) Motors, Motor Controllers, Live farts, Live Parts,502-15 430-K Motor Controllers,502-6 Motors,Portable,430-143 Motors and Generators,502-8 Over 600 Volts,710-5,710-34 Receptacles and Attachment Plugs,502-13 Transformers,450-7 Sealing,502-5 Gutters, Auxiliary (see Auxiliary Gut- Signal, Alarm, Remote-control, and ters) Intercom Systems,502-14 Handlamps,Portable,410-37 Surge Protection,502-3 Hangars,Aircraft,Art. 513 Switches,502-6 Transformers and Capacitors,502-2 Hazardous Areas (see Hazardous Loca- Utilization Equipment,502-10 tions),Art.500 Ventilating Piping,502-9 Hazardous Atmospheres,Art.500 Wiring Methods,502-4 Class I Locations,500-4 Hazardous Location(s), Class III, Class II Locations,500-5 Art.503 (Fibers,Flyings,Lint) Class III Locations,500-6 Circuit Breakers and Fuses,503-4 Control Transformers,Resistors,503-5 Specific Occupancies,500-3 Special Precautions and Groups A-G, Electric Cranes and Hoists,503-13 500-2 Electric Trucks,503-14 Hazardous Locations,Art. 500,TIA 146 Flexible Cords,503-10 Aircraft Hangars,Art.513 Fuses and Circuit Breakers,503-4 Anesthetics,Flammable,Art.517 General,503-1 Bulk Storage Plants,Art.515 Grounding,503-17 Lures, Dusts,Explosive,Art.502 Lighting Fixtures,503-9 Fibers, Flyings, Lint, Highly Combust- Live Parts, 503-16 ible Materials,Art.503 Motor Controllers,for 503-4 Finishing Processes,Art.516 Motors and Generators,503-6 11 Garages,Commercial,Art.511 Receptacles and Attachment Plugs, 503- Garages,Residential,Art.512 Signal, Alarm, Remote-Control and In- Gases,Flammable,Art.500,501 Gasoline Service Stations,Art.514 tercom Systems,503-12 Group Designations,Art.500-2 Storage-Battery Charging,503-15 Liquids,Flammable,Art.500,501 Switches,503-4 Tentative Interim Amendment,p.70-465 Transformers and Capacitors,503-2 Utilization Equipment,503-8 Vapors,Flammable,Art.500,501 Ventilating Piping,503-7 Hazardous Location(s), Class I, Art. Wiring Methods,503-3 501, TIA 146 (Flammable Gases Header(s)and Liquids) Raceways,Cellular Metal Floor356-1, Bonding,501-16(b), (d), (e) Circuit Breakers and Fuses,501-6 356-2,cre 356-5,356-6 Conductor Insulation,501-13 Cellular Concrete Floor Raceways, 358- Control Transformers and Resistors, 1,358-2,358-3,358-6,358-7 501-7 Structural Raceways, 357-1(b), 357-5, Drainage of Equipment,501-5(d) 357-7 Flexible Cords,501-11 Header Duct(s),Art.358 Fuses and Circuit Breakers,501-6 Heat Generating Equipment,Art.665 General,501-1 Heater Cords,Table 400-11,422-8(a) Grounding,501-16 Lighting Fixtures,501-9 Heater Elements,Marking,422-31 Lightning Protection, c 501-16( ) Heating Appliances Live Parts,501-15 Calculations,Art.220 y Meters,Instruments,and Relays,501-3 Motor Controllers,501-6 InGrounding,250E 22C Motors and Generators,501-8 Marking,4 E Receptacles and Attachment Plugs, 501- Overcurrent Protection,422D 12 Sealing Fittings and Compound, 501- Heating Cables,Art.424 Signal, 5(c Alarm, Remote-control, and Heating,Fixed Electric Space,Art.424 Communication Systems,501-14 Heavy-Duty Lampholders Switches,501-6 Branch Circuits,210-24,Table 210-25 Tentative Interim Amendment,p.70-465 Definition,210-8 Transformers and Capacitors,501-2 Unit Loads,220-2(b) Utilization Equipment,501-10 Hermetic Type Refrigeration Coln- Wiring Methods,501-4 pressors (see Refrigeration) 70-444 NATIONAL ELECTRICAL CODE Hoists and Cranes,Art.610 Institutions, Emergency Lighting, Disconnecting Means—Motors and Con- Art.700 trollers,430-112,610-D Instrument Transformers, Grounding, Flexible Cords,400-3 250-L Hoistway,Definition,Art. 100 Instruments,Meters,Relays Hood,Metal Grounding,250L Theaters,Assembly Halls,etc.,520-24 Hazardous Locations,Class 1,501-3 Hospitals Insulating Joints, Fixtures on Metal, Anesthetizing Locations in,Art.517 Metal Lath,Ceilings,Walls,410-93 Emergency Light and Power Systems, Insulating Links, Metal Pull Chains, Art.700 Lighting Fixtures,410-95(b) Hotels Insulation Emergency Light and Power Systems, Conductor, Art.310- 3 00 3 Art.700 GHazardous Locations, FlexibleIdentification on Class I Installations,501-13 GuCords Motion-Picture Projectors,540-14 Grounded Conductor,Conductor,400-1 Theaters,Assembly Halls,etc.,520-42 Grounding nduc ,Art.40 200 Double,250-45 Grounded Conductors, 200 Fixture Wire,402-3,Table 402-6 Identified,Definition,Art. 100 Flexible Cords,Table 400-11,400-C Immersion Heaters, Portable Types, Appliances,422-3 422-9 Over 300 Volts,400-8 Incandescent Lamps (see also Hazardous Resistance,General,110-20 Cables,424-E Locations) Service Conductors, 230-4, 230-22, 230- Guards 30,230-40 230-Aircraft Hangars,511-6(b), (3-5(a) Splices and Joints, 110-15 Garages, Boos 540-16c) Insulators,Open Wiring,Art.320 Projection Booths, Theater Dressing Rooms,520-72 Intercommunication Systems, Art. 800 Medium-base Lampholders,410-49 (see also Hazardous Locations) Mogul-base Lampholders,410-49 Intermittent Duty,Definition,Art.100 ReSnap aptSrs,470-8 Switches for,380-14(b) Interpretation(s), 90-6, Official, How to Obtain,Part D,Appendix Independent Supply,700-15(a) Interruption Capacity,General,110-9 Emergency Lighting Supply, Emergency Power Spply 700-I5(b) Intrinsically Safe Equipment, Hazard- Supports, Services, Over Buildings, 230- ous Locations,500-1 25 Introduction,Art.90 Wiring,Emergency Circuits,700-17 Irons,Smoothing,422-13 X-ray Control,660-14 Isolated Individual Branch Circuit(s) Definition,Art. 100 Definition, under Branch Circuit, Art. Systems,Grounding,250-26 100 Isolating (see also Guarding and Guards) May Supply Any Load, ,2 Single-24 Appli- Means,Over 600 Volts,710-22 Overcuance, Protection, Switch,Definition,Art.100 ance,210-20(b) Induced Currents, Metal Enclosures, Isolation Coy 600 Elevation 300-20 Volts,710-11. Induction and Dielectric Heating, Art. Joints (see also Splices and Taps) 665 Grounding Conductor,250-91(a) Guarding and Grounding,665-D Insulation,Fixtures,410-93 Output,665-9,665-10,665-18 Insulation of, 110-15 Power Supply,665-B,665-C Strain at,Fixtures,400-10 Therapeutic,665-E Wrenchtight, Conduit Grounding Con- Inductive Loads ductor,250-91(b) Switches, Types, Ratings, Lighting Fix- Joists tures,380-14(c) Boxes on,370-13(b) Motors,430-83,430-109 Concealed Knob and Tube Work,Attics, Signs,600-2(b) Roof Spaces,324-8 Holes through or Notches in,300-8 Infrared Lamp Industrial Heating Ap- Metal-clad Cable pliances Exposed,334-12 Branch Circuits,210-24(d) In Accessible Attics,334-13 General Rules,422-15 Nonmetallic Sheathed Cable, in Base- Overcurrent Protection,422-27(c) ments,336-8 Inserting Conductors in Raceways, Open Wiring,Crossing,320-12 300-18 Jumpers,Bonding Inserts Conduit Joints, Hazardous Locations, Cellular Concrete Floor Raceways,358-7 500-1 Cellular Metal Floor Raceways,356-10 Expansion Joints, Telescoping Sections Underfloor Raceways,354-14 of Raceways,250-77 In Sight From Grounding-Type Receptacles,250-74 Motors,Motor Controllers,430-4 Material,Size and Attachment,250-79 Signs,600-2(a) Service Equipment,250-72 INDEX 70-445 Junction Boxes (see also Boxes and Pull Lampholders Boxes) Branch Circuits Supplying Accessibility,370-19 15-20 amps,Medium-Base,210-24(a) Cellular Concrete Floor Raceways,358-5 30-50 amps, Heavy-Duty, 210-24(b), Cellular Metal Floor Raceways,356-9 (c),(d) Covers,370-15,370-18(c) Circuits Less Than 50V,for,720-5 Deicing and Snow Melting Cables, 424- Construction,410-H 78 Damp or Wet Locations,410-4,410-43 Motor Controllers and Disconnects not Double-Pole Switched,410-42 used for,430-10 Heavy-Duty, Nonheating Cable Leads,424-43 Defined,210-8 Separation,from Motors,430-145(b) Unit Loads,220-2(b) Size, Infra-red Lamps,422-15 Conductors No.6 and Larger,370-18 Outdoor Lighting,730-25 Conductors No.6 and Smaller,370-6 Pendant Construction Specifications,370-C Not in Clothes Closets,410-8 Swimming Pools,680-5 Not in Theater Dressing Rooms,520-71 Supports,370-13 Screw-shell Types for Lamps only,410-41 Switch Enclosures not for,373-8 Signs and Outline Lighting,600-22 Underfloor Raceways,354-13 Unswitched Over Highly Combustible Keying, Induction and Dielectric Material,410-6 Heating Equipment,665-20 Laundry Outlets, Dwellings 210-22(b), Knife Switches 220-3(b) Connection,380-7 Length(s) Busways used as Branch Circuits,364-13 Construction Specifications,380-B Enclosures,380-3 Free Conductors at Outlets and Switches, Position,380-6 300-14,424-43,424-76 Ratings,380-13 Nonmetallic Flexible Tubing with Open Knob and Tube Work,Art.324 Wiring,320-7 Knockout(s) Nonmetallic Rigid Conduit, 347-16(a), b Bonding Service Equipment,250-72(d) Pull and Junction Boxes,370-18(a) (1) Openings to be Closed,370-7,370-8 Rigid Metal Conduit,346-14(a) Labels Space Heating Cable Nonheating Cords,Flexible,400-12 Leads,424-43 Warning, Heat Generating Equip., 665_ Taps, 25 Cooking Appliances,210.19(c),Exc.5 Lacquers and Paints Feeders, 10-ft. Rule, 240-15, Exc. 5; Application, i. 25-ft.Rule,240-15,Exc.6 Atmospheres,500-2,500-4,Art.501 Individual Lampholders(a) or Fixtures, 210.19(c),Exc.2(a) Individual Outlets,210-19(c),Exc.2(b) Lamp(s) (Lighting Fixtures), Art. 410 (see also Hazardous Loca- Motor Feeders,25-ft.Rule,430-59 tions) Light(s) (see also Lamps and Lighting) Arc (see Arc Lamps) Border,Cables for,Theaters,520-44(b) Electric Discharge,410-P,410-Q From Railway Conductors, 110-19 Fluorescent,Art.410 Scenery,Theaters,Halls,520-63 Guards(see Guarding and Guards) Lighting Handlamps(see Handlamps) Branch Circuit(s), Calculation of Load, Incandescent,Art.410 220-2 Bases for,410-49 Emergency,Art.700 As Resistors,470-8 Feeders,Calculation of Load,220-4 Infra-Red(see Infra-Red Lamps) Fixtures (see Lighting Fixtures) Mercury-Vapor, Enclosure of Resistors Outlet,Def.,Art.100 and Regulators,410-50 Lighting Fixt ,Art.410 (see also Haz- Motion-Picture Projectors ardous Locations) Nonprofessional Type,540-33 Autotransformers, Ballasts Supp y t m Professional Type,540-14,540-16 Fluorescent Fixtures,410-76 8 Motion-Picture Studios,in Supplying Circuits,200-4 Film Storage Vaults,530-51 Auxiliary Equipment,410-75 Stages,530-16,530-17 Boxes,Canopies,Pans,410-C Viewing,Cutting Tables,530-41 Branch Circuits, Outdoor,Location,730-26 Sizes,210-23,210-24 Portable Unit Loads,220-2s,210-6, a Flexible Cords for,400-3ta ( ) (b) Motion-Picture Studios,in,530-16,530- Clothes Closet,410-8 410-73 17 Combustible Material,Near,410-5 Show-Windows,400-6 Connection, Theaters,Assembly Halls Fluorescent,410-14 Border and Proscenium,520-44 General,410-25 Dressing Rooms,520-72 Construction of,410-F,410-N Festoons,520-65 Corrosive (see Damp,etc.) Footlights,520-43 Coves,Adequate Space,410-9 Scene Docks,in,520-47 Damp,Wet,or Corrosive Locations,410- Stage,Arc,520-61 4,410-43 Switchboards,Pilot Lights,520-53 Electric Discharge Lighting Wattage Marking, Flush and Recessed Systems 1000 V or less,410-P; Fixtures,410-68 Systems over 1000 V,410-Q 70-446 NATIONAL ELECTRICAL CODE Lighting Fixtures (Continued) Load(s) (Continued) Electric Discharge Lighting (Cont.) Mobile Homes,550-11 Voltages-Dwelling Occupancies,410-73 Stager Motors, Conductors, nt, 430-B Loads,Fluorescent,410- in-Qters,Assembly Halls,520-41 Thea- Autotransformers in Ballasts,410-76 Ballast Protection,410-71(e) Location(s) Connection,410-14 Capacitors,460-2 Flush,410-M Crane and Hoist Disconnecting Means, Grounding,410-R 610-D Live Parts,410-3 Definition,Art.100 Location,410-B Electric Discharge Lighting Transform- Motion-Picture Studios,Art.530 ers(over 1000 Volts),410-84 Outdoor(see Damp,etc.) Elevator Motor Disconnecting Means, Overcurrent Protection,Wires and Cords, 620-51(b) 240-5,Exc.3 Foreign Pipes, Accessories, Transformer Polarization,410-27 Vaults,450-47 Raceways,410-26 Generators,445-1 Recessed,410-M Grounding Connections at Electrodes, Show Windows,410-7 250-112 Supports,410-D Hazardous(see Hazardous Locations) Swimming Pools,680-4 Junction Boxes,370-19 Theaters and Assembly Halls,Art.520 Lamps Outdoors,730-26 Wet(see Damp,etc.) Lighting Fixtures,410-B Wiring,410-E Lightning Arresters, Lightning Arresters (see also Lightning Indoors,280-21 Protection and Rods),Art.280 Outdoors,280-22 Antenna Discharge Systems,810-20 Mobile Home Disconnecting Means and Connections at Services,230-73 Branch-Circuit Protective Equip- Grounding,250-M ment,550-4 Industrial Stations,280-A Motion-Picture Projection Equipment, Radio and Television Equipment 540-17 Receiving Stations (Antenna Discharge Motors,430-14 Units),810-20 Motor Disconnecting Means,430-H Transmitting Stations,810-57 Motor Feeder Taps,430-59 Services Over 600 Volts,230-107 Overcurrent Devices,240-B Protective Devices for Communication Lightning Protection Arresters and Rods)(see also Light- Circuits,800-2(a) Wing Resistors and Reactors,470-1 Communication Circuits,800-12Service Disconnecting Means,230-70(b) Hazardous Locations,501-16(c),502-3 Service Heads,230-51 Lightning Rods (see also Lightning Service Overcurrent Protection, 230-91, Arresters and Protection) 92,93 As a Ground,250-86 Splices 8 and Taps,Auxiliary Gutters, 374- Spacing from Conductor Enclosures and Sign Switches,600 2(a) Equipment,250-34,250-46 Lint,Flyings (see Hazardous Locations) Swimmingns o oil Junction er EnclosnresBoxes and Liquid-Tight Flexible Metal Con- TraSwitchboards,384-4,384-6 Suit,Art.351 System Ground Connection,250-52 Live Parts (see also Enclosures, Guard- Transformers and Vaults,450-2 ing) Travel Trailer Disconnecting Means and Appliances,Disconnecting Means,422-D Branch-Circuit Protective Equip- Capacitors,Guarding,460-11 ment,551-4 Generators,Protection,445-6 Ventilation Openings for Transformer Guarding,General,110-17 Vaults,450-45(a) Hazardous Locations,501-15,502-15,503- Wet (see Wet Locations) 16 Locked-Rotor,Motor Current Lamp Terminals,Lampholders,410-80 LoCode Letters Motor Lighting Fixtures, Lampholders, Lamps, Conversion Table,430-151 Receptacles,Rosettes,410-3 Refrigeration Compressors, 430 83, Exc. Lighting Systems, Electric Discharge, 430-110 1000 Volts or less, 410-P, Over 3, 1000 Volts,410-Q Lockouts,Double Where Required , Motors and Motor Controllers,430-K Over 250 Volts to Ground,250-76(b) Transformers,Guarding,450-7 Wholly InsulatedBushings Used, 373- Load(s) b) Appliances,Household Cooking,Demand Low-Energy Poer Art~100 Circuit,Art.725 Table,220-5 Branch Circuits, Calculations, Art. 220; Low-Energy, Remote-control, Low- Pert Homes,5.9 Voltage Power and Signal Mobile 50.11 Cir- cuits,Art.725 Branch Circuits,Maximum,210-23,Table Lugs 210-25 Branch Circuits, Permissible, 210-24, Connection to Terminals, General, 110- Table 210-25 14 Clothes Dryers,Demand,Table 220-6 SolderlesS Type p ato e lctroe s,C 250-115; Feeders, Calculations, Art. 220; Part B, Connectionn2 Chap.9 INDEX 70-447 Made Electrodes (see Electrodes, also Mobile Homes (Continued) Grounding) Nameplates,550-4(c) Markings (see articles on wiring and Power Supplies,550-3 equip.involved) Receptacle Outlets, Types, Where Re- quired,Mechanical Execution of Work,110-12 Testi 550-6 550-10 Mercury-Vapor Lamps, Enclosures for, Wiring g'Me hods and Materials,550-8 410-50 Mogul Lampholders,410-49 Metal-Clad Cable, MC and AC Series, Art.334 Monorails,610-1 Accessible Attics, Type AC Cable in, Motion-Picture 334-13 Projectors,Art.540,520-2 Anti-Short Bushings,at Ends,334-10(b) Grounding,250-43 Bends,334-9 Studios,Art.530 Conductors Theaters,Assembly Halls,etc.,Art.520 Type AC,334-5(b) Type MC,334-5(a) Motor(s),Art.430 Construction Air Conditioning Units,422-F Type AC,334-4(b) Appliances,Motor Driven,Art.422 Type MC,334-4(a) Branch Circuits,430-B Definition,334-1 Combination Loads,430-25,430-63 Exposed Work,334-12 Continuous Duty,430-22 Marking,334-3 Intermittent Duty,430-22 Supports,334-8 Single Motor,430-22 Through Studs,Joists,and Rafters,300-8 Taps,430-53,430-58 Uses Two or More,430-24 Type AC,334-6(b) CapacitorWund Rotor Secondary,430-23 Type MC,334-6(a) Circuits,460-8,460-9 Voltages,334-2 Rating,460-7 Metal-Enclosed Switchgear, 230-101(h), Circuits,430-B 230-106 Code Letters,Table 430-7(b) Metal Frame of Building Coded and Noncoded, Setting of Branch Circuit Devices, Tables 430-152, Grounding Electrode,250-82(a) Resistance to Ground,250-84 430-153 Combined Overcurrent Protection (Start- Metal Hood, Stage Switchboard, 520- 24 ing and Running) 430-54 CombustileMetal Working Machine Tools, Art. Con uctor(s),430 Mater Bl,430-14 670 Control Circuits,430-F Conductors,Supplying,670-4 Controllers,430-G Definition,670-2 Hazardous Locations,501-6,502-6, 503- Nameplate Data,670-3 4 Metal Siding,Grounding of,250-44 Current,Full Load Metallic Outlet Boxes (see Boxes) Alternating Current Single Phase,Table 430-148 Metallic Raceways (see Raceways) Three Phase,Table 430-150 Metals,Dissimilar,346-1,348-1 Two Phase,Table 430-149 Meter(s) Direct Current,Table 430-147 CurtainCases,Grounding,250-123,250-124 D sco nectingters Me nsS430-H Halls,520 48 Connection and Location at Services, Disconnects and Controllers not as Junc- 230-73,230-94 tion Boxes,430-10 Grounding to Circuit Conductor,250-61 Fault Protection,430-D,430-E Hazardous Locations,Class I,501-3 Feeder demand Factor,430-26 Feeders,Calculation of Load,2204 Mineral Insulated-Metal Sheathed Cable,Art. 330 Fuseholder,Size of,430-56 Bends,330-7 General,430-A Construction Specifications,330-C Grounding,250-D,430-L Definition and Description,330-1 Grouped,430-24,42,53,87, 112 Fittings,330-9 Guarding,430-133 Hazardous Locations,501-8,502-8,503-6 Insulation and Resistance,330-10 Supports,330-4 In Sight from,Defined Rule for Disconnects,430-4 Terminating Seals,330-8 Liquids,Protection from,430-11 (see also Through Studs,Joists,etc.,330-5,300-8 Use,330-2Hazardous Locations) Wet Locations,330-6,300-5(c) Live Parts,Protection,430-133 Mobile Homes,Art.550 Location,430-14 Appliances, a) Maintenance and Ventilation,430-14 Branch Circuits,550-5 Marking,430-7;Terminals,430-9 Branch-Circuit Protective Equipment, Metal Working Machine Tools,Art.670 550-4(b) Multispeed, Branch Circuits,430-22(a) Calculations of Loads,550-11 Definition,550-2 Locked Rotor Code Letters, 430-7(b) Disconnecting Means,550 4(a) (I) Marking,430-7 Grounding,550-9 550-9(a) Running Protection, 430-32(a) (1), Insulated Neutral Required,55 Lighting Fixtures,550-7(b) 00 Volts, 430.0- Over 600 J 70-448 NATIONAL ELECTRICAL CODE Motor(s) (Continued) Nonmetallic Extensions (Continued) Overcurrent (Overload) Protection, 430- Installation C As Aerial Cable,342-7(b) Overheating, Dust, Accumulations, 430- As Surface Extensions,342-7(a) 16 Permitted Uses,342-3 Part Winding Described,430-3 Prohibited Uses,342-4 Projectors,Motion-Picture,540-12 Splices and Taps,342-5 Restarting,Automatic,430-43 Nonmetallic Rigid Conduit (see Rigid Sealed (hermetic-type)Refrigerator Corn- Nonmetallic Conduit) pressor Described,430-6(b) Nonmetallic Sheathed Cable, Art. 336 Short Circuit Protection,430-D,430-E Accessible Attics,336-9,334-13 Starting, Shunting,430-35 Bends,336-10 Terminal Housings,Size,430-12 Construction Three Running Overcurrent Units Type NM,336-2(a) Required Table(Unattended,etc.), Type NMC,336-2(b) 430-37nand Definition,336-1 Ventilation MaMotor-Generator,intenance,43 630-C-14 Exposed Work,336-6 Welders,Diagram,. rah Circuit, Insulating Devices,336-11 Wiring Branch 430- Marking,336-2(c) 1(a)Wiring Space,430-10 Supports,336-5Through Studs, Joists, Rafters, 300-8, Motor-Circuit Switch, Definition, Art. 336-7 100 Unfinished Basements,336-8 Motor-Generator Arc Welders,630-C Uses, 336-3 Mounting of Equipment,110-13,300-11 Nontamperable (see Tamperability) Moving Walks (see Elevators),Art.620 Occupancy,c( Lighting Loads, Table 220- Multioutlet Assembly,Art.353 Official Interpretations, Obtaining, Definia) tion, Art.f Load,220-2 Part D,Appendix Definition, 100 Multiple Conductors (Conductors in Openings in 37 E uipm4nt to be Parallel),310-10 Multiple Fuses (Fuses in Parallel), O Accessible eWirin on Insul tors2Art.320 240-14 Conductor Separation,320-6 BranchMultispeed Motors Conductor Types Permitted,320-4 Locke Circuits,CodeLe 430-22(a) Definition,320-1 Making,430-7 tor Letters,430-7(b) Drip Loops, 320-14 Running'Protection,430-32(a),430-32(c) Flexible Nonmetallic Tubing,320-7 Passing through Walls and Floors,320-9 Nameplate (see articles on wiring and Separation from Metal Work,320-10 equip.involved) Separation from Piping,320-11 Neat Installation,110-12 Supports,320-5 Switches,320-15 Neutral Exc.1, Tie Wires,320-8 Bare,where Permitted,40(a Exc0(a), Use,320-2 Exc.2,23Service Exc. Definition, Art. Bonding to Service Equipment,250-72(a) Operable, Externally, Common Feeder,215-5 Feeder Load,220-4(d) Operating Rooms,Hospital,Art.517 Equipment,Grounding to,250-61 Emergency Light and Power,Art.700 Groun250 25o f250-2r 6;Afor DCe250-3,5 0- Organs,Art.650 4,250-22 Electronic,640-1 Identification,Art.200 Outlet(s) Ranges and Dryers,Grounding,250-60 Boxes (see Boxes,Outlet) Switchboards,Connections, 384-3(b) Definition,Art. 100 Uninsulated, where Permitted, 230-30, Devices,Branch Circuits,210-21 338-3(b) Discontinued, Night Clubs,Art.520 Cellular Concrete Floor Raceways,358- 11 Nipples, Conduit, Fill Permitted, Note Cellular Metal Floor Raceways,356-7 Preceding Table 1,Chap.9 Underfloor Raceways,354-7 Nonautomatic,Definition,Art. 100 Lighting,Definition,Art. 100 3 Multioutlet Assembly, Nonelectrical Equipment, Ground- Receptacle,Definition,Art. 100 ing,250-44 Outlet, Switch, and Junction Boxes Nongrounding-Type Receptacles, Re- and Fittings, (see Boxes) placements,210-21(b) Outline Lighting,Art.600 Nonmetallic Boxes (see Boxes) Definition,Art. 100 Covers for,370-15(a) Grounding,Conductor Size,250-97 Ungrounded Metallic Fixtures, Lamp- holders,Faceplates within reach of Output Circuits grounded surfaces,410-95(a) Amplifiers,640-5 Heat Generating Equip.,665-9,665-10 Nonmetallic Extensions Outside Branch Circuits and Feed- Fittings,342-6 Description 342-1 ers,Art.730 INDEX 70-449 Outside Branch Circuits (Continued) Overcurrent Protection (Continued) Calculation of Load Panelboards,384-15,384-16 Branch Circuits,730-3(a) Paralleled Fuses and Circuit Breakers Feeders,730-3(b) 240-14 Circuit Entrances and Exits, Buildings, Remote-Control,240-5,Exc.5,Art.725 730-11 Services Conductors, Entrance Conductor,230-K Clearance from buildings,730-19 Over 600 Volts,230-106 From Ground,730-18 Single Appliance,210-20(b) Covering,730-4 Sound Recording Equipment,640-10 Size,730-5,730-6 Supplementary,240-30 Disconnection,730-8 Switchboards,384-2 Festoon Supports,730-13 Theaters,Assembly Halls,Stage Switch- Lighting Equipment on Poles,730-7 boards,520-23,520-25,520-52.520- Mechanical Protection,730-20 53,520-62 Outdoor Lighting Equipment, 730-25, Time Delay, Residential Occupancies 730-26 240-4 Overcurrent Protection,730-9 Transformers,450-3,450-5 Spacing,Open Conductors,730-14 Travel Trailers,551-4(b) Supports Vertical Position,Enclosures,240-17(c) Festoons,730-13 Welders Open Conductors,730-12 Resistance,630-32 Over Buildings,730-15 Transformer,630-12 Wiring on Buildings,730-10 X-Ray Equipment,660-5 Ovens, Wall-Mounted (see also Cook- Over 600 Volts,General,Art.710 ing Units) (see also Ranges) Braid-Covered Insulated Conductors, Branch Circuits,210-19,210-24 Connections,422-17 Open Runs,,714 Definition,Art.100 Circuit Conductors, 0-32 Demand Loads,Table 220-5 Circuit Interrupting Devices Grounding,250-57,250-60 Circuit Breakers,710-21(c) Overcurrent Protection,Art.240 Fuseholders and Fuses,710-21(b) Appliances,422-27 Load Interrupters,710-21(c) Busways,364-8 thru 364-12 Elevation of Unguarded Live Parts, 710- Capacitors,460-8(b) Enclosure (f) Circuit-Breakers,240-H nclos71e for Electrical Installations, Circuits 710-31 Grounding,710-7 Branch,210-20 Grounding of Shielding Tape,710-6 Capacitor,460-8,460-9 Less than 50 Volts,720-5 Headroom above Working Spaces, 710- Remote-control and Signal 34(e) Class 1 Systems,725-8,725-19 Illumination of Working Spaces, 710-34 d) Class 2 Systems,725-32,725-41,-42 Indoor Installations,710-10 Low-Voltage Power,725-22 Isolating Means,710-22 Cords,Flexible and Tinsel,400-9 Metal-enclosed Equipment,710-12 Cranes and Hoists,610.E Moisture, Mechanical Protection, Metal- Current-Limiting Defined,240-27 sheathed Cables,710-8 Disconnecting and Guarding,240-D Outdoor Installations,710-11 Elevators, Dumbwaiters, Escalators, Shielding, Rubber-Insulated Conductors, and Moving Walks,620-G 710-5 Emergency Systems,700.E Wiring Methods,710-3 Enclosures,240-C Feeder Taps,240-15 Pan(s) Fixture Wires,402-5 Drip (see Drip Pans) Fuses and Fuseholders,240-E,240-F, Fixture,410-13 240-G,240-H Panelboard Generators,445 4 (s), Art. 384 (see also Haz- Grounded Conductor,not in,240-12 ardour Locations) Heat Generating Equipment,665-7 Damp or Wet Locations,384-17 Induction and Dielectric Heating Equip- Ge ,384-18 ment,665-7,665-15 Gennlosureseral,384-13 Installation,240-A Lighting and Appliance Branch-Circuit, Location,240-B Definition,384-14 Mobile Homes,550-4 Number of Overcu tion,Devices,384-15 Motion-Picture Studios,530-18,530-63 Overcurrent Protection,384-16 Motors,Motor Circuits,Controllers Overcurrent rent Protection,General,384-16 e Arrangement of Switches and Branch Circuits,430-D Capacitors,460-8 Fuses,384-19 Control Circuits,430-72 Service Equipment, 384-16(a), 384-3(c), Cutouts and Relays,Thermal,430-40 230-H 230-K Overloads,430-C Support for bus-Bars,384-3 Over 600 Volts,430-123,430-124 Part-Winding Motors Multiple Fuses and Circuit Breakers in Code Letter Markings,430-7(b) (5) Parallel,240-14 Organs,650-6 Paralleled Outside Branch Circuits and Feeders, Conductors,310-10 730-9 Circuit Breakers and Fuses,240-14 Over 600 Volts,710-C Patching Tables,Motion Picture,530-D 70-450 NATIONAL ELECTRICAL CODE Pendants Protection (Continued) Clothes Closets,410-8(b) Physical Damage (Cont.) Dressing Rooms,520-71 Liquid-tight Flexible Metal Conduit, Flexible Cords,400-3 351-2(b) Pendant Conductors,Lamps,410-22 Metal-Clad Cable, 334-6, 334-12(c), 334-13 Periodic Duty,Definition,Art.100 Multioutlet Assembly 353-2 Permission,Special,Definition,Art.100 Nonmetallic Sheathed Cable,336-6(b) Person,Qualified,Definition,Art.100 Open Wiring,320-7,320-12 Overcurrent Devices,240-16(b) Phase Protection,Elevators,620-53 Resistors and Reactors,470-1 Pipe Electrodes,250-83(c) Rigid Nonmetallic Conduit,347-3(a) Places of Public Assembly,Art.520 Space Heating Systems,424-13 Surface Metal Raceways,352-1 Plate Electrodes,250-83(b) Transformers,450-7(a) Plugging Boxes, Motion-Picture Studios, OF Cable,e 339-3(c) 530-14 Polarity Identification Protection Devices (see Circuit Break- Conductors,310-2(f) ers; Fuses; Overcurrent Protec- Systems and Circuits,Art.200 Lion;Thermal Cutout) Polarization Protective Equipment (see Guarding Lighting Fixtures,Wiring,410-27 and Guards) Poles 40 6 Address Systems,Art. Climbing Space,Conductors,730-14 PublicEmergency Power Supply, 6.700 Conductors, Mechanical, Protection, 230- 32(b),730-20 Public Assembly Places,Art.520 Portable Emergency Lighting Systems,Art.700 Appliance(s),Art.422 Pull Boxes (see also Boxes and Junction Definition,Art.100 Boxes) Equipment Accessibility,370-19 Appliance(s), Tool(s), Double Insula- Construction Specifications,370-C tion,250-45 Sizes, No. 6 and Larger Conductors, Grounding,250-45,250-59 370-18 Grounding Conductor Size, Table 250- Sizes, No. 6 and Smaller Conductors, 95 Handlamps,Construction,410-37 Lamps (see Lamps) Qualified70-6 Person,Definition,Art.100 Stage Equipment,520-E Raceway(s) Switchboards, Theaters, Halls, etc., Bonding,230-63,250-G 520-D Busways,Art.364 Wiring,Motion Picture Studios,530-16 Cellular Concrete Floor,Art.358 Positive-Pressure Ventilation, 500-1, Cellular Metal Floor,Art.356 500-4(b) Conductors in Service,230-43 Power,Emergency Systems,Art.700 ContinuityElectrical,300-10 Power Factor Correction, Capacitors, Mechanical,300-12 460-7 Definition,Art. 100 Power Supply,Mobile Homes,550-3 Electrical Metallic Tubing,Art.348 Emergency Circuits,Independent,700-17 Power Supply,Travel Trailers,551-3 Expansion Joints,300-6(b),347-9 Prefabricated Buildings,Art.390 Fixtures as Raceways,410-26 Pressure Connector,Definition,Art. 100 Flexible Metal Conduit,Art.350 Pressure, Positive, Ventilation, 500-1, Grounding,230-63(b),250-D sections,250-56 5004(b) Induced Currents,300-20 Prevention of Fire Spread Through Inserting Conductor,300-18 Fire Partitions,300-21 Insulation Bushings,300-16,373-6(b) Projectors,Motion Picture,Art.540 Liquidtight Metal Conduit,Art.351 Metal-Trough,Sound Recording,640-4 Protection Combustible Material,Appliances,422-10 Number of Conductors,300-17Rigid Metal Conduit,Art.346 Corrosion, Secured,300.11 Aluminum-Sheathed Cable,331-2 Service(see Service Raceways) Conductors,Metallic Signal and Power Circuits,Low-Energy Electricale Tubing,348-1 Different Systems,725-16 MGeneral Equipment,300-5 Separations of other Conductors,725-42 Rigid Cable,l Co Sizes,725-13 d Metal Raceways,e 346-1354 Storage Battery Rooms,480-7 Underfloor 354-2 Structural Raceways,Art.357 Liv Pa,Motors,4 44-15 6,450-7(c),(d) Supporting Conductors,Vertical,300-19 Livee Parts,110-17, Temperatures,300-6 Motor-Running Overcurrent,430-C Underfloor,Art.354 Physic Overcurrent (see (Injury), Overcurrent Protection) Underground, Cable Under Building, Physical Damage(Injur 300-7 Busways,364-2 Wireways,Art.362 Capacitors,460-3 Wiring,Outside,730-23 Conductors,alMetallic Tubing, Radiographic Equipment,660-12(a) Electrical Metallic 348-1 INDEX 70-451 Radio,Television Equipment,Art.810 Remote-Control,etc. (Continued) Radio, Television Distribution Equip., Class 2 System Art.820 Installation,725-E Railway Limits,Voltage and Current,725-31 Conductors,Power and Light, 110-19 Overcurrent Protection,Mounting,725- Track,As a Ground,250-85 32 Raintight,Definition,Art. 100 Transformer Leads,725-34 Ranges,422-17,422-23 Classifications rmer Rating,725-33 Branch Circuits Class 1,725-3(a) Calculation of Load,Table 220-5 Class 2,725-3(b) Conductors,210-19 Communication Cables,725-7 Maximum Load,210-23 Low-energy Power Circuits, Defined, Feeders,Calculation of Load,220-4 725-4 Grounding Method,250-60 Low-Voltage Power Circuits, Defined, Loads,Demand,Table 220-5 725-5 Receptacles,210-21(b) (see also Cooking Overcurrent Protection,725-22 Units) (see also Ovens) Transformer Ratings,725-23 Reactors (see Resistors and Reactors) Motors,430-F Readily Accessible,Definition,Art. 100 Sid Metal Conduit,ol Dev Art., 34725-6 Rigid Metal 346 Reaming, Ends of Rigid Metal Conduits, Residential Occupancies (see Dwell- 346-7 ings) Receptacle (Convenience Outlet), Resistance Def.,Art. 100 Conductors,Copper,Aluminum,Table 8, Receptacle Outlet,Definition,Art.100 Chap.9 Receptacles, 410-K Convaron,General rTovis 9,Chap-9 Branch Circuits,210-21,210-22 Welders,Insulation, Provisions, 110-20 Disconnecting Means,422-22 Resistance-to-Ground, Electrodes, 250- Faceplates,410-52(b) 84 Grounding Type,250-74,410-55 Hazardous Locations, 501-12, 502-13, Resistors and Reactors,Art.470 503-11 Combustible Material,on,near, 470-3 Less Than 50 Volts,720-6,720-7 Conductor Insulation,470-7 Contacts,Fixed,Movable,470-4 Minimum Ratings,410-52(a) Incandescent Lamps as Resistors,470-8 Mobile Homes,550-6 Nongrounding types, Replacements, 210- Location,470-1 21(b) Mounting,470-6 Outlets, Where Required, Dwellings, Reactor Materials,470-5 210-22(b) Space Separation,470-2 Terminals,Identification,200-10 Rheostats, Construction Specifications, Theaters,Halls,etc.,520-23,520-45 430-82(c) Travel Trailers,551-6 Rigid Metal Conduit,Art.346 Recessed Lighting Fixtures Bends As raceways,410-26 How Made,346-10 Clearances,410-64 Number,346-11 Construction,410-N Bushings, 346-8 Temperatures,410-63 Cinder Fill,346-3 Wiring,410-64 Construction Specifications,346-B Couplings and Connectors,346-9 Recording Systems,Art.640Exansion Refrigeration Compressor Motors and Minimum Size,t346-a6(b) Controls,430-6,430-7,430-83,430- Number of Conductors, ( 110 b New Work,346-6(a) Definition,Art.(1100 Nipples,Note Table 1,Chap.9 Regulators, Mercury Vapor Lamps, Rewiring, 346-6(b) 410-50 Reaming Ends,346-7 Relays Supports,346-12,Table 346-12 1 Reverse-Current,Transformers,450-5(b) Use,Locations,3oc- Thermal, Motor Overcurrent Protection, Wet mtalc4C 4 430-40 Rigid Nonmetallic Conduit,Art.347 Remote-Control, Low-EnergyPower, Bends and Signal Circuits How Made,347-131 Class 1 System Number,347- 4 Circuits Beyond Buildin 725-20 Boxes and Fittings,370-4,370-7(c) Conductors g' Bushings,347-12 Different 725-16 Construction Specifications,347-16 Different t Systems,e4 Description,347-1 Expansion Joints, 347-9,300-6(b) Number in Raceways,725-15 -6 Overcurrent Protection,725-18 Minimumin Size,725-13 Number Size,duct Grounding,725-21 Number of Conductors, 11(a) Location,Overcurrent Devices,725-19 New Work,3 7-11(b) Mechanical Protection,725-17 pot,Rewiring,347-8,Table Wiring Methods,725-11 Trimming s 347-8 Trimming Ends,347-5 70-452 NATIONAL ELECTRICAL CODE Rigid Nonmetallic Conduit (Continued) Service-Entrance Cond. (Continued) Use permitted,347-2 Disconnecting Means,230-.1 Use prohibited,347-3 Insulation,230-40 Rod Electrodes,250-83(c) Mechanical Protection,230-46 Outside of Building,230-45 - Room Air Conditioners Over 600V,230-L Branch Circuits,422-42 Overcurrent Protection,230-90,230-106 Defined,430-53(d) Size,230-41 Grounding,422-41 Service Head,230-51 Nameplate Rating, Branch Circuit Re- Splices,230-42 quirements,430-53(d) Underground,230-D Rosettes,410-L Wiring Methods,230-44 Overcurrent Protection,240-17(d) Service Entrance Equipment (Dis- Running Protection, Motors and Con- connecting Means and Overcur- ductors,430-C rent Protection) RunningThreads,346-9(b) Definition,Art. 100 Disconnecting Means,230-3 Screw-Shells Approved Type,230-70(c) Identification,Polarity,200-8,410-27 Connections ahead of,230-73 Terminals,200-10 Connections to Terminals,230-72 Lampholders,410-G Disconnection of Grounded Conduc- Sealable Equipment, Definition, Art. tExternallyo,23 (i) Operable, 0230-70(e) 100230-70(f) Indicating, Sealed Hermetic-Type Compressor Location,230-70(b) Controller Rating,430-83,Exc.3 Described,430-2,Art. 100 Multiple Occupancy Buildings, 230- 70(b) Nameplate,4307(c) Over 600V,230-103 Running Protection,430-C Rating,230-71 Size of Conductor,430-6(b) Safeguard,Emergency Supply,230-74 Sealing, Conduit Systems (see also Haz- Simultaneous Openings,230-70(h) ardous Locations) Six Switch Rule,230-70(g) Temperature Changes,300-6(a) Two or More Buildings, Single Man- Underground Services,230-33 agement,230-76 Secondary Ties,Transformers,450-5 Grounding, Bonding, Guarding, 230-H, 250-71,250-72 Service(s),Art.230 Overcurrent Protection,230-K Definition,Art.100 Location,230-91,230-92 Emergency Systems,700-9 Over 600V,230-106 Farm,220-4(m) Relative Location,230-94 Insulation,Size,230-B Specific Circuits,230-93 Lateral,Def.,Art. 100 Two or More Buildings, Single Man- Number,230-2 agement,230-90(c) Over 600V,230-L Ungrounded Conductors,230-90(a) Supply to Building Through Another, Panelboards,as,384-B 230-3 Service Raceways Underground,230-D Arranged to Drain, Raintight, 230-52, Service Cables,Art.338 230-101(g) Buildings,230-50 Conductors,Others permitted in,230-43 Definition,Art. 100 Definition,Art.100 230-63(b) (c), Installation,Art.338 Grounding and Bonding, Mechanical Protection,230-46 250-71,250-72 Service Head,230-51 Service Head,230-51 Terminating,Service Equipment,230-53 Terminating at Service Equipment, 230- Underground,230-D,310-6 53 Underground,230-D Service Drops Clearance, Over Roofs, from Ground, Service Stations, Gasoline (see Hazard- Building Openings,230-24 ous Locations) Connections,Service Head,230-51 Definition,Art.100 Shielding (see Guarding and Guards) Means of Attachment,230-27 Short-Time Duty,Definition,Art. 100 Minimum Size,230-23 Show Cases,Wall Cases,410-23(c) Number,230-2,230-21 Point of Attachment,230-26 Show Window(s) Supports Over Buildings,230-25 Cords,Flexible,400-6 Termination,230-24,230-26,230-51 Definition,Art.100 Lighting Fixtures,410-7 Service Entrance Cable,Art.338 Branch Circuits,220-2 Definition,338-1 Feeders,220-4 Installation Methods,338-4 Receptacles,Floor,410-53 Marking,338-5 Signs,Outline Lighting,600-34(e) Use Buried Conductors,310-6 Sidelights, Borders and Proscenium, 5 - Branch Circuits or Feeders,338-3 Service-Entrance Conductors, 338-2, Sign(s)Art.230 Electric,Definition,Art.100 Service-Entrance Conductors,230-E Discharge, Lighting, Electric, 410-P, Definition,Art.100 410-Q INDEX 70-453 Sign(s) (Continued) Stand-By Gen.Systems(Continued) Grounding,250-4-3(f) Approval,750-3 Outline Lighting,Art.600 Capacity,750-6 Size of Conductors(see Conductors) Control and Transfer,750-7 Signal Circuit(s) Generator,750-5 Definition,Art. 100 Protection,750-8 Installation Requirements,Art.725 Tests,750-4 Smoothing Irons,422-13 Wiring,750-9 Snap Switches Steel Siding (see Metal Siding) Accessibility,Grouping,380-8 Storage Batteries,Art.480 Definition,Art. 100 under Switches Aircraft Hangars,513-9 Motors,430-83,430-109 Battery Rooms,480-7 Panelboards,384-16,384-19 Emergency Systems,700-7 Ratings Garages,511-7 Inductive Loads,380-14(c) Insulation Noninductive Loads,380-14(a) Over 250V,480-5 Tungsten-Filament Loads,380-14 Not over 250V,480-4 Residential Garages, Outbuildings, Sup- Racks and Trays,480-6 ply Conductors,230-76 Sound Recording Equipment, 640-9, 640- Signs,600-2 10 Solderless (Pressure) Connector, Defini- Structural Raceways,Art.357 tion,Art. 100 Definitions,357-1 Sound Recording Installation,357-A Equipment,Art.640 Construction,357-B Motion Picture Projectors,540-50 Use,357-2 Theaters,Assembly Halls,etc.,520-3 Substations, Motion Picture Studios, Space 530-F Cabinets, Cutout Boxes, 373-7, 373-9, 373-11 Supply Stations, Overcurrent Protection, Lightning Rods, Conductor Enclosures, Feeders,240-9 Equipment,250-34,250-46 Support(s) (see Articles on wiring and Outside Branch Circuits,Feeders,730-14 equip.involved) Over 600 Volts,Separation, 230-101,710- 33 Suppressors,Radio Noise,810-4 Service Entrance Conductors,230-47,230- Surface Metal Raceway,Art.352 48 Surge Protection, 502-3 (see also Light- Working Space About Electrical Equip., 110-16 ping Protection) Space Heating, Fixed Indoor, 424-13, Swimming Pools,Art.680 424-39 Approval of Equipment,680-2 Attachment-Plug Receptacles, Location, Spacing Between Bare Metal Parts, Table 384-26 680-6 Special Permission,Definition,Art. 100 Forming Shell,Definition,680-4(d) Grounding,Bonding,680-7,680-8 Splices and Taps Junction Boxes, Transformer Enclosures, Antennas,810-14 680-5 Auxiliary Gutters,374-8 Overhead Wiring,Clearances,680-9 Bare-Conductor Feeders,328-3 Underwater Lighting Fixtures,680-4 Cable Heating,424-40 Switch(es), Art. 380 (see also Hazardous Cellular Concrete Floor Raceways, 358- Locations) 10 Accessibility and Grouping,380-8 Cellular Metal Floor Raceways,356-6 AC General Use Snap Switch,Def.,Art. Concealed Knob and Tube,324-11 100 Continuous Rigid Cable Supports, 318- AC-DC Snap Switch,Def.,Art.100 4(j) Appliances,422-24 Deicing,Snow-Melting,424-73 Disconnecting Means Fixtures,410-25 Appliances,422-D Flexible Cords,400-5 Motors,Controllers,430-86,430-H General Provisions,110-15 Services,230-70 Hazardous Locations,501-5,502-4,503-3 Emergency Systems,700-D Nonmetallic Extensions,342-5 Foot Open Wiring,320-5(a-2) Heat Generating Equipment,665-12(b) Space Heating Cables,424-40 X-ray Equipment,660-13 Structural Raceways,357-7 General Use,Art.380 Underfloor Raceways,354-6 Definition,Art.100 Wireways,362-6 Identification, 110-22 Stage Equipment Isolating Fixed, Theaters, Assembly Halls, etc., Definition,Art. 100 520-C Lightning Arresters,280-25 Portable,Theaters,Halls,etc.,520-E Motors Over 50 HP,430-109(d) Services Over 600 Volts,230.104 Stage Motion Picture,530-B Switchboard,520-B,520-D Knife,Art.380 Limit Stand-By Power Generation Systems, Cranes and Hoists,610-34 Art.750 (see also Emergency Sys- Elevators,620-51 tems,Art.700) Manually Operable,Art.380,430-86 70-454 NATIONAL ELECTRICAL CODE Switch(es) (Continued) Tables (Continued) Motor Controllers,430-G Conductors (Cont.) Definition,430-81(a) Grounding,Size, Motor Circuit,Definition,Art.100 For grounded Systems, Table 250-94 Panelboards,384-16(b),384-19 (a)grounding Service,230-J ForInterior Equipment, Signs,Outline Lighting,600-2,600-35Table 250-95 Snap,Art.380 For ungrounded Systems,250-94(b) Theaters, Assembly Halls, Dressing Insulations,Table 310-2(b) , Rooms,etc.,520-73 Number in Box, Time,Connection,230-73,230-94 Cu., in. Dimensions for Combina- Unit, Appliances, 422-24 tions,Table 370-6(b) Switchboard(s),Art.384 Deep Boxes,Table 370-6(a-1) Shallow Boxes,Table 370-6(a-2) Clearances Over 600V to 5000V BackroCeiling, 8 384-7 Asbestos and Varnished Cambric, From orCovering, Single-Conductors, Table 310-2(i) Conductor 384-9 Construction Specifications,384-C Rubber-covered,Table 310-2(i) (1) Grounding Ignitible a Frames,384-114-1,Near,384-6 Shielding, Rubber-Insulated Conduc- Grounding s3tors,Table 710-5 Intruments, -17 Varnished Cambric multiple-Con- Illumination,Guarding Live0-16( 100.17 ductor cables,Table 310-2(i) (3) Location, 8110-16(e) Varnished Cambric, single-conduc- Portable, Sheater tors,Table 310-2(i) (2) SuSupport,bus-bars,Stages,ou tors, Voltage Marking,310-2(e) (5) Wet Locations, conductors,384-3 Properties,Table 8,Chap.9 or king Spaces,Sabo Support,Vertical Raceways,300-19(a) Working about,110-16 Conduit or Tubing Switchgear, Metal-Enclosed, 230-101(h), Combination of Conductors, percent 230-106 Area Fill,Table 3,Chap.9 Dimensions,Table 4,Chap.9 Tables Flexible Metal (143 in.), Table 350-3 Ampacities Liquidtight Flexible Metal,351-4 Crane and Hoist Motor Conductors, Number of Conductors Permitted, Table 610-14(a) Combinations, Tables 3 to 8, Chap. Fixture Wire,Table 402-4 9,See 346-6,and 347-11 Flexible Cord,Table 400-9(b) Lead-Covered,Table 2,Chap.9 General Conductors, New Work,Table 1,Chap.9 Aluminum, in Raceways or Cables, Rewiring,Table lA,Chap.9 310-14 Aluminum,Single Conductor in Free Radius of Bends,Table 346-10(a),346- 10(b) Air,Table 310-15 Supports Copper, in Raceways or Cables, Rigid Metal Conduit,Table 346-12 Table 310-12 Copper,Single Conductor in free air, Rigid Nonmetallic Conduit, Table347-8 Table 310-13 Continuous Rigid Cable Supports, Correction Facto31rs,Note 15 to Tables Table 318-6(a) Simplified Wiring,T 310-12 thru Table 310-21 15General Lighting Unit Loads by Occu- Ambient panties,Table 220-2(a) Ambient Temperatures for, Table 3 Gutters, Sheet-Metal Thickness, Table Wound-rotor 374-9(d)or Secondaries,Table 430- Household Clothes Dryers, Demand 23(c)Bare (Swit Parts, an Loads,Table 220-6(b) dcings Between Household Ranges and Similar Cooking Tablet chboards 384 26 a (Swind Panelboards) Appliances, Demand Loads, TableBranch-Circuit Requirements, Table 210- 220-5Live Parts,Separation 25 Over 600V Calculation of Feeder Loads by Occu- O pancies,Table 220-4(a) Air Separation, Indoors, Table 710- 33 Cooking Appliances Elevation,710-34(f) Commercial,220.5 220-6(a) Working Space,710-34(a) Conductor or( Hd Working Clearances,Table 110-16(a) Motors Application,etio Table Bending Deflection, Min. Bending Space, in Full-Load Currents Cabinets, Cutout Boxes, Table AC AC SinhasPhase,Table able 0 Dimensioionss 430-148 ins AC 2-Phase,430-149 Asbestos, DC le 47 Varnished Cambric, Table Locked Current Conversion,-1 7 Rotor Chap.9 Table 430-151 Rubber, Ther Table 6,Chap.9 Rubber, Thermoplastic-Covered, Ta- Locked Rotor, Code Letters, Table ble 5,Chap.9 430-7(b) DC to AC (60 Cycle) Resistance Con- Maximum Rating or Setting,Br.Cir. version,Table 9,Chap.9 Protective Devices,Tables 430-152, Fixture Wires,Types,Table 402-6 430-153 Flexible Cords,Types,Table 400-11 Number and Location, Overcurrent INDEX 70-455 Tables (Continued) Thermally Protected (Thermal Pro- Units,Table 430-37 Section),Marking on Motors,430- Terminal Housing Tables,430-12(b), 7(a) (b) 430-12(c) (1),430-12(c) (2) Three Running Overcurrent Units, mo- Multifamily Dwellings, tors,Table 430-37,Note Common Demand Factors,Table 220-9 Optional Load Calculations, One-family Tools, Metal Working Machine, Art. Residences,Table 220-7 670 Radio and TV Equipment,Antenna Sizes Tools, Motor Operated, Grounding and Amateur Stations,Table 810-52 Double Insulation, 250-45(c), 250- Receiving Stations,Table 810-16(a) 45(d) Tamperability Transformers, Transformer Vaults, Art. Air Circuit Breakers,240-25(e) 450 (see also Hazardous Loca- Type S Fuses,240-22(d) Lions) Taps (see also Splices and Taps) Arc Welders,630-B Branch-Circuit Capacitors,460-5 Cooking Appliances, 210-19(c), Exc. 1 Installation,Art.450 Individual Fixtures or Lampholders, X-ray Equipment,660-D 210-19(c),Exc.2(b) Electric Discharge Lighting Systems Busways,364-11,Exc. 1 1000 Volts or Less,410-P Feeders More than 1000 Volts,410-Q 10-ft.Rule,240-15,Exc.5 Instrument,Grounding,250-L 25-ft.Rule,240-15,Exc.6 Connections at Services,230-73 Motor,430-59 Isolating, in Anesthetizing Locations, Service-entrance Conductors,230-42 517-6(a) Systems,Art.800 Power and Signal Circuits, Remote-con- Telegraphtrol,725-23,725-33,725-41,725-42 Telephone Exchanges, Circuit Load, Remote-Control Circuits, for, 430-74(b), 220-2,Exc.4 725-23,725-33 Telephone Systems,Art.800 Signs and Outline Lighting,600-32 Television,Radio Equipment,Art.810 Two-winding, Underwater Lighting Transformers,680-4(h) Television Studios,Art.520,Art.530 Vaults,450-C Television & Radio Distribution Sys- X-ray Equipment,660-D tems, Community Antenna, Art. Transmitting Stations, Radio and Tele- 820 vision,810-C Temperature Limitation, Conductors in Travel Trailers,Art.551 Outlet Boxes for Fixtures,410-11 Branch Circuits,551-5 Terminal Housing,430-145 Branch-Circuit Protection,551-4(b) Terminals Definition,551-2 Connections to,General,110-14,250-113 Disconnecting Means,751-4(a) Electric Discharge Tubing, Signs, Outline Grounding,xed Appliances,-9551-7(a) Lighting,600-34 Laelig, c rig Identification LLabeling,electrical entrance,551 4(c) 51-7(b) Motors,Controllers,430-9 Neutral ontu ct s,551 9( Polarity,200-9,200-10 Neutral Conductors,551-9(a) Power Supply,551-3 Tests Receptacle Outlets,Types,551-6 Deicing and Snow Melting Systems,424- Testing,551-10 80 Trays,Storage Batteries,480-6(b) Emergency Systems,700-4 TubingConduit) Insulation Resistance, (see also General,110-20 Electric Discharge, Sign and Outline Mineral-Insulated Cable,330-10 Lighting,600-33,600-34 Space-Heating Cables,424-45 Electrical Metallic,Art.348 Mobile Homes,550-10 TV&Radio,Arts.810 and 820 Travel Trailers,551-10 Underfloor Raceways,Art.354 Television&Radio Conductors, Equipment,Art.810 Number,354-5 Distribution Systems,Art.820 Size,354-4 Theaters Connections to Cabinets, Wall Outlets, Arc Lamps,410-51 354-15 adring Assembly Halls,Art.520 D ,354-3 ,3 Emergency Lighting Systems,Art.700 DeadD Ends, Outlets, Grounding,4 Electrical Fixed Equip., 250- Fittingsiniat Angles,gles, 5,354-12 354-7 at Inserts,354-14 Therapeutic Equipment, Inductive and Junction Boxes,354-13 Dielectric Heat Generating,665-E Low Points,Avoid,354-11 Thermal Markers,Where Required,354-9 Cutout,Definition,Art.100 Splices and Taps,Junction Boxes,354-6 Disconnecting Means,240-18 Use,354-2 Devices Underground Feeder and Branch-Cir- Motors,430-40 cuit Cable(Type UF),Art.339 Overcurrent Protection,240-8 Description and Marking,339-1 Protection,Definition,Art.100 Overcurrent Protection,339-4 Protector,Definition,Art.100 Use,330-3 70-456 NATIONAL ELECTRICAL CODE Underground Services,230-D Warning Signs(Labels),At Equipment Underground Wiring, (see also Hazard- Induction and Dielectric Heating,665-25 ous Locations) Locked Room or Enclosure with Live Buried Conductors,Types USE,UF, 310- Parts over 600V,710-34(c) 6,339-3 Services over 600V,230-102 Conductor Types in Raceways,310-5 Transformers,450-7(d) Direct Burial in Earth,310-6 Water Heaters,Protection,422-10 Over 600V,710-3(b) Water Pipe Rigid Metal Conduit,346-1 As Grounding Electrode,250-81 Rigid Nonmetallic Conduit,347-2 Connections,250-112(a),250-113 Services,230-30 Grounding Conductor,250-112,250-113 Wet Locations,310-5 Resistance,250-84 Underplaster Extensions,Art.344 Watertight,Definition,Art.100 Boxes and Fittings,344-3 Weatherproof,Definition,Art.100 Extension to Another Floor,344-5 p Installation,344-4 Welders,Electric,Art.630 Materials,344-2 Motor-Generator Arc,630-C Use,344-1 Resistance,630-D Unit Equipments, Emergency Lighting, Transformer Arc,630-B 700-22 Wet Locations (see Damp or Wet Loca- Unused Openings tions) Boxes and Fittings,370-8 Conductors,Types,310-5 Cabinets and Cutout Boxes,373-4 Definition,Art.100 Electrical Metllic 348 Utilization Equipment,Def.,Art.100 Enameled Equipm ntb300-5(a) Vapors, Flammable (see Hazardous Lo- Mounting of Equipment,300-5(c) cations) Rigid Metal Conduit,346-4 Varying,Duty,Definition,Art.100 Rigid Nonmetallic Conduit,347-2 Vaults Switchboards,384-5 Capacitors,460-2 Switches,380-4 Film Storage,530-E Window,Show(see Show Windows) Service Over 600 Volts,230-106,710-31 Wire in Co to Footings, Electrodes, Transformers,450-C 250-83(a) Vehicle,Electric,Charging,511-8 Wire(s) (see Conductors; Cords; Fixture Ventilated,Definition,Art.100 Wire) Ventilating Ducts,Wiring,300-21,300-22 Wireways,Art.362 I Ventilating Piping for Motors,etc. Conductors Hazardous Locations, Maximum Size,362-4 Class II Installations,502-9 Number,362-5 Class III Installations,503-7 Dead Ends,362-9 Definition,362-1 Ventilation Extensions,362-10 f Battery Rooms,480-7(b) Extensions thru Walls,362-8 Generators, 445-1 (see also Hazardous Marking,362-11 Locations) Splices and Taps,362-6 Motion Picture Projectors,540-18 Supports,362-7 Motors,430-14(a),430-16 Use,362-2 Positive-Pressure,500-1,500-4(b) Wiring 450-44,450-45 Methods, Types (see Table of Viewing Tables,Motion Picture,530-D Contents) Voltage and Volts Wiring Methods, Gen'l Requirements, Branch Circuits,Limits,210-6 Art. 300 (see also Hazardous Circuit,Definition,Art.100 Locations) Drop Ducts,300-21,200-22 Branch Circuits,210-6(c) Mobile Homes,550-8 Feeders,215-3 Temporary,300-23 , Electric Discharge Lighting, under 1000 Theaters and Assembly Halls,520-4 Volts, 410-P; Over 1000 Volts, Travel Trailers,551-8 410-Q Working Space General Provisions,110-5 About Electrical Equipment, Horizontal Ground,to,Definition,Art.100 Dimensions, Clear Spaces, Eleva- Less than 50, Circuits and Equip., Art. loon of Equipment, General, 110- 720 Limitations, Elevators, Dumbwaiters, Es- Adjacent to Live Parts,Circuits over 600 calators,Moving Walks,620-2 Volts,710-33,710-34 Over 600V Circuits and Equip.,Art.710 Workmanlike Installation,110-12 Swimming Pool Underwater Lighting Equipment,Art.660 , X-Ray Fixtures,680-4(b),680-4(g) Control,66mB Wiring Methods,300-2 Guarding and Grounding,660-E Wall or Show Cases,Conductors,410-23 Industrial,660-C Wall-Mounted Ovens (see Ovens, Wall- Installation,660-A Mounted, Ranges, Cooking Units) Transformers and Capacitors,660-D 70-457 APPENDIX Rules of Procedure for the NFPA Electrical Section and the National Electrical Code Committee Adopted by the NFPA Board of Directors on January 23, 1964 and Amended June 28,1967 The National Fire Protection Association Part A—Rules of Procedure for the is sponsor of the National Electrical Code NFPA Electrical Section (USAS C1-1968, NFPA No. 70-1968) and Part B—Rules of Procedure for the other standards covering the safe use of National Electrical Code Committee electricity. In 1948, the NFPA Board of Directors authorized an Electrical Section Part C—Rules of Procedure—Tenta- of NFPA. The National Electrical Code tive Interim Amendments to the National Committee consists of a Correlating Com- Electrical Code mittee and a number of Code-Making Panels. The Rules of Procedure for these Part D—Interpretation Procedure of the organizations consist of: National Electrical Code Committee PART A—RULES OF PROCEDURE FOR THE NFPA ELECTRICAL SECTION Section 10.General 10. There are no dues or fees beyond proposals for revisions or additions to the regular NFPA membership dues. these standards may be discussed. 11. The Section provides particular op- 12. Bulletins and reports on matters af- fecting the work of NFPA Technical Com- portunity for Section members to become mittees in this field are made available to informed and contribute to the development members of the Section as the need indi- of NFPA electrical standards. It sponsors, cates, through its Chairman, Secretary, or for this purpose, open meetings where the NFPA Executive Office. Section 20.Activities,Membership,Meetings,Officers 21. Activities,programs, and procedures the Section on the work of that Committee not covered in these Rules for the NFPA and may take such other steps as he con- Electrical Section shall be in accordance siders desirable to keep the Section in- with the Regulations for NFPA Sections. formed on Committee matters. The Elec- 22. Membership in the NFPA Electrical trical Section may vote to request further Section is open to any Associate Member consideration of a specific item by the Cor- of the Association and up to four individ- relating Committee. Reports from other uals designated by an Organization Mem- existing NFPA Technical Committees may ber. To become a member of the NFPA be presented to the Annual Meeting of the Electrical Section, it is necessary to file a Section when such action is considered ap- special application form with the NFPA propriate by the officers of the Electrical Executive Office or the Electrical Section Section. Secretary(forms available on request). 27. The Section may recommend to the 23. The Section shall meet at least an- NFPA Board of Directors the establish- nually at the time and place of the National ment of other Technical Committees useful Fire Protection Association Annual Meet- in promoting its objectives, other than as ing (unless omitted on the request of the covered by the scope of the National Elec- Section with the consent of the NFPA An- trical Code. These Committees, if author- nual Meeting Program Committee). Other ized,shall be organized and operated under meetings of the Section may be held at the NFPA Regulations Governing Technical times and places it may select. Committees or under such special rules as 24. The Chairman and Secretary of the may be authorized by the NFPA Board of National Electrical Code Committee shall Directors.The Chairman of any such Com- be the Chairman and Secretary, respec- mittee so established shall follow the pro- tively, of the Electrical Section.The Secre- cedures outlined in Paragraph 26. tary of the Section shall keep a record of 28. Reports of Technical Committees the membership, notify its members of Sec- covering areasortthat of are currently tion meetings and keep members rofe theo the National Electrical Code, shall becovered sub- them.Section informed on matters of interest to them. mitted through the Correlating Committee 25. In order to transact business at any of the National Electrical Code Committee meeting of the Section, there shall be at when so directed by the NFPA Board of least fifty members of the Section present. Directors. (See Paragraphs 54 and 55 of the Robert's Rules of Order, Revised, shall NFPA Regulations Governing Technical govern the transactions of business at all Committees.) meetings. 29. The Section does not have authority 26. The Chairman of the National Elec- to commit the Association nor does mem- trical Code Committee (or his representa- bership in the Section commit any individ- tive) shall report to the Annual Meeting of ual or organization to a course of action. 70-458 APPENDIX—RULES OF PROCEDURE PART B—RULES OF PROCEDURE FOR THE NATIONAL ELECTRICAL CODE COMMITTEE Section 30.General 31. The National Electrical Code Corn- nounced to the public following issuance mittee shall consist of of each successive edition. a. A Correlating Committee,and b. Processing proposals for Tentative b. A number of Code-Making Panels. Interim Amendments of the current edition of the National Electrical Code in accord- ance The functions of the National Elec- with the Rules of Procedure—Tenta- 32.trical Code Committee shall be established Electricaltive Interim CodeA(see Par is ofo the National trical by the NFPA Board of Directors and shall Inge Part C these the Rules). cur- include c. Interpreting provisions of rent edition of the National Electrical Code a. Developing periodically revisions of in accordance with the Interpretation Pro- the National Electrical Code (USAS Cl, cedure of the National Electrical Code NFPA No. 70) on a schedule to be an- Committee(see Part D of these Rules). Section 40.Membership 41. The Chairman of the National Elec- individuals to serve on the Code-Making trical Code Committee shall be the Chair- Panels, submitting their recommendations man of the Correlating Committee of the to the Chairman of the Correlating Coin- National Electrical Code Committee and mittee in such form as he may request. Al- shall be appointed by the Board of Direc- ternates for such individuals may be nomi- tors of the National Fire Protection Asso- nated when conditions warrant. Individuals ciation. (See also Paragraph 24 of Part A having an interest in only a portion of the —Rules of Procedure for the NFPA Elec- scope of the work of a particular Panel trical Section.) may be nominated to limited membership 42. Subject to approval by the Board of covering their special field of interest. All Directors of the National Fire Protection appointments of members and alternates Association, the NFPA Electrical Field shall be made by the Chairman of the Cor- Engineer serves as the Secretary of the Na- relating Committee acting with the advice tional Electrical Code Committee and as and consent of the members of the Cor- the Secretary of the Correlating Committee relating Committee acting in consideration of the National Electrical Code Committee. of the items noted in Paragraph 46. He shall serve in this capacity as a non- 45. The Chairman of the Correlating voting member, except as noted in Para- Committee shall a of graphs 112 and 121.b. (See also Paragraph ppoint the Chairman 24 of Part A—Rules of Procedure for the each Code-Making Panel, acting with the NFPA Electrical Section.) advice and consent of the members of the 43. Other members of the Correlating Correlating Committee. Committee shall also be appointed by the 46. All appointments to the Correlating NFPA Board of Directors acting on recom- Committee and to the Code-Making Panels mendations of the Chairman of the Corn- shall be based on the technical competence mittee. Alternates for such individuals may of the individuals selected. Proper balance be nominated when conditions warrant.The of all interests concerned shall be made membership of the Correlating Committee within the desired limits of effective com- shall be restricted to nine voting members mittee size and in accordance with the ob- (Secretary and other nonvoting members jectives of the National Fire Protection excluded). Association and in accordance with proce- 44. Groups concerned with various Ar- dures of the United States of America tides of the Code may nominate qualified Standards Institute. Section 50.Functions of the Correlating Committee 51. The Correlating Committee shall Making Panels that recommend changes or have the following functions: additions to the National Electrical Code; a. Determine the steps and schedule determine whether a consensus exists war- for each revised edition of the National ranting acceptance of such recommended Electrical Code, subject to approval by the changes or additions; and determine Board of Directors of the National Fire whether the proposals shall be approved Protection Association. for further processing, rejected, returned b. Organize the Code-Making Panels to the appropriate Code-Making Panel or in such a manner as to effectively cover Panels for further study, or submitted to a the technical objectives of the National Technical Subcommittee for further con- Electrical Code as set forth in Article 90 of sideration. Action to recommend amend- the Code. The number of Code-Making ments to the National Electrical Code for Panels and the Code Articles assigned to action at an NFPA Annual Meeting shall each shall be determined by the Correlating require at least seven affirmative votes by Committee. the Correlating Committee provided that, if c. Appoint, as needed, Technical Sub- any absent member subsequently registers committees to assist in developing the Na- disapproval, the action must be reaffirmed tional Electrical Code and such other by letter ballot or at a later meeting of the Codes, Standards or Manuals which the Committee. NFPA Board of Directors recommends be e. Review all reports of other tech- handled by the National Electrical Code nical committees of the Electrical Section Committee. that normally submit such reports in ac- d. Review all reports by the Code- cordance with Paragraph 28. APPENDIX-RULES OF PROCEDURE 70-459 f. Establish that no conflict exists and proval of the Board of Directors of the satisfactory correlation is achieved between National Fire Protection Association (see recommendations of the various Code-Mak- Part C of these Rules). ing Panels and with other NFPA Technical i. Establish an Interpretation Proce- Committees having an interest in the sub- duce for the National Electrical Code, jects under consideration. subject to approval of the Board of Direc- g. Report to the Director of Techni- tors of the National Fire Protection Asso- cal Services of the National Fire Protection ciation(see Part D of these Rules). Association any proposals for revisions or additions to the National Electrical Code. 52. Meetings of the Correlating Com- h. Determine the Rules of Procedure mittee shall be held at the call of the for Tentative Interim Amendments of the Chairman. Seven members shall constitute National Electrical Code, subject to ap- a quorum. Section 60.Functions of the Code-Making Panels 61. A Code-Making Panel shall consider ing Committee to determine if such a valid and report its recommendations on all consensus exists.) matters referred to it by any of the methods 63. When reporting recommendations, outlined in Paragraph 91 of these Rules. the vote of each member of a Panel shall be recorded with the Correlating Com- 62. The program of each Code-Making mittee by the Chairman of the Panel. This Panel shall be directed by its Chairman report shall identify affirmative voters, as seems most appropriate for the efficient negative voters,those abstaining, and those disposition of its business subject to the whose ballots have not been returned, to- approval of the Correlating Committee. gether with the reasons for negative votes Code-Making Panel Meeting dates and and abstentions. places shall be coordinated through the 64. Each Panel shall report the consid- Secretary of the National Electrical Code eration given to each proposal for Code Committee to avoid conflicts of meetings changes that have been referred to it, and to assure that the established schedule whether it recommends a specific action, is adhered to. Within this framework, each rejects the proposal, votes to retain the Code-Making Panel may develop its own item on its docket for further study, refers working methods consistent with the ob- the proposal to another Code-Making jectives of the Association and the National Panel,or takes any other course of action. Electrical Code Committee as herein estab- 65. The various Panels are authorized to lished. A guide outline of "Manual of solicit from individuals or groups concerned Procedure for Code-Making Panels" is with the scope of an Article such technical available from the Secretary of the Na- assistance and cooperation as will contrib- tional Electrical Code Committee.Any pro- ute to their work. The Chairman of the posed revision of the National Electrical National Electrical Code Committee should Code recommended by a Panel shall repre- be kept advised of such actions and those sent, to a major degree, the consensus of cooperating in this manner shall be men- the membership substantially concerned. (It tioned in the report of the Panel to the shall be the responsibility of the Correlat- Correlating Committee. Section 70.Technical Subcommittees 71. Technical Subcommittees to consider 72. Those invited to serve on a Tech- any designated topic shall be appointed by nical Subcommittee shall be chosen on the Chairman of the National Electrical the basis of familiarity with the problem or Code Committee. Forming such Technical topic and need not be members of the Na- Subcommittees may result from a recom- tional Electrical Code Committee. mendation of the Correlating Committee or 73. Any report from a Technical Sub- a request of a Code-Making Panel follow- committee, if containing proposals for ing approval by the Correlating Committee. changes or additions to the National Elec- Where the topic to be considered is wholly trical Code, shall be referred to the Code- within a single Panel, the Chairman of the Making Panel or Panels to which the af- National Electrical Code Committee may fected Articles of the Code have been request the Chairman of the Code-Making assigned. Further processing shall follow Panel to appoint the members of the the procedures indicated in Sections 91 to Technical Subcommittee. 93,inclusive,of these Rules. Section 80.Revisions,Additions,and Deletions to the National Electrical Code 81. To be approved by the Correlating the Board of Directors of the National Committee, a revision of the National Fire Protection Association. Electrical Code shall be either for: 83. A Tentative Interim Amendment is a. A proposed revision for a new a revision applied for and processed in Edition of the Code,or accordance with the Rules of Procedure for b. A Tentative Interim Amendment Tentative Interim Amendments (see Part C (see Part C of these Rules). of these Rules). 82. A new Edition of the National Elec- o 84. A schedule for each revised Edition trical Code will be planned according to Association the ion and shall bn pu suit by the the following conditions: to the announcedlinsuitable news releases to the technical press within six a. Upon the initiative of the Cor- months following the issuance of each re- relating Committee on a three-year or four- vised edition. This schedule shall include year schedule,or dates during which comments or recom- b. After a shorter interval when re- mendations from the public are to be re- quested by the Correlating Committee or ceived. 70-460 APPENDIX-RULES OF PROCEDURE Section 90.Methods for Handling Proposed Code Revisions 91. The stages through which proposed Electrical Code, the Committee Secretary changes in the Code are to be considered prepares for public dissemination through shall be as follows: the National Fire Protection Association a. Proposal is prepared by any member the"Preprint of the Proposed Amendments of the National Electrical Code Committee, for the * National Electrical Code" by any interested person, or by any inter- for study and comment, announcing at that ested organization and submitted to the time a final date for receipt of such corn- Chairman of the National Electrical Code ment in accordance with the prearranged Committee with copies to the Secretary of schedule(see Paragraphs 51.a.and 82). the National Electrical Code Committee and f. Following action specified in Para- to the Chairman of the responsible Code- graph 91.e., all comments received are re- Making Panel. If the submitter is not sure ferred to the Code-Making Panels for their which Code-Making Panel has jurisdiction final consideration and vote. Their propos- or if it involves a subject not previously als are then resubmitted to the Correlating assigned, an extra copy of the proposal Committee, which reviews them and takes should be sent to the Chairman of the one of the actions indicated in Paragraph National Electrical Code Committee for 91.d. proper disposition. g. The Secretary of the National Elec- b. The proposal is circulated to the trical Code Committee then prepares for members of the Code-Making Panel by its publication in the NFPA Technical Corn- Chairman. mittee Reports the proposed * Na- c. The Code-Making Panel considers tional Electrical Code. the proposal and takes one or more of the h. The Electrical Section (see Part A) following steps: is provided with the opportunity of review- (1) Drafts or prepares a proposed ing these amendments or the revised edition revision or addition to the National Elec- at its Annual Meeting prior to Association trical Code, ballots on same, and forwards action on the report.The Electrical Section its recommendations, with a ballot state- may vote to request further consideration ment (see Paragraphs 63 and 64) to the of a specific item by the Correlating Com- Correlating Committee for approval as a mittee.The Correlating Committee in giving proposed revision for a new Edition of the further consideration must either reaffirm Code. its original position or refer the matter (2) Requests coordination with any back to the Code-Making Panel involved other affected Code-Making Panel through for further study. the Correlating Committee, looking for- i. Following final consideration by the ward to future submittal in accordance Correlating Committee, the report is sub- with Paragraph 91.c.(1). mitted to the membership of the National (3) Rejects the proposal, submitting Fire Protection Association in Annual it and a vote statement explaining its ac- Meeting for action in accordance with the Lion to the Correlating Committee. NFPA Regulations Governing Technical (4) Reports to the Correlating Com- Committees. mittee that the proposal has been placed on 92. The NFPA submits each edition of the Panel's docket pending further study. the National Electrical Code (NFPA No. (5) Refers the recommendation to a 70) to the United States of America Stand- Technical Subcommittee for detailed consid- ards Institute for adoption as a USA Stand- eration(see Section 70 of these Rules). and(USA Standard Cl). d. All proposals for revisions or 93. A new edition of the Code is pub- changes made by the Code-Making Panels lished by the National Fire Protection As- and referred to the Correlating Committee sociation. , are reviewed and processed in accordance with Paragraphs 51.d.and 51.f. e. For a new Edition of the National *Next date of issue. PART C—RULES OF PROCEDURE—TENTATIVE INTERIM AMENDMENTS TO THE NATIONAL ELECTRICAL CODE Section 100.Purpose and Scope of Tentative Interim Amendments 101. A Tentative Interim Amendment to vances in the art of safeguarding of per- the National Electrical Code is an amend- sons and of buildings and their contents as ment processed and promulgated separate set forth in Section 90-1 of the National and apart from a revised edition of the Electrical Code. Code in accordance with this Part. 103. This method of amending the Code 102. The purpose of a Tentative Interim shall be resorted to only when action is Amendment is to correct errors and con- urgently needed and should not be deferred flicts or to accomplish recognition of ad- until the next scheduled revision. Section 110.Handling Proposals for Tentative Interim Amendments 111. A proposal for such a Tentative to furnish as many copies of the proposal Interim Amendment should include a full and supporting data as the Chairman of the explanation of the proposal and an exact National Electrical Code Committee may statement of the suggested solution sup- determine are needed for appropriate con- ported by all pertinent data, together with sideration. a specific statement of what new text or 112. The Chairman of the National Elec- amendment of the existing text of the Na- trical Code Committee shall refer each pro- tional Electrical Code is recommended. posal to a special Subcommittee appointed Each proposal must be'endorsed by a mem- by him and consisting of two members of ber of the National Electrical Code Com- the Correlating Committee of the National mittee and the proposer must be prepared Electrical Code Committee and the Chair- APPENDIX—RULES OF PROCEDURE 70-461 man or Chairmen of the Code-Making Pan- Committee shall notify the proposer that el(s) concerned with the proposal. The the National Electrical Code Committee has Chairman and Secretary of the National declined to accept the Tentative Interim Electrical Code Committee shall be voting Amendment as proposed. members of this special Subcommittee.This 115. If agreement is reached between the special Subcommittee shall determine interested Panel or Panels and the proposer whether the proposal is within the stated as to a specific Tentative Interim Amend- purpose of the Tentative Interim Amend- ment of the Code, it shall be submitted to ment Procedure set forth in Paragraphs the Correlating Committee for formal ap- 102 and 103. proval. If approved by both the Panel and a. If the proposal is found not to be the Correlating Committee with no more within the stated purpose of this procedure, than one negative vote by either group, the Chairman of the National Electrical such a Tentative Interim Amendment shall Code Committee shall so notify the sub- be promulgated for the current edition of mitter. the National Electrical Code and will be- 113. If the proposal is found to be within come effective immediately. the stated purpose of this Procedure, the a. If the Panel approves the Tentative Chairman of the National Electrical Code Interim Amendment by a consensus of vot- Committee shall refer the proposal and all ing,but with two or more negative votes or supporting data to the appropriate Code- if there is more than one negative vote by Making Panel or Panels. The Panel or the Correlating Committee, the Association Panels shall report any recommendations to shall publish in one of its publications dis- the Correlating Committee of the National tributed to all members the proposed Electrical Code Committee,following which Amendment with the notice that it is being the Chairman of the National Electrical considered for the current edition of the Code Committee shalPreport the proposed National Electrical Code,and those persons Panel action to the submitter. If the sub- wishing to comment should file such com- mitter is not satisfied with the proposed ments with the Chairman of the National Panel action,he shall be privileged to with- Electrical Code Committee within 60 days draw his proposal or submit a revision of after the mailing date of the publication. the proposed amendment or new data in Any comments so received shall be consid- support of his original proposal. Such a ered by the Code-Making Panel, which submitter's revision, new data, or both, shall make a final report to the Correlating shall be referred to the Code-Making Panel Committee. The latter will then reconsider or Panels for further consideration and the amendment, make a final decision re- report. garding it, and notify the submitter of the a. The Panel is not privileged to revise action taken. or amend the proposal as submitted, ex- b. A Tentative Interim Amendment, cept for purely editorial content. If it is when approved with or without the 60-day felt desirable to amend or revise the sub- waiting period, shall be published by the stantive content of the original proposal, Association in a manner or manners best such amendments or revisions shall be sub- designed to notify all interested parties and ject to the same criteria for handling as a announced in a suitable NFPA news release Tentative Interim Amendment, as the orig- to the technical press. final proposal, namely, the criteria specified 116. All Tentative Interim Amendments in Paragraphs 102 and 103. are subject to further consideration by the 114. If the Panel recommends against appropriate Code-Making Panel or Panels adoption of the proposal and the Corre- in preparing recommendations for a sub- lating Committee determines that the pro- sequent new edition of the National Elec- posal has been processed in accordance trical Code as though originating in accord- with the procedures described herein, the ance with the established regular procedure Chairman of the National Electrical Code for revising the National Electrical Code. PART D—INTERPRETATION PROCEDURE OF THE NATIONAL ELECTRICAL CODE COMMITTEE Section 120.Personnel of Interpretations Committee 121. There shall be a standing committee Article of the Code for which an interpreta- of the National Electrical Code Committee tion is requested,and to be known as the Interpretations Commit- d. At least two other members or al- tee.This Committee shall consist of: ternates of the National Electrical Code a. The Chairman of the Correlating Committee selected by the Chairman de- Committee, who shall be the Chairman of pending upon the availability, experience, the Interpretations Committee and a voting knowledge, and interest of the members. member. The Code-Making Panel Chairman and the b. The Secretary of the Correlating two other members shall be selected for Committee, who shally bef the Secretary of each specific interpretation and shall be each. the Interpretations Committee and a voting discharged upon completion of a member. No member or alternate shall be eligible who is directly concerned with a c. The Chairman of that Code-Making controversial situation to which the spe- Panel which has charge of the affected cific question for interpretation applies. Section 130.Method of Applying for Interpretations 131. Those desiring an interpretation Association, 60 Batterymarch Street, Bos- shall direct their requests to the Chairman ton, Mass. 02110, supplying five identical of the Interpretations Committee, National copies of a statement in which shall ap- Electrical Code, National Fire Protection pear specific references to a single prob- 70-462 APPENDIX-RULES OF PROCEDURE lem, Article or Section. Such a statement 132. When applications involve actual shall be on the business stationery of the field situations, they shall so state and all inquirer and shall be duly signed. parties involved shall be named. Section 140.Forms of Interpretations Recognized 141. Two general forms of findings will arise in the application of the requirements be recognized: of the National Electrical Code which are n. Those makingan interpretation of not subject to interpretation under the pro- cedures described herein.These include de- the literal text. gree and extent of a hazardous location b. Those making an interpretation of area, interpretation of suitability of isola- the intent of the National Electrical Code tion or guarding, interpretation of equiva- Committee when a particular rule was lent protection—and such items which in- adopted. volve an intimate knowledge of the installation rather than a knowledge of the 142. There are certain questions which intent and meaning of the requirement. Section 150.Methods of Handling and Issuing Interpretations 151. The findings of the Interpretations tations reports to the Electrical Correlating Committee will be in its name and for the Committee at its regular meeting, a state- National Electrical Code Committee as a ment shall be made as to extent of con- whole. In any case, where there is more currence of the members in the separate than one negative vote on any proposed findings covered in their report. No other interpretation, the interpretation shall be release shall be made of any minority referred to the Correlating Committee.The views. Correlating Committee shall then make a 154. Each interpretation will be based judgment on the consensus of voting in on the best judgment of the Committee, the Committee to determine that a consen- but the Committee cannot be responsible sus does exist. If it is determined that a for subsequent actions by authorities en- consensus does not exist, the request shall forcing the National Electrical Code as to be referred to the proper Code-Making whether they accept or reject the findings. Panel or Panels. 152. The applicant will be informed of 155. Each Code-Making Panel will be the finding promptly following its having expected to give appropriate consideration been determined. As soon as feasible, the to the text of any Article or Section of the Interpretation, serially numbered, but not National Electrical Code which has pro- otherwise identified, shall be published by duced an Interpretation finding to the end the Association and announced in a suitable that a suitable revision of the text may be NFPA news release to the technical press. recommended to eliminate the difficulty 153. When the Committee on Interpre- which prompted the request. APPENDIX—TIME SCHEDULE-1971 CODE 70-463 TIME SCHEDULE FOR THE 1971 NATIONAL ELECTRICAL CODE Adopted by the Correlating Committee of the National Electrical Code Com- mittee,February 14, 1968 Dec. 1, 1969 Final date for receipt of proposals from the public for revision of the 1968 National Electrical Code preparatory to the issuance of a 1971 edi- tion. Proposals should be forwarded to the Chairman, the Secretary, and the responsible Code Making Panel Chairmen. (Full names and addresses published on Pages 70-v to 70-xi herein.) Dec. 1, 1969 to Code Making Panels consider proposals for Code changes and prepare April 1970 reports for submittal to Correlating Committee. April 14, 1970 Final Date for Code Making Panel reports to be submitted to the Cor- relating Committee April 15, 1970 Correlating Committee reviews reports submitted by Code Making Panels. to May 1970 Advises Panels with respect to existence of consensus, correlates work among Panels, assigns Panel jurisdiction over new and borderline items. Submits reports of the Panels to the NFPA Executive Office for the Pre- print of the Proposed Amendments for the 1971 National Electrical Code. May 1970 Informal report to the NFPA Electrical Section by the Correlating Com- _ mittee at the 1970 NFPA Annual Meeting. July 1970 Preprint of the Proposed Amendments for the 1971 National Electrical Code published for distribution to the National Electrical Code Commit- tee and other interested parties. July 1970 to Period for study by members of the National Electrical Code Committee, Nov. 15, 1970 electrical inspectors, industry and others, and submittal of recommenda- tions to Code Making Panel Chairmen*for changes. Nov. 16, 1970 Code Making Panels reconsider all proposed recommendations for changes to Feb. 1, 1971 and prepare final report for submittal to the Correlating Committee. Feb. 1, 1971 Final date for Code Making Panel reports to be submitted to the Cor- relating Committee. Feb. 1971 Correlating Committee reviews Final Reports of Code Making Panels, accepts or rejects changes, determines existence of consensus, resolves conflicts between Code Making Panel Reports. March 1, 1971 Final date for Correlating Committee to submit the final proposed changes to NFPA for printing in the 1971 NFPA Technical Committee Reports. April 1971 NFPA prints and distributes the 1971 NFPA Technical Committee Re- ports containing the proposed 1971 National Electrical Code to members of the National Electrical Code Committee and to all other NFPA mem- bers who file requests therefor. May 1971 Review by the NFPA Electrical Section and official action by NFPA An- nual Meeting. Submittal by NFPA to United States of America Standards Institute for approval as USA Standard. September 1971 Publication of the 1971 National Electrical Code. *Copies should also be sent to the Chairman and the Secretary. 70-464 appendix—submitting proposed revisions Method of Submitting Proposal to Revise the National Electrical Code A proposal to revise the 1968 Edition of the National Electrical Code must be submitted prior to December 1, 1969 as indicated in the time sched- ule for the 1971 National Electrical Code.The proposal should be sent to the Chairman and Secretary of the National Electrical Code Committee in the form indicated below. The proposal is to be identified by Section number and paragraph letter, where applicable, and is to state the new or revised Code text. It is essential that the submitter fully understand the intent of an existing requirement before attempting to propose a revision of it. The submitter is to identify the source of the proposal, indicating whether it is his own or is being submitted by a committee or organization. The proposal needs to be accompanied by supporting comment explaining the need for the change and should include any available substantiating in- formation or data. Where the submitter believes it imperative that the sup- porting comment shall provide considerable detailed information that can- not be accommodated on a single page, he is to provide 25 copies of this proposal on plain paper for subsequent use by the Panel Chairman in proc- essing the proposal. An example of a properly submitted proposal is as fol- lows: Section 250-74 PROPOSAL: Amend Section 250-74 to read: 250-74. Bonding at Grounding-Type Receptacles. Grounding continuity between a grounded outlet box and the grounding circuit of the receptacle shall be established by means of a bonding jumper between the outlet box and the receptacle grounding terminal. Exception 1: When the box is surface-mounted, direct metal-to-metal con- tact between the device yoke and the box may be used to establish the grounding circuit. Exception 2:Contact devices or yokes designed and approved for the pur- pose may be used in conjunction with the supporting screws to establish the grounding circuit between the device yoke and flush-type boxes installed in walls. SUBMITTER: International Association of Electrical Inspectors. SUPPORTING COMMENT: Direct contact between device yokes and boxes is seldom achieved be- tween devices and boxes installed in walls, inasmuch as flush boxes are in practice seldom found flush, despite the provisions of Section 370-10. Screws and yokes currently in use were designed solely for the support of devices rather than as part of the grounding circuit.The intent of the amend- ment is to encourage the design of either a modified yoke or a supplemental conducting member to augment the supporting screw in the device-to-box grounding circuit. NATIONAL ELECTRICAL CODE 70-465 SPECIAL NOTICE Tentative Interim Amendment No. 146 Released February 14,1968 NATIONAL ELECTRICAL CODE 1968 ARTICLES 500 and 501—HAZARDOUS LOCATIONS Section 500-2.Special Precaution.Revise to Read: 500-2. Special Precaution. The intent of Articles 500-503 is to require a form of construction of equipment, and of installation that will insure safe performance under conditions of proper use and maintenance. It, therefore, is assumed that inspection authorities and users will exercise more than ordinary care with regard to installation and maintenance. The explosion characteristics of air mixtures of hazardous gases, vapors, or dusts vary with the specific material involved. Classification of a hazardous mixture into a Class I hazardous location, Group A, B, C or D, involves determinations of maximum explosion pressure, maxi- mum safe clearance between parts of a clamped joint in an enclosure, and the minimum ignition temperature of the atmospheric mixture. For Class II location, Groups E, F, and G, the classification involves the tightness of the joints of assembly and shaft openings to prevent en- trance of dust in the dust-ignitionproof enclosure, the blanketing effect of layers of dust on the equipment that may cause overheating, electrical conductivity of the dust, and the ignition temperature of the dust. It is necessary therefore that equipment be approved not only for the class of location but also for the specific group of the gas, vapor or dust that will be present. For purposes of testing and approval, various air mixtures (not oxygen enriched) have been grouped on the basis of their hazardous characteristics, and facilities have been made available for testing and approval of equipment for use in the following atmospheric groups: Group A,Atmospheres containing acetylene; Group B, Atmospheres containing butadiene*, ethylene oxide**, hydrogen (or gases or vapors equivalent in hazard to hydrogen, such as manufactured gas),or propylene oxide**; *Group D equipment may be used for this atmosphere if such equipment is isolated in accordance with Section 501-5(a) by sealing all conduit V2 inch size or larger. **Group C equipment may be used for this atmosphere if such equip- ment is isolated in accordance with Section 501-5(a) by sealing all conduit 1/2 inch size or larger. Group C, Atmospheres containing acetaldehyde, cyclopropane, di- ethyl ether, ethylene, isoprene, or unsymmetrical dimethyl hydrazine (UDMH); 70-466 NATIONAL ELECTRICAL CODE Group D,Atmospheres containing acetone,acrylonitrile, alcohol, am- monia, benzine, benzol, butane, ethylene dichloride, gasoline, hexane, lacquer solvent vapors, naphtha, natural gas, propane, propylene, sty- rene,vinyl acetate,vinyl chloride,or xylenes. Group E, Atmospheres containing metal dust, including aluminum, magnesium, and their commercial alloys, and other metals of similarly hazardous characteristics. Group F,Atmospheres containing carbon black,coal or coke dust; Group G,Atmospheres containing flour,starch,or grain dust. Certain chemical atmospheres may have characteristics which would re- quire safeguards beyond those required for any of the above groups. Carbon disulfide is one of these chemicals because of its low ignition temperature (100°C) and the small joint clearance required to arrest its flame. For a complete list noting properties of flammable liquids, gases and solids refer to NFPA No.325M. Section 501-5(a)(2). Amend Section 501-5(a)(2) by adding the sen- tence:"See notes under Group B in Section 500-2." Tentative Interim Amendment No. 148 Released June 27,1968 NATIONAL ELECTRICAL CODE 1968 ARTICLE 550—MOBILE HOMES Section 550-3. Power Supply.Revise as follows: (1) Change the second sentence of Section 550-3 to read: "The power supply to the mobile home shall be feeder circuits consisting of not more than three mobile home supply cords, each rated 50 amperes or permanently installed circuits." (2) Change the second paragraph of Section 550-3(a) to read: "The power supply cord shall be not less than 21 feet, nor more than 361 feet long." (3) Change the first sentence of Section 550-3(b) to read: "Where the calculated load of the mobile home is in excess of 50 amperes, or where separately metered appliances are installed in the mobile home, additional 50 ampere mobile home supply cords shall be installed. Where more than one cord supply system is installed, they shall not be interconnected on either the line side or the load side except that the grounding circuits and grounding means shall be electrically intercon- nected." (4) Change the value of 100 amperes in the first line of Section 550-3(c) to 150 amperes. Section 550-4(a). Disconnecting Means.Revise as follows: Change the second paragraph of Section 550-4(a) by inserting the words"or more"after the word"two"in the first line. �4 e 1:4 ' y fiCe c m- -74' A �a�_s i ", ks' o To: NATIONAL FIRE PROTECTION ASSOCIATION Vt 60 Batterymarch Street z Boston,Mass.02110 0 I- Vl 0 Please send me copies of the 1968 Na- tional Electrical Code (NFPA No. 70, USAS Cl — v▪. 1968) for which $ is enclosed. m Prices a 1 to 5 copies$2.00 ea. 50 copies and over$1.70 ea. re Over 5 copies 1.90 ea. 100 copies and over 1.55 ea. 25 copies and over 1.80 ea. 250 copies and over 1.35 ea. Q m 500 copies and over$1.20 ea. 00 1,000 and over:Ask for Quotation Single copies prepaid when money accompanies order u All others f.o.b.Boston,Mass. z Mail to: Q .. Name ✓ o Company or Organization re Street or Post Office Box u City State ZIP Code Other NFPA Publications of Interest ELECTRICAL AND ASSOCIATED I w No. Short Title Latest Edition Price i 71 Central Station Protective Signaling 1967 $ .60 Systems 72A Local Protective Signaling Systems 1967 .60 72B Auxiliary Protective Signaling Systems 1967 .60 72C Remote Station Protective Signaling Systems 1967 .60 72D Proprietary Protective Signaling Systems 1967 .60 73 Municipal Fire Alarm Systems 1967 .60 74 Household Fire Warning Systems 1967 .50 75 Electronic Computer/Data Processing Equipment, Protection of 1968 .75 76 Essential Electrical Systems for Hospitals 1967 .50 77 Static Electricity,Recommended Practice on 1966 1.00 78 Lightning Protection Code 1968 1.25 79 Electrical Metalworking Machine Tools 1965 .60 496 Purged Enclosures for Electrical Equipment 1967 .50 493-T Tentative Standard on Intrinsically Safe Process Control Equipment 1967 .75 ALLIED AND REFERENCED STANDARDS No. Short Title Latest Edition Price 10 Portable Fire Extinguishers,Installation 1968 $1.00 12 Carbon Dioxide Extinguishing Systems 1968 1.50 13 Sprinkler Systems, Installation 1968 1.50 15 Water Spray Systems 1962 .75 17 Dry Chemical Extinguishing Systems 1968 .75 20 Centrifugal Fire Pumps 1968 2.00 30 Flammable &Combustible Liquids Code 1966 .75 31 Oil Burning Equipment 1968 1.25 325M Fire-Hazard Properties of Flammable Liquids, Gases, and Volatile Solids 1965 2.00 33 Spray Finishing 1966 .60 49 Hazardous Chemicals Data 1968 2.00 54 Gas Appliances&Gas Piping in Buildings 1964 .75 56 Flammable Anesthetics Code 1968 1.25 56B Inhalation Therapy 1968 .75 80 Fire Doors and Windows 1968 1.50 101 Life Safety Code 1967 1.50 255 Building Materials,Tests of Surface Burning Characteristics 1966 .50 302 Motor Craft, Fire Protection for 1968 1.25 303 Marinas and Boatyards,Fire Protection of 1966 .60 409 Aircraft Hangars 1967 .75 410A Aircraft Electrical System Maintenance 1968 .50 501B Mobile Homes 1968 2.00 505 Powered Industrial Trucks 1968 .75 Complete Publications List Available on Request cn O r1 z r� d >j H Chi. H rl7j -4011.11-111.1111110111011- 7 'z, 0 • Ui iu > 1-1 H _ . H x Cr