Table Of ContentNational Electrical Code®
Handbook
Fourteenth Edition
International Electrical Code® Series
Edited by
Mark W. Earley, P.E.
E6di0toB-in-C5hief
Christopher D. Coache
Mark Cloutier
Gil Moniz
Derek Vigstol
With the complete text of the 2017 edition of NFPA 70®, National Electrical Code®
NATIONAL FIRE PROTECTION ASSOCIATION
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Notice Concerning Code Interpretations: This fourteenth edition of the National Electrical Code® Handbook is
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Standards”) are developed in accordance with the published procedures of the NFPA by technical committees
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16 17 18 19 20 5 4 3 2 1
Dedication
This edition of the National Electrical Code® Handbook is
dedicated to Michael J. Johnston for his outstanding leadership
during both the 2014 and 2017 revision cycles of the NEC®.
While Mike continues as chair of the NEC Correlating Com-
mittee through the 2020 edition of the NEC, his leadership has
been so exceptional that we chose to honor him before the end
of his tenure. He is a true leader, with unwavering dedication
to the mission and the people who make it all happen.
The 2017 NEC revision cycle brought extraordinary
changes to how the work gets done. Mike’s exemplary orga-
nizational and communication skills ensured that our panel
members and correlating committee members were well pre-
pared to embrace the changes and complete their all-important
work of revising the NEC. Mike was ahead of the curve by being a strong advocate for training
on the new process and for the use of task groups to help the committees work more efficiently,
including mock meetings with monitored replays online, which enabled participants to get
their questions answered.
Mike is the executive director of standards and safety at the National Electrical Contrac-
tors Association (NECA), where he has been for eight years. He previously served as director
of education codes and standards for the International Association of Electrical Inspectors
(IAEI) for ten years. His diverse electrical background and his work with NECA and IAEI have
empowered Mike to effectively communicate across many industry segments. As a result, his
educational programs have long been recognized as being among some the best in the field.
His dedication to training and the electrical industry has resulted in numerous recognitions,
including the Artie’s Apple Award from the Southwestern Section of IAEI, as well as the pres-
tigious Gold Road Runner pin for his long-standing dedication to NEC education through IAEI.
Mike has authored a number of books at NECA and IAEI, including Significant Changes
toE the7 20D11 a6nd 0201B4 N3EC5 and Bseve2ralF edi4tions 4of Cthe A4na2lysis Aof CFhan2gesC to theE Na8tio8nal
Electrical Code. He has also worked on the Electrical Training Alliances Applied Grounding &
Bonding and Soares Book on Grounding and Bonding. During his time at NECA, numerous
new standards have been added to the National Electrical Installation Standards (NEIS) library.
Mike is an active member of ANSI, IAEI, NFPA, SES, ASSE, ANSI-EVSP, ANSI-EXSC,
the UL Electrical Council, and the National Safety Council. He is the vice-chair of the NFPA
Electrical Section and also served as chair of NEC Code-Making Panel 5 for the 2011 cycle.
Mike has also served as an electrical inspector, an inspection field supervisor, a journeyman,
and a master electrician.
It is often said that great leaders lead by example and recognize that they cannot do the
job alone. Mike has been a master at selecting the right leaders and delegating responsibilities
for training activities, ongoing technical issues needing resolution, and new technical areas,
many of which have resulted in significant additions in the 2014 and 2017 editions of the NEC.
Under Mike’s leadership, the changes in the revision process have been effected and, more
importantly, the NEC has been positioned to keep pace with today’s dynamic electrical industry.
The editors wish to thank Mike for his leadership and untiring dedication to the NEC and for
all the help he has provided to us. It is with extreme pleasure that we proudly dedicate this, the
2017 edition of the National Electrical Code Handbook, to Michael J. Johnston.
iii
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Contents
Preface ix Article 328 Medium Voltage Cable: Type MV 313
Article 330 Metal-Clad Cable: Type MC 314
Acknowledgments x Article 332 Mineral-Insulated, Metal-Sheathed Cable:
Type MI 318
Richard G. Biermann Award xi
Article 334 Nonmetallic-Sheathed Cable: Types NM, NMC,
and NMS 320
About the Editors xii
Article 336 Power and Control Tray Cable:
Type TC 325
Technical Changes T1 Article 338 Service-Entrance Cable: Types SE
and USE 327
Article 90 Introduction 1 Article 340 Underground Feeder and Branch-Circuit Cable:
Type UF 329
Article 342 Intermediate Metal Conduit: Type IMC 330
Chapter 1 General 8
Article 344 Rigid Metal Conduit: Type RMC 333
Article 100 Definitions 8 Article 348 Flexible Metal Conduit: Type FMC 337
Article 110 Requirements for Electrical Installations 30 Article 350 Liquidtight Flexible Metal Conduit:
Type LFMC 339
Article 352 Rigid Polyvinyl Chloride Conduit:
Chapter 2 Wiring and Protection 57
Type PVC 341
Article 200 Use and Identification of Grounded Article 353 High Density Polyethylene Conduit:
Conductors 57 Type HDPE Conduit 345
Article 210 Branch Circuits 61 Article 354 Nonmetallic Underground Conduit with
Article 215 Feeders 90 Conductors: Type NUCC 346
Article 220 Branch-Circuit, Feeder, and Service Load Article 355 Reinforced Thermosetting Resin Conduit:
Ca0lcuBlatio3ns 95 C TEype8 RT8RC 3C48
Article 225 Outside Branch Circuits and Feeders 112 Article 356 Liquidtight Flexible Nonmetallic Conduit:
Article 230 Services 123 Type LFNC 351
Article 240 Overcurrent Protection 146 Article 358 Electrical Metallic Tubing: Type EMT 353
Article 250 Grounding and Bonding 167 Article 360 Flexible Metallic Tubing: Type FMT 356
Article 280 Surge Arresters, Over 1000 Volts 225 Article 362 Electrical Nonmetallic Tubing:
Article 285 Surge-Protective Devices (SPDs), 1000 Volts Type ENT 358
or Less 227 Article 366 Auxiliary Gutters 362
Article 368 Busways 365
Article 370 Cablebus 369
Chapter 3 Wiring Methods and Materials 231
Article 372 Cellular Concrete Floor Raceways 371
Article 300 General Requirements for Wiring Methods and Article 374 Cellular Metal Floor Raceways 372
Materials 231 Article 376 Metal Wireways 374
Article 310 Conductors for General Wiring 252 Article 378 Nonmetallic Wireways 376
Article 312 Cabinets, Cutout Boxes, and Meter Socket Article 380 Multioutlet Assembly 378
Enclosures 284 Article 382 Nonmetallic Extensions 378
Article 314 Outlet, Device, Pull, and Junction Boxes; Article 384 Strut-Type Channel Raceway 381
Conduit Bodies; Fittings; and Handhole Article 386 Surface Metal Raceways 383
Enclosures 289 Article 388 Surface Nonmetallic Raceways 384
Article 320 Armored Cable: Type AC 304 Article 390 Underfloor Raceways 386
Article 322 Flat Cable Assemblies: Type FC 307 Article 392 Cable Trays 387
Article 324 Flat Conductor Cable: Type FCC 309 Article 393 Low-Voltage Suspended Ceiling Power
Article 326 Integrated Gas Spacer Cable: Type IGS 312 Distribution Systems 397
v
Contents
Article 394 Concealed Knob-and-Tube Wiring 400 Article 511 Commercial Garages, Repair
Article 396 Messenger-Supported Wiring 402 and Storage 655
Article 398 Open Wiring on Insulators 403 Article 513 Aircraft Hangars 661
Article 399 Outdoor Overhead Conductors over Article 514 Motor Fuel Dispensing Facilities 665
1000 Volts 405 Article 515 Bulk Storage Plants 673
Article 516 Spray Application, Dipping, Coating,
and Printing Processes Using Flammable
Chapter 4 Equipment for General Use 406
or Combustible Materials 679
Article 400 Flexible Cords and Flexible Cables 406 Article 517 Health Care Facilities 692
Article 402 Fixture Wires 417 Article 518 Assembly Occupancies 718
Article 404 Switches 421 Article 520 Theaters, Audience Areas of Motion Picture
Article 406 Receptacles, Cord Connectors, and Attachment and Television Studios, Performance Areas,
Plugs (Caps) 427 and Similar Locations 722
Article 408 Switchboards, Switchgear, Article 522 Control Systems for Permanent Amusement
and Panelboards 435 Attractions 737
Article 409 Industrial Control Panels 443 Article 525 Carnivals, Circuses, Fairs, and Similar
Article 410 Luminaires, Lampholders, and Lamps 445 Events 739
Article 411 Low-Voltage Lighting 461 Article 530 Motion Picture and Television Studios
Article 422 Appliances 462 and Similar Locations 743
Article 424 Fixed Electric Space-Heating Article 540 Motion Picture Projection Rooms 747
Equipment 469 Article 545 Manufactured Buildings 749
Article 425 Fixed Resistance and Electrode Industrial Article 547 Agricultural Buildings 750
Process Heating Equipment 480 Article 550 Mobile Homes, Manufactured Homes,
Article 426 Fixed Outdoor Electric Deicing and Mobile Home Parks 754
and Snow-Melting Equipment 485 Article 551 Recreational Vehicles and Recreational Vehicle
Article 427 Fixed Electric Heating Equipment for Pipelines Parks 765
and Vessels 489 Article 552 Park Trailers 780
Article 430 Motors, Motor Circuits, Article 553 Floating Buildings 791
and Controllers 492 Article 555 Marinas, Boatyards, and Commercial
Article 440 Air-Conditioning and Refrigerating and Noncommercial Docking
E7D60B35 2F C-E 84 C0
Equipment 537 Facilities 792
Article 445 Generators 546 Article 590 Temporary Installations 798
Article 450 Transformers and Transformer Vaults
(Including Secondary Ties) 549
Chapter 6 Special Equipment 802
Article 455 Phase Converters 563
Article 460 Capacitors 565 Article 600 Electric Signs and Outline Lighting 802
Article 470 Resistors and Reactors 568 Article 604 Manufactured Wiring Systems 811
Article 480 Storage Batteries 569 Article 605 Office Furnishings 813
Article 490 Equipment Over 1000 Volts, Nominal 572 Article 610 Cranes and Hoists 815
Article 620 Elevators, Dumbwaiters, Escalators,
Moving Walks, Platform Lifts, and Stairway
Chapter 5 Special Occupancies 581
Chairlifts 822
Article 500 Hazardous (Classified) Locations, Classes I, II, Article 625 Electric Vehicle Charging System 836
and III, Divisions 1 and 2 581 Article 626 Electrified Truck Parking Spaces 844
Article 501 Class I Locations 593 Article 630 Electric Welders 849
Article 502 Class II Locations 614 Article 640 Audio Signal Processing, Amplification,
Article 503 Class III Locations 621 and Reproduction Equipment 853
Article 504 Intrinsically Safe Systems 625 Article 645 Information Technology Equipment 860
Article 505 Zone 0, 1, and 2 Locations 631 Article 646 Modular Data Centers 865
Article 506 Zone 20, 21, and 22 Locations for Combustible Article 647 Sensitive Electronic Equipment 870
Dusts or Ignitible Fibers/Flyings 647 Article 650 Pipe Organs 872
Article 510 Hazardous (Classified) Locations — Article 660 X-Ray Equipment 873
Specific 655 Article 665 Induction and Dielectric Heating
Equipment 876
vi 2017 National Electrical Code Handbook
Contents
Article 668 Electrolytic Cells 879 Table 2 Radius of Conduit and Tubing Bends 1105
Article 669 Electroplating 882 Table 4 Dimensions and Percent Area of Conduit and
Article 670 Industrial Machinery 883 Tubing (Areas of Conduit or Tubing for the
Article 675 Electrically Driven or Controlled Irrigation Combinations of Wires Permitted in Table 1,
Machines 885 Chapter 9) 1105
Article 680 Swimming Pools, Fountains, and Similar Table 5 Dimensions of Insulated Conductors and
Installations 888 Fixture Wires 1110
Article 682 Natural and Artificially Made Bodies Table 5A Compact Copper and Aluminum Building Wire
of Water 911 Nominal Dimensions and Areas 1114
Article 685 Integrated Electrical Systems 914 Table 8 Conductor Properties 1115
Article 690 Solar Photovoltaic (PV) Systems 914 Table 9 Alternating-Current Resistance and Reactance
Article 691 Large-Scale Photovoltaic (PV) Electric Power for 600-Volt Cables, 3-Phase, 60 Hz, 75°C
Production Facility 932 (167°F) — Three Single Conductors in
Article 692 Fuel Cell Systems 933 Conduit 1116
Article 694 Wind Electric Systems 936 Table 10 Conductor Stranding 1119
Article 695 Fire Pumps 941 Table 11(A) Class 2 and Class 3 Alternating-Current Power
Source Limitations 1120
Table 11(B) Class 2 and Class 3 Direct-Current Power
Chapter 7 Special Conditions 955
Source Limitations 1120
Article 700 Emergency Systems 955 Table 12(A) PLFA Alternating-Current Power Source
Article 701 Legally Required Standby Systems 969 Limitations 1121
Article 702 Optional Standby Systems 973 Table 12(B) PLFA Direct-Current Power Source
Article 705 Interconnected Electric Power Production Limitations 1121
Sources 976
Article 706 Energy Storage Systems 982
Annexes
Article 708 Critical Operations Power Systems
(COPS) 989 Informative Annex A Product Safety Standards 1122
Article 710 Stand-Alone Systems 995 Informative Annex B Application Information for Ampacity
Article 712 Direct Current Microgrids 996 Calculation 1128
Article 720 Circuits and Equipment Operating at Less Than Informative Annex C Conduit and Tubing Fill Tables for
E7 60B35-B F C 2 F2C E 840C0B7294
50 Volts 997 Conductors and Fixture Wires of the
Article 725 Class 1, Class 2, and Class 3 Remote-Control, Same Size 1142
Signaling, and Power-Limited Circuits 998 Informative Annex D Examples 1222
Article 727 Instrumentation Tray Cable: Type ITC 1014 Informative Annex E Types of Construction 1235
Article 728 Fire-Resistive Cable Systems 1016 Informative Annex F Availability and Reliability for Critical
Article 750 Energy Management Systems 1017 Operations Power Systems; and
Article 760 Fire Alarm Systems 1017 Development and Implementation
Article 770 Optical Fiber Cables 1033 of Functional Performance Tests
(FPTs) for Critical Operations Power
Systems 1238
Chapter 8 Communications Systems 1044
Informative Annex G Supervisory Control and Data
Article 800 Communications Circuits 1044 Acquisition (SCADA) 1241
Article 810 Radio and Television Equipment 1063 Informative Annex H Administration and
Article 820 Community Antenna Television and Radio Enforcement 1243
Distribution Systems 1069 Informative Annex I Recommended Tightening Torque
Article 830 Network-Powered Broadband Communications Tables from UL Standard
Systems 1080 486A-B 1251
Article 840 Premises-Powered Broadband Communications Informative Annex J ADA Standards for Accessible
Systems 1095 Design 1253
Index 1256
Chapter 9 Tables 1101
Table 1 Percent of Cross Section of Conduit and Tubing
for Conductors and Cables 1101
National Electrical Code Handbook 2017 vii
Preface
This handbook contains the 54th edition of the National Electrical Code®. Nearly 120 years
have passed since those cold days in March of 1896 (a mere 17 years after the invention of
the incandescent light bulb), when a group representing a variety of organizations met at the
headquarters of the American Society of Mechanical Engineers in New York City to develop a
national code of rules for electrical construction and operation. This was not the first attempt to
establish consistent rules for electrical installations, but it was the first national effort. The need
for standardization was becoming urgent; the number of electrical fires was increasing. By 1881,
one insurer had reported electrical fires in 23 of the 65 insured textile mills in New England.
The major problem was the lack of an authoritative, nationwide electrical installation stan-
dard. As one of the early participants noted, “We were without standards and inspectors, while
manufacturers were without experience and knowledge of real installation needs. The workmen
frequently created the standards as they worked, and rarely did two men think and work alike.”
By 1895, five electrical installation codes were in use in the United States. The manufacture
of products that met the requirements of all five codes was difficult, so something had to be
done to develop a single national code. The committee that met in 1896 recognized that the
five existing codes should be used collectively as the basis for the new code. In the first known
instance of international harmonization, the group also referred to the German code, the code
of the British Board of Trade, and the Phoenix Rules of England. The importance of industry
consensus was immediately recognized; before the committee met again in 1897, the new code
was reviewed by 1200 individuals in the United States and Europe. Shortly thereafter, the first
standardized U.S. electrical code, the National Electrical Code, was published.
The National Electrical Code has become the most widely adopted code in the United
States. It is the installation code used in all 50 states and all U.S. territories and is now used
inE num7erDous 6oth0er cBoun3trie5s. U-sBe of2 theF Co4de co4ntinCues4 to 2gro-wA becFause2 it Cis a -livEing8 do8cu-
ment, constantly changing to reflect changes in technology. And it continues to offer an open-
consensus process. Anyone can submit a proposal for change or a public comment, and all
proposals and comments are subject to a rigorous public review process. The NEC provides the
best technical information, ensuring the practical safeguarding of persons and property from
the hazards arising from the use of electricity.
Throughout its history, the National Electrical Code Committee has been guided by giants
in the electrical industry — too many to mention individually. The first chairman, William J.
Hammer, provided the leadership necessary to get the Code started. More recently, the Code has
been chaired by outstanding leaders such as Richard L. Loyd, Richard W. Osborne, Richard G.
Biermann, D. Harold Ware, James W. Carpenter, and Michael J. Johnston. Each of these men
has devoted many years to the National Electrical Code Committee.
ix
