contents · contents article 90 240introduction ..... 70– 1 chapter 1 general 100 ... 2005...

CONTENTS

Contents

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90 Introduction ........................................ 70– 1

Chapter 1 General

100 Definitions ......................................... 70– 4

I. General .......................................... 70– 4II. Over 600 Volts, Nominal ..................... 70– 10

110 Requirements for Electrical Installations ..... 70– 11

I. General .......................................... 70– 11II. 600 Volts, Nominal, or Less ................. 70– 14

III. Over 600 Volts, Nominal ..................... 70– 17IV. Tunnel Installations over 600 Volts,

Nominal .......................................... 70– 20V. Manholes and Other Electric

Enclosures Intended for PersonnelEntry, All Voltages. [ROP 1–240] ........... 70– 20

Chapter 2 Wiring and Protection

200 Use and Identification of GroundedConductors .......................................... 70– 23

210 Branch Circuits ................................... 70– 25

I. General Provisions ............................ 70– 25II. Branch-Circuit Ratings ....................... 70– 29

III. Required Outlets ............................... 70– 31

215 Feeders ............................................. 70– 35

220 Branch-Circuit, Feeder, and ServiceCalculations ........................................ 70– 37

I. General .......................................... 70– 37II. Branch Circuit Load Calculations .......... 70– 38

III. Feeder and Service Load Calculations ..... 70– 40IV. Optional Feeder and Service Load

Calculations ..................................... 70– 43V. Farm Load Calculation ...................... 70– 46

225 Outside Branch Circuits and Feeders ......... 70– 47

I. General .......................................... 70– 47II. More Than One Building or Other

Structure ......................................... 70– 50III. Over 600 Volts ................................. 70– 52

230 Services ............................................ 70– 53

I. General .......................................... 70– 53II. Overhead Service-Drop Conductors ........ 70– 54

III. Underground Service-LateralConductors ...................................... 70– 56

IV. Service-Entrance Conductors ................ 70– 56V. Service Equipment — General .............. 70– 58

VI. Service Equipment — DisconnectingMeans ............................................ 70– 59

VII. Service Equipment — OvercurrentProtection ........................................ 70– 60

VIII. Services Exceeding 600 Volts, Nominal ... 70– 62

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240 Overcurrent Protection ........................... 70– 63

I. General .......................................... 70– 63II. Location ......................................... 70– 66

III. Enclosures ...................................... 70– 70IV. Disconnecting and Guarding ................ 70– 70V. Plug Fuses, Fuseholders, and Adapters .... 70– 70

VI. Cartridge Fuses and Fuseholders ........... 70– 71VII. Circuit Breakers ............................... 70– 71

VIII. Supervised Industrial Installations .......... 70– 72IX. Overcurrent Protection Over 600 Volts,

Nominal .......................................... 70– 73

250 Grounding and Bonding ......................... 70– 74

I. General .......................................... 70– 74II. System Grounding ............................ 70– 77

III. Grounding Electrode System andGrounding Electrode Conductor ............. 70– 83

IV. Enclosure, Raceway, and Service CableGrounding ....................................... 70– 87

V. Bonding ......................................... 70– 88VI. Equipment Grounding and Equipment

Grounding Conductors ........................ 70– 90VII. Methods of Equipment Grounding ......... 70– 95

VIII. Direct-Current Systems ....................... 70– 97IX. Instruments, Meters, and Relays ............ 70– 98X. Grounding of Systems and Circuits of

1 kV and Over (High Voltage) ............... 70– 99

280 Surge Arresters .................................... 70–100

I. General .......................................... 70–100II. Installation ...................................... 70–101

III. Connecting Surge Arresters .................. 70–101

285 Transient Voltage Surge Suppressors:TVSSs ............................................... 70–102


III. Connecting Transient Voltage SurgeSuppressors ...................................... 70–102

Chapter 3 Wiring Methods and Materials

300 Wiring Methods ................................... 70–104

I. General Requirements ........................ 70–104II. Requirements for Over 600 Volts,

Nominal .......................................... 70–114

310 Conductors for General Wiring ................ 70–115

312 Cabinets, Cutout Boxes, and Meter SocketEnclosures .......................................... 70–141

I. Installation ...................................... 70–141II. Construction Specifications .................. 70–144

314 Outlet, Device, Pull, and Junction Boxes;Conduit Bodies; Fittings; and HandholeEnclosures [ROP 9–15, 9–16] ................... 70–145

I. Scope and General ............................ 70–145II. Installation ...................................... 70–145

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III. Construction Specifications .................. 70–151IV. Pull and Junction Boxes for Use on

Systems Over 600 Volts, Nominal .......... 70–152

320 Armored Cable: Type AC ....................... 70–152


III. Construction Specifications .................. 70–154

322 Flat Cable Assemblies: Type FC ............... 70–154


III. Construction .................................... 70–154

324 Flat Conductor Cable: Type FCC .............. 70–155



326 Integrated Gas Spacer Cable: Type IGS ...... 70–157



328 Medium Voltage Cable: Type MV ............. 70–158



330 Metal-Clad Cable: Type MC .................... 70–158



332 Mineral-Insulated, Metal-Sheathed Cable:Type MI ............................................. 70–160



334 Nonmetallic-Sheathed Cable: Types NM,NMC, and NMS ................................... 70–161



336 Power and Control Tray Cable: Type TC .... 70–163



338 Service-Entrance Cable: Types SE andUSE .................................................. 70–165



340 Underground Feeder and Branch-CircuitCable: Type UF .................................... 70–165


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342 Intermediate Metal Conduit: Type IMC ...... 70–166



344 Rigid Metal Conduit: Type RMC .............. 70–168



348 Flexible Metal Conduit: Type FMC ........... 70–169


350 Liquidtight Flexible Metal Conduit: TypeLFMC ............................................... 70–171



352 Rigid Nonmetallic Conduit: Type RNC ....... 70–172



353 High Density Polyethylene Conduit: TypeHDPE Conduit [ROP 8–96] ..................... 70–174



354 Nonmetallic Underground Conduit withConductors: Type NUCC ........................ 70–177



356 Liquidtight Flexible Nonmetallic Conduit:Type LFNC ......................................... 70–178



358 Electrical Metallic Tubing: Type EMT ........ 70–180



360 Flexible Metallic Tubing: Type FMT ......... 70–181



362 Electrical Nonmetallic Tubing: Type ENT ... 70–182



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366 Auxiliary Gutters [ROP 8–167a] ............... 70–184



368 Busways [ROP 8–172a] ......................... 70–186

I. General Requirements ........................ 70–186II. Installation ...................................... 70–187

III. Construction .................................... 70–188IV. Requirements for Over 600 Volts,

Nominal .......................................... 70–188

370 Cablebus ........................................... 70–189

372 Cellular Concrete Floor Raceways ............ 70–190

374 Cellular Metal Floor Raceways ................ 70–191


376 Metal Wireways ................................... 70–192



378 Nonmetallic Wireways ........................... 70–193



380 Multioutlet Assembly ............................ 70–194

382 Nonmetallic Extensions .......................... 70–195


384 Strut-Type Channel Raceway ................... 70–196



386 Surface Metal Raceways ........................ 70–197



388 Surface Nonmetallic Raceways ................. 70–198



390 Underfloor Raceways ............................ 70–199

392 Cable Trays ........................................ 70–200

394 Concealed Knob-and-Tube Wiring ............. 70–207



396 Messenger Supported Wiring ................... 70–208


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398 Open Wiring on Insulators ...................... 70–209



Chapter 4 Equipment for General Use

400 Flexible Cords and Cables ...................... 70–211

I. General .......................................... 70–211II. Construction Specifications .................. 70–223

III. Portable Cables Over 600 Volts,Nominal .......................................... 70–224

402 Fixture Wires ...................................... 70–224

404 Switches ............................................ 70–229


406 Receptacles, Cord Connectors, andAttachment Plugs (Caps) ......................... 70–232

408 Switchboards and Panelboards ................. 70–235

I. General .......................................... 70–235II. Switchboards ................................... 70–236

III. Panelboards ..................................... 70–236IV. Construction Specifications .................. 70–238

410 Luminaires (Lighting Fixtures),Lampholders, and Lamps ........................ 70–239

I. General .......................................... 70–239II. Luminaire (Fixture) Locations .............. 70–239

III. Provisions at Luminaire (Fixture)Outlet Boxes, Canopies, and Pans ........... 70–240

IV. Luminaire (Fixture) Supports ................ 70–241V. Grounding ...................................... 70–242

VI. Wiring of Luminaires (Fixtures) ............ 70–242VII. Construction of Luminaires (Fixtures) ..... 70–244

VIII. Installation of Lampholders .................. 70–245IX. Construction of Lampholders ................ 70–245X. Lamps and Auxiliary Equipment ........... 70–245

XI. Special Provisions for Flush andRecessed Luminaires (Fixtures) .............. 70–245

XII. Construction of Flush and RecessedLuminaires (Fixtures) .......................... 70–246

XIII. Special Provisions forElectric-Discharge Lighting Systems of1000 Volts or Less ............................. 70–246

XIV. Special Provisions forElectric-Discharge Lighting Systems ofMore Than 1000 Volts ......................... 70–247

XV. Lighting Track ................................. 70–248

411 Lighting Systems Operating at 30 Volts orLess .................................................. 70–249

422 Appliances ......................................... 70–249


III. Disconnecting Means ......................... 70–252IV. Construction .................................... 70–253V. Marking ......................................... 70–254

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424 Fixed Electric Space-Heating Equipment ..... 70–254


III. Control and Protection of FixedElectric Space-Heating Equipment .......... 70–255

IV. Marking of Heating Equipment ............. 70–257V. Electric Space-Heating Cables .............. 70–257

VI. Duct Heaters ................................... 70–259VII. Resistance-Type Boilers ...................... 70–260

VIII. Electrode-Type Boilers ....................... 70–261IX. Electric Radiant Heating Panels and

Heating Panel Sets ............................. 70–261

426 Fixed Outdoor Electric Deicing andSnow-Melting Equipment ........................ 70–263


III. Resistance Heating Elements ................ 70–264IV. Impedance Heating ............................ 70–265V. Skin-Effect Heating ........................... 70–266

VI. Control and Protection ........................ 70–266

427 Fixed Electric Heating Equipment forPipelines and Vessels ............................. 70–267


III. Resistance Heating Elements ................ 70–267IV. Impedance Heating ............................ 70–268V. Induction Heating ............................. 70–269

VI. Skin-Effect Heating ........................... 70–269VII. Control and Protection ........................ 70–269

430 Motors, Motor Circuits, and Controllers ...... 70–270

I. General .......................................... 70–270II. Motor Circuit Conductors .................... 70–276

III. Motor and Branch-Circuit OverloadProtection ........................................ 70–278

IV. Motor Branch-Circuit Short-Circuit andGround-Fault Protection ....................... 70–281

V. Motor Feeder Short-Circuit andGround-Fault Protection ....................... 70–285

VI. Motor Control Circuits ....................... 70–285VII. Motor Controllers ............................. 70–287

VIII. Motor Control Centers ........................ 70–290IX. Disconnecting Means ......................... 70–291X. Adjustable-Speed Drive Systems [ROP

11–6] ............................................. 70–294XI. Over 600 Volts, Nominal ..................... 70–295

XII. Protection of Live Parts — AllVoltages .......................................... 70–296

XIII. Grounding — All Voltages ................... 70–296XIV. Tables ............................................ 70–298

440 Air-Conditioning and RefrigeratingEquipment .......................................... 70–301

I. General .......................................... 70–301II. Disconnecting Means ......................... 70–303

III. Branch-Circuit Short-Circuit andGround-Fault Protection ....................... 70–304

IV. Branch-Circuit Conductors ................... 70–305V. Controllers for Motor-Compressors ........ 70–305

VI. Motor-Compressor and Branch-CircuitOverload Protection ............................ 70–306

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VII. Provisions for Room Air Conditioners ..... 70–307

445 Generators ......................................... 70–308

450 Transformers and Transformer Vaults(Including Secondary Ties) ...................... 70–309

I. General Provisions ............................ 70–309II. Specific Provisions Applicable to

Different Types of Transformers ............. 70–314III. Transformer Vaults ............................ 70–315

455 Phase Converters ................................. 70–316

I. General .......................................... 70–316II. Specific Provisions Applicable to

Different Types of Phase Converters ........ 70–318

460 Capacitors .......................................... 70–318

I. 600 Volts, Nominal, and Under ............. 70–318II. Over 600 Volts, Nominal ..................... 70–319

470 Resistors and Reactors....................................................... 70–320

I. 600 Volts, Nominal, and Under ............. 70–320II. Over 600 Volts, Nominal ..................... 70–320

480 Storage Batteries .................................. 70–320

490 Equipment, Over 600 Volts, Nominal ......... 70–322

I. General .......................................... 70–322II. Equipment — Specific Provisions .......... 70–322

III. Equipment — Metal-Enclosed PowerSwitchgear and Industrial ControlAssemblies ...................................... 70–324

IV. Mobile and Portable Equipment ............ 70–326V. Electrode-Type Boilers ....................... 70–327

Chapter 5 Special Occupancies

500 Hazardous (Classified) Locations, ClassesI, II, and III, Divisions 1 and 2 ................. 70–328

501 Class I Locations [ROP 14–19a] ............... 70–336

I. General .......................................... 70–336II. Wiring ........................................... 70–336

III. Equipment ...................................... 70–342

502 Class II Locations [ROP 14–51a] .............. 70–346


III. Equipment ...................................... 70–348

503 Class III Locations [ROP 14–60a] ............. 70–352


III. Equipment ...................................... 70–353

504 Intrinsically Safe Systems ....................... 70–355

505 Class I, Zone 0, 1, and 2 Locations ........... 70–358

506 Zone 20, 21, and 22 Locations forFlammable Dusts, Fibers, and Flyings ......... 70–371

510 Hazardous (Classified) Locations —Specific .............................................. 70–377

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511 Commercial Garages, Repair and Storage .... 70–377

513 Aircraft Hangars .................................. 70–380

514 Motor Fuel Dispensing Facilities .............. 70–383

515 Bulk Storage Plants .............................. 70–387

516 Spray Application, Dipping, and CoatingProcesses ............................................ 70–391

517 Health Care Facilities ............................ 70–397

I. General .......................................... 70–397II. Wiring and Protection ........................ 70–399

III. Essential Electrical System .................. 70–403IV. Inhalation Anesthetizing Locations ......... 70–410V. X-Ray Installations ............................ 70–412

VI. Communications, Signaling Systems,Data Systems, Fire Alarm Systems, andSystems Less Than 120 Volts, Nominal .... 70–414

VII. Isolated Power Systems ...................... 70–414

518 Assembly Occupancies [ROP 15–57] ......... 70–415

520 Theaters, Audience Areas of MotionPicture and Television Studios,Performance Areas, and Similar Locations ... 70–417

I. General .......................................... 70–417II. Fixed Stage Switchboards .................... 70–418

III. Fixed Stage Equipment Other ThanSwitchboards .................................... 70–419

IV. Portable Switchboards on Stage ............ 70–420V. Portable Stage Equipment Other Than

Switchboards .................................... 70–423VI. Dressing Rooms ............................... 70–425

VII. Grounding ...................................... 70–425

525 Carnivals, Circuses, Fairs, and SimilarEvents ............................................... 70–425

I. General Requirements ........................ 70–425II. Power Sources ................................. 70–425

III. Wiring Methods ................................ 70–426IV. Grounding and Bonding ...................... 70–427

530 Motion Picture and Television Studiosand Similar Locations ............................ 70–427

I. General .......................................... 70–427II. Stage or Set .................................... 70–428

III. Dressing Rooms ............................... 70–430IV. Viewing, Cutting, and Patching Tables .... 70–430V. Cellulose Nitrate Film Storage Vaults ..... 70–430

VI. Substations ...................................... 70–430

540 Motion Picture Projection Rooms ............. 70–431

I. General .......................................... 70–431II. Equipment and Projectors of the

Professional Type .............................. 70–431III. Nonprofessional Projectors .................. 70–432IV. Audio Signal Processing, Amplification,

and Reproduction Equipment ................ 70–432

545 Manufactured Buildings ......................... 70–432

547 Agricultural Buildings ........................... 70–433

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550 Mobile Homes, Manufactured Homes, andMobile Home Parks ............................... 70–436

I. General .......................................... 70–436II. Mobile and Manufactured Homes .......... 70–437

III. Services and Feeders .......................... 70–444

551 Recreational Vehicles and RecreationalVehicle Parks ....................................... 70–446

I. General .......................................... 70–446III. Combination Electrical Systems ............ 70–447IV. Other Power Sources ......................... 70–448V. Nominal 120-Volt or 120/240-Volt

Systems .......................................... 70–449VI. Factory Tests ................................... 70–455

VII. Recreational Vehicle Parks ................... 70–455

552 Park Trailers ....................................... 70–458

I. General .......................................... 70–458II. Low-Voltage Systems ......................... 70–458

III. Combination Electrical Systems ............ 70–459IV. Nominal 120-Volt or 120/240-Volt

Systems .......................................... 70–460V. Factory Tests ................................... 70–467

553 Floating Buildings ................................ 70–467

I. General .......................................... 70–467II. Services and Feeders .......................... 70–467

III. Grounding ...................................... 70–468

555 Marinas and Boatyards .......................... 70–468

590 Temporary Installations [TCC 3–108] ........ 70–471

Chapter 6 Special Equipment

600 Electric Signs and Outline Lighting ........... 70–474

I. General .......................................... 70–474II. Field-Installed Skeleton Tubing ............. 70–477

604 Manufactured Wiring Systems ................. 70–478

605 Office Furnishings (Consisting of LightingAccessories and Wired Partitions) .............. 70–479

610 Cranes and Hoists ................................ 70–480


III. Contact Conductors ........................... 70–483IV. Disconnecting Means ......................... 70–484V. Overcurrent Protection ........................ 70–484

VI. Control .......................................... 70–485VII. Grounding ...................................... 70–486

620 Elevators, Dumbwaiters, Escalators,Moving Walks, Wheelchair Lifts, andStairway Chair Lifts .............................. 70–486

I. General .......................................... 70–486II. Conductors ...................................... 70–488

III. Wiring ........................................... 70–489IV. Installation of Conductors .................... 70–491V. Traveling Cables ............................... 70–492

VI. Disconnecting Means and Control .......... 70–493VII. Overcurrent Protection ........................ 70–494

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VIII. Machine Rooms, Control Rooms,Machinery Spaces, and Control Spaces .... 70–495

IX. Grounding ...................................... 70–495X. Emergency and Standby Power

Systems .......................................... 70–495

625 Electric Vehicle Charging System ............. 70–496

I. General .......................................... 70–496II. Wiring Methods ................................ 70–496

III. Equipment Construction ...................... 70–497IV. Control and Protection ........................ 70–497V. Electric Vehicle Supply Equipment

Locations ........................................ 70–498

630 Electric Welders ................................... 70–499

I. General .......................................... 70–499II. Arc Welders .................................... 70–500

III. Resistance Welders ............................ 70–501IV. Welding Cable ................................. 70–502

640 Audio Signal Processing, Amplification,and Reproduction Equipment .................... 70–502

I. General .......................................... 70–502II. Permanent Audio System Installations ..... 70–505

III. Portable and Temporary Audio SystemInstallations ...................................... 70–506

645 Information Technology Equipment ........... 70–507

647 Sensitive Electronic Equipment ................ 70–509

650 Pipe Organs ........................................ 70–510

660 X-Ray Equipment ................................ 70–511

I. General .......................................... 70–511II. Control .......................................... 70–512

III. Transformers and Capacitors ................ 70–512IV. Guarding and Grounding ..................... 70–512

665 Induction and Dielectric HeatingEquipment .......................................... 70–513

I. General .......................................... 70–513II. Guarding, Grounding, and Labeling ........ 70–514

668 Electrolytic Cells ................................. 70–514

669 Electroplating ...................................... 70–517

670 Industrial Machinery ............................. 70–518

675 Electrically Driven or ControlledIrrigation Machines ............................... 70–519

I. General .......................................... 70–519II. Center Pivot Irrigation Machines ........... 70–521

680 Swimming Pools, Fountains, and SimilarInstallations ......................................... 70–521

I. General .......................................... 70–521II. Permanently Installed Pools ................. 70–524

III. Storable Pools .................................. 70–531IV. Spas and Hot Tubs ............................ 70–532V. Fountains ........................................ 70–534

VI. Pools and Tubs for Therapeutic Use ....... 70–535VII. Hydromassage Bathtubs ...................... 70–536

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682 Natural and Artificially Made Bodies ofWater [ROP 17–154] .............................. 70–537


III. Grounding and Bonding ...................... 70–538

685 Integrated Electrical Systems ................... 70–538

I. General .......................................... 70–538II. Orderly Shutdown ............................. 70–538

690 Solar Photovoltaic Systems ..................... 70–539

I. General .......................................... 70–539II. Circuit Requirements ......................... 70–541

III. Disconnecting Means ......................... 70–543IV. Wiring Methods ................................ 70–545V. Grounding ...................................... 70–546

VI. Marking ......................................... 70–546VII. Connection to Other Sources ................ 70–547

VIII. Storage Batteries ............................... 70–548IX. Systems Over 600 Volts ...................... 70–549

692 Fuel Cell Systems ................................ 70–549

I. General .......................................... 70–549II. Circuit Requirements ......................... 70–550

III. Disconnecting Means ......................... 70–550IV. Wiring Methods ................................ 70–551V. Grounding ...................................... 70–551

VI. Marking ......................................... 70–551VII. Connection to Other Circuits ................ 70–551

VIII. Outputs Over 600 Volts ...................... 70–552

695 Fire Pumps ......................................... 70–552

Chapter 7 Special Conditions

700 Emergency Systems .............................. 70–557

I. General .......................................... 70–557II. Circuit Wiring .................................. 70–558

III. Sources of Power .............................. 70–559IV. Emergency System Circuits for

Lighting and Power ............................ 70–560V. Control — Emergency Lighting

Circuits ........................................... 70–561VI. Overcurrent Protection ........................ 70–561

701 Legally Required Standby Systems ............ 70–561


III. Sources of Power .............................. 70–563IV. Overcurrent Protection ........................ 70–564

702 Optional Standby Systems ...................... 70–564


III. Grounding ...................................... 70–565IV. Sources of Power [ROP 13–155] ........... 70–565

705 Interconnected Electric Power ProductionSources .............................................. 70–566

720 Circuits and Equipment Operating at LessThan 50 Volts ...................................... 70–567

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725 Class 1, Class 2, and Class 3Remote-Control, Signaling, andPower-Limited Circuits [ROP 3–126] .......... 70–568

I. General .......................................... 70–568II. Class 1 Circuits ................................ 70–569

III. Class 2 and Class 3 Circuits ................. 70–571VI. Listing Requirements ......................... 70–576

727 Instrumentation Tray Cable: Type ITC ........ 70–577

760 Fire Alarm Systems [ROP 3–223] ............. 70–578

I. General .......................................... 70–578II. Non–Power-Limited Fire Alarm

(NPLFA) Circuits .............................. 70–579III. Power-Limited Fire Alarm (PLFA)

Circuits ........................................... 70–582

770 Optical Fiber Cables and Raceways [ROP16–5] ................................................ 70–587

I. General .......................................... 70–587II. Protection ....................................... 70–588

III. Cables Within Buildings ...... .................... {ROP 16-24]... 70–589VI. Listing Requirements ......................... 70–591

780 Closed-Loop and Programmed PowerDistribution ......................................... 70–592

Chapter 8 Communications Systems

800 Communications Circuits ........................ 70–594

I. General .......................................... 70–594II. Wires and Cables Outside and Entering

Buildings [ROP 16–84] ....................... 70–595III. Protection ....................................... 70–596IV. Grounding Methods ........................... 70–597V. Wires and Cables Within Buildings

[ROP 16–100] ................................... 70–598VI. Listing Requirements ......................... 70–601

810 Radio and Television Equipment ............... 70–603

I. General .......................................... 70–603II. Receiving Equipment — Antenna

Systems .......................................... 70–603III. Amateur Transmitting and Receiving

Stations — Antenna Systems ................. 70–606IV. Interior Installation — Transmitting

Stations ........................................... 70–606

820 Community Antenna Television and RadioDistribution Systems .............................. 70–607

I. General .......................................... 70–607II. Cables Outside and Entering Buildings .... 70–608

III. Protection ....................................... 70–609IV. Grounding Methods ........................... 70–609V. Cables Within Buildings ..................... 70–610

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830 Network-Powered BroadbandCommunications Systems ........................ 70–614

I. General .......................................... 70–614II. Cables Outside and Entering Buildings .... 70–615

III. Protection ....................................... 70–618IV. Grounding Methods ........................... 70–619V. Cables Within Buildings ..................... 70–620

VI. Listing Requirements ......................... 70–622ABLES

Chapter 9 Tables

1 Percent of Cross Section of Conduit andTubing for Conductors ........................... 70–624

2 Radius of Conduit and Tubing Bends[ROP 8–24a] ....................................... 70–624

4 Dimensions and Percent Area of Conduitand Tubing(Areas of Conduit or Tubing for theCombinations of Wires Permitted in Table1, Chapter 9) [ROP 8–294] ...................... 70–625

5 Dimensions of Insulated Conductors andFixture Wires ....................................... 70–629

5A Compact Aluminum Building WireNominal Dimensions* and Areas [ROP6–108, 6–109] ...................................... 70–634

8 Conductor Properties [ROP 6–111] ........... 70–634

9 Alternating-Current Resistance andReactance for 600-Volt Cables, 3-Phase,60 Hz, 75°C (167°F) — Three SingleConductors in Conduit ............................ 70–635

1(A) Class 2 and Class 3 Alternating-CurrentPower Source Limitations ........................ 70–637

11(B) Class 2 and Class 3 Direct-Current PowerSource Limitations ................................ 70–637

2(A) PLFA Alternating-Current Power SourceLimitations .......................................... 70–638

2(B) PLFA Direct-Current Power SourceLimitations [ROP 3–301] ........................ 70–638

Annex A ............................................ 70–640

Annex B ............................................ 70–643

Annex C ............................................ 70–657

Annex D ............................................ 70–679

Annex E ............................................. 70–691

Annex F ............................................. 70–693

Annex G ............................................ 70–696

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ARTICLE 90Introduction

90.1 Purpose.

(A) Practical Safeguarding. The purpose of this Code isthe practical safeguarding of persons and property fromhazards arising from the use of electricity.

(B) Adequacy. This Code contains provisions that are con-sidered necessary for safety. Compliance therewith andproper maintenance will result in an installation that is es-sentially free from hazard but not necessarily efficient, con-venient, or adequate for good service or future expansion ofelectrical use.

FPN: Hazards often occur because of overloading of wir-ing systems by methods or usage not in conformity withthis Code. This occurs because initial wiring did not pro-vide for increases in the use of electricity. An initial ad-equate installation and reasonable provisions for systemchanges will provide for future increases in the use ofelectricity.

(C) Intention. This Code is not intended as a design speci-fication or an instruction manual for untrained persons.

(D) Relation to Other International Standards. The re-quirements in this Code address the fundamental principlesof protection for safety contained in Section 131 of Inter-national Electrotechnical Commission Standard 60364-1,Electrical Installations of Buildings. [ROP 1–16a]

FPN: IEC 60364-1, Section 131, contains fundamentalprinciples of protection for safety that encompass protec-tion against electric shock, protection against thermal ef-fects, protection against overcurrent, protection againstfault currents, and protection against overvoltage. All ofthese potential hazards are addressed by the requirements inthis Code.

90.2 Scope.

(A) Covered. This Code covers the installation of electricconductors, cables, equipment, and raceways; signaling andcommunications conductors, cables, equipment, and race-ways; and optical fiber cables and raceways for the follow-ing: [ROP 1–18]

(1) Public and private premises, including buildings, struc-tures, mobile homes, recreational vehicles, and floatingbuildings

(2) Yards, lots, parking lots, carnivals, and industrial sub-stations

FPN: For additional information concerning such installa-tions in an industrial or multibuilding complex, see theANSI C2-2002, National Electrical Safety Code. [ROP1–22a]

(3) Installations of conductors and equipment that connectto the supply of electricity

(4) Installations used by the electric utility, such as officebuildings, warehouses, garages, machine shops, andrecreational buildings, which are not an integral part ofa generating plant, substation, or control center. [ROP1–23]

(B) Not Covered. This Code does not cover the following:

(1) Installations in ships, watercraft other than floatingbuildings, railway rolling stock, aircraft, or automotivevehicles other than mobile homes and recreational ve-hicles

FPN: Although the scope of this Code indicates that theCode does not cover installations in ships, portions of thisCode are incorporated by reference into Title 46, Code ofFederal Regulations, Parts 110–113.

(2) Installations underground in mines and self-propelledmobile surface mining machinery and its attendantelectrical trailing cable [ROP 1–28]

(3) Installations of railways for generation, transformation,transmission, or distribution of power used exclusivelyfor operation of rolling stock or installations used ex-clusively for signaling and communications purposes

(4) Installations of communications equipment under theexclusive control of communications utilities locatedoutdoors or in building spaces used exclusively forsuch installations

(5) Installations under the exclusive control of an electricutility where such installations

a. Consist of service drops or service laterals, and as-sociated metering, or

b. Are located in legally established easements, rights-of-way, or by other agreements either designated byor recognized by public service commissions, utilitycommissions, or other regulatory agencies havingjurisdiction for such installations, or

c. Are on property owned or leased by the electricutility for the purpose of communications, metering,generation, control, transformation, transmission, ordistribution of electric energy.

FPN to (4) and (5): Utilities are organizations, typicallydesignated or recognized by governmental law or regula-tion by public service/utility commissions, that install, op-erate, and maintain electric supply (such as generation,transmission, or distribution systems) or communicationsystems (such as telephone, CATV, Internet, satellite, or

NFPA 70

National Electrical Code®

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data services). As such, the utility is subject to compliancewith codes and standards covering these activities relevantto their industry as adopted under governmental law orregulation. Refer to the appropriate governmental bodies,such as state regulatory commissions, Federal EnergyRegulatory Commission, and Federal CommunicationsCommission. [ROP 1–25]

(C) Special Permission. The authority having jurisdictionfor enforcing this Code may grant exception for the instal-lation of conductors and equipment that are not under theexclusive control of the electric utilities and are used toconnect the electric utility supply system to the service-entrance conductors of the premises served, provided suchinstallations are outside a building or terminate immedi-ately inside a building wall.

90.3 Code Arrangement. This Code is divided into theintroduction and nine chapters, as shown in Figure 90.3.Chapters 1, 2, 3, and 4 apply generally; Chapters 5, 6, and7 apply to special occupancies, special equipment, or otherspecial conditions. These latter chapters supplement ormodify the general rules. Chapters 1 through 4 apply exceptas amended by Chapters 5, 6, and 7 for the particular con-ditions.

Chapter 8 covers communications systems and is notsubject to the requirements of Chapters 1 through 7 exceptwhere the requirements are specifically referenced in Chap-ter 8.

Chapter 9 consists of tables.Annexes are not part of the requirements of this Code

but are included for informational purposes only.

90.4 Enforcement. This Code is intended to be suitablefor mandatory application by governmental bodies that ex-ercise legal jurisdiction over electrical installations, includ-ing signaling and communications systems, and for use byinsurance inspectors. The authority having jurisdiction forenforcement of the Code has the responsibility for makinginterpretations of the rules, for deciding on the approval ofequipment and materials, and for granting the special per-mission contemplated in a number of the rules.

By special permission, the authority having jurisdictionmay waive specific requirements in this Code or permitalternative methods where it is assured that equivalent ob-jectives can be achieved by establishing and maintainingeffective safety.

This Code may require new products, constructions, ormaterials that may not yet be available at the time the Codeis adopted. In such event, the authority having jurisdictionmay permit the use of the products, constructions, or mate-rials that comply with the most recent previous edition ofthis Code adopted by the jurisdiction.

90.5 Mandatory Rules, Permissive Rules, and Explana-tory Material.

(A) Mandatory Rules. Mandatory rules of this Code arethose that identify actions that are specifically required orprohibited and are characterized by the use of the termsshall or shall not.

(B) Permissive Rules. Permissive rules of this Code arethose that identify actions that are allowed but not required,are normally used to describe options or alternative meth-ods, and are characterized by the use of the terms shall bepermitted or shall not be required.

(C) Explanatory Material. Explanatory material, such asreferences to other standards, references to related sectionsof this Code, or information related to a Code rule, is in-cluded in this Code in the form of fine print notes (FPNs).Fine print notes are informational only and are not enforce-able as requirements of this Code.

Brackets containing section references to another NFPAdocument are for informational purposes only and are pro-vided as a guide to indicate the source of the extracted text.These bracketed references immediately follow the ex-tracted text. [ROP 1–34]

FPN: The format and language used in this Code followsguidelines established by NFPA and published in the NECStyle Manual. Copies of this manual can be obtained fromNFPA.

90.6 Formal Interpretations. To promote uniformity ofinterpretation and application of the provisions of thisCode, formal interpretation procedures have been estab-

Chapter 1 — General

Chapter 2 — Wiring and Protection

Chapter 3 — Wiring Methods and Materials

Chapter 4 — Equipment for General Use

Applies generallyto all electrical

installations

Chapter 5 — Special Occupancies

Chapter 6 — Special Equipment

Chapter 7 — Special Conditions

Supplements or modifiesChapters 1 through 4

Chapter 9 — Tables

Annex A through Annex G

Chapter 8 — Communications Systems

Informational only; not mandatory

Applicable as referenced

Chapter 8 is not subject to the requirements of Chapters 1 through 7 except where the requirements are specifically referenced in Chapter 8.

Figure 90.3 Code arrangement.

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lished and are found in the NFPA Regulations GoverningCommittee Projects.

90.7 Examination of Equipment for Safety. For specificitems of equipment and materials referred to in this Code,examinations for safety made under standard conditionsprovide a basis for approval where the record is made gen-erally available through promulgation by organizationsproperly equipped and qualified for experimental testing,inspections of the run of goods at factories, and service-value determination through field inspections. This avoidsthe necessity for repetition of examinations by differentexaminers, frequently with inadequate facilities for suchwork, and the confusion that would result from conflictingreports on the suitability of devices and materials examinedfor a given purpose.

It is the intent of this Code that factory-installed inter-nal wiring or the construction of equipment need not beinspected at the time of installation of the equipment, ex-cept to detect alterations or damage, if the equipment hasbeen listed by a qualified electrical testing laboratory that isrecognized as having the facilities described in the preced-ing paragraph and that requires suitability for installation inaccordance with this Code.

FPN No. 1: See requirements in 110.3.

FPN No. 2: Listed is defined in Article 100.

FPN No. 3: Annex A contains an informative list of prod-uct safety standards for electrical equipment.

90.8 Wire and Cable Planning.

(A) Future Expansion and Convenience. Plans andspecifications that provide ample space in raceways, spareraceways, and additional spaces allow for future increasesin electric power and communication circuits. Distributioncenters located in readily accessible locations provide con-venience and safety of operation. [ROP 1–35]

(B) Number of Circuits in Enclosures. It is elsewhereprovided in this Code that the number of wires and circuitsconfined in a single enclosure be varyingly restricted. Lim-iting the number of circuits in a single enclosure minimizesthe effects from a short circuit or ground fault in one cir-cuit.

90.9 Units of Measurement.

(A) Measurement System of Preference. For the purposeof this Code, metric units of measurement are in accor-

dance with the modernized metric system known as theInternational System of Units (SI).

(B) Dual System of Units. The SI units shall appear first,and the inch-pound units shall immediately follow in pa-rentheses. The conversion from the inch-pound units to SIunits shall be based on hard conversion except as providedin 90.9(C).

(C) Permitted Uses of Soft Conversion. The cases givenin 90.9(C)(1) through (4) shall not be required to use hardconversion and shall be permitted to use soft conversion.

(1) Trade Sizes. Where the actual measured size of a prod-uct is not the same as the nominal size, trade size designa-tors shall be used rather than dimensions. Trade practicesshall be followed in all cases.

(2) Extracted Material. Where material is extracted fromanother standard, the context of the original material shallnot be compromised or violated. Any editing of the ex-tracted text shall be confined to making the style consistentwith that of the NEC.

(3) Industry Practice. Where industry practice is to ex-press units in inch-pound units, the inclusion of SI unitsshall not be required.

(4) Safety. Where a negative impact on safety would re-sult, soft conversion shall be used. [ROP 1–45]

(D) Compliance. The conversion from inch-pound units toSI units shall be permitted to be an approximate conver-sion. Compliance with the numbers shown in either the SIsystem or the inch-pound system shall constitute compli-ance with this Code.

FPN No. 1: Hard conversion is considered a change indimensions or properties of an item into new sizes thatmight or might not be interchangeable with the sizes usedin the original measurement. Soft conversion is considereda direct mathematical conversion and involves a change inthe description of an existing measurement but not in theactual dimension.

FPN No. 2: SI conversions are based on IEEE/ASTM SI10-1997, Standard for the Use of the International Systemof Units (SI): The Modern Metric System.

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Chapter 1 General

ARTICLE 100Definitions

Scope. This article contains only those definitions essentialto the proper application of this Code. It is not intended toinclude commonly defined general terms or commonly de-fined technical terms from related codes and standards. Ingeneral, only those terms that are used in two or morearticles are defined in Article 100. Other definitions areincluded in the article in which they are used but may bereferenced in Article 100.

Part I of this article contains definitions intended toapply wherever the terms are used throughout this Code.Part II contains definitions applicable only to the parts ofarticles specifically covering installations and equipmentoperating at over 600 volts, nominal.

I. General

Abandoned Cables. Cable that is neither terminated atboth ends nor identified for future use with a tag. [ROP1–46]

Accessible (as applied to equipment). Admitting closeapproach; not guarded by locked doors, elevation, or othereffective means.

Accessible (as applied to wiring methods). Capable ofbeing removed or exposed without damaging the buildingstructure or finish or not permanently closed in by the struc-ture or finish of the building.

Accessible, Readily (Readily Accessible). Capable of be-ing reached quickly for operation, renewal, or inspectionswithout requiring those to whom ready access is requisiteto climb over or remove obstacles or to resort to portableladders, and so forth.

Air Duct. A conduit for or passageway for conveying air toor from heating, cooling, air conditioning, or ventilatingequipment, but not including the plenum. [ROP 1–49]

Ampacity. The current, in amperes, that a conductor cancarry continuously under the conditions of use without ex-ceeding its temperature rating.

Appliance. Utilization equipment, generally other than in-dustrial, that is normally built in standardized sizes or typesand is installed or connected as a unit to perform one ormore functions such as clothes washing, air conditioning,food mixing, deep frying, and so forth.

Approved. Acceptable to the authority having jurisdiction.[TCC 1–54]

Askarel. A generic term for a group of nonflammable syn-thetic chlorinated hydrocarbons used as electrical insulatingmedia. Askarels of various compositional types are used.Under arcing conditions, the gases produced, while consist-ing predominantly of noncombustible hydrogen chloride,can include varying amounts of combustible gases, depend-ing on the askarel type.

Attachment Plug (Plug Cap) (Plug). A device that, byinsertion in a receptacle, establishes a connection betweenthe conductors of the attached flexible cord and the conduc-tors connected permanently to the receptacle.

Authority Having Jurisdiction (AHJ). The organization,office, or individual responsible for approving equipment,materials, an installation, or a procedure. [ROP 1–57]

FPN: The phrase “authority having jurisdiction” is used inNFPA documents in a broad manner, since jurisdictions andapproval agencies vary, as do their responsibilities. Wherepublic safety is primary, the AHJ may be a federal, state,local, or other regional department or individual such as afire chief; fire marshal; chief of a fire prevention bureau,labor department, or health department; building official;electrical inspector; or others having statutory authority.For insurance purposes, an insurance inspection depart-ment, rating bureau, or other insurance company represen-tative may be the AHJ. In many circumstances, the propertyowner or his or her designated agent assumes the role of theAHJ; at government installations, the commanding officeror departmental official may be the AHJ. [ROP 1–57]

Automatic. Self-acting, operating by its own mechanismwhen actuated by some impersonal influence, as, for ex-ample, a change in current, pressure, temperature, or me-chanical configuration.

Bathroom. An area including a basin with one or more ofthe following: a toilet, a tub, or a shower.

Bonding (Bonded). The permanent joining of metallicparts to form an electrically conductive path that ensureselectrical continuity and the capacity to conduct safely anycurrent likely to be imposed.

Bonding Jumper. A reliable conductor to ensure the re-quired electrical conductivity between metal parts requiredto be electrically connected.

Bonding Jumper, Equipment. The connection betweentwo or more portions of the equipment grounding conduc-tor.

Bonding Jumper, Main. The connection between thegrounded circuit conductor and the equipment groundingconductor at the service.

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Bonding Jumper, System. The connection between thegrounded circuit conductor and the equipment groundingconductor at a separately derived system. [ROP 1–63, TCC1–63]

Branch Circuit. The circuit conductors between the finalovercurrent device protecting the circuit and the outlet(s).

Branch Circuit, Appliance. A branch circuit that suppliesenergy to one or more outlets to which appliances are to beconnected and that has no permanently connected lumi-naires (lighting fixtures) that are not a part of an appliance.

Branch Circuit, General-Purpose. A branch circuit thatsupplies two or more receptacles or outlets for lighting andappliances.

Branch Circuit, Individual. A branch circuit that suppliesonly one utilization equipment.

Branch Circuit, Multiwire. A branch circuit that consistsof two or more ungrounded conductors that have a voltagebetween them, and a grounded conductor that has equalvoltage between it and each ungrounded conductor of thecircuit and that is connected to the neutral or groundedconductor of the system.

Building. A structure that stands alone or that is cut offfrom adjoining structures by fire walls with all openingstherein protected by approved fire doors.

Cabinet. An enclosure that is designed for either surfacemounting or flush mounting and is provided with a frame,mat, or trim in which a swinging door or doors are or canbe hung.

Circuit Breaker. A device designed to open and close acircuit by nonautomatic means and to open the circuit au-tomatically on a predetermined overcurrent without damageto itself when properly applied within its rating.

FPN: The automatic opening means can be integral, directacting with the circuit breaker, or remote from the circuitbreaker.

Adjustable (as applied to circuit breakers). A qualifyingterm indicating that the circuit breaker can be set to trip atvarious values of current, time, or both, within a predeter-mined range.

Instantaneous Trip (as applied to circuit breakers). Aqualifying term indicating that no delay is purposely intro-duced in the tripping action of the circuit breaker.

Inverse Time (as applied to circuit breakers). A qualifyingterm indicating that there is purposely introduced a delay inthe tripping action of the circuit breaker, which delay de-creases as the magnitude of the current increases.

Nonadjustable (as applied to circuit breakers). A quali-fying term indicating that the circuit breaker does not have

any adjustment to alter the value of current at which it willtrip or the time required for its operation.

Setting (of circuit breakers). The value of current, time, orboth, at which an adjustable circuit breaker is set to trip.

Concealed. Rendered inaccessible by the structure or finishof the building. Wires in concealed raceways are consid-ered concealed, even though they may become accessibleby withdrawing them.

Conductor, Bare. A conductor having no covering or elec-trical insulation whatsoever.

Conductor, Covered. A conductor encased within materialof composition or thickness that is not recognized by thisCode as electrical insulation.

Conductor, Insulated. A conductor encased within mate-rial of composition and thickness that is recognized by thisCode as electrical insulation.

Conduit Body. A separate portion of a conduit or tubingsystem that provides access through a removable cover(s)to the interior of the system at a junction of two or moresections of the system or at a terminal point of the system.

Boxes such as FS and FD or larger cast or sheet metalboxes are not classified as conduit bodies.

Connector, Pressure (Solderless). A device that estab-lishes a connection between two or more conductors orbetween one or more conductors and a terminal by meansof mechanical pressure and without the use of solder.

Continuous Load. A load where the maximum current isexpected to continue for 3 hours or more.

Controller. A device or group of devices that serves togovern, in some predetermined manner, the electric powerdelivered to the apparatus to which it is connected.

Cooking Unit, Counter-Mounted. A cooking appliancedesigned for mounting in or on a counter and consisting ofone or more heating elements, internal wiring, and built-inor mountable controls.

Coordination (Selective). Localization of an overcurrentcondition to restrict outages to the equipment affected, ac-complished by the choice of overcurrent-protective devicesor settings. [ROP 1–76]

Copper-Clad Aluminum Conductors. Conductors drawnfrom a copper-clad aluminum rod with the copper metallur-gically bonded to an aluminum core. The copper forms aminimum of 10 percent of the cross-sectional area of asolid conductor or each strand of a stranded conductor.

Cutout Box. An enclosure designed for surface mountingthat has swinging doors or covers secured directly to andtelescoping with the walls of the box proper.

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Dead Front. Without live parts exposed to a person on theoperating side of the equipment.

Demand Factor. The ratio of the maximum demand of asystem, or part of a system, to the total connected load of asystem or the part of the system under consideration.

Device. A unit of an electrical system that is intended tocarry or control but not utilize electric energy. [ROP 1–78]

Disconnecting Means. A device, or group of devices, orother means by which the conductors of a circuit can bedisconnected from their source of supply.

Dusttight. Constructed so that dust will not enter the en-closing case under specified test conditions.

Duty, Continuous. Operation at a substantially constantload for an indefinitely long time.

Duty, Intermittent. Operation for alternate intervals of (1)load and no load; or (2) load and rest; or (3) load, no load,and rest.

Duty, Periodic. Intermittent operation in which the loadconditions are regularly recurrent.

Duty, Short-Time. Operation at a substantially constantload for a short and definite, specified time.

Duty, Varying. Operation at loads, and for intervals oftime, both of which may be subject to wide variation.

Dwelling Unit. One or more rooms for the use of one ormore persons as a housekeeping unit with space for eating,living, cooking, and sleeping, and permanent provisions forsanitation. [ROP 1–84]

Dwelling, One-Family. A building that consists solely ofone dwelling unit.

Dwelling, Two-Family. A building that consists solely oftwo dwelling units.

Dwelling, Multifamily. A building that contains three ormore dwelling units.

Electric Sign. A fixed, stationary, or portable self-contained, electrically illuminated utilization equipmentwith words or symbols designed to convey information orattract attention.

Enclosed. Surrounded by a case, housing, fence, or wall(s)that prevents persons from accidentally contacting ener-gized parts.

Enclosure. The case or housing of apparatus, or the fenceor walls surrounding an installation to prevent personnelfrom accidentally contacting energized parts or to protectthe equipment from physical damage.

FPN: See Table 430.91 for examples of enclosure types.

Energized. Electrically connected to, or is, a source ofvoltage. [ROP 1–88]

Equipment. A general term including material, fittings, de-vices, appliances, luminaires (fixtures), apparatus, and thelike used as a part of, or in connection with, an electricalinstallation.

Explosionproof Apparatus. Apparatus enclosed in a casethat is capable of withstanding an explosion of a specifiedgas or vapor that may occur within it and of preventing theignition of a specified gas or vapor surrounding the enclo-sure by sparks, flashes, or explosion of the gas or vaporwithin, and that operates at such an external temperaturethat a surrounding flammable atmosphere will not be ig-nited thereby.

FPN: For further information, see ANSI/UL 1203-1999,Explosion-Proof and Dust-Ignition-Proof Electrical Equip-ment for Use in Hazardous (Classified) Locations.

Exposed (as applied to live parts). Capable of being in-advertently touched or approached nearer than a safe dis-tance by a person. It is applied to parts that are not suitablyguarded, isolated, or insulated.

Exposed (as applied to wiring methods). On or attachedto the surface or behind panels designed to allow access.

Externally Operable. Capable of being operated withoutexposing the operator to contact with live parts.

Feeder. All circuit conductors between the service equip-ment, the source of a separately derived system, or otherpower supply source and the final branch-circuit overcur-rent device.

Festoon Lighting. A string of outdoor lights that is sus-pended between two points.

Fitting. An accessory such as a locknut, bushing, or otherpart of a wiring system that is intended primarily to per-form a mechanical rather than an electrical function.

Garage. A building or portion of a building in which one ormore self-propelled vehicles can be kept for use, sale, stor-age, rental, repair, exhibition, or demonstration purposes.

FPN: For commercial garages, repair and storage, see Ar-ticle 511.

Ground. A conducting connection, whether intentional oraccidental, between an electrical circuit or equipment andthe earth or to some conducting body that serves in place ofthe earth.

Grounded. Connected to earth or to some conducting bodythat serves in place of the earth.

Grounded, Effectively. Intentionally connected to earththrough a ground connection or connections of sufficiently



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low impedance and having sufficient current-carrying ca-pacity to prevent the buildup of voltages that may result inundue hazards to connected equipment or to persons.

Grounded, Solidly. Connected to ground without insertingany resistor or impedance device. [ROP 1–136]

Grounded Conductor. A system or circuit conductor thatis intentionally grounded.

Grounding Conductor. A conductor used to connectequipment or the grounded circuit of a wiring system to agrounding electrode or electrodes.

Grounding Conductor, Equipment. The conductor usedto connect the non–current-carrying metal parts of equip-ment, raceways, and other enclosures to the systemgrounded conductor, the grounding electrode conductor, orboth, at the service equipment or at the source of a sepa-rately derived system.

Grounding Electrode. A device that establishes an electri-cal connection to the earth. [ROP 1–97]

Grounding Electrode Conductor. The conductor used toconnect the grounding electrode(s) to the equipmentgrounding conductor, to the grounded conductor, or to both,at the service, at each building or structure where suppliedby a feeder(s) or branch circuit(s), or at the source of aseparately derived system. [ROP 1–98]

Ground-Fault Circuit Interrupter (GFCI). A device in-tended for the protection of personnel that functions to de-energize a circuit or portion thereof within an establishedperiod of time when a current to ground exceeds the valuesestablished for a Class A device. [ROP 1–94]

FPN: Class A ground-fault circuit interrupters trip whenthe current to ground has a value in the range of 4 mA to 6mA. For further information, see UL 943, Standard forGround-Fault Circuit Interrupters.

Ground-Fault Protection of Equipment (GFPE). A sys-tem intended to provide protection of equipment from dam-aging line-to-ground fault currents by operating to cause adisconnecting means to open all ungrounded conductors ofthe faulted circuit. This protection is provided at currentlevels less than those required to protect conductors fromdamage through the operation of a supply circuit overcur-rent device. [ROP 1–94]

Guarded. Covered, shielded, fenced, enclosed, or other-wise protected by means of suitable covers, casings, barri-ers, rails, screens, mats, or platforms to remove the likeli-hood of approach or contact by persons or objects to a pointof danger.

Guest Room. An accommodation combining living, sleep-ing, sanitary, and storage facilities within a compartment.[ROP 1–101]

Guest Suite. An accommodation with two or more con-tiguous rooms comprising a compartment, with or withoutdoors between such rooms, that provides living, sleeping,sanitary, and storage facilities. [ROP 1–101]

Hoistway. Any shaftway, hatchway, well hole, or other ver-tical opening or space in which an elevator or dumbwaiteris designed to operate.

Identified (as applied to equipment). Recognizable assuitable for the specific purpose, function, use, environ-ment, application, and so forth, where described in a par-ticular Code requirement.

FPN: Some examples of ways to determine suitability ofequipment for a specific purpose, environment, or applica-tion include investigations by a qualified testing laboratory(listing and labeling), an inspection agency, or other orga-nizations concerned with product evaluation.

In Sight From (Within Sight From, Within Sight).Where this Code specifies that one equipment shall be “insight from,” “within sight from,” or “within sight,” and soforth, of another equipment, the specified equipment is tobe visible and not more than 15 m (50 ft) distant from theother.

Interrupting Rating. The highest current at rated voltagethat a device is intended to interrupt under standard testconditions.

FPN: Equipment intended to interrupt current at other thanfault levels may have its interrupting rating implied in otherratings, such as horsepower or locked rotor current.

Isolated (as applied to location). Not readily accessibleto persons unless special means for access are used.

Kitchen. An area used, or designated to be used, for thepreparation of food. [ROP 1–114]

Labeled. Equipment or materials to which has been at-tached a label, symbol, or other identifying mark of anorganization that is acceptable to the authority having juris-diction and concerned with product evaluation, that main-tains periodic inspection of production of labeled equip-ment or materials, and by whose labeling the manufacturerindicates compliance with appropriate standards or perfor-mance in a specified manner.

Lighting Outlet. An outlet intended for the direct connec-tion of a lampholder, a luminaire (lighting fixture), or apendant cord terminating in a lampholder.

Listed. Equipment, materials, or services included in a listpublished by an organization that is acceptable to the au-thority having jurisdiction and concerned with evaluationof products or services, that maintains periodic inspectionof production of listed equipment or materials or periodicevaluation of services, and whose listing states that the



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equipment, material, or services either meets appropriatedesignated standards or has been tested and found suitablefor a specified purpose.

FPN: The means for identifying listed equipment mayvary for each organization concerned with product evalua-tion, some of which do not recognize equipment as listedunless it is also labeled. Use of the system employed by thelisting organization allows the authority having jurisdictionto identify a listed product.

Live Parts. Energized conductive components.

Location, Damp. Locations protected from weather andnot subject to saturation with water or other liquids butsubject to moderate degrees of moisture. Examples of suchlocations include partially protected locations under cano-pies, marquees, roofed open porches, and like locations,and interior locations subject to moderate degrees of mois-ture, such as some basements, some barns, and some cold-storage warehouses.

Location, Dry. A location not normally subject to damp-ness or wetness. A location classified as dry may be tem-porarily subject to dampness or wetness, as in the case of abuilding under construction.

Location, Wet. Installations under ground or in concreteslabs or masonry in direct contact with the earth; in loca-tions subject to saturation with water or other liquids, suchas vehicle washing areas; and in unprotected locations ex-posed to weather.

Luminaire. A complete lighting unit consisting of a lampor lamps together with the parts designed to distribute thelight, to position and protect the lamps and ballast (whereapplicable), and to connect the lamps to the power supply.

Metal-Enclosed Power Switchgear. A switchgear assem-bly completely enclosed on all sides and top with sheetmetal (except for ventilating openings and inspection win-dows) containing primary power circuit switching, inter-rupting devices, or both, with buses and connections. Theassembly may include control and auxiliary devices. Accessto the interior of the enclosure is provided by doors, remov-able covers, or both.

Motor Control Center. An assembly of one or more en-closed sections having a common power bus and princi-pally containing motor control units.

Multioutlet Assembly. A type of surface, flush, or free-standing raceway designed to hold conductors and recep-tacles, assembled in the field or at the factory.

Neutral Conductor. A conductor, other than a groundingconductor, that is connected to the common point of a wyeconnection in a polyphase system or the point of a sym-metrical system that is normally at zero voltage. [ROP1–122]

Nonautomatic. Action requiring personal intervention forits control. As applied to an electric controller, nonauto-matic control does not necessarily imply a manual control-ler, but only that personal intervention is necessary.[ROP 1–123]

Nonlinear Load. A load where the wave shape of thesteady-state current does not follow the wave shape of theapplied voltage.

FPN: Electronic equipment, electronic/electric-dischargelighting, adjustable-speed drive systems, and similar equip-ment may be nonlinear loads.

Outlet. A point on the wiring system at which current istaken to supply utilization equipment.

Outline Lighting. An arrangement of lighting equipmentto outline or call attention to certain features such as theshape of a building or the decoration of a window. [ROP1–125]

Overcurrent. Any current in excess of the rated currentof equipment or the ampacity of a conductor. It may resultfrom overload, short circuit, or ground fault.

FPN: A current in excess of rating may be accommodatedby certain equipment and conductors for a given set ofconditions. Therefore the rules for overcurrent protectionare specific for particular situations.

Overload. Operation of equipment in excess of normal,full-load rating, or of a conductor in excess of rated ampac-ity that, when it persists for a sufficient length of time,would cause damage or dangerous overheating. A fault,such as a short circuit or ground fault, is not an overload.

Panelboard. A single panel or group of panel units de-signed for assembly in the form of a single panel, includingbuses and automatic overcurrent devices, and equippedwith or without switches for the control of light, heat, orpower circuits; designed to be placed in a cabinet or cutoutbox placed in or against a wall, partition, or other support;and accessible only from the front.

Plenum. A compartment or chamber to which one ormore air ducts are connected and that forms part of the airdistribution system.

Power Outlet. An enclosed assembly that may includereceptacles, circuit breakers, fuseholders, fused switches,buses, and watt-hour meter mounting means; intended tosupply and control power to mobile homes, recreationalvehicles, park trailers, or boats or to serve as a means fordistributing power required to operate mobile or tempo-rarily installed equipment.

Premises Wiring (System). That interior and exteriorwiring, including power, lighting, control, and signal circuitwiring together with all their associated hardware, fittings,and wiring devices, both permanently and temporarily in-stalled, that extends from the service point or source ofpower, such as a battery, a solar photovoltaic system, or a



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generator, transformer, or converter windings, to the out-let(s). Such wiring does not include wiring internal to ap-pliances, luminaires (fixtures), motors, controllers, motorcontrol centers, and similar equipment.

Qualified Person. One who has skills and knowledge re-lated to the construction and operation of the electricalequipment and installations and has received safety trainingon the hazards involved.

FPN: Examples of this safety training include, but are notlimited to, training in the use of special precautionary tech-niques, personal protective equipment, insulating andshielding materials, and insulated tools and test equipmentwhen working on or near exposed conductors and or circuitparts that are or can become energized. [ROP 1–130]

Raceway. An enclosed channel of metal or nonmetallicmaterials designed expressly for holding wires, cables, orbusbars, with additional functions as permitted in thisCode. Raceways include, but are not limited to, rigid metalconduit, rigid nonmetallic conduit, intermediate metal con-duit, liquidtight flexible conduit, flexible metallic tubing,flexible metal conduit, electrical nonmetallic tubing, elec-trical metallic tubing, underfloor raceways, cellular con-crete floor raceways, cellular metal floor raceways, surfaceraceways, wireways, and busways.

Rainproof. Constructed, protected, or treated so as to pre-vent rain from interfering with the successful operation ofthe apparatus under specified test conditions.

Raintight. Constructed or protected so that exposure to abeating rain will not result in the entrance of water underspecified test conditions.

Receptacle. A receptacle is a contact device installed atthe outlet for the connection of an attachment plug. A singlereceptacle is a single contact device with no other contactdevice on the same yoke. A multiple receptacle is two ormore contact devices on the same yoke.

Receptacle Outlet. An outlet where one or more recep-tacles are installed.

Remote-Control Circuit. Any electric circuit that con-trols any other circuit through a relay or an equivalent de-vice.

Sealable Equipment. Equipment enclosed in a case orcabinet that is provided with a means of sealing or lockingso that live parts cannot be made accessible without open-ing the enclosure. The equipment may or may not be oper-able without opening the enclosure.

Separately Derived System. A premises wiring systemwhose power is derived from a source of electric energyother than a service. Such systems have no direct electricalconnection, including a solidly connected grounded circuitconductor, to supply conductors originating in another sys-tem. [ROP 1–132]

Service. The conductors and equipment for deliveringelectric energy from the serving utility to the wiring systemof the premises served.

Service Cable. Service conductors made up in the formof a cable.

Service Conductors. The conductors from the servicepoint to the service disconnecting means.

Service Drop. The overhead service conductors from thelast pole or other aerial support to and including the splices,if any, connecting to the service-entrance conductors at thebuilding or other structure.

Service-Entrance Conductors, Overhead System. Theservice conductors between the terminals of the serviceequipment and a point usually outside the building, clear ofbuilding walls, where joined by tap or splice to the servicedrop.

Service-Entrance Conductors, Underground System.The service conductors between the terminals of the serviceequipment and the point of connection to the service lateral.

FPN: Where service equipment is located outside thebuilding walls, there may be no service-entrance conduc-tors, or they may be entirely outside the building.

Service Equipment. The necessary equipment, usuallyconsisting of a circuit breaker(s) or switch(es) and fuse(s)and their accessories, connected to the load end of serviceconductors to a building or other structure, or an otherwisedesignated area, and intended to constitute the main controland cutoff of the supply.

Service Lateral. The underground service conductors be-tween the street main, including any risers at a pole or otherstructure or from transformers, and the first point of con-nection to the service-entrance conductors in a terminal boxor meter or other enclosure, inside or outside the buildingwall. Where there is no terminal box, meter, or other enclo-sure, the point of connection is considered to be the point ofentrance of the service conductors into the building.

Service Point. The point of connection between the fa-cilities of the serving utility and the premises wiring.

Show Window. Any window used or designed to be usedfor the display of goods or advertising material, whether itis fully or partly enclosed or entirely open at the rear andwhether or not it has a platform raised higher than the streetfloor level.

Signaling Circuit. Any electric circuit that energizes sig-naling equipment.

Solar Photovoltaic System. The total components andsubsystems that, in combination, convert solar energy intoelectrical energy suitable for connection to a utilizationload.

Special Permission. The written consent of the authorityhaving jurisdiction.



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Structure. That which is built or constructed.

Supplementary Overcurrent Protective Device. A de-vice intended to provide limited overcurrent protection forspecific applications and utilization equipment such as lu-minaires (lighting fixtures) and appliances. This limitedprotection is in addition to the protection provided in therequired branch circuit by the branch circuit overcurrentprotective device. [ROP 1–138]

Switch, Bypass Isolation. A manually operated deviceused

contents · contents article 90 240introduction ..... 70– 1 chapter 1 general 100 ... 2005...

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