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90 Introduction ........................................ 70– 9

Chapter 1 General

100 Definitions ......................................... 70– 12

I. General ...................................... 70– 12II. Over 600 Volts, Nominal ................. 70– 19

110 Requirements for Electrical Installations ..... 70– 20

I. General ...................................... 70– 20II. 600 Volts, Nominal, or Less ............. 70– 25

III. Over 600 Volts, Nominal ................. 70– 27IV. Tunnel Installations over 600 Volts,

Nominal ...................................... 70– 29V. Manholes and Other Electric

Enclosures Intended for PersonnelEntry, All Voltages ......................... 70– 30

Chapter 2 Wiring and Protection

200 Use and Identification of GroundedConductors .......................................... 70– 32

210 Branch Circuits ................................... 70– 34

I. General Provisions ........................ 70– 34II. Branch-Circuit Ratings ................... 70– 38

III. Required Outlets ........................... 70– 40

215 Feeders ............................................. 70– 44

220 Branch-Circuit, Feeder, and ServiceCalculations ........................................ 70– 47

I. General ...................................... 70– 47II. Branch-Circuit Load Calculations ...... 70– 47

III. Feeder and Service LoadCalculations ................................. 70– 50

IV. Optional Feeder and Service LoadCalculations ................................. 70– 53

V. Farm Load Calculation .................. 70– 56

225 Outside Branch Circuits and Feeders ......... 70– 57

I. General ...................................... 70– 57II. More Than One Building or Other

Structure ..................................... 70– 59III. Over 600 Volts ............................. 70– 62

230 Services ............................................ 70– 63

I. General ...................................... 70– 63II. Overhead Service-Drop Conductors .... 70– 64

III. Underground Service-LateralConductors .................................. 70– 65

IV. Service-Entrance Conductors ............ 70– 65V. Service Equipment — General .......... 70– 68

VI. Service Equipment —Disconnecting Means ...................... 70– 68

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

VIII. Services Exceeding 600 Volts,Nominal ...................................... 70– 71

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240 Overcurrent Protection ........................... 70– 72

I. General ...................................... 70– 72II. Location. [ROP 10–16] ................... 70– 76

III. Enclosures .................................. 70– 79IV. Disconnecting and Guarding ............ 70– 80V. Plug Fuses, Fuseholders, and

Adapters ..................................... 70– 80VI. Cartridge Fuses and Fuseholders ....... 70– 81

VII. Circuit Breakers ........................... 70– 81VIII. Supervised Industrial Installations ...... 70– 82

IX. Overcurrent Protection Over 600Volts, Nominal .............................. 70– 84

250 Grounding and Bonding ......................... 70– 84

I. General ...................................... 70– 84II. System Grounding ........................ 70– 88

III. Grounding Electrode System andGrounding Electrode Conductor ......... 70– 95

IV. Enclosure, Raceway, and ServiceCable Connections [ROP 5–61] ......... 70– 99

V. Bonding ..................................... 70– 99VI. Equipment Grounding and

Equipment Grounding Conductors ...... 70–103VII. Methods of Equipment Grounding ..... 70–107

VIII. Direct-Current Systems ................... 70–110IX. Instruments, Meters, and Relays ........ 70–111X. Grounding of Systems and Circuits

of 1 kV and Over (High Voltage) ....... 70–111

280 Surge Arresters, Over 1 kV [ROP 5–335] .... 70–113

I. General ...................................... 70–113II. Installation .................................. 70–114

III. Connecting Surge Arresters .............. 70–114

285 Surge-Protective Devices (SPDs), 1 kV orLess [ROP 5–349] ................................. 70–115


III. Connecting SPDs. [ROP 5–349] ........ 70–115

Chapter 3 Wiring Methods and Materials

300 Wiring Methods ................................... 70–117

I. General Requirements .................... 70–117II. Requirements for Over 600 Volts,

Nominal ...................................... 70–126

310 Conductors for General Wiring ................ 70–128

312 Cabinets, Cutout Boxes, and Meter SocketEnclosures .......................................... 70–155

I. Installation .................................. 70–155II. Construction Specifications .............. 70–156

314 Outlet, Device, Pull, and Junction Boxes;Conduit Bodies; Fittings; and HandholeEnclosures .......................................... 70–158

I. Scope and General ........................ 70–158II. Installation .................................. 70–159

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III. Construction Specifications .............. 70–165IV. Pull and Junction Boxes for Use on

Systems Over 600 Volts, Nominal ...... 70–166

320 Armored Cable: Type AC ....................... 70–167


III. Construction Specifications .............. 70–168

322 Flat Cable Assemblies: Type FC ............... 70–168


III. Construction ................................ 70–169

324 Flat Conductor Cable: Type FCC .............. 70–169



326 Integrated Gas Spacer Cable: Type IGS ...... 70–171



328 Medium Voltage Cable: Type MV ............. 70–172



330 Metal-Clad Cable: Type MC .................... 70–173



332 Mineral-Insulated, Metal-Sheathed Cable:Type MI ............................................. 70–175



334 Nonmetallic-Sheathed Cable: Types NM,NMC, and NMS ................................... 70–176



336 Power and Control Tray Cable: Type TC .... 70–179



338 Service-Entrance Cable: Types SE andUSE .................................................. 70–180



340 Underground Feeder and Branch-CircuitCable: Type UF .................................... 70–181


ARTICLE


342 Intermediate Metal Conduit: Type IMC ...... 70–182



344 Rigid Metal Conduit: Type RMC .............. 70–184



348 Flexible Metal Conduit: Type FMC ........... 70–186


350 Liquidtight Flexible Metal Conduit: TypeLFMC ............................................... 70–188



352 Rigid Polyvinyl Chloride Conduit: TypePVC [ROP 8–53] .................................. 70–189



353 High Density Polyethylene Conduit: TypeHDPE Conduit ..................................... 70–192



354 Nonmetallic Underground Conduit withConductors: Type NUCC ........................ 70–193



355 Reinforced Thermosetting Resin Conduit:Type RTRC [ROP 8–78] ......................... 70–195



356 Liquidtight Flexible Nonmetallic Conduit:Type LFNC ......................................... 70–197



358 Electrical Metallic Tubing: Type EMT ........ 70–199



360 Flexible Metallic Tubing: Type FMT ......... 70–201



362 Electrical Nonmetallic Tubing: Type ENT ... 70–202


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366 Auxiliary Gutters ................................. 70–204



368 Busways ............................................ 70–206

I. General Requirements .................... 70–206II. Installation .................................. 70–206

III. Construction ................................ 70–208IV. Requirements for Over 600 Volts,

Nominal ...................................... 70–208

370 Cablebus ........................................... 70–209

372 Cellular Concrete Floor Raceways ............ 70–210

374 Cellular Metal Floor Raceways ................ 70–211


376 Metal Wireways ................................... 70–212



378 Nonmetallic Wireways ........................... 70–213



380 Multioutlet Assembly ............................ 70–214

382 Nonmetallic Extensions .......................... 70–215


III. Construction Specifications(Concealable NonmetallicExtensions only) [ROP 7–98] ............ 70–216

384 Strut-Type Channel Raceway ................... 70–217



386 Surface Metal Raceways ........................ 70–218



388 Surface Nonmetallic Raceways ................ 70–219



390 Underfloor Raceways ............................ 70–220

392 Cable Trays ........................................ 70–221

I. General [ROP 8–180] ..................... 70–221II. Installation [ROP 8–180] ................. 70–221


ARTICLE

394 Concealed Knob-and-Tube Wiring ............. 70–228



396 Messenger Supported Wiring ................... 70–229


398 Open Wiring on Insulators ...................... 70–230



Chapter 4 Equipment for General Use

400 Flexible Cords and Cables ...................... 70–233

I. General ...................................... 70–233II. Construction Specifications .............. 70–243

III. Portable Cables Over 600 Volts,Nominal ...................................... 70–244

402 Fixture Wires ...................................... 70–244

404 Switches ............................................ 70–249


406 Receptacles, Cord Connectors, andAttachment Plugs (Caps) ......................... 70–252

408 Switchboards and Panelboards ................. 70–255

I. General ...................................... 70–255II. Switchboards ............................... 70–256

III. Panelboards ................................. 70–257IV. Construction Specifications .............. 70–258

409 Industrial Control Panels ........................ 70–259



410 Luminaires, Lampholders, and Lamps ........ 70–261

I. General ...................................... 70–261II. Luminaire Locations [ROP 18-70] ..... 70–262

III. Provisions at Luminaire OutletBoxes, Canopies, and Pans ............... 70–263

IV. Luminaire Supports ....................... 70–264V. Grounding .................................. 70–264

VI. Wiring of Luminaires ..................... 70–265VII. Construction of Luminaires .............. 70–267

VIII. Installation of Lampholders .............. 70–268IX. Construction of Lampholders ............ 70–268X. Lamps and Auxiliary Equipment ....... 70–268

XI. Special Provisions for Flush andRecessed Luminaires ...................... 70–268

XII. Construction of Flush and RecessedLuminaires [ROP 18-43] ................. 70–269

XIII. Special Provisions forElectric-Discharge Lighting Systemsof 1000 Volts or Less ...................... 70–269

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XIV. Special Provisions forElectric-Discharge Lighting Systemsof More Than 1000 Volts ................. 70–270

XV. Lighting Track ............................. 70–271XVI. Decorative Lighting and Similar

Accessories .................................. 70–272

411 Lighting Systems Operating at 30 Volts orLess .................................................. 70–272

422 Appliances ......................................... 70–273


III. Disconnecting Means ..................... 70–276IV. Construction ................................ 70–276V. Marking ..................................... 70–278

424 Fixed Electric Space-Heating Equipment ..... 70–278


III. Control and Protection of FixedElectric Space-Heating Equipment ...... 70–279

IV. Marking of Heating Equipment ......... 70–281V. Electric Space-Heating Cables .......... 70–281

VI. Duct Heaters ............................... 70–283VII. Resistance-Type Boilers .................. 70–283

VIII. Electrode-Type Boilers ................... 70–284IX. Electric Radiant Heating Panels and

Heating Panel Sets ......................... 70–285

426 Fixed Outdoor Electric Deicing andSnow-Melting Equipment ........................ 70–287


III. Resistance Heating Elements ............ 70–288IV. Impedance Heating ........................ 70–289V. Skin-Effect Heating ....................... 70–289

VI. Control and Protection .................... 70–289

427 Fixed Electric Heating Equipment forPipelines and Vessels ............................. 70–290


III. Resistance Heating Elements ............ 70–291IV. Impedance Heating ........................ 70–292V. Induction Heating ......................... 70–292

VI. Skin-Effect Heating ....................... 70–292VII. Control and Protection .................... 70–293

430 Motors, Motor Circuits, and Controllers ...... 70–293

I. General ...................................... 70–293II. Motor Circuit Conductors ................ 70–299

III. Motor and Branch-Circuit OverloadProtection .................................... 70–301

IV. Motor Branch-Circuit Short-Circuitand Ground-Fault Protection ............. 70–305

V. Motor Feeder Short-Circuit andGround-Fault Protection ................... 70–308

VI. Motor Control Circuits ................... 70–308VII. Motor Controllers ......................... 70–310

VIII. Motor Control Centers .................... 70–312IX. Disconnecting Means ..................... 70–313X. Adjustable-Speed Drive Systems ....... 70–316

ARTICLE

XI. Over 600 Volts, Nominal ................. 70–317XII. Protection of Live Parts — All

Voltages ...................................... 70–317XIII. Grounding — All Voltages ............... 70–318XIV. Tables ........................................ 70–319

440 Air-Conditioning and RefrigeratingEquipment .......................................... 70–323

I. General ...................................... 70–323II. Disconnecting Means ..................... 70–325

III. Branch-Circuit Short-Circuit andGround-Fault Protection ................... 70–326

IV. Branch-Circuit Conductors ............... 70–327V. Controllers for Motor-Compressors .... 70–328

VI. Motor-Compressor andBranch-Circuit Overload Protection ..... 70–328

VII. Provisions for Room AirConditioners ................................. 70–329

445 Generators ......................................... 70–330

450 Transformers and Transformer Vaults(Including Secondary Ties) ...................... 70–331

I. General Provisions ........................ 70–331II. Specific Provisions Applicable to

Different Types of Transformers ......... 70–336III. Transformer Vaults ........................ 70–337

455 Phase Converters ................................. 70–339

I. General ...................................... 70–339II. Specific Provisions Applicable to

Different Types of Phase Converters .... 70–340

460 Capacitors .......................................... 70–340

I. 600 Volts, Nominal, and Under ......... 70–340II. Over 600 Volts, Nominal ................. 70–341

470 Resistors and Reactors ........................... 70–342

I. 600 Volts, Nominal, and Under ......... 70–342II. Over 600 Volts, Nominal ................. 70–342

480 Storage Batteries .................................. 70–343

490 Equipment, Over 600 Volts, Nominal ......... 70–344

I. General ...................................... 70–344II. Equipment — Specific Provisions ...... 70–344

III. Equipment — Metal-EnclosedPower Switchgear and IndustrialControl Assemblies ........................ 70–346

IV. Mobile and Portable Equipment ........ 70–349V. Electrode-Type Boilers ................... 70–350

Chapter 5 Special Occupancies

500 Hazardous (Classified) Locations, ClassesI, II, and III, Divisions 1 and 2 ................. 70–351

501 Class I Locations ................................. 70–360

I. General ...................................... 70–360II. Wiring ....................................... 70–360

III. Equipment .................................. 70–365

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502 Class II Locations ................................ 70–370


III. Equipment .................................. 70–372

503 Class III Locations ............................... 70–376


III. Equipment .................................. 70–377

504 Intrinsically Safe Systems ....................... 70–379

505 Class I, Zone 0, 1, and 2 Locations ........... 70–382

506 Zone 20, 21, and 22 Locations forCombustible Dusts or IgnitibleFibers/Flyings [ROP 14–1a] ..................... 70–396

510 Hazardous (Classified) Locations —Specific .............................................. 70–403

511 Commercial Garages, Repair and Storage .... 70–403

513 Aircraft Hangars .................................. 70–405

514 Motor Fuel Dispensing Facilities .............. 70–408

515 Bulk Storage Plants .............................. 70–412

516 Spray Application, Dipping, and CoatingProcesses ............................................ 70–417

517 Health Care Facilities ............................ 70–423

I. General ...................................... 70–423II. Wiring and Protection .................... 70–425

III. Essential Electrical System .............. 70–428IV. Inhalation Anesthetizing Locations ..... 70–435V. X-Ray Installations ........................ 70–438

VI. Communications, SignalingSystems, Data Systems, Fire AlarmSystems, and Systems Less Than120 Volts, Nominal ........................ 70–439

VII. Isolated Power Systems .................. 70–440

518 Assembly Occupancies .......................... 70–441

519 Control Systems for PermanentAmusement Attractions ........................... 70–442

I. General. ..................................... 70–442II. Control Circuits. ........................... 70–443

III. Control Circuit Wiring Methods. ....... 70–443

520 Theaters, Audience Areas of MotionPicture and Television Studios,Performance Areas, and Similar Locations ... 70–444

I. General ...................................... 70–444II. Fixed Stage Switchboards ................ 70–446

III. Fixed Stage Equipment Other ThanSwitchboards ................................ 70–447

IV. Portable Switchboards on Stage ........ 70–448V. Portable Stage Equipment Other

Than Switchboards ......................... 70–451VI. Dressing Rooms ........................... 70–453

VII. Grounding .................................. 70–453

ARTICLE

525 Carnivals, Circuses, Fairs, and SimilarEvents ............................................... 70–453

I. General Requirements .................... 70–453II. Power Sources ............................. 70–454

III. Wiring Methods ............................ 70–454IV. Grounding and Bonding .................. 70–455

530 Motion Picture and Television Studiosand Similar Locations ............................ 70–455

I. General ...................................... 70–455II. Stage or Set ................................ 70–456

III. Dressing Rooms ........................... 70–458IV. Viewing, Cutting, and Patching

Tables ........................................ 70–458V. Cellulose Nitrate Film Storage

Vaults ......................................... 70–458VI. Substations .................................. 70–459

540 Motion Picture Projection Rooms ............. 70–459

I. General ...................................... 70–459II. Equipment and Projectors of the

Professional Type .......................... 70–459III. Nonprofessional Projectors .............. 70–460IV. Audio Signal Processing,

Amplification, and ReproductionEquipment ................................... 70–460

545 Manufactured Buildings ......................... 70–460

547 Agricultural Buildings ........................... 70–461

550 Mobile Homes, Manufactured Homes, andMobile Home Parks ............................... 70–464

I. General ...................................... 70–464II. Mobile and Manufactured Homes ...... 70–465

III. Services and Feeders ...................... 70–472

551 Recreational Vehicles and RecreationalVehicle Parks ....................................... 70–474

I. General ...................................... 70–474II. Combination Electrical Systems ........ 70–475

III. Other Power Sources ..................... 70–476IV. Nominal 120-Volt or 120/240-Volt

Systems ...................................... 70–477V. Factory Tests ............................... 70–484

VI. Recreational Vehicle Parks ............... 70–484

552 Park Trailers ....................................... 70–486

I. General ...................................... 70–486II. Low-Voltage Systems ..................... 70–487

III. Combination Electrical Systems ........ 70–488IV. Nominal 120-Volt or 120/240-Volt

Systems ...................................... 70–488V. Factory Tests ............................... 70–495

553 Floating Buildings ................................ 70–496

I. General ...................................... 70–496II. Services and Feeders ...................... 70–496

III. Grounding .................................. 70–496

555 Marinas and Boatyards .......................... 70–497

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585 Critical Operations Power Systems(COPS) [ROP 20-1] ............................... 70–500

I. General ...................................... 70–500II. Circuit Wiring and Equipment .......... 70–502

III. Power Sources and Connection ......... 70–503IV. Overcurrent Protection .................... 70–504V. System Performance and Analysis ...... 70–505

590 Temporary Installations .......................... 70–505

Chapter 6 Special Equipment

600 Electric Signs and Outline Lighting ........... 70–508

I. General ...................................... 70–508II. Field-Installed Skeleton Tubing and

Wiring [ROP 18–141] ..................... 70–512

604 Manufactured Wiring Systems ................. 70–513

605 Office Furnishings (Consisting of LightingAccessories and Wired Partitions) .............. 70–514

610 Cranes and Hoists ................................ 70–516


III. Contact Conductors ....................... 70–519IV. Disconnecting Means ..................... 70–519V. Overcurrent Protection .................... 70–520

VI. Control ...................................... 70–521VII. Grounding .................................. 70–521

620 Elevators, Dumbwaiters, Escalators,Moving Walks, Platform Lifts, andStairway Chairlifts [ROP 12–17] ............... 70–521

I. General ...................................... 70–521II. Conductors .................................. 70–523

III. Wiring ....................................... 70–525IV. Installation of Conductors ................ 70–527V. Traveling Cables ........................... 70–528

VI. Disconnecting Means and Control ...... 70–529VII. Overcurrent Protection .................... 70–530

VIII. Machine Rooms, Control Rooms,Machinery Spaces, and ControlSpaces ........................................ 70–531

IX. Grounding .................................. 70–531X. Emergency and Standby Power

Systems ...................................... 70–532

625 Electric Vehicle Charging System ............. 70–532

I. General ...................................... 70–532II. Wiring Methods ............................ 70–533

III. Equipment Construction .................. 70–533IV. Control and Protection .................... 70–534V. Electric Vehicle Supply Equipment

Locations .................................... 70–534

626 Electrified Truck Parking SpaceEquipment [ROP 12–81] ......................... 70–536

I. Electrified Truck Parking SpaceElectrical Wiring Systems ................ 70–537

II. Electrified Truck Parking SpaceSupply Equipment (Off-Board) .......... 70–538

ARTICLE

III. Transportation Refrigerated Units(TRU) ........................................ 70–541

630 Electric Welders ................................... 70–542

I. General ...................................... 70–542II. Arc Welders ................................ 70–543

III. Resistance Welders ........................ 70–544IV. Welding Cable ............................. 70–545

640 Audio Signal Processing, Amplification,and Reproduction Equipment .................... 70–545

I. General ...................................... 70–545II. Permanent Audio System

Installations .................................. 70–548III. Portable and Temporary Audio

System Installations ........................ 70–549

645 Information Technology Equipment ........... 70–550

647 Sensitive Electronic Equipment ................ 70–552

650 Pipe Organs ........................................ 70–554

660 X-Ray Equipment ................................ 70–554

I. General ...................................... 70–554II. Control ...................................... 70–556

III. Transformers and Capacitors ............ 70–556IV. Guarding and Grounding ................. 70–556

665 Induction and Dielectric HeatingEquipment .......................................... 70–556

I. General ...................................... 70–556II. Guarding, Grounding, and Labeling .... 70–557

668 Electrolytic Cells ................................. 70–558

669 Electroplating ...................................... 70–561

670 Industrial Machinery ............................. 70–561

675 Electrically Driven or ControlledIrrigation Machines ............................... 70–563

I. General ...................................... 70–563II. Center Pivot Irrigation Machines ....... 70–565

680 Swimming Pools, Fountains, and SimilarInstallations ......................................... 70–565

I. General ...................................... 70–565II. Permanently Installed Pools ............. 70–568

III. Storable Pools .............................. 70–575IV. Spas and Hot Tubs ........................ 70–576V. Fountains .................................... 70–578

VI. Pools and Tubs for Therapeutic Use ... 70–580VII. Hydromassage Bathtubs .................. 70–580

682 Natural and Artificially Made Bodies ofWater ................................................ 70–581


III. Grounding and Bonding .................. 70–582

685 Integrated Electrical Systems ................... 70–583

I. General ...................................... 70–583II. Orderly Shutdown ......................... 70–583

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690 Solar Photovoltaic Systems ..................... 70–583

I. General ...................................... 70–583II. Circuit Requirements ..................... 70–586

III. Disconnecting Means ..................... 70–588IV. Wiring Methods ............................ 70–590V. Grounding .................................. 70–591

VI. Marking ..................................... 70–593VII. Connection to Other Sources ............ 70–593

VIII. Storage Batteries ........................... 70–595IX. Systems Over 600 Volts .................. 70–596

692 Fuel Cell Systems ................................ 70–596

I. General ...................................... 70–596II. Circuit Requirements ..................... 70–597

III. Disconnecting Means ..................... 70–597IV. Wiring Methods ............................ 70–598V. Grounding .................................. 70–598

VI. Marking ..................................... 70–598VII. Connection to Other Circuits ............ 70–598

VIII. Outputs Over 600 Volts .................. 70–599

695 Fire Pumps ......................................... 70–599

Chapter 7 Special Conditions

700 Emergency Systems .............................. 70–604

I. General ...................................... 70–604II. Circuit Wiring .............................. 70–605

III. Sources of Power .......................... 70–606IV. Emergency System Circuits for

Lighting and Power ........................ 70–608V. Control — Emergency Lighting

Circuits ....................................... 70–608VI. Overcurrent Protection .................... 70–609

701 Legally Required Standby Systems ............ 70–609


III. Sources of Power .......................... 70–610IV. Overcurrent Protection .................... 70–612

702 Optional Standby Systems ...................... 70–612


III. Grounding .................................. 70–613IV. Sources of Power .......................... 70–613

705 Interconnected Electric Power ProductionSources [ROP 13–184] ........................... 70–613

I General ...................................... 70–613II Utility-Interactive Inverters .............. 70–616

III Generators .................................. 70–617

720 Circuits and Equipment Operating at LessThan 50 Volts ...................................... 70–617

725 Class 1, Class 2, and Class 3Remote-Control, Signaling, andPower-Limited Circuits ........................... 70–617

I. General ...................................... 70–617II. Class 1 Circuits ............................ 70–619

III. Class 2 and Class 3 Circuits ............. 70–621

ARTICLE

IV. Listing Requirements ..................... 70–625

727 Instrumentation Tray Cable: Type ITC ........ 70–627

760 Fire Alarm Systems .............................. 70–628

I. General ...................................... 70–628II. Non–Power-Limited Fire Alarm

(NPLFA) Circuits .......................... 70–629III. Power-Limited Fire Alarm (PLFA)

Circuits ....................................... 70–631IV. Listing Requirements ..................... 70–634

770 Optical Fiber Cables and Raceways ........... 70–637

I. General ...................................... 70–637II. Cables Outside and Entering

Buildings. [ROP 16–2] .................... 70–638III. Protection [ROP 16–25] .................. 70–638IV. Grounding Methods [ROP 16–25] ...... 70–639V. Installation Methods Within

Buildings [ROP 16–38] ................... 70–640VI. Listing Requirements [ROP 6–2] ....... 70–641

Chapter 8 Communications Systems

800 Communications Circuits ........................ 70–644

I. General ...................................... 70–644II. Wires and Cables Outside and

Entering Buildings ......................... 70–645III. Protection ................................... 70–646IV. Grounding Methods ....................... 70–648V. Installation Methods Within

Buildings [ROP 16–172] ................. 70–649VI. Listing Requirements ..................... 70–652

810 Radio and Television Equipment ............... 70–654

I. General ...................................... 70–654II. Receiving Equipment — Antenna

Systems ...................................... 70–654III. Amateur Transmitting and

Receiving Stations — AntennaSystems ...................................... 70–657

IV. Interior Installation — TransmittingStations ....................................... 70–657

820 Community Antenna Television and RadioDistribution Systems .............................. 70–658

I. General ...................................... 70–658II. Coaxial Cables Outside and

Entering Buildings [ROP 16-281] ....... 70–659III. Protection ................................... 70–660IV. Grounding Methods ....................... 70–661V. Installation Methods Within

Buildings [ROP 16–238] ................. 70–662VI. Listing Requirements ..................... 70–664

830 Network-Powered BroadbandCommunications Systems ........................ 70–665

I. General ...................................... 70–665II. Cables Outside and Entering

Buildings ..................................... 70–667III. Protection ................................... 70–670IV. Grounding Methods ....................... 70–671

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V. Installation Methods WithinBuildings [ROP 16–405] .................. 70–672

VI. Listing Requirements ..................... 70–674TABLES

Chapter 9 Tables

1 Percent of Cross Section of Conduit andTubing for Conductors ........................... 70–676

2 Radius of Conduit and Tubing Bends ......... 70–676

4 Dimensions and Percent Area of Conduitand Tubing(Areas of Conduit or Tubing for theCombinations of Wires Permitted in Table1, Chapter 9) ....................................... 70–677

5 Dimensions of Insulated Conductors andFixture Wires ....................................... 70–682

5A Compact Copper and Aluminum BuildingWire Nominal Dimensions and Areas[ROP 6–98] ......................................... 70–686

8 Conductor Properties ............................. 70–686

9 Alternating-Current Resistance andReactance for 600-Volt Cables, 3-Phase,60 Hz, 75°C (167°F) — Three SingleConductors in Conduit ............................ 70–688

TABLES

11(A) Class 2 and Class 3 Alternating-CurrentPower Source Limitations ........................ 70–690

11(B) Class 2 and Class 3 Direct-Current PowerSource Limitations ................................ 70–690

12(A) PLFA Alternating-Current Power SourceLimitations .......................................... 70–691

12(B) PLFA Direct-Current Power SourceLimitations .......................................... 70–692

Annex A ............................................ 70–693

Annex B ............................................ 70–696

Annex C ............................................ 70–710

Annex D ............................................ 70–780

Annex E ............................................. 70–791

Annex F ............................................. 70–793

Annex G ............................................ 70–795

Annex H ............................................ 70–796

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National Electrical Code®

2008 Edition

IMPORTANT NOTE: This NFPA document is madeavailable for use subject to important notices and legaldisclaimers. These notices and disclaimers appear in allpublications containing this document and may be foundunder the heading “Important Notices and DisclaimersConcerning NFPA Documents.” They can also be ob-tained on request from NFPA or viewed atwww.nfpa.org/disclaimers.

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 results in an installation that is essen-tially free from hazard but not necessarily efficient, conve-nient, 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 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.

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 electri-cal conductors, equipment, and raceways; signaling and

communications conductors, equipment, and raceways; andoptical fiber cables and raceways for the following:

(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 to (2):For additional information concerning such in-stallations in an industrial or multibuilding complex, seeANSI C2-2002, National Electrical Safety Code.

(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, that are not an integral part of agenerating plant, substation, or control center.

(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

(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.

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FPN to (4) and (5): Examples of utilities may include thoseentities that are typically designated or recognized by gov-ernmental law or regulation by public service/utility com-missions and that install, operate, and maintain electric sup-ply (such as generation, transmission, or distributionsystems) or communication systems (such as telephone,CATV, Internet, satellite, or data services). Utilities may besubject to compliance with codes and standards coveringtheir regulated activities as adopted under governmentallaw or regulation. Additional information can be foundthrough consultation with the appropriate governmentalbodies, such as state regulatory commissions, Federal En-ergy Regulatory Commission, and Federal Communica-tions Commission.

(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 applicable as referenced.[ROP 1-6]

Annexes are not part of the requirements of this Codebut 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 Code

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.

FPN: The format and language used in this Code followsguidelines established by NFPA and published in the NEC

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

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.

Annex C, Annex D, Annex G

Figure 90.3 Code Arrangement.

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Style 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-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 Wiring 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.

(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. SI units shall appear first, andinch-pound units shall immediately follow in parentheses.Conversion from inch-pound units to SI units shall bebased on hard conversion except as provided in 90.9(C).

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

(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.

(D) Compliance. Conversion from inch-pound units to SIunits shall be permitted to be an approximate conversion.Compliance with the numbers shown in either the SI sys-tem or the inch-pound system shall constitute compliancewith 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

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.

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.

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). An organization,office, or individual responsible for enforcing the require-ments of a code or standard, or for approving equipment,materials, an installation, or a procedure.

FPN: The phrase “authority having jurisdiction,” or itsacronym AHJ, is used in NFPA documents in a broad man-ner, since jurisdictions and approval agencies vary, as dotheir responsibilities. Where public safety is primary, theauthority having jurisdiction may be a federal, state, local,or other regional department or individual such as a firechief; fire marshal; chief of a fire prevention bureau, labordepartment, or health department; building official; electri-cal inspector; or others having statutory authority. For in-surance purposes, an insurance inspection department, rat-ing bureau, or other insurance company representative maybe the authority having jurisdiction. In many circum-stances, the property owner or his or her designated agentassumes the role of the authority having jurisdiction; atgovernment installations, the commanding officer or depart-mental official may be the authority having jurisdiction.

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.

Bonded (Bonding). Connected to establish electrical con-tinuity and conductivity. [ROP 5-2]

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.

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 be

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connected 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.

Branch-Circuit Overcurrent Device. A device capable ofproviding protection for service, feeder, and branch circuitsand equipment over the full range of overcurrents betweenits rated current and its interrupting rating. Branch-circuitovercurrent protective devices are provided with interrupt-ing ratings appropriate for the intended use but no less than5,000 amperes. [ROP 10-1a]

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

Bundled. Cables or conductors that are tied, wrapped,taped, or otherwise periodically bound together. [ROP1-19, 15–124]

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 haveany 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.

Clothes Closet. A non-habitable room or space intendedprimarily for storage of garments and apparel. [ROP 1-20]

Communications Equipment. The electronic equipmentthat performs the telecommunications operations for thetransmission of audio, video, and data, and including powerequipment (e.g., dc converters, inverters and batteries) andtechnical support equipment (e.g., computers). [ROP 16–106, 16–107]

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 circuit or equipment

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affected, accomplished by the choice of overcurrent protec-tive devices and their ratings or settings.

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.

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 carries or con-trols electric energy as its principal function. [ROP 9-7]

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, 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.

Dwelling Unit. One or more rooms arranged for complete,independent housekeeping purposes, with space for eating,living, and sleeping; facilities for cooking; and provisionsfor sanitation. [ROP 1-27]

Electric Sign. A fixed, stationary, or portable self-contained, electrically illuminated utilization equipment

with words or symbols designed to convey information orattract attention.

Electrical Power Production and Distribution Network.Power production, distribution, and utilization equipmentand facilities, such as an electric utility system that deliverelectric power to the connected loads, that is external to andnot controlled by an Interactive System. [ROC 1-28]

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 110.20 for examples of enclosure types.[ROP 1-30]

Energized. Electrically connected to, or is, a source ofvoltage.

Equipment. A general term including material, fittings, de-vices, appliances, luminaires (fixtures), apparatus, machin-ery, and the like used as a part of, or in connection with, anelectrical installation. [ROP 1-31]

Equipotential Plane. An area where wire mesh or otherconductive elements are embedded in or placed under con-crete or other conductive surface, are bonded together andto all metal structures and fixed nonelectrical equipmentthat may become energized, and are connected to the elec-trical grounding system. [ROP 5-7]

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.



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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. The earth. [ROP 5-8]

Grounded (Grounding). Connected (connecting) toground or to a conductive body that extends the groundconnection. [ROP 5-9]

[ROP 5-12]

Grounded, Solidly. Connected to ground without insertingany resistor or impedance device.

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

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.

FPN: Class A ground-fault circuit interrupters trip whenthe current to ground is 6 mA or higher and do not tripwhen the current to ground is less than 4 mA. For furtherinformation, see UL 943, Standard for Ground-Fault Cir-cuit Interrupters. [ROP 2-5]

Ground-Fault Protection of Equipment. A system in-tended to provide protection of equipment from damagingline-to-ground fault currents by operating to cause a discon-necting means to open all ungrounded conductors of thefaulted circuit. This protection is provided at current levelsless than those required to protect conductors from damagethrough the operation of a supply circuit overcurrent de-vice.

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

Grounding Conductor, Equipment (EGC). The conduc-tive path installed to connect normally non–current-carrying metal parts of equipment together and to the sys-

tem grounded conductor or to the grounding electrodeconductor. [ROP 5-6]

FPN No. 1: It is recognized that the equipment groundingconductor also performs bonding. [ROP 5-6]

FPN No. 2: See 250.118 for a list of acceptable equipmentgrounding conductors. [ROP 5-6]

Grounding Electrode. A conducting object through whicha direct connection to earth is established. [ROP 5-14]

Grounding Electrode Conductor. The conductor used toconnect the grounding electrode(s) to a system conductor orto equipment. [ROP 5-18]

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.

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.

Handhole Enclosure. An enclosure for use in undergroundsystems, provided with an open or closed bottom, and sizedto allow personnel to reach into, but not enter, for the pur-pose of installing, operating, or maintaining equipment orwiring or both. [ROP 9-3, 9-4]

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.

Interactive System. An electric power production systemthat is operating in parallel with and capable of deliveringenergy to an electric primary source supply system.



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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.

Intersystem Bonding Termination. A device that pro-vides a means of bonding communications equipment at theservice equipment or the disconnecting means for any ad-ditional buildings or structures. [ROP 5-20]

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

Kitchen. An area with a sink and permanent facilities forfood preparation and cooking. [ROP 1-36]

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 connection of alampholder, a luminaire (lighting fixture), or a pendant cordterminating in a lampholder. [ROP 1-39]

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 eitherthe equipment, material, or service meets appropriate des-ignated standards or has been tested and found suitable fora 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 lightsource such as a lamp or lamps, together with the partsdesigned to position the light source and connect it to thepower supply. It may also include parts to protect the lightsource, ballast, or distribute the light. A lampholder itself isnot a luminaire. [ROP 18-4b]

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. Metal-enclosed power switchgear isavailable in non-arc-resistant or arc-resistant constructions.[ROP 9-5]

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. The conductor connected to the neu-tral point of a system that is intended to carry current undernormal conditions. [ROP 5-36]

Neutral Point. The common point on a wye-connection ina polyphase system or midpoint on a single-phase, 3-wiresystem, or midpoint of a single-phase portion of a 3-phasedelta system, or a midpoint of a 3-wire, direct current sys-tem. [ROP 5-36]

FPN: At the neutral point of the system, the vectorial sumof the nominal voltages from all other phases within thesystem that utilize the neutral, with respect to the neutralpoint, is zero potential. [ROP 5-36]

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.

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.



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

Outline Lighting. An arrangement of incandescent lamps,electric discharge lighting, or other electrically poweredlight sources to outline or call attention to certain featuressuch as the shape of a building or the decoration of awindow.

Overcurrent. Any current in excess of the rated current ofequipment 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 or moreair ducts are connected and that forms part of the air distri-bution system.

Power Outlet. An enclosed assembly that may include re-ceptacles, 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). Interior and exterior wiring,including power, lighting, control, and signal circuit wiringtogether with all their associated hardware, fittings, andwiring devices, both permanently and temporarily installed.This includes: (a) wiring from the service point or powersource to the outlets; or (b) wiring from and including thepower source to the outlets where there is no service point.[ROP 1-43]

Such wiring does not include wiring internal to appli-ances, luminaires (fixtures), motors, controllers, motor con-trol centers, and similar equipment.

Qualified Person. One who has skills and knowledge re-lated to the construction and operation of the electrical

equipment and installations and has received safety trainingto recognize and avoid the hazards involved. [ROP 1-45]

FPN: Refer to NFPA 70E-2004, Standard for ElectricalSafety in the Workplace, for electrical safety trainingrequirements.

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 at theoutlet 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 controlsany other circuit through a relay or an equivalent device.

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 energy orequipment other than a service. Such systems have no di-rect electrical connection, including a solidly connectedgrounded circuit conductor, to supply conductors originat-ing in another system.

Service. The conductors and equipment for delivering elec-tric energy from the serving utility to the wiring system ofthe premises served.

Service Cable. Service conductors made up in the form ofa cable.

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



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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