Table Of Content

NFPA 70 ® National Electrical Code® 2011 Edition NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471 An International Codes and Standards Organization Copyright © 2010 National Fire Protection Association® One Batterymarch Park Quincy, Massachusetts 02169-7471 NFPA, National Fire Protection Association, National Electrical Code, NFPA 70, and NEC are registered trademarks of the National Fire Protection Association. IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA® DOCUMENTS Notice and Disclaimer of Liability Concerning the Use of NFPA Documents NFPA® codes, standards, recommended practices, and guides (“NFPA Documents”), of which the document contained herein is one, are developed through a consensus standards development process approved by the American National Standards Institute. This process brings together volunteers representing varied viewpoints and interests to achieve consensus on fire and other safety issues. 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For Further Information All questions or other communications relating to NFPA Documents and all requests for information on NFPA procedures governing its codes and standards development process, including information on the procedures for requesting Formal Interpretations, for proposing Tentative Interim Amendments, and for proposing revisions to NFPA documents during regular revision cycles, should be sent to NFPA headquarters, addressed to the attention of the Secretary, Standards Council, NFPA, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101; email: [email protected] For more information about NFPA, visit the NFPA website at www.nfpa.org. Copyright©2010,NationalFireProtectionAssociation®.AllRightsReserved NFPA 70® National Electrical Code® 2011 Edition This edition of NFPA 70, National Electrical Code, was prepared by the National Electrical Code Committee and acted on by NFPAat its JuneAssociation Technical Meeting held June 7–10, 2010, in Las Vegas, NV. It was issued by the Standards Council on August 5, 2010, with an effective date of August 25, 2010, and supersedes all previous editions. This edition of NFPA70 was approved as anAmerican National Standard onAugust 25, 2010. History and Development of the National Electrical Code® TheNationalFireProtectionAssociationhasactedassponsoroftheNationalElectricalCodesince 1911. The original Code document was developed in 1897 as a result of the united efforts of various insurance, electrical, architectural, and allied interests. In accordance with the provisions of the NFPA Regulations Governing Committee Projects, a NationalElectricalCodeCommitteeReportonProposalscontainingproposedamendmentstothe2008 National Electrical Code was published by NFPAin July 2009.This report recorded the actions of the variousCode-MakingPanelsandtheCorrelatingCommitteeoftheNationalElectricalCodeCommittee oneachproposalthathadbeenmadetorevisethe2008Code.Thereportwascirculatedtoallmembers of the National Electrical Code Committee and was made available to other interested NFPAmembers and to the public for review and comment. Following the close of the public comment period, the Code-Making Panels met, acted on each comment, and reported their action to the Correlating Com- mittee. NFPApublished the National Electrical Code Committee Report on Comments in March 2010, which recorded the actions of the Code-Making Panels and the Correlating Committee on each public commenttotheNationalElectricalCodeCommitteeReportonProposals.TheNationalElectricalCode CommitteeReportonProposalsandtheNationalElectricalCodeCommitteeReportonCommentswere presented to the 2010 JuneAssociation Technical Meeting for adoption. NFPAhasanElectricalSectionthatprovidesparticularopportunityforNFPAmembersinterestedin electrical safety to become better informed and to contribute to the development of the National Electrical Code and other NFPA electrical standards. At the Electrical Section Codes and Standards Review Session held at the 2010 NFPA Conference and Expo, Section members had opportunity to discuss and review the report of the National Electrical Code Committee prior to the adoption of this edition of the Code by theAssociation at its 2010 June Technical Session. This 52nd edition supersedes all other previous editions, supplements, and printings dated 1897, 1899, 1901, 1903, 1904, 1905, 1907, 1909, 1911, 1913, 1915, 1918, 1920, 1923, 1925, 1926, 1928, 1930, 1931, 1933, 1935, 1937, 1940, 1942, 1943, 1947, 1949, 1951, 1953, 1954, 1955, 1956, 1957, 1958, 1959, 1962, 1965, 1968, 1971, 1975, 1978, 1981, 1984, 1987, 1990, 1993, 1996, 1999, 2002, 2005, and 2008. ThisCodeispurelyadvisoryasfarasNFPAisconcerned.Itismadeavailableforawidevarietyof bothpublicandprivateusesintheinterestoflifeandpropertyprotection.Theseincludebothuseinlaw and for regulatory purposes, and use in private self-regulation and standardization activities such as insurance underwriting, building and facilities construction and management, and product testing and certification. NFPA70,NationalElectricalCode,NFPA,andNationalFireProtectionAssociationareregisteredtrademarksoftheNationalFireProtectionAssociation,Quincy,Massachusetts,02169. CONTENTS Contents ARTICLE ARTICLE 90 Introduction ........................................ 70– 22 IV. DisconnectingandGuarding ................ 70– 96 V. PlugFuses,Fuseholders,andAdapters ... 70– 96 VI. CartridgeFusesandFuseholders ........... 70– 97 Chapter 1General VII. CircuitBreakers ............................... 70– 97 100 Definitions ......................................... 70– 26 VIII. SupervisedIndustrialInstallations ......... 70– 98 IX. OvercurrentProtectionOver600Volts, I. General ......................................... 70– 26 Nominal ......................................... 70–100 II. Over600Volts,Nominal .................... 70– 33 250 GroundingandBonding ......................... 70–100 110 RequirementsforElectricalInstallations ..... 70– 34 I. General ......................................... 70–100 I. General ......................................... 70– 34 II. SystemGrounding ........................... 70–103 II. 600Volts,Nominal,orLess ................ 70– 37 III. GroundingElectrodeSystemand III. Over600Volts,Nominal .................... 70– 40 GroundingElectrodeConductor ............. 70–111 IV. TunnelInstallationsover600Volts, IV. Enclosure,Raceway,andService Nominal ......................................... 70– 43 CableConnections ............................. 70–116 V. ManholesandOtherElectrical V. Bonding ......................................... 70–117 EnclosuresIntendedforPersonnel VI. EquipmentGroundingandEquipment Entry,AllVoltages ............................ 70– 44 GroundingConductors ........................ 70–120 VII. MethodsofEquipmentGrounding ......... 70–125 Chapter 2 Wiring and Protection VIII. Direct-CurrentSystems ...................... 70–128 IX. Instruments,Meters,andRelays ........... 70–129 200 UseandIdentificationofGrounded X. GroundingofSystemsandCircuitsof Conductors.......................................... 70– 46 over1kV ....................................... 70–129 210 BranchCircuits ................................... 70– 48 280 SurgeArresters,Over1kV ..................... 70–131 I. GeneralProvisions ............................ 70– 48 I. General ......................................... 70–131 II. Branch-CircuitRatings ....................... 70– 52 II. Installation ..................................... 70–132 III. RequiredOutlets .............................. 70– 55 III. ConnectingSurgeArresters ................. 70–132 215 Feeders ............................................. 70– 59 285 Surge-ProtectiveDevices(SPDs),1kVor 220 Branch-Circuit,Feeder,andService Less .................................................. 70–133 Calculations ........................................ 70– 61 I. General ......................................... 70–133 I. General ......................................... 70– 61 II. Installation ..................................... 70–133 II. Branch-CircuitLoadCalculations .......... 70– 61 III. ConnectingSPDs ............................. 70–133 III. FeederandServiceLoadCalculations .... 70– 64 IV. OptionalFeederandServiceLoad Chapter 3 Wiring Methods and Materials Calculations..................................... 70– 67 V. FarmLoadCalculations .................... 70– 70 300 WiringMethods ................................... 70–135 225 OutsideBranchCircuitsandFeeders ......... 70– 71 I. GeneralRequirements ........................ 70–135 II. Requirementsforover600Volts, I. General ......................................... 70– 71 Nominal ......................................... 70–145 II. BuildingsorOtherStructuresSupplied byaFeeder(s)orBranchCircuit(s) ........ 70– 74 310 ConductorsforGeneralWiring ................ 70–147 III. Over600Volts ................................ 70– 76 I. General ......................................... 70–147 230 Services ............................................ 70– 78 II. Installation ..................................... 70–147 III. ConstructionSpecifications ................. 70–168 I. General ......................................... 70– 78 312 Cabinets,CutoutBoxes,andMeterSocket II. OverheadServiceConductors .............. 70– 79 Enclosures .......................................... 70–173 III. UndergroundServiceConductors .......... 70– 81 IV. Service-EntranceConductors ............... 70– 81 I. Installation ..................................... 70–174 V. ServiceEquipment—General ............. 70– 84 II. ConstructionSpecifications ................. 70–175 VI. ServiceEquipment—Disconnecting 314 Outlet,Device,Pull,andJunctionBoxes; Means............................................ 70– 84 ConduitBodies;Fittings;andHandhole VII. ServiceEquipment—Overcurrent Enclosures .......................................... 70–177 Protection ....................................... 70– 86 VIII. ServicesExceeding600Volts, I. ScopeandGeneral ............................ 70–177 Nominal ......................................... 70– 87 II. Installation ..................................... 70–177 III. ConstructionSpecifications ................. 70–184 240 OvercurrentProtection ........................... 70– 88 IV. PullandJunctionBoxes,Conduit I. General ......................................... 70– 88 Bodies,andHandholeEnclosuresfor II. Location ........................................ 70– 92 UseonSystemsover600Volts, III. Enclosures ...................................... 70– 95 Nominal ......................................... 70–185 70–2 NATIONALELECTRICALCODE 2011Edition CONTENTS ARTICLE ARTICLE 320 ArmoredCable:TypeAC ....................... 70–186 344 RigidMetalConduit:TypeRMC .............. 70–203 I. General ......................................... 70–186 I. General ......................................... 70–203 II. Installation ..................................... 70–186 II. Installation ..................................... 70–203 III. ConstructionSpecifications ................. 70–187 III. ConstructionSpecifications ................. 70–205 322 FlatCableAssemblies:TypeFC ............... 70–187 348 FlexibleMetalConduit:TypeFMC ........... 70–205 I. General ......................................... 70–187 I. General ......................................... 70–205 II. Installation ..................................... 70–188 II. Installation ..................................... 70–205 III. Construction ................................... 70–188 350 LiquidtightFlexibleMetalConduit:Type 324 FlatConductorCable:TypeFCC .............. 70–189 LFMC ............................................... 70–207 I. General ......................................... 70–189 I. General ......................................... 70–207 II. Installation ..................................... 70–189 II. Installation ..................................... 70–207 III. Construction ................................... 70–190 III. ConstructionSpecifications ................. 70–208 326 IntegratedGasSpacerCable:TypeIGS ...... 70–191 352 RigidPolyvinylChlorideConduit:Type PVC ................................................. 70–208 I. General ......................................... 70–191 II. Installation ..................................... 70–191 I. General ......................................... 70–208 III. ConstructionSpecifications ................. 70–191 II. Installation ..................................... 70–208 III. ConstructionSpecifications ................. 70–210 328 MediumVoltageCable:TypeMV ............. 70–192 353 HighDensityPolyethyleneConduit:Type I. General ......................................... 70–192 HDPEConduit ..................................... 70–211 II. Installation ..................................... 70–192 III. ConstructionSpecifications ................. 70–192 I. General ......................................... 70–211 II. Installation ..................................... 70–211 330 Metal-CladCable:TypeMC .................... 70–192 III. ConstructionSpecifications ................. 70–212 I. General ......................................... 70–192 354 NonmetallicUndergroundConduitwith II. Installation ..................................... 70–193 Conductors:TypeNUCC ........................ 70–212 III. ConstructionSpecifications ................. 70–194 I. General ......................................... 70–212 332 Mineral-Insulated,Metal-SheathedCable: II. Installation ..................................... 70–212 TypeMI ............................................. 70–194 III. ConstructionSpecifications ................. 70–213 I. General ......................................... 70–194 355 ReinforcedThermosettingResinConduit: II. Installation ..................................... 70–195 TypeRTRC ......................................... 70–213 III. ConstructionSpecifications ................. 70–196 I. General ......................................... 70–213 334 Nonmetallic-SheathedCable:TypesNM, II. Installation ..................................... 70–214 NMC,andNMS ................................... 70–196 III. ConstructionSpecifications ................. 70–216 I. General ......................................... 70–196 356 LiquidtightFlexibleNonmetallicConduit: II. Installation ..................................... 70–196 TypeLFNC ......................................... 70–216 III. ConstructionSpecifications ................. 70–198 I. General ......................................... 70–216 336 PowerandControlTrayCable:TypeTC .... 70–198 II. Installation ..................................... 70–216 III. ConstructionSpecifications ................. 70–217 I. General ......................................... 70–198 II. Installation ..................................... 70–199 358 ElectricalMetallicTubing:TypeEMT ........ 70–218 III. ConstructionSpecifications ................. 70–199 I. General ......................................... 70–218 338 Service-EntranceCable:TypesSEand II. Installation ..................................... 70–218 USE .................................................. 70–200 III. ConstructionSpecifications ................. 70–219 I. General ......................................... 70–200 360 FlexibleMetallicTubing:TypeFMT ......... 70–219 II. Installation ..................................... 70–200 I. General ......................................... 70–219 III. Construction ................................... 70–201 II. Installation ..................................... 70–219 III. ConstructionSpecifications ................. 70–220 340 UndergroundFeederandBranch-Circuit Cable:TypeUF .................................... 70–201 362 ElectricalNonmetallicTubing:TypeENT ... 70–220 I. General ......................................... 70–201 I. General ......................................... 70–220 II. Installation ..................................... 70–201 II. Installation ..................................... 70–220 III. ConstructionSpecifications ................. 70–202 III. ConstructionSpecifications ................. 70–222 342 IntermediateMetalConduit:TypeIMC ...... 70–202 366 AuxiliaryGutters ................................. 70–222 I. General ......................................... 70–202 I. General ......................................... 70–222 II. Installation ..................................... 70–202 II. Installation ..................................... 70–222 III. ConstructionSpecifications ................. 70–203 III. ConstructionSpecifications ................. 70–224 2011Edition NATIONALELECTRICALCODE 70–3 CONTENTS ARTICLE ARTICLE 368 Busways ............................................ 70–224 398 OpenWiringonInsulators ...................... 70–248 I. GeneralRequirements ........................ 70–224 I. General ......................................... 70–248 II. Installation ..................................... 70–224 II. Installation ..................................... 70–248 III. Construction ................................... 70–226 III. ConstructionSpecifications ................. 70–250 IV. RequirementsforOver600Volts, 399 OutdoorOverheadConductorsover600 Nominal ......................................... 70–226 Volts ................................................. 70–250 370 Cablebus ........................................... 70–227 372 CellularConcreteFloorRaceways ............ 70–228 Chapter 4Equipment for General Use 374 CellularMetalFloorRaceways ................ 70–229 400 FlexibleCordsandCables ...................... 70–251 I. Installation ..................................... 70–229 I. General ......................................... 70–251 II. ConstructionSpecifications ................. 70–229 II. ConstructionSpecifications ................. 70–260 III. PortableCablesOver600Volts, 376 MetalWireways ................................... 70–230 Nominal ......................................... 70–261 I. General ......................................... 70–230 402 FixtureWires ...................................... 70–262 II. Installation ..................................... 70–230 III. ConstructionSpecifications ................. 70–231 404 Switches ............................................ 70–266 378 NonmetallicWireways ........................... 70–231 I. Installation ..................................... 70–266 II. ConstructionSpecifications ................. 70–270 I. General ......................................... 70–231 II. Installation ..................................... 70–231 406 Receptacles,CordConnectors,and III. ConstructionSpecifications ................. 70–232 AttachmentPlugs(Caps) ......................... 70–270 380 MultioutletAssembly ............................ 70–232 408 SwitchboardsandPanelboards ................. 70–274 I. General ......................................... 70–232 I. General ......................................... 70–274 II. Installation ..................................... 70–232 II. Switchboards .................................. 70–275 III. Panelboards .................................... 70–276 382 NonmetallicExtensions .......................... 70–233 IV. ConstructionSpecifications ................. 70–277 I. General ......................................... 70–233 409 IndustrialControlPanels ........................ 70–278 II. Installation ..................................... 70–233 III. ConstructionSpecifications I. General ......................................... 70–278 (ConcealableNonmetallicExtensions II. Installation ..................................... 70–278 Only)............................................. 70–234 III. ConstructionSpecifications ................. 70–279 384 Strut-TypeChannelRaceway ................... 70–235 410 Luminaires,Lampholders,andLamps ........ 70–280 I. General ......................................... 70–235 I. General ......................................... 70–280 II. Installation ..................................... 70–235 II. LuminaireLocations ......................... 70–281 III. ConstructionSpecifications ................. 70–236 III. ProvisionsatLuminaireOutletBoxes, Canopies,andPans ............................ 70–282 386 SurfaceMetalRaceways ........................ 70–236 IV. LuminaireSupports ........................... 70–282 I. General ......................................... 70–236 V. Grounding ...................................... 70–283 II. Installation ..................................... 70–236 VI. WiringofLuminaires ........................ 70–283 III. ConstructionSpecifications ................. 70–237 VII. ConstructionofLuminaires ................. 70–285 VIII. InstallationofLampholders ................. 70–285 388 SurfaceNonmetallicRaceways ................ 70–237 IX. LampsandAuxiliaryEquipment ........... 70–285 I. General ......................................... 70–237 X. SpecialProvisionsforFlushand II. Installation ..................................... 70–237 RecessedLuminaires .......................... 70–286 III. ConstructionSpecifications ................. 70–238 XI. ConstructionofFlushandRecessed Luminaires ...................................... 70–286 390 UnderfloorRaceways ............................ 70–238 XII. SpecialProvisionsfor 392 CableTrays ........................................ 70–239 Electric-DischargeLightingSystemsof 1000VoltsorLess ............................ 70–286 I. General ......................................... 70–239 XIII. SpecialProvisionsfor II. Installation ..................................... 70–239 Electric-DischargeLightingSystemsof III. ConstructionSpecifications ................. 70–246 MoreThan1000Volts ........................ 70–288 394 ConcealedKnob-and-TubeWiring ............. 70–246 XIV. LightingTrack ................................. 70–289 I. General ......................................... 70–246 XV. DecorativeLightingandSimilar II. Installation ..................................... 70–246 Accessories ..................................... 70–289 III. ConstructionSpecifications ................. 70–247 411 LightingSystemsOperatingat30Voltsor Less .................................................. 70–289 396 Messenger-SupportedWiring ................... 70–247 422 Appliances ......................................... 70–290 I. General ......................................... 70–247 II. Installation ..................................... 70–248 I. General ......................................... 70–290 70–4 NATIONALELECTRICALCODE 2011Edition CONTENTS ARTICLE ARTICLE II. Installation ..................................... 70–290 V. ControllersforMotor-Compressors ........ 70–344 III. DisconnectingMeans ........................ 70–293 VI. Motor-CompressorandBranch-Circuit IV. Construction ................................... 70–294 OverloadProtection ........................... 70–345 V. Marking ........................................ 70–295 VII. ProvisionsforRoomAirConditioners .... 70–346 424 FixedElectricSpace-HeatingEquipment ..... 70–295 445 Generators ......................................... 70–347 I. General ......................................... 70–295 450 TransformersandTransformerVaults II. Installation ..................................... 70–296 (IncludingSecondaryTies) ...................... 70–348 III. ControlandProtectionofFixed I. GeneralProvisions ............................ 70–348 ElectricSpace-HeatingEquipment ......... 70–296 II. SpecificProvisionsApplicableto IV. MarkingofHeatingEquipment ............ 70–298 DifferentTypesofTransformers ............ 70–352 V. ElectricSpace-HeatingCables .............. 70–298 III. TransformerVaults ........................... 70–354 VI. DuctHeaters ................................... 70–300 VII. Resistance-TypeBoilers ..................... 70–300 455 PhaseConverters ................................. 70–355 VIII. Electrode-TypeBoilers ....................... 70–301 I. General ......................................... 70–355 IX. ElectricRadiantHeatingPanelsand II. SpecificProvisionsApplicableto HeatingPanelSets ............................ 70–302 DifferentTypesofPhaseConverters ....... 70–356 426 FixedOutdoorElectricDeicingand 460 Capacitors .......................................... 70–357 Snow-MeltingEquipment ........................ 70–304 I. 600Volts,Nominal,andUnder ............ 70–357 I. General ......................................... 70–304 II. Over600Volts,Nominal .................... 70–358 II. Installation ..................................... 70–305 III. ResistanceHeatingElements ............... 70–305 470 ResistorsandReactors ........................... 70–358 IV. ImpedanceHeating ........................... 70–306 I. 600Volts,Nominal,andUnder ............ 70–358 V. Skin-EffectHeating ........................... 70–306 II. Over600Volts,Nominal .................... 70–359 VI. ControlandProtection ....................... 70–307 480 StorageBatteries .................................. 70–359 427 FixedElectricHeatingEquipmentfor 490 Equipment,Over600Volts,Nominal ......... 70–360 PipelinesandVessels ............................. 70–307 I. General ......................................... 70–360 I. General ......................................... 70–307 II. Equipment—SpecificProvisions ......... 70–361 II. Installation ..................................... 70–308 III. Equipment—Metal-EnclosedPower III. ResistanceHeatingElements ............... 70–308 SwitchgearandIndustrialControl IV. ImpedanceHeating ........................... 70–309 Assemblies ...................................... 70–363 V. InductionHeating ............................. 70–309 IV. MobileandPortableEquipment ............ 70–365 VI. Skin-EffectHeating ........................... 70–309 V. Electrode-TypeBoilers ....................... 70–366 VII. ControlandProtection ....................... 70–309 430 Motors,MotorCircuits,andControllers ...... 70–310 Chapter 5Special Occupancies I. General ......................................... 70–310 500 Hazardous(Classified)Locations,Classes II. MotorCircuitConductors ................... 70–316 I,II,andIII,Divisions1and2 ................. 70–367 III. MotorandBranch-CircuitOverload Protection ....................................... 70–319 501 ClassILocations ................................. 70–376 IV. MotorBranch-CircuitShort-Circuit I. General ......................................... 70–376 andGround-FaultProtection ................. 70–322 II. Wiring .......................................... 70–376 V. MotorFeederShort-Circuitand III. Equipment ...................................... 70–381 Ground-FaultProtection ...................... 70–325 VI. MotorControlCircuits ....................... 70–326 502 ClassIILocations ................................ 70–386 VII. MotorControllers ............................. 70–327 I. General ......................................... 70–386 VIII. MotorControlCenters ....................... 70–329 II. Wiring .......................................... 70–386 IX. DisconnectingMeans ........................ 70–330 III. Equipment ...................................... 70–388 X. Adjustable-SpeedDriveSystems ........... 70–333 XI. Over600Volts,Nominal .................... 70–334 503 ClassIIILocations ............................... 70–391 XII. ProtectionofLiveParts—All I. General ......................................... 70–391 Voltages ......................................... 70–335 II. Wiring .......................................... 70–391 XIII. Grounding—AllVoltages .................. 70–335 III. Equipment ...................................... 70–392 XIV. Tables ........................................... 70–336 504 IntrinsicallySafeSystems ....................... 70–394 440 Air-ConditioningandRefrigerating Equipment .......................................... 70–340 505 Zone0,1,and2Locations ..................... 70–397 506 Zone20,21,and22Locationsfor I. General ......................................... 70–340 CombustibleDustsorIgnitible II. DisconnectingMeans ........................ 70–342 Fibers/Flyings ...................................... 70–412 III. Branch-CircuitShort-Circuitand Ground-FaultProtection ...................... 70–343 510 Hazardous(Classified)Locations— IV. Branch-CircuitConductors .................. 70–344 Specific .............................................. 70–419 2011Edition NATIONALELECTRICALCODE 70–5 CONTENTS ARTICLE ARTICLE 511 CommercialGarages,RepairandStorage .... 70–419 IV. AudioSignalProcessing, Amplification,andReproduction 513 AircraftHangars .................................. 70–422 Equipment ...................................... 70–477 514 MotorFuelDispensingFacilities .............. 70–425 545 ManufacturedBuildings ......................... 70–477 515 BulkStoragePlants .............................. 70–429 547 AgriculturalBuildings ........................... 70–478 516 SprayApplication,Dipping,andCoating 550 MobileHomes,ManufacturedHomes,and Processes ............................................ 70–434 MobileHomeParks ............................... 70–481 517 HealthCareFacilities ............................ 70–440 I. General ......................................... 70–481 II. MobileandManufacturedHomes ......... 70–482 I. General ......................................... 70–440 III. ServicesandFeeders ......................... 70–489 II. WiringandProtection ........................ 70–442 III. EssentialElectricalSystem .................. 70–445 551 RecreationalVehiclesandRecreational IV. InhalationAnesthetizingLocations ........ 70–452 VehicleParks ....................................... 70–490 V. X-RayInstallations ........................... 70–455 I. General ......................................... 70–490 VI. Communications,SignalingSystems, II. CombinationElectricalSystems ............ 70–491 DataSystems,FireAlarmSystems, III. OtherPowerSources ......................... 70–492 andSystemsLessThan120Volts, IV. Nominal120-Voltor120/240-Volt Nominal ......................................... 70–456 Systems.......................................... 70–493 VII. IsolatedPowerSystems ...................... 70–457 V. FactoryTests ................................... 70–500 VI. RecreationalVehicleParks .................. 70–500 518 AssemblyOccupancies .......................... 70–458 552 ParkTrailers ....................................... 70–503 520 Theaters,AudienceAreasofMotion PictureandTelevisionStudios, I. General ......................................... 70–503 PerformanceAreas,andSimilarLocations ... 70–459 II. Low-VoltageSystems ........................ 70–503 III. CombinationElectricalSystems ............ 70–504 I. General ......................................... 70–459 IV. Nominal120-Voltor120/240-Volt II. FixedStageSwitchboards ................... 70–461 Systems.......................................... 70–505 III. FixedStageEquipmentOtherThan V. FactoryTests ................................... 70–511 Switchboards ................................... 70–462 IV. PortableSwitchboardsonStage ............ 70–463 553 FloatingBuildings ................................ 70–512 V. PortableStageEquipmentOtherThan I. General ......................................... 70–512 Switchboards ................................... 70–466 II. ServicesandFeeders ......................... 70–512 VI. DressingRooms ............................... 70–468 III. Grounding ...................................... 70–512 VII. Grounding ...................................... 70–468 555 MarinasandBoatyards .......................... 70–513 522 ControlSystemsforPermanent 590 TemporaryInstallations .......................... 70–516 AmusementAttractions ........................... 70–468 I. General ......................................... 70–468 Chapter 6Special Equipment II. ControlCircuits ............................... 70–468 III. ControlCircuitWiringMethods ........... 70–469 600 ElectricSignsandOutlineLighting ........... 70–519 525 Carnivals,Circuses,Fairs,andSimilar I. General ......................................... 70–519 Events ............................................... 70–470 II. Field-InstalledSkeletonTubing, OutlineLighting,andSecondary I. GeneralRequirements ........................ 70–470 Wiring ........................................... 70–523 II. PowerSources ................................. 70–470 III. WiringMethods ............................... 70–471 604 ManufacturedWiringSystems ................. 70–525 IV. GroundingandBonding ..................... 70–472 605 OfficeFurnishings(ConsistingofLighting 530 MotionPictureandTelevisionStudios AccessoriesandWiredPartitions) .............. 70–526 andSimilarLocations ............................ 70–472 610 CranesandHoists ................................ 70–527 I. General ......................................... 70–472 I. General ......................................... 70–527 II. StageorSet .................................... 70–473 II. Wiring .......................................... 70–527 III. DressingRooms ............................... 70–475 III. ContactConductors ........................... 70–530 IV. Viewing,Cutting,andPatchingTables .... 70–475 IV. DisconnectingMeans ........................ 70–531 V. CelluloseNitrateFilmStorageVaults ..... 70–475 V. OvercurrentProtection ....................... 70–531 VI. Substations ..................................... 70–475 VI. Control .......................................... 70–532 VII. Grounding ...................................... 70–532 540 MotionPictureProjectionRooms ............. 70–476 620 Elevators,Dumbwaiters,Escalators, I. General ......................................... 70–476 MovingWalks,PlatformLifts,and II. EquipmentandProjectorsofthe StairwayChairlifts ................................ 70–532 ProfessionalType .............................. 70–476 III. NonprofessionalProjectors .................. 70–477 I. General ......................................... 70–532 70–6 NATIONALELECTRICALCODE 2011Edition CONTENTS ARTICLE ARTICLE II. Conductors ..................................... 70–534 680 SwimmingPools,Fountains,andSimilar III. Wiring .......................................... 70–536 Installations ......................................... 70–575 IV. InstallationofConductors ................... 70–538 I. General ......................................... 70–575 V. TravelingCables .............................. 70–539 II. PermanentlyInstalledPools ................. 70–579 VI. DisconnectingMeansandControl ......... 70–540 III. StorablePools ................................. 70–585 VII. OvercurrentProtection ....................... 70–542 IV. SpasandHotTubs ........................... 70–586 VIII. MachineRooms,ControlRooms, V. Fountains ....................................... 70–588 MachinerySpaces,andControlSpaces .... 70–542 VI. PoolsandTubsforTherapeuticUse ...... 70–589 IX. Grounding ...................................... 70–543 VII. HydromassageBathtubs ..................... 70–590 X. EmergencyandStandbyPower Systems.......................................... 70–543 682 NaturalandArtificiallyMadeBodiesof Water ................................................ 70–590 625 ElectricVehicleChargingSystem ............. 70–543 I. General ......................................... 70–590 I. General ......................................... 70–543 II. Installation ..................................... 70–591 II. WiringMethods ............................... 70–544 III. GroundingandBonding ..................... 70–592 III. EquipmentConstruction ..................... 70–544 IV. ControlandProtection ....................... 70–545 685 IntegratedElectricalSystems ................... 70–592 V. ElectricVehicleSupplyEquipment I. General ......................................... 70–592 Locations ........................................ 70–545 II. OrderlyShutdown ............................ 70–593 626 ElectrifiedTruckParkingSpaces .............. 70–547 690 SolarPhotovoltaic(PV)Systems .............. 70–593 I. General ......................................... 70–547 I. General ......................................... 70–593 II. ElectrifiedTruckParkingSpace II. CircuitRequirements ......................... 70–597 ElectricalWiringSystems .................... 70–548 III. DisconnectingMeans ........................ 70–599 III. ElectrifiedTruckParkingSpaceSupply IV. WiringMethods ............................... 70–601 Equipment ...................................... 70–549 V. Grounding ...................................... 70–603 IV. TransportRefrigeratedUnits(TRUs) ...... 70–551 VI. Marking ........................................ 70–604 630 ElectricWelders ................................... 70–552 VII. ConnectiontoOtherSources ............... 70–605 VIII. StorageBatteries .............................. 70–605 I. General ......................................... 70–552 IX. Systemsover600Volts ...................... 70–607 II. ArcWelders .................................... 70–552 III. ResistanceWelders ........................... 70–553 692 FuelCellSystems ................................ 70–607 IV. WeldingCable ................................. 70–554 I. General ......................................... 70–607 640 AudioSignalProcessing,Amplification, II. CircuitRequirements ......................... 70–608 andReproductionEquipment .................... 70–554 III. DisconnectingMeans ........................ 70–608 IV. WiringMethods ............................... 70–609 I. General ......................................... 70–554 V. Grounding ...................................... 70–609 II. PermanentAudioSystemInstallations .... 70–557 VI. Marking ........................................ 70–609 III. PortableandTemporaryAudioSystem VII. ConnectiontoOtherCircuits ............... 70–609 Installations ..................................... 70–558 VIII. OutputsOver600Volts ...................... 70–609 645 InformationTechnologyEquipment ........... 70–559 694 SmallWindElectricSystems ................... 70–610 647 SensitiveElectronicEquipment ................ 70–563 I. General ......................................... 70–610 650 PipeOrgans ........................................ 70–564 II. CircuitRequirements ......................... 70–611 660 X-RayEquipment ................................ 70–565 III. DisconnectingMeans ........................ 70–612 IV. WiringMethods ............................... 70–613 I. General ......................................... 70–565 V. Grounding ...................................... 70–613 II. Control .......................................... 70–566 VI. Marking ........................................ 70–614 III. TransformersandCapacitors ................ 70–566 VII. ConnectiontoOtherSources ............... 70–614 IV. GuardingandGrounding .................... 70–566 VIII. StorageBatteries .............................. 70–614 665 InductionandDielectricHeating IX. Systemsover600Volts ...................... 70–616 Equipment .......................................... 70–567 695 FirePumps ......................................... 70–616 I. General ......................................... 70–567 II. Guarding,Grounding,andLabeling ....... 70–568 Chapter 7Special Conditions 668 ElectrolyticCells ................................. 70–568 700 EmergencySystems .............................. 70–622 669 Electroplating ...................................... 70–571 I. General ......................................... 70–622 670 IndustrialMachinery ............................. 70–572 II. CircuitWiring ................................. 70–623 III. SourcesofPower ............................. 70–624 675 ElectricallyDrivenorControlled IV. EmergencySystemCircuitsfor IrrigationMachines ............................... 70–573 LightingandPower ........................... 70–626 I. General ......................................... 70–573 V. Control—EmergencyLighting II. CenterPivotIrrigationMachines .......... 70–575 Circuits .......................................... 70–626 2011Edition NATIONALELECTRICALCODE 70–7

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National electrical code handbook PDF

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NFPA 70 ® National Electrical Code® 2011 Edition NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471 An International Codes and Standards Organization Copyright © 2010 National Fire Protection Association® One Batterymarch Park Quincy, Massachusetts 02169-7471 NFPA, National Fire Protection Association, National Electrical Code, NFPA 70, and NEC are registered trademarks of the National Fire Protection Association. IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA® DOCUMENTS Notice and Disclaimer of Liability Concerning the Use of NFPA Documents NFPA® codes, standards, recommended practices, and guides (“NFPA Documents”), of which the document contained herein is one, are developed through a consensus standards development process approved by the American National Standards Institute. This process brings together volunteers representing varied viewpoints and interests to achieve consensus on fire and other safety issues. While the NFPA administers the process and establishes rules to promote fairness in the development of consensus, it does not independently test, evaluate, or verify the accuracy of any information or the soundness of any judgments contained in NFPA Documents. The NFPA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on NFPA Documents. The NFPA also makes no guaranty or warranty as to the accuracy or completeness of any information published herein. In issuing and making NFPA Documents available, the NFPA is not undertaking to render professional or other services for or on behalf of any person or entity. Nor is the NFPA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. The NFPA has no power, nor does it undertake, to police or enforce compliance with the contents of NFPA Documents. Nor does the NFPA list, certify, test, or inspect products, designs, or installations for compliance with this document. Any certification or other statement of compliance with the requirements of this document shall not be attributable to the NFPA and is solely the responsibility of the certifier or maker of the statement. ISBN: 978-087765914-3 (SB Print) ISBN: 978-087765915-0 (LL Print) ISBN: 978-087765913-6 (PDF) 14 13 12 11 10 10 9 8 7 6 5 4 3 2 1 IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA® DOCUMENTS ADDITIONAL NOTICES AND DISCLAIMERS Updating of NFPA Documents Users of NFPA codes, standards, recommended practices, and guides (“NFPA Documents”) should be aware that these documents may be superseded at any time by the issuance of new editions or may be amended from time to time through the issuance of Tentative Interim Amendments. An official NFPA Document at any point in time consists of the current edition of the document together with any Tentative Interim Amendments and any Errata then in effect. In order to determine whether a given document is the current edition and whether it has been amended through the issuance of Tentative Interim Amendments or corrected through the issuance of Errata, consult appropriate NFPA publications such as the National Fire Codes® Subscription Service, visit the NFPA website at www.nfpa.org, or contact the NFPA at the address listed below. Interpretations of NFPA Documents A statement, written or oral, that is not processed in accordance with Section 6 of the Regulations Governing Committee Projects shall not be considered the official position of NFPA or any of its Committees and shall not be considered to be, nor be relied upon as, a Formal Interpretation. Patents The NFPA does not take any position with respect to the validity of any patent rights referenced in, related to, or asserted in connection with an NFPA Document. The users of NFPA Documents bear the sole responsibility for determining the validity of any such patent rights, as well as the risk of infringement of such rights, and the NFPA disclaims liability for the infringement of any patent resulting from the use of or reliance on NFPA Documents. NFPA adheres to the policy of the American National Standards Institute (ANSI) regarding the inclusion of patents in American National Standards (“the ANSI Patent Policy”), and hereby gives the following notice pursuant to that policy: NOTICE: The user’s attention is called to the possibility that compliance with an NFPA Document may require use of an invention covered by patent rights. NFPA takes no position as to the validity of any such patent rights or as to whether such patent rights const itute or include essential patent claims under the ANSI Patent Policy. If, in connection with the ANSI Patent Policy, a patent holder has filed a statement of willingness to grant licenses under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license, copies of such filed statements can be obtained, on request, from NFPA. For further information, contact the NFPA at the address listed below. Law and Regulations Users of NFPA Documents should consult applicable federal, state, and local laws and regulations. NFPA does not, by the publication of its codes, standards, recommended practices, and guides, intend to urge action that is not in compliance with applicable laws, and these documents may not be construed as doing so. Copyrights NFPA Documents are copyrighted. They are made available for a wide variety of both public and private uses. These include both use, by reference, in laws and regulations, and use in private self-regulation, standardization, and the promotion of safe practices and methods. By making these documents available for use and adoption by public authorities and private users, the NFPA does not waive any rights in copyright to these documents. Use of NFPA Documents for regulatory purposes should be accomplished through adoption by reference. The term “adoption by reference” means the citing of title, edition, and publishing information only. Any deletions, additions, and changes desired by the adopting authority should be noted separately in the adopting instrument. In order to assist NFPA in following the uses made of its documents, adopting authorities are requested to notify the NFPA (Attention: Secretary, Standards Council) in writing of such use. For technical assistance and questions concerning adoption of NFPA Documents, contact NFPA at the address below. For Further Information All questions or other communications relating to NFPA Documents and all requests for information on NFPA procedures governing its codes and standards development process, including information on the procedures for requesting Formal Interpretations, for proposing Tentative Interim Amendments, and for proposing revisions to NFPA documents during regular revision cycles, should be sent to NFPA headquarters, addressed to the attention of the Secretary, Standards Council, NFPA, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101; email: [email protected] For more information about NFPA, visit the NFPA website at www.nfpa.org. Copyright©2010,NationalFireProtectionAssociation®.AllRightsReserved NFPA 70® National Electrical Code® 2011 Edition This edition of NFPA 70, National Electrical Code, was prepared by the National Electrical Code Committee and acted on by NFPAat its JuneAssociation Technical Meeting held June 7–10, 2010, in Las Vegas, NV. It was issued by the Standards Council on August 5, 2010, with an effective date of August 25, 2010, and supersedes all previous editions. This edition of NFPA70 was approved as anAmerican National Standard onAugust 25, 2010. History and Development of the National Electrical Code® TheNationalFireProtectionAssociationhasactedassponsoroftheNationalElectricalCodesince 1911. The original Code document was developed in 1897 as a result of the united efforts of various insurance, electrical, architectural, and allied interests. In accordance with the provisions of the NFPA Regulations Governing Committee Projects, a NationalElectricalCodeCommitteeReportonProposalscontainingproposedamendmentstothe2008 National Electrical Code was published by NFPAin July 2009.This report recorded the actions of the variousCode-MakingPanelsandtheCorrelatingCommitteeoftheNationalElectricalCodeCommittee oneachproposalthathadbeenmadetorevisethe2008Code.Thereportwascirculatedtoallmembers of the National Electrical Code Committee and was made available to other interested NFPAmembers and to the public for review and comment. Following the close of the public comment period, the Code-Making Panels met, acted on each comment, and reported their action to the Correlating Com- mittee. NFPApublished the National Electrical Code Committee Report on Comments in March 2010, which recorded the actions of the Code-Making Panels and the Correlating Committee on each public commenttotheNationalElectricalCodeCommitteeReportonProposals.TheNationalElectricalCode CommitteeReportonProposalsandtheNationalElectricalCodeCommitteeReportonCommentswere presented to the 2010 JuneAssociation Technical Meeting for adoption. NFPAhasanElectricalSectionthatprovidesparticularopportunityforNFPAmembersinterestedin electrical safety to become better informed and to contribute to the development of the National Electrical Code and other NFPA electrical standards. At the Electrical Section Codes and Standards Review Session held at the 2010 NFPA Conference and Expo, Section members had opportunity to discuss and review the report of the National Electrical Code Committee prior to the adoption of this edition of the Code by theAssociation at its 2010 June Technical Session. This 52nd edition supersedes all other previous editions, supplements, and printings dated 1897, 1899, 1901, 1903, 1904, 1905, 1907, 1909, 1911, 1913, 1915, 1918, 1920, 1923, 1925, 1926, 1928, 1930, 1931, 1933, 1935, 1937, 1940, 1942, 1943, 1947, 1949, 1951, 1953, 1954, 1955, 1956, 1957, 1958, 1959, 1962, 1965, 1968, 1971, 1975, 1978, 1981, 1984, 1987, 1990, 1993, 1996, 1999, 2002, 2005, and 2008. ThisCodeispurelyadvisoryasfarasNFPAisconcerned.Itismadeavailableforawidevarietyof bothpublicandprivateusesintheinterestoflifeandpropertyprotection.Theseincludebothuseinlaw and for regulatory purposes, and use in private self-regulation and standardization activities such as insurance underwriting, building and facilities construction and management, and product testing and certification. NFPA70,NationalElectricalCode,NFPA,andNationalFireProtectionAssociationareregisteredtrademarksoftheNationalFireProtectionAssociation,Quincy,Massachusetts,02169. CONTENTS Contents ARTICLE ARTICLE 90 Introduction ........................................ 70– 22 IV. DisconnectingandGuarding ................ 70– 96 V. PlugFuses,Fuseholders,andAdapters ... 70– 96 VI. CartridgeFusesandFuseholders ........... 70– 97 Chapter 1General VII. CircuitBreakers ............................... 70– 97 100 Definitions ......................................... 70– 26 VIII. SupervisedIndustrialInstallations ......... 70– 98 IX. OvercurrentProtectionOver600Volts, I. General ......................................... 70– 26 Nominal ......................................... 70–100 II. Over600Volts,Nominal .................... 70– 33 250 GroundingandBonding ......................... 70–100 110 RequirementsforElectricalInstallations ..... 70– 34 I. General ......................................... 70–100 I. General ......................................... 70– 34 II. SystemGrounding ........................... 70–103 II. 600Volts,Nominal,orLess ................ 70– 37 III. GroundingElectrodeSystemand III. Over600Volts,Nominal .................... 70– 40 GroundingElectrodeConductor ............. 70–111 IV. TunnelInstallationsover600Volts, IV. Enclosure,Raceway,andService Nominal ......................................... 70– 43 CableConnections ............................. 70–116 V. ManholesandOtherElectrical V. Bonding ......................................... 70–117 EnclosuresIntendedforPersonnel VI. EquipmentGroundingandEquipment Entry,AllVoltages ............................ 70– 44 GroundingConductors ........................ 70–120 VII. MethodsofEquipmentGrounding ......... 70–125 Chapter 2 Wiring and Protection VIII. Direct-CurrentSystems ...................... 70–128 IX. Instruments,Meters,andRelays ........... 70–129 200 UseandIdentificationofGrounded X. GroundingofSystemsandCircuitsof Conductors.......................................... 70– 46 over1kV ....................................... 70–129 210 BranchCircuits ................................... 70– 48 280 SurgeArresters,Over1kV ..................... 70–131 I. GeneralProvisions ............................ 70– 48 I. General ......................................... 70–131 II. Branch-CircuitRatings ....................... 70– 52 II. Installation ..................................... 70–132 III. RequiredOutlets .............................. 70– 55 III. ConnectingSurgeArresters ................. 70–132 215 Feeders ............................................. 70– 59 285 Surge-ProtectiveDevices(SPDs),1kVor 220 Branch-Circuit,Feeder,andService Less .................................................. 70–133 Calculations ........................................ 70– 61 I. General ......................................... 70–133 I. General ......................................... 70– 61 II. Installation ..................................... 70–133 II. Branch-CircuitLoadCalculations .......... 70– 61 III. ConnectingSPDs ............................. 70–133 III. FeederandServiceLoadCalculations .... 70– 64 IV. OptionalFeederandServiceLoad Chapter 3 Wiring Methods and Materials Calculations..................................... 70– 67 V. FarmLoadCalculations .................... 70– 70 300 WiringMethods ................................... 70–135 225 OutsideBranchCircuitsandFeeders ......... 70– 71 I. GeneralRequirements ........................ 70–135 II. Requirementsforover600Volts, I. General ......................................... 70– 71 Nominal ......................................... 70–145 II. BuildingsorOtherStructuresSupplied byaFeeder(s)orBranchCircuit(s) ........ 70– 74 310 ConductorsforGeneralWiring ................ 70–147 III. Over600Volts ................................ 70– 76 I. General ......................................... 70–147 230 Services ............................................ 70– 78 II. Installation ..................................... 70–147 III. ConstructionSpecifications ................. 70–168 I. General ......................................... 70– 78 312 Cabinets,CutoutBoxes,andMeterSocket II. OverheadServiceConductors .............. 70– 79 Enclosures .......................................... 70–173 III. UndergroundServiceConductors .......... 70– 81 IV. Service-EntranceConductors ............... 70– 81 I. Installation ..................................... 70–174 V. ServiceEquipment—General ............. 70– 84 II. ConstructionSpecifications ................. 70–175 VI. ServiceEquipment—Disconnecting 314 Outlet,Device,Pull,andJunctionBoxes; Means............................................ 70– 84 ConduitBodies;Fittings;andHandhole VII. ServiceEquipment—Overcurrent Enclosures .......................................... 70–177 Protection ....................................... 70– 86 VIII. ServicesExceeding600Volts, I. ScopeandGeneral ............................ 70–177 Nominal ......................................... 70– 87 II. Installation ..................................... 70–177 III. ConstructionSpecifications ................. 70–184 240 OvercurrentProtection ........................... 70– 88 IV. PullandJunctionBoxes,Conduit I. General ......................................... 70– 88 Bodies,andHandholeEnclosuresfor II. Location ........................................ 70– 92 UseonSystemsover600Volts, III. Enclosures ...................................... 70– 95 Nominal ......................................... 70–185 70–2 NATIONALELECTRICALCODE 2011Edition CONTENTS ARTICLE ARTICLE 320 ArmoredCable:TypeAC ....................... 70–186 344 RigidMetalConduit:TypeRMC .............. 70–203 I. General ......................................... 70–186 I. General ......................................... 70–203 II. Installation ..................................... 70–186 II. Installation ..................................... 70–203 III. ConstructionSpecifications ................. 70–187 III. ConstructionSpecifications ................. 70–205 322 FlatCableAssemblies:TypeFC ............... 70–187 348 FlexibleMetalConduit:TypeFMC ........... 70–205 I. General ......................................... 70–187 I. General ......................................... 70–205 II. Installation ..................................... 70–188 II. Installation ..................................... 70–205 III. Construction ................................... 70–188 350 LiquidtightFlexibleMetalConduit:Type 324 FlatConductorCable:TypeFCC .............. 70–189 LFMC ............................................... 70–207 I. General ......................................... 70–189 I. General ......................................... 70–207 II. Installation ..................................... 70–189 II. Installation ..................................... 70–207 III. Construction ................................... 70–190 III. ConstructionSpecifications ................. 70–208 326 IntegratedGasSpacerCable:TypeIGS ...... 70–191 352 RigidPolyvinylChlorideConduit:Type PVC ................................................. 70–208 I. General ......................................... 70–191 II. Installation ..................................... 70–191 I. General ......................................... 70–208 III. ConstructionSpecifications ................. 70–191 II. Installation ..................................... 70–208 III. ConstructionSpecifications ................. 70–210 328 MediumVoltageCable:TypeMV ............. 70–192 353 HighDensityPolyethyleneConduit:Type I. General ......................................... 70–192 HDPEConduit ..................................... 70–211 II. Installation ..................................... 70–192 III. ConstructionSpecifications ................. 70–192 I. General ......................................... 70–211 II. Installation ..................................... 70–211 330 Metal-CladCable:TypeMC .................... 70–192 III. ConstructionSpecifications ................. 70–212 I. General ......................................... 70–192 354 NonmetallicUndergroundConduitwith II. Installation ..................................... 70–193 Conductors:TypeNUCC ........................ 70–212 III. ConstructionSpecifications ................. 70–194 I. General ......................................... 70–212 332 Mineral-Insulated,Metal-SheathedCable: II. Installation ..................................... 70–212 TypeMI ............................................. 70–194 III. ConstructionSpecifications ................. 70–213 I. General ......................................... 70–194 355 ReinforcedThermosettingResinConduit: II. Installation ..................................... 70–195 TypeRTRC ......................................... 70–213 III. ConstructionSpecifications ................. 70–196 I. General ......................................... 70–213 334 Nonmetallic-SheathedCable:TypesNM, II. Installation ..................................... 70–214 NMC,andNMS ................................... 70–196 III. ConstructionSpecifications ................. 70–216 I. General ......................................... 70–196 356 LiquidtightFlexibleNonmetallicConduit: II. Installation ..................................... 70–196 TypeLFNC ......................................... 70–216 III. ConstructionSpecifications ................. 70–198 I. General ......................................... 70–216 336 PowerandControlTrayCable:TypeTC .... 70–198 II. Installation ..................................... 70–216 III. ConstructionSpecifications ................. 70–217 I. General ......................................... 70–198 II. Installation ..................................... 70–199 358 ElectricalMetallicTubing:TypeEMT ........ 70–218 III. ConstructionSpecifications ................. 70–199 I. General ......................................... 70–218 338 Service-EntranceCable:TypesSEand II. Installation ..................................... 70–218 USE .................................................. 70–200 III. ConstructionSpecifications ................. 70–219 I. General ......................................... 70–200 360 FlexibleMetallicTubing:TypeFMT ......... 70–219 II. Installation ..................................... 70–200 I. General ......................................... 70–219 III. Construction ................................... 70–201 II. Installation ..................................... 70–219 III. ConstructionSpecifications ................. 70–220 340 UndergroundFeederandBranch-Circuit Cable:TypeUF .................................... 70–201 362 ElectricalNonmetallicTubing:TypeENT ... 70–220 I. General ......................................... 70–201 I. General ......................................... 70–220 II. Installation ..................................... 70–201 II. Installation ..................................... 70–220 III. ConstructionSpecifications ................. 70–202 III. ConstructionSpecifications ................. 70–222 342 IntermediateMetalConduit:TypeIMC ...... 70–202 366 AuxiliaryGutters ................................. 70–222 I. General ......................................... 70–202 I. General ......................................... 70–222 II. Installation ..................................... 70–202 II. Installation ..................................... 70–222 III. ConstructionSpecifications ................. 70–203 III. ConstructionSpecifications ................. 70–224 2011Edition NATIONALELECTRICALCODE 70–3 CONTENTS ARTICLE ARTICLE 368 Busways ............................................ 70–224 398 OpenWiringonInsulators ...................... 70–248 I. GeneralRequirements ........................ 70–224 I. General ......................................... 70–248 II. Installation ..................................... 70–224 II. Installation ..................................... 70–248 III. Construction ................................... 70–226 III. ConstructionSpecifications ................. 70–250 IV. RequirementsforOver600Volts, 399 OutdoorOverheadConductorsover600 Nominal ......................................... 70–226 Volts ................................................. 70–250 370 Cablebus ........................................... 70–227 372 CellularConcreteFloorRaceways ............ 70–228 Chapter 4Equipment for General Use 374 CellularMetalFloorRaceways ................ 70–229 400 FlexibleCordsandCables ...................... 70–251 I. Installation ..................................... 70–229 I. General ......................................... 70–251 II. ConstructionSpecifications ................. 70–229 II. ConstructionSpecifications ................. 70–260 III. PortableCablesOver600Volts, 376 MetalWireways ................................... 70–230 Nominal ......................................... 70–261 I. General ......................................... 70–230 402 FixtureWires ...................................... 70–262 II. Installation ..................................... 70–230 III. ConstructionSpecifications ................. 70–231 404 Switches ............................................ 70–266 378 NonmetallicWireways ........................... 70–231 I. Installation ..................................... 70–266 II. ConstructionSpecifications ................. 70–270 I. General ......................................... 70–231 II. Installation ..................................... 70–231 406 Receptacles,CordConnectors,and III. ConstructionSpecifications ................. 70–232 AttachmentPlugs(Caps) ......................... 70–270 380 MultioutletAssembly ............................ 70–232 408 SwitchboardsandPanelboards ................. 70–274 I. General ......................................... 70–232 I. General ......................................... 70–274 II. Installation ..................................... 70–232 II. Switchboards .................................. 70–275 III. Panelboards .................................... 70–276 382 NonmetallicExtensions .......................... 70–233 IV. ConstructionSpecifications ................. 70–277 I. General ......................................... 70–233 409 IndustrialControlPanels ........................ 70–278 II. Installation ..................................... 70–233 III. ConstructionSpecifications I. General ......................................... 70–278 (ConcealableNonmetallicExtensions II. Installation ..................................... 70–278 Only)............................................. 70–234 III. ConstructionSpecifications ................. 70–279 384 Strut-TypeChannelRaceway ................... 70–235 410 Luminaires,Lampholders,andLamps ........ 70–280 I. General ......................................... 70–235 I. General ......................................... 70–280 II. Installation ..................................... 70–235 II. LuminaireLocations ......................... 70–281 III. ConstructionSpecifications ................. 70–236 III. ProvisionsatLuminaireOutletBoxes, Canopies,andPans ............................ 70–282 386 SurfaceMetalRaceways ........................ 70–236 IV. LuminaireSupports ........................... 70–282 I. General ......................................... 70–236 V. Grounding ...................................... 70–283 II. Installation ..................................... 70–236 VI. WiringofLuminaires ........................ 70–283 III. ConstructionSpecifications ................. 70–237 VII. ConstructionofLuminaires ................. 70–285 VIII. InstallationofLampholders ................. 70–285 388 SurfaceNonmetallicRaceways ................ 70–237 IX. LampsandAuxiliaryEquipment ........... 70–285 I. General ......................................... 70–237 X. SpecialProvisionsforFlushand II. Installation ..................................... 70–237 RecessedLuminaires .......................... 70–286 III. ConstructionSpecifications ................. 70–238 XI. ConstructionofFlushandRecessed Luminaires ...................................... 70–286 390 UnderfloorRaceways ............................ 70–238 XII. SpecialProvisionsfor 392 CableTrays ........................................ 70–239 Electric-DischargeLightingSystemsof 1000VoltsorLess ............................ 70–286 I. General ......................................... 70–239 XIII. SpecialProvisionsfor II. Installation ..................................... 70–239 Electric-DischargeLightingSystemsof III. ConstructionSpecifications ................. 70–246 MoreThan1000Volts ........................ 70–288 394 ConcealedKnob-and-TubeWiring ............. 70–246 XIV. LightingTrack ................................. 70–289 I. General ......................................... 70–246 XV. DecorativeLightingandSimilar II. Installation ..................................... 70–246 Accessories ..................................... 70–289 III. ConstructionSpecifications ................. 70–247 411 LightingSystemsOperatingat30Voltsor Less .................................................. 70–289 396 Messenger-SupportedWiring ................... 70–247 422 Appliances ......................................... 70–290 I. General ......................................... 70–247 II. Installation ..................................... 70–248 I. General ......................................... 70–290 70–4 NATIONALELECTRICALCODE 2011Edition CONTENTS ARTICLE ARTICLE II. Installation ..................................... 70–290 V. ControllersforMotor-Compressors ........ 70–344 III. DisconnectingMeans ........................ 70–293 VI. Motor-CompressorandBranch-Circuit IV. Construction ................................... 70–294 OverloadProtection ........................... 70–345 V. Marking ........................................ 70–295 VII. ProvisionsforRoomAirConditioners .... 70–346 424 FixedElectricSpace-HeatingEquipment ..... 70–295 445 Generators ......................................... 70–347 I. General ......................................... 70–295 450 TransformersandTransformerVaults II. Installation ..................................... 70–296 (IncludingSecondaryTies) ...................... 70–348 III. ControlandProtectionofFixed I. GeneralProvisions ............................ 70–348 ElectricSpace-HeatingEquipment ......... 70–296 II. SpecificProvisionsApplicableto IV. MarkingofHeatingEquipment ............ 70–298 DifferentTypesofTransformers ............ 70–352 V. ElectricSpace-HeatingCables .............. 70–298 III. TransformerVaults ........................... 70–354 VI. DuctHeaters ................................... 70–300 VII. Resistance-TypeBoilers ..................... 70–300 455 PhaseConverters ................................. 70–355 VIII. Electrode-TypeBoilers ....................... 70–301 I. General ......................................... 70–355 IX. ElectricRadiantHeatingPanelsand II. SpecificProvisionsApplicableto HeatingPanelSets ............................ 70–302 DifferentTypesofPhaseConverters ....... 70–356 426 FixedOutdoorElectricDeicingand 460 Capacitors .......................................... 70–357 Snow-MeltingEquipment ........................ 70–304 I. 600Volts,Nominal,andUnder ............ 70–357 I. General ......................................... 70–304 II. Over600Volts,Nominal .................... 70–358 II. Installation ..................................... 70–305 III. ResistanceHeatingElements ............... 70–305 470 ResistorsandReactors ........................... 70–358 IV. ImpedanceHeating ........................... 70–306 I. 600Volts,Nominal,andUnder ............ 70–358 V. Skin-EffectHeating ........................... 70–306 II. Over600Volts,Nominal .................... 70–359 VI. ControlandProtection ....................... 70–307 480 StorageBatteries .................................. 70–359 427 FixedElectricHeatingEquipmentfor 490 Equipment,Over600Volts,Nominal ......... 70–360 PipelinesandVessels ............................. 70–307 I. General ......................................... 70–360 I. General ......................................... 70–307 II. Equipment—SpecificProvisions ......... 70–361 II. Installation ..................................... 70–308 III. Equipment—Metal-EnclosedPower III. ResistanceHeatingElements ............... 70–308 SwitchgearandIndustrialControl IV. ImpedanceHeating ........................... 70–309 Assemblies ...................................... 70–363 V. InductionHeating ............................. 70–309 IV. MobileandPortableEquipment ............ 70–365 VI. Skin-EffectHeating ........................... 70–309 V. Electrode-TypeBoilers ....................... 70–366 VII. ControlandProtection ....................... 70–309 430 Motors,MotorCircuits,andControllers ...... 70–310 Chapter 5Special Occupancies I. General ......................................... 70–310 500 Hazardous(Classified)Locations,Classes II. MotorCircuitConductors ................... 70–316 I,II,andIII,Divisions1and2 ................. 70–367 III. MotorandBranch-CircuitOverload Protection ....................................... 70–319 501 ClassILocations ................................. 70–376 IV. MotorBranch-CircuitShort-Circuit I. General ......................................... 70–376 andGround-FaultProtection ................. 70–322 II. Wiring .......................................... 70–376 V. MotorFeederShort-Circuitand III. Equipment ...................................... 70–381 Ground-FaultProtection ...................... 70–325 VI. MotorControlCircuits ....................... 70–326 502 ClassIILocations ................................ 70–386 VII. MotorControllers ............................. 70–327 I. General ......................................... 70–386 VIII. MotorControlCenters ....................... 70–329 II. Wiring .......................................... 70–386 IX. DisconnectingMeans ........................ 70–330 III. Equipment ...................................... 70–388 X. Adjustable-SpeedDriveSystems ........... 70–333 XI. Over600Volts,Nominal .................... 70–334 503 ClassIIILocations ............................... 70–391 XII. ProtectionofLiveParts—All I. General ......................................... 70–391 Voltages ......................................... 70–335 II. Wiring .......................................... 70–391 XIII. Grounding—AllVoltages .................. 70–335 III. Equipment ...................................... 70–392 XIV. Tables ........................................... 70–336 504 IntrinsicallySafeSystems ....................... 70–394 440 Air-ConditioningandRefrigerating Equipment .......................................... 70–340 505 Zone0,1,and2Locations ..................... 70–397 506 Zone20,21,and22Locationsfor I. General ......................................... 70–340 CombustibleDustsorIgnitible II. DisconnectingMeans ........................ 70–342 Fibers/Flyings ...................................... 70–412 III. Branch-CircuitShort-Circuitand Ground-FaultProtection ...................... 70–343 510 Hazardous(Classified)Locations— IV. Branch-CircuitConductors .................. 70–344 Specific .............................................. 70–419 2011Edition NATIONALELECTRICALCODE 70–5 CONTENTS ARTICLE ARTICLE 511 CommercialGarages,RepairandStorage .... 70–419 IV. AudioSignalProcessing, Amplification,andReproduction 513 AircraftHangars .................................. 70–422 Equipment ...................................... 70–477 514 MotorFuelDispensingFacilities .............. 70–425 545 ManufacturedBuildings ......................... 70–477 515 BulkStoragePlants .............................. 70–429 547 AgriculturalBuildings ........................... 70–478 516 SprayApplication,Dipping,andCoating 550 MobileHomes,ManufacturedHomes,and Processes ............................................ 70–434 MobileHomeParks ............................... 70–481 517 HealthCareFacilities ............................ 70–440 I. General ......................................... 70–481 II. MobileandManufacturedHomes ......... 70–482 I. General ......................................... 70–440 III. ServicesandFeeders ......................... 70–489 II. WiringandProtection ........................ 70–442 III. EssentialElectricalSystem .................. 70–445 551 RecreationalVehiclesandRecreational IV. InhalationAnesthetizingLocations ........ 70–452 VehicleParks ....................................... 70–490 V. X-RayInstallations ........................... 70–455 I. General ......................................... 70–490 VI. Communications,SignalingSystems, II. CombinationElectricalSystems ............ 70–491 DataSystems,FireAlarmSystems, III. OtherPowerSources ......................... 70–492 andSystemsLessThan120Volts, IV. Nominal120-Voltor120/240-Volt Nominal ......................................... 70–456 Systems.......................................... 70–493 VII. IsolatedPowerSystems ...................... 70–457 V. FactoryTests ................................... 70–500 VI. RecreationalVehicleParks .................. 70–500 518 AssemblyOccupancies .......................... 70–458 552 ParkTrailers ....................................... 70–503 520 Theaters,AudienceAreasofMotion PictureandTelevisionStudios, I. General ......................................... 70–503 PerformanceAreas,andSimilarLocations ... 70–459 II. Low-VoltageSystems ........................ 70–503 III. CombinationElectricalSystems ............ 70–504 I. General ......................................... 70–459 IV. Nominal120-Voltor120/240-Volt II. FixedStageSwitchboards ................... 70–461 Systems.......................................... 70–505 III. FixedStageEquipmentOtherThan V. FactoryTests ................................... 70–511 Switchboards ................................... 70–462 IV. PortableSwitchboardsonStage ............ 70–463 553 FloatingBuildings ................................ 70–512 V. PortableStageEquipmentOtherThan I. General ......................................... 70–512 Switchboards ................................... 70–466 II. ServicesandFeeders ......................... 70–512 VI. DressingRooms ............................... 70–468 III. Grounding ...................................... 70–512 VII. Grounding ...................................... 70–468 555 MarinasandBoatyards .......................... 70–513 522 ControlSystemsforPermanent 590 TemporaryInstallations .......................... 70–516 AmusementAttractions ........................... 70–468 I. General ......................................... 70–468 Chapter 6Special Equipment II. ControlCircuits ............................... 70–468 III. ControlCircuitWiringMethods ........... 70–469 600 ElectricSignsandOutlineLighting ........... 70–519 525 Carnivals,Circuses,Fairs,andSimilar I. General ......................................... 70–519 Events ............................................... 70–470 II. Field-InstalledSkeletonTubing, OutlineLighting,andSecondary I. GeneralRequirements ........................ 70–470 Wiring ........................................... 70–523 II. PowerSources ................................. 70–470 III. WiringMethods ............................... 70–471 604 ManufacturedWiringSystems ................. 70–525 IV. GroundingandBonding ..................... 70–472 605 OfficeFurnishings(ConsistingofLighting 530 MotionPictureandTelevisionStudios AccessoriesandWiredPartitions) .............. 70–526 andSimilarLocations ............................ 70–472 610 CranesandHoists ................................ 70–527 I. General ......................................... 70–472 I. General ......................................... 70–527 II. StageorSet .................................... 70–473 II. Wiring .......................................... 70–527 III. DressingRooms ............................... 70–475 III. ContactConductors ........................... 70–530 IV. Viewing,Cutting,andPatchingTables .... 70–475 IV. DisconnectingMeans ........................ 70–531 V. CelluloseNitrateFilmStorageVaults ..... 70–475 V. OvercurrentProtection ....................... 70–531 VI. Substations ..................................... 70–475 VI. Control .......................................... 70–532 VII. Grounding ...................................... 70–532 540 MotionPictureProjectionRooms ............. 70–476 620 Elevators,Dumbwaiters,Escalators, I. General ......................................... 70–476 MovingWalks,PlatformLifts,and II. EquipmentandProjectorsofthe StairwayChairlifts ................................ 70–532 ProfessionalType .............................. 70–476 III. NonprofessionalProjectors .................. 70–477 I. General ......................................... 70–532 70–6 NATIONALELECTRICALCODE 2011Edition CONTENTS ARTICLE ARTICLE II. Conductors ..................................... 70–534 680 SwimmingPools,Fountains,andSimilar III. Wiring .......................................... 70–536 Installations ......................................... 70–575 IV. InstallationofConductors ................... 70–538 I. General ......................................... 70–575 V. TravelingCables .............................. 70–539 II. PermanentlyInstalledPools ................. 70–579 VI. DisconnectingMeansandControl ......... 70–540 III. StorablePools ................................. 70–585 VII. OvercurrentProtection ....................... 70–542 IV. SpasandHotTubs ........................... 70–586 VIII. MachineRooms,ControlRooms, V. Fountains ....................................... 70–588 MachinerySpaces,andControlSpaces .... 70–542 VI. PoolsandTubsforTherapeuticUse ...... 70–589 IX. Grounding ...................................... 70–543 VII. HydromassageBathtubs ..................... 70–590 X. EmergencyandStandbyPower Systems.......................................... 70–543 682 NaturalandArtificiallyMadeBodiesof Water ................................................ 70–590 625 ElectricVehicleChargingSystem ............. 70–543 I. General ......................................... 70–590 I. General ......................................... 70–543 II. Installation ..................................... 70–591 II. WiringMethods ............................... 70–544 III. GroundingandBonding ..................... 70–592 III. EquipmentConstruction ..................... 70–544 IV. ControlandProtection ....................... 70–545 685 IntegratedElectricalSystems ................... 70–592 V. ElectricVehicleSupplyEquipment I. General ......................................... 70–592 Locations ........................................ 70–545 II. OrderlyShutdown ............................ 70–593 626 ElectrifiedTruckParkingSpaces .............. 70–547 690 SolarPhotovoltaic(PV)Systems .............. 70–593 I. General ......................................... 70–547 I. General ......................................... 70–593 II. ElectrifiedTruckParkingSpace II. CircuitRequirements ......................... 70–597 ElectricalWiringSystems .................... 70–548 III. DisconnectingMeans ........................ 70–599 III. ElectrifiedTruckParkingSpaceSupply IV. WiringMethods ............................... 70–601 Equipment ...................................... 70–549 V. Grounding ...................................... 70–603 IV. TransportRefrigeratedUnits(TRUs) ...... 70–551 VI. Marking ........................................ 70–604 630 ElectricWelders ................................... 70–552 VII. ConnectiontoOtherSources ............... 70–605 VIII. StorageBatteries .............................. 70–605 I. General ......................................... 70–552 IX. Systemsover600Volts ...................... 70–607 II. ArcWelders .................................... 70–552 III. ResistanceWelders ........................... 70–553 692 FuelCellSystems ................................ 70–607 IV. WeldingCable ................................. 70–554 I. General ......................................... 70–607 640 AudioSignalProcessing,Amplification, II. CircuitRequirements ......................... 70–608 andReproductionEquipment .................... 70–554 III. DisconnectingMeans ........................ 70–608 IV. WiringMethods ............................... 70–609 I. General ......................................... 70–554 V. Grounding ...................................... 70–609 II. PermanentAudioSystemInstallations .... 70–557 VI. Marking ........................................ 70–609 III. PortableandTemporaryAudioSystem VII. ConnectiontoOtherCircuits ............... 70–609 Installations ..................................... 70–558 VIII. OutputsOver600Volts ...................... 70–609 645 InformationTechnologyEquipment ........... 70–559 694 SmallWindElectricSystems ................... 70–610 647 SensitiveElectronicEquipment ................ 70–563 I. General ......................................... 70–610 650 PipeOrgans ........................................ 70–564 II. CircuitRequirements ......................... 70–611 660 X-RayEquipment ................................ 70–565 III. DisconnectingMeans ........................ 70–612 IV. WiringMethods ............................... 70–613 I. General ......................................... 70–565 V. Grounding ...................................... 70–613 II. Control .......................................... 70–566 VI. Marking ........................................ 70–614 III. TransformersandCapacitors ................ 70–566 VII. ConnectiontoOtherSources ............... 70–614 IV. GuardingandGrounding .................... 70–566 VIII. StorageBatteries .............................. 70–614 665 InductionandDielectricHeating IX. Systemsover600Volts ...................... 70–616 Equipment .......................................... 70–567 695 FirePumps ......................................... 70–616 I. General ......................................... 70–567 II. Guarding,Grounding,andLabeling ....... 70–568 Chapter 7Special Conditions 668 ElectrolyticCells ................................. 70–568 700 EmergencySystems .............................. 70–622 669 Electroplating ...................................... 70–571 I. General ......................................... 70–622 670 IndustrialMachinery ............................. 70–572 II. CircuitWiring ................................. 70–623 III. SourcesofPower ............................. 70–624 675 ElectricallyDrivenorControlled IV. EmergencySystemCircuitsfor IrrigationMachines ............................... 70–573 LightingandPower ........................... 70–626 I. General ......................................... 70–573 V. Control—EmergencyLighting II. CenterPivotIrrigationMachines .......... 70–575 Circuits .......................................... 70–626 2011Edition NATIONALELECTRICALCODE 70–7

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