2020 NEC Code Reference

Grounding connects the system or equipment to earth; bonding establishes electrical continuity and an effective ground-fault current path. Exception/watch: Services,...

Other metal piping systems likely to become energized shall be bonded as required by 250.104(B). Exception/watch: CSST systems can have manufacturer instructions and...

If a metal underground water pipe qualifies as a grounding electrode, it shall be included in the grounding electrode system. Exception/watch: Electrode qualification depends...

All grounding electrodes described in 250.52(A)(1) through (A)(7) that are present at a building or structure shall be bonded together to form the grounding electrode system....

The grounded service conductor shall be connected to the grounding electrode system as required by 250.24. Exception/watch: Existing installations and separately derived...

Separately derived alternating-current systems shall be grounded and bonded in accordance with 250.30 where required. Exception/watch: Some systems are not separately derived...

Conductors shall have ampacity sufficient for the load after required adjustment and correction factors are applied. Exception/watch: Specific equipment articles,...

A continuous load is a load where the maximum current is expected to continue for 3 hours or more. Exception/watch: Listed assemblies rated for 100% operation can have...

AFCI protection shall be provided for the branch circuits and locations identified by the adopted edition of 210.12. Exception/watch: Check the adopted edition and local...

Equipment grounding conductors shall be sized in accordance with 250.122 and the rating or setting of the circuit overcurrent device, subject to the article rules....

Motor full-load current used for conductor and branch-circuit short-circuit/ground-fault protection calculations is generally determined from the Article 430 tables as...

Transformer secondary conductors shall be protected in accordance with one of the permitted 240.21(C) rule paths. Exception/watch: Outdoor secondary conductors and supervised...

Every circuit and circuit modification shall be legibly identified as to its clear, evident, and specific purpose or use. Exception/watch: Existing directories should be...

Indoor switchboards, switchgear, panelboards, and motor control centers shall have dedicated equipment space as required by 110.26(E). Exception/watch: Suspended ceilings...

Voltage drop recommendations appear in informational notes and are design considerations rather than blanket mandatory ampacity requirements. Exception/watch: Sensitive loads...

A grounding electrode conductor shall be installed in one continuous length without a splice or joint except as permitted by 250.64(C). Exception/watch: The rule contains...

Boxes shall be of sufficient size to provide free space for all enclosed conductors. Exception/watch: Check listed box volume markings and applicable raceway-body rules.

Raceway fill is determined from the actual conductor areas and the permitted percentage of the raceway internal area. Exception/watch: Nipples not over 24 in. have a 60% fill...

GFCI protection shall be provided in the locations and for the outlets/equipment covered by the adopted edition of 210.8. Exception/watch: Specific listed exceptions and...

Disconnecting means shall be provided for the controller and motor as required by 430.102. Exception/watch: Lockable disconnect provisions can affect the within-sight...

Transformer overcurrent protection shall be provided in accordance with 450.3 and the applicable table. Exception/watch: Supervised locations and transformers over or under...

Conductor ampacity shall be based on the temperature rating of the termination as required by 110.14(C). Exception/watch: Listed equipment identified for other conductor...

Working space about electrical equipment shall be provided and maintained to permit ready and safe operation and maintenance. Exception/watch: Special installations and...

Electrical equipment identified by 110.16 shall be field or factory marked to warn qualified persons of potential electric arc-flash hazards. Exception/watch: The NEC...

Purpose, scope, arrangement, enforcement concepts, and how to read the NEC in the field.

Keywords: scope, purpose, enforcement, mandatory, permissive, explanatory

Related:

Primary definitions used across the Code. Start here when a term drives the answer.

Keywords: definitions, qualified person, readily accessible, continuous load, grounded, bonding

Related: 110

General installation requirements, listing/labeling, working space, conductor terminations, equipment markings, and workmanship.

Keywords: working space, listing, labeling, torque, termination, 110.26, equipment space

Related: 100, 250

Grounded conductor identification, white/gray rules, and neutral conductor field identification issues.

Keywords: neutral, grounded conductor, white wire, gray wire, identification

Related: 210, 215, 250

Core branch-circuit rules for outlets, receptacles, required circuits, GFCI/AFCI references, and dwelling/commercial branch work.

Keywords: branch circuit, receptacle, GFCI, AFCI, small appliance, laundry, bathroom, garage, 210.8, 210.12, 210.52

Related: 220, 250, 406

Feeder sizing, ratings, voltage drop informational notes, and feeder identification in service/subpanel work.

Keywords: feeder, subpanel, ampacity, voltage drop, neutral

Related: 220, 225, 230, 250

Load calculations for dwellings, commercial spaces, feeders, and services.

Keywords: load calculation, service calculation, dwelling, demand factor, commercial load

Related: 210, 215, 230

Outside feeders/branch circuits, building disconnect rules, and detached structure feeds.

Keywords: detached garage, outside feeder, building disconnect, overhead, underground

Related: 215, 230, 250

Service conductors, service disconnecting means, service equipment, service entrance rules, and common utility/service work references.

Keywords: service, service disconnect, service equipment, meter, service entrance, 230.71

Related: 225, 250, 408

Breaker/fuse protection rules, standard ratings, tap conductors, conductor protection, and equipment protection.

Keywords: breaker, fuse, OCP, overcurrent, tap conductor, 240.4, 240.6

Related: 310, 408, 430

Surge protective devices and overvoltage protection requirements.

Keywords: surge, SPD, overvoltage

Related: 230, 250, 285

Grounding electrode systems, bonding, equipment grounding conductors, grounded conductors, and service/subpanel grounding logic.

Keywords: grounding, bonding, GEC, EGC, ground rod, water pipe, gas bonding, subpanel, 250.66, 250.122

Related: 100, 110, 200, 230, 680

SPD installation, connection, and application references.

Keywords: surge protective device, SPD, transient voltage

Related: 242, 230, 250

General wiring method rules: protection, securing/support, boxes, raceways, wet locations, and underground basics.

Keywords: wiring method, raceway, cable, support, secure, wet location, underground

Related: 310, 314, 358, 352

Conductor ampacity, insulation types, temperature ratings, and adjustment/correction references.

Keywords: ampacity, conductor, THHN, THWN, temperature, 310.16, derating

Related: 240, 300, 334

Cabinets and enclosures including wire bending and conductor space concerns.

Keywords: cabinet, enclosure, meter socket, wire bending

Related: 314, 408

Box fill, pull boxes, junction boxes, device boxes, conduit bodies, and handholes.

Keywords: box fill, junction box, pull box, device box, conduit body, 314.16

Related: 300, 370, Chapter 9

AC cable rules and limitations.

Keywords: AC cable, armored cable

Related: 300, 330

MC cable installation rules, uses, support, and limitations.

Keywords: MC cable, metal clad, support

Related: 300, 320, 334

NM-B rules for residential and light commercial contexts, protection, securing, and permitted uses.

Keywords: NM-B, Romex, nonmetallic sheathed cable, dwelling, support

Related: 300, 310, 320

SE/USE cable applications for service and feeder work.

Keywords: SE cable, USE cable, service entrance

Related: 230, 310, 334

IMC raceway uses, installation, support, and fittings.

Keywords: IMC, intermediate metal conduit

Related: 344, 358

Rigid metal conduit installation rules.

Keywords: RMC, rigid conduit, galvanized rigid

Related: 342, 358

FMC rules for flexibility, support, and permitted uses.

Keywords: flex, FMC, greenfield

Related: 350, 356

Liquidtight flex rules for wet/damp locations and equipment connections.

Keywords: liquidtight, LFMC, sealtite, wet location

Related: 348, 356

PVC conduit installation, expansion, underground, sunlight, and support references.

Keywords: PVC, schedule 40, schedule 80, underground, expansion fitting

Related: 300, 355, 358

LFNC rules for wet/damp locations and equipment whip-style use.

Keywords: LFNC, nonmetallic liquidtight, whip

Related: 350, 352

EMT installation, support, fittings, bends, corrosion protection, and common commercial raceway work.

Keywords: EMT, thinwall, conduit, support, strap, coupling, connector

Related: 300, 344, 352

ENT installation and permitted/limited uses.

Keywords: ENT, smurf tube

Related: 352, 358

Wireway fill, conductor count, splices, and industrial/commercial use.

Keywords: wireway, gutter, auxiliary gutter, fill

Related: 366, 378

Cable tray installation, support, and permitted cable types.

Keywords: cable tray, tray cable, industrial

Related: 300, 336

Flexible cord rules, uses not permitted, strain relief, and temporary equipment connection issues.

Keywords: cord, flexible cord, SO cord, extension cord

Related: 590, 422

Switch installation, switching of grounded conductors, snap switches, and enclosure requirements.

Keywords: switch, snap switch, disconnect switch

Related: 406, 430

Receptacle ratings, replacement rules, tamper resistance, weather resistance, grounding-type devices, and device applications.

Keywords: receptacle, outlet, NEMA, tamper resistant, weather resistant, WR, TR

Related: 210, 250, 422

Panelboards, switchboards, switchgear, circuit directories, unused openings, and panel equipment rules.

Keywords: panelboard, switchgear, switchboard, directory, breaker, unused opening

Related: 110, 230, 240

Lighting fixture installation, supports, clearance, LED/retrofit considerations, and luminaire rules.

Keywords: lighting, luminaire, fixture, lampholder, LED

Related: 411, 410

Low-voltage lighting systems, power supplies, and installation rules.

Keywords: low voltage lighting, landscape lighting, driver

Related: 410, 725

Appliance branch circuits, disconnecting means, nameplate ratings, and appliance installation references.

Keywords: appliance, dishwasher, water heater, disconnect

Related: 210, 422, 440

Baseboard, space heat, and fixed heating equipment circuits/controls.

Keywords: baseboard heat, space heater, electric heat

Related: 210, 422

Motor conductor sizing, overloads, short-circuit protection, disconnects, and controller rules.

Keywords: motor, overload, MCC, starter, disconnect, VFD

Related: 240, 440, 460

A/C and refrigeration disconnects, conductor/OCP sizing, MCA/MOCP labels, and HVAC equipment rules.

Keywords: HVAC, air conditioner, MCA, MOCP, condenser, disconnect

Related: 430, 422

Generator installation, marking, disconnecting means, and wiring references.

Keywords: generator, genset, standby, portable generator

Related: 250, 700, 701, 702

Transformer installation, ventilation, overcurrent protection, and vault references.

Keywords: transformer, dry type, vault, primary, secondary

Related: 240, 250

Battery installations, ventilation, disconnects, and energy storage tie-ins.

Keywords: battery, UPS battery, stationary battery

Related: 645, 706

Medium-voltage equipment rules and references.

Keywords: medium voltage, over 1000V, MV

Related: 110, 240

Hazardous location classification system and general Class/Division/Zone structure.

Keywords: hazardous location, classified, Class I, Division, Zone

Related: 501, 502, 503, 504, 505, 506

Flammable gas/vapor Class I wiring methods and equipment.

Keywords: Class I, explosionproof, sealoff, gas vapor

Related: 500, 504, 505

Combustible dust Class II wiring methods and equipment.

Keywords: Class II, dust, combustible dust

Related: 500, 506

Commercial garage classification and wiring concerns.

Keywords: commercial garage, repair garage, vehicle

Related: 500, 514

Gas station/fuel dispenser wiring and classified location references.

Keywords: gas station, fuel dispenser, service station

Related: 500, 501

Healthcare essential electrical systems, patient care spaces, grounding, receptacles, and branch requirements.

Keywords: healthcare, hospital, patient care, essential electrical system, 517

Related: 700, 701

Assembly occupancy wiring and equipment references.

Keywords: assembly, church, auditorium, occupancy

Related: 520, 525

Stage, theater, performance, and studio wiring references.

Keywords: theater, stage, performance, studio

Related: 518, 530

Event power, temporary wiring, and outdoor public event rules.

Keywords: fair, carnival, temporary event, festival

Related: 590

Agricultural building wiring, equipotential planes, corrosive/dusty/wet conditions.

Keywords: agricultural, barn, livestock, equipotential plane

Related: 250, 300

Dock and marina power, GFCI/GFPE, shore power, corrosion/wet location concerns.

Keywords: marina, dock, boat, shore power

Related: 250, 682

Sign circuits, disconnecting means, and outline lighting references.

Keywords: sign, neon, outline lighting

Related: 410

Elevator/lift electrical equipment, disconnects, and coordination references.

Keywords: elevator, lift, escalator, disconnect

Related: 430, 645

EV charging equipment, branch circuits, load management, GFCI references, and installation rules.

Keywords: EV, EVSE, charger, electric vehicle

Related: 210, 220, 250

Welder circuits, conductor sizing, duty cycle, and OCP references.

Keywords: welder, welding, duty cycle

Related: 240, 310

IT equipment rooms, UPS/data equipment, disconnects, and fire/smoke conditions.

Keywords: IT room, server room, data center, UPS

Related: 480, 700

Pipe organ electrical references.

Keywords: pipe organ

Related:

X-ray equipment branch circuit and control references.

Keywords: x-ray, medical equipment

Related: 517

Pool bonding, GFCI, equipment grounding, wet niche fixtures, fountains, and related installations.

Keywords: pool, hot tub, spa, fountain, bonding, equipotential

Related: 250, 555

Electrical work near bodies of water not otherwise covered.

Keywords: pond, lake, water, dock

Related: 555, 680

PV circuits, disconnects, rapid shutdown, labeling, grounding, and interconnection references.

Keywords: solar, PV, photovoltaic, rapid shutdown

Related: 705, 706

Fire pump power supply, disconnects, reliability, and emergency/standby coordination.

Keywords: fire pump, pump controller

Related: 700, 701

Emergency systems, wiring separation, transfer equipment, and life-safety power references.

Keywords: emergency system, life safety, generator, ATS

Related: 517, 701, 702

Legally required standby systems, transfer equipment, and standby wiring.

Keywords: legally required standby, standby, ATS

Related: 700, 702

Optional standby generators and transfer equipment for residential/commercial standby systems.

Keywords: optional standby, generator, transfer switch

Related: 445, 700, 701

Interconnection of power production sources such as PV with premises wiring.

Keywords: interconnection, backfeed, line side tap, solar

Related: 690, 706

Battery/energy storage systems, disconnects, location, and equipment references.

Keywords: ESS, battery storage, energy storage, inverter

Related: 480, 690, 705

Critical operations power systems for facilities requiring hardened power reliability.

Keywords: critical operations, COPS, mission critical

Related: 700, 701

Control wiring, power-limited circuits, Class 2/3, and separation from power conductors.

Keywords: Class 2, low voltage, control wire, power limited, thermostat

Related: 760, 800

Fire alarm circuit classifications, wiring methods, power-limited/non-power-limited circuits.

Keywords: fire alarm, FACP, notification, initiating, NAC

Related: 725, 770, 800

General communications circuit wiring and separation references.

Keywords: communications, low voltage, data, telecom

Related: 725, 805

Communications circuits and cabling references.

Keywords: communications circuit, phone, data

Related: 800

Coaxial cable/CATV grounding and bonding references.

Keywords: coax, CATV, antenna

Related: 800, 830

Network-powered broadband communications wiring references.

Keywords: broadband, network powered

Related: 800, 820

Conduit fill, conductor properties, resistance/reactance, and table-based calculations. Use exact NEC tables for final values.

Keywords: conduit fill, wire fill, table 1, table 4, table 5, resistance, reactance

Related: 300, 310, 314

Annex fill tables for raceway/conductor combinations. Informational; verify against adopted NEC usage.

Keywords: Annex C, fill table, conduit fill, EMT fill, PVC fill

Related: Chapter 9, 300