• CHAPTER39
    POWER AND LIGHTING DISTRIBUTION

    SECTIONE3901
    RECEPTACLE OUTLETS

    E3901.1 General.

    Outlets for receptacles rated at 125 volts, 15- and 20-amperes shall be provided in accordance with Sections E3901.2 through E3901.11. Receptacle outlets required by this section shall be in addition to any receptacle that is:

    1. 1.Part of a luminaire or appliance;

    2. 2.Located within cabinets or cupboards;

    3. 3.Controlled by a wall switch in accordance with Section E3903.2, Exception 1; or

    4. 4.Located over 5.5 feet (1676 mm) above the floor.

    Permanently installed electric baseboard heaters equipped with factory-installed receptacle outlets, or outlets provided as a separate assembly by the baseboard manufacturer shall be permitted as the required outlet or outlets for the wall space utilized by such permanently installed heaters. Such receptacle outlets shall not be connected to the heater circuits. (210.52)

    E3901.2 General purpose receptacle distribution.

    In every kitchen, family room, dining room, living room, parlor, library, den, sun room, bedroom, recreation room, or similar room or area of dwelling units, receptacle outlets shall be installed in accordance with the general provisions specified in Sections E3901.2.1 through E3901.2.3 (see Figure E3901.2).

    GENERAL USE RECEPTACLE DISTRIBUTION

    For SI: 1 foot = 304.8 mm.

    FIGURE E3901.2

    GENERAL USE RECEPTACLE DISTRIBUTION

    E3901.2.1 Spacing.

    Receptacles shall be installed so that no point measured horizontally along the floor line of any wall space is more than 6 feet (1829 mm), from a receptacle outlet. [210.52(A)(1)]

    E3901.2.2 Wall space.

    As used in this section, a wall space shall include the following: [210.52(A)(2)]

    1. 1.Any space that is 2 feet (610 mm) or more in width, including space measured around corners, and that is unbroken along the floor line by doorways and similar openings, fireplaces, and fixed cabinets.

    2. 2.The space occupied by fixed panels in exterior walls, excluding sliding panels.

    3. 3.The space created by fixed room dividers such as railings and freestanding bar-type counters.

    E3901.2.3 Floor receptacles.

    Receptacle outlets in floors shall not be counted as part of the required number of receptacle outlets except where located within 18 inches (457 mm) of the wall. [210.52(A)(3)]

    E3901.2.4 Countertop receptacles.

    Receptacles installed for countertop surfaces as specified in Section E3901.4 shall not be considered as the receptacles required by Section E3901.2. [210.52(A)(4)]

    E3901.3 Small appliance receptacles.

    In the kitchen, pantry, breakfast room, dining room, or similar area of a dwelling unit, the two or more 20-ampere small-appliance branch circuits required by Section E3703.2, shall serve all wall and floor receptacle outlets covered by Sections E3901.2 and E3901.4 and those receptacle outlets provided for refrigeration appliances. [210.52(B)(1)]

    Exceptions:

    1. 1.In addition to the required receptacles specified by Sections E3901.1 and E3901.2, switched receptacles supplied from a general-purpose branch circuit as defined in Section E3903.2, Exception 1 shall be permitted. [210.52(B)(1) Exception No. 1]

    2. 2.The receptacle outlet for refrigeration appliances shall be permitted to be supplied from an individual branch circuit rated at 15 amperes or greater. [210.52(B)(1) Exception No. 2]

    E3901.3.1 Other outlets prohibited.

    The two or more small-appliance branch circuits specified in Section E3901.3 shall serve no other outlets. [210.52(B)(2)]

    Exceptions:

    1. 1.A receptacle installed solely for the electrical supply to and support of an electric clock in any of the rooms specified in Section E3901.3. [210.52(B)(2) Exception No.1]

    2. 2.Receptacles installed to provide power for supplemental equipment and lighting on gas-fired ranges, ovens, and counter-mounted cooking units. [210.52(B)(2) Exception No.2]

    E3901.3.2 Limitations.

    Receptacles installed in a kitchen to serve countertop surfaces shall be supplied by not less than two small-appliance branch circuits, either or both of which shall also be permitted to supply receptacle outlets in the same kitchen and in other rooms specified in Section E3901.3. Additional small-appliance branch circuits shall be permitted to supply receptacle outlets in the kitchen and other rooms specified in Section E3901.3. A small-appliance branch circuit shall not serve more than one kitchen. [210.52(B)(3)]

    E3901.4 Countertop receptacles.

    In kitchens pantries, breakfast rooms, dining rooms and similar areas of dwelling units, receptacle outlets for countertop spaces shall be installed in accordance with Sections E3901.4.1 through E3901.4.5 (see Figure E3901.4). [210.52(C)]

    COUNTERTOP RECEPTACLES

    For SI: 1 foot = 304.8 mm.

    FIGURE E3901.4

    COUNTERTOP RECEPTACLES

    E3901.4.1 Wall countertop space.

    A receptacle outlet shall be installed at each wall countertop space 12 inches (305 mm) or wider. Receptacle outlets shall be installed so that no point along the wall line is more than 24 inches (610 mm), measured horizontally from a receptacle outlet in that space. [210.52(C)(1)]

    Exception: Receptacle outlets shall not be required on a wall directly behind a range, counter-mounted cooking unit or sink in the installation described in Figure E3901.4.1. [210.52(C)(1) Exception]

    DETERMINATION OF AREA BEHIND SINK OR RANGE

    For SI: 1 inch = 25.4 mm.

    FIGURE E3901.4.1

    DETERMINATION OF AREA BEHIND SINK OR RANGE

    E3901.4.2 Island countertop spaces.

    At least one receptacle outlet shall be installed at each island countertop space with a long dimension of 24 inches (610 mm) or greater and a short dimension of 12 inches (305 mm) or greater. [210.52(C)(2)]

    E3901.4.3 Peninsular countertop space.

    At least one receptacle outlet shall be installed at each peninsular countertop space with a long dimension of 24 inches (610 mm) or greater and a short dimension of 12 inches (305 mm) or greater. A peninsular countertop is measured from the connecting edge. [210.52(C)(3)]

    E3901.4.4 Separate spaces.

    Countertop spaces separated by range tops, refrigerators, or sinks shall be considered as separate countertop spaces in applying the requirements of Sections E3901.4.1, E3901.4.2 and E3901.4.3. Where a range, counter-mounted cooking unit, or sink is installed in an island or peninsular countertop and the depth of the countertop behind the range, counter-mounted cooking unit, or sink is less than 12 inches (305 mm), the range, counter-mounted cooking unit, or sink has divided the countertop space into two separate countertop spaces as defined in Section E3901.4.4. Each separate countertop space shall comply with the applicable requirements of this section. [210.52(C)(4)]

    E3901.4.5 Receptacle outlet location.

    Receptacle outlets shall be located not more than 20 inches (508 mm) above the countertop. Receptacle outlet assemblies installed in countertops shall be listed for the application. Receptacle outlets shall not be installed in a face-up position in the work surfaces or countertops. Receptacle outlets rendered not readily accessible by appliances fastened in place, appliance garages, sinks or rangetops as addressed in the exception to Section E3901.4.1, or appliances occupying dedicated space shall not be considered as these required outlets. [210.52(C)(5)]

    Exception: Receptacle outlets shall be permitted to be mounted not more than 12 inches (305 mm) below the countertop in construction designed for the physically impaired and for island and peninsular countertops where the countertop is flat across its entire surface and there are no means to mount a receptacle within 20 inches (508 mm) above the countertop, such as in an overhead cabinet. Receptacles mounted below the countertop in accordance with this exception shall not be located where the countertop extends more than 6 inches (152 mm) beyond its support base. [210.52(C)(5) Exception]

    E3901.5 Appliance receptacle outlets.

    Appliance receptacle outlets installed for specific appliances, such as laundry equipment, shall be installed within 6 feet (1829 mm) of the intended location of the appliance. (210.50(C)]

    E3901.6 Bathroom.

    At least one wall receptacle outlet shall be installed in bathrooms and such outlet shall be located within 36 inches (914 mm) of the outside edge of each lavatory basin. The receptacle outlet shall be located on a wall or partition that is adjacent to the lavatory basin location, located on the countertop, or installed on the side or face of the basin cabinet. The receptacle shall be located not more than 12 inches (305 mm) below the top of the basin.

    Receptacle outlets shall not be installed in a face-up position in the work surfaces or countertops in a bathroom basin location. Receptacle outlet assemblies installed in countertops shall be listed for the application. [210.52(D)]

    E3901.7 Outdoor outlets.

    Not less than one receptacle outlet that is readily accessible from grade level and located not more than 6 feet, 6 inches (1981 mm) above grade, shall be installed outdoors at the front and back of each dwelling unit having direct access to grade level. Balconies, decks, and porches that are accessible from inside of the dwelling unit shall have at least one receptacle outlet installed within the perimeter of the balcony, deck, or porch. The receptacle shall be located not more than 6 feet, 6 inches (1981 mm) above the balcony, deck, or porch surface. [210.52(E)]

    E3901.8 Laundry areas.

    Not less than one receptacle outlet shall be installed in areas designated for the installation of laundry equipment.

    E3901.9 Basements, garages and accessory buildings.

    Not less than one receptacle outlet, in addition to any provided for specific equipment, shall be installed in each separate unfinished portion of a basement, in each attached garage, and in each detached garage or accessory building that is provided with electrical power. The branch circuit supplying the receptacle(s) in a garage shall not supply outlets outside of the garage and not less than one receptacle outlet shall be installed for each motor vehicle space. [210.52(G)(1), (2), and (3)]

    E3901.10 Hallways.

    Hallways of 10 feet (3048 mm) or more in length shall have at least one receptacle outlet. The hall length shall be considered the length measured along the centerline of the hall without passing through a doorway. [210.52(H)]

    E3901.11 Foyers.

    Foyers that are not part of a hallway in accordance with Section E3901.10 and that have an area that is greater than 60 ft2 (5.57 m2) shall have a receptacle(s) located in each wall space that is 3 feet (914 mm) or more in width. Doorways, door-side windows that extend to the floor, and similar openings shall not be considered as wall space. [210.52(H)]

    E3901.12 HVAC outlet.

    A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet shall be installed at an accessible location for the servicing of heating, air-conditioning and refrigeration equipment. The receptacle shall be located on the same level and within 25 feet (7620 mm) of the heating, air-conditioning and refrigeration equipment. The receptacle outlet shall not be connected to the load side of the HVAC equipment disconnecting means. (210.63)

    Exception: A receptacle outlet shall not be required for the servicing of evaporative coolers. (210.63 Exception)

    SECTIONE3902
    GROUND-FAULT AND ARC-FAULT
    CIRCUIT-INTERRUPTER PROTECTION

    E3902.1 Bathroom receptacles.

    125-volt, single-phase, 15- and 20-ampere receptacles installed in bathrooms shall have ground-fault circuit-interrupter protection for personnel. [210.8(A)(1)]

    E3902.2 Garage and accessory building receptacles.

    125-volt, single-phase, 15- or 20-ampere receptacles installed in garages and grade-level portions of unfinished accessory buildings used for storage or work areas shall have ground-fault circuit-interrupter protection for personnel. [210.8(A)(2)]

    E3902.3 Outdoor receptacles.

    125-volt, single-phase, 15- and 20-ampere receptacles installed outdoors shall have ground-fault circuit-interrupter protection for personnel. [210.8(A)(3)]

    Exception: Receptacles as covered in Section E4101.7. [210.8(A)(3) Exception]

    E3902.4 Crawl space receptacles.

    Where a crawl space is at or below grade level, 125-volt, single-phase, 15- and 20-ampere receptacles installed in such spaces shall have ground-fault circuit-interrupter protection for personnel. [210.8(A)(4)]

    E3902.5 Unfinished basement receptacles.

    125-volt, single-phase, 15- and 20-ampere receptacles installed in unfinished basements shall have ground-fault circuit-interrupter protection for personnel. For purposes of this section, unfinished basements are defined as portions or areas of the basement not intended as habitable rooms and limited to storage areas, work areas, and similar areas. [210.8(A)(5)]

    Exception: A receptacle supplying only a permanently installed fire alarm or burglar alarm system. Receptacles installed in accordance with this exception shall not be considered as meeting the requirement of Section E3901.9. [210.8(A)(5) Exception]

    E3902.6 Kitchen receptacles.

    125-volt, single-phase, 15- and 20-ampere receptacles that serve countertop surfaces shall have ground-fault circuit-interrupter protection for personnel. [210.8(A)(6)]

    E3902.7 Sink receptacles.

    125-volt, single-phase, 15- and 20-ampere receptacles that are located within 6 feet (1829 mm) of the outside edge of a sink shall have ground-fault circuit-interrupter protection for personnel. Receptacle outlets shall not be installed in a face-up position in the work surfaces or countertops. [210.8(A)(7)]

    E3902.8 Bathtub or shower stall receptacles.

    125-volt, single phase, 15- and 20-ampere receptacles that are located within 6 feet (1829 mm) of the outside edge of a bathtub or shower stall shall have ground-fault circuit interrupter protection for personnel. [210.8(A)(8)]

    E3902.9 Laundry areas.

    125-volt, single-phase, 15- and 20-ampere receptacles installed in laundry areas shall have ground-fault circuit interrupter protection for personnel. [210.8(A)(9)]

    E3902.10 Kitchen dishwasher branch circuit.

    Ground-fault circuit-interrupter protection shall be provided for outlets that supply dishwashers in dwelling unit locations. [210.8(D)]

    E3902.11 Boathouse receptacles.

    125-volt, single-phase, 15- or 20-ampere receptacles installed in boathouses shall have ground-fault circuit-interrupter protection for personnel. [210.8(A)(8)]

    E3902.12 Boat hoists.

    Ground-fault circuit-interrupter protection for personnel shall be provided for 240-volt and less outlets that supply boat hoists. [210.8(C)]

    E3902.13 Electrically heated floors.

    Ground-fault circuit-interrupter protection for personnel shall be provided for electrically heated floors in bathrooms, kitchens and in hydromassage bathtub, spa and hot tub locations. [424.44(G)]

    E3902.14 Location of ground-fault circuit interrupters.

    Ground-fault circuit interrupters shall be installed in a readily accessible location. [210.8(A)]

    E3902.15 Location of arc-fault circuit interrupters.

    Arc-fault circuit interrupters shall be installed in readily accessible locations.

    E3902.16 Arc-fault circuit-interrupter protection.

    Branch circuits that supply 120-volt, single-phase, 15- and 20-ampere outlets installed in kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sun-rooms, recreations rooms, closets, hallways, laundry areas and similar rooms or areas shall be protected by any of the following: [210.12(A)]

    1. 1.A listed combination-type arc-fault circuit interrupter, installed to provide protection of the entire branch circuit. [210.12(A)(1)]

    2. 2.A listed branch/feeder-type AFCI installed at the origin of the branch-circuit in combination with a listed outlet branch-circuit type arc-fault circuit interrupter installed at the first outlet box on the branch circuit. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit. [210.12(A)(2)]

    3. 3.A listed supplemental arc protection circuit breaker installed at the origin of the branch circuit in combination with a listed outlet branch-circuit type arc-fault circuit interrupter installed at the first outlet box on the branch circuit where all of the following conditions are met:

      1. 3.1.The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arc-fault circuit interrupter.

      2. 3.2.The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 50 feet (15.2 m) for 14 AWG conductors and 70 feet (21.3 m) for 12 AWG conductors.

      3. 3.3.The first outlet box on the branch circuit shall be marked to indicate that it is the first outlet on the circuit. [210.12(A)(3)]

    4. 4.A listed outlet branch-circuit type arc-fault circuit interrupter installed at the first outlet on the branch circuit in combination with a listed branch-circuit overcurrent protective device where all of the following conditions are met:

      1. 4.1.The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arc-fault circuit interrupter.

      2. 4.2.The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 50 feet (15.2 m) for 14 AWG conductors and 70 feet (21.3 m) for 12 AWG conductors.

      3. 4.3.The first outlet box on the branch circuit shall be marked to indicate that it is the first outlet on the circuit.

      4. 4.4.The combination of the branch-circuit overcurrent device and outlet branch-circuit AFCI shall be identified as meeting the requirements for a system combination-type AFCI and shall be listed as such. [210.12(A)(4)]

    5. 5.Where metal outlet boxes and junction boxes and RMC, IMC, EMT, Type MC or steel-armored Type AC cables meeting the requirements of Section E3908.8, metal wireways or metal auxiliary gutters are installed for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, a listed outlet branch-circuit type AFCI installed at the first outlet shall be considered as providing protection for the remaining portion of the branch circuit. [210.12(A)(5)]

    6. 6.Where a listed metal or nonmetallic conduit or tubing or Type MC cable is encased in not less than 2 inches (50.8 mm) of concrete for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, a listed outlet branch-circuit type AFCI installed at the first outlet shall be considered as providing protection for the remaining portion of the branch circuit. [210.12(A)(6)]

    Exception: AFCI protection is not required for an individual branch circuit supplying only a fire alarm system where the branch circuit is wired with metal outlet and junction boxes and RMC, IMC, EMT or steel-sheathed armored cable Type AC or Type MC meeting the requirements of Section E3908.8.

    E3902.17 Arc-fault circuit interrupter protection for branch circuit extensions or modifications.

    Where branch-circuit wiring is modified, replaced, or extended in any of the areas specified in Section E3902.16, the branch circuit shall be protected by one of the following:

    1. 1.A combination-type AFCI located at the origin of the branch circuit

    2. 2.An outlet branch-circuit type AFCI located at the first receptacle outlet of the existing branch circuit. [210.12(B)]

    Exception: AFCI protection shall not be required where the extension of the existing conductors is not more than 6 feet (1.8 m) in length and does not include any additional outlets or devices. [210.12(B) Exception]

    SECTIONE3903
    LIGHTING OUTLETS

    E3903.1 General.

    Lighting outlets shall be provided in accordance with Sections E3903.2 through E3903.4. [210.70(A)]

    E3903.2 Habitable rooms.

    At least one wall switch-controlled lighting outlet shall be installed in every habitable room and bathroom. [210.70(A)(1)]

    Exceptions:

    1. 1.In other than kitchens and bathrooms, one or more receptacles controlled by a wall switch shall be considered equivalent to the required lighting outlet. [210.70(A)(1) Exception No. 1]

    2. 2.Lighting outlets shall be permitted to be controlled by occupancy sensors that are in addition to wall switches, or that are located at a customary wall switch location and equipped with a manual override that will allow the sensor to function as a wall switch. [210.70(A)(1) Exception No. 2]

    E3903.3 Additional locations.

    At least one wall-switch-controlled lighting outlet shall be installed in hallways, stairways, attached garages, and detached garages with electric power. At least one wall-switch-controlled lighting outlet shall be installed to provide illumination on the exterior side of each outdoor egress door having grade level access, including outdoor egress doors for attached garages and detached garages with electric power. A vehicle door in a garage shall not be considered as an outdoor egress door. Where one or more lighting outlets are installed for interior stairways, there shall be a wall switch at each floor level and landing level that includes an entryway to control the lighting outlets where the stairway between floor levels has six or more risers. [210.70(A)(2)]

    Exception: In hallways, stairways, and at outdoor egress doors, remote, central, or automatic control of lighting shall be permitted. [210.70(A)(2) Exception]

    E3903.4 Storage or equipment spaces.

    In attics, under-floor spaces, utility rooms and basements, at least one lighting outlet shall be installed where these spaces are used for storage or contain equipment requiring servicing. Such lighting outlet shall be controlled by a wall switch or shall have an integral switch. At least one point of control shall be at the usual point of entry to these spaces. The lighting outlet shall be provided at or near the equipment requiring servicing. [210.70(A)(3)]

    SECTIONE3904
    GENERAL INSTALLATION REQUIREMENTS

    E3904.1 Electrical continuity of metal raceways and enclosures.

    Metal raceways, cable armor and other metal enclosures for conductors shall be mechanically joined together into a continuous electric conductor and shall be connected to all boxes, fittings and cabinets so as to provide effective electrical continuity. Raceways and cable assemblies shall be mechanically secured to boxes, fittings cabinets and other enclosures. (300.10)

    Exception: Short sections of raceway used to provide cable assemblies with support or protection against physical damage. (300.10 Exception No. 1)

    E3904.2 Mechanical continuity—raceways and cables.

    Metal or nonmetallic raceways, cable armors and cable sheaths shall be continuous between cabinets, boxes, fittings or other enclosures or outlets.

    Exception: Short sections of raceway used to provide cable assemblies with support or protection against physical damage. (300.12 Exception No. 1)

    E3904.3 Securing and supporting.

    Raceways, cable assemblies, boxes, cabinets and fittings shall be securely fastened in place. (300.11)

    E3904.3.1 Prohibited means of support.

    Cable wiring methods shall not be used as a means of support for other cables, raceways and nonelectrical equipment. [300.11(C)]

    E3904.4 Raceways as means of support.

    Raceways shall be used as a means of support for other raceways, cables or non-electric equipment only under the following conditions:

    1. 1.Where the raceway or means of support is identified as a means of support; or

    2. 2.Where the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 circuit conductors or cables that are solely for the purpose of connection to the control circuits of the equipment served by such raceway; or

    3. 3.Where the raceway is used to support boxes or conduit bodies in accordance with Sections E3906.8.4 and E3906.8.5. [300.11(B)]

    E3904.5 Raceway installations.

    Raceways shall be installed complete between outlet, junction or splicing points prior to the installation of conductors. (300.18)

    Exception: Short sections of raceways used to contain conductors or cable assemblies for protection from physical damage shall not be required to be installed complete between outlet, junction, or splicing points. (300.18 Exception)

    E3904.6 Conduit and tubing fill.

    The maximum number of conductors installed in conduit or tubing shall be in accordance with Tables E3904.6(1) through E3904.6(10). (300.17, Chapter 9, Table 1 and Annex C)

    TABLE E3904.6(1) (Annex C, Table C.1)

    MAXIMUM NUMBER OF CONDUCTORS IN ELECTRICAL METALLIC TUBING (EMT)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2144711202746
    12369172338
    10258131830
    81247916
    61135813
    41124610
    3111459
    2111347
    1011135
    1/0011124
    2/0011124
    3/0001113
    4/0001113
    TW, THHW, THW, THW-21481525435896
    1261119334574
    105814243355
    8258131830
    RHHa, RHWa, RHW-2a1461016283964
    124813233151
    103610182440
    8146101424
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2613481118
    41136813
    31135712
    21124610
    1111347
    1/0011236
    2/0011135
    3/0011124
    4/0001113
    THHN, THWN, THWN-2141222356184138
    12916264561101
    1051016283863
    8369162236
    6247121626
    412471016
    31136813
    21135711
    1111458
    1/0111347
    2/0011236
    3/0011135
    4/0011124
    XHH, XHHW, XHHW-21481525435896
    1261119334574
    105814243355
    8258131830
    6136101422
    412471016
    31136814
    21135711
    1111458
    1/0111347
    2/0011236
    3/0011135
    4/0011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(2) (Annex C, Table C.2)

    MAXIMUM NUMBER OF CONDUCTORS IN ELECTRICAL NONMETALLIC TUBING (ENT)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2143610192643
    12259162236
    10147131729
    81136915
    61135712
    4112469
    3111358
    2011347
    1011135
    1/0001124
    2/0001113
    RHH, RHW, RHW-23/0001113
    4/0001112
    TW, THHW, THW, THW-21471322405592
    1251017314271
    104713233252
    8147131729
    RHHa, RHWa, RHW-2a144815273761
    123712212949
    10359172338
    8135101423
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2612471017
    41135813
    31125711
    2112469
    1011346
    1/0011235
    2/0011135
    3/0001124
    4/0001113
    THHN, THWN, THWN-2141018325880132
    1271323425896
    104815263660
    8258152135
    6136111525
    41147915
    31135813
    21125611
    THHN, THWN, THWN-21111358
    1/0011347
    2/0011235
    3/0011134
    4/0001124
    XHH, XHHW, XHHW-21471322405592
    1251017314271
    104713233252
    8147131729
    613591321
    41147915
    31136813
    21125611
    1111358
    1/0011347
    2/0011236
    3/0011135
    4/0001124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(3) (Annex C, Table C.3)

    MAXIMUM NUMBER OF CONDUCTORS IN FLEXIBLE METALLIC CONDUIT (FMC)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2144711172544
    12369142137
    10357111730
    81246915
    61135712
    41124510
    3111357
    RHH, RHW, RHW-22111347
    1011125
    1/0011124
    2/0011113
    3/0001113
    TW, THHW, THW, THW-21491523365394
    1271118284172
    105813213054
    8357111730
    RHHa, RHWa, RHW-2a1461015243562
    125812192850
    104610152239
    814691323
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2613471018
    41135713
    31134611
    21124510
    1111247
    1/0011136
    2/0011135
    3/0011124
    4/0001113
    4/0001112
    THHN, THWN, THWN-2141322335276134
    1291624385698
    1061015243562
    8369142035
    THHN, THWN, THWN-26246101425
    41246916
    31135713
    21134611
    1111348
    1/0111247
    2/0011136
    3/0011125
    4/0011114
    XHH, XHHW, XHHW-21491523365394
    1271118284172
    105813213054
    8357111730
    613581222
    41246916
    31135713
    21134611
    1111358
    1/0111247
    2/0011236
    3/0011135
    4/0011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(4) (Annex C, Table C.4)

    MAXIMUM NUMBER OF CONDUCTORS IN INTERMEDIATE METALLIC CONDUIT (IMC)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2144813223049
    124611182541
    10358152033
    813481017
    61136814
    41135611
    3112469
    2111358
    1011235
    1/0011134
    2/0011124
    3/0001113
    4/0001113
    TW, THHW, THW, THW-2141017274764104
    1271321364980
    105915273659
    8358152033
    RHHa, RHWa, RHW-2a1461118314269
    125914253456
    104711192643
    8247121626
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2613591220
    41246915
    31136813
    21135611
    1111347
    1/0111346
    2/0011235
    3/0011134
    4/0011124
    THHN, THWN, THWN-2141424396891149
    121017294967109
    1061118314268
    83610182439
    6247131728
    413481017
    31246915
    21135712
    1112459
    1/0111348
    2/0111346
    THHN, THWN, THWN-23/0011235
    2/0011124
    XHH, XHHW, XHHW-2141017274764104
    1271321364980
    105915273659
    8358152033
    6146111524
    413481118
    31247915
    21135712
    1112459
    1/0111358
    2/0111346
    3/0011235
    4/0011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(5) (Annex C, Table C.5)

    MAXIMUM NUMBER OF CONDUCTORS IN LIQUID-TIGHT FLEXIBLE NONMETALLIC CONDUIT (FNMC-B)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    3/81/23/4111/411/22
    RHH, RHW, RHW-21424712212744
    1213610172236
    101358141829
    81124791
    611136712
    40112469
    RHH, RHW, RHW-230111458
    20111347
    10011135
    1/00011124
    2/00011113
    3/00001113
    4/00001112
    TW, THHW, THW, THW-214591525445793
    12471219334371
    1035914253253
    81358141829
    RHHa, RHWa, RGW-2a14361016293862
    1235813233050
    1013610182339
    81146111423
    RHHa, RHWa, RHW-2a,TW, THW, THHW, THW-26113581118
    411136813
    311135711
    20112469
    10111347
    1/00011236
    2/00011235
    3/00011124
    4/00001113
    THHN, THWN, THWN-21481322366381133
    12591626465997
    10361016293761
    81369162135
    THHN, THWN, THWN-261247121525
    411247915
    311136813
    211135711
    10111458
    1/00111347
    2/00011236
    3/00011135
    4/00011124
    XHH, XHHW, XHHW-214591525445793
    12471219334371
    1035914253253
    81358141829
    61136101322
    411247916
    311136813
    211135711
    10111458
    1/00111347
    2/00011236
    3/00011135
    4/00011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(6) (Annex C, Table C.6)

    MAXIMUM NUMBER OF CONDUCTORS IN LIQUID-TIGHT FLEXIBLE NONMETALLIC CONDUIT (FNMC-A)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    3/81/23/4111/411/22
    RHH, RHW, RHW-21424711202745
    121369172338
    101358131830
    811247916
    611135713
    401124610
    30111458
    20111347
    10011135
    1/00011124
    2/00011114
    3/00001113
    4/00001113
    TW, THHW, THW, THW-214591524435896
    12471219334474
    1035914243355
    81358131830
    RHHa, RHWa, RHW-2a14361016283864
    1234813233151
    1013610182440
    81146101424
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-26113481118
    411136813
    311135711
    201124610
    10111347
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-21/00011236
    2/00011135
    3/00011124
    4/00001113
    THHN, THWN, THWN-21481322356283137
    125916254560100
    10361016283863
    81369162236
    61246121626
    411247916
    311136813
    211135711
    10111458
    1/00111347
    2/00011236
    3/00011135
    4/00011124
    XHH, XHHW, XHHW-214591524435896
    12471219334474
    1035914243355
    81358131830
    61135101322
    4112471016
    311136814
    211135711
    10111458
    XHH, XHHW, XHHW-21/00111347
    2/00011236
    3/00011135
    4/00011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(7) (Annex C, Table C.7)

    MAXIMUM NUMBER OF CONDUCTORS IN LIQUID-TIGHT FLEXIBLE METAL CONDUIT (LFMC)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2144712212744
    123610172236
    10358141829
    81247915
    61136712
    4112469
    3111458
    2111347
    1011135
    1/0011124
    2/0011113
    3/0001113
    4/0001112
    TW, THHW, THW, THW-21491525445793
    1271219334371
    105914253253
    8358141829
    RHHa, RHWa, RHW-2a, THHW, THW, THW-21461016293862
    125813233050
    103610182339
    8146111423
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2613581118
    41136813
    31135711
    2112469
    1111347
    1/0011236
    2/0011235
    3/0011124
    4/0001113
    THHN, THWN, THWN-2141322366381133
    1291626465997
    1061016293761
    8369162135
    6247121525
    41247915
    31136813
    21135711
    1111458
    1/0111347
    2/0011236
    3/0011135
    4/0011124
    XHH, XHHW, XHHW-21491525445793
    1271219334371
    105914253253
    8358141829
    XHH, XHHW, XHHW-26136101322
    41247916
    31136813
    21135711
    1111458
    1/0111347
    2/0011236
    3/0011135
    4/0011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(8) (Annex C, Table C.8)

    MAXIMUM NUMBER OF CONDUCTORS IN RIGID METAL CONDUIT (RMC)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2144712212846
    123610172338
    10358141931
    812471016
    61136813
    41124610
    3112459
    2111347
    1011135
    1/0011124
    2/0011124
    3/0001113
    4/0001113
    TW, THHW, THW, THW-21491525445998
    1271219334575
    105914253456
    8358141931
    RHHa, RHWa, RHW-2a1461017293965
    125813233252
    103610182541
    8146111524
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2613581118
    41136814
    31135712
    21124610
    1111347
    1/0011236
    2/0011235
    3/0011124
    4/0001113
    THHN, THWN, THWN-2141322366385140
    12916264662102
    1061017293964
    8369162237
    6247121627
    412471016
    31136814
    21135711
    1111458
    THHN, THWN, THWN-21/0111347
    2/0011236
    3/0011135
    4/0011124
    XHH, XHHW, XHHW-21491525445998
    1271219334575
    105914253456
    8358141931
    6136101423
    412471016
    31136814
    21135712
    1111459
    1/0111347
    2/0011236
    3/0011135
    4/0011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(9) (Annex C, Table C.9)

    MAXIMUM NUMBER OF CONDUCTORS IN RIGID PVC CONDUIT, SCHEDULE 80 (PVC-80)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-214359172339
    12247141932
    10136111526
    81136813
    61124611
    4111358
    RHH, RHW, RHW-23011347
    2011346
    1011124
    1/0001113
    2/0001113
    3/0001113
    4/0000112
    TW, THHW, THW, THW-21461120354982
    125915273863
    103611202847
    8136111526
    RHHa, RHWa, RHW-2a144813233255
    123610192644
    10258152034
    813591220
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-261137916
    41135712
    31124610
    2111358
    1011236
    1/0011135
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-22/0011124
    3/0001113
    4/0001113
    THHN, THWN, THWN-214917285170118
    1261220375186
    104713233254
    8247131831
    613591322
    41136814
    31135712
    21124610
    1011347
    1/0011236
    2/0011135
    3/0011124
    4/0001113
    XHH, XHHW, XHHW-21461120354982
    125915273863
    103611202847
    81361181526
    61241119
    XHH, XHHW, XHHW-21461120354982
    125915273863
    103611202847
    8136111526
    612481119
    41136814
    31135712
    21124610
    1011347
    1/0011236
    2/0011135
    3/0011124
    4/0001113

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    TABLE E3904.6(10) (Annex C, Table C.10)

    MAXIMUM NUMBER OF CONDUCTORS IN RIGID PVC CONDUIT SCHEDULE 40 (PVC-40)a

    TYPE LETTERSCONDUCTOR SIZE AWG/kcmilTRADE SIZES (inches)
    1/23/4111/411/22
    RHH, RHW, RHW-2144711202745
    12359162237
    10247131830
    81247915
    61135712
    41124610
    3111458
    2111347
    RHH, RHW, RHW-21011135
    1/0011124
    2/0001113
    3/0001113
    4/0001112
    TW, THHW, THW, THW-21481424425794
    1261118324472
    104813243254
    8247131830
    RHHa, RHWa, RHW-2a145916283863
    124813223050
    103610172439
    8136101423
    RHHa, RHWa, RHW-2a, TW, THW, THHW, THW-2612481118
    41136813
    31135711
    21124610
    1011347
    1/0011236
    2/0011135
    3/0011124
    4/0001113
    THHN, THWN, THWN-2141121346082135
    1281525435999
    105915273762
    8359162136
    THHN, THWN, THWN-26146111526
    41247916
    31136813
    21135711
    1111358
    1/0111347
    2/0011236
    3/0011135
    4/0011124
    XHH, XHHW, XHHW-21481424425794
    1261118324472
    104813243254
    8247131830
    6135101322
    41247916
    31136813
    21135711
    1111358
    1/0111347
    2/0011236
    3/0011135
    4/0011124

    For SI: 1 inch = 25.4 mm.

    1. a.Types RHW, and RHW-2 without outer covering.

    E3904.7 Air handling-stud cavity and joist spaces.

    Where wiring methods having a nonmetallic covering pass through stud cavities and joist spaces used for air handling, such wiring shall pass through such spaces perpendicular to the long dimension of the spaces. [300.22(C) Exception]

    SECTIONE3905
    BOXES, CONDUIT BODIES AND FITTINGS

    E3905.1 Box, conduit body or fitting—where required.

    A box or conduit body shall be installed at each conductor splice point, outlet, switch point, junction point and pull point except as otherwise permitted in Sections E3905.1.1 through E3905.1.6.

    Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed. (300.15)

    E3905.1.1 Equipment.

    An integral junction box or wiring compartment that is part of listed equipment shall be permitted to serve as a box or conduit body. [300.15(B)]

    E3905.1.2 Protection.

    A box or conduit body shall not be required where cables enter or exit from conduit or tubing that is used to provide cable support or protection against physical damage. A fitting shall be provided on the end(s) of the conduit or tubing to protect the cable from abrasion. [300.15(C)]

    E3905.1.3 Integral enclosure.

    A wiring device with integral enclosure identified for the use, having brackets that securely fasten the device to walls or ceilings of conventional on-site frame construction, for use with nonmetallic-sheathed cable, shall be permitted in lieu of a box or conduit body. [300.15(E)]

    E3905.1.4 Fitting.

    A fitting identified for the use shall be permitted in lieu of a box or conduit body where such fitting is accessible after installation and does not contain spliced or terminated conductors. [300.15(F)]

    E3905.1.5 Buried conductors.

    Splices and taps in buried conductors and cables shall not be required to be enclosed in a box or conduit body where installed in accordance with Section E3803.4.

    E3905.1.6 Luminaires.

    Where a luminaire is listed to be used as a raceway, a box or conduit body shall not be required for wiring installed therein. [300.15(J)]

    E3905.2 Metal boxes.

    Metal boxes shall be grounded. (314.4)

    E3905.3 Nonmetallic boxes.

    Nonmetallic boxes shall be used only with cabled wiring methods with entirely nonmetallic sheaths, flexible cords and nonmetallic raceways. (314.3)

    Exceptions:

    1. 1.Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways and metal-armored cables. (314.3 Exception No. 1)

    2. 2.Where integral bonding means with a provision for attaching an equipment grounding jumper inside the box are provided between all threaded entries in nonmetallic boxes listed for the purpose, nonmetallic boxes shall be permitted to be used with metal raceways and metal-armored cables. (314.3 Exception No. 2)

    E3905.3.1 Nonmetallic-sheathed cable and nonmetallic boxes.

    Where nonmetallic-sheathed cable is used, the cable assembly, including the sheath, shall extend into the box not less than 1/4 inch (6.4 mm) through a nonmetallic-sheathed cable knockout opening. (314.7(C)]

    E3905.3.2 Securing to box.

    Wiring methods shall be secured to the boxes. [314.17(C)]

    Exception: Where nonmetallic-sheathed cable is used with boxes not larger than a nominal size of 21/4 inches by 4 inches (57 mm by 102 mm) mounted in walls or ceilings, and where the cable is fastened within 8 inches (203 mm) of the box measured along the sheath, and where the sheath extends through a cable knockout not less than 1/4 inch (6.4 mm), securing the cable to the box shall not be required. [314.17(C) Exception]

    E3905.3.3 Conductor rating.

    Nonmetallic boxes shall be suitable for the lowest temperature-rated conductor entering the box. [314.17(C)]

    E3905.4 Minimum depth of boxes for outlets, devices, and utilization equipment.

    Outlet and device boxes shall have an approved depth to allow equipment installed within them to be mounted properly and without the likelihood of damage to conductors within the box. (314.24)

    E3905.4.1 Outlet boxes without enclosed devices or utilization equipment.

    Outlet boxes that do not enclose devices or utilization equipment shall have an internal depth of not less than 1/2 inch (12.7 mm). [314.24(A)]

    E3905.4.2 Utilization equipment.

    Outlet and device boxes that enclose devices or utilization equipment shall have a minimum internal depth that accommodates the rearward projection of the equipment and the size of the conductors that supply the equipment. The internal depth shall include that of any extension boxes, plaster rings, or raised covers. The internal depth shall comply with all of the applicable provisions that follow. [314.24(B)]

    Exception: Utilization equipment that is listed to be installed with specified boxes.

    1. 1.Large equipment. Boxes that enclose devices or utilization equipment that projects more than 17/8 inches (48 mm) rearward from the mounting plane of the box shall have a depth that is not less than the depth of the equipment plus 1/4 inch (6.4 mm). [314.24(B)(1)]

    2. 2.Conductors larger than 4 AWG. Boxes that enclose devices or utilization equipment supplied by conductors larger than 4 AWG shall be identified for their specific function. [314.24(B)(2)]

    3. 3.Conductors 8, 6, or 4 AWG. Boxes that enclose devices or utilization equipment supplied by 8, 6, or 4 AWG conductors shall have an internal depth that is not less than 21/16 inches (52.4 mm). [314.24(B)(3)]

    4. 4.Conductors 12 or 10 AWG. Boxes that enclose devices or utilization equipment supplied by 12 or 10 AWG conductors shall have an internal depth that is not less than 13/16 inches (30.2 mm). Where the equipment projects rearward from the mounting plane of the box by more than 1 inch (25.4 mm), the box shall have a depth that is not less than that of the equipment plus 1/4 inch (6.4 mm). [314.24(B)(4)]

    5. 5.Conductors 14 AWG and smaller. Boxes that enclose devices or utilization equipment supplied by 14 AWG or smaller conductors shall have a depth that is not less than 15/16 inch (23.8 mm). [314.24(B)(5)]

    E3905.5 Boxes enclosing flush-mounted devices.

    Boxes enclosing flush-mounted devices shall be of such design that the devices are completely enclosed at the back and all sides and shall provide support for the devices. Screws for supporting the box shall not be used for attachment of the device contained therein. (314.19)

    E3905.6 Boxes at luminaire outlets.

    Outlet boxes used at luminaire or lampholder outlets shall be designed for the support of luminaires and lampholders and shall be installed as required by Section E3904.3. [314.27(A)]

    E3905.6.1 Vertical surface outlets.

    Boxes used at luminaire or lampholder outlets in or on a vertical surface shall be identified and marked on the interior of the box to indicate the maximum weight of the luminaire or lamp holder that is permitted to be supported by the box if other than 50 pounds (22.7 kg). [314.27(A)(1)]

    Exception: A vertically-mounted luminaire or lampholder weighing not more than 6 pounds (2.7 kg) shall be permitted to be supported on other boxes or plaster rings that are secured to other boxes, provided that the luminaire or its supporting yoke is secured to the box with not fewer than two No. 6 or larger screws. [314.27(A)(1) Exception]

    E3905.6.2 Ceiling outlets.

    For outlets used exclusively for lighting, the box shall be designed or installed so that a luminaire or lampholder can be attached. Such boxes shall be capable of supporting a luminaire weighing up to 50 pounds (22.7 kg). A luminaire that weighs more than 50 pounds (22.7 kg) shall be supported independently of the outlet box, unless the outlet box is listed and marked on the interior of the box to indicate the maximum weight that the box is permitted to support. [314.27(A)(2)]

    E3905.7 Floor boxes.

    Where outlet boxes for receptacles are installed in the floor, such boxes shall be listed specifically for that application. [314.27(B)]

    E3905.8 Boxes at fan outlets.

    Outlet boxes and outlet box systems used as the sole support of ceiling-suspended fans (paddle) shall be marked by their manufacturer as suitable for this purpose and shall not support ceiling-suspended fans (paddle) that weigh more than 70 pounds (31.8 kg). For outlet boxes and outlet box systems designed to support ceiling-suspended fans (paddle) that weigh more than 35 pounds (15.9 kg), the required marking shall include the maximum weight to be supported.

    Where spare, separately switched, ungrounded conductors are provided to a ceiling-mounted outlet box and such box is in a location acceptable for a ceiling-suspended (paddle) fan, the outlet box or outlet box system shall be listed for sole support of a ceiling-suspended (paddle) fan. [314.27(C)]

    E3905.9 Utilization equipment.

    Boxes used for the support of utilization equipment other than ceiling-suspended (paddle) fans shall meet the requirements of Sections E3905.6.1 and E3905.6.2 for the support of a luminaire that is the same size and weight. [314.27(D)]

    Exception: Utilization equipment weighing not more than 6 pounds (2.7 kg) shall be permitted to be supported on other boxes or plaster rings that are secured to other boxes, provided that the equipment or its supporting yoke is secured to the box with not fewer than two No. 6 or larger screws. [314.27(D) Exception]

    E3905.10 Conduit bodies and junction, pull and outlet boxes to be accessible.

    Conduit bodies and junction, pull and outlet boxes shall be installed so that the wiring therein can be accessed without removing any part of the building or structure or, in underground circuits, without excavating sidewalks, paving, earth or other substance used to establish the finished grade. (314.29)

    Exception: Boxes covered by gravel, light aggregate or noncohesive granulated soil shall be listed for the application, and the box locations shall be effectively identified and access shall be provided for excavation. (314.29 Exception)

    E3905.11 Damp or wet locations.

    In damp or wet locations, boxes, conduit bodies and fittings shall be placed or equipped so as to prevent moisture from entering or accumulating within the box, conduit body or fitting. Boxes, conduit bodies and fittings installed in wet locations shall be listed for use in wet locations. Where drainage openings are installed in the field in boxes or conduit bodies listed for use in damp or wet locations, such openings shall be approved and not larger than 1/4 inch (6.4 mm). For listed drain fittings, larger openings are permitted where installed in the field in accordance with the manufacturer’s instructions. (314.15)

    E3905.12 Number of conductors in outlet, device, and junction boxes, and conduit bodies.

    Boxes and conduit bodies shall be of an approved size to provide free space for all enclosed conductors. In no case shall the volume of the box, as calculated in Section E3905.12.1, be less than the box fill calculation as calculated in Section E3905.12.2. The minimum volume for conduit bodies shall be as calculated in Section E3905.12.3. The provisions of this section shall not apply to terminal housings supplied with motors or generators. (314.16)

    E3905.12.1 Box volume calculations.

    The volume of a wiring enclosure (box) shall be the total volume of the assembled sections, and, where used, the space provided by plaster rings, domed covers, extension rings, etc., that are marked with their volume in cubic inches or are made from boxes the dimensions of which are listed in Table E3905.12.1. [314.16(A)]

    TABLE E3905.12.1 [Table 314.16(A)]

    MAXIMUM NUMBER OF CONDUCTORS IN METAL BOXESa

    BOX DIMENSIONS (inches trade size and type)MAXIMUM CAPACITY (cubic inches)MAXIMUM NUMBER OF CONDUCTORSa
    18 Awg16 Awg14 Awg12 Awg10 Awg8 Awg6 Awg
    4 × 11/4 round or octagonal12.58765542
    4 × 11/2 round or octagonal15.510876653
    4 × 21/8 round or octagonal21.51412109874
    4 × 11/4 square18.0121098763
    4 × 11/2 square21.01412109874
    4 × 21/8 square30.32017151312106
    411/16 × 11/4 square25.5171412111085
    411/16 × 11/2 square29.5191614131195
    411/16 × 21/8 square42.02824211816148
    3 × 2 × 11/2 device7.55433321
    3 × 2 × 2 device10.06554432
    3 × 2 × 21/4 device10.57654432
    3 × 2 × 21/2 device12.58765542
    3 × 2 × 23/4 device14.09876542
    3 × 2 × 31/2 device18.0121098763
    4 × 21/8 × 11/2 device10.36554432
    4 × 21/8 × 17/8 device13.08765542
    4 × 21/8 × 21/8 device14.59876542
    33/4 × 2 × 21/2 masonry box/gang14.09876542
    33/4 × 2 × 31/2 masonry box/gang21.01412109874

    For SI: 1 inch = 25.4 mm, 1 cubic inch = 16.4 cm3.

    1. a.Where volume allowances are not required by Sections E3905.12.2.2 through E3905.12.2.5.

    E3905.12.1.1 Standard boxes.

    The volumes of standard boxes that are not marked with a cubic-inch capacity shall be as given in Table E3905.12.1. [314.16(A)(1)]

    E3905.12.1.2 Other boxes.

    Boxes 100 cubic inches (1640 cm3) or less, other than those described in Table E3905.12.1, and nonmetallic boxes shall be durably and legibly marked by the manufacturer with their cubic-inch capacity. Boxes described in Table E3905.12.1 that have a larger cubic inch capacity than is designated in the table shall be permitted to have their cubic-inch capacity marked as required by this section. [314.16(A)(2)]

    E3905.12.2 Box fill calculations.

    The volumes in Section E3905.12.2.1 through Section E3905.12.2.5, as applicable, shall be added together. No allowance shall be required for small fittings such as locknuts and bushings. [314.16(B)]

    E3905.12.2.1 Conductor fill.

    Each conductor that originates outside the box and terminates or is spliced within the box shall be counted once, and each conductor that passes through the box without splice or termination shall be counted once. Each loop or coil of unbroken conductor having a length equal to or greater than twice that required for free conductors by Section E3406.11.3, shall be counted twice. The conductor fill, in cubic inches, shall be computed using Table E3905.12.2.1. A conductor, no part of which leaves the box, shall not be counted. [314.16(B)(1)]

    Exception: An equipment grounding conductor or not more than four fixture wires smaller than No. 14, or both, shall be permitted to be omitted from the calculations where such conductors enter a box from a domed fixture or similar canopy and terminate within that box. [314.16(B)(1) Exception]

    TABLE E3905.12.2.1 [Table 314.16(B)]

    VOLUME ALLOWANCE REQUIRED PER CONDUCTOR

    SIZE OF CONDUCTORFREE SPACE WITHIN BOX FOR EACH CONDUCTOR (cubic inches)
    18 AWG1.50
    16 AWG1.75
    14 AWG2.00
    12 AWG2.25
    10 AWG2.50
    8 AWG3.00
    6 AWG5.00

    For SI: 1 cubic inch = 16.4 cm3.

    E3905.12.2.2 Clamp fill.

    Where one or more internal cable clamps, whether factory or field supplied, are present in the box, a single volume allowance in accordance with Table E3905.12.2.1 shall be made based on the largest conductor present in the box. An allowance shall not be required for a cable connector having its clamping mechanism outside of the box. A clamp assembly that incorporates a cable termination for the cable conductors shall be listed and marked for use with specific nonmetallic boxes. Conductors that originate within the clamp assembly shall be included in conductor fill calculations provided in Section E3905.12.2.1 as though they entered from outside of the box. The clamp assembly shall not require a fill allowance, but, the volume of the portion of the assembly that remains within the box after installation shall be excluded from the box volume as marked in accordance with Section E3905.12.1.2. [314.16(B)(2)]

    E3905.12.2.3 Support fittings fill.

    Where one or more fixture studs or hickeys are present in the box, a single volume allowance in accordance with Table E3905.12.2.1 shall be made for each type of fitting based on the largest conductor present in the box. [314.16(B)(3)]

    E3905.12.2.4 Device or equipment fill.

    For each yoke or strap containing one or more devices or equipment, a double volume allowance in accordance with Table E3905.12.2.1 shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap. For a device or utilization equipment that is wider than a single 2-inch (51 mm) device box as described in Table E3905.12.1, a double volume allowance shall be made for each ganged portion required for mounting of the device or equipment. [314.16(B)(4)]

    E3905.12.2.5 Equipment grounding conductor fill.

    Where one or more equipment grounding conductors or equipment bonding jumpers enters a box, a single volume allowance in accordance with Table E3905.12.2.1 shall be made based on the largest equipment grounding conductor or equipment bonding jumper present in the box. [314.16(B)(5)]

    E3905.12.3 Conduit bodies.

    Conduit bodies enclosing 6 AWG conductors or smaller, other than short-radius conduit bodies, shall have a cross-sectional area not less than twice the cross-sectional area of the largest conduit or tubing to which they can be attached. The maximum number of conductors permitted shall be the maximum number permitted by Section E3904.6 for the conduit to which it is attached. [314.16(C)(1)]

    E3905.12.3.1 Splices, taps or devices.

    Only those conduit bodies that are durably and legibly marked by the manufacturer with their cubic inch capacity shall be permitted to contain splices, taps or devices. The maximum number of conductors shall be calculated using the same procedure for similar conductors in other than standard boxes. [314.16(C)(2)]

    E3905.12.3.2 Short-radius conduit bodies.

    Conduit bodies such as capped elbows and service-entrance elbows that enclose conductors 6 AWG or smaller and that are only intended to enable the installation of the raceway and the contained conductors, shall not contain splices, taps, or devices and shall be of sufficient size to provide free space for all conductors enclosed in the conduit body. [314.16(C)(3)]

    SECTIONE3906
    INSTALLATION OF BOXES,
    CONDUIT BODIES AND FITTINGS

    E3906.1 Conductors entering boxes, conduit bodies or fittings.

    Conductors entering boxes, conduit bodies or fittings shall be protected from abrasion. (314.17)

    E3906.1.1 Insulated fittings.

    Where raceways contain 4 AWG or larger insulated circuit conductors and these conductors enter a cabinet, box enclosure, or raceway, the conductors shall be protected by an identified fitting providing a smoothly rounded insulating surface, unless the conductors are separated from the fitting or raceway by identified insulating material securely fastened in place. [300.4(G)]

    Exception: Where threaded hubs or bosses that are an integral part of a cabinet, box enclosure, or raceway provide a smoothly rounded or flared entry for conductors. [300.4(G) Exception]

    Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway. The insulating fitting or insulating material shall have a temperature rating not less than the insulation temperature rating of the installed conductors. [330.4(G)]

    E3906.2 Openings.

    Openings through which conductors enter shall be closed in an approved manner. [314.17(A)]

    E3906.3 Metal boxes and conduit bodies.

    Where raceway or cable is installed with metal boxes, or conduit bodies, the raceway or cable shall be secured to such boxes and conduit bodies. [314.17(B)]

    E3906.4 Unused openings.

    Unused openings other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to that of the wall of the equipment. Metal plugs or plates used with nonmetallic boxes or conduit bodies shall be recessed at least 1/4 inch (6.4 mm) from the outer surface of the box or conduit body. [110.12(A)]

    E3906.5 In wall or ceiling.

    In walls or ceilings of concrete, tile or other noncombustible material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back from the finished surface more than 1/4 inch (6.4 mm). In walls and ceilings constructed of wood or other combustible material, boxes, plaster rings, extension rings and listed extenders shall be flush with the finished surface or project therefrom. (314.20)

    E3906.6 Noncombustible surfaces.

    Openings in noncombustible surfaces that accommodate boxes employing a flush-type cover or faceplate shall be made so that there are no gaps or open spaces greater than 1/8 inch (3.2 mm) around the edge of the box. (314.21)

    E3906.7 Surface extensions.

    Surface extensions shall be made by mounting and mechanically securing an extension ring over the box. (314.22)

    Exception: A surface extension shall be permitted to be made from the cover of a flush-mounted box where the cover is designed so it is unlikely to fall off, or be removed if its securing means becomes loose. The wiring method shall be flexible for an approved length that permits removal of the cover and provides access to the box interior and shall be arranged so that any bonding or grounding continuity is independent of the connection between the box and cover. (314.22 Exception)

    E3906.8 Supports.

    Boxes and enclosures shall be supported in accordance with one or more of the provisions in Sections E3906.8.1 through E3906.8.6. (314.23)

    E3906.8.1 Surface mounting.

    An enclosure mounted on a building or other surface shall be rigidly and securely fastened in place. If the surface does not provide rigid and secure support, additional support in accordance with other provisions of Section E3906.8 shall be provided. [314.23(A)]

    E3906.8.2 Structural mounting.

    An enclosure supported from a structural member or from grade shall be rigidly supported either directly, or by using a metal, polymeric or wood brace. [314.23(B)]

    E3906.8.2.1 Nails and screws.

    Nails and screws, where used as a fastening means, shall be attached by using brackets on the outside of the enclosure, or they shall pass through the interior within 1/4 inch (6.4 mm) of the back or ends of the enclosure. Screws shall not be permitted to pass through the box except where exposed threads in the box are protected by an approved means to avoid abrasion of conductor insulation. [314.23(B)(1)]

    E3906.8.2.2 Braces.

    Metal braces shall be protected against corrosion and formed from metal that is not less than 0.020 inch (0.508 mm) thick uncoated. Wood braces shall have a cross section not less than nominal 1 inch by 2 inches (25.4 mm by 51 mm). Wood braces in wet locations shall be treated for the conditions. Polymeric braces shall be identified as being suitable for the use. [314.23(B)(2)]

    E3906.8.3 Mounting in finished surfaces.

    An enclosure mounted in a finished surface shall be rigidly secured there to by clamps, anchors, or fittings identified for the application. [314.23(C)]

    E3906.8.4 Raceway supported enclosures without devices or fixtures.

    An enclosure that does not contain a device(s), other than splicing devices, or support a luminaire, lampholder or other equipment, and that is supported by entering raceways shall not exceed 100 cubic inches (1640 cm3) in size. The enclosure shall have threaded entries or identified hubs. The enclosure shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs. Each conduit shall be secured within 3 feet (914 mm) of the enclosure, or within 18 inches (457 mm) of the enclosure if all entries are on the same side of the enclosure. [314.23(E)]

    Exception: Rigid metal, intermediate metal, or rigid polyvinyl chloride nonmetallic conduit or electrical metallic tubing shall be permitted to support a conduit body of any size, provided that the conduit body is not larger in trade size than the largest trade size of the supporting conduit or electrical metallic tubing. [314.23(E) Exception]

    E3906.8.5 Raceway supported enclosures, with devices or luminaire.

    An enclosure that contains a device(s), other than splicing devices, or supports a luminaire, lampholder or other equipment and is supported by entering raceways shall not exceed 100 cubic inches (1640 cm3) in size. The enclosure shall have threaded entries or identified hubs. The enclosure shall be supported by two or more conduits threaded wrench-tight into the enclosure or hubs. Each conduit shall be secured within 18 inches (457 mm) of the enclosure. [314.23(F)]

    Exceptions:

    1. 1.Rigid metal or intermediate metal conduit shall be permitted to support a conduit body of any size, provided that the conduit bodies are not larger in trade size than the largest trade size of the supporting conduit. [314.23(F) Exception No. 1]

    2. 2.An unbroken length(s) of rigid or intermediate metal conduit shall be permitted to support a box used for luminaire or lampholder support, or to support a wiring enclosure that is an integral part of a luminaire and used in lieu of a box in accordance with Section E3905.1.1, where all of the following conditions are met:

      1. 2.1.The conduit is securely fastened at a point so that the length of conduit beyond the last point of conduit support does not exceed 3 feet (914 mm).

      2. 2.2.The unbroken conduit length before the last point of conduit support is 12 inches (305 mm) or greater, and that portion of the conduit is securely fastened at some point not less than 12 inches (305 mm) from its last point of support.

      3. 2.3.Where accessible to unqualified persons, the luminaire or lampholder, measured to its lowest point, is not less than 8 feet (2438 mm) above grade or standing area and at least 3 feet (914 mm) measured horizontally to the 8-foot (2438 mm) elevation from windows, doors, porches, fire escapes, or similar locations.

      4. 2.4.A luminaire supported by a single conduit does not exceed 12 inches (305 mm) in any direction from the point of conduit entry.

      5. 2.5.The weight supported by any single conduit does not exceed 20 pounds (9.1 kg).

      6. 2.6.At the luminaire or lampholder end, the conduit(s) is threaded wrenchtight into the box, conduit body, or integral wiring enclosure, or into hubs identified for the purpose. Where a box or conduit body is used for support, the luminaire shall be secured directly to the box or conduit body, or through a threaded conduit nipple not over 3 inches (76 mm) long. [314.23(F) Exception No. 2]

    E3906.8.6 Enclosures in concrete or masonry.

    An enclosure supported by embedment shall be identified as being suitably protected from corrosion and shall be securely embedded in concrete or masonry. [314.23(G)]

    E3906.9 Covers and canopies.

    Outlet boxes shall be effectively closed with a cover, faceplate or fixture canopy. Screws used for the purpose of attaching covers, or other equipment to the box shall be either machine screws matching the thread gauge or size that is integral to the box or shall be in accordance with the manufacturer’s instructions. (314.25)

    E3906.10 Covers and plates.

    Covers and plates shall be nonmetallic or metal. Metal covers and plates shall be grounded. [314.25(A)]

    E3906.11 Exposed combustible finish.

    Combustible wall or ceiling finish exposed between the edge of a fixture canopy or pan and the outlet box shall be covered with noncombustible material where required by Section E4004.2. [314.25(B)]

    SECTIONE3907
    CABINETS AND PANELBOARDS

    E3907.1 Switch and overcurrent device enclosures with splices, taps, and feed-through conductors.

    Where the wiring space of enclosures for switches or overcurrent devices contains conductors that are feeding through, spliced, or tapping off to other enclosures, switches, or overcurrent devices, all of the following conditions shall apply:

    1. 1.The total area of all conductors installed at any cross section of the wiring space shall not exceed 40 percent of the cross-sectional area of that space.

    2. 2.The total area of all conductors, splices, and taps installed at any cross section of the wiring space shall not exceed 75 percent of the cross-sectional area of that space.

    3. 3.A warning label shall be applied to the enclosure that identifies the closest disconnecting means for any feed-through conductors. (312.8)

    E3907.2 Damp and wet locations.

    In damp or wet locations, cabinets and panelboards of the surface type shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet, and shall be mounted to provide an air-space not less than 1/4 inch (6.4 mm) between the enclosure and the wall or other supporting surface. Cabinets installed in wet locations shall be weatherproof. For enclosures in wet locations, raceways and cables entering above the level of uninsulated live parts shall be installed with fittings listed for wet locations. (312.2)

    Exception: Nonmetallic enclosures installed on concrete, masonry, tile, or similar surfaces shall not be required to be installed with an air space between the enclosure and the wall or supporting surface. (312.2 Exception)

    E3907.3 Position in wall.

    In walls of concrete, tile or other noncombustible material, cabinets and panelboards shall be installed so that the front edge of the cabinet will not set back of the finished surface more than 1/4 inch (6.4 mm). In walls constructed of wood or other combustible material, cabinets shall be flush with the finished surface or shall project there-from. (312.3)

    E3907.4 Repairing noncombustible surfaces.

    Noncombustible surfaces that are broken or incomplete shall be repaired so that there will not be gaps or open spaces greater than 1/8 inch (3.2 mm) at the edge of the cabinet or cutout box employing a flush-type cover. (312.4)

    E3907.5 Unused openings.

    Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, and those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to that of the wall of the equipment. Metal plugs and plates used with nonmetallic cabinets shall be recessed at least 1/4 inch (6.4 mm) from the outer surface. Unused openings for circuit breakers and switches shall be closed using identified closures, or other approved means that provide protection substantially equivalent to the wall of the enclosure. (110.12(A)]

    E3907.6 Conductors entering cabinets.

    Conductors entering cabinets and panelboards shall be protected from abrasion and shall comply with Section E3906.1.1. (312.5)

    E3907.7 Openings to be closed.

    Openings through which conductors enter cabinets, panelboards and meter sockets shall be closed in an approved manner. [312.5(A)]

    E3907.8 Cables.

    Where cables are used, each cable shall be secured to the cabinet, panelboard, cutout box, or meter socket enclosure. [312.5(C)]

    Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more sections of rigid raceway not less than 18 inches (457 mm) nor more than 10 feet (3048 mm) in length, provided all the following conditions are met:

    1. 1.Each cable is fastened within 12 inches (305 mm), measured along the sheath, of the outer end of the raceway.

    2. 2.The raceway extends directly above the enclosure and does not penetrate a structural ceiling.

    3. 3.A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.

    4. 4.The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.

    5. 5.The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 1/4 inch (6.4 mm).

    6. 6.The raceway is fastened at its outer end and at other points in accordance with Section E3802.1.

    7. 7.The allowable cable fill shall not exceed that permitted by Table E3907.8. A multiconductor cable having two or more conductors shall be treated as a single conductor for calculating the percentage of conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on the major diameter of the ellipse as a circle diameter. [312.5(C) Exception]

    TABLE E3907.8 (Chapter 9, Table 1)

    PERCENT OF CROSS SECTION OF CONDUIT AND TUBING FOR CONDUCTORS

    NUMBER OF CONDUCTORSMAXIMUM PERCENT OF CONDUIT AND TUBING AREA FILLED BY CONDUCTORS
    153
    231
    Over 240

    E3907.9Wire-bending space within an enclosure containing a panelboard.

    Wire-bending space within an enclosure containing a panelboard shall comply with the requirements of Sections E3907.9.1 through E3907.9.3.

    E3907.9.1Top and bottom wire-bending space.

    The top and bottom wire-bending space for a panelboard enclosure shall be sized in accordance with Table E3907.9.1(1) based on the largest conductor entering or leaving the enclosure. [408.55 (A)]

    Exceptions:
    1. 1.For a panelboard rated at 225 amperes or less and designed to contain not more than 42 overcurrent devices, either the top or bottom wire-bending space shall be permitted to be sized in accordance with Table E3907.9.1(2). For the purposes of this exception, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively. [408.55(A) Exception No. 1]

    2. 2.For any panelboard, either the top or bottom wire-bending space shall be permitted to be sized in accordance with Table E3907.9.1(2) where the wire-bending space on at least one side is sized in accordance with Table E3907.9.1(1) based on the largest conductor to be terminated in any side wire-bending space. [408.55(A) Exception No. 2]

    3. 3. Where the panelboard is designed and constructed for wiring using only a single 90-degree bend for each conductor, including the grounded circuit conductor, and the wiring diagram indicates and specifies the method of wiring that must be used, the top and bottom wire-bending space shall be permitted to be sized in accordance with Table E3907.9.1(2). [408.55(A) Exception No. 3]

    4. 4.Where there are no conductors terminated in that space, either the top or the bottom wire-bending space, shall be permitted to be sized in accordance with Table E3907.9.1(2). [408.55(A) Exception No. 4]

    TABLE E3907.9.1(1) [Table 312.6(B)]

    MINIMUM WIRE-BENDING SPACE AT TERMINALS (see note 1)

    WIRE SIZE (AWG or kcmil)WIRES PER TERMINAL
    All other conductorsCompact stranded AA-8000 aluminum alloy conductors (see Note 3)One (see note 2)Two
    inchesmminchesmm
    14-1012-8Not specifiedNot specified
    8611/238.1
    64250.8
    42376.2
    31376.2
    21/031/288.9
    12/041/2114
    1/03/051/214051/2140
    2/04/061526152
    3/025061/2a165a61/2a165a
    4/03007b178b71/2c190c
    25035081/2d216d81/2d229d
    30040010c254c10d254d
    35050012c305c12c305c
    40060013c330c13c330c
    500700-75014c356c14c356c
    600800-90015c381c16c406c
    700100016c406c18c457c
    1. 1.Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector in a direction perpendicular to the enclosure wall.

    2. 2.For removable and lay-in wire terminals intended for only one wire, bending space shall be permitted to be reduced by the following number of millimeters (inches):

      1. a.1/2 inches (12.7 mm)

      2. b.1 inches (25.4 mm)

      3. c.11/2 inches (38.1 mm)

      4. d.2 inches (50.8 mm)

    3. 3.This column shall be permitted to determine the required wire-bending space for compact stranded aluminum conductors in sizes up to 1000 kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material.

    TABLE E3907.9.1(2) [Table 312.6(A)]

    MINIMUM WIRE-BENDING SPACE AT TERMINALS AND MINIMUM WIDTH OF WIRING GUTTERS (see note 1)

    WIRE SIZE (AWG or kcmil)WIRES PER TERMINAL
    OneTwo
    inchesmminchesmm
    14-10Not specifiedNot specified
    8-611/238.1
    4-3250.8
    221/263.5
    1276.2
    1/0-2/031/288.95127
    3/0-4/041026152
    25041/21146152
    300-35051278203
    400-50061528203
    600-700820310254
    1. 1.Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector in the direction that the wire leaves the terminal to the wall, barrier, or obstruction.

    E3907.9.2 Side wire-bending space.

    Side wire-bending space shall be in accordance with Table E3907.9.1(2) based on the largest conductor to be terminated in that space. [408.55(B)]

    E3907.9.3 Back wire-bending space.

    The distance between the center of the rear entry and the nearest termination for the entering conductors shall be not less than the distance given in Table E3907.9.1(1). Where a raceway or cable entry is in the wall of the enclosure, opposite a removable cover, the distance from that wall to the cover shall be permitted to comply with the distance required in Table E3907.9.1(2). [408.55 (C)]

    SECTIONE3908
    GROUNDING

    E3908.1 Metal enclosures.

    Metal enclosures of conductors, devices and equipment shall be connected to the equipment grounding conductor. (250.86)

    Exceptions:

    1. 1.Short sections of metal enclosures or raceways used to provide cable assemblies with support or protection against physical damage. (250.86 Exception No. 2)

    2. 2.A metal elbow that is installed in an underground installation of rigid nonmetallic conduit and is isolated from possible contact by a minimum cover of 18 inches (457 mm) to any part of the elbow or that is encased in not less than 2 inches (51 mm) of concrete. (250.86 Exception No. 3)

    E3908.2 Equipment fastened in place or connected by permanent wiring methods (fixed).

    Exposed, normally noncurrent-carrying metal parts of fixed equipment supplied by or enclosing conductors or components that are likely to become energized shall be connected to the equipment grounding conductor where any of the following conditions apply:

    1. 1.Where within 8 feet (2438 mm) vertically or 5 feet (1524 mm) horizontally of earth or grounded metal objects and subject to contact by persons;

    2. 2.Where located in a wet or damp location and not isolated; or

    3. 3.Where in electrical contact with metal. (250.110)

    E3908.3 Specific equipment fastened in place (fixed) or connected by permanent wiring methods.

    Exposed, normally noncurrent-carrying metal parts of the following equipment and enclosures shall be connected to an equipment grounding conductor:

    1. 1.Luminaires as provided in Chapter 40. [250.112(J)]

    2. 2.Motor-operated water pumps, including submersible types.Where a submersible pump is used in a metal well casing, the well casing shall be connected to the pump circuit equipment grounding conductor. [250.112(L)]

    E3908.4 Effective ground-fault current path.

    Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. Such circuit shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault might occur to the electrical supply source. [250.(A)(5)]

    E3908.5 Earth as a ground-fault current path.

    The earth shall not be considered as an effective ground-fault current path. [250.4(A)(5)]

    E3908.6 Load-side grounded conductor neutral.

    A grounded conductor shall not be connected to normally noncurrent-carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means. [250.24(A)(5)]

    E3908.7 Load-side equipment.

    A grounded circuit conductor shall not be used for grounding noncurrent-carrying metal parts of equipment on the load side of the service disconnecting means. [250.142(B)]

    E3908.8 Types of equipment grounding conductors.

    The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:

    1. 1.A copper, aluminum or copper-clad conductor.This conductor shall be solid or stranded; insulated, covered or bare; and in the form of a wire or a busbar of any shape. [250.118(1)]

    2. 2.Rigid metal conduit. [250.118(2)]

    3. 3.Intermediate metal conduit. [250.118(3)]

    4. 4.Electrical metallic tubing. [250.118(4)]

    5. 5.Armor of Type AC cable in accordance with Section E3908.4. [250.118(8)]

    6. 6.Type MC cable that provides an effective ground-fault current path in accordance with one or more of the following:

      1. 6.1.It contains an insulated or uninsulated equipment grounding conductor in compliance with Item 1 of this section.

      2. 6.2.The combined metallic sheath and uninsulated equipment grounding/bonding conductor of interlocked metal tape-type MC cable that is listed and identified as an equipment grounding conductor.

      3. 6.3.The metallic sheath or the combined metallic sheath and equipment grounding conductors of the smooth or corrugated tube-type MC cable that is listed and identified as an equipment grounding conductor. [250.118(10)]

    7. 7.Other electrically continuous metal raceways and auxiliary gutters. [250.118(13)]

    8. 8.Surface metal raceways listed for grounding. [250.118(14)]

    E3908.8.1 Flexible metal conduit.

    Flexible metal conduit shall be permitted as an equipment grounding conductor where all of the following conditions are met:

    1. 1.The conduit is terminated in listed fittings.

    2. 2.The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.

    3. 3.The combined length of flexible metal conduit and flexible metallic tubing and liquid-tight flexible metal conduit in the same ground return path does not exceed 6 feet (1829 mm).

    If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed. [250.118(5)]

    E3908.8.2 Liquid-tight flexible metal conduit.

    Liquid-tight flexible metal conduit shall be permitted as an equipment grounding conductor where all of the following conditions are met:

    1. 1.The conduit is terminated in listed fittings.

    2. 2.For trade sizes 3/8 through 1/2 (metric designator 12 through 16), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.

    3. 3.For trade sizes 3/4 through 11/4 (metric designator 21 through 35), the circuit conductors contained in the conduit are protected by overcurrent devices rated at not more than 60 amperes and there is no flexible metal conduit, flexible metallic tubing, or liquid-tight flexible metal conduit in trade sizes 3/8 inch or 1/2 inch (9.5 mm through 12.7 mm) in the ground fault current path.

    4. 4.The combined length of flexible metal conduit and flexible metallic tubing and liquid-tight flexible metal conduit in the same ground return path does not exceed 6 feet (1829 mm).

    If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed. [250.118(6)]

    E3908.8.3 Nonmetallic sheathed cable (Type NM).

    In addition to the insulated conductors, the cable shall have an insulated, covered, or bare equipment grounding conductor. Equipment grounding conductors shall be sized in accordance with Table E3908.12. (334.108)

    E3908.9 Equipment fastened in place or connected by permanent wiring methods.

    Noncurrent-carrying metal parts of equipment, raceways and other enclosures, where required to be grounded, shall be grounded by one of the following methods: (250.134)

    1. 1.By any of the equipment grounding conductors permitted by Sections E3908.8 through E3908.8.3. [250.134(A)]

    2. 2.By an equipment grounding conductor contained within the same raceway, cable or cord, or otherwise run with the circuit conductors. Equipment grounding conductors shall be identified in accordance with Section E3407.2. [250.134(B)]

    E3908.10 Methods of equipment grounding.

    Fixtures and equipment shall be considered grounded where mechanically connected to an equipment grounding conductor as specified in Sections E3908.8 through E3908.8.3. Wire type equipment grounding conductors shall be sized in accordance with Section E3908.12. (250 Part VII)

    E3908.11 Equipment grounding conductor installation.

    Where an equipment grounding conductor consists of a race-way, cable armor or cable sheath or where such conductor is a wire within a raceway or cable, it shall be installed in accordance with the provisions of this chapter and Chapters 34 and 38 using fittings for joints and terminations approved for installation with the type of raceway or cable used. All connections, joints and fittings shall be made tight using suitable tools. (250.120)

    E3908.12 Equipment grounding conductor size.

    Copper, aluminum and copper-clad aluminum equipment grounding conductors of the wire type shall be not smaller than shown in Table E3908.12, but they shall not be required to be larger than the circuit conductors supplying the equipment. Where a raceway or a cable armor or sheath is used as the equipment grounding conductor, as provided in Section E3908.8, it shall comply with Section E3908.4. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors shall be increased proportionally according to the circular mil area of the ungrounded conductors. [250.122(A) and (B)]

    TABLE E3908.12 (Table 250.122)

    EQUIPMENT GROUNDING CONDUCTOR SIZING

    RATING OR SETTING OF AUTOMATIC OVERCURRENT DEVICE IN CIRCUIT AHEAD OF EQUIPMENT, CONDUIT, ETC., NOT EXCEEDING THE FOLLOWING RATINGS (amperes)MINIMUM SIZE
    Copper wire No. (AWG)Aluminum or copper-clad aluminum wire No. (AWG)
    151412
    201210
    60108
    10086
    20064
    30042
    40031

    E3908.12.1 Multiple circuits.

    Where a single equipment grounding conductor is run with multiple circuits in the same raceway or cable, it shall be sized for the largest overcurrent device protecting conductors in the raceway or cable. [250.122(C)]

    E3908.13 Continuity and attachment of equipment grounding conductors to boxes.

    Where circuit conductors are spliced within a box or terminated on equipment within or supported by a box, any equipment grounding conductors associated with the circuit conductors shall be connected within the box or to the box with devices suitable for the use. Connections depending solely on solder shall not be used. Splices shall be made in accordance with Section E3406.10 except that insulation shall not be required. The arrangement of grounding connections shall be such that the disconnection or removal of a receptacle, luminaire or other device fed from the box will not interfere with or interrupt the grounding continuity. [250.146(A) and (C)]

    E3908.14 Connecting receptacle grounding terminal to box.

    An equipment bonding jumper, sized in accordance with Table E3908.12 based on the rating of the overcurrent device protecting the circuit conductors, shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box except where grounded in accordance with one of the following: (250.146)

    1. 1.Surface mounted box.Where the box is mounted on the surface, direct metal-to-metal contact between the device yoke and the box shall be permitted to ground the receptacle to the box. At least one of the insulating washers shall be removed from receptacles that do not have a contact yoke or device designed and listed to be used in conjunction with the supporting screws to establish the grounding circuit between the device yoke and flush-type boxes. This provision shall not apply to cover-mounted receptacles except where the box and cover combination are listed as providing satisfactory ground continuity between the box and the receptacle. A listed exposed work cover shall be considered to be the grounding and bonding means where the device is attached to the cover with at least two fasteners that are permanent, such as a rivet or have a thread locking or screw locking means and where the cover mounting holes are located on a flat non-raised portion of the cover. [250.146(A)]

    2. 2.Contact devices or yokes. Contact devices or yokes designed and listed for the purpose shall be permitted in conjunction with the supporting screws to establish equipment bonding between the device yoke and flush-type boxes. [250.146(B)]

    3. 3.Floor boxes.The receptacle is installed in a floor box designed for and listed as providing satisfactory ground continuity between the box and the device. [250.146(C)]

    E3908.15 Metal boxes.

    A connection shall be made between the one or more equipment grounding conductors and a metal box by means of a grounding screw that shall be used for no other purpose, equipment listed for grounding or by means of a listed grounding device. Where screws are used to connect grounding conductors or connection devices to boxes, such screws shall be one or more of the following: [250.148(C)]

    1. 1.Machine screw-type fasteners that engage not less than two threads.

    2. 2.Machine screw-type fasteners that are secured with a nut.

    3. 3.Thread-forming machine screws that engage not less than two threads in the enclosure. [250.8(5) and (6)]

    E3908.16 Nonmetallic boxes.

    One or more equipment grounding conductors brought into a nonmetallic outlet box shall be arranged to allow connection to fittings or devices installed in that box. [250.148(D)]

    E3908.17 Clean surfaces.

    Nonconductive coatings such as paint, lacquer and enamel on equipment to be grounded shall be removed from threads and other contact surfaces to ensure electrical continuity or the equipment shall be connected by means of fittings designed so as to make such removal unnecessary. (250.12)

    E3908.18 Bonding other enclosures.

    Metal raceways, cable armor, cable sheath, enclosures, frames, fittings and other metal noncurrent-carrying parts that serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be effectively bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel and similar coating shall be removed at threads, contact points and contact surfaces, or connections shall be made by means of fittings designed so as to make such removal unnecessary. [250.96(A)]

    E3908.19 Size of equipment bonding jumper on load side of an overcurrent device.

    The equipment bonding jumper on the load side of an overcurrent devices shall be sized, as a minimum, in accordance with Table E3908.12, but shall not be required to be larger than the circuit conductors supplying the equipment. An equipment bonding conductor shall be not smaller than No. 14 AWG.

    A single common continuous equipment bonding jumper shall be permitted to connect two or more raceways or cables where the bonding jumper is sized in accordance with Table E3908.12 for the largest overcurrent device supplying circuits therein. [250.102(D) and 250.122]

    E3908.20 Installation equipment bonding jumper.

    Bonding jumpers or conductors and equipment bonding jumpers shall be installed either inside or outside of a raceway or an enclosure in accordance with Sections E3908.20.1 and E3908.20.2. [250.102(E)]

    E3908.20.1 Inside raceway or enclosure.

    Where installed inside a raceway or enclosure, equipment bonding jumpers and bonding jumpers or conductors shall comply with the requirements of Sections E3407.2 and E3908.13. [250.102(E)(1)]

    E3908.20.2 Outside raceway or enclosure.

    Where installed outside of a raceway or enclosure, the length of the bonding jumper or conductor or equipment bonding jumper shall not exceed 6 feet (1829 mm) and shall be routed with the raceway or enclosure. [250.102(E)(2)]

    Equipment bonding jumpers and supply-side bonding jumpers installed for bonding grounding electrodes and installed at outdoor pole locations for the purpose of bonding or grounding isolated sections of metal raceways or elbows installed in exposed risers of metal conduit or other metal raceway, shall not be limited in length and shall not be required to be routed with a raceway or enclosure. [250.102(E)(2) Exception]

    E3908.20.3 Protection.

    Bonding jumpers or conductors and equipment bonding jumpers shall be installed in accordance with Section E3610.2. [250.102(E)(3)]

    SECTIONE3909
    FLEXIBLE CORDS

    E3909.1 Where permitted.

    Flexible cords shall be used only for the connection of appliances where the fastening means and mechanical connections of such appliances are designed to permit ready removal for maintenance, repair or frequent interchange and the appliance is listed for flexible cord connection. Flexible cords shall not be installed as a substitute for the fixed wiring of a structure; shall not be run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings or floors; shall not be concealed behind walls, floors, ceilings or located above suspended or dropped ceilings. (400.7 and 400.8)

    E3909.2 Loading and protection.

    The ampere load of flexible cords serving fixed appliances shall be in accordance with Table E3909.2. This table shall be used in conjunction with applicable end use product standards to ensure selection of the proper size and type. Where flexible cord is approved for and used with a specific listed appliance, it shall be considered to be protected where applied within the appliance listing requirements. [240.4, 240.5(A), 240.5(B)(1), 400.5, and 400.13]

    TABLE E3909.2 [Table 400.5(A)(1)]

    MAXIMUM AMPERE LOAD FOR FLEXIBLE CORDS

    CORD SIZE (AWG)CORD TYPES S, SE, SEO, SJ, SJE, SJEO, SJO, SJOO, SJT, SJTO, SJTOO, SO, SOO, SRD, SRDE, SRDT, ST, STD, SV, SVO, SVOO, SVTO, SVTOO
    Maximum ampere load
    Three current-carrying conductorsTwo current-carrying conductors
    18710
    161013
    141518
    122025

    E3909.3 Splices.

    Flexible cord shall be used only in continuous lengths without splices or taps. (400.9)

    E3909.4 Attachment plugs.

    Where used in accordance with Section E3909.1, each flexible cord shall be equipped with an attachment plug and shall be energized from a receptacle outlet. [400.7(B)]

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