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Section E3905 Boxes, Conduit Bodies and Fittings
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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)
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)]
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)]
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)]
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)]
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.
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)]
Metal boxes shall be grounded. (314.4)
Nonmetallic boxes shall be used only with cabled wiring methods with entirely nonmetallic sheaths, flexible cords and nonmetallic raceways. (314.3)
Exceptions:
- 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)
- 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)
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)]
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]
Nonmetallic boxes shall be suitable for the lowest temperature-rated conductor entering the box. [314.17(C)]
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)]
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)]
- 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)]
- 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)]
- 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)]
- 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)]
- 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)]
Exception: Utilization equipment that is listed to be installed with specified boxes.
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)
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)]
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]
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 for not less than the weight to be supported. The interior of the box shall be marked by the manufacturer to indicate the maximum weight that the box is permitted to support. [314.27(A)(2)]
Where outlet boxes for receptacles are installed in the floor, such boxes shall be listed specifically for that application. [314.27(B)]
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)]
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]
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)
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, not smaller than 1/8 inch (3 mm) 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)
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)
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. Where a box is provided with one or more securely installed barriers, the volume shall be apportioned to each of the resulting spaces. Each barrier, if not marked with its volume, shall be considered to take up to 0.5 cubic inch (8.2 cm3) if metal, and 1.0 cubic inch (16.4 cm3) if nonmetallic. [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 Awg | 16 Awg | 14 Awg | 12 Awg | 10 Awg | 8 Awg | 6 Awg | ||
| 4 × 11/4 round or octagonal | 12.5 | 8 | 7 | 6 | 5 | 5 | 4 | 2 |
| 4 × 11/2 round or octagonal | 15.5 | 10 | 8 | 7 | 6 | 6 | 5 | 3 |
| 4 × 21/8 round or octagonal | 21.5 | 14 | 12 | 10 | 9 | 8 | 7 | 4 |
| 4 × 11/4 square | 18.0 | 12 | 10 | 9 | 8 | 7 | 6 | 3 |
| 4 × 11/2 square | 21.0 | 14 | 12 | 10 | 9 | 8 | 7 | 4 |
| 4 × 21/8 square | 30.3 | 20 | 17 | 15 | 13 | 12 | 10 | 6 |
| 411/16 × 11/4 square | 25.5 | 17 | 14 | 12 | 11 | 10 | 8 | 5 |
| 411/16 × 11/2 square | 29.5 | 19 | 16 | 14 | 13 | 11 | 9 | 5 |
| 411/16 × 21/8 square | 42.0 | 28 | 24 | 21 | 18 | 16 | 14 | 8 |
| 3 × 2 × 11/2 device | 7.5 | 5 | 4 | 3 | 3 | 3 | 2 | 1 |
| 3 × 2 × 2 device | 10.0 | 6 | 5 | 5 | 4 | 4 | 3 | 2 |
| 3 × 2 × 21/4 device | 10.5 | 7 | 6 | 5 | 4 | 4 | 3 | 2 |
| 3 × 2 × 21/2 device | 12.5 | 8 | 7 | 6 | 5 | 5 | 4 | 2 |
| 3 × 2 × 23/4 device | 14.0 | 9 | 8 | 7 | 6 | 5 | 4 | 2 |
| 3 × 2 × 31/2 device | 18.0 | 12 | 10 | 9 | 8 | 7 | 6 | 3 |
| 4 × 21/8 × 11/2 device | 10.3 | 6 | 5 | 5 | 4 | 4 | 3 | 2 |
| 4 × 21/8 × 17/8 device | 13.0 | 8 | 7 | 6 | 5 | 5 | 4 | 2 |
| 4 × 21/8 × 21/8 device | 14.5 | 9 | 8 | 7 | 6 | 5 | 4 | 2 |
| 33/4 × 2 × 21/2 masonry box/gang | 14.0 | 9 | 8 | 7 | 6 | 5 | 4 | 2 |
| 33/4 × 2 × 31/2 masonry box/gang | 21.0 | 14 | 12 | 10 | 9 | 8 | 7 | 4 |
For SI: 1 inch = 25.4 mm, 1 cubic inch = 16.4 cm3.
- Where volume allowances are not required by Sections E3905.12.2.2 through E3905.12.2.5.
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)]
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