Page 771 - 2018_IRC

POWER AND LIGHTING DISTRIBUTION

E3905.12.2 Box fill calculations. The volumes in Section volume allowance in accordance with Table
E3905.12.2.1 through Section E3905.12.2.5, as applicable, E3905.12.2.1 shall be made for each type of fitting based
shall be added together. No allowance shall be required for on the largest conductor present in the box.
small fittings such as locknuts and bushings. Each space [314.16(B)(3)]
within a box installed with a barrier shall be calculated E3905.12.2.4 Device or equipment fill. For each yoke
separately. [314.16(B)] or strap containing one or more devices or equipment, a
E3905.12.2.1 Conductor fill. Each conductor that double volume allowance in accordance with Table
originates outside the box and terminates or is spliced E3905.12.2.1 shall be made for each yoke or strap
within the box shall be counted once, and each conduc- based on the largest conductor connected to a device(s)
tor that passes through the box without splice or termi- or equipment supported by that yoke or strap. For a
nation shall be counted once. Each loop or coil of device or utilization equipment that is wider than a sin-
unbroken conductor having a length equal to or greater gle 2-inch (51 mm) device box as described in Table
than twice that required for free conductors by Section E3905.12.1, a double volume allowance shall be made
E3406.11.3, shall be counted twice. The conductor fill, for each ganged portion required for mounting of the
in cubic inches, shall be computed using Table device or equipment. [314.16(B)(4)]
E3905.12.2.1. A conductor, no part of which leaves the E3905.12.2.5 Equipment grounding conductor fill.
box, shall not be counted. [314.16(B)(1)] Where one or more equipment grounding conductors or
Exception: An equipment grounding conductor or equipment bonding jumpers enters a box, a single vol-
not more than four fixture wires smaller than No. 14, ume allowance in accordance with Table E3905.12.2.1
or both, shall be permitted to be omitted from the shall be made based on the largest equipment ground-
calculations where such conductors enter a box from ing conductor or equipment bonding jumper present in
a domed fixture or similar canopy and terminate the box. [314.16(B)(5)]
within that box. [314.16(B)(1) Exception] E3905.12.3 Conduit bodies. Conduit bodies enclosing 6
TABLE E3905.12.2.1 [Table 314.16(B)] AWG conductors or smaller, other than short-radius con-
VOLUME ALLOWANCE REQUIRED PER CONDUCTOR duit bodies, shall have a cross-sectional area not less than
FREE SPACE WITHIN BOX twice the cross-sectional area of the largest conduit or tub-
SIZE OF CONDUCTOR FOR EACH CONDUCTOR ing to which they can be attached. The maximum number
(cubic inches) of conductors permitted shall be the maximum number
18 AWG 1.50 permitted by Section E3904.6 for the conduit to which it is
16 AWG 1.75 attached. [314.16(C)(1)]
14 AWG 2.00 E3905.12.3.1 Splices, taps or devices. Only those con-
12 AWG 2.25 duit bodies that are durably and legibly marked by the
manufacturer with their cubic inch capacity shall be
10 AWG 2.50
permitted to contain splices, taps or devices. The maxi-
8 AWG 3.00 mum number of conductors shall be calculated using
6 AWG 5.00 the same procedure for similar conductors in other than
standard boxes. [314.16(C)(2)]
For SI: 1 cubic inch = 16.4 cm . 3
E3905.12.2.2 Clamp fill. Where one or more internal E3905.12.3.2 Short-radius conduit bodies. Conduit
cable clamps, whether factory or field supplied, are bodies such as capped elbows and service-entrance
present in the box, a single volume allowance in accor- elbows that enclose conductors 6 AWG or smaller and
dance with Table E3905.12.2.1 shall be made based on that are only intended to enable the installation of the
the largest conductor present in the box. An allowance raceway and the contained conductors, shall not contain
shall not be required for a cable connector having its splices, taps, or devices and shall be of sufficient size to
clamping mechanism outside of the box. provide free space for all conductors enclosed in the
conduit body. [314.16(C)(3)]
A clamp assembly that incorporates a cable termina-
tion for the cable conductors shall be listed and marked
for use with specific nonmetallic boxes. Conductors SECTION E3906
that originate within the clamp assembly shall be INSTALLATION OF BOXES,
included in conductor fill calculations provided in Sec- CONDUIT BODIES AND FITTINGS
tion E3905.12.2.1 as though they entered from outside E3906.1 Conductors entering boxes, conduit bodies or fit-
of the box. The clamp assembly shall not require a fill tings. Conductors entering boxes, conduit bodies or fittings
allowance, but, the volume of the portion of the assem- shall be protected from abrasion. (314.17)
bly that remains within the box after installation shall
be excluded from the box volume as marked in accor- E3906.1.1 Insulated fittings. Where raceways contain 4
dance with Section E3905.12.1.2. [314.16(B)(2)] AWG or larger insulated circuit conductors and these con-
ductors enter a cabinet, box enclosure, or raceway, the
E3905.12.2.3 Support fittings fill. Where one or more
fixture studs or hickeys are present in the box, a single conductors shall be protected by an identified fitting pro-
viding a smoothly rounded insulating surface, unless the

746 2018 INTERNATIONAL RESIDENTIAL CODE ®
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