Chapter 3 Wiring Methods and Materials

ARTICLE 312 -
CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES
312.10
Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters
Wires per Terminal
1 2 3 4 5
Wire Size (AWG or
kcrnil) mrn in. mrn in. mrn in. mm in. mrn in.
14-10 Not specified
8-6 38.1 1 1 /2
4-3 50.8 2
2 63.5 2'/2
1 76.2 3
110-2/0 88.9 3 1 /2 127 5 178 7
3/0-4/0 102 4 152 6 203 8
250 114 4 1 /2 152 6 203 8 254 10
300-350 127 5 203 8 254 10 305 12
400-500 152 6 203 8 254 10 305 12 356 14
600-700 203 8 254 10 305 12 356 14 406 16
750-900 203 8 305 12 356 14 406 16 457 18
1000-1250 254 10
1500-2000 305 12
Note: 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, bamer, or obstruction.
enter or leave the enclosure through the wall opposite its
terminal.
(2) Conductors Entering or Leaving Opposite Wall.
Table 312.6(B) shall apply where the conductor does
enter or leave the enclosure through the wall opposite its
terminal.
Exception No.1: Where the distance between the wall and
its terminal is in accordance with Table 312.6(A), a conductor
shall be permitted to enter or leave an enclosure
through the wall opposite its terminal, provided the conductor
enters or leaves the enclosure where the gutter joins
an adjacent gutter that has a width that conforms to Table
312.6(B) for the conductor.
Exception No.2: A conductor not larger than 350 kcmil
shall be permitted to enter or leave an enclosure containing
only a meter socket(s) through the wall opposite its terminal,
provided the distance between the terminal and the
opposite wall is not less than that specified in Table
312.6(A) and the terminal is a lay-in type, where the terminal
is either of the following:
(a) Directed toward the opening in the enclosure and
within a 45 degree angle of directly facing the enclosure
wall
(b) Directly facing the enclosure wall and offset not
greater than 50 percent of the bending space specified in
Table 312.6(A)
FPN: Offset is the distance measured along the enclosure
wall from the axis of the centerline of the terminal to a line
passing through the center of the opening in the enclosure.
(C) Conductors 4 AWG or Larger. Installation shall comply
with 300.4(G).
312.7 Space in Enclosures. Cabinets and cutout boxes
shall have sufficient space to accommodate all conductors
installed in them without crowding.
312.8 Enclosures for Switches or Overcurrent Devices.
Enclosures for switches or overcurrent devices shall not be
used as junction boxes, auxiliary gutters, or raceways for conductors
feeding through or tapping off to other switches or
overcurrent devices, unless adequate space for this purpose is
provided. The conductors shall not fill the wiring space at any
cross section to more than 40 percent of the cross-sectional
area of the space, and the conductors, splices, and taps shall
not fill the wiring space at any cross section to more than
75 percent of the cross-sectional area of that space.
312.9 Side or Back Wiring Spaces or Gutters. Cabinets
and cutout boxes shall be provided with back-wiring
spaces, gutters, or wiring compartments as required by
312.11(C) and (D).
II. Construction Specifications
312.10 Material. Cabinets, cutout boxes, and meter socket
enclosures shall comply with 312.1O(A) through (C).
(A) Metal Cabinets and Cutout Boxes. Metal enclosures
within the scope of this article shall be protected both inside
and outside against corrosion.
FPN: For information on protection against corrosion, see
300.6.
(B) Strength. The design and construction of enclosures
within the scope of this article shall be such as to secure
2008 Edition NATIONAL ELECTRICAL CODE
70-165