Selection Guide
Free space within box for each conductor
Size of conductor (AWG) (cm
) (in.
)
—
Metallic boxes — Fire resistance rating
Wall Penetrations
Listed single- and double-gang metallic outlet and
switch boxes and octagon ceiling boxes with
metallic or non-metallic cover plates may be
used in bearing and non-bearing wood stud and
steel stud walls with ratings not exceeding 2
hours. These walls shall have gypsum wallboard
facings similar to those shown in Design Nos.
U301, U411, and U425. 4 in. square boxes may be
used in 2 hr. fire rated ceilings.
The surface area of individual metallic outlet or
The aggregate surface area of the boxes shall not
exceed 100 sq. inches per 100 sq. ft. of wall.
Boxes located on opposite sides of walls or
partitions shall be separated by a horizontal
distance of 24 inches.
The metallic outlet or switch boxes shall be
securely fastened to the studs and the opening in
the wallboard facing shall be cut so that the
clearance between the box and the wallboard does
not exceed
1
8 in.
9
Reprinted with permission from National Fire Protection Association NFPA70-2011.
on the referenced subject which is represented only by the standard in its entirety.
Canadian Standards Association File Number: LR 12798
Products designed to meet Federal Specification Number: A-A5924 (formerly W-J-800).
Verification of file numbers and compliance with federal specifications for individual items available upon request.
AISI C-1055, heat treated to R. 35 zinc plated .0005 thick.
OVERVIEW - NEC® REFERENCE