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Box Mounting on Metal Framing | Up
Construction Electrician Basic - Electricity handbook for electricians | Next
Box Mounting in Existing Structures |
Figure 5-13.—Box mounting on metal doorframe.
quick, simple method of installing a box on the
doorframe. This anchor allows the box to be adjusted in
all directions; that is, toward or away from the frame,
the depth from the outside wall surface, and up or down
as needed. The nut on the bolt shown in the figure holds
the bracket to the anchor and must be loose while the
anchor is installed. The anchor itself consists of a
flathead bolt with a screwdriver slot and a threaded
channel. The channel comes in two sizes; one for
narrow doorframes not over 4 inches wide and a second
for doorframes up to 7 inches wide. The anchor is set in
place by inserting it in the frame channel with the
flathead of the bolt toward the doorstop channel and the
threaded channel under the lips of the doorframe. The
anchor is locked in place by inserting a screwdriver in
the slot of the bolt and turning it clockwise until tight.
As you can see in the figure, the bracket is adjustable
and is held in position by the tightened nut on the bolt.
The box is adjustable toward or away from the
doorframe and is attached to the bracket with two
machine bolts and nuts.
Metal spring clips provide a quick and easy way of
mounting boxes onto metal studs. The same clip will
work on studs of more than one design and size, such as
1 5/8- to 3 5/8-inch C channel studs and the truss type of
studs. They are designed to mount square boxes with
cover plates and to permit device boxes to be flush-
mounted with various thicknesses of wall surfacing. A
metal spring clip is shown at the left in figure 5-14. To
mount a box, tap the clip over the open edge of the box.
Then tip the box so the upper prong slips behind the face
of the stud, as you can see at the right in figure 5-14.
Press the lower prong back with your thumb until it slips
Figure 5-14.—Box mounting on metal stud with spring clip.
behind the stud face and locks the box in place. The box
can be moved easily up or down on the stud by releasing
the spring tension. Boxes can also be attached to metal
framing members with sheet metal screws or machine
bolts and nuts.
Box Mounting Between Framing
At times, boxes must be mounted between the
building or wall supports instead of directly on them.
This positioning is particularly true of ceiling lights
where the joists do not coincide with the spot at which
the light is to be placed. In such cases, boxes must be
mounted on a separate support attached to the structure.
These supports may be purchased in the form of bar
hangers or metal straps, or they may be constructed
from metal straps or wooden strips. Figure 5-15 shows
Figure 5-15.—Box supports.
5-9
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