Electrical
Advice From an Experienced
Professional
Dear
Mr. Electrician: I want to install
an outlet on a dedicated circuit for
my window air conditioner. I've
got it figured out how to run the 12/2
NM-B cable from the circuit breaker
electrical panel in the basement up
through the wall under the living room
window. How do I install an electrical
receptacle box in the wall that will
contain the wire and support the
receptacle? Click
here for answer.Photos
below
The
hole below was made using a drywall
saw. The metal box was held
against the wall and a pencil line was
traced onto the surface. Note
the notches on the upper right and
lower left corners. They are to
allow for the protruding screws on
each side that all metal switch boxes
of this type have.
The
photo below shows that the
12/2 type NM-B wire is brought into the metal box and
clamped. The ground wire is
attached to the box using a separate
10/32 machine screw.
In
the photo below, the
longer end of the Madison Bar is
inserted first along side of the metal
box.
With
one Madison Bar pinched tightly in the
photo below, the
other side of the metal electrical box
protrudes slightly from the wall.
After
inserting the second Madison Bar as
depicted in the photo below, the
edge of the metal electrical box needs
to be pushed hard against the wall
as the Madison Bar is pinched
over. This ensures that the box
will be held in place tightly.
The
box in the photo below is held firmly in place by the
Madison Bars. It should not be
loose. Note how the screw hole
tabs on the box are set back into the
wall slightly.
The
wires below are folded and the GFI receptacle
is pushed into the box
Below
is the
finished GFI receptacle installation
using Madison Bars to support the
box. I usually prefer to install
the box next to a wall stud so that a
wood or sheet metal screw can be screwed
through a hole in the box directly into
the wood stud in addition to the Madison
Bars. That makes the box extremely
secure. However in this case the
customer wanted the receptacle in this
exact location so the mounting is
entirely dependent on the Madison
Bars. Fortunately the drywall is
in very good condition here.
Click
here for more instructions on
installing an electrical box in a wall.
