Connecting A New Branch
To An Existing Electrical Circuit
Bruce W. Maki,
||This outlet will be the connection point for a
new electrical line.
I removed the outlet with a cordless drill-driver.
|Earlier I had removed this outlet to check how
many wires the box contained.
Because there was only one wire (the line that feeds this
outlet) and no other branches, I chose this outlet as a
point to begin a new branch.
||I removed the upper cable clamp. Many metal
electrical boxes have these built-in cable clamps. This type
uses a single screw to secure one or two cables.
|With the cable clamp removed, I removed the
knock-out. This was quite difficult, as I could not get a
screwdriver in the optimum position. But I finally succeeded.
||Normally it is easier to run the new cable by
starting at the smaller hole and trying to grab it at the
larger hole (the opening for the old-work box just three
feet higher up the wall).
But in this case, I kept running into some obstruction. It
seemed there was a piece of blocking in the wall
cavity, standing on edge as to partially block the cavity.
|So I tried the other way... by inserting the
cable into the old work box hole and trying to hit the tiny hole
in the metal box.
This method is a long shot, and I figured it would take a
while. But the cable end was visible, resting on the top of
the box, and all I had to do was direct it into the hole
with a screwdriver (working in the gap above the box).
Getting the cable clamp back into the box took forever.
||With the new cable extending out of the box by
about 6 inches, I stripped back the cable jacket, and connected
the two ground wires with this special wire nut.
These green wire nuts are for ground wires and have a hole
in the end, so one wire can extend through and connect to
the device's ground screw.
|I stripped back the insulation on the white
(neutral) wire and connected it to the empty silver
screw on the receptacle.
||I connected the black (hot) wire to the
empty gold screw on the receptacle.
About These Terms:
The neutral wire has the same electrical potential as the
earth. Theoretically, when everything is working right, you should
not get a shock from touching a bare neutral wire (but don't try
this!) because at the breaker panel the neutral and ground wires are
The hot wire is so named because there is high electrical
potential (i.e. voltage) between hot and neutral, and also the same
potential between hot and ground.
If a neutral wire became open (such as if a wire nut fell off
somewhere in the middle of a sequence of connections) then parts of
that neutral line could actually be hot, but no devices connected to
that part of the circuit would function. Does this sound
baffling? Electricity can be sort of complicated, until you
understand the fundamentals. Read our
Science Of Electricity section.
|Since this receptacle is in a metal box (and
because I know that elsewhere in the circuit there is no ground
wire) I wrapped it in electrical tape. This also provides an
added layer of protection from shock when the cover plate is
removed, such as during painting.
||I re-installed the outlet and its cover plate.
After the rest of the components were connected, I turned the
power on and verified that everything worked.
Back To Top
- Cordless Drill/Driver
- Flat Blade Screwdriver
- Needle-nose Pliers
- Wire Strippers
- Non-Metallic Cable
- Wire Nuts
- Electrical Tape