Installing an electrical socket in an existing wall

My friend Melissa wanted to have an electrical socket installed to be hidden behind her new wall mounted LCD TV, and managed to persuade me to do it.

The socket needed to be mounted just 1 meter above an existing socket, so the installation didn't involve much of a challenge fishing wires through walls. So I knew the whole thing could be done within a relatively deterministic amount of time.

I started by making a small hole in the drywall roughly where I wanted the socket to go. I started with a small hole, so I could make sure there was hollow space where I wanted the socket to go, and also to feel for the exact location of the stud before I cut it much bigger.

Even though I was using a rework socket that can be mounted directly in drywall, it's always best to put a new socket next to a stud, so that it can be screwed directly into the wood for good measure.

Shown is the outline I drew from the template that came with the socket, though I didn't draw the part of the outline on the left - that's where I attach it straight to the stud.

Rework sockets have flip out wings on the ends for holding the socket straight in drywall. The wing flips out when the screw it's attached to is turned clockwise for tightening. This causes the socket to clamp the drywall between the flip out wing, and the larger flanges on either end of the electrical box. It's a neat system, although I am always skeptical how well the socket would hold if mounted just to the edges of the drywall like that.

The flip-out wing

Wing position while inserting

Wing position once installed

It's best not to try to follow all the corners of the outline when initially cutting the hole. In fact, I usually like to go a little smaller than the outline. It's easy enough to enlarge the hole afterwards, but impossible to make it smaller. And the template is nearly the size of the cover plate (see first image of the article), so there's little room for error.

A utility knife will do the job just fine for drywall. First cut firmly along the lines, then keep doing this until you get fairly deeply, next use a saw-like action with the knife to cut all the way though.

If your house uses plaster walls (1950's or earlier), its not as easy to cut a nice hole for a socket, you might want to read about installing in plaster walls.

A fairly clean cut, the initial rectangle is removed.

Next it's time to fit the socket, expanding the hole to allow for all the bumps and protrusions on the socket. Also note that I removed the wing on the left side of the socket, and bent the metal flat, so that I could screw that side directly to the stud.

And checking the fit in the final sized hole. Note how the hole has been expanded on the right side to make room for the flip out wing. The hole is still smaller than the one the template would have suggested.

Wiring to an existing socket

Next it was time to tap into the existing socket, which was just a meter below the new socket. Don't forget to take out the breaker before you do this, or you will get a rather jolting reminder to do so when you grab the socket by its terminals (speaking from experience, although not on this occasion)

Removing this socket, we can see that it is part of a chain of socket, as it is not a split socket but has two cables hooked up to it, one feeding power, the other going on to the next socket. They used the socket to connect the wires together - this may or may not be conforming with present electrical codes in some jurisdictions. I think primarily because if somebody does work, one can mess up the circuits down the line. Especially if one interrupts neutral (white) while leaving hot (black) connected.

Of greater concern to me was that both wires fed in from the top, so those holes in the metal box were already full. I could have tried pulling a second wire into one of the holes, but that is kind of ugly, and probably also a violation of electrical codes.

So I decided to try to pass the wire behind the socket, catch it with a pair of surgical forceps through the hole on the bottom and pull it in. Surgical forceps are good for this sort of job, because they are narrow, with the hinge fairly close to the front, so you can reach through a small hole and still open them.

You can usually find used surgical forceps at surplus stores for a few dollars each.

To make it easier to catch the wire, I stripped the outer insulation off the end of it, so that I could pull one conductor at a time into the hole. In retrospect, it would have been easier if I had stripped the inner insulation off the very end of the wires as well. The forceps were barely strong enough to get one wire into the hole at a time.

Once I had the wires in, I used a pair of needle-nose pliers to pull them further into the socket far enough so that the main insulation sheath was pulled into the socket.

The next step was to put the strain relief back on the bottom of the socket, though I neglected to take a photo of that step.

To be on the safe side, I decided to make the connection of the neutral wires all with one wire nut. With the feed wire, one wire going off to the next socket, one wire to the new socket, and a short wire to the existing socket, it was four wires to connect together.

For four or more wires, the screw terminal wire nuts work pretty good, as long as you tighten them enough. It's best to hold the brass sleeve in a pair of pliers while tightening the set screw, just to get enough torque. Next, screw the plastic cap back on it.

For the hot (not neutral) lead, I left it going through the socket, so I only had three wires to contend with, and used a regular wire nut.

The key to having these work well is to twist the wires together with a pair of square nosed pliers before twisting the wire nut on.

With the wire connected into the bottom socket installed and secured, it was time to feed the wire through the rework socket, and then stick the rework socket back in the hole and screw it in.

A great advantage of the rework sockets is the way they wires feed into them at the back, which allows you to insert the socket into the hole in the wall with the wires already in it.

With the funny clamping wing removed from the left side, I was able to screw the socket directly into the stud. I did have to drill a larger hole in that side of the box to get even a drywall screw through.

And with the wiring on the socket all done.

There is a bit of an incompatibility between the rework sockets, and the "decora" style switch and socket plate covers. The screws for these tend to hit the flanges of the rework sockets, so it helps to bastardize the rework sockets a little to make room for the screws. Here's me opening the space a little with a screwdriver. Another approach is to crimp the flange a bit narrower where the screw goes with a pair of wire cutters. It's all a rather inexact business.

And finally, the socket, with the wall bracket mounted back on the wall. Time to turn the electricity back on and mount the TV on the wall.

And with the TV mounted on the wall. Melissa likes the juxtaposition of the fancy new HDTV and the rabbit ears. She's planning on mounting a shelf for the DVD player just below the TV. With the socket behind the TV, there will be no dangling power cords.

And the socket, as seen from behind the TV. Maybe we should have mounted it a centimeter lower to give the plug a little bit more room. We wound the cord around the bracket to get it out of sight.