How to Hide a Wall Wart Transformer

In the last 20 years our homes have become inundated with "wall warts," the small to not-so-small electric transformers for everything from powering our computer printers to recharging our iPads. Behind our TV, there are at least four of them attached to devices such as the cable box or my wireless stereo headphones. Because some of these ubiquitous devices are inside a cabinet or behind the appliance they power, they are out of sight and out of mind. However, many of these byproducts of the electronic age create a blight on the visual harmony of our home. A case in point:

In our kitchen, the hub of activity in our house, the cordless phone system’s mother ship was mounted on a wall over a countertop (see photo). However, like many modern phones, it required a fairly large transformer to power it. The good news was there was a duplex electric outlet right next to the phone; the bad news was that this wall wart was unsightly. The situation begged for a hidden remote electric outlet. So I decided to make an extension to the wall mounted duplex outlet next to the phone by dropping below the countertop, installing the new outlet inside the cabinet below and, most importantly, placing it out of sight.

Here is how to do that...

Turn off the electric power to this circuit at your circuit breaker box. Verify with a circuit tester, a voltage detector, or a voltmeter that the circuit is offline. Any of these 3 tools can tell you if the power is shut off. None of them is foolproof. I usually check a nearby circuit that I know is hot with the voltage detector to prove it is working and then check the duplex outlet I will be working on. To be on the safe side I will also plug in the circuit tester. My least favorite tool for this job is the voltmeter. Too many times I have seen the probe not make contact with the element in the socket until I moved it around a bit.

Before starting anything, put on some eye protection even if it is just your regular glasses. The wires and the tools you will deal with can injure your eyes when you least expect it.

Take the plastic cover off of the duplex socket, remove the attachment screws, and pull out the socket itself. I often wear some work gloves when doing this because a lot of the edges of these sockets and the wire ends are sharp. Usually the wires in an older outlet box are stiff and some effort is required to pull the socket out far enough to get to the lug screws. You will now be able to look inside the outlet box that housed the socket.

Unless there is an unused opening in the bottom of this outlet box already, you will need to remove a knock-out slug in the bottom of a metal box so that you can pass a piece of Romex electrical cable through that opening. These pre-punched disks push inward to create additional openings in electric boxes. In a new construction situation an electrician would knock out the disk with a screwdriver and the heal of his hand from the outside. But you will be approaching the box from the inside. In this situation it is usually easier to use a small blade screwdriver and get it into the pre-punched slot and pry up on the disk until the slot gets bigger. Then you can insert a bigger screwdriver to push it up enough until you can grasp the K-O slug with some needle nose pliers and bend it up and down until it breaks off.

Probe downward through the new opening in the outlet box with a wire fish (a piece of semi-rigid wire rod with a small loop in one end) into the inner wall space to make sure there is not a noggin, a horizontal 2 X 4 cross member, inside the wall between the studs. Although this would not be a show-stopper, it would definitely require a decision on your part. At this point, you would either have to figure out how to drill at least a 1/2" hole through the noggin or look elsewhere for another location for the wall wart, such as in a cabinet above the counter top. The latter choice would usually be the better option. The process would be virtually identical for putting the new hidden outlet in the cabinet below the counter top except you would run the wiring upward through the wall instead of down.

It is likely that this outlet box in the wall is attached to a stud. Be mindful of this since the hole in the sheetrock you will make below must be on the same side of the stud as this box. Note- in the photo above the fish is protruding from the hole in the bottom of the outlet box.

Figure out where you want the duplex outlet to be in the cabinet below. Normally it should be located directly below the outlet you are connecting to. On the rear wall of the cabinet, draw the outline or the footprint of the old work electric box. Place masking tape on the outsides of the lines to help prevent the sheetrock from splitting or crumbling when you are sawing the opening.

Drill a one-inch hole through the sheetrock or wood panel in one corner of that outline. Use a hole saw or jigsaw to cut a rectangular opening in the rear wall. Remember that there may be wires inside the wall into which you are drilling/cutting and you don't want to damage it. The sheetrock in the back of my cabinet was old and very friable and did not make sharp edges.

Insert a ruler into the new opening to measure how much room there is between the inside surface of the sheetrock and the outer wall. That is to say, will the wall space accommodate a full depth old work (push-in type) outlet box or will you need a shallow depth version? Note- The term old work means the type of electric box that is added to an existing house and is generally pushed into to newly created opening in a wall.

Using the fish, go down from the opening in the bottom of the outlet box and feed it downward through the wall space until it appears in the opening that you have just made in the cabinet below. Pull the end of the fish slightly out of that hole (see photo).

Estimate how much 12-gauge Romex wire you will need to connect the top and bottom boxes. Then cut at least a foot more to give yourself some some extra wire for a service loop in the back of each box, i.e., some slack in the Romex to allow you to easily connect the wiring to the sockets and to permit trouble-free access if you have to work on these sockets again in the future.

1. Push one end of the Romex cable through an opening in the top of the old work outlet box.

2. Strip back approx 6 inches of the outer insulation covering on both ends of the Romex and then strip the insulation off the black and white wires on both ends sufficient to make C shaped bends in the wire. This will render it easier to attach these wires to the sockets (see photo).

3. On the end of the Romex you pushed into the outlet box, attach the three wires (hot, common, and ground) to the appropriate lugs on the new duplex socket. It is much easier to do this out on a workbench or a countertop rather than trying to work up inside the cabinet.

1. Tape the loose end of the Romex to the small loop in the end of the fish that is protruding from the hole in the wall.

2. From the wall opening above the countertop, pull the fish wire up through the wall and bring the loose end of the Romex out of the hole in the bottom of the outlet box (see photo).

3. Remove the tape and free up the ends of the Romex wire.

Connect the two insulated Romex wires to the appropriate lug screws on the sides of the duplex socket in the top outlet. The black wire goes to the brass colored lug, the white wire goes to the silver lug, and the bare copper ground wire connects to the bundle of ground wires in the back of the outlet box by way of a wire nut.

1. If you are trying to hide the transformer and its cord, you should first remove the phone from its attachment plate. Then pass the fish wire through the hole in the plate and through the wall space down to the opening in the cabinet below. In my case I had to remove the mounting plate from the wall because the hole in the plate was too small for the fish to make the bend downward.

2. If the phone cord is not attached to the mounting plate, tie a piece of string around that cord so you don't lose it down in the wall.

3. This time, you will bring the fish out of the opening below, tape the wall wart's plug to the fish wire, and pull it up through the phone's wall opening, leaving the transformer in the cabinet below just outside of the wall opening.

4. Pass both the transformer cord and the telephone cord through the hole in the phone mounting plate and re-attach the plate to the wall.

5. Plug the phone cord and the transformer cord into the back of the phone and then replace the phone on its attachment bracket (see photo).

1. Turn the power back on. Use the circuit tester on both upper and lower duplex sockets to insure that all leads, including ground wires are hooked up properly.

2. Turn the power off and push the sockets back into their respective outlet boxes and re-install the screws that hold them in. Put the socket covers on over both the sockets. In the cabinet, the wall wart will remain outside the wall and its cord will pass just under the lip of the outlet cover.

3. Turn the power back on one more time. Plug the wall wart into its new socket in the cabinet and check to see if the phone is operating properly (see photo).

The results were more that worth the effort. I probably did not spend $10 on the parts. And my wife was very happy to see the wall wart disappear.

This is a list of the tools and materials needed for this project:

1. About 3 feet of Romex 12/2 cable. This electrical cable has two solid 12 gauge insulated copper wires- one black and one white, plus a single bare copper ground wire, all inside of a plastic insulated sheath. Although I show a 15 ft package of Romex (for the sake of the photo), you can buy this wire by the foot at Lowe's or Home Depot.

2. One old work electric outlet box

3. One duplex electric socket

4. One duplex socket cover

5. Some masking tape

6. Wire fish- although you can buy these commercially made up in various lengths, I made a couple several years ago out of some 1/8-inch diameter steel rod from a hardware store. The rod is stiff enough to be pushed through wall spaces and insulation, but yet flexible enough to bend when you put it in an outlet hole in the sheetrock. For a small job like this one, some coat hanger wire would likely do the job.

7. Circuit tester- this device plugs into a wall socket and is mandatory when installing a new outlet. It has lights on it that will tell you whether a circuit is wired correctly and if the ground is connected.

8. Voltage detector- very nice to have and gives you some backup for the circuit tester as to whether there is some unexpected current in one of the wires in an outlet box. It happens.

9. Voltmeter- OK for testing the amount of voltage in a circuit, but not my favorite "failsafe" mechanism when working around live electrical wiring.

10. Wire strippers or a pocket knife for removing insulation. The strippers are nice to have, but the knife will strip wire and split the outer covering on Romex, which the wire strippers will not.

11. Pair of needle nose pliers

12. Flat blade screwdriver or two and possibly a #2 Phillips screwdriver depending on the kind of screws you encounter

13. Pair of wire cutters

I installed this out-of sight duplex outlet about 2 1/2 years ago. At the time I had not considered that the socket in the cabinet might be used for anything else. But, about 6 months later I decided to install a 4-gallon point of use water heater in the adjacent sink cabinet. I quickly determined that the electric outlet in the under-sink cabinet was not what electricians call a half-hot outlet. Some brief background information is in order.

The under-sink cabinets in most homes have a duplex electric outlet on the rear wall intended to power the garbage disposal. Some are wired so that both sockets are connected to the disposal wall switch next the sink, while others have one of the sockets always hot (the aforementioned half-hot outlet). If the latter is the case under your sink, you may be able to use the always hot socket in the outlet to power a small water heater. If you have the former arrangement, as I did, then you will need to find an uninterrupted power source elsewhere.

In my water heater project, I was fortunate to be able to drill a one-inch hole in the common wall with the adjoining cabinet where I had, a few months before, already installed a duplex electric wall outlet to hide my wall wart. I am always amazed at how two fairly different projects come together in a kind of unplanned synergy. Did the wall wart project unconsciously influence my thinking on the water heater installation? This much I do know; having that hidden duplex outlet in the cabinet next to the sink certainly saved me some time providing another source of electricity.

It is beyond the scope of this tutorial to address the legalities of doing these types of repairs. However, I will say that in most municipalities, the homeowner is allowed to make minor modifications in the electric system of his own home. Some towns will allow you to simply go online to apply for a permit, if one is needed, and describe what you are going to do. In the city where I live, one can obtain a homeowner’s electrician license just for his domicile, i.e., while he may do electrical work in his own home, he is not authorized to do so elsewhere. I passed a written test and got such a license a couple of years ago. With it, I am permitted to install up to 3 new circuits and do some other things. By the way, adding these branch outlet extensions is not considered adding new circuits; this project falls under the category of a minor electrical repair.

I realize that ordinances vary from city to city. In our town they use the NEC 2008 Manual, with some minor exceptions, as their electrical code. This project totally complies with that code and I have verified that not once but twice with code compliance electrical inspectors. They also said that a small electrical repair such as this would not require a permit nor an inspection. I will leave it up to you, the reader, to make certain that this project complies with your local code.

Most electrical repairs such as these extensions are quite easy to perform and should be good confidence builders. However, if you have doubts or are uncomfortable doing these projects, by all means, get some expert help- and learn from it. This is not rocket science, but there is an element of danger in working around electrical wiring, especially if you do not follow some basic safety rules.