How to Wire Electrical Outlets - DIY Receptacle Wiring of Electrical Outlets

Installing an electrical outlet, even a GFCI outlet, is not a difficult task - the hardest part may be deciding which one to buy! There are literally dozens and dozens of possibilities, but only one or two are correct for any given application.

This article will walk the homeowner through not only how to install electrical outlets, but the purchasing as well. It is not intended to cover all the possibilities of receptacles to be installed and wired, only the normal, common types of outlets found in residential homes. The duplex (two spots to plug a cord into) in both 15 amp and 20 amp ratings as well as the GFCI (or GFI as it is often called) outlets will be discussed. Simplex outlets (one spot to plug into) are wired the same as the duplex outlet.

If you are installing a new outlet rather than simply replacing an existing one, please read the article about adding a new outlet; it contains tips and suggestions for pulling wire as well as wiring the new outlet into an existing circuit.

While there are many choices of new outlet, there will only be one or two that are a good choice for any give location.  Primary considerations include the following:

• Amperage. When installing a new electrical outlet the amperage must be considered. A 15 amp circuit should have only a 15 amp outlet on it. A 15 amp outlet may be placed on a 20 amp circuit as well, but 20 amp appliances will not plug into it and the value of the greater circuit ampacity is, to a large degree, lost. Never, never install a 20 amp outlet onto a 15 amp circuit - 20 amp appliances will trip the circuit breaker or fuse and could cause fires. A good indication if the circuit ampacity is to inspect existing outlets (the picture to the right indicates the difference in outlets) but a better method is to look at the circuit breaker or fuse that is feeding that circuit. Each will have the ampacity of the circuit stamped on it.
• GFCI outlet. These are more square looking outlets that have two small buttons on the front to test and reset the shock protection they offer. Any outlet installed within 6 feet of a water outlet such as a sink or tub must be GFCI protected, as must outlets installed in garages, outdoors or other "non-living" spaces. A possibility to look out for here is that the outlet being changed is protected by a GFCI outlet "upline" from it. If a different GFCI outlet that trips off also shuts off the outlet being replaced it is already protected and a normal outlet may be installed. GFCI outlets cost considerably more, but how much is your safety or life worth? Use one if necessary, and always replace a GFCI outlet with the same thing. In addition, any outlet being replaced that does not have a ground wire (either bare or green) connected to it must be replaced with the GFCI variety with a sticker attached indicating that there is no ground wire (stickers come with the new outlet).
• Color. A purely personal choice, of course, and not a requirement. There are many colors commonly available including ivory, white, gray and black, but more are available by special order. Cover plates are also available to match the outlet color.
• Style of outlet. Both regular and "decora" styles are commonly available. The decora designation refers to switches and receptacles of the square appearance (a GFCI looks similar, with buttons added to test and reset it).
  

If the task involves replacing an old outlet, that outlet must be removed first. Turn the power off before doing any work! A loud radio plugged into the outlet in question may help if the circuit breakers are not labeled properly. After turning the power off, check the outlet again, preferably with a plug tester or non contact voltage detector. Make sure it is off - being shocked is no fun, but there is no reason to suffer that indignity if you are careful about removing power before working on it. The picture to the right shows an outlet pulled from a pegboard wall that is till powered on.

Remove the cover plate and the two screws, top and bottom, that hold the outlet in place and gently pull the outlet out from the wall. If a voltage detector is available now is a good time to check once more for the presence of voltage on the wires. If the outlet is switched, and particularly if a switch controls only half of it, make careful note of which wire goes where. Label them with a piece of tape or other method and make a drawing of which wire goes where. Also label the wires to any GFCI that has more than one white, black and green wires attached to it. Wires to a GFCI outlet must go to the "line" and "load" terminals so if there is more than one set of wires  label which set (white and black) is "line" and which is "load".

Take note of whether or not the existing outlet has a ground wire (bare or with green insulation) connected to it. If not, and there is no ground wire in the box, a GFCI outlet must be installed (this is assuming that an "upline" existing GFCI outlet does not already protect it - as noted above that should have already been checked for).

If wires are connected to the screws on the side of the outlet loosen the screws (they should not come completely out) and remove the wires. If the wires are plugged into the back of the outlet there will be a small slot or hole next to the wire - insert a small screwdriver or other tool into the hole and while pressing in pull the wire out of it's hole. It may take a little pressure with the screwdriver to do this. If the wire can't be removed by this method, simply cut it off with wire cutters and strip about ½" of insulation so that once again the end of the wire is bare of insulation. Remove and discard the old outlet.

The next step is wiring and installing the new electrical outlet. If the old outlet was switched on just the top or bottom half, the new outlet must be prepared for that function as well. On the side of the outlet, between the two wiring screws, is a small tab connecting the two screws. The picture to the side shows such an arrangement, with a small screwdriver resting on the tab. Break the tab off so that the two screws are no longer connected.  Normally, only the tab between the brass screws is broken off - the tab between white screws is left alone.  Check the original outlet and prepare the new the same way.

Connect the wires to the new outlet. The ground wire (bare or insulated with a green color) goes to the green screw, usually near the bottom of the outlet. If by chance there is a ground wire in the box but it was never connected to the old outlet it must now be connected. An additional 6" piece of wire may be necessary to connect between two or more ground wires already in the box and the outlet. If so, add it by removing the wire nut holding the two existing ground wires together, add the new "pigtail" and replace the wire nut. Bend a small hook in the stripped wire and wrap it around the screw in a clockwise direction. If wrapped in the wrong direction it may tend to come off when tightening the screw. Tighten the screw firmly.

The white wires go to the white colored screws, or can be plugged into the back of a 15 amp outlet. Make sure they are plugged into the holes nearest the white screws. Black or other colored wires go to the more brass colored screws (or holes) on the other side. If you are looking at the front of the outlet, black wires go to to the right side. If the outlet was switched on either the top or bottom the black wires still go to the same side, making sure that the labels previously applied to the wires go to the same place. If labels have come off, the worst that can happen is the the switched part will reverse from top to bottom or vice-versa, so don't worry too much about it.

The back side of the GFCI outlet has two sets of screws or holes to use. One set is for the "line" side and one for the "load side".

Line side screws are for GFCI outlets that are stand alone outlets; they do not protect any "downstream" outlets. If you are replacing an old outlet without a ground wire and have more than two white or two black wires in the box, these wires will have to be "pigtailed" to the new GFCI outlet. To do this both white wires need to be connected together using a wire nut, along with a new 6" piece of white wire. All three white wires will be fastened together with the wire nut. The same thing must be done with the black wires. The new pigtails are now connected to the "line" side of the GFCI outlet with the white wires going to the white screws and the black wires going to the brass colored screws. Small lengths of wire are usually available to home improvement stores such as Home Depot.

Alternatively the new GFCI may be used to protect "downstream" outlets as well as itself - this is the preferred option. To accomplish this a tester, preferably a non contact voltage detector, will be necessary, as will some wire nuts. Separate all the wires in the box from each other if they aren't already separated and put a wire nut on each individual wire to cover any exposed copper wire. Turn on the power once more and check to see which wire is "hot" - that is, which wire is now powered. Mark that wire, being careful not to dislodge the wire nut; that wire will be the "line" side of the GFCI outlet.

Turn the power back off and verify with the tester that it is off. Trace the marked, black, wire into the box to find which white wire goes with it. Most houses use wiring in cables that have one white and one black wire; you are looking for the white wire that is cabled with the marked black wire. That white wire is also the "line" side of the new GFCI and will be connected to the white screw marked "line" on the GFCI outlet. The marked black wire will be attached to the brass screw marked "line" as well.

The remaining white and black wires are connected to the "load" end of the GFCI outlet (these screws are normally covered with a caution tape from the factory and such tape must be removed, but the outlet is also stamped with the words "line" and "load"). Electrical code requires that all outlets now protected by the new GFCI be labeled as such; stickers should have come with the new outlet. If there is no ground in the box, all the outlets must also be labeled with a "no ground" sticker.

Fold the wires neatly back into the box and push the electrical outlet into the box as well. The outlet is attached with two screws, one each at top and bottom - very occasionally the plastic boxes used in residential wiring will have the threads stripped out of the screw holes. Not to panic - a 1" long #8 sheet metal screw will work as well, although it cannot be repeatedly removed and put back without again stripping out the hole.

Attach the cover plate and turn on the power. It is best to check the new outlet with an outlet tester - these are small inexpensive testers made just for testing to see if an outlet is wired correctly.

Congratulations: you have learned how to wire and install a new electrical outlet and done it yourself! Another home repair task completed with a minimum of fuss or bother. If this task seems beyond your ability, I suggest you check out "Learning to do home repairs" by Wilderness. Of possible interested is also a hub recommending tools for the new homeowner as well as instructions for replacing a light switch or a new light fixture. Both are simple tasks as well, easily accomplished by the average homeowner.