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Outlet Wiring BasicsContinue to 2 of 11 below.
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000000000000The wire connections for outlets must be made carefully to ensure safety and proper operation. A wire coming loose from an outlet can create a serious fire or shock hazard. The safest way to connect wires is to use the outlet's side screw terminals, a procedure known as sidewiring. Another common method, called backwiring, uses self-clamping rear terminals that do not screw down the wire; this method is unsafe because the wires can come loose from these terminals.
Never connect more than one wire to a single terminal. If there is more than one cable in the electrical b0ox, use pigtails to connect the receptacle. A pigtail is a short length of wire that you install between the outlet terminal (or ground screw) and a connection of multiple circuit wires.
Before touching any wires in an electrical box, always test each wire for power with a non-contact voltage tester to make sure the power is off. Before conducting the test, make sure your tester is working properly by first testing it on an outlet that you know is hot (energized); the tester should light up, indicating it is working.Continue to 3 of 11 below.
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Tools and Materials You Will Need
- Non-contact voltage tester
- Cable ripper
- Cutting pliers or utility knife
- Wire strippers
- Scrap NM cable (as needed)
- Wire connectors (wire nuts)
- Needlenose pliers
- Outlet with cover plate
- Phillips screwdriver
Important Notes on Materials
Ensure that the outlet and cable are compatible. The color of the cable sheathing usually will indicate the gauge and amp rating of the internal wires. If the electrical cable has white sheathing, typically this means that it is a 15-amp, 14-gauge cable. You would then use a 15-amp outlet. If the cable is yellow, this typically signifies a 20-amp, 12-gauge cable. You would use an outlet rated for 20 amps. This outlet usually has a T-shaped slot on the left side.
Many areas now require tamper-resistant (TR) outlets for new installations. Identified by a "TR" imprint, these outlets have internal wings, or shutters, behind the slots that don't open unless you insert two prongs from a plug at the same time. This helps prevent children from getting shocked by inserting a knife, pin, or paper clip into the outlet.
Most electrical codes require that the edge of the receptacle box is recessed no more than 1/4 inch from the finished wall surface. If the box is embedded too deeply, you can install a box extender ring to bring the box up to code.
If any electrical box is metal, you must add an extra grounding pigtail to the circuit ground wire(s) and connect the pigtail to the ground screw on the metal box. All metal boxes must be grounded to the circuit wiring. Plastic electrical boxes do not require grounding.Continue to 4 of 11 below.
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Turn Off the Power
Locate your home's electrical service panel. Also known as a breaker box or fuse box, the service panel is usually located in a remote area, such as a basement, kitchen pantry, garage, hallway, or closet or on an outdoor wall. Turn off the power to the circuit for the new outlet by switching off the circuit breaker. Go back to the outlet that you intend to work on. Use a non-contact voltage tester to test each of the wires in the outlet's electrical box. The test should verify that no voltage is present in any of the wires.Continue to 5 of 11 below.
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Prepare the Cable(s)
Electrical cables feed through holes in the back or bottom of the outlet's electrical box. Each cable should extend about 6 or 7 inches beyond the leading edge of the box to provide ample working room. Cables that extend beyond that length become unwieldy and difficult to stuff into the box. If any cables extend further, trim them with cutting pliers or wire cutters so they extend only 6 or 7 inches past the front of the box.
Remove the sheathing, or outer jacket, of each cable, with a cable ripper. Clamp the ripper over the cable as far back into the box as possible. Pull the tool toward the end of the cable to cut through the sheathing. Peel the sheathing away from the wires inside the cable and trim it off about 1/2 inch to 1 inch from where the cable is clamped to the back of the electrical box, using cutting pliers or a utility knife.
Note: If you're replacing an old outlet, you probably will not need to prepare the cable(s) in the box, or strip the individual wire ends (next step).Continue to 6 of 11 below.
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Strip the Wire Ends
Strip the plastic insulation from the end of each insulated wire in the box, using wire strippers. If you are replacing an old outlet, make sure that the ends of the wires are in good condition and have no nicks or scorch marks; if they do, trim off the damaged portion and strip the insulation 3/4 inch from the end of the wire.
Note that if you have two cables running into the box and are adding pigtails, strip the end of each wire only about 1/2 inch. This is because these wires will connect to the pigtails with wire connectors (wire nuts). Follow the wire nut manufacturer's directions for how much to strip. If you strip too much insulation, the wire nut will not cover the bare metal end of the wire.Continue to 7 of 11 below.
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Install Pigtail Wires
Install pigtails if there is more than one cable in the box. Using a scrap of the same type of circuit cable, cut 6-inch lengths of each type of wire in the cable. Strip one end of each pigtail at 1/2 inch and the other end at 3/4 inch. The 1/2-inch end will be connected to the circuit wires with a wire nut, while the 3/4-inch end will be shaped into a hook and connected to an outlet screw terminal.
Join the bare copper (or green insulated) pigtail to the ground wires in the circuit cables, using a wire connector, following the manufacturer's directions. Do the same with the white (neutral) pigtail, then the black (hot) pigtail, so you have one ground, one white, and one black pigtail.
Note: If the electrical box is metal, install an additional grounding pigtail and connect it to the ground screw on the box. The outlet will have its own separate grounding pigtail.Continue to 8 of 11 below.
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Connect the Ground Wire
Form a U-shaped hook on the end of each wire (or pigtail), using needlenose pliers. Fit the hooked end of the ground wire around the ground screw of the new outlet.
The hook must wrap around the screw in a clockwise fashion so that the opening in the hook is on the right of the screw. This way, the screw will close the hook as you tighten the screw. If you wrap it the other way, the screw opens up the hook.
Use the pliers to squeeze the hook closed around the threaded shank of the screw. Tighten the ground screw with a Phillips screwdriver. The hook should fit snugly around the shank of the screw. The wire insulation should come up close to the screw but should not be under it.Continue to 9 of 11 below.
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Attach the Neutral and Hot Wires
Connect the white neutral wire or pigtail to one of the silver (neutral) screw terminals on the outlet. Connect the black hot wire or pigtail to one of the brass (hot) screw terminals on the outlet. Use the same technique described for the ground screw, where the hook-shaped end fits clockwise around the screw.
For standard outlet wiring, the white neutral wire can go on either silver terminal, since they are interchangeable. Likewise, the black hot wire can go on either brass terminal.Continue to 10 of 11 below.
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Attach the Outlet to the Box
Confirm that all wiring connections are secure by gently tugging on each wire. Reconnect and retighten any loose wires. Carefully tuck the wires into the box; it often helps to bend them in one or two places, but do not create sharp bends. Hold the outlet against the box edge and secure it to the box with the screw at the top and bottom of the outlet.
The outlet can be oriented with the ground slot (D-shaped hole) facing up or down. Technically it is safer to have the ground slot on top. If a cord plugged into the outlet is partially pulled out, exposing the plug's prongs, and something were to fall onto the prongs, it is safest if the object contacts the ground prong rather than the hot or neutral prong.Continue to 11 of 11 below.
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Install the Cover Plate
Fit the outlet cover plate over the outlet and secure it with its screw. Restore power to the circuit by switching on the circuit breaker. Plug in an electrical device to the outlet to make sure the outlet is working properly. You can also use an inexpensive plug-in receptacle tester to confirm that the outlet has power and is wired correctly and is properly grounded.