Overview: Wiring an Outlet
Outlets and switches are the electrical devices that get the most use in the house, and they do wear out. You’ll know a receptacle needs replacing if it’s cracked, or if the plug isn’t held tightly in the receptacle. Wiring an outlet, a new one, is important for your own safety. Over time, cheap outlets that are well used simply lose their grip. Other reasons to replace an outlet might be a desire to change the color or style, or to install a ground-fault circuit interrupter (GFCI) outlet (“shock stopper”) or a tamper-resistant (“childproof”) outlet for safety.
In almost every instance in a home, it’s OK to use a 15-amp-rated receptacle or GCFI. A special 20-amp-rated receptacle is needed only when an appliance or tool that uses more than 15 amps (and so equipped with a special plug) is going to be plugged in.
Cheap standard receptacles (and most switches) have “push-in” terminals, where a spring inside grabs the wire. These can get weak and fail sooner or later. Avoid using this method of connecting a wire to a receptacle.
RECEPTACLES DON’T LAST FOREVER.
A cracked outlet should be replaced as soon as possible before it fails and causes a shock or a fire.
Left to right below, a standard receptacle; a heavier-duty, specification-grade receptacle; and a GFCI receptacle. The upgrade to specification grade is well worth it. GFCIs are required by Code in bathrooms, kitchens, garages, outside, and other locations. All styles come in different colors.
Removing Old Outlet/Receptacle
Wiring an outlet or replacing is a straightforward repair, and safe—as long as you first cut power at the breaker. Test for voltage to verify that the power is off, using both volt-tick and voltage-continuity testers, and then disconnect the receptacle. Label the wires. Figure out the wiring configuration.
TURN OFF THE POWER AT THE BREAKER. Don’t trust the labels; verify by testing that you’ve got the right breaker.
There may be a second circuit, live, in any box, so always test for voltage even if the power to the receptacle has been shut off.
Receptacle Wiring Configurations
Check for Damaged Wire Insulation
Sometimes when a razor knife is used to remove the cable sheath or jacket, the wire insulation is cut. The bare wire is unsafe and must be fixed before the new receptacle is installed. Wrap two layers of tape on the diagonal over damaged areas, overlapping half the width of the tape. Cut the tape to length rather than tearing it, and you’ll get a longer-lasting repair.
WRAP AND COVER. If the insulation on a wire is nicked or torn, wrap it with high-quality electrical tape. Use tape that’s the color of the wire insulation.
“Push-in” Backwire Terminals
If you’re replacing an outlet with “push-in” terminals, you have two options for disconnecting the wires. If the wires are long enough, just cut them off flush with the back of the device. If they’re short, use a very small screwdriver to release them.
Wiring an Outlet or Installing new one.
Basically, you should strip about 5 in. of insulation from each wire, form a loop, place it under the terminal screw, and tighten the screw. If there are two black or two white wires, you can place one on each screw. By convention, black wires are the “hot” or supply wires and go to the brass-colored screws; the white wires are the “neutral” or return wires and go to the silver-colored screws. The green-insulated or bare copper wire(s) are the equipment grounding wire(s), which are key to safety for tools and appliances with three-prong plugs. The ground wire connects to the grounding screw, which is typically green. If there’s more than one ground wire, you must splice them together and include a short jumper wire (called a “pigtail”) to connect to the single terminal of a switch or receptacle.
- LOOP AND TIGHTEN. Orient the loop on the terminal screw so that tightening the screw clockwise closes the loop.
- CONNECTING TWO CABLES. With two cables in a box (for a middle-of-run circuit), use the device terminals to make the connections. One cable brings power into the box and is connected to the receptacle; the other cable, also connected to the receptacle and so to the first cable, carries power to the next device in the circuit.
- CONNECTING THREE CABLES. In a receptacle box with three cables, you splice the three black wires together with a pigtail, which connects to the receptacle terminal. Do the same with the white wires and twist on the connectors, which need to be good and tight.
- TUCK IN THE WIRES. Fold the wires back into the box, making a Z so that the wires accordion back in neatly.
- SCREW THE RECEPTACLE INTO THE BOX. Run one screw in half way, then the other, and then finish off both screws.
- CHECK ALIGNMENT. Make sure you wiring an outlet vertically, either by eye or with a level.
- INSTALL THE COVER PLATE. Set the screws so the slots are vertical. It just looks better that way.
Ground-fault circuit interrupter receptacles (GFCIs or GFIs) shut off (interrupt) power if there’s even a minute amount of power leaking from the circuit through some unintended path. This will protect you from a bad shock or electrocution if, because of a broken or frayed wire, the power is leaking through you.
GFCI Outlet (or GFCI circuit breakers) are required on circuits that serve receptacles in the kitchen, bathroom, garage, outside, and other locations. These locations present the greatest risk of someone using electrical items when they’re in contact with water or the ground. These GFCI outlets (and better-quality regular outlets) have clamp-type terminals to make connections. These are easy to wire and make very good connections. You strip the insulation off the wire, insert it into the hole, and tighten a screw to clamp the wire tight.
Wiring a GFCI Outlet
GFCIs have two sets of terminals on the back: One is marked “LINE” (for incoming wires) and the other is marked “LOAD” (for outgoing wires that need GFCI protection, like those going to other kitchen counter outlets). The stripped neutral of the cable providing power fits into the hole next to the silver-colored screw. When the silver screw is tightened, a clamp inside securely grips the wire. The arrangement is the same for the black wire.When everything is done, closed up, and powered up, use a plug-in tester to check polarity. If there’s a problem, cut power and check your work. If you can’t identify the problem, call an electrician.