Standard 120-volt receptacles typically come in two amperage ratings: 15-amp and 20-amp. They look quite similar, but on a 20-amp receptacle, one of the vertical slots has a "T" shape. This is so that the special plugs on some appliances that need more power can be plugged into them. Standard cords and appliances can also be plugged into 20-amp outlets. Be sure to buy a new receptacle that looks exactly like the old one and has the same amperage rating. Most importantly, never install a 20-amp receptacle on a 15-amp circuit.
Identifying the Circuit Rating
In addition to the outlet type (15-amp or 20-amp), the circuit wiring and the circuit's breaker are important clues to the circuit amperage. Circuit wiring (usually non-metallic cable, or Romex) on 20-amp circuits contains 12-gauge wire and usually has a yellow outer sheathing. Cable for 15-amp circuits has 14-gauge wire and typically has white sheathing. The circuit breaker on a 20-amp circuit must be stamped with a "20," indicating a 20-amp rating; likewise, a 15-amp circuit must have a breaker stamped with "15."
Tools and Supplies You Will Need
- Replacement 15-amp or 20-amp receptacle
- Non-contact voltage tester
- Needlenose pliers
- Wire strippers (as needed)
Turn Off the Power
Shut off the power to the receptacle circuit by switching off the appropriate circuit breaker in your home's main service panel (breaker box). Use a non-contact voltage tester to check for power at the outlet location: Insert the probe tip of the tester into each of the receptacle's slots. The tester should indicate no voltage.
Test Again for Power
Remove the center screw on the outlet face plate, using a screwdriver, then remove the plate. Test for power again by inserting the probe of the voltage tester into the spaces alongside the body of the receptacle and touching all of the wires inside the electrical box, using the tester only (not your hands). The tester should indicate no voltage.
Examine the Wiring
Remove the mounting screws holding the receptacle strap to the wall box, and gently pull the receptacle out of the wall box, gripping the receptacle by the top and bottom "ears" of the receptacle.
Examine the wire configuration. In most cases, you will see three wire colors attached to the receptacle. Black wires are "hot" wires that carry live voltage; these are usually attached to the brass-colored screw terminals on the receptacle. White wires are neutral wires and are usually attached to the silver-colored screw terminals. Bare copper wires (or sometimes green insulated wires) are ground wires; one of these should be attached to the green grounding screw on the receptacle, while another may connect to the electrical box if it is metal (not plastic).
Some receptacles will have only one hot and one neutral wire attached to the receptacle, while others may have two hot wires and two white wires attached to the two sides of the receptacle. The wiring will depend on where the receptacle is within the circuit (middle-of-run vs. end-of-run) and on how the previous electrician chose to wire the circuit. In any case, your goal is to recreate the same wiring connections on the new receptacle.
Confirm the Amperage
Verify the proper amperage for the new receptacle. If the circuit has been wired correctly, a 15-amp circuit should be wired with 14-gauge wire. This circuit should be wired with a 15-amp receptacle. A 20-amp circuit should be wired with 12-gauge wire and a 20-amp receptacle. If you find a contradiction in the wiring—for example, if a 20-amp circuit breaker is feeding wires that are only 14-gauge—it's time to call a professional, as you have a potentially dangerous situation. If the circuit breaker, circuit wires, and receptacle all are consistent, you can proceed.
Remove the Receptacle
Disconnect the receptacle wires. Receptacles have two methods of connecting the wires: screw terminals on the sides of the receptacle, or push-in "back-wire" slots in the back of the receptacle. Most electricians believe that the screw terminal connections are more secure, and they usually avoid making back-wire connections. If your old receptacle has back-wire connections, remove the wires by inserting a small nail or flat screwdriver into the release slot next to each wire. The wire connection should loosen and pull free of the receptacle body. If your receptacle has screw terminal connections, loosen the screws and remove the wire loops from around the screws.
Wire the New Receptacle
Attach the bare copper or green insulated circuit wire to the green screw terminal on the receptacle. To do this, bend a C-shaped loop at the end of the wire, loop it in a clockwise direction around the green screw terminal on the receptacle, and tighten the screw firmly.
Attach the white neutral circuit wire(s) to the silver-colored screw terminal(s) on the receptacle. Form a C-shaped loop at the end of the wires, loop them around the silver screw terminals in a clockwise position, and tighten the screws firmly. NOTE: Some receptacles are designed so the straight ends of the wires are inserted into slots next to the screw terminals on the side of the receptacle. Do not connect more than one wire to a single terminal.
If the old receptacle was back-wired, don't use the back-wire fittings on the new receptacle unless they are the type that can be tightened with a screw. If not, trim off the bare end of each wire, then strip about 3/4 inch of insulation from the wire, using wire strippers. Bend the wire into a C-shaped loop to connect to the side screw terminal.
Attach the black (hot) wires to the brass-colored screw terminals, using the same technique. Do not connect more than one wire to a single terminal.
Mount the Receptacle
Tuck the wires neatly into the box as you push the receptacle into place against the box tabs. Secure the receptacle to the box with the two receptacle screws. Install the faceplate onto the new receptacle.
Turn On the Power
Restore power to the circuit by switching on the circuit breaker, then test the receptacle for proper operation.