How to Wire a GFCI Outlet

Using electricity in spaces that are wet, damp or often exposed to moisture can lead to injuries and damage to appliances and other electrical devices. Installing a GFCI outlet can help prevent this.

Before you learn how to wire a GFCI outlet, it's best to know what a GFCI outlet is and how it works. A GFCI receptacle has two connectors, one marked “line” and the other “load.” The line connectors monitor the power coming into the outlet. The load connectors monitor the power going “downstream" to other outlets on the circuit. When an electrical issue involves either what's coming in or out of a connector, a GFCI receptacle shuts the power off.

GFCI outlets can be used several ways inside or outside a home. For example:

• An entire circuit can be protected by a single GFCI device if the GFCI receptacle is the first outlet on that circuit.
• If the GFCI receptacle isn’t the first one in the circuit, only those outlets that are “downstream” from it are protected.
• GFCI outlets can also share the same circuit. For example, if the GCFI outlet shuts off in one bathroom, you’ll need to reset the outlets in both.

Here are the tools and materials you’ll need when wiring a GFCI outlet:

• Screwdriver
• Voltage tester
• Wire stripper
• Pliers
• GFCI outlet replacement
• Electrical tape

Safety Tip: The National Electrical Code (NEC) requires GFCI outlets in all wet or damp locations inside and outside the home. Check the code itself for the latest updates.

If an existing GFCI receptacle is damaged or quits working, it needs to be replaced.

• Turn off the power to the circuit in the breaker box.
• Remove the wall plate.
• Use a non-contact voltage tester to ensure that the power is off. Test the terminals on the outlet since the outlet itself may be tripped.
• Once it has been confirmed that the power is off, remove the outlet by backing out the two screws that hold it in the box.
• Carefully pull the receptacle out of the junction box and examine it before doing anything else. Does it have signs of overheating or sparking? Any cracks or breaks in the housing? If so, consider consulting a qualified electrician.
• If the wire is long enough to allow it, remove one connection at the time and transfer it to the new receptacle, being careful to keep things just as they were.
• If the wires aren’t long enough, use electrical tape to temporarily mark the incoming “line” power. This tape should be removed afterward, since it may confuse the next person who works on this system.
• Take photos to help keep up with your work.
• Make the new connections exactly as they were originally.
• Fold the wires back into the junction box.
• Secure the receptacle in the box with the two screws.
• Replace the face plate.
• Turn the breaker on.
• Test with a receptacle tester that will indicate any problems and test the GFCI system.

• Turn off the power at the breaker panel.
• Use a non-contact voltage tester to check the receptacle that will be changed.
• Remove the faceplate.
• Remove the existing receptacle from the junction box, but leave any wire connections in place for now.
• If only one set of wires are connected to the outlet, disconnect them. Then, connect these wires to the “line” side of the GFCI receptacle, secure it into the junction box, attach the faceplacte, turn the power on.
• Test with a receptacle tester to determine any problems, and test the GFCI system.
• If two or more sets of wires are connected to the existing receptacle, go to the next step.

• Turn off the power at the breaker panel.
• Use a non-contact voltage tester to check the receptacle that will be changed.
• Remove the faceplate.
• Remove the existing receptacle from the junction box but leave any wire connections in place for now.
• Check the existing outlet to see if the bridge between outlets is intact. If it is, there shouldn’t be two lines coming into the outlet, or there’s not a switch leg attached to one side.
• If the existing installation is standard, remove the wires from the outlet.
• Straighten or trim the exposed wires and cover all the ends with wire nuts.
• Ask an assistant to turn the power on at the breaker box.
• Use the non-contact voltage tester to determine which wire is providing power and which line carries the power to the next outlet.
• Have your assistant turn off the power at the breaker box.
• Use the tester to ensure the power is off.
• Connect the wires that provide power to the terminals marked “line” on the GFCI receptacle. The hot wire, usually black, should connect to the brass-colored terminal. The neutral, white, wire should be connected to the silver-colored terminal.
• Remove the tape that covers the “load” terminals on the GFCI receptacle, if present.
• Connect the wires that go downstream to the load terminals.
• Connect the ground wire, usually bare copper, to the green screw.
• Fold the wires into the junction box and put the receptacle in place. Secure it with the two screws.
• Attach the faceplate.
• Turn the power on.
• Test with a receptacle tester to indicate any problems, and test the GFCI system.

Test your GFCI outlets monthly to make sure they are in good working order. Press the TEST button. Then, press the RESET button. The indicator light should go out and come back on.

• If your GFCI outlets has a self-test light, it should be green. If it is red, try resetting it.
• If the GFCI outlet fails or it can’t be reset after tripping, replace it.