GFCI Protection for Downstream Outlets

Intro

Wiring for a ground fault circuit interrupter (GFCI) depends on where it falls in the circuit and whether you want it to protect the other outlets.

Turn off the power and look into the box to see whether the receptacle is at the start, end, or in the middle of a run. If it is in the middle or at the start, it can protect other outlets. Consider any drawbacks to protecting outlets in the circuit after the GFCI. Do you risk cutting off power to a freezer if the GFCI trips, for instance?

Checklist

Time
About 25 minutes to remove a receptacle and install a GFCI

Tools
Screwdriver, side cutters, strippers, lineman's pliers, voltage detector

Skills
Stripping and splicing wire

Prep
Lay a towel or small drop cloth on the surface below the receptacle.

Materials
GFCI receptacle, wire nuts, electrician's tape

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Step 1

Turn off the power. Test to make sure the power is off. Look inside the box to see where in the circuit the outlet falls. This box has two cables coming into it, making it a middle-of-run outlet. Disconnect the wires.

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Step 2

If you want the GFCI to protect itself and the outlets downstream, find out which wires supply power (the line wires). Cap all the wires with wire nuts except one black one and turn the power back on. Place a meter across the black wire and the ground wire or metal box. If there's no reading, it's a wire in the load cable; if it reads approximately 120 volts, it's a wire in the line cable. Double-check by repeating the test with the other black wire, turning the power off to move the wire nut and on to test the wire.

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Step 3

Connect the white line wire to the WHITE LINE terminal. Connect the other white wire to the WHITE LOAD terminal.

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Step 4

Connect the black line wire to the BLACK LINE terminal. Connect the other black wire to the BLACK LOAD terminal.

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Step 5

Pigtail all the ground wires together and connect the pigtail to the green ground screw on the GFCI. Wrap tape around the GFCI to cover the terminals. Attach it to the box and cover with a cover plate.

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