Ground fault circuit interrupter (GFCI) receptacles are designed to prevent electrical shocks by automatically shutting off power to the receptacle if the device detects an imbalance in the current. Wiring an end-of-run ground fault circuit interrupter (GFCI) receptacle is necessary when wiring in a new whirlpool bath, hot tub or a small swimming pool. The receptacle is an alternative to installing a GFCI circuit breaker to protect all the receptacles on the circuit. GFCI receptacles can be installed on old Edison Base fuse panels, but GFCI circuit breakers can't be installed in a fuse panel.
Turn off the branch circuit breaker or remove the Edison base fuse. Check for current by turning the non-contact voltage tester on and bringing it near the wiring in the receptacle box. The voltage tester will beep loudly if there's voltage still present in the box. Some boxes may have more than one circuit. You will need to turn off more than one circuit breaker or remove more than one fuse before working in the box if this is the case.
Remove the outer, plastic jacket from the ROMEX® cable in the box. Use the razor knife to slit the jacket down the center. Peel the jacket away from the individual wires, then cut it off the cable. Be careful not to damage the insulation on the individual wires when removing the cable's outer jacket.
Adjust the cutting depth of the wire strippers using a scrap piece of wire the same size as the circuit wires. Loosen the wire stripper's adjustment screw. Apply pressure to the wire stripper's grips until the wire stripper's jaws cut through the wire's insulation. Your objective here is to cut through the insulation without cutting into the bare copper. Set the wire stripper's cutting depth and tighten the wire stripper's adjustment screw.
Remove 3/4 inches of insulation from the ends of the insulated wires in the box and then make loops in the stripped ends with needle-nose pliers. The opening in the loops should be just large enough to slip around a terminal screw on the GFCI receptacle.
Locate the set of terminal screws marked "Line" on the back of the GFCI receptacle. The second set of terminal screws marked "Load" should have a piece of yellow tape across them.
Connect the black wire to the brass-colored "Line" screw and the white wire to the silver screw. Place the loops around the screws in a clockwise direction and tighten the screws. Connect the bare copper ground wire to the green, octagon shaped screw.
Wrap the terminal screws with several turns of electrical tape as an extra precaution against accidental short circuits.