How to Wire a Ground Fault Circuit Breaker


A Ground Fault Circuit Interrupter (GFCI) can save you from being accidentally electrocuted in your home. A GFCI works by comparing the electrical current flowing to the load with the current returning from the load. If they are not equal, it means that electricity is flowing somewhere it shouldn't--through your body, for example--so the GFCI instantly opens the circuit to stop the current. While GFCI electrical outlets are more commonly used in the home, GFCI circuit breakers last longer and are a better choice if you do not test your GFCI outlets on a regular basis.

Things You'll Need

  • Safety glasses
  • Rubber gloves
  • Battery-operated light source
  • Insulated screwdriver
  • Examine your service panel and the surrounding area. If you see moisture or rust on or near the panel, or have any doubts about your ability to do this task safely, hire an electrician to do the job. Otherwise, put on your rubber gloves and safety glasses, then turn off the main breaker in the service panel. Remove the screws that hold the panel cover in place and remove the cover.

  • Pry out the breaker that you wish to replace and disconnect the wires. Read the wire size printed on the cable to verify that the GFCI breaker matches the circuit wiring; you must use a 15-amp breaker with 14-gauge wire and a 20-amp breaker with 12-gauge wire.

  • Attach the black wire that was connected to the old breaker to the hot terminal on the GFCI breaker. No more than 1/4 inch of exposed wire should show outside the breaker. Trace that black wire back to the cable where it enters the service panel. Follow the white wire from that same cable to find where it attaches to the metal bar with all the screws on it. This metal bar is known as the neutral bus.

  • Loosen the screw holding the white wire against the neutral bus and remove the wire. Connect the white wire to the neutral terminal on the GFCI breaker. Again, no more than 1/4 inch of exposed wire should show outside the breaker.

  • Follow the breaker manufacturer's directions for inserting the breaker into the panel. The wiring end of the breaker is usually inserted first, and the other end is then pushed down until fully seated on the center tab.

  • Fasten the GFCI breaker's curly white wire underneath a screw on the neutral bus; you might even be able to put it under the same screw from which you removed the straight white wire earlier. Replace the cover on the service panel.

  • Switch the main breaker back on then turn on the GFCI breaker. Press the "Test" button on the breaker and the breaker should trip. Reset the GFCI by pushing the switch fully off and then on.

Tips & Warnings

  • The cables which bring electricity to your service panel from the outside will still be hot after you have turned off the main breaker. These thick cables usually enter the service panel at the top: do not go anywhere near them.
  • If you accidentally reverse the hot and neutral wires on the GFCI breaker, the circuit may still test normally, but you may not have ground-fault protection. Use a polarity tester on a circuit outlet, if you wish, to verify that the wires are properly connected.
  • A GFCI should not be used with lights, freezers, refrigerators or medical equipment. A GFCI cannot be used with appliances which are individually grounded, such as ovens or dryers.

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  • "Wiring a House;" Rex Cauldwell; 2002
  • Photo Credit Jupiterimages/ Images
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