GFCI stands for "ground fault circuit interrupt," a fairly sophisticated circuit breaker used to protect your home from power surges. It represents an improvement over regular circuit breakers, because it is more resistant to leaky water, which can be a hazard in a damp basement or neglected corner of the house. You can install circuit breakers of any sort yourself, without needing to hire an electrician. In the case of GFCI circuit breakers, you simply need to connect one additional wire.
Things You'll Need
Turn the main breaker in your circuit box to the "off" position, cutting off electricity to the entire house.
Unscrew the metal panel framing the row of circuit breakers and set it aside.
Find the breaker you need to replace and turn it to the "off" position. If you are installing the GFCI circuit breaker in a new position, clip off the appropriate metal tab with a pair of pliers.
Pop out the old circuit breaker (it should come right out) and unscrew the connecting wires from the terminal screws. Be sure to note which screw corresponds to which wire. If you are installing the GFCI breaker in a new position, pull out the three wires corresponding to that position and strip the insulation off the ends of the wire with a pair of wire strippers.
Make sure the new GFCI circuit breaker is turned to the "off" position. Then connect the coiled pigtail wire to the terminal screw on the grounding bar.
Connect the remaining two wires to the terminal screws on the GFCI breaker: the hot wire (usually black) to the terminal marked "power" or "load power" and the neutral wire (usually white) to the terminal marked "neutral" or "load neutral." Tighten the terminal screws firmly into place.
Snap the GFCI breaker into position, making sure that the wires aren't pinched or caught in anything.
Turn the main power switch back to the "on" position, then turn the GFCI switch to the "on" position.
Find the test button on the new circuit breaker and push it. If the breaker is working, it will switch to the "off" position and shut off the power.
Place the metal frame back around the row of breakers and screw it into place, then close the power box.
A new GFCI circuit breaker should always match the amperage of the old breaker you are replacing. Check the listed amps for both breakers and make sure the numbers are the same before you work.
Don't forget to stay safe while replacing a GFCI circuit breaker. Stand on rubber when you're working (either stand on a rubber mat or wear a pair of shoes with rubber soles). If you have a multimeter or a voltmeter, use it to test the wiring before you touch it. The wiring shouldn't have any electricity running through it while you work.