Things You'll Need
GFCI circuit breaker
Ground-fault circuit interrupter (GFCI) devices monitor the hot and neutral lines in circuits to ensure that the current levels are equal. When the processor in the GFCI detects a disparity in the circuit, it trips the circuit, killing power. Where circuit breakers in the service panel protect the wiring in a home, a GFCI protects people from faulty appliances or when they are using appliances in damp conditions. While most GFCI devices are power receptacles linked to a single appliance, it is possible to install GFCI circuit breakers to protect entire circuits.
Replacing an existing breaker
Shut off power to the service panel through the main breaker.
Remove the old 220/240-volt breaker by unclipping it from the hot bus bars and disconnect the wires from the old breaker.
Connect the hot and neutral wires from the circuit to the setscrews on the GFCI breaker. A third neutral wire, called the pigtail, remains to be connected.
Connect the pigtail to the neutral bus bar.
Clip the breaker into place on the hot bus bars.
Restore power to the service panel and test the new GFCI by pushing the test button. The breaker should trip.
Adding a new GFCI-protected circuit
Make sure your box can accept another 220/240-volt circuit before beginning any work. There must be two adjacent unused spaces in the service panel.
Turn off the power to the circuit breaker box.
Remove the cover from the empty spaces in the service panel where you will be adding your new breaker by popping them out with your screwdriver.
Connect the breaker as described above.