A ground fault control interrupter (GFCI) is an electrical outlet with a built-in circuit breaker that is required equipment in key positions in the home, according to the National Electrical Code (NEC). GFCIs function by monitoring the current passing through the outlet. When there is a dip in the amount of current leaving the circuit compared with the amount of current entering the circuit--a ground fault--they cut the power to the outlet and anything that is plugged in. A GFCI can prevent a fatal electric shock, so it should be tested monthly.
Test the GFCI using the onboard indicator light if your outlet is so equipped. Units of this type have a light that is on unless the breaker has been tripped. Push the "Test" button located between the two outlets on the unit. If the light goes out, the breaker in the GFCI is working properly. Press the "Reset" button to restore the GFCI's functionality.
Plug in a night light if your unit does not have an indicator light. Push the "Test" button to break the circuit. If the light continues to shine, the GFCI is faulty and needs to be replaced. As with the indicator light, if the night light goes out, the receptacle is working properly. Press "Reset" to restore the circuit.
Plug in a small appliance to the GFCI and perform the test. If you are able to turn on the appliance after you have pressed the "Test" button, the GFCI has failed and needs to be replaced.
Test your appliances that have an onboard GFCI in the same way. Many hair dryers have a GFCI built in to the plug. They also include two buttons--one to "Test" and one to "Reset." If the appliance works after you have pushed the "Test" button, replace the appliance. Do not attempt to fix the GFCI.
The NEC stipulates that new construction includes GFCIs in outdoor receptacles (1973), bathrooms (1975), garages (1978), kitchens (1987), and basements and crawlspaces (1990)