Written by Dwight Kramer
Ground Fault Circuit Interrupters (GFCIs) are safety devices designed to protect you and your family from electrical shock. They are usually installed as protection in areas where moisture or dampness may contribute to a shock hazard; these areas include: outdoors, kitchen, bathrooms, basements, garages and storage buildings. Wherever there is potential for contact between a person and an electrical appliance in a damp or wet location, a GFCI should be protecting the circuit … and you.
How a GFCI works
Inside of a GFCI is a sensor that detects changes in current to the appliance by comparing the current flowing to the appliance and the current flowing back from the appliance. A mere difference of about 5 milliamperes turns off all power by tripping a relay within the GFCI within a few hundredths of a second. You might not even feel the shock, it happens so quickly!
GFCI maintenance is a very simple but extremely important procedure that should be performed monthly. These devices are just like any other electronic device in that sometimes they fail to perform properly.
All GFCI receptacles have two testing-related buttons on them. One is appropriately labeled TEST and the other is labeled RESET. Turn on an appliance or light fixture connected to the GFCI and press the TEST button. The appliance should immediately turn off. If it does not, the GFCI is either miswired or there is a problem with other wiring in the same circuit or with the device itself. In either case the GFCI should be replaced.
If the GFCI is functioning properly, pressing the RESET button will restore power to the appliance or circuit. If the GFCI is a circuit breaker, just turn the breaker back on to restore power to the circuit.
I highly recommend that you familiarize yourself with the GFCI protection installed in your home and the locations of the protective devices that control those circuits. Testing them on a regular basis and maintaining them as functional and properly operating GFCIs will ensure that you and your family are protected from the shock hazards associated with a ground fault.
NW Iowa Electrical Inspector Supervisor
Department of Public Safety