WHAT IS A GROUND FAULT CIRCUIT INTERRUPTER?
These are receptacles that typically have the black and red test buttons on them (pictured above). GFCIs are found in outlets and service panels. They monitor the flow of current to and from appliances. If there's an imbalance in the flow, because of a frayed wire, a ground fault or a faulty device, current may attempt to travel through you, but the GFCI will quickly cut power to prevent any serious injury. Unless you have an outlet with a Ground Fault Circuit Interrupter (GFCI), you may be seriously shocked or burned because you may be the shortest route to the ground. Although they prevent electrocution, there is still a risk of electric shock.
GFCI Receptacles (Ground Fault Circuit Interrupter) - Safety Receptacles
They are required (by code) in many areas where electricity and water may come into contact. These areas include bathrooms, kitchen receptacles for countertop use within 6 feet of any sink, basements, pools, spas, laundry and utility rooms, garages and all receptacles located on the exterior of the home. At least one GFCI outlet is required in an unfinished basement.
There are GFCI outlets and GFCI-protected outlets which are outlets that are "downstream" of GFCI outlets, meaning that they are on the same circuit as a GFCI outlet, but do not have the red and black buttons on them. If there is no electricity to a GFCI-protected outlet, the GFCI outlet (at a separate location) might have tripped and disconnected electricity to this particular circuit. The reset button must be pressed in order to restore electricity to any downstream outlets.
You should test the GFCI outlets as soon as you move in, noting at the same time any protected outlets that may be present and which GFCI outlets control those protected outlets; typically the protected outlets should be labeled as such. Although they are proven life-saving devices, they are known to fail on a regular basis and should be tested monthly to ensure that they are functioning properly. DEFECTIVE GFCI's can become deadly.
To test the GFCI outlet, first plug a nightlight or lamp into the outlet. Turn the light on, and then press the "TEST" button on the GFCI outlet. The GFCI outlet's "RESET" button should pop out, and the light should go out. If the GFCI outlet is functioning properly, meaning that the light does go out, press the "RESET" button to restore power to the outlet. If the "RESET" button pops out but the light does not go out, either the GFCI outlet is not working properly or it is incorrectly wired. Call a qualified electrician to evaluate the problem. Usually the kitchen GFCI outlet will control any other outlets in the kitchen (sometimes more than one GFCI outlet is present in the kitchen). Sometimes all the bathroom outlets are placed on the same circuit, with only one GFCI outlet protecting the outlets in all the bathrooms. Occasionally a GFCI outlet in the garage will protect outlets in various bathrooms. Such garage installations can be inconvenient, particularly in multi-story buildings.
If GFCI outlets trip regularly, consult a qualified electrician immediately to determine why the tripping is occurring. GFCI outlets trip quite often when hair dryers are used on the circuit due to the electricity surge typically needed to start the dryer. If you notice this happening, try starting the dryer on the lowest setting and then moving up to the higher setting after a few seconds. If your circuit continues to trip, consult a qualified electrician for further evaluation.