Electrical Basics ~ Ground Fault Circuit Interrupter

The Ground Fault Circuit Interrupter or GFCI, senses any leakage or loss of current, on a electrical circuit, that may be flowing through a person. When the GFCI detects a ground fault, it will shut off the power at the outlet, before injury or electrocution can occur.

The NEC requires that GFCI outlet protection be installed in, bathrooms, kitchens, garages, unfinished basements, outdoors and similar areas.

What Is A Ground Fault?

A ground fault is the unintended electrical path between a power source and a
grounded object. Often, ground faults occur when equipment is damaged, such that live electrical parts are no longer protected from unintended contact. If your body provides the path to the ground for this current, you could be shocked or even electrocuted.

For example... A bare wire, inside an kitchen appliance, touches its metal case. The case is then energized with electricity. If you touch the appliance with one hand while another part of your body is touching a grounded metal object, such as a faucet, you will get shocked. If the appliance is plugged into an outlet protected by a GFCI, the power will be shut off before a fatal shock can occur.

While the reaction time is fast, you may still encounter a shock in the time that the GFCI takes to cut off the electricity.

A GFCI circuit breaker can be used in some situations. When installed, they provide protection from electrocution, excessive leakage current and over current, over an entire branch circuit. You may find this useful when feeding a unfinished basement or garage.

Note: Not all electrical panels will accept GFCI breakers. You'll want to check before starting your project.


GFCI outlets are commonly used outdoors, in bathrooms, kitchens and similar areas. They can be installed in place of standard outlets, to provide protection, for a single outlet or a series of receptacles on a branch circuit. They can also be used to replace older ungrounded, two-prong outlets. These outlets, must be labeled “NO EQUIPMENT GROUND GFCI PROTECTED” to identify that the outlet is not grounded.

Used where installed GFCIs are not practical, a GFCI "plug in" or portable device, may be plugged into receptacles, where appliances will be used. Both two and three pronged receptacles can be protected using a plug in device.

Another type of portable GFCI is an extension cord combined with a GFCI. It
adds flexibility in using receptacles that are not protected by GFCIs.

These can also be used, where installed GFCIs are not practical. For instance, working with power tools, electrically powered yard equipment or remodel and construction sites.

Whether your using a GFCI breaker, receptacle or plug in, it is recommended that they be tested once a month.

To test the GFCI, press the TEST button. There should be an indication that the power is off. Use a lamp or blow dryer to confirm operation. To complete the test and restore power, simply press the RESET button.

GFCI vs. AFCI (Arc Fault Circuit Interrupter)

While both, GFCIs and AFCIs are important safety devices, they have different functions. GFCIs are intended to prevent electrical shocks, while AFCIs are meant to prevent electrical fires.

See: GFCI Wiring Diagrams >