A Ground Fault Interrupter outlet (also
referred to as GFCI or GFI) is a device that protects you
from an electric shock. The most common locations to find
GFCI outlets are in the kitchen and bathrooms of a house.
They are easily spotted by their distinctive face. Normally
there are two buttons in the middle of the face, a red test
button and a black reset button (Figure 1). Sometimes knowing
if a circuit is ground fault protected is not as easy as
simply spotting it because the ground fault interrupter
may be located somewhere else like another bathroom, in
the basement, or in the main circuit panel box. It is possible
to ground fault protect an outlet from another location.
If properly wired, outlets downstream from a GFCI will be
protected (up to approx. 4-6 outlets). The 1999 National
Electrical Code (NEC) states that GFCI outlets are required
to be installed in all wet locations in new construction
as well as remodeling projects. This means that countertop
outlets in bathrooms and kitchens, and exterior outlets
should be protected if it is a newer house or has been remodeled
recently. In older buildings built prior to the invention
of and requirement of GFCI outlets may not have any in the
house. Although not required in existing homes built prior
to the NEC requirements (unless recently remodeled), it
is strongly recommended installing them in their proper
How Do They Work?
How a GFCI outlet works is it monitors the
amount of current going to and coming from a receptacle.
Whenever the amount of incoming and outgoing current are
not equal, indicating current leakage or a "Ground Fault"
the GFCI opens the circuit instantly, cutting off the electricity.
The protection of GFCI outlets lies with their quick response
and sensitivity. GFCIs are designed and built to trip in
approx. 1/40 of a second in the event of a ground fault
of 0.005 ampere. This is important because circuit breakers
are designed to only trip once the circuit has exceeded
the designed amount of ampere (or amps), which is usually
15 or 20 amps. Manufactures of GFCI devices state that the
GFCI outlets should be tested at least once a month to ensure
proper function ability.