How A GFCI Circuit Works
A typical household circuit has a fuse or circuit breaker which is rated at 15 or 20 amps.  An electrical shock of 10
milliamps (1/100 of 1 amp) is enough to stop a human heart resulting in death.  A ground fault circuit interrupter (GFCI)
can help prevent this type of electrocution inside and outside the home.  The GFCI circuit monitors the amount of
current exiting one side of the circuit and compares it with the amount of current returning.  With a properly operating
appliance/device the current will be the same exiting and returning.  When someone receives an electrical shock the
current is exiting the device, but is traveling through the person and going to ground (a ground fault).  If the GFCI circuit
detects that 6 milliamps or more of the electrical current leaving the device is not returning, it turns the current off.  By
installing GFCIs in every home in the United States, the U.S. Product Safety Commission (CPSC) estimates that more
than two-thirds of the approximately 300 electrocutions occurring each year could be prevented.
GFCI Receptacle
Use of GFCI Protection on an Ungrounded Circuit
The National Electric Code permits the use of GFCI protection on an ungrounded circuit (e.g. a 2-prong or 'open ground' 3-prong
receptacle).  The receptacle must be labeled indicating the lack of a grounding conductor.  While this method can reduce the risk of a fatal
electrical shocks it does
NOT reduce the overall risk of electrical shocks.  An electrical shock strong enough to trip a GFCI circuit is still very
painful and could cause injury.  An ungrounded GFCI circuit also does not provide the surge and static protection offered by a properly
grounded circuit.  For these reasons I personally do not recommend the use of GFCI circuits in place of a 2-prong, ungrounded outlet
except in areas where a GFCI circuit should be installed anyway.

GFCI'S Must Be Tested Regularly
GFCIs are an effective means of reducing the risk of death or serious injury due to electrical shocks, however, they must be tested regularly
-- UL recommends once a month -- to verify they are working properly.
Like all products, GFCIs can fail or become damaged and cease to function correctly.  GFCIs devices can be damaged by lightning or
electrical surges.  A simple test once a month and after any violent thunderstorm should be conducted.

To properly test GFCI receptacles in your home:
  • Push the "Reset" button located on the GFCI receptacle, first to assure normal GFCI operation.
  • Plug a night light (with an "ON/OFF" switch) or other product (such as a lamp) into the GFCI receptacle and turn the product "ON."
  • Push the "Test" button located on the GFCI receptacle. The GFCI should trip (makes a click sound) and the night light or other
    product should go "OFF."
  • Push the "Reset" button, again. The light or other product should go "ON" again.

If the light or other product remains "ON" when the "Test" button is pushed, the GFCI is not working properly or has been incorrectly
installed (mis wired). If your GFCI is not working properly, call a qualified electrician who can assess the situation, rewire the GFCI if
necessary or replace the device.
"GFCIs are proven lifesavers, however, consumers need to take a few minutes each month to do this simple test. By taking action, you can
help protect your family from the risk of electric shock," says John Drengenberg, UL Consumer Affairs Manager.

Types of GFCI Devices
Several types of GFCIs may be installed in/around your home.
  • GFCI Receptacle -- This type of GFCI -- the most widely used -- fits into a standard outlet and protects against ground faults
    whenever an electrical product is plugged into the outlet.  Wall receptacle GFCIs are most often installed in kitchens, bath and
    laundry rooms, and outside where water and electricity are most likely to be in close proximity.
  • GFCI Circuit Breaker -- In homes equipped with circuit breakers, this type of GFCI may be installed in a panel box to give protection
    to selected circuits. Circuit breaker GFCIs should also be checked monthly. Keep in mind that the test will disconnect power to all
    lights and appliances on the circuit.
  • Portable GFCI -- A portable GFCI requires no special knowledge or equipment to install. One type contains the GFCI circuitry in a
    self-contained enclosure with plug blades in the back and receptacle slots in the front. It can then be plugged into a receptacle, and
    the electrical products are plugged into the GFCI. 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. Portable GFCIs should only be used on a temporary basis and
    should be tested prior to every use.
Ground Fault Circuit Interrupter Protection
Recommended Locations for GFCI Protection
  • All bathroom receptacles
  • Kitchen counter top receptacles , especially within 6 feet
    of a sink
  • Any receptacle near a sink
  • All exterior receptacles
  • Receptacles in garages
  • Receptacles in crawlspaces
  • Receptacles servicing or near pools and spas

Where to Not Use GFCI Protection
A GFCI can trip due to surges during normal cycling of motor
driven appliances.  This is mostly an inconvenience, however it
can result in damage (food spoilage, flooding due to non-
operational sump pump).  If GFCI protection is not used, then
ensure that the appliance is properly grounded to reduce the
risk of electrical shock.  The design of modern appliances and
GFCI devices has reduced incidences of nuisance tripping.
  • Refrigerators and freezers
  • Sump pumps
  • Sewage ejector pumps