Al - Ga Amateur Update no. 42
Monday, July 19, 1999

What is a GFCI?
What does a GFCI do for us?
Who requires GFCI's in your house?

I thought I'd write a short fact sheet on the purpose and use of a GFCI.

This device may save you or a family member from a dangerous or fatal shock!

First of all a GFCI is a Ground Fault Circuit Interrupter. It's purpose is to protect
people using electrical circuits and appliances. 
The GFCI will open the circuit if a current leakage or fault (to ground) exceeds 0.006 A, (6 mA). 
Note, a person can be electrocuted by a current of only 2 mA.
Normally the current going to the appliance or device along the ungrounded ("hot) wire and the 
current returning to the source along the white or grounded neutral conductor are equal.
During a ground fault or short circuit (to ground), however, an imbalance occurs and the difference 
represents a dangerous shock hazard. A GFCI, monitoring the circuit, will sense any imbalance greater
than 6 mA and will immediately open the circuit, stopping the dangerous current flow. 
If a GFCI is tripped, it can be reset by pressing the red button on the receptacle or on the GFCI breaker. 
They may be tested by pressing the test button on each unit. If they seem to trip for no apparent reason, 
have an electrician check out the circuit and find out what is causing the GFCI to activate.

The National Electrical Code requires GFCI protection at the following:
1.   ALL 125 V, single-phase, 15 and 20 A receptacles in bathrooms and outdoors where there is direct 
       grade access. 
2.    At least one identified basement receptacle.
3.    All countertop receptacles within 6 feet of the kitchen sink.
4.    All 125V, single phase, 15 and 20 A receptacles in garages unless:
	a.    Not readily accessible.
	b.   Dedicated for a cord-and-plug-connected fixed appliance.
5.    All 120 V, single-phase, 15 and 20 A receptacles which are not part of permanent wiring (such as those
        used for temporary power during construction).

These code requirements are not retroactive so you do not have to do this to older houses, but they are 
required for all new construction.
You can add GFCI protection to your house and it's not difficult to do. They may be installed as breakers
or receptacles. The receptacle GFCI units are cheaper and can be installed in the bathroom, kitchen, 
outdoors, or in a basement. They may be connected so as to protect more than one receptacle on the 
same circuit. 
DIRECTIONS MUST BE FOLLOWED EXACTLY FOR THE PROTECTION TO WORK AS IT IS 
SUPPOSED TO, SO IF YOU ARE NOT FAMILIAR WITH ELECTRICAL WIRING, HAVE A 
LICENSED ELECTRICIAN DO THE WORK FOR YOU.

This information is from MODERN RESIDENTIAL WIRING,  ISBN 0-87006-902-0

Jerry O. Hemby
W1NRA