May, 2003
Technical Jargon:
Inoperable GFCI (or GFI) Outlet
“Technical Jargon” is a forum used to provide more information on terms commonly seen in U.S. Inspect reports.
Ground-fault circuit-interrupter receptacles (GFCI or GFI) are safety devices that protect you from electrical shock in the event of a short
circuit in an appliance, extension cord, or outlet itself. These outlets are commonly found in bathrooms, kitchens, garages and outdoors, and are easily recognized by the small “test” and “reset” buttons placed in the center of the outlet.
These GFCI receptacles have the ability to measure the electrical amperage in both the hot and neutral wires comprising the electrical circuit. If the GFCI detects more than a difference of .005 amps on the hot wire (likely caused by a ground-fault), it will “trip” (divert the flow of electricity) to ground (i.e. the ground—literally the soil beneath your feet). A ground-fault is caused when a person or object provides a path of lesser-resistance to ground. For example, if a hair dryer falls into a bathtub, the GFCI outlet will trip and divert the electricity into the Ground, rather than into the water.
If the outlet containing a GFCI does not “trip” when tested, it is considered inoperable.
GFCI protection should not be confused with grounding. Grounding provides a release for a built up electrical charge in an object. An electrical panel box is a good example of this. By grounding the panel box, any excess electrical charge in the panel box itself is released to ground instead of shocking a person coming into contact with it.
A few basic rules of electricity should help explain this:
-
Rule #1. Electricity will always take the path of least resistance.
-
Rule #2. Electricity requires a complete circuit (path from source to ground) to flow.
-
Rule #3. Electricity is always trying to reach equilibrium. This means that electricity, like water, if it meets no resistance, will always spread itself out until it can no longer do so (i.e. reaches an insignificant level).
-
Rule #4. Electricity is always trying to get to ground. Ground has little resistance and allows electricity to expand as far as it can go.
Electricity is controlled by giving it only one path to ground. That path is through the service cable entering your house, through a series of wires to your appliances and lights, and finally to the ground (through the neutral wire). This is not electricity’s path of choice because of the resistance it meets along the way. When a GFCI “trips” to ground, it switches the flow of the electrical current to the ground wire instead of the neutral wire. Doing this, it is providing electricity with a path of lesser resistance to ground (see Rule #1) and effectively cuts power to the appliance you’re using, or maybe even you.
Grounding may provide some protection against electrical shock, but does not defend well against the risk of electrocution. A non-GFCI circuit relies on the circuit breaker in the panel to trip when a ground-fault occurs.
A circuit breaker will require a minimum draw of 15 amps before the breaker
trips (20 amps on a 20 amp breaker, etc.). Electrocution has been known to occur with exposure to an electrical charge as little as 1 amp. A GFCI outlet will trip at .005 amps. A charge of .005 amps may still give you a nasty shock, but it’s a lot better than the alternative.
Article 210.8 in the National Electric Code (NEC) outlines the requirements
for the use of GFCI devices) in new home construction.
Click here
for more information on GFCI outlets and other electrical components.
Contributed by Justin Gore
Quality Assurance Supervisor
U.S. Inspect, LLC
Other stories in this month's report:
Visit the Advisory
Report Archives
