Appendix L. GROUND FAULT CIRCUIT INTERRUPTORS (GFCIs)

GFCIs are designed to protect a person from electric shock when he or she simultaneously contacts a “live” (usually 120V) wire or part and a grounded object. The GFCI works by sensing a difference between the supply and return currents. When the difference exceeds 5mA—indicating that current is flowing to ground (through the person)—the device switches off.

Although the GFCI is an effective safety device, it is not a guarantee against shock in every situation. The GFCI does not protect against a line-to-neutral or a line-to-line shock. Also, if GFCI-protected equipment contains transformers, a ground fault (shock) on the secondary side of the transformer may not trip the GFCI.

GFCIs are normally installed as either circuit breakers or receptacles. In either case, the GFCI may be wired to protect multiple receptacles. Individual GFCI plug-in adapters are also available.

LBNL requires GFCI protection for the following conditions:

1. Any 120V convenience outlet located within 2 m (6 ft) of an open water source. This does not include emergency eyewash showers or fire sprinklers.


2. Any 120V convenience outlet located outdoors.


3. Any 120V convenience outlet located within 2 m (6 ft) of a “massive ground.” (A massive ground is a large area of metal, wet earth, or other highly conductive surface that enhances the conductivity to ground of the person touching it.)


4. Any extension cord providing power for construction activities.


5. Any resistance heating equipment not having a metal covering, such as heating tapes.

It is LBNL policy to implement the GFCI requirements in conditions 1, 2, and 3 above on a phase-in basis. Any new or remodel construction will include the GFCIs as specified. Existing locations should be prioritized for retrofitting according to relative risk. For example, locations near sinks with heavy electrical use should be retrofitted immediately with GFCI protection.

GFCIs must be tested before each use, but at least at 30-day intervals. Push the “test” button and observe if the “reset” button pops out and the receptacle turns off. If this does not happen, the GFCI is not functional and must be replaced.

CAUTION: Testing of a GFCI will disconnect all receptacles protected by the GFCI. Before testing, determine which receptacles are protected. Verify that the interruption of power will not adversely affect other activities.