A GFCI is a receptacle or circuit breaker and is used to increase safety in areas that are prone to the risk of electric shock. They will trip when current from the GFCI 120 V side does not return through the neutral side. The GFCI measures the current from the 120 V, through a load, and back to the neutral. This current needs to be the same. If current from the 120 V does not return to the neutral (i.e. goes to ground instead), the GFCI will trip (power will be turned off coming out of the GFCI). It takes a mismatch of about 5 mA of current (5 milliamps or .005 A) to trip a GFCI.
GFCI receptacles can provide protection to standard receptacles connected to the load side of the GFCI.
When the test button is pushed or if the GFCI trips, power is shut off to the GFCI and protected receptacles. Pushing the reset button should restore power to the GFCI and receptacles connected to the GFCI load. If a GFCI has no power going to it (the GFCI line) then the test and reset button will not work. See Troubleshoot GFCI Receptacles.
GFCIs should be tested about once a month. If it doesn’t trip when testing (but it has power to the line side), then it will need to be replaced.
GFCI line side*
GFCI load side*
Yes, a GFCI will work properly if there is no ground. A plug tester with a GFCI test button will not trip the GFCI because the tester leaks a small amount of current from 120 V to ground. The GFCI test button is used for testing.
A GFCI adapter can be used on a standard receptacle. Plug the adapter into a receptacle and anything you plug into the adapter will have GFCI protection.
GFCI breakers are an option for providing GFCI protection to the entire circuit. To test the breaker, press the test button and the breaker should trip. To reset, push the handle away from the center of the panel, then push the handle toward the center of the panel.
If the breaker does not trip when the test button is pressed, either the breaker is bad or there is no power to the breaker.
Ground connection is not shown
*Line and load side locations can differ between GFCI receptacle manufacturers
Ground Fault Circuit Interrupters (GFCIs)