The National Electrical Code (NEC) requires ground fault circuit interrupt (GFCI) outlets in new construction for countertop and exterior outlets, as well as any outlet within 6 feet of a water basin. Dedicated or inaccessible outlets such as those for dishwashers, disposals and refrigerators do not require GFCI protection. If the test button on the GFCI does not trip the reset button on the outlet, you must inspect and repair the outlet and connections, or replace the bad GFCI.
Line and Load
GFCI outlets have connections marked "Line" and "Load" on their back or sides. If the line and load are installed backward, the GFCI will not function properly. The line connection is for the hot black and white wires, in the same sheath, that feed power into the outlet. The load wires are the black and white wires, in the same sheath, that continue on to the next outlet in the circuit protected by the GFCI.
Identifying the Line Side Wires
To determine which wires are the line, set a multimeter on ohms scale at the lowest setting. Look inside the box where the wires enter; you may see two sets of wires with a black and white wire in the same sheath. With the power off, touch the red lead from the multimeter to one of the white wires in the box. Touch the black lead from the multimeter to the bare ground wire. The multimeter will show extremely low or no resistance between one of the white wires and ground, known as "line side neutral" because the line side neutral wire is tied to the ground bus in the breaker panel. The black wire, in the same sheath with the white, is the line side hot.
Proper GFCI Installation
The connections on the GFCI outlet marked "Line" connect to the line hot and line neutral wires. The white line wire connects to the silver screw marked "Line," and the hot black wire connects to the brass colored screw marked "Line." The load wires are the remaining black and white left in the box once you have connected the line side. The white load wire connects to the silver screw marked "Load," and the black load hot wire connects to the brass screw marked "Load." The bare ground wire connects to the green ground screw on the GFCI.
Ground Wire Shorts
If the bare ground wire touches any of the screws on the side of the outlet, it won't work properly. Take special care to push the bare ground wire into the back of the electrical box and away from all the screw connections.
Finding a Problem
If your GFCI is connected right but still does not test and reset properly, disconnect the load connections and test the GFCI again. If the GFCI still doesn't test correctly after you have disconnected the load side connections, the GFCI outlet has gone bad and requires replacement. If the outlet tests correctly after you have disconnected the load side connections, the problem lies in another outlet box. A ground wire may be touching the screws on one of the other outlets fed by the GFCI's load side. Check all the outlets that are not working when the GFCI is not powered; look for shorts between the ground wires and the screws on the outlets.
- Photo Credit Jupiterimages/Photos.com/Getty Images
How to Wire a GFCI Outlet With Pigtails
A ground-fault circuit interrupting (GFCI) outlet uses a current sensor and a circuit breaker to disconnect a dangerous electrical circuit. The electrical...
How to Replace a GFCI Outlet With Issues
A GFCI outlet that fails or displays other performance issues may require replacement using a GCFI tester, a screwdriver and a pair...
Installation Guidelines for GFCI Outlets
A GFCI, or ground fault circuit interrupter, is a special outlet designed with a small circuit breaker inside and its own reset...