GFCI

A ground-fault circuit interrupter (GFCI) is an electrical safety device designed to protect people from electric shock. It monitors the current flowing in a circuit and detects small imbalances between the hot and neutral conductors. If leakage current to ground is detected, the GFCI quickly interrupts power to the circuit, typically within a fraction of a second.

GFCIs work by comparing the current on the live and neutral conductors. Under normal operation, the currents are equal. If current leaks to ground—such as through a person who touches a live surface—the difference is detected and the device trips. Most GFCIs trip at leakage levels around five milliamps and are designed to shut off within 40 milliseconds, minimizing the risk of serious shock. They may employ a residual current device (RCD) principle, implemented in outlets, breakers, or portable units.

There are several forms of GFCI protection. A GFCI receptacle provides protection at a specific outlet and can protect downstream outlets on the same circuit. A GFCI circuit breaker provides protection for all outlets on a circuit. Portable GFCIs offer temporary protection for cord-and-appliance use in areas without fixed GFCI protection. GFCIs are commonly installed in wet or damp locations such as bathrooms, kitchens, outdoor outlets, garages, basements, and laundry areas.

GFCIs are mandated or recommended by electrical codes in many jurisdictions for certain locations. Regular testing is advised—using the built-in test button—to verify operation. They do not protect against all electrical hazards and do not replace other safety measures such as proper wiring, insulation, or AFCIs for arc faults.