GFCI Protection for Personnel

A GFCI compares current leaving on the hot conductor with current returning on the neutral. If they differ by more than about 5 milliamps, some current is finding another path — often a person — and the device opens in under 1/30th of a second.

First required for swimming-pool equipment in 1971, GFCI coverage has expanded almost every code cycle: outdoor receptacles (1973), bathrooms (1975), garages (1978), kitchens (1987), and by the 2020 edition nearly every 125–250 V receptacle in dwelling kitchens, laundry and outdoor areas.

When it applies

Think of GFCI protection as required anywhere water and electricity can meet. In a home that means bathrooms, kitchens serving countertop receptacles, garages, unfinished basements, crawl spaces, laundry areas, outdoors, and near pools or sinks. The device watches the current going out on the hot and coming back on the neutral. If even a tiny amount leaks away, say through someone standing on a wet floor, it opens the circuit in a fraction of a second.

Common mistakes

• Assuming an outlet is protected because it looks new. A standard receptacle in a bathroom without a GFCI upstream is not protected.
• Forgetting that one GFCI receptacle can protect the outlets downstream, so you do not always need a special device at every box.
• Wiring the load and line terminals backward, which leaves the protection dead while everything still powers up.

In the field

I always press the test button after installing one. If it does not trip and reset cleanly, I do not leave it, no matter how tidy the wiring looks.