GFCI outlets: where you need them and why they trip

Published 2026-02-27 · 6 min read

What a GFCI actually does

It compares the current going out with the current coming back. If they differ by a tiny amount, roughly the difference that would occur if current were passing through a person to ground, it opens the circuit in a fraction of a second.

It does not protect against overload, and it does not require a ground wire to work. That second point is useful in older houses: a GFCI can provide protection on an ungrounded circuit where a standard three-prong outlet would be misleading.

Where they belong

Kitchens, bathrooms, garages, laundry areas, unfinished basements, crawl spaces, outdoors, and anywhere near a sink, pool or spa. In Florida, we would add dock circuits, outdoor kitchens and anything on a lanai regardless of whether it is strictly required.

Protection can come from a GFCI receptacle or from a GFCI breaker in the panel. The breaker protects everything downstream, which is tidier but makes the trip location less obvious.

Testing, and why nobody does it

Press test. It should trip. Press reset. It should restore. Doing this monthly is the recommendation; doing it twice a year is realistic and far better than never.

A GFCI that does not trip when tested has failed and is protecting nothing. This is common in units more than ten years old, particularly outdoors.

Why yours keeps tripping

Moisture is the leading cause in Florida, and it is seasonal. Outdoor GFCIs that trip after every afternoon storm are usually telling you water has got into a fitting, a cover is cracked, or a cord end is sitting in a puddle.

Long circuits can also produce enough natural leakage to bring a sensitive device close to its threshold. So can certain appliances, especially older motors and anything with a heating element.

If it trips with everything unplugged, the fault is in the fixed wiring. That one needs tracing rather than guessing.

The dead outlets nobody can explain

One of the most common calls we take: half the outlets in a house stop working, no breaker has tripped, and nothing makes sense. The cause is almost always a tripped GFCI upstream protecting a long run, frequently one hidden in a garage, behind a freezer, or in a bathroom nobody uses.

Worth knowing where yours are before you need them.