GFCI Outlets: Where They Go and Why They Trip
The two buttons in the middle of a GFCI outlet, one marked test and one marked reset, are among the most useful safety devices in a house. They exist for one purpose: to cut power in an instant when electricity is flowing somewhere it should not, such as through a person standing near water.
If you have ever pressed reset on an outlet in your garage or bathroom, you have met one. Here is what it is doing, where you should expect to find it, and what is behind the trips that drive people crazy.
What a GFCI actually does
GFCI stands for ground-fault circuit interrupter. Normally the current leaving the outlet on the hot wire comes back on the neutral wire in nearly the same amount. A GFCI constantly compares the two. If a small amount goes missing, which means it is leaking out through another path such as a wet hand, a damaged cord or a faulty tool, the GFCI shuts off the circuit almost instantly.
It is not the same as a breaker. A breaker protects the wiring from too much current. A GFCI protects people from shock, and it reacts to leakage far too small for a breaker to notice.
Where they are generally required
The National Electrical Code generally calls for GFCI protection on receptacles in the places where electricity and water, or damp ground, are most likely to meet. In a house, those typically include bathrooms, kitchens (at least countertop receptacles), garages, outdoor outlets, crawl spaces, unfinished basements, laundry areas and receptacles near sinks. Newer code editions have steadily widened the list.
Exact requirements depend on which code edition your city or county has adopted, and on when your house was built, since older homes are generally not required to be upgraded unless work is being done. If you are unsure about a particular room, ask an electrician rather than guessing.
GFCI outlet, GFCI breaker, or protection from another outlet
Protection can come in three ways. A GFCI receptacle protects itself and can also protect other regular outlets wired downstream of it, which is why a dead outlet in the garage may be fixed by pressing reset on a GFCI somewhere else, perhaps in a bathroom or at the outside wall. A GFCI breaker in the panel protects the whole circuit. And a portable GFCI plug or adapter protects whatever is plugged into it.
The sneaky one is the downstream arrangement. If an outlet has no buttons and no power, hunt for the GFCI that feeds it before assuming something is broken.
Testing: once a month
Manufacturers generally tell you to test GFCIs about once a month. Plug in something that is on, like a lamp, press the test button and the power should drop out and the lamp go dark. Then press reset and the power should return. If the button does not trip it, or reset will not hold, the device has worn out and should be replaced.
A GFCI that no longer trips is more dangerous than no GFCI at all, because it looks protective but is not.
Why a GFCI keeps tripping
Frequent trips usually have an explanation, and the trip is often the device doing exactly what it should.
- Moisture in the outlet box or a cover that no longer seals, which is very common outdoors
- A damaged appliance, tool or cord leaking current to ground
- Older appliances such as refrigerators, freezers or well-worn tools sharing the protected circuit
- A worn-out GFCI that has become overly sensitive after years of service
- Too many outlets chained downstream of one GFCI, with leakage from each device adding up
- Heavy or moisture-prone use, like pressure washers and outdoor holiday lights after a rain
What you can try and what to leave alone
Unplug everything on the protected outlets, reset, then plug items back in one at a time to find the troublemaker. Dry out any wet covers and avoid running cords through standing water. If the GFCI trips with nothing plugged in, or the cause is not obvious, the problem is likely inside the wiring or the device and calls for a licensed electrician.
Replacing a GFCI sounds like a quick swap, but the line and load wiring matter. Connected wrong, it can leave downstream outlets unprotected or not powered. Where an older home has two-prong outlets with no ground wire, the code generally permits a GFCI to provide protection, but it should be labeled correctly and done properly. It is a straightforward job for an electrician.
A GFCI will not reset, trips with nothing plugged in, feels hot, buzzes or sparks, or the outlet looks scorched or water-damaged. Stop using it and have a licensed electrician inspect the circuit.