Around the house · First steps · about 5 minutes

Test and Reset a GFCI Outlet

A GFCI (ground-fault circuit interrupter) outlet is the kind with TEST and RESET buttons, usually found near water in kitchens, bathrooms, garages, and outdoors. It cuts the power in a split second when electricity starts leaking where it shouldn't, such as through water or a person. Testing it once a month tells you it still works, and knowing how to reset it can bring a 'dead' outlet back to life.

When to teach it: Watch from about 6, help from about 8, do it alone from about 10.

Test each GFCI once a month with a lamp plugged in.

You'll need

A small lamp or night-light that you know works
Paper and pencil (to note which outlets each GFCI controls)

Before you start

If the GFCI has tripped, unplug whatever was running on it and check the cord for fraying or other damage.

Step by step

Tick each step as you go if you like; ticks stay on this device.

Find your GFCIsLook for outlets with TEST and RESET buttons in bathrooms, the kitchen, the garage, the basement or crawl space, laundry and utility sinks, and outdoors. Some homes have GFCI breakers in the panel instead, with a TEST button on the breaker.
Plug in a lightPlug a lamp or night-light into the GFCI outlet and turn it on. If it doesn't light, press RESET first.
Press TESTPush the TEST button. The light should go out. On a GFCI breaker, pressing TEST should move the handle to the tripped position.
Press RESETPush RESET firmly. The light should come back on. For a GFCI breaker, reset the handle.
Notice what else went darkA GFCI outlet also protects the outlets wired after it on the same circuit. Next time you test, check which other outlets lose power and write them down.
Bring back a dead outletIf a regular outlet stops working, look for a tripped GFCI on the same circuit, which may be in another room. Unplug what was running, then press RESET.
Know when it failsIf the light stays on when you press TEST, or won't come back on after RESET, the GFCI is not doing its job. Have a qualified electrician fix or replace it.
Repeat every monthTest each GFCI once a month and after a power outage.

Physics

How it works: How a GFCI notices a leak

Electricity travels in a loop. Current flows out to your lamp on one wire and comes back on another. In a healthy circuit, the amount going out equals the amount coming back.

A GFCI keeps comparing those two amounts. If some current is missing on the way back, it must be leaking out another path, maybe through water or a person. When the difference reaches just a few thousandths of an amp, about 4 to 6 milliamps, the GFCI shuts off the power in less than a tenth of a second.

A milliamp is one-thousandth of an amp. That means a GFCI can notice a leak far smaller than the current a lamp uses, and act on it faster than you can blink.

leak = current out − current back; the GFCI trips when the leak reaches about 0.004 to 0.006 amps (4 to 6 milliamps)

Try it: Math warm-up: 1 amp = 1,000 milliamps. If a lamp uses 0.5 amps, how many milliamps is that? (500.) How many times bigger is that than a 5-milliamp leak? (100 times.)

Keep learning: Science

Teaching it to your kids

Make testing a first-of-the-month family routine.
Let your child press TEST and RESET while you both watch the lamp.
Draw a simple house map together showing which outlets go dark when each GFCI trips.

Tips

Use a lamp you can see from the outlet so you know right away when it goes off.
Test after every power outage too.
If a GFCI trips every time one certain appliance is plugged in, that appliance may be faulty. Stop using it.
For outdoor power tools and electric garden equipment, use portable GFCI protection.

Common mistakes

Mistake	Instead
Deciding an outlet is broken when it's really fed by a tripped GFCI somewhere else.	Check the GFCI outlets in nearby bathrooms, the kitchen, garage, basement, and outside, and press RESET.
Never testing because the outlet 'works fine'.	A GFCI can stop protecting you and still deliver power. In one CPSC survey, about a quarter of people who tested their GFCIs found one that wasn't working. Test monthly.
Pressing RESET over and over on a GFCI that keeps tripping.	Unplug everything on it. If it still trips, or you can't tell why, call an electrician.

Safe habits

Test GFCIs once a month.
If TEST doesn't cut the power, don't count on that outlet for protection until a qualified electrician fixes it.

When to call a pro

If the light stays on when you press TEST, the GFCI isn't working or isn't installed right. Have a qualified electrician correct it.
If RESET won't bring the power back, the GFCI needs to be replaced. Replacing it is wiring work, so have a qualified electrician do it.
If a GFCI keeps tripping, or you can't tell why it tripped, contact an electrician.

Sources

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