GFCI and AFCI: what they do and where they go

GFCI and AFCI are two kinds of protection that an ordinary breaker does not give you. They sound alike, but they guard against different dangers. A GFCI protects people from electric shock. An AFCI protects the house from fires that start in the wiring.

What a GFCI does

GFCI stands for ground-fault circuit interrupter. It compares the current going out on one wire with the current coming back on the other. In a healthy circuit the two are equal. If some of the current is missing, it is leaking somewhere it should not go, possibly through a person. The GFCI notices a very small difference and cuts the power in a fraction of a second.

You know a GFCI outlet by its two buttons, marked TEST and RESET. The same protection can also be built into a breaker in the panel.

Where GFCI protection goes

GFCI protection belongs wherever electricity and water can meet. In homes that typically means:

• bathrooms
• kitchens, especially outlets that serve the counters
• garages and unfinished basements
• outdoor outlets
• laundry areas and places near a sink

One GFCI outlet can protect the regular outlets wired after it on the same circuit. That is why a dead outlet in one bathroom is sometimes fixed by pressing RESET in another bathroom or in the garage.

What an AFCI does

AFCI stands for arc-fault circuit interrupter. An arc is a spark that jumps across a gap: a cracked cord under a rug, a loose connection behind an outlet, a cable pinched by a nail. Arcs produce intense heat and can start a fire inside a wall without ever drawing enough current to trip a normal breaker.

An AFCI watches the pattern of the current for the signature of arcing and shuts the circuit off when it finds one. In most homes it is a breaker in the panel with a test button on it. AFCI outlets also exist.

Where AFCI protection goes

AFCI protection is aimed at the living spaces of a home: bedrooms, living rooms, hallways and similar rooms, where cords, lamps and electronics are plugged in every day. Some circuits need both kinds of protection, and dual-function breakers that combine GFCI and AFCI are made for that.

What applies to your house

Electrical codes have added GFCI and AFCI locations little by little over the years. What a particular house must have depends on when it was built, on the code in force when work was last done and on the kind of work being done now. Older homes often have less protection than a new one would, and replacing an outlet or extending a circuit can bring current rules into play.

I do not list the rules here, because they change and because your town’s wiring inspector has the final word. Ask me about your specific job, or check with the inspector.

What you can safely check yourself

• Test every GFCI. Plug in a lamp, press TEST and the lamp should go off. Press RESET and it should come back. Manufacturers recommend doing this every month.
• Map what each GFCI protects. Press TEST and walk around to see which other outlets lost power. Write it down for the next time something stops working.
• Test AFCI and GFCI breakers with the button on the breaker. The handle should move to the tripped position. Reset it by pushing it fully off and then on. Do this at a time when a short power cut to those rooms does not matter.
• Look at outdoor outlets. They should have a cover that closes over the outlet.

When to stop and call an electrician

• A GFCI will not reset, or the TEST button does nothing. GFCIs wear out, and one that does not trip on test is not protecting anyone.
• A GFCI or AFCI trips again and again. The device is reporting a real leak or a real arc until proven otherwise. Unplug what is on the circuit and see my guide on why a breaker keeps tripping.
• An outlet near water has no GFCI protection at all.
• An outlet or its cover is warm, cracked, scorched or loose in the wall.
• You feel a tingle when you touch an appliance, a faucet or a metal cover. Stop using it and switch that circuit off at the panel.

Replacing regular outlets with GFCIs and adding the right breakers is routine work for me. See outlets and switches or ask for a free quote.