What is the difference between a GFCI and an AFCI breaker?

A GFCI trips on 4 to 6 milliamps of current leaking to ground and protects people from shock. An AFCI trips on the waveform signature of an arcing fault and protects against fire. They detect different conditions and do not substitute for each other.

Can one breaker do both?

Yes. Dual function AFCI/GFCI breakers provide both protections in one device and are commonly used on dwelling kitchen and laundry circuits where NEC 210.8 and 210.12 both apply.

Where does NEC 2023 require AFCI protection?

NEC 210.12 requires AFCI on 120 volt single phase 15 and 20 amp branch circuits supplying outlets or devices in most dwelling living areas, including bedrooms, kitchens, living rooms, hallways, closets and laundry areas.

What is the difference between GFCI and AFCI breakers?

A GFCI protects people, an AFCI protects the building. A ground fault circuit interrupter measures the difference between the current leaving on the ungrounded conductor and the current returning on the grounded conductor, and opens the circuit when that imbalance reaches 4 to 6 milliamps. An arc fault circuit interrupter watches the current waveform for the electrical signature of an arcing fault and opens the circuit when it sees that pattern. They detect completely different things and are not interchangeable.

How each one senses a fault

The GFCI uses a current transformer around both circuit conductors. In a healthy circuit the outgoing and returning currents cancel and the transformer sees nothing. When some of the current finds another path to ground, through a person, a wet appliance or a damaged cable, the imbalance produces a signal and the device trips. UL 943 sets the Class A trip threshold at 4 to 6 milliamps, well below the roughly 30 milliamps where current across the chest becomes life threatening.

The AFCI uses electronics that sample the current waveform and look for the erratic, high frequency, chopped pattern that a series or parallel arc produces. A loose terminal, a nail through a cable or a chewed cord all produce arcs that draw far less current than the breaker rating, so a standard breaker never trips while the arc keeps making heat. That is the fire risk the AFCI addresses.

Where NEC 2023 requires each

Section 210.8(A) requires GFCI protection for 125 volt through 250 volt receptacles in dwelling bathrooms, garages and accessory buildings, outdoors, crawl spaces, basements, kitchens, sinks, boathouses, bathtubs and shower areas, laundry areas and indoor damp or wet locations. Section 210.8(B) covers other than dwelling occupancies, 210.8(D) covers specific appliances including dishwashers and ranges, and 210.8(F) covers outdoor outlets serving equipment such as condensing units.

Section 210.12 requires AFCI protection for all 120 volt single phase 15 and 20 amp branch circuits supplying outlets or devices in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas and similar rooms. AFCI is a branch circuit requirement covering everything on the circuit, while GFCI is often an outlet level requirement.

Where both apply

A dwelling kitchen small appliance circuit needs AFCI for the branch circuit and GFCI for the countertop receptacles, and a laundry circuit is in the same position. Dual function breakers provide both in one device and are usually cheaper than a separate AFCI breaker plus GFCI receptacles. Note that GFCI protection is also required for certain 240 volt loads now, which a receptacle level GFCI cannot cover, so the breaker is the only option there.

Field takeaway

GFCI is shock protection at 4 to 6 milliamps of leakage. AFCI is fire protection against arcing. Many dwelling circuits need both, and a dual function breaker is the simplest way to get there.