One is shock protection for people. The other is fire protection for the building. They are not interchangeable, and the code lists for both have grown every cycle.
They look alike in the panel and they are not interchangeable. Knowing what each device actually senses is what keeps you from installing the wrong one.
A ground-fault circuit interrupter compares the current going out on the ungrounded conductor with the current coming back on the grounded conductor. If some of it is leaving the circuit by another path — through a person, through wet conduit, through a failed appliance — the device opens. A Class A GFCI, the type used for personnel protection, is designed to trip at roughly 6 milliamps and to hold below about 4 milliamps. That is a threshold set for the human body, not for the wiring.
An arc-fault circuit interrupter watches the current waveform for the electrical signature of an arc: a damaged cord, a loose terminal screw, a staple driven through insulation, a nail through a wall cavity. Those faults can burn without ever drawing enough current to trip a conventional breaker. The AFCI is looking for ignition risk in the wiring, not for current leaving the circuit.
The consequence is simple. A GFCI will not see a series arc in a lamp cord, because nothing is leaving the circuit. An AFCI will not save someone standing in a wet basement holding a faulted tool. Where the code calls for both, you install a dual-function device or combine a breaker with a downstream receptacle — you do not pick one and call it covered.
Both requirements have expanded in every recent code cycle, and California amends the NEC on top of that. Treat the following as orientation and confirm the specifics in the edition your permit falls under.
| Device | Where it is generally required in dwellings |
|---|---|
| GFCI — NEC 210.8 | Bathrooms, kitchens, garages and accessory buildings, outdoors, crawl spaces, unfinished basements, laundry areas, boathouses, and receptacles located near sinks — historically those within six feet of the top inside edge of the sink bowl, with the measurement language refined across cycles. Additional subsections cover specific outlets such as dishwashers and outdoor HVAC equipment. |
| AFCI — NEC 210.12 | 15- and 20-amp, 120-volt branch circuits supplying outlets and devices in dwelling-unit living areas: bedrooms, living and family rooms, dining rooms, dens, libraries, sunrooms, recreation rooms, closets, hallways, and laundry areas, plus similar rooms. The list has grown with each cycle; read it rather than reciting it. |
Two changes worth knowing about because they surprise people on inspection. Recent NEC editions extended GFCI protection beyond ordinary 125-volt receptacles to certain higher-voltage receptacles, which is why ranges and dryers now come up in the conversation. And AFCI protection generally follows the circuit when you extend or modify wiring in a covered area, not just when you build new — see NEC 210.12 and the receptacle-replacement rules in 406.4(D).
Non-dwelling occupancies have their own GFCI list, and it is longer than most people expect. Do not assume a commercial tenant improvement is exempt.
An AFCI or GFCI breaker needs the circuit neutral landed on the breaker, with the breaker's own pigtail on the panel neutral bar. Leave the circuit neutral on the bar and it will trip immediately, every time.
A multiwire branch circuit split across two single-pole devices will not hold. Use a two-pole device listed for it, or separate the neutrals.
A pinched conductor in a device box, or a neutral and ground twisted together at a fixture, gives the sensor exactly the imbalance it is built to find. Ring out the circuit before swapping hardware.
Motors, some LED drivers, and worn appliance cords produce real leakage or real arcing signatures. A device that trips on one appliance and holds on everything else is usually reporting the truth.
We keep standard, GFCI, AFCI, and dual-function breakers on the shelf alongside GFCI receptacles, weather-resistant devices, in-use covers, and boxes, and the wire and cable to go with them. Not sure what a legacy panel accepts? Send us a photo of the panel label and we will cross-reference it the same day.
Reference only. This page is general reference information, not a substitute for the currently adopted code or the ruling of the authority having jurisdiction. California adopts the NEC as the California Electrical Code (Title 24, Part 3) with state amendments, and your city or county may amend it further. Requirements change from one code cycle to the next — verify every value against the edition in force for your permit, and confirm the details with your inspector before you buy material or energize anything. Ora Electric Lighting & Supply is a wholesale distributor. We sell materials. We do not perform electrical work, and we do not provide design or engineering services.
Send a photo of the panel label. We will cross-reference it and quote the same day.