3.2 GFCI & AFCI Protection Requirements

GFCI & AFCI Protection Requirements

Ordinary thermal-magnetic breakers protect conductors. They cannot sense the few milliamperes that kill a person or the low-current arcing that starts a fire. Ground-fault circuit interrupters (GFCIs, 210.8) protect people from shock. Arc-fault circuit interrupters (AFCIs, 210.12) protect buildings from fire. The exam tests which locations need which device, and the 2023 edition changed several of those lists.

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How a GFCI Works

A GFCI compares the current on the ungrounded conductor with the current returning on the grounded conductor. Normally $I_{\text{hot}} - I_{\text{neutral}} = 0$. If current leaks to ground through a person or damaged insulation, the difference trips the device.

Class A trip characteristics

The Article 100 definition of a GFCI carries an informational note: Class A devices trip when ground-fault current is 6 mA or higher and do not trip below 4 mA.

Trip time follows an inverse-time curve from UL 943, $t = (20/I)^{1.43}$, where $t$ is in seconds and $I$ is in milliamperes:

The familiar "25 milliseconds" figure applies to large fault currents, not to the 5-mA region.

Exam trap: GFCI versus GFPE. Ground-fault protection of equipment (GFPE) is not personnel protection. For example, 230.95 requires GFPE on each service disconnect rated 1000 amperes or more on solidly grounded wye services of more than 150 volts to ground, such as 480Y/277 volts. The setting may not exceed 1200 amperes, with a maximum 1-second delay for ground faults of 3000 amperes or more. GFPE protects equipment from burning down. It will not save a person.

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Dwelling-Unit GFCI Locations (2023 NEC 210.8(A))

The 2023 code requires GFCI protection for all 125-volt through 250-volt receptacles on single-phase branch circuits rated 150 volts or less to ground in these dwelling locations:

1. Bathrooms
2. Garages, and accessory buildings with a floor at or below grade not intended as habitable rooms
3. Outdoors (with an exception for receptacles that are not readily accessible and that supply snow-melting, deicing, or pipeline and vessel heating equipment)
4. Crawl spaces at or below grade level
5. Basements
6. Kitchens, meaning all receptacles in the kitchen. The 2020 wording covered only receptacles serving countertops.
7. Areas with a sink and permanent provisions for food preparation, beverage preparation, or cooking (new in 2023)
8. Sinks, where receptacles are within 6 feet (1.8 m) of the top inside edge of the bowl
9. Boathouses
10. Bathtubs or shower stalls, where receptacles are within 6 feet of the outside edge
11. Laundry areas
12. Indoor damp and wet locations

Measuring the 6 feet. Measure the shortest path the cord of an appliance plugged into the receptacle would follow. The path may not pierce a floor, wall, ceiling, or fixed barrier, or pass through a door, doorway, or window.

The GFCI device itself must be installed in a readily accessible location.

Nebraska field note

Neb. Rev. Stat. § 81-2104(5) keeps the 2017 NEC text for 210.8(A), 210.8(A)(3), and 210.8(A)(5).

• In 2017, the dwelling list applied to 125-volt, single-phase, 15- and 20-ampere receptacles only, not to 250-volt receptacles.
• The 2017 basement item covered only unfinished portions of basements not intended as habitable rooms.

Answer PSI questions from the code book. Expect the state inspector to apply the statute.

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GFCI for Specific Appliances and Outdoor Outlets

• 210.8(D) Specific appliances (2023). The appliance list moved into 210.8 from 422.5(A). It covers outlets, so it reaches hardwired equipment as well as cord-and-plug equipment. It applies to appliances rated 150 volts or less to ground and 60 amperes or less, single- or 3-phase:
  • automotive vacuum machines;
  • drinking-water coolers and bottle-fill stations;
  • high-pressure spray washers;
  • tire inflation machines;
  • vending machines;
  • sump pumps;
  • dishwashers;
  • electric ranges;
  • wall-mounted ovens;
  • counter-mounted cooking units;
  • clothes dryers; and
  • microwave ovens.
• 210.8(E) Equipment requiring servicing. Receptacles installed under 210.63 for servicing HVAC and other equipment must be GFCI-protected.
• 210.8(F) Outdoor outlets at dwellings. Outdoor outlets (not just receptacles) on single-phase circuits of 150 volts or less to ground and 50 amperes or less need GFCI protection. This includes outlets in garages with floors at or below grade, accessory buildings, and boathouses. Lighting outlets are excepted.

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Other-Than-Dwelling GFCI Locations (210.8(B))

In other occupancies, the rule covers these receptacles:

• single-phase receptacles on circuits of 150 volts or less to ground and 50 amperes or less; and
• 3-phase receptacles on circuits of 150 volts or less to ground and 100 amperes or less.

Locations include:

• bathrooms;
• kitchens, or areas with a sink and permanent provisions for food preparation or cooking;
• rooftops;
• outdoors;
• receptacles within 6 feet of a sink;
• indoor damp or wet locations;
• locker rooms with showers;
• garages, accessory buildings, service bays, and similar areas (not vehicle showrooms);
• crawl spaces at or below grade;
• unfinished basement areas;
• laundry areas (2023);
• receptacles within 6 feet of a bathtub or shower stall (2023); and
• receptacles within 6 feet of aquariums, bait wells, and similar open aquatic vessels (2023).

Agricultural buildings have their own GFCI rule in 547.28, covered in Chapter 7.

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Arc-Fault Circuit Interrupters (210.12)

AFCIs detect the signatures of two kinds of arcing:

• Series arcs: a loose or broken conductor, such as a backstabbed receptacle connection. Current is limited by the load, so a breaker never sees an overload, but the arc heats wood framing.
• Parallel arcs: line-to-neutral or line-to-ground arcing through damaged insulation. Current is too low and too erratic to trip the breaker's magnetic element.

Permitted AFCI methods (210.12(A)(1)–(6))

1. A listed combination-type AFCI breaker protecting the whole branch circuit (the usual method).
2. A branch/feeder-type AFCI breaker plus an outlet branch-circuit (OBC) AFCI at the first outlet.
3. A supplemental arc-protection breaker plus an OBC AFCI at the first outlet. The home run must be continuous and no longer than 50 feet of 14 AWG or 70 feet of 12 AWG, and the first outlet box must be marked.
4. An OBC AFCI at the first outlet with a branch-circuit device that is listed as a system combination with it.
5. An OBC AFCI at the first outlet where the home run is RMC, IMC, EMT, Type MC, or steel-armored Type AC cable with metal boxes.
6. An OBC AFCI at the first outlet where the home run is encased in at least 2 inches of concrete.

Dwelling units (210.12(B))

AFCI protection is required on all 120-volt, single-phase, 10-, 15-, and 20-ampere branch circuits supplying outlets or devices in these dwelling rooms and areas:

• kitchens;
• family rooms, dining rooms, living rooms, and parlors;
• libraries and dens;
• bedrooms and sunrooms;
• recreation rooms;
• closets and hallways;
• laundry areas; and
• similar rooms or areas.

Circuits that are extended or modified must also be protected, with limited exceptions for short extensions.

Exam trap: what is not on the dwelling AFCI list. Bathrooms, garages, outdoor circuits, and unfinished basements used only for storage are not listed. Bathrooms and garages need GFCI protection instead. A finished basement used as a recreation room is a listed area.

Other occupancies

• 210.12(C) Dormitory units: bedrooms, living rooms, hallways, closets, bathrooms, and similar rooms.
• 210.12(D) Other occupancies: guest rooms and guest suites of hotels and motels; patient sleeping rooms in nursing homes and limited-care facilities; and sleeping quarters in fire, police, ambulance, rescue, and ranger stations.

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GFCI vs. AFCI Comparison