6.4 AFCI Protection and Receptacle Requirements

What an Arc Fault Is

A parallel arc occurs between conductors or between a conductor and ground — a nail through a cable, a crushed cord. It draws high current and a conventional breaker may or may not clear it, depending on impedance.

A series arc occurs along a single conductor at a break — a loose terminal screw, a broken strand, a worn cord. Because the load is still in series with the arc, the current stays at or below normal load current, so a conventional overcurrent device never sees a problem. A series arc at a loose backstab connection can burn for months at 5 amperes.

An AFCI uses signature analysis of the current waveform to distinguish arcing from normal switching and motor operation.

Where AFCIs Are Required — 210.12

210.12(A) Dwelling Units. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, or similar rooms or areas shall be protected by any of the means described in 210.12(A)(1) through (6).

The list is easier to invert: the rooms not listed are bathrooms, garages, unfinished basements, crawl spaces, and outdoors. Those areas are typically covered by GFCI requirements instead.

210.12(B) Dormitory Units. Same requirement for dormitory unit bedrooms, living rooms, hallways, closets, bathrooms, and similar rooms.

210.12(C) Guest Rooms and Guest Suites. Same requirement in guest rooms and guest suites of hotels and motels.

210.12(D) Branch Circuit Extensions or Modifications — Dwelling Units, Dormitory Units, and Guest Rooms and Guest Suites. Where branch-circuit wiring is modified, replaced, or extended in any of the areas specified in 210.12(A), (B), or (C), the branch circuit shall be protected by one of the following:

1. A listed combination-type AFCI located at the origin of the branch circuit; or
2. A listed outlet branch-circuit type AFCI located at the first receptacle outlet of the existing branch circuit.

There is an exception for extensions not more than 6 feet in length where no outlets or devices are added other than splicing devices.

210.12(A) Methods. The six permitted methods include a listed combination-type AFCI at the origin; a listed branch/feeder AFCI at the origin combined with a listed outlet branch-circuit AFCI at the first outlet; and several arrangements using listed supplemental arc protection breakers or listed system combination AFCIs with specified conductor types and lengths — for example RMC, IMC, EMT, Type MC, or steel-armored Type AC cable meeting 250.118 with metal outlet and junction boxes, and a limited home-run length.

Dual-Function Devices

A dual-function breaker or receptacle provides both AFCI and GFCI protection in one device. Where both are required — a dwelling kitchen countertop circuit, for example, requires GFCI under 210.8(A)(6) and AFCI under 210.12(A) — one dual-function device satisfies both.

Article 406 — Receptacles

Tamper-Resistant Receptacles — 406.12

All nonlocking-type 15- and 20-ampere, 125- and 250-volt receptacles in the following shall be listed tamper resistant:

1. Dwelling units, in the areas specified in 210.52 plus additional areas;
2. Guest rooms and guest suites of hotels and motels;
3. Child care facilities;
4. Preschools and elementary education facilities;
5. Business offices, corridors, waiting rooms and similar areas in clinics, medical and dental offices, and outpatient facilities;
6. Subset of assembly occupancies including gymnasiums, skating rinks, and auditoriums;
7. Dormitory units;
8. Assisted living facilities.

406.12 Exceptions cover receptacles located more than 5.5 feet above the floor; those that are part of a luminaire or appliance; a single or duplex receptacle for two appliances located within dedicated space for each appliance that in normal use is not easily moved; and nongrounding receptacles used for replacements as permitted in 406.4(D)(2)(a).

Weather-Resistant Receptacles and Covers — 406.9

406.9(A) Damp Locations. A receptacle installed outdoors in a location protected from the weather or in other damp locations shall have an enclosure for the receptacle that is weatherproof when the receptacle is covered — that is, an attachment plug cap is not inserted and the receptacle covers are closed.

406.9(B)(1) Wet Locations. A 15- or 20-ampere, 125- or 250-volt receptacle installed in a wet location shall have an enclosure that is weatherproof whether or not the attachment plug cap is inserted — an in-use or bubble cover. All 15- and 20-ampere, 125- and 250-volt nonlocking receptacles in a wet location shall be listed weather resistant type.

406.9(C) Bathtub and Shower Space. Receptacles shall not be installed within or directly over a bathtub or shower stall.

406.9(E) prohibits receptacles from being installed in a face-up position in countertops or similar work surfaces unless listed for the application, and 406.5(E)/(F) address floor and seating-area receptacles.

Replacing Receptacles — 406.4(D)

This section governs work in existing buildings and is a frequent exam topic.

406.4(D)(1) Grounding-Type Receptacles. Where a grounding means exists in the receptacle enclosure or an equipment grounding conductor is installed, grounding-type receptacles shall be used and connected to the equipment grounding conductor.

406.4(D)(2) Non-Grounding-Type Receptacles. Where attachment to an equipment grounding conductor does not exist in the receptacle enclosure, the installation shall comply with one of:

• (a) A non-grounding-type receptacle shall be permitted to be replaced with another non-grounding-type receptacle;
• (b) A GFCI-type receptacle shall be permitted, and shall be marked "No Equipment Ground"; an equipment grounding conductor shall not be connected between such receptacles;
• (c) A grounding-type receptacle shall be permitted where supplied through a GFCI, and shall be marked "GFCI Protected" and "No Equipment Ground".

406.4(D)(3) Ground-Fault Circuit Interrupters. GFCI protection shall be provided where replacements are made at receptacle outlets that are required to be so protected elsewhere in this Code — meaning a replacement in a location now covered by 210.8 must be GFCI protected, even though the original installation predates the requirement.

406.4(D)(4) Arc-Fault Circuit-Interrupter Protection. Where a receptacle outlet is supplied by a branch circuit that requires arc-fault protection as specified elsewhere in the Code, a replacement receptacle at this outlet shall be one of: a listed outlet branch-circuit type AFCI receptacle; a receptacle protected by a listed outlet branch-circuit type AFCI receptacle; or a receptacle protected by a listed combination-type AFCI circuit breaker.

406.4(D)(5) Tamper-Resistant Receptacles. Listed tamper-resistant receptacles shall be provided where replacements are made at receptacle outlets required to be tamper resistant elsewhere in the Code.

406.4(D)(6) Weather-Resistant Receptacles. Weather-resistant receptacles shall be provided where replacements are made at receptacle outlets required to be so protected elsewhere in the Code.

The pattern across (D)(3) through (D)(6) is consistent: replacement triggers current requirements. Swapping a device in an existing house pulls that outlet up to today's Code even though the rest of the circuit is grandfathered.

Article 404 — Switches, in Brief

404.2(C) requires a grounded circuit conductor for switch loops at switch locations controlling lighting loads, with limited exceptions where the wiring is accessible for future extension or where a raceway or cable assembly is present. The purpose is to supply electronic switches and dimmers that need a neutral.

404.9(B) requires snap switch faceplates to provide a means to ground metal faceplates, and metal faceplates to be grounded. 404.8(A) requires switch handles to be located so the centre of the grip of the operating handle, when in its highest position, is not more than 6 feet 7 inches (2.0 m) above the floor or working platform.

404.4 addresses damp and wet locations, and 404.14 covers the rating and use of snap switches, including the requirement that AC general-use snap switches be used only on AC circuits.