The 2005 Code cycle was a busy time for members of Code-Making Panel 2, which oversees the requirements for Art. 210, 215, and 220, including the rules for AFCIs. The panel received more than 50 proposals for change to 210.12, ranging from clarifying the definition of an AFCI to deleting requirements for the device altogether. In the end, CMP-2 kept the section in place and accepted some of the less drastic proposals.

Background on arcing faults

As defined by the NEC, AFCIs are intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.

Arcing faults are classified as either series or parallel. A series fault may occur when one of the current-carrying conductors in series with the load is broken or incomplete. Extreme flexing in an appliance cord can cause conductors to open and arc under load. Series arcing occurs when light switches are opened or closed, and when disconnects are open and closed. A cord-and-plug connected appliance pulled from a receptacle will also cause series arcing.

Parallel arcing faults occur when an unintentional conducing path is formed between two conductors of opposite polarity, such as line-to-ground or line-to-line. Because they're limited only by the available fault current of the circuit, parallel arcing faults may involve dangerously high currents that generate high temperatures and could potentially ignite surrounding combustible materials.

Any number of factors can contribute to creating arcing faults. Conductor or cord insulation can be pinched or pierced and lead to the condition. Nails and screws can damage conductors and cords, which can also lead to arcing. Old, cracked insulation caused by heat, bending stress, or loose or improperly made connections can also cause arcing. Rodents have also been known to chew through insulation and create the potential for the problem.

AFCIs and the 2005 NEC

Numerous proposals and comments to expand the required use of AFCIs in dwelling areas other than the bedrooms were submitted during the 2005 Code cycle. Perhaps the most important change to the section was an accepted proposal to require the exclusive use of combination type AFCIs starting Jan. 1, 2008. This new AFCI combines the protection of branch/feeder circuits with increased sensitivity as well as added protection for cord-and-plug connected equipment (Sidebar below). Allowing this requirement to become effective in 2008 will give manufacturers time to produce the devices in sufficient quantity for the expected demand.

Another topic debated at all levels is the requirement for fire alarm and burglar alarm systems to be connected to AFCI-protected circuits in the bedrooms of dwelling units. (“All levels” means during construction as debated by electrical installers and inspectors; discussions and debates by building code officials, electrical inspectors and other authorities; and NFPA code panels, including interested parties submitting and/or reviewing proposals and comments). As stated in 210.12(B), all branch circuits and all outlets in dwelling unit bedrooms shall be AFCI protected. A smoke detector connected to a nominal 120V circuit requires AFCI protection. How do 760.21 and 760.41 relate to the smoke detectors in dwelling unit bedrooms? It's clear that both sections prohibit the power source of fire alarm circuits to be connected to AFCI-protected circuits, as well as GFCIs.

If a smoke detector is part of a fire alarm circuit, which is part of a fire alarm system, it isn't permitted to be connected to a circuit protected by an AFCI or GFCI. If it's neither part of a fire alarm circuit nor part a fire alarm system, it must be connected to AFCI-protected branch circuits for dwelling unit bedrooms.

It's important to check the requirements of NFPA 72. The document defines a fire alarm system as a system or portion of a combination system that consists of components and circuits arranged to monitor and annunciate the status of fire alarm or supervisory signal-initiating devices and to initiate the appropriate response to those signals.

Proposals that didn't make the cut

One proposal that was ultimately voted down suggested expanding the requirements for AFCIs to include all living areas of dwelling units. It was rejected during both the proposal and comment stage by CMP-2. The issue was raised again at the annual NFPA meeting in May 2004, when a similar proposal to expand use of AFCIs to all living areas of dwelling units was submitted as a floor action, but a floor vote rejected it as well. Neither CMP-2 nor the Technical Correlating Committee was in favor of the proposal. Considering all proposals, comments, and associated information, the NFPA Standards Council decided not to incorporate the proposed change during this cycle.

A topic vigorously debated was the proposal to exempt AFCI protection to dedicated circuits that supply power to life support systems. This proposal was accepted during the proposal stage and rejected during the comment stage, due to concerns that arcing faults on any circuit pose a hazard.

It should be noted that the National Association of State Fire Marshals hoped AFCIs could be required in lodging units, rooming houses, day care centers, educational buildings (K-12), and residential board and care homes for the elderly. The association also supported the addition of requirements for AFCI in electrical upgrades for existing homes. The proposal was also turned down, but there is a strong possibility it could be raised — and accepted — again in future Code cycles.

The NEC continues to expand the requirements for AFCIs. New technological advances and improvements are changing the way that AFCIs are evaluated by recognized testing labs and the way in which they're manufactured. Look for expanded requirements for AFCI protection in dwelling units, and possibly in commercial and industrial applications in future Code cycles.

Owen is the owner and president of National Code Seminars in Pelham, Ala.

Sidebar: AFCI Types and Product Categories as Referenced by Underwriters Laboratories

The UL product category control numbers (CCNs) for AFCIs are as follows. AVYI is the main category that all AFCI sub-categories fall under. It contains the general information pertinent to all AFCI categories and sub-categories. AVYI defines AFCIs as devices intended to mitigate the effects of arcing faults by functioning to de-energize the circuit when an arc fault is detected.

The following types of AFCIs are intended for permanent installation in a branch circuit (or feeder where noted).

AVZQ (branch/feeder type) — A device intended to be installed at the origin of a branch circuit or feeder, such as at a panelboard. It's intended to protect the branch-circuit wiring, feeder wiring, or both, against unwanted effects of arcing. This device also provides limited protection to branch circuit extension wiring. It may be a circuit breaker type device or a device in its own enclosure mounted at or near a panelboard.

AWAH (combination type) — An AFCI that complies with the requirements for both branch/feeder and outlet circuit AFCIs. It's intended to protect downstream branch-circuit wiring and cord sets and power-supply cords.

AWBZ (outlet branch-circuit type) — A device intended to be installed as the first outlet in a branch circuit. It's intended to protect downstream branch-circuit wiring, cord sets, and power-supply cords against the unwanted effects of arcing. This device also provides protection to upstream branch wiring. It's intended to be provided with or without receptacle outlets.

AWCG (outlet circuit type) — A device intended to be installed at a branch-circuit outlet, such as at an outlet box. It's intended to protect cord sets and power supply cords connected to it (when provided with receptacle outlets) against the unwanted effects of arcing. This device may provide feed-through protection of the cord sets and power-supply cords connected to downstream receptacles.

The following types of AFCIs are portable devices that may be incorporated into in appliances or utilization equipment.

AWAY (cord type) — A plug-in device intended to be connected to a receptacle outlet. It's intended to protect the power supply cord connected to it against the unwanted effects of arcing. The cord may be integral to the device. The device has no additional outlets.

AWDO (portable type) — A plug-in device intended to be connected to a receptacle outlet and provided with one or more outlets. It's intended to protect connected cord sets and power supply cords against the unwanted effects of arcing.

ELGN (leakage-current detection and interruption) — This is a device provided in power supply cords or cord sets that senses leakage current flowing between or from the integral cord conductor and interrupts the circuits at a predetermined level of leakage current.