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Arc Fault Detection: Your Questions Answered

Nov 1, 2007 12:00 PM, By Gerard Winstanley, National Electrical Manufacturers Association

As with any change in the required protection for electrical systems, there have been many deliberations both for and against arc fault protection being part of the NEC

Find more articles on Arc Flash/Arc Fault

The National Electrical Code (NEC) requirements for arc fault circuit interrupters (AFCIs) have become more stringent with each passing Code cycle, stirring up much discussion and debate among builders, electrical contractors, and other professionals involved in home construction. While these devices were previously only required to protect the bedroom, the 2008 NEC now requires the technology to be installed in additional areas of the home, including dining rooms, living rooms, and other habitable areas.

Many prominent experts in the electrical and homebuilding communities believe this expanded requirement will have a significant positive impact on homeowner safety (see the Figure), reducing the number of lives lost and injuries that occur in home electrical fires. According to a 2006 report from the United States Fire Administration, approximately 67,800 fires occur annually due to problems in a home's electrical system, resulting in approximately 485 deaths, more than 2,300 injuries, and more than $868 million in residential property loss.

Not all experts and end-users agree with this line of thinking, however. Some have argued that the cost of the AFCI is higher than standard circuit breakers and, as such, cost too much to be in balance with the increased protection. Others have argued that because it is a relatively new type of protection device, the AFCI does not have the history on which to base a decision about whether to support it or not. As with most new technology developments, questions and concerns covering a variety of issues exist. Since AFCI inclusion in the NEC, questions have arisen, ranging from cost and availability to nuisance tripping and the experience level among those responsible for AFCI installation.

This article will explore some of these important questions and attempt to clear up some misconceptions that may be circulating in the industry.

Cost vs. benefit

One of the more popular questions regarding AFCIs and the expanded Code requirements for their installation is whether the additional cost is worth the benefits the technology provides to the homeowner.

While AFCIs have been a part of the NEC since the 1999 edition (see The Evolution to Develop Arc Fault Technology below), some states and municipalities have removed the AFCI requirement from the Code during their own Code-adoption process, citing cost as a key factor. On the flip side, Vermont has been requiring AFCIs since 2000. In fact, the state already requires AFCIs to be installed in the rooms outlined in the 2008 NEC.

While there is an added expense associated with equipping a home with AFCIs instead of standard circuit breakers, safety advocacy groups and other AFCI supporters believe that the benefits significantly outweigh the cost (see United Front below), arguing that the cost is relatively insignificant when measured against the number of deaths and injuries that may be prevented.

A quick survey conducted by the National Electrical Manufacturers Association (NEMA), Rosslyn, Va., of hardware stores and “do-it-yourself” home centers found AFCIs priced in the $30 to $35 range, and standard circuit breakers costing between $2 and $4. As the average number of circuits in a home requiring AFCIs is 12, this equates to an approximate cost increase of $372 to $396, approximately one-fifth of 1% of the national average cost of a 2,500-square-foot home. (Note: These figures do not include installation costs.)

To trip or not to trip

Another argument against the use of AFCIs is over the issue of nuisance tripping. However, consistent findings throughout the AFCI implementation process have revealed that the majority of the nuisance trip issues are related to installation problems — specifically the wiring practices of some electricians. Specific examples include reversing neutral and ground wires, shared neutral wiring on single-pole circuits, and ground wires touching neutral wires.

Electrical contractors have been very active in providing information about these types of wiring problems. Many contractors indicate that the initial installation issues associated with wiring errors have disappeared as the installers become more familiar with the installation and operation of AFCIs.

One common misconception is that AFCIs are not tested for nuisance tripping on real-world products and circuits. Between all of the AFCI manufacturers' products, there are now millions of operating hours with AFCIs (both in field tests and in new and existing homes) that showcase the successful performance of AFCIs in protecting new and old appliances. These tests include the new combination AFCI.

Manufacturers contend that the same concern existed in the 1999 NEC, when the branch/feeder AFCI was first introduced. Louder voices were heard when GFCI provisions were expanded to commercial kitchen outlets in the 2002 NEC. Those claims proved to be unfounded, and manufacturers are confident that combination AFCIs will prove to be successful when properly installed.

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