Bare Necessities: Every Home Requires Arcing-Fault Protection

Electrical Panel Image Credit: iStock / FSTOP123
Image Credit: iStock / FSTOP123

A friend who had just purchased a 10-year-old house asked me whether he and his wife should spend money to have his electrical contractor install all the newest safety devices. We reviewed the existing equipment so I could help him determine what different safety devices he might need and their approximate cost. I told him to ask his EC’s recommendation as well. The EC would better answer the cost questions. Two opinions are better than one, after all.

I determined by the approximate age of the home that none of the overcurrent devices nor the electrical circuits in his service panelboard were arc-fault circuit- interrupter-protected circuits. Based on the newest edition of the National Electrical Code (NEC), I also determined many of the circuits that should have been ground-fault circuit-interrupter (GFCI) protected were not.

I told the homeowner we should focus on those two types of protective devices initially, since they were critical for his family’s basic protection. He was very familiar with GFCI protection but unfamiliar with arc-fault circuit-interrupters (AFCI).

I provided a basic explanation of the history and purpose of the AFCI protective devices as I’ll do here as well. These devices were first introduced in the 1996 NEC as circuit breakers designed to interrupt an arcing fault; however, the electrical industry wasn’t ready for mass testing and production until the 1999 NEC in which these breakers were inserted as protection for bedroom outlets. The first AFCI circuit breakers were called branch/feeder AFCIs and were designed to recognize an arcing fault where the peak value of the arc was a minimum of 75 amperes (A). These devices dealt primarily with parallel arcing faults. An example of a parallel arcing fault is a nonmetallic-sheathed cable (NM cable or commonly called Romex as named by Rome Cable) with a staple hammered too tightly across the cable assembly causing damage to the internal conductors resulting in a short from the hot conductor to the neutral conductor within the cable assembly. These branch/feeder AFCIs did not provide series-arcing-fault protection, only protection for parallel-arcing faults. Series arcing faults commonly occur when an extension cord has damage to the strands in one of the conductors within the cable assembly and starts to arc in a series path across the individual conductor. Both series and parallel-arcing faults can result in a fire within the home.

I then explained that a newly designed AFCI circuit breaker was already in the testing stage and would be available on the market within the next six months to a year. This new AFCI circuit breaker was called a combination-type AFCI and would cover both parallel and series-arc faults. He then asked me for my opinion on what circuits to protect and whether to move in and wait for the new combination-type AFCIs before installing the AFCIs. I told him I would install AFCI circuit breakers on all the 15- and 20A outlets and device circuits in the panel.

To answer his question about moving into the home and waiting for the combination-type AFCI devices to go on the market, I advised him not to wait. The branch/feeder AFCI devices would provide his family with protection for whatever length of time necessary; he could replace the devices with the new combination-type AFCI devices later. The cost of the branch/feeder AFCI devices would be good insurance for his family for the brief wait, and they would be priceless if a parallel-arcing fault occurred during that time.

The last issue I addressed was one his EC would probably also cover—many outlet circuits have been wired as multiwire branch circuits, especially in older homes where two hots share a neutral. Since AFCI circuits require a separate neutral to operate properly, any existing outlet circuit that is a multiwire branch circuit may require a two-pole AFCI for proper operation.

The cost of AFCI and GFCI protection on circuits to prevent fires and electrocutions is the least expensive insurance you can provide for your home and your family. The ability to sleep at night without worry of an electrical arcing fire in your house is the best money anyone can spend.

About the Author

Mark C. Ode

Fire/Life Safety, Residential and Code Contributor

Mark C. Ode is a lead engineering associate for Energy & Power Technologies at Underwriters Laboratories Inc. and can be reached at 919.949.2576 and Mark.C.Ode@ul.com.

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