Arc Fault Circuit Interrupters.
First of all what the heck are they?
According to Square D, a leading manufacturer and innovator of electrical equipment, “Combination AFCI circuit breakers provide an added dimension of safety for homeowners by sensing and responding to both parallel and series arcing incidents. Series arcing is often associated with damaged devices or cord sets. A series arc is an arcing incident across a break in a conductor. A common example is a cut across one of the two wires in a lamp cord, with a dangerous arc forming in the gap. Combination AFCI circuit breakers detect the arcing condition and turn off the circuit, thus providing the enhanced protection.”
In the early days of these breakers, there were some reported problems with “nuisance” tripping and they only protected against “Parallel faults.” An example of a parallel fault would be like when you crush an extension cord by running it through a window and the “parallel” wires start to arc from one to the other.
Initially these breakers were required in most jurisdictions in bedrooms—because they had to start somewhere and it was calculated that bedrooms are where most house electrical fires start.
In 2002 the code required that all 120 volt “outlets” in the room be protected. To many people—even experienced electricians—an “outlet” was taken to mean only the “receptacles” (places to plug things in). To the National Electrical Code, an “outlet” is any place where a device is connected whether it is a receptacle, switch, smoke alarm/detector, or the fan in a hydronic heater.
As of the 2008 revision of the NEC (National Electrical Code) ARC Fault breakers are required to be the “combination” type that also detect “series” type faults. A series fault is more like a loose connection or a break in just one of the conductors that a spark might have to jump across to complete the circuit. As one can imagine this is an AWESOME improvement. Getting the older type breakers to trip in relation to a parallel arc is more difficult than one might think and series type arcing conditions are actually more common.
These combination type AFCI devices are a great way to add a layer of protection to older ungrounded type wiring systems like Knob & Tube wiring. Knob & Tube wiring is very prone to series type arcs.
I had a client tell me that their ARC Fault breaker kept tripping every time they used the vacuum cleaner so they took the breaker out and replaced it with a regular breaker! They didn’t realize that this was not nuisance tripping—-it was an indication that there was a problem with the vacuum cleaner. Contrary to popular believe, and the skepticism of some electricians, these devices have become very reliable and are a great improvement to overall fire safety in the home—especially the newer combination type breakers.
If your home has the older type AFCI devices it would be a considerable improvement to upgrade them to the newer Combination Type devices.
In many jurisdictions the 2014 NEC also requires that almost ALL 120 volt circuits in the home be AFCI protected–not just the bedroom circuits like it used to be starting in 2002.
Currently all 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets 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.
The cost of these things is coming down every day and the difference in cost between doing all the circuits in an average home and doing just the bedrooms would be about $300.00-$400.00 dollars—-hardly a deal breaker in my opinion.
All in all, these are great safety devices and many electrical panels can be upgraded to include these breakers to improve electrical safety. Other panels might require upgrading or the addition of sub-panels to accommodate space requirements.
How much of a safety issue it is might only be determined when someone dies.
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Charles Buell, Seattle Home Inspector
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AFCI, GFCI — what’s the difference? And if you’re in an early 1970s house like mine with GFCI receptacles only in the bathroom and the living room (because electronics were plugged in there?), does upgrading mean putting in new receptacles in all the other places or can something be done at the circuit breaker box?
Daniela, typically GFCI’s in most homes are located at the receptacles where they are needed and provide protection against electrical shock—or faults to ground. AFCI’s protect against arcing conditions that could result in a fire. AFCI’s are located in the electrical panel and GFCI’s can be on the circuits that are AFCI protected.
I like your reference to the use of AFCIs for protection in home wired with knob and tube wiring. I find quite a few in my area, and am also looking for ways to educate my clients on mitigating the safety issues associated with older wiring.
Greg, thanks. While of course K&T should be upgraded, installing AFCI’s on the old circuits when possible is a good idea.
Charles, thanks for the good info. I have another question re: our 85 year old church with K&T wiring. Will AFCI offer any benefit against wire overheating and thus causing a fire that way? We are about to have $10K of electrical upgrade work.
Dick, the newer Combination type AFCI’s do indeed add a layer of protection for the kinds of issues common with K&T and well worth the expense for these circuits until they can eventually be upgraded.