Home & Garden Columns

About the House: An Introduction to the AFCI Circuit Breakers

By Matt Cantor
Friday February 09, 2007

Breakers of the space-age: In 2003 there were over 73,000 electrical fires and nearly 600 resulting deaths, not to mention about a billion dollars in property loss. Most of these fires were caused by electrical “arcing.”  

Now what IS arcing and why does it cause fires? 

When I think of arcing, I always think of those early science fiction movies where an electrical current can be seen bridging across a pair of metal prongs held upright (they call this a “Jacob’s ladder”). The arc climbs up and disappears, replaced by a new shorter one that then also climbs up and out of sight. “It’s ALIVE!” screams Gene Wilder. Yes, that’s an arc, although that particular one is under control and doing what we wish it to do. There are also tiny arcs occurring inside of motors all the time as the little copper brushes sweep across the magnetic core, causing the whole thing to rotate. Motors seen in the dark usually issue some flecks of orange light. Get down on the kitchen floor and look beneath the fridge at night and you might see what I’m talking about. Now, all arcing is not good. In fact, most arcing isn’t good at all and the majority of electrical fires are caused it.  

When two wires are separated by a tiny space, the power attempts to jump the gap. This gap creates resistance and this creates heat. This effect can built upon itself (heat melts metal creating more of a gap and more resistance and so on) until wires begin to melt and nearby combustibles, such as insulation or wood, catch fire. These gaps can be caused by a cord that has been worn from repeated bending or from prolonged heat. A cord or wire may have been stepped on or punctured in use or a pair of wires in a “wire-nut” (these are used to join wires in most houses) may have pulled just a teensy bit apart.  

Any of these conditions can begin to create heat and lead to a fire. If you notice that you have an outlet that glows or gets hot, it has likely developed an “arc-fault,” A cord may also feel hot in one place and the same might well be true. There are lots of ways and places that this can occur and for years, the only thing we could do was to rely upon our wits and sluggish old style breakers and fuses to eventually notice the increased heat on the circuit. Sadly, these devices are not good at detecting arc-faults and fires continued to break out. But wait, computer technology is here to save you, Mr & Mrs. Ludd. 

Just as electrical engineering has learned to “see” and “hear” for robots, cars and so many other devices in our brave new electronic world, circuit breakers, too, have begun to think in a very exciting new way. They have learned to hear the sounds of arcing, which I think is incredibly cool.  

Arcing has a particular sound or wave-form, if you speak oscilloscope. The amazing thing is that these devices can ignore the arcing of a motor but attend to the wave form of a wire that has begun to spark and overheat. If they sense this particular kind of arcing going on, they kill the circuit, preventing a deadly fire. This new breaker, the Arc-Fault Circuit Interrupter or AFCI is new and not in widespread use … yet. These are not required in older houses that have electrical repairs and is only required for the bedrooms in new houses. Even this requirement is only true where city inspectors are using the 2002 code book and amazingly enough, many cities are 7-10 years behind on code enforcement.  

One might also ask why we’re not using this life-saving technology on all of our circuits and one should! The truth is, it’s being discussed in those gray rooms that you and I are never invited into. Might be a security clearance thing. Nevertheless, those who write the codes are doing what they can to push this technology forward and get it into homes across the U.S. and Canada. I have no idea where the EU stands and can find nothing on AFCIs in the U.K. either. 

The good news is that you can go forth and procure these lovelies for your home and put them in as a means of decreasing your fire risk. There are, however, some things you need to know about them since nothing is ever as sweet as it seems from across the street through the shop window. 

Older homes tend to have lots of tiny/minor arc-faults and installation of an AFCI breaker on your bedroom circuit might result in a breaker that trips when energized and will not reset. I’ve seen it myself. You can then set about to find the tiny arc-faults, which is certainly a worthy, if not valiant attempt but you may find it beyond your purse size or the skills of your electrician to complete such a task. Nonetheless, I think it’s worthwhile.  

Be aware that old, worn electrical cords and certain appliances are more likely to be the cause of an arc-fault than your old knob and tube wiring. An old outlet may be the cause or perhaps an old poorly wired lamp or switch. In short, it’s easier to put these in a new house but worthwhile to try to use in an old one. I think one could even argue that this is good way to challenge the most problematic portions of an older electrical system. 

Sometimes an inspection client will jokingly tell me that they don’t want to hear what’s wrong with the house but if I challenge them, they will typically smile and say that they really DO want to know. I think they just want me to be gentle, which, of course, I always am (he smiled to himself). I think this is a similar issue. It’s better to find out and now there’s a really good way to do it. By the way, I’d very much recommend using our new friend the AFCI in all parts of the house. There’s no reason not to use them in bathrooms, kitchens or garages as well, although you may find out that your toaster oven needs to be tossed out. 

AFCIs cost about 100 bucks a piece so they’re not cheap but I’m sure they’ll be coming down in price, just as the GFCI has. (That’s the Ground-Fault Circuit Interrupter, the AFCIs shock preventing cousin, seen in baths across America.)  

So installation of AFCIs, including the troubleshooting they can induce, may cost hundred or even thousands of dollars. For now, you’ll have the be the judge of their value since you’re not likely to have them foisted upon your older home. If you buy new, you may be buying them any way. 

So, whether you retrofit them into your older home or receive them with your new one, please do take advantage of these space-age sentinels and you won’t have to keep the home-fires burning. 

 

Got a question about home repairs and inspections? Send them to Matt Cantor at mgcantor@pacbell.net.