An arc fault circuit interrupter (AFCI) is an advanced circuit breaker that, as a way to reduce electrical fire threats, breaks the circuit when it detects a dangerous electric arc in the circuit that it protects.
An AFCI is able to selectively distinguish between a harmless arc that is incidental to the normal operation of switches and plugs, versus a potentially dangerous arc that can occur, such as in a lamp cord with a broken conductor. An AFCI is designed to detect a wide range of arcing electrical faults that help reduce the electrical system from being an ignition source of a fire.
Despite the fact that AFCIs were introduced and written into electrical codes in the late 1990s (more on this later), several myths still surround AFCIs—myths often believed by homeowners, state legislators, building commissions, and even some electricians.
MYTH 1: AFCIs are not important when it comes to saving lives
"AFCIs are very important safety devices that have been proven time and again," said Ashley Bryant, senior product manager for Siemens. In fact, according to Bryant, www.afcisafety.org includes several success stories on how these breakers have found some very dangerous situations and saved people and property.
Arc faults are one of the leading causes of residential electrical fires. Through the 1990s, according to the U.S. Consumer Product Safety Commission (CPSC), an average of over 40,000 fires a year were attributed to home electrical wiring, resulting in over 350 deaths and over 1,400 injuries. The CPSC also reported that over 50 percent of these fires could have been prevented with the use of AFCIs.
"The www.afcsafety.org website also includes a UL report noting that the average time to get out of a house in the event of a fire was 17 minutes," she said. "These days, though, because of homes being larger, having more open floor plans and fewer drywall barriers, and furniture that catches fire easier, that is now down to three minutes."
In addition, the CPSC reports that electrical fires due to arcing tend to occur behind walls, making them more dangerous. That is, these fires can spread undetected more quickly, they can cause more damage than other fires, and they end up being twice as deadly as fires not occurring behind walls, since homeowners tend not be aware of the fires behind walls until it may be too late to escape.
MYTH 2: AFCI manufacturers are driving expanded code requirements for the installation of AFCI
"I find this myth common when I am talking with legislators, but it is important that the electrical industry understand the reality as well when they are talking with their state senators and building commissions," said Alan Manche, vice president, external affairs, for Schneider Electric.
[SB]The drive for the expanding code requirements are coming from third-party research.
"The Consumer Product Safety Commission and studies conducted by UL with regard to thousands of fires occurring in homes in late 1980s and early 1990s drove the need to address the causes of these fires," Manche said. "Arc fault protection became the solution that was recognized by the CPSC, UL, and others."
MYTH 3: AFCIs are only required by codes in a small number of rooms in residential homes
"The National Electrical Code has been expanding the reach of AFCIs beyond residential homes," said Jim Phillips, P.E. president of Brainfiller.com, and a contributing editor to ELECTRICAL CONTRACTOR magazine.
The first National Electrical Code (NEC) requirement for AFCIs was released in 1999, requiring them to be installed to protect the circuits feeding bedrooms in new homes. In 2008, and again in 2014, the NEC was expanded to require AFCIs to be installed on circuits to more and more rooms in homes, now covering virtually all rooms—bedrooms, family rooms, dining rooms, living rooms, sunrooms, kitchens, dens, home offices, hallways, recreation rooms, laundry rooms, and even closets.
In addition, in 2014, the NEC also began requiring the use of AFCIs in college dormitories. It has also expanded requirements to include hotel/motel rooms that offer permanent provisions for cooking.
MYTH 4: An AFCI only protects what is plugged into the specific defective outlet that triggers the electric arc
"An AFCI actually protects the entire circuit," said Rich Korthauer, vice president, final distribution business, for Schneider Electric. "This includes the electrical panel; the downstream wires that run through the walls; the outlets; the switches; all of the connections to those wires, outlets and switches; and anything that is plugged into any of those outlets and connected to switches on that circuit."
MYTH 5: A standard circuit breaker will provide just as much protection as an AFCI
Conventional circuit breakers only respond to overloads and short circuits. They do not protect against arcing conditions that produce erratic and often reduced current.
"A standard circuit breaker protects the insulation on a wire from an overload," Korthauer said. "It is not intended to identify bad arcs on circuits in the home. Of course, if you have a dead short, a standard circuit breaker is designed to trip and interrupt that condition."
MYTH 6: Most AFCI "trips" are the result of "nuisance tripping"
"I hear this myth a lot," Siemens' Bryant said. "People believe that certain arc fault breakers are defective because they frequently trip. People need to think of these not as 'nuisance tripping,' but rather as 'safety alerts.' The majority of the time, these breakers trip because they are supposed to. They are tripping due to some type of arcing event on the circuit."
This can especially be true with "stab" receptacles, where wires are spring-loaded into the backs of the receptacles, instead of wiring around screws, which provide firm connections. In many instances, according to Bryant, when homeowners jam plugs into spring-loaded receptacles or pull them out roughly, it jostles the receptacles, allowing the wires to come loose, which will cause the arc fault breakers to trip.
"Again, this is not 'nuisance tripping," she said. "It is a 'safety alert.'"
Update: An earlier version of this article incorrectly stated AFCIs had been around since the 1970s, but it's GFCIs that were introduced in the 1970s. AFCIs were introduced in the 1990s. We regret the error, and we have updated the article with this information.