What Arc-Fault Circuit Interrupters Mean to Homebuilders
The technology employed in Arc-Fault Circuit Interrupters (AFCIs) may help prevent electrical fires in additon to saving lives and millions of dollars. Gerard Winstanley from the National Electrical Manufacturer’s Association gives us the run-down on what AFCIs are and how they can be used in the home.
There are few things more devastating to a homeowner than a fire.
Despite best efforts from manufacturers, installers and inspectors, home electrical problems cause an estimated 67,800 home fires and $868 million in property losses annually, according to the most recent data from the U.S. Fire Administration.
But there are steps builders can take to prevent electrical fires, which lead to an estimated 485 deaths and 2,300 injuries annually, according to the USFA. That includes using arc-fault circuit interrupters (AFCIs), which the U.S. Department of Housing and Urban Development listed as one of the many devices that can be used to prevent residential electrical fires.
Whereas conventional circuit breakers only respond to overloads and short circuits, they don't prevent arcing conditions that produce an erratic current flow. According to the National Electrical Manufacturers Association, arcs naturally occur in the operation of electrical devices such as motors and switches. An arc fault occurs when wiring insulation damages the arc. These can produce extreme heat and lead to fires.
"Arc faults can occur in two ways: a series arc would be a broken current-carrying path in a single conductor, while a parallel arc would be an arc between two conductors or between a conductor and ground. Parallel arcs generally involve more energy," says Gerard Winstanley, program manager for NEMA. "An AFCI utilizes advanced electronic technology to monitor the circuit for the presence of normal and dangerous arcing conditions. It will analyze ... an arcing event and determine if it is hazardous, in which case it will interrupt power to the line."
According to NEMA, the 2008 National Electrical Code is expanding requirements for AFCIs. NEMA estimates AFCI protection in circuit breakers could prevent 50 percent or more of the fires caused by problems in the electrical system. The 2008 edition of the code also takes safety a step further by requiring that all new home construction builders install combination AFCIs to all 15-amp and 20-amp branch circuits not only in bedrooms, but in additional living areas in new dwellings and in the lighting system.
It is important to note that AFCIs are not a panacea; it is possible for a high-voltage surge to damage the arc-detecting circuits of an AFCI. "This is a very rare occurrence, and in this case, the device may still function as a circuit breaker. The test button on the AFCI will confirm whether the arc detecting circuitry is still functioning," says Winstanley. "We recommend that the operation of all AFCIs is checked on a monthly basis."
AFCIs may also be tripped inadvertently, though this too is rare. According to NEMA, the majority of the "nuisance trip" issues are related to installation problems. Specific examples include
reversing neutral to ground wires, shared neutral wiring on single pole circuits, and ground wires touching neutral wires. These are arcs that a standard circuit breaker would not detect, but an AFCI would and then shut the circuit down immediately. "As contractors become more familiar with the installation and operation of AFCIs, these wiring errors, reports of nuisance tripping will decline," says Winstanley.
"AFCIs are a relatively new technology and manufacturers are investing great effort in their development. It is very likely we will see further developments in these products. The key issue is safety. There are many home safety options, but AFCIs are a technological leap forward that provides immediate preventative protection to the home's electrical system," says Winstanley.
He believes the expanded NEC requirement will have a significant impact on home safety and decrease the number of lives lost and injuries that occur in residential fires. "Homeowners deserve the safest home possible. This is especially important with new home construction, where safety needs to be the number one priority in the home building processes."