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Arc Fault Circuit Interrupter (AFCI)
AFCIs are newly developed electrical devices designed to protect against fires caused by arcing faults in home electrical wiring. Annually, over 40,000 fires are attributed to home electrical wiring. Arcing faults are one of the major causes of these fires. When unwanted arcing occurs, it generates high temperatures that can ignite nearby combustibles such as wood, paper and carpets.
Arcing faults often occur in damaged or deteriorated wires and cords. Some causes of damaged and deteriorated wiring include puncturing of wire insulation from picture hanging or cable staples, poorly installed outlets or switches, cords caught in doors or under furniture, furniture pushed against plugs in an outlet, natural aging and cord exposure to heat vents and sunlight.
The AFCI should not be confused with a GFCI or Ground Fault Circuit Interrupter. The GFCI is designed to protect people from severe or fatal electric shocks while the AFCI protects against fires caused by arcing faults. The GFCI can also protect against some electrical fires by detecting arcing and other faults to ground but cannot detect hazardous across-the-line arcing faults that can cause fires.
How the AFCI Works
Conventional circuit breakers only respond to overloads and short circuits; so they do not protect against arcing conditions that produce erratic current flow. An AFCI is selective in that normal arcs do not cause it to trip. The AFCI circuitry continuously monitors current flow through the AFCI. AFCI’s use unique current sensing circuitry to discriminate between normal and unwanted arcing conditions. Once an unwanted arcing condition is detected, the control circuitry in the AFCI trips the internal contacts, thus de-energizing the circuit and reducing the potential for a fire to occur.
Where AFCIs are Needed
Presently, AFCI’s are designed into conventional circuit breakers combining traditional overload and short-circuit protection with arc fault protection. As of January 2002 the National Electric Code, which is the model code for electrical wiring, requires AFCI’s for receptacle outlets in bedrooms and as of January 2008, the NEC revised this requirement to all livable areas. In homes equipped with conventional circuit breakers rather than fuses, an AFCI circuit breaker may be installed in the panel box in place of the conventional circuit breaker. Homes with fuses are limited to either receptacle or portable type AFCI’s or AFCI circuit breakers can be added in separate panel boxes next to the fuse panel box.