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.

Conventional circuit breakers only respond to overloads and short circuits; so they don’t protect against arcing conditions that produce erratic current flow.

The AFCI circuitry continuously monitors current flow through the AFCI.  AFCIs 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.

Presently, AFCIs are designed into conventional circuit breakers combining traditional overload and short-circuit protection with arc fault protection.  It’s important to note that AFCIs are designed to mitigate the effects of arcing faults but cannot eliminate them completely.  In some cases, the initial arc may cause ignition prior to detection and circuit interruption by the AFCI.

The 2008 edition of the National Electrical Code requires that AFCIs be installed in all new dwelling units.  Arc Fault breakers are not required in kitchens, bathrooms, unfinished basements, garages and outdoors.  In many cases arc fault breakers can’t be retrofitted in older homes.  They are only required for new circuits.

The AFCI costs about ten times the amount of a standard circuit breaker.