An AFCI is a receptacle or circuit breaker that is used to open a circuit if an abnormal arc is detected. Small arc conditions exist in a normal circuit (light switches, motor starting or stopping). An AFCI ignores these normal arcs, but will detect the abnormal ones, using advanced technology.
Arc faults and flashes are usually caused by loose connections and/or damaged wire, and are the greatest cause of electrical fires. They happen when anything connected to a line phase (like a line wire) is in the process of touching anything that is connected to a different line phase, neutral or ground. An arc actually happens before contact is made when the current jumps a tiny gap.
AFCI receptacles can provide protection to standard receptacles that are connected to the load side of the AFCI.
AFCI Location Requirements
The 1999 NEC required AFCI protections for receptacle outlets in dwelling unit bedrooms.
The 2002 NEC required AFCI protections for all outlets in dwelling unit bedrooms (receptacle, lighting, smoke alarms, etc).
The 2008 NEC required AFCI protections for all outlets in all dwelling unit rooms that are not required to be GFCI protected (all rooms except bathrooms, kitchens, garages, etc).
Testing and Resetting an AFCI
When the test button is pushed or if the AFCI trips, power is shut off to the AFCI and protected receptacles. Pushing the reset button should restore power to the AFCI and receptacles connected to the AFCI load. If a AFCI has no power going to it (the AFCI line side) then the test and reset button will not work.
AFCIs should be tested about once a month. If it doesn’t trip when testing (but it has power to the line side), then it will need to be replaced.
AFCI receptacles and circuit breakers are wired exactly the same as GFCIs. Please see GFCI Wiring for info on AFCI wiring.