Do AFCI breakers protect existing knob-and-tube wiring systems?
An AFCI circuit breaker will trip and clear the circuit when a line-to-neutral arc occurs (often caused by the melting of the conductor insulation at loose terminals) within three to eight half-cycles, whereas a standard circuit breaker might not open for many hundreds of half-cycles. Note: If the AFCI is dual listed as a GFCI, the two wire receptacle can be replaced with three-wire receptacles and no equipment grounding conductor is required to be run to the receptacles [406.3(D)(3)]. Is it okay to replace a regular circuit breaker with an AFCI circuit breaker if there are GFCI receptacles on the circuit in question? Yes. The GFCI receptacle should not interfere with the AFCI protection circuitry. What type of arcs are the most common factors in electrical fires, and will today’s AFCI circuit breakers detect these faults? An AFCI is designed to detect and clear a line-to-neutral fault under conditions where a standard circuit breaker might not (3 to 8 cycles as compared to 600 half-cy
