Arc fault circuit interrupters — commonly called AFCIs or arc fault breakers — are one of the most important safety innovations in residential electrical systems in the past 30 years. Required by the National Electrical Code in most living areas of new construction since 2002, AFCIs prevent thousands of electrical fires every year. Here is everything you need to know about arc fault circuit breakers.
What Is an Arc Fault?
An arc fault is an unintended electrical discharge that occurs when electricity jumps across a gap between conductors. Unlike a short circuit — where two conductors touch directly — an arc fault involves electricity arcing through the air or through damaged insulation. This arc generates intense heat (up to 35,000°F) that can ignite nearby combustible materials and start a fire.
Arc faults can be caused by damaged wiring insulation, loose electrical connections, pinched or stapled wires, and aging wiring. They are particularly dangerous because they can occur in walls and ceilings where the heat is not immediately visible, allowing a fire to grow undetected.
How AFCI Breakers Work
Standard circuit breakers protect against overloads and short circuits by detecting excess current. But arc faults do not necessarily draw excess current — they can occur at normal operating current levels. This is why standard breakers cannot detect them.
AFCI breakers use sophisticated electronic circuitry to analyze the waveform of the electrical current flowing through the circuit. Arc faults produce a distinctive electrical signature — a pattern of current spikes and interruptions that the AFCI's microprocessor can recognize. When it detects this signature, it trips the circuit within milliseconds, before a fire can start.
Modern AFCI breakers are designed to distinguish between dangerous arc faults and normal arcing that occurs in everyday appliances like vacuum cleaners and light switches. This prevents nuisance tripping while still providing protection against genuinely dangerous arcs.
NEC Requirements for AFCI Breakers
The National Electrical Code has progressively expanded AFCI requirements over the years. As of the 2020 NEC (adopted by most states), AFCI protection is required in virtually all living spaces in new residential construction, including bedrooms, living rooms, dining rooms, kitchens, hallways, closets, and garages.
Many states have adopted the 2020 NEC or later versions, making AFCI breakers standard in most new home construction. Older homes are not required to retrofit AFCI breakers unless they are doing substantial electrical work, but many homeowners choose to upgrade for safety.
Major AFCI Breaker Brands
Square D AFCI Breakers include the QO120CAFIC (1-pole 20A combination AFCI) and the dual-function QO120PDFC (1-pole 20A AFCI/GFCI). Square D AFCI breakers are among the most widely used in new construction.
Siemens AFCI Breakers include the QA120AFC (1-pole 20A) and the dual-function QA120AFCPDF. Siemens AFCI breakers are compatible with Siemens and ITE load centers.
Eaton/Cutler-Hammer AFCI Breakers include the BRCAF120 (1-pole 20A combination AFCI) for BR panels and the CHCAF120 for CH panels. Eaton also offers dual-function AFCI/GFCI breakers.
GE AFCI Breakers include the THQL1120AFP2 (1-pole 20A) for GE load centers.
AFCI Breakers on the Secondary Market
AFCI breakers have strong secondary market value because they are required in new construction and renovation projects. A new AFCI breaker typically costs $35 to $60 at retail. Surplus or used AFCI breakers in good condition can sell for $15 to $40 each, making them attractive to contractors and homeowners looking to save on materials.
Electrical Breaker Buyers purchases AFCI arc fault circuit interrupters of all brands and configurations. Whether you have a box of surplus AFCI breakers from a completed project or a large lot from a distributor, we want to buy them. Call 951-733-6603 for a free quote.