What is an AFCI?

If you bought a new home recently, had new electrical lines ran and/or failed an inspection due to “AFCI’s”, you probably are wondering “what the heck is an AFCI, and why is it so much more costly then a regular breaker?” Well, I am here to help. I have created a general overview of the device, how it works, and why they are so “important.” Some may consider AFCIs a nuisance; however, following the new codes for these are important to ensure safety for you and your family!


AFCI General Overview


What are AFCIs and what Purpose do they Serve?


An AFCI is a special circuit breaker that is designed to help protect against fires resulting from electrical arcing, often caused by damaged or deteriorated wires and cords. Fires result from the heat generated from electrical arcing near combustible materials such as paper, wood, carpet, etc. Some causes of damaged and deteriorated wiring include puncturing of wire insulation from picture hanging, cable stables, drywall screws, 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.


How have AFCIs evolved into the National Electric Code (NEC)?


The 2002 edition of the National Electric Code (NEC), Section 210.12 requires all branch circuits that supply 120-volt, single-phase, 15- and 20-ampere outlets (“outlets” includes lighting fixtures as defined by code) installed in dwelling unit bedrooms to be protected by an AFCI listed to provide protection of the entire branch circuit. This requirement became effective January 2002 for all new installations.


The 2008 edition of the NEC, Section 210.12 Arc-Fault Circuit Interrupter Protection increased these requirements to include dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms for all new installations.


How do AFCIs work?


The internal circuitry of an AFCI continuously monitors current flow in the branch circuit. AFCIs apply intelligent algorithms to the current flow information in an attempt to distinguish between normal arcing (for example the arcing that occurs when a mechanical switch is opened or closed) and unwanted arcing. This allows AFCIs to detect arcing conditions that conventional circuit breakers are unable to detect. Conventional circuit breakers only respond to sustained overloads and short circuits; so they do not protect against arcing that is characterized by erratic current flow. Once an unwanted arcing condition is detected, the control circuitry in the AFCI trips – de- energizing the circuit to avoid a potential fire.