Electrical Code Requirements
Starting with the 1999 version of the National Electrical Code (NFPA 70) in the United States (US), and the 2002 version of the Canadian Electrical Code in Canada (CSA Standard C22.1), the national codes require AFCIs in all circuits that feed outlets in bedrooms of dwelling units. This requirement is typically accomplished by using a kind of circuit-breaker (defined by UL 1699) in the breaker panel that provides combined arc-fault and overcurrent protection. Not all US jurisdictions have adopted the AFCI requirements of the NEC as written.
The AFCI is intended to prevent fire from arcs. AFCI circuit breakers are designed to meet one of two standards as specified by UL 1699: "branch" type or "combination" type (note: the Canadian Electrical Code uses different terminology but similar technical requirements). A branch type AFCI trips on 75 amperes of arcing current from the line wire to either the neutral or ground wire. A combination type adds series arcing detection to branch type performance. Combination type AFCIs trip on 5 amperes of series arcing.
The advanced electronics inside an AFCI breaker detect sudden bursts of electric current in milliseconds; long before a standard circuit breaker or fuse would trip. A "combination AFCI breaker" will provide protection against parallel arcing (line to neutral), series arcing (a loose, broken, or otherwise high resistance segment in a single line), ground arcing (from line, or neutral, to ground), overload protection and short circuit protection.
In 2002, the NEC removed the word "receptacle", leaving "outlets", with the effect for lights and other wired-in devices such as ceiling fans within bedrooms of dwellings are added to the requirement. The 2005 code made it more clear that all outlets must be protected despite discussion in the code-making panel about excluding bedroom smoke detectors from the requirement. "Outlets" as defined in the NEC includes receptacles, light fixtures and smoke alarms, amongst other things.
As of January 2008, only "combination type" AFCIs will meet the NEC requirement. The 2008 NEC requires the installation of combination-type AFCIs in all 15 and 20 ampere residential circuits with the exception of laundries, kitchens, bathrooms, garages and unfinished basements.
Read more about this topic: Arc-fault Circuit Interrupter
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