An Arc Fault Circuit Interrupter (AFCI) is a circuit breaker designed to prevent fires by detecting an unintended Electric arc and disconnecting the power before the arc starts a fire. An AFCI must distinguish between a harmless arc that occurs regularly when switches, plugs and brushed motors (like vacuums) are used and an undesirable arc that can occur, for example, in a lamp cord that has a broken conductor in the cord. Arc faults in a home are one of the leading causes for household fires. Each year in the United States, over 40,000 fires are attributed to home electrical wiring. These fires result in over 350 deaths and over 1,400 injuries each year. Conventional circuit breakers only respond to overloads and short circuits; so they do not protect against arcing conditions that produce erratic, and often reduced current.
An AFCI is selective so that normal arcs do not cause it to trip.
The AFCI monitors the current and discriminates between normal and unwanted arcing conditions. Once an unwanted arcing condition is detected, the AFCI opens, de-energizing the circuit and reducing the potential for a fire to occur. An AFCI should not trip during normal arcing conditions, which can occur when a switch is opened or a plug is pulled from a receptacle. AFCIs resemble a GFCI (Ground-Fault Circuit Interrupter) in that they both have a test button although it is important to distinguish between the two. GFCIs are designed to protect against electrical shock while AFCIs are primarily designed to protect against arcing and fire.
Electrical code requirements
Starting with the 2008 version of the National Electrical Code (NFPA 70) the national code require AFCIs in all circuits that feed outlets in all living areas 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.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.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.
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