What Is an ARC Fault Breaker?

According to the 2008 National Electrical Code, Section 210.12, an arc fault breaker, or arc fault circuit interrupter (AFCI) provides "protection from the effects of arc faults" to prevent electrical fires. These breakers are required in "family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sun-rooms, recreation rooms, closets, hallways or similar rooms or areas."

What is an Arc Fault?

Electrical fires destroy over 40,000 homes a year.
When electricity jumps from the circuit to a conductor, an arc is formed.

An arc fault occurs when an electrical wire's insulation is damaged. The exposed wire allows the electrical current to escape from the conductor, contacting other objects. For example, on a very small scale, an arc occurs when a plug is pulled out of a socket and there is a blue spark. That spark is a small arc of electricity. If a large arc contacts combustible material and is hot enough, it will start a fire.

Types of Arcs

There are two different types of arcs. A series arc occurs in the same wire as the current "skips" along the wire instead of "flowing." This happens when the wire or insulation is damaged but the arc is not able to connect with another conductor. A parallel arc occurs when the current jumps to another conductor or material separate from the wire.

Types of Arc Fault Breakers

A branch feeder arc fault breaker detects parallel arcs and disconnects the circuit. A combination arc fault breaker detects parallel and series arcs and will disrupt the current if either occurs.

How an Arc Fault Breaker Works

An arc fault breaker monitors the circuit, and if unwanted arcing occurs, it trips the breaker, interrupting the electrical current. Without current, the arc is extinguished.

Why Arc Fault Breakers are Required

Arc fault protection is required by the National Electrical Code and is necessary for safety. In the United States annually, there are over 40,000 electrical home fires, resulting in more than 400 deaths and 2,000 injuries. Smoke detectors, fire extinguishers, and other safety devices help deal with electrical fires, but arc fault breakers stop the fire before it starts.

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