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What is an Arc Fault Circuit Interrupter (AFCI) and where should they be used?

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up vote 11 down vote accepted

AFCI's detect patterns of current that usually indicate some sort of electrical problem. Unlike a GFCI which is making sure that current going out = current coming back, AFCI's try to look for electrical usage that would not trip a GFCI but might be something causing an electrical fire. Most code now requires them for bedroom circuits.

The one major drawback for them is that some stuff tricks them into tripping. Often times larger machines with motors, like a vacuum cleaner or power tool can trip them. They are still a good thing to have, just be aware of this limitation

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The code differs widely depending on where you live. Not only are they not required in my area, I have never actually seen one. – Brad Gilbert Jul 24 '10 at 4:49
Why did they choose to only require them in bed rooms? What about that type of room makes them suited for that? – C. Ross Jan 23 '12 at 13:31

An arc fault circuit interrupter (AFCI) contains electronics that detect sudden bursts of current, faster than a circuit breaker would trip. This is intended to prevent fire from arcs.

An arc fault circuit interrupter (AFCI) is different from the more common ground fault circuit interrupter (GFCI).

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