AFCI Protection

A standard breaker trips on overload or a dead short, but a series arc across a nicked wire or loose terminal can smolder for months below its threshold. An AFCI recognizes the high-frequency, irregular waveform of arcing and opens the circuit.

Required for bedroom outlets in 1999, AFCI protection now covers most habitable-room branch circuits.

When it applies

Arc-fault protection reaches almost everywhere people live now — bedrooms, living rooms, kitchens, hallways, closets and laundry areas. If you are running a 15 or 20 amp, 120 volt circuit that serves those spaces, plan on protecting it, whether that means an AFCI breaker or a protected outlet device at the first box.

Common mistakes

• Sharing a neutral between two circuits and then wondering why the AFCI trips the moment you energize it.
• Leaving a nick in the wire from a rushed staple or a sharp box edge — the breaker is doing its job when it senses that.
• Feeding a big motor load, like a vacuum or treadmill, and blaming the device for nuisance trips before checking the connections.

In the field

When a client calls me about a breaker that keeps popping, I start at the connections, not the breaker. Nine times out of ten I find a loose backstab or a stray neutral strand, tighten it up, and the trip stops for good.