Why does my AFCI breaker keep tripping?

Real fault or nuisance trip

An arc-fault breaker (AFCI) that keeps tripping is either catching a genuine arcing fault in your wiring or nuisance-tripping on a harmless load, and telling those two apart is the entire job. Reset it once. If it trips again and again, especially with a burning smell or always on the same circuit, treat it as a real fault until proven otherwise.

An AFCI does something a regular breaker cannot: it listens for the erratic electrical signature of an arc, the small sparking from a damaged cord, a pinched wire, or a loose connection, and cuts power before that arc can start a fire. The trouble is that some ordinary things, certain motors and electronics, can produce a signature the breaker mistakes for an arc. For the full picture of what an AFCI is and how it differs from a GFCI, see our AFCI, GFCI, and surge protection guide.

What causes nuisance trips

Nuisance trips are common, and in older Portland homes one cause stands out: shared neutrals. When a home was wired before AFCIs, circuits sometimes share a neutral wire in a way that confuses an arc-fault breaker, and it trips even though nothing is wrong. Certain appliances set them off too.

• Motor loads: vacuums, treadmills, power tools, some furnace blowers
• Older electronics and some LED drivers or dimmers with noisy power supplies
• Shared or crossed neutrals from pre-AFCI wiring, a frequent culprit in older homes
• A slightly incompatible pairing of a specific AFCI breaker and a specific device

What a real arc fault looks like

A true arc fault is the reason the breaker exists, and it is what you do not want to dismiss as a nuisance. These point at actual damage inside the wiring, and they should be found and fixed, not worked around by swapping in a regular breaker.

• A burning or hot-plastic smell anywhere on the circuit
• Warm or discolored outlets or switch plates
• Trips that started after a nail, screw, or a recent remodel that could have pinched a wire
• A backstabbed or loose connection at a device on that circuit

How to narrow it down

You can safely do some of the isolating yourself before calling. This tells the electrician a lot and sometimes solves it outright.

• Unplug everything on the circuit, reset the breaker, and see if it holds with nothing connected
• Add devices back one at a time until it trips, which fingers the culprit appliance
• Note the AFCI's trip-indicator: many blink a code that distinguishes a series arc, a parallel arc, or an overload
• If it trips with the whole circuit unplugged, the fault is in the wiring, not a device, and that is an electrician's call

When to call, and the fix

If the breaker trips with nothing plugged in, if you smell burning, or if you cannot pin it to one appliance, have a licensed electrician trace it. The fix depends on the cause: correcting a shared neutral or a loose connection, repairing damaged wiring, or in a genuine compatibility case, fitting the right AFCI. What we do not do is defeat the protection by dropping in a standard breaker, because that removes the fire protection the code put there. This is bread-and-butter electrical repair, and often it is a wiring correction at the panel.