Electrical – 2 AFCI Breakers Tripping – One instantly and the other after a few minutes

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I have 2x 15amp AFCI Siemens breakers, both are tripping. One breaker would trip instantly and the other one after a few minutes. Nothing new was plugged in into these circuits. It just happened out of the blue and was working fine for years. The house was built around 2003.

The breaker that instantly trips connects to the master bathroom which has a light, 2 receptacles (non gfci), and bathroom fan. It also connects to the laundry room but only to the light and fan. Lastly, it also connects to 2 lights in the upstairs hallway.

The breaker that would trip after a few minutes is connected to 3 bedrooms, 2 rooms has 2 receptacles and the master has 3 receptacles.

Would replacing the breaker be my first (quickest) option at this point?
would swapping breakers to see if the instant tripping follows the breaker or the circuits be a good troubleshooting idea?

Best Answer

If a swap reveals that the symptoms stay, i.e. other AFCI are also tripping in the same circuits, and all devices/lamps etc. were disconnected, there is most likely one or more problems with the panels/boards or wires. Since the AFCI is tripping immediately, it seems to be a static fault and therefore an insulation tester would help to find the location via a bubble search, i.e. iteratively disconnecting half of the wires/outlets/circuits. Since an AFCI detects HF signals, a portable AM receiver may help searching when the insulation tester feeds that faulty location. Possible reasons:

  • Water damage from heavy rain or moisture or plumbing, spilling/overfilling of bathtubes, sinks etc.
  • Rodents or insects having destroyed the insulation resulting in leakage currents
  • Any recent work like hammering nails or turning screws into the wall or ceiling
  • Earth movings/oscillations from earthquakes, underground activities, mining, construction activities, subways etc. causing stress to the building

If the AFCI are faulty, possible reasons are an overload, e.g. by a lightning strike or a shortcut or electric switching activities of the power supplier or any surges in the power lines. The main panel surge protection - if any - can not cover 100% of all possible surge events. Maybe neighbours do have similar problems.

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