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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?

  • Can you post photos of the breakers in question please? Also, do they trip with no loads on them, or only when/shortly after certain loads are turned on? – ThreePhaseEel May 16 at 2:06
  • Thanks for the quick reply! I just posted a photo of the 2 breakers. I haven't tried unplugging everything but they have very little load from the receptacles. In total for the 2 breakers: 1 floor lamp (15W), google mini, mini sound bar, led tv, and 2 ikea desk lamps. It had this same load for about 1 year now. – raycphoto May 16 at 3:12
  • Try unplugging/switching off all loads and seeing if the breakers hold -- if they hold, then plug in/turn on each load one at a time and seeing which one trips the breaker – ThreePhaseEel May 16 at 3:19
  • Actually the one that automatically trips has nothing plugged in the receptacles, very strange. The one that trips after a few mins is the one that has things plugged in. – raycphoto May 16 at 3:46
  • Are there any light fixtures/switches on the one that trips instantly? – ThreePhaseEel May 16 at 5:44
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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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  • Thank you for the detailed response! Looks like I have some work to do. I really hope it's only a bad breaker. I am just waiting for the replacement breaker to arrive. I will update this post if anything changes. Thanks again! – raycphoto May 16 at 23:59
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    Update for the instant trip breaker situation: when you said "moisture" something clicked to me so I decided to check the bathroom fan and open the cover, and man looks like we found the culprit. There was what it looked like a clump of rodent poop clumped together in little balls but turns out to be melted plastic from the fan I'm guessing? and I do remember now, that sometimes when I switch on that bathroom fan it would make this popping/cracking sound before turning on. I unplugged the fan, reset the breaker and no more instant trips! 1 more problem breaker to go! – raycphoto May 17 at 2:26
  • Update for the 2nd breaker situation: Replacement breaker came today and read instructions on how to clear a "last known trip condition". So I decided to try this on the old breaker and looks like it may have resolved the issue (partially) so far. No more trips and its been over 2 hours with the same load. I say partially, because Now even though the breaker is ON, there is still no power to the lights or receptacles in 2 out of 3 bedrooms that are on this circuit?? the 1 bedroom is fully restored (lights and receptacles). This is so strange! – raycphoto May 17 at 18:12
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    @raycphoto -- the latter issue sounds like a failed splice or backstab somewhere downline (which could have explained the AFCI tripping, too, due to the splice arcing as it was in the process of failing) – ThreePhaseEel May 17 at 19:10
  • I spoke too soon. Now this intermittent breaker is back to having the same symptom. Nothing is plugged into this circuit, no bathroom fans. I guess its really time to replace it. – raycphoto May 24 at 23:46

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