It was being temperamental, working for periods, and then tripping for periods.

So I replaced it with another Siemens combo breaker, but it still trips. If I replace it with a non GFCI breaker it works just fine. Part of this circuit does the outside lights, thus the GFCI.

I’ve set up an appointment with an electrician, but is there anything else I should try first?

  • 1
    What is on the other part of the circuit?
    – crip659
    Aug 4 at 13:46
  • 1
    Does "non GFCI" mean AFI only, or does it mean just a plain breaker? If it's an AFI breaker you should focus on manasseh's answer. Otherwise you need to think about both answers and some kind of search-based approach to finding the source of the problem. If there is one jbox where all the outside boxes are fed from, and you know where it is .... disconnecting them for a while should reduce the scope to either inside or outside.
    – jay613
    Aug 4 at 17:57
  • @jay613 Also if non-GFCI means plain breaker then the diagnostic code from the GFCI/AFCI would be very helpful here. Aug 4 at 19:59

3 Answers 3


You should start by determining whether this is tripping from:

  • Overload
  • Ground fault
  • Arcing fault

The breaker will tell you - google up the instructions for the breaker and it will explain the procedure (if any). Some models need electricity to store the fault codes, so pulling the breaker out of the panel and swapping may have destroyed that information.

The ground fault case has been discussed at length by manassehkatz.

An overload is either the circuit being generally overloaded, or an intermittent short.

An arcing fault is current "leaping" across a poor electrical contact, due to a defective or badly installed splice, or faulty device. It is making tremendous heat at the faulty connection, and this can cause burn-up of the wires, box and even start a fire. It was invented to reduce electric blanket fires, but was found to be very good at detecting backstabs (whoops, said the quiet part out loud) arcing at bad connections in walls. That is why it is broadly required now.

If you've ever heard someone hooking up stereo speakers with the amplifier turned on, and there's a "crinkle crunch" sound... Or a bad microphone cable can cause this as well. Or plugging in headphones. A digital signal processor inside the breaker is "listening" for this "sound". This is not a perfect science, but still, the first thing I would check is wire connections along the route.

I would focus on opening up every junction box in the circuit, and closely inspecting any connections that might be faulty backstabs. Seriously, the problem with backstabs is they have a long track record of connection failurs, and are not inspectable, except by wresting the wire out of the hole and visually inspecting it for arcing marks. Since holes are not reusable (the spring has sprung), best to move it to the side screws, and torque to spec with a torque screwdriver.

Torque screwdrivers are required as of NEC 2014 because of many, many failures of terminals that were hand-torqued by pro electricians - science has shown no one can hit torque specs "by feel".

  • 1
    My strong hunch of "ground fault" is based on "replaced with a non-GFCI" to mean "AFCI but not GFCI". If OP actually swapped it for a plain breaker than arc faults are potentially in play here, as you describe. But "intermittent" + "outside" points to ground fault. Aug 4 at 18:21

You have diagnosed that this is a ground fault. This is quite common for outside electrical circuits, which is why they need GFCI protection. If the lights are hardwired rather than plug-in and in the ceiling or high up on a wall then they may not actually require GFCI protection. But since you know you have a ground fault, it makes sense to fix it for safety's sake.

Since the problem happens intermittently, my hunch is rain. There is a good chance you have either a light fixture or a junction box that is getting water in it and then has a ground fault. Once it dries up, the fault goes away. Keep in mind that water will potentially get into everything outside. A few things to look for:

  • Make sure that junction boxes and light fixtures are able to drain. Otherwise they can collect moisture due to rain or even just condensation and it fills up the box and causes a ground fault. If water can drain easily then that problem is minimized.
  • If there are any receptacles (e.g., plug-in lights instead of hardwired), make sure they are weather-resistant and have a good in-use cover.
  • Make sure that any covers on light fixtures are securely fastened. Depending on design, there may be gaskets (which can wear out) or there may be places you can caulk to seal from water. Or even just a little tape in the right places.
  • There is no evidence presented to rule out an arc fault here.
    – nobody
    Aug 4 at 20:34
  • The evidence is based on outside and intermittent and that non gfci didn't have a problem. Aug 4 at 21:34

So the answer here, at least so far, was that it was a bad outlet. I had installed a USB enhanced outlet seven years ago, and apparently that was failing. I don’t know why a non GFCI breaker (AFCI only) made the circuit stop tripping. Reinstalling the original GFCI after replacing that and everything is working so far.

Unless it was just timing, and rain was somehow involved. If it happens again, that will be my suspicion. Thank you everyone!

  • Any receptacle, and certainly including a USB receptacle since that is more complex than a plain receptacle (a plain receptacle has no electronic components - just metal parts insulated in plastic) can fail and cause a ground fault. However, I am skeptical that this is the only problem due to the intermittent nature. Time will tell. Aug 5 at 14:23

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