Circuit breaker tripping at random, nothing new plugged in, help??

July 3, 2023 12:45 PM

We have a baffling new problem in our 140-year-old house. A circuit breaker, which controls (bizarrely) the lights to the stairwell to the second floor and a random selection of outlets on the second floor (one bathroom outlet, a couple of outlets in the master bedroom, but not ALL of them, an outlet in a spare bedroom... but no other lights or anything) has started tripping at random times. There is nothing new plugged into any of the outlets, and no new light fixtures, bulbs, etc.

Our usual electrician came out and replaced the circuit breaker, in hopes that that would fix the issue. it did not. We have noticed that the breaker trips when it's either very humid or raining -- and here in New Hampshire, it has frequently been both. The electrician can't come out for another week or so, since he'll be on vacation. Has anyone else dealt with an issue like this? I'm having panicked visions of the house burning down, or having to have the wiring ripped out and replaced and a huge bill... would homeowner's insurance cover that??

posted by maryellenreads to Home & Garden (13 answers total)

Turn off the breaker if you're ok with the lights being off. That will cut off the power to whatever is acting up, so your house shouldn't burn down.
posted by Slinga at 12:55 PM on July 3, 2023 [7 favorites]

Are there any outdoor outlets or exterior lights (or the remains of either) on the same circuit? There may be water entering a box somewhere creating a short that causes the breaker to trip.

If it's still raining when you reset the breaker, does it trip again right away? Are you ever unable to reset the breaker because it won't stay closed? If you wait until things dry out, does your success-rate of resetting the breaker increase?

On such an old house, there may be some forgotten part of the circuit that's getting exposed to the elements. Check your eaves and attic for anything obvious. The electrician should be able to trace out the entire circuit. In the meantime, leaving the breaker off is probably the safest thing you can do.
posted by RonButNotStupid at 1:06 PM on July 3, 2023 [5 favorites]

Yeah, keep that circuit off. Be prepared, however, when your electrician tears into the walls to find the problem, that they discover knob-and-tube wiring, that your homeowners insurance suddenly doesn't apply any more because there's probably a carve-out for that, so you'll need to have the house rewired at what will probably be five figures and several weeks of very annoying wall-destroying renovations.

I could be wrong, and I hope not, but just ... be prepared for one of those "oh this is a simple problem" things to snowball into an avalanche of pain.
posted by seanmpuckett at 1:07 PM on July 3, 2023 [5 favorites]

Improper grounding or shorting can cause this, and they're not uncommon issues in old houses whose wiring has had decades to deteriorate or been subject to piecemeal repair.

FWIW, I live in a 100 year old, pretty ramshackle house that has had similar issues, including surging in some sockets. We can't currently afford to overhaul it, as it will involve demoing all-plaster walls, which will only add to the already (yes - I've gotten estimates) high cost. We are very careful not to overload the system, and there are some sockets we just don't use for now.
posted by ryanshepard at 1:36 PM on July 3, 2023 [2 favorites]

Does the bathroom outlet have a gfci on it? (the outlets with little test and reset buttons?)

Those things do fail and can exhibit this behavior when they do.

You could always buy a simple outlet tester and start checking them all.
posted by chasles at 1:51 PM on July 3, 2023 [4 favorites]

The reason people are talking about your house burning down is this: somewhere around your house, there are wires with exposed metal. Those wires are very close to each other, and when there's enough moisture in the air, they are close enough that they essentially touch. When that happens, it makes a short circuit, which would lead to a quick build up of heat, sparks, all kinds of exciting and dangerous stuff. Fortunately, your circuit breaker is shutting off the current immediately - but it's still dangerous to have that happen over and over.

I would consider calling in another electrician since this counts as an emergency to me. If you can live without electricity until your dude is back from vacation, awesome -- having someone you trust in this situation is super helpful.

However, chances are that all of your wiring needs to be checked, and maybe redone - this sounds like an age-related issue. So, having a second electrician might not be terrible -- maybe your main guy (see what I did there) knows someone who he'd like to work with on this job, since it might be a big one. And maybe that second someone could come check out the house ASAP.
posted by amtho at 2:05 PM on July 3, 2023 [8 favorites]

The question of what your homeowner's insurance covers can only be answered by looking at your specific policy. There may be legal minimums in your state, but they probably don't cover faulty wiring. A home warranty, if you have one, may cover this, but again, it depends on the coverage you bought (and they are notorious for finding any way to avoid payouts and minimize expenses).
posted by Aleyn at 2:17 PM on July 3, 2023

So yeah, there is probably a short somewhere, and homeowner's insurance is unlikely to cover it. But depending on exactly how the house is constructed, running new wires may not be as horrifically expensive as you fear; sometimes it's not that hard to fish wires through the old wires' paths. So leave the circuit off and don't panic yet.
posted by metasarah at 2:45 PM on July 3, 2023 [1 favorite]

Something else to try would be unscrewing all the light bulbs on this circuit and see if the problem goes away, one of them may just be on the verge of failing.
posted by Lanark at 3:06 PM on July 3, 2023

You say "nothing new plugged in to the outlets" but one or more of the existing devices that are plugged in may be faulty. Step number one is to unplug everything that's plugged into the outlets on the circuit and see if the problem goes away.

Knob and tube wiring traditionally is done in such a way that maintains pretty decent spacing between the two conductors, typically 4+ inches, so the probable short points will be at junction boxes rather than random spots in the middle of the wall or something. Anything is possible though and you never know what sort of hacked adaptations might have been done over the years.

If you want to split the difference between safety and testing, you can shut the circuit breaker off a couple of hours before bedtime. (A fire while the occupants of the house are awake would be Not Great, but a fire while people are sleeping would be potentially much worse.)

I am a little skeptical of the relationship between the weather and the issue, unless the existing breaker is a GFI or Arc Fault type one. A little moisture is unlikely to pass 15+ amps of current needed to trip a standard breaker. People notice all kinds of coincidental correlations when something occurs randomly. GFIs are much more sensitive to any current leakage and some slightly damp, deteriorated insulation could cause some nuisance tripping.
posted by Larry David Syndrome at 4:03 PM on July 3, 2023

Response by poster: We don't have knob-and-tube wiring -- the house was renovated about 8 years ago. We double-checked the inspection report.
posted by maryellenreads at 4:22 PM on July 3, 2023 [1 favorite]

Chances are that this is water coming in from a leak and shorting out something.
Modern wiring is waterproof, so it's going to be where there's a connection. This by law has to be inside a small metal box with a cover, and they have to be accessible. You can start by taking the covers off and looking inside for water, and looking where your light fixtures are attached to walls and ceilings. If there's water, that's it.
But really, it's obvious you have a leak - and I'd first check inside the breaker panel for water hitting that circuit - and your first order of business is to find and fix the leak. If you have an attic, get up and look. Walk around and look at your ceilings. Water doesn't have to appear anywhere near the leak, but that's how you start.
Once the leak is fixed the wiring should behave normally.
posted by AugustusCrunch at 4:42 PM on July 3, 2023 [2 favorites]

Modern wiring is waterproof, so it's going to be where there's a connection.

If rodents are in the house you cannot guarantee the integrity of your wiring - mice will gnaw insulation, leading to problems like you describe.
posted by HiroProtagonist at 5:27 PM on July 3, 2023 [4 favorites]