Strange Electical Sounds

August 18, 2008 1:07 PM

What is causing the strange metallic "clank" sounds that appear to be coming from one of the junction boxes on my ceiling?

I live in a loft with high ceilings that had poor lighting and recently had some electrical work done. I had quite a bit of new conduit run, fixtures hung, and new switches installed. Towards the end of this project when I turned on one of the light switches, there was a loud metallic "clank" sound that seemed to come from one of the new junction boxes on the ceiling. Since then, the sound is completely random, although it is always associated with some new load to the electrical system, such as the AC unit coming on. Sometimes there won't be any sound for weeks, other times several times/day. It seems to be unconnected to how many or few electrical devices are on.

I asked the electrician when it first started what the sound was. He said he had never heard anything like it but would look into it. I asked him if the system was overloaded, if there was adequate amperage, etc. and he said that everything was fine in that regard. He is licensed. Unfortunately, I gave him his final payment before he sorted this issue out and I cannot get him to return to resolve this.

It is mostly a piece of mind thing. I want to know for sure what is causing it and correct the problem. None of the circuit-breakers have ever popped in my unit.

Is this the type of thing that an electrical trouble-shooter could sort out without huge expense?

posted by philmas to home & garden (8 comments total)

Could it just be someone walking around upstairs and causing something that's loose to hit something else? What are the floors/ceiling like in your building?
posted by GuyZero at 1:12 PM on August 18, 2008

Heat contraction/expansion from the load going through the box? Is it instantly when you add the extra load? Or after a few seconds?

Either way, I'd get it checked out, once you have experimented and ensured it is related to electrical load and not from some other source. Electrical devices that aren't "My Tandy Electrical Clanker" shouldn't be clanking.
posted by Brockles at 1:23 PM on August 18, 2008 [2 favorites]

I have seen extremely high currents cause wires in to jump inside the conduit but that was a short circuit condition and the breaker popped immediately. I would not use that circuit until you have it checked out by another electrician, there's no way any sound should be coming from your wiring.
posted by tommasz at 1:29 PM on August 18, 2008

although it is always associated with some new load to the electrical system, such as the AC unit coming on
this is important. i suspect that you are searching for a correlation rather than being a neutral observer (not a personal criticism - confirmation bias means you are human, not that you are stupid). you really need to nail the correlation. next time it happens, be very critical with assessing what might have triggered the noise. see if you can repeat it - if it's the ac then go turn the ac off and then on again.

it's very odd for electric circuits to make such a noise; even odder that they don't trip the circuit breaker; stranger still that it's not always triggered by the same event. the odds really are on it being something else. extraordinary claims do need extraordinary evidence.

i'm not saying ignore this - i'm just being practical. yes, it's so odd that the most likely explanation is that you've confusing some other noise with the electrics. but it's also sufficiently likely to be dangerous (if it is electric and not tripping in the breaker then there's the possibility things are very unsafe) that you shouldn't let it drop. which is why you need to work to improve the data you have.
posted by not sure this is a good idea at 2:25 PM on August 18, 2008

If it truly is associated with the AC turning on or off, it could be a loose or broken motor mount in the unit, and you're hearing the motor move when the compressor powers on or off. My fridge does the same thing for that reason.
posted by mudpuppie at 2:46 PM on August 18, 2008

Is there any possibility this could be an electrical relay that's switching on an AC or some other load? Electrical relays do click & clank.
posted by crapmatic at 3:04 PM on August 18, 2008

If you've got conduit running to the noisy boxes I'd bet the sound isn't originating in the box. Instead the sound is being generated elsewhere and is just being transmitted by the conduit like a speaking tube. A loose transformer will clunk as will some relays. I can't think of what could be causing this for something as simple as a light switch. Do you have Halogen or low voltage track lighting? Both of those use transformers.

"Is this the type of thing that an electrical trouble-shooter could sort out without huge expense? "
Intermittent problems can be hard to track down. It would be worth it though to have someone over to inspect the installation; maybe remove the cover plates from every box on that circuit and have a look. Shouldn't take more than a hour labour.
posted by Mitheral at 3:22 PM on August 18, 2008

It would help to know more about the nature and volume of the sound but I have two guesses:

1. a relay with a physical switch that is either loose or attached in such a way to reverberate the metal plating

2. Cylons
posted by Jon_Evil at 9:54 PM on August 18, 2008