I just moved into a condo I'm renting for a month and the first two nights were fine, but on the third night I was awakened by a low humming sound. It actually woke me up. I had no idea what it was and checked the clock, the light, etc. I realized the sound was coming from the wall behind my bed. I eventually went outside the unit and found to my surprise that the electric meters were on the exterior wall and thus that's the source of the noise. This low humming was so irritating I got up and slept on the couch.

I noticed in the morning the humming had stopped. At approximately 7 pm the next evening I heard a "clunk" and the humming started again. I put two and two together and realized the meter was cycling - during the day there was no hum, and at night when it switched off (or whatever it does, I guess for the night time rates), this low hum comes from the meter through the wall.

I have contacted the condo management about this but somehow I doubt anything will be done about it, but want to know if anyone else here knows what's going on? Is this a smart meter? It makes a clunk when it goes off in the evening and a clunk when it goes on in the morning at around 6 a.m. As indicated, during the day, all is fine and no humming (I turn the t.v. off and it's clearly not making the sound or hum it makes at nite). I'm really ticked off that a builder would have meters on an exterior wall of a bedroom where people sleep, but that's the way it is. Naturally I hope the low hum can be stopped but if not I'm stuck sleeping on the couch for the month I'm renting this corporate condo. Lucky me, huh?

Any suggestions appreciated before the "management" checks this situation out!

Bet it's a lighting contactor. It would go thud and would be on at night. The coil could hum as you described.

Here is a discussion, although not probably understandable, that addresses your issue. "quiet" 200 amp contactor - Contractor Talk - Professional Construction and Remodeling Forum

Kiss is correct, I also think it is a lighting contactor for exterior site or security lighting.

An electrically held contactor is in use, means the coil of the contactor is energized all night, and that would hum.

A mechanically held, AKA Latching, contactor will solve the problem, and the hum will go away.

Depending on the size of contactor needed, can be costly. May be difficult to get management to pay for this upgrade.

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Originally Posted by tkrussell

Kiss is correct, I also think it is a lighting contactor for exterior site or security lighting.

An electrically held contactor is in use, means the coil of the contactor is energized all night, and that would hum.

A mechanically held, AKA Latching, contactor will solve the problem, and the hum will go away.

Depending on the size of contactor needed, can be costly. May be difficult to get management to pay for this upgrade.

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Thanks for the info, I will certainly bring it up if the management says there's no problem. I don't offhand see any security lighting that would account for this though. I can hear the hum through my bedroom wall at the precise location of the bank of electrical meters that share the exterior wall, so I still tend to think it's related to the meters. I've read other posts on forums that say their meters shut on and off with a "clunk" so I'm tending to think it's the meters. But the night time issue is the real clue here. During the day, if I put my ear up to the wall I can still hear a very faint buzzing, but not audible within the room until night when it comes online with a clunk at around 7:15-7:30 (the time varies a bit, which is interesting also, if it's on a precise timer, it should be the same time every night I would think?)

A coil has been mentioned on another forum too with regard to a transformer. I agree, if it's something pricey that management won't pay for, I'm sol, **** out of luck and stuck living in this condo for a month sleeping on the couch in the livingroom. Each unit is individually owned and operated so management probably only takes care of bare minimum to keep the grounds maintained or safe. Anyway, I'll let you know what I find out, and thanks again for more info that maybe I can use to get some help!

Upon further inspection, I just now went outside and there IS a security light on that side of the building which shares the exterior wall of my unit. The only problem is, it doesn't line up with the area of the wall where the hum comes from. However, perhaps it is sending some type of electrical buzz/hum through the electrical box/meters. So, it's a possible as you suggest, a lighting contactor or some issue related to the light.

Plus the fact that this is a night time only issue. I find it interesting also that the humming hasn't started at the precise same time, so that may indicate that the lighting turns on at somewhat different times in relation to variable time of sunset or evening hours. I am going to go out and observe this light to see just when it cuts off and if it's around 6:30 am (which is the time the humming usually seems to stop) I think it may indeed be the culprit.

We have a winner! KISS you were correct and I have rewarded your efforts since you were the first in line on this. I went out and watched the security light cut off at 6:30 am and of course the buzzing stopped inside the unit. I think the management can now simply cut that light off (there's other lights in the complex that can make up for it), if it means I can't sleep in my room at night. It's that or I move out and I don't think they or their owner wants that over a stupid light. Thanks again and whether they fix it or not, at least they can't b.s. me about what it is. Thanks again sincerely. You made my day. And NIGHT!

There is something known as as Astronomical Clock. It bases it's on and off times by sunrise and sunset. I have a small plug-in timer by Intermatic for a light.

Good luck and thanks.

If there is a code that dictates the placement of the security lights, more than likely it is a building code and I have no experience with building codes as yet.

The light may have to stay exactly where it is. Which, in-turn means that the only appropriate fixes would be to change the location of the feed to the security light (probably not going to happen) or change the type contactor to a magnetically energized coil.

This will stop the armature from chattering as it reacts to the changes in the AC circuit that feeds it.

The problem with this be a condo, at least as I seen it is that you are someone's tenant and not an owner in the condo association. Plus, as you said, you are only renting for a month.

The person that has to champion this request to the association is not you, it is the owner of the condo.

If no other renter of the unit has complained of the problem the best you could probably hope for is that the association would send someone (electrician) to look at the circuit to make sure that the current configuration is working as designed.

Good luck.

Hopefully I am not too concerned about getting the light turned off while I rent here. This is in Las Vegas and owners are desperate for tenants. 3/4 of these condos are rented out, probably a lot of the security lights aren't even working (I saw several this morning not on). Let them get the others back up and working (especially if non occupied or empty, which a lot of them probably are in this economy) and turn mine off so I can sleep at night. This isn't the normal condo situation out here... lots of foreclosures and they are lucky to have people who come out here and rent their condos in the first place. If they fuss about turning the circuit to this humming light off for one suffering person while they let whatever else goes on around here, that will be ridiculous.

I'm not asking them to reconfigure the light. I know they won't do that. Just turn it off, cut the power to it at the circuit breaker or however it would be switched off. There's plenty of other lights around here that either they can be using or should get up and running for more than adequate security light. And if the owner of this place doesn't know about this annoying hum, he/she should, because they are renting out a unit with a very irritating problem that backs up to a bedroom where a tenant sleeps, so I feel they need to know about it. I can't be concerned whether past tenants complained or not. Maybe they weren't even home at night or whatever the situation may be... maybe they didn't want to come to the attention of the management for various certain reasons. That doesn't make my complaint less valid. But thank you for reminding me that this may happen and I may have to continue to fight to my own rights here as a tenant to get a decent night's sleep.

Here's an update on the situation: the condo maintenance guy looked at the light and said it was a circuit breaker about to go bad that controls the security light. The buzzing hum is coming from the circuit breaker box, whichever breaker controls the light. So, he said he will replace the bad breaker. Hopefully that will be done soon. Didn't get it done today so another night spent on the sofa instead of the bedroom where the buzzing is.

In any event, apparently it does not require something as involved as an entirely new configuration of the light. According to him, it's a bad circuit breaker which he said will make a hum like that when it's starting to go bad. As far as I know, this did not get done today. (the light turned on and the humming circuit in the breaker box is still going). I know that sometimes it can take awhile to get a new breaker, so maybe they had to order one. I wanted to update about this because hopefully it turned out to be something SIMPLE and not an involved job of redoing a lighting contactor or whatever was suggested earlier. No one suggested a bad circuit breaker. I hope this maintenance guy is right and that's all it is and he isn't just under estimating the problem. But I think he's probably right. I still am very glad KISS helped me to identify the security light as the source of the problem which definitely helped me out today to troubleshoot for the maintenance guy. He could clearly see that when the light was off, the buzzing stopped and when he turned the light back on, the buzzing started. I'll let you know if it is fixed once and for all soon!

That's interesting, I have never of a breaker causing a relay to chatter.

Usually, it's the coil itself or the latch mechanism. Or the ground from the magnet being dirty.

Theoretically, I can see where a weak breaker might not be able to sustain the needed current to hold the coil active, but I would think that if it could not, the breaker itself would trip.

Please let us know what the final fall out is. Thanks

Sounds like the maintenance guy is guessing... and probably guessing wrong. I've heard breakers buzz, but never loud enough to resemble a contactor noise.