Transformer in basement ceiling buzzing--what is it?

October 23, 2013 4:54 PM

I heard this weird buzzing sound coming from my basement today, and I eventually opened up the ceiling and traced it to this transformer or something that's up in there. I tapped it with a piece of non-conductive material and it stopped buzzing. Tapped it again, it started buzzing more quietly, and then I tapped it again and it was silent. Anyone have any idea what this is, and why it's there? The house is from 1952 and doesn't have any electrical issues that I know of. Pictures: Pic 1 Pic 2 Pic 3
posted by Slinga to Home & Garden (7 answers total)

Tracing where those red and white wires go would tell you what it's for. Maybe door bell? If it's near the furnace maybe an add-on component (humidifier, ancient thermostat, etc)? Sometimes these things also get left over from previous improvements and are no longer in use.

I'm an amateur electrician, so this advice might not be best for you but... I'd disconnect it from mains and see what fails to work in the house.
posted by sbutler at 4:58 PM on October 23, 2013

It's probably for a doorbell, yeah. You can get a replacement. You just have to know what voltage this transformer is, which should be measurable with a voltmeter while taking proper precautions since you will be testing a live circuit.
posted by zsazsa at 5:06 PM on October 23, 2013

Nthing doorbell.
posted by brownrd at 6:05 PM on October 23, 2013

Yes, doorbell transformer. We had to replace ours last year, and it looked just like that.
posted by procrastination at 7:25 PM on October 23, 2013

It's is definitely a doorbell transformer. New ones are cheap and easy to replace but PLEASE PLEASE turn off the power before you replace it.
posted by Confess, Fletch at 7:30 PM on October 23, 2013 [1 favorite]

Nthing doorbell, but it might also be part of your thermostat circuit- the transformers are often similar.
As to why the buzz, two things: one, it's sitting loosely on top of conduit. Two, the core laminations can be loose. Since a transformer has an alternating magnetic field around it, either condition (or both) can cause buzzing. And bumping it, or moving it slightly, can cause it to either start or quit the buzz.
I'd suggest that you replace it- when you do, mount the new one to a joist.
posted by drhydro at 10:12 PM on October 23, 2013

Looks exactly like the dead doorbell transformer up in my attic.
posted by Thorzdad at 7:12 AM on October 24, 2013