I love when I've lived somewhere for a while and come across something that I can't identify.

Could someone tell me what is attached to this light fixture in my furnace room? It's some sort of low gauge wire coming in from one side of the room, going into this block attached to the fixture, and then running out the other side of the room. It's clearly not the power for the light (that would be the white romex coming in from the left). It almost looks like ethernet, but it's certainly not that. I would google it, but I can't think of what to search for.

Anyone know?

Looks like a low voltage ac transformer for your house doorbell. One thin wire runs to the actual doorbell, the other to the push button near the front door.

Excellent question. There is one of those on the ceiling of my garage, it is near some ceiling lights exactly like the one pictured, and I want to know the same thing.

It’s possible I may have already asked this question here on the BBS and gotten an answer that I don’t remember.

It looks like a DC transformer but why would one be needed on our garage ceiling?

I vaguely remember either being told this or deciding this too.

Is there a chance that this thing could emit a low hum that's picked up by my pro audio gear during recording sessions? The floor of the studio is directly above the ceiling of the garage. And I've had an everpresent faint hum at approx 60 cycles that I keep having to deal with.

As others said, most likely the doorbell transformer. But possibly instead a transformer for powering a furnace humidifier (ugh!), or sometimes even an alarm system.

But most likely, for the doorbell(s).

As for 60Hz hum, the transformer itself will typically have an audible hum. So if that is audible in the recording room, then it might be picked up there.

But 60Hz electrical noise is also present in all of the home wiring, including the wiring powering the audio gear. And the most likely source of 60Hz in a recording is from the 60Hz electrical noise of that wiring.

Finding and eliminating sources of AC electrical hum or buzz in audio gear is a science and art all its own.

There is also a lot of misunderstanding and half-correct old-wives tales regarding how to reduce the unwanted noise in your recorded material.

‘Grounding’ in particular is often misused and incorrectly applied, also many with strange beliefs that are held to be true.

It is entirely possible to have a recording studio space with damn near zero AC induced hum and buzz noise. How to do so and what must be done can vary greatly depending on the specifics of the audio equipment, the space, and the electrical system.

The approach and solution must be methodical and holistic. Generally speaking there will be multiple issues contributing to the problem. Resolution will be similarly multi-pronged.

That said, there is a simple ‘trick’ that sometimes helps. Plug all of the interconnected audio gear (and any connected recording/computer gear) into the same power bar. With a single heavy cord back to the power outlet. This forces every piece of equipment to have the ground pin connected to the same electrical ground reference.

If some equipment has only two prong power cord, it may require a separate ground wire run from the metal shell of the power bar to the equipment ground screw. *

* Apple MacBook power bricks sometimes come with a two prong power cord, but there is a grounding nub on the power brick. There are three prong power cords available for Apple power blocks that provide the grounding link.



Power cords should be kept separated from audio and other cables. Power cords should not be coiled, use lazy S shapes, and well away from non-power cords. Try to keep audio cables multiple feet away from power cords, even elevated where possible.

Beyond this, an understanding of the room configuration and electrical environment would be necessary.

If you have a battery powered recorder or amp you can use with headphones and microphone, you can ‘hunt’ for lower level audible hum sources. Some equipment may emit resonant audible sound matching the 60 cycle AC power line frequency. Within equipment sometimes the noise frequency is doubled (typically from rectification in the power supply). This can be a clue, if you hear 120 Hz noise, as to what equipment may be producing it.

Since it is low voltage it is relatively safe to mess with the exposed thin wiring.

Loosen one of the screws and carefully pull the wire(s) away from the screw, so the wire ends are just hanging in the air. Then go check for what doesn’t work anymore. Doorbell would be my guess but it could be something else that runs on low voltage.

When done, reconnect the wires under the screw head and snug the screw tight. If you do accidentally short wires or the tool between the two exposed screws there may be some sparks. While visually surprising, the mild sparking is not dangerous to you nor the transformer.

Thanks folks! I think you're right on the money about the doorbell. I took the button off once to see if I could re-route it for a Ring bell (my doorbell is on the side, unfortunately), and I seem to recall seeing what looked like cat5 connected to it. I looked a little closer last night and I actually think it's Cat3.

So that makes sense. I suspect that the wire going out to the right goes the button and the wire going to the left goes to the actual bell.

I know it's not to my humidifier. I just rewired that today so that it's controlled by my Ecobee instead of the humidistat in the duct, and that's powered through the C terminal on the furnace control panel.

Thanks for solving my mystery!

***edit***

Wow, Google autocompleted a search about moving my doorbell to the front, and there's tons of people looking for advice on how to move it, specifically for a Ring doorbell. Funny. Hopefully someone will have a suggestion similar to my setup...

Definitely clicked on this thread hoping for an insect.

Peter

Here's one I saw at the gas station recently...but I know what it is...

Amen!

Here ya go: a two-fer:

Those doorbell transformers sometimes also power sprinkler systems and or thermostats.

Interesting. I would have thought a sprinkler system would need more power than that. Thermostats make sense though.

But no sprinklers in our yard, and I'm now very familiar with the wiring of my thermostat and HVAC system I had to create my own C wire when I installed my ZWave thermostat years ago. Yesterday I made my own ACC+ wire for my humidifier so I could hand over control to my new stat.

Nah. Just enough to trip a relay somewhere is all it would take.

tanstaafl.

Just needs to power the solenoids in the valves.