2

I just bought a house and there are two transformers in the garage. I'm trying to figure out what they do. The house was built in 2014 and located in San Mateo, California.

I suspect one of them is for the doorbell (since there must be a doorbell transformer somewhere). I'm guessing it's the one with two cables (one for the button and one for the chime).

I have no idea what the other one (the one with yellow tape) is for. What I do know is that it is hot, so it must be powering something. (The blue one is slightly warm, but definitely not hot.) Any idea what this could be for? It's not for the alarm system (I already identified the alarm system's transformer) and I don't think it's for the furnace, since it is not nearby.

I'm also not sure how to disconnect either of these transformers. At first I thought it was an ordinary outlet/plug. I pulled and it didn't come out. Then I noticed that it can twist. What kind of connection is this? and how do I "unplug" them?

I'm going to try disconnecting the wires to see what stops working. But I need to turn it off first via the circuit breaker. How do I verify that it has been disconnected since there is no direct indication that it is or is not connected?

transformer with 3 cablestransformer with 2 cables

UPDATE: I got a multimeter. The one with yellow tape and 3 cables is 14.7VAC and the blue one with 2 cables is 20.2VAC. I identified the correct breaker, but it also took out the lighting in the garage…

Improve this question
6
  • Do you have a voltmeter with an AC setting?
    – Harper - Reinstate Monica
    Commented May 25, 2021 at 1:34
  • @Harper-ReinstateMonica I just ordered one.:-)
    – Thomas Steinke
    Commented May 25, 2021 at 1:39
  • I bet they are both 16v transformers and the blue one isn't hooked to anything anymore.
    – dandavis
    Commented May 25, 2021 at 6:22
  • @dandavis Second one could power an always on low-voltage circuit somewhere. Could even be a doorbell (with the button having separate wires going to the buzzer).
    – Tonny
    Commented May 25, 2021 at 14:01
  • These transformers are more than meets the eye!
    – RonJohn
    Commented May 25, 2021 at 14:44

3 Answers 3

Reset to default
5

One of them (top picture) is your door bell, and the second one could be the garage opener, sprinkler controller, or low voltage lighting of some sort. Typically, there is an electrical box behind it and it is 120v. You can use ether multi-meter or electrical tester like this to determent if the wires are hot or not and shut one breaker at the time. Sometime there might be a label in your service panel for those.

Improve this answer
5
  • Since there are 3 cables going to the top one I would guess a door-bell with 2 buttons (are there 2 doors or a drive-way gate and a door ?) or a single button door-bell that rings 2 buzzers.
    – Tonny
    Commented May 25, 2021 at 13:58
  • @Tonny there's only one doorbell button that I am aware of. The only entrances are the front door and the garage.
    – Thomas Steinke
    Commented May 25, 2021 at 16:35
  • I've never seen a garage door opener that needed a separate transformer like that, and this would be an odd place indeed to mount a transformer for a sprinkler control. Low voltage lighting I could see. Maybe...
    – FreeMan
    Commented May 25, 2021 at 18:12
  • Garage door probably would have it's own power supply/transformer build in but sprinkler controller, if the low voltage wires for the valves are in the garage (mine are), it is very possible to have it there. It's very hard to tell by the provided pictures where exactly they are located
    – IgorK
    Commented May 25, 2021 at 19:05
  • Could also be thermostat, if the heating system is old enough not to have its own transformer; that would typically be 24v. Probably not old phone power; Telco favored plug-in wall warts for those
    – keshlam
    Commented Jun 30, 2023 at 17:57
0

Well the low -voltage one is probably for your Solar cell and evening lights. Garage lights and Lighted address number plate. It seems that they run between 16.0 to possible 18.0 Volts. Should be closer to sixteen though.

Improve this answer
0

Re disconnecting: If you want to remove them (and their parasitic load) completely, turn off the breaker, remove the faceplate, disconnect and cap/insulate the 110VAC supply writes, cover with a blank faceplate, then finally turn breaker back on. You probably want to have the blank faceplate on hand before you start, and ideally some wire nuts or equivalent in case someone did something ugly when connecting this and you can't just use the existing wire nuts as caps.

The reason they rotate a bit is probably related to how they're mounted to (a hole in) the faceplate. Electrical equipment inherited some things from gas lighting, and hollow threaded tube is frequently used for mechanical connections, with wires run through that. Or there might just be one screw holding it from inside, though that begs the question of where itts power wires would be.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.