I’m very happy to say my house is 100% grounded as far as outlets and up to code on GFCI for Kitchen, Bathrooms and outside outlets.
The outlets testers cost nearly nothing and are the easiest things to use.
I have one. Several, actually. One of them even sends a signal down the line and there’s a contactless probe that makes a tone when put near another line/receptacle on the same circuit. Very useful for my old house.
Not directly related to this thread, just a weird thing in my house.
I think the doorbell transformer is attached to the furnace. On the furnace is an electrical box with a standard light switch in it, which is used to cut power to the furnace. Attached to the box is a transformer exactly like what is pictured earlier in the thread.
I know the thermostat also runs on low voltage AC, but I thought that was fed from the furnace’s internal power supply. I could be wrong, and this is for the thermostat. Maybe at some point I’ll be bored enough to disconnect a wire from the transformer, and see what stops working.
If the thing on the furnace is not the doorbell transformer, then I have no idea where the doorbell transformer is.
That transformer is for powering thermostats.
It was a very common design in the past.
IIRC, you could also have a separate (24V) transformer to power a whole-house humidifier triggered by the furnace.
ETA: my doorbell transformer says “NuTone” (the doorbell manufacturer) on it (click on the pic to see the full monty):
That is very possible. The old furnace had the transformer on the switch; another transformer that was connected to the furnace power supply or wiring, which sat on the floor inside the furnace, and a third transformer that also sat on the floor inside the furnace; but wasn’t connected to anything. I do not know the story behind that.
The new furnace just has the one connected to the switch, I think.
Now I’ll have to look when I get home.
Does your house get warmer whenever somebody comes to the door?
I tested the transformer the easiest way I know how. I disconnected a wire, and observed what lost power. The instant I pulled the wire off, the feed from my doorbell went down. I put the wire back, and after a minute or so, the feed returned. I guess I could have walked upstairs to check the light, but that seems silly.
So to the OP, your doorbell transformer might be on your furnace, or in your fridge, or under the dishwasher. Who knows?
As for electrical noises, I think I’ve told this story before. We heard a buzzing noise in the bedroom. It also sounded electrical, but no idea what it was. I noticed the cat was staring into an electrical outlet, so I got down on the floor and looked at the outlet, and there was a blue glow from arcing in the outlet.
Well, color me surprised.
BTW, you are aware that you have Aluminum wiring, right?
And, that it’s an ENORMOUS fire risk, right?
Not to worry you unduly, but the chance of a house fire is something like ten times greater with aluminum wiring than with copper.
ETA:
I was wrong - it’s 55x!
Dangers of Aluminum Wiring | Prevent Fire Hazards at Home.
Citing a company that rewires houses is iffy at best as a cite to rewire your house.
That said, aluminum wire is indeed a fire hazard and especially for DIYers. It is most dangerous going into outlets not designed for aluminum and every place aluminum and copper are twisted together. There are special caps that reduce this problem. Usually purple in color.
Rewiring a house is very expensive and disruptive.
As I recall though, aluminum wiring is a much lower fire hazard than laptop batteries, candles, smoking, plug in air freshners and #1 cooking.
Additional worse hazards, fireplaces, cheap or overloaded electrical cords, dryer lint screens.
Space heaters use to be high on the list, but have generally improved a lot.
MY house has aluminum wiring, so I am experienced with it.
When I bought it, I spent quite a bit of money having each junction box opened and the wire ends terminated in a UL-approved system (“CopAlum”).
And, for the risk, well here’s the quote, from a “disinterested party”:
According to the U.S. Consumer Product Safety Commission, homes with aluminum wiring are 55 times more likely to have at least one outlet connection reach “fire hazard conditions” such as hot receptacles, electrical sparks, and charred materials.
Given how old aluminum wiring is in US housing today, I’d suggest that it’d be smart to carefully inspect every connection involving aluminum wiring. You’re probably going to find at least one growing (or already fully grown :yikes:) problem.
I’ll also suggest that if your home is wired in copper but is also that old, the same inspection is not a bad idea. You might find nothing, but you might find something.
Me, too. After you said they used to use external transformers for thermostats, I thought that must be what it was for. Who would put a doorbell on a furnace?
Oh yeah. The house is a mix of aluminum and copper. Sometimes it will change mid-circuit.
Yep, that is the number I was aware of. I replaced all of the copper only receptacles and switches with aluminum compatible ones, and pigtailed in other places. Supposedly that brings the risk down to 5-10 times as bad a copper. That was about 13 years ago.
That’s what I used for pigtails, but are not considered adequate anymore. One of me near term plans, possibly this summer, is to have everything pigtailed with alumiconn connectors. If done properly, and I’ll hire someone to do it, that should bring the electrical fire risk down to parity with copper.
CopAlum is the other option instead of the AlumiConn. If installed correctly both are completely effective. The big difference is CopAlum is more expensive, and more difficult to install. The ironic thing is, my dad spent most of his working life at AMP, the makers of CopAlum. Except that he retired 25 years ago, he could have gotten me as many as I needed for free.
The counter-argument to the AlumiConn, is that electricians certified in CopAlum are going to be very experienced in dealing with aluminum remediation. AlumiConn does not require certification, so can be used by any random apprentice.
Somebody who wanted to use one transformer for two compatible loads: doorbell and thermostat.
Or who just wanted a convenient accessible 120v source in a service area, not a decorated area, of the house. Better in plain sight tagged off the furnace than at a hidden junction box in the attic.
But yeah, we all get trapped in categorical thinking that becomes misleading when we encounter the work of a raging DIYer or a super lazy super cheap-ass.
Paraphrasing some wise philosopher whose name I forget:
It’s not the things we don’t know that trip us up. It’s the things we know that tain’t actually so.
Transformer hum is a common thing. Lots of them do it new. Many develop it over time as the plates delaminate or the hum damping system fails. The chance of this type of failure causing a fire is quite low. It’s a problem with the mechanical side, not the electrical.
The only realistic reason to find the transformer so it can either be replaced or taken out (if you want to use an alternate doorbell system).
I don’t know that I can 100% agree with you here. It really depends on what’s making the doorbell transformer hum.
And there are underlying causes that have near zero potential to cause greater issues, but there are also underlying causes that may speak/lead to larger issues:
A transformer is literally just two coils of wire around an iron core. That’s all there is to it. The voltage is stepped up or down according to the ratio of how many turns each coil has. If the 120v side has 10 times as many turns as the other coil, the output voltage of the second coil will be 1/10th or 12 volts AC.
You can make a transformer using a solid iron core, but usually they use stacks of thin iron plates laminated together to reduce eddy currents which would reduce the efficiency of the transformer.
While the article that @DavidNRockies linked to does list a lot of different causes of transformer hum, by far the most common cause is that the laminated plates start separating and becoming loose as they age. The looser they get, the more they vibrate, and the louder the hum gets.
The coils can also loosen up over time and can contribute to some of the humming.
The hum from delaminated plates can be annoying, but it’s usually not a problem unless the transformer is getting hot, in which case it needs to be replaced.
By the way, the fancy shmancy technical term to google is “transformer magnetostriction”.
ETA: By the way, don’t touch a transformer or anything else electrical unless you really know what you are doing. Worst case is you kill yourself.
Transformers hum “because they don’t know the words.” I’ll see myself out…
Sparky for 36 years.