120v to 24 heat thermostat control


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Old 12-08-21, 05:46 AM
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120v to 24 heat thermostat control

Upstairs I have a traditional thermostat controlling heat connected to this adapt a stat transformer relay. The relay connects to a 12/2 with just a black and white wire. This goes to an oil burner that for some reason is 120v. My downstairs heat is using an old mercury 120v thermostat.
The adapt a stat outputs 2 red wires that are manually labeled r and w connected to the thermostat.

On the opposite wall I have a traditional thermostat controlling my a/c.

Project was to consolidate to one thermostat, so tried pulling the 12/2 and adapt a stat to the attic and extending the r and w wires from the adapt a stat to the same thermostat as the a/c.

For some reason it isnít working, I measure 20v on the r/w wires but not sure if the relay is working as when I connect the wires the heat does not turn on. Connecting the 120v black and white does turn the heat on.

Question: is the adapt a stat fried? I donít have a neutral and I havenít explored the wiring on the oil furnace yet. Canít seem to find this adapter relay anywhere for sale. In the interim I connected a high voltage thermostat to the 120 v wires.

Any recommendations?

 
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Old 12-08-21, 10:36 AM
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Welcome to the forums.

Those adapt-a-stats were fairly obscure. I haven't seen one in years.
The strange thing is that unit should require three wire power hookup..... a neutral.

It sounds like it's no longer working.
You can replace it with a modern substitute.... the Aube RC-840T-120
It does require a neutral connection. Line in, switched out and neutral.
Aube RC840T-120
 
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Old 12-13-21, 04:23 PM
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Thanks

So I only have a black, white, and ground wire. White is basically my load and not neutral. I did order that part but wasnít sure if it would work as I have no neutral to power itís transformer. I saw they had a model without the transformer but would take too long to ship. So instead I bought a transformer and a 24v coil contacter at the local electrical store. First I pulled all the wires up to my attic. Then I connected the com wire of the transformer to one end of relay and the other hot wire to R of the thermostat. Then W from the thermostat to the other end of the relay. Then I connected the white and black wires 120v wires to opposite side of the relay contacter.

It is working nicely, but I needed a large junction box for it to fit. I am wondering now if I had been able to use the aube 120v device just without R and neutral? Or if I needed the non transformer version of the aube -

https://www.supplyhouse.com/Honeywel...-o-Transformer

also wondering what that adapt a stat was doing to be able to function without a neutral? Must be some kind of power stealing from line and load to create 20v for the thermostat?
 
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Old 12-13-21, 04:46 PM
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The piece you linked to is a 24v relay. It doesn't generate any voltage.
It's labeled W and C. It would be labeled R and W if it was internally powered.
You'd need to supply it 24vAC from a power source.

I would have told you purchase a fan center if I knew what you were doing.
There are dozens to chose from...... just an example.
 
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Old 12-14-21, 12:26 PM
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that device looks pretty cool. i actually have another high voltage thermostat downstairs. Thanks for this!

So this device takes two high voltage wires, just a line and load? It does not require a neutral? How would the transformer be powered in my case. As an FYI what I had done for upstairs was use a transformer, i used a wall wart plugged into a separate circuit and that powered a regular relay that just connected my line and load. It just happens that the wires are white and black.

thanks again
 
 

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