Wiring Google nest with no C wire


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Old 12-06-22, 06:30 PM
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Wiring Google nest with no C wire

I am trying to install a google nest thermostat in my old milwaukee thermoflo furnace; model 1203-B10. I do not have a current C WIRE hooked up at the thermostat. There are 3 wires run to the thermostat, but only 2 are used. Could it be as simple as connecting the unused wire to the TR spot? Would this make it a "c wire" that I could hook up the spot for the C wire on my nest?




 

Last edited by PJmax; 12-06-22 at 06:45 PM. Reason: resized pics
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Old 12-06-22, 06:35 PM
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Welcome to the forums.

I had previously resized your pics for the board.
I need to know the three colors of the wires to the thermostat.
 
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Old 12-06-22, 06:56 PM
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red, white, and blue run to the thermostat. The White is hooked up to the TH spot. The red goes to a wire nut that is connected to a load wire. The blue is unused


 
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Old 12-06-22, 07:15 PM
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Very good.
Your blue wire will connect to the blue wire from the transformer.
The letters in yellow are the system function.

 
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Old 12-07-22, 04:11 AM
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Should I connect these blue wires with a butt connector? Or use a spade connector and connect that to the the TR terminal?
 
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Old 12-07-22, 09:14 AM
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Butt connectors aren't commonly used for these connections. I would say wire nut would be best, if not then spade connector.
 
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Old 12-07-22, 09:20 AM
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Could I just connect the 2 wires, or do they both have to go back on the TR terminal?
 
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Old 12-07-22, 10:22 AM
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You can connect them any way that is convenient.
Personally.... I would replace the TR crimp with both wires.
 
 

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