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thermostat issue

I am an electrician by trade.

I have a tempstar ntc6075fbai furnace. I want to put in a new thermostat. The voltage at the thermostat is 30v, instead of 24. What could be causing that. ?

(The transformer on the controller board is 24v and it reads 24 volts on the output)

2. On the board, if you measure across the "R" and the "C" terminals, you should get the same voltage at the wall thermostat. If you measure on the board, you might be on a regulated power supply line for the logic circuits. Secondary voltage should be input voltage divided by 4
120v/4= 30v
115v/4 = 28.75v
110v/4 = 27.5

3. Originally Posted by Joe Harper
On the board, if you measure across the "R" and the "C" terminals, you should get the same voltage at the wall thermostat. If you measure on the board, you might be on a regulated power supply line for the logic circuits. Secondary voltage should be input voltage divided by 4
120v/4= 30v
115v/4 = 28.75v
110v/4 = 27.5
Makes sense and is the same thing I've seen in the field. Not sure how he's only getting 24v @ the transformer but 30v @ the thermostat.

Martuuuu, are you reading directly across the transformer terminals or from one side to ground/other point?

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Originally Posted by 54regcab
Makes sense and is the same thing I've seen in the field. Not sure how he's only getting 24v @ the transformer but 30v @ the thermostat.

Martuuuu, are you reading directly across the transformer terminals or from one side to ground/other point?
Directly across the transformer terminals reads 24.

5. Are the thermostat wires and the 120v wires run together?

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