No power at Thermostat


Old 02-25-06, 07:40 PM
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No power at Thermostat

I wanted to change a Bryant Digital Thermostat to a battery backup Hunter unit. The issue I have is after I made the switch, I have no power at the thermostat. I did not turn off any power when I started this process which I know is dumb. Did I shortcircut the wiring? I can not figure out what I did wrong or how to fix this now. I checked the circut breaker and nothing was tripped. I put the Bryant back in exactly as before and still no power to the old thermostat after numerous attempts. Any suggestions on how to fix this? I have many zones in my house and all are still working, only this thermostat has no power.
Old 02-25-06, 08:45 PM
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If it is a low voltage T-stat you could have smoked the transformer.
If it's line voltage check the breaker again , ALL the way off then ON
Old 02-25-06, 08:46 PM
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If you didn't turn off the power, chances are you burnt out the transfromer, or some newer equipment will have a low voltage fuse on the board.. Remove the blower door, and see if there is a low voltage fuse on the board.. Most of them looks like the fuse you find in your car.

FYI, I hear lot of bad lucks with Hunter t-stat, I'd suggest the Honywell.
Old 02-26-06, 06:18 AM
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[Two threads on same question merged into one. Please respond here.]

bobbycrossman11 wrote:
"I have many zones in my house and all are still working, only this thermostat has no power."

It would be helpfull if you describe in detail what type of system you have.
Old 02-26-06, 08:12 AM
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I have a forced hot water system and an air conditioning system. The air conditioning system was put in last year, the heat was original with the house and is 12 years old. There are two transformers by the gas boiler and another what looks like a transformer with two connections coming to it. One of those connections is for the heat in this room. Oddly, the other one comes from a connection of all the other zones. I tried moving the nonworking heat wires on the transformer to open connections and the power still did not turn on. I assumed that since the other thermostats are still getting power, the other open connections on this transformer had to work.

The three transformers dont look the same. One is a plug type transformer and the other two are the same. The two same transformer units are interconnected. These seem to support the mass of wires coming from all the other thermostats.

The air conditioning unit and this one zone is connected to the nonworking thermostat. Every other zone: basement, 2nd floor and 3rd floor are working fine.

The heat is your typical two wire connection, the ac is a four wire. I can not find where the AC wires tie to a transformer. I have looked at the electrical box, reset all fuses, and none were tripped.

I tried using only the heat wires to the thermastat and still no power. Any ideas?

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