Millivolt Thermostat Installation


Old 07-18-05, 01:26 PM
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Millivolt Thermostat Installation

I will be replacing a natural gas, gravity flow furnace with a new unit.

The thermostats are the millivolt variety as no electricity is used on these furnaces at all.

The thermostat is run by two wires, (red and white).

* Is there any correct order that these two wires need to be installed on the furnace?

The current thermostat attachment is that the white wire is attached to the "W" on the thermostat and the red to the "rc". At the furnace the red wire attaches to the "aux" connection at the furnace that is bridged to the themocouple and the white to the remaining screw.

Any information would be appreciated.
Old 07-18-05, 05:03 PM
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It sounds like you are replacing furnace with like kind. Millivolt system. You said the tstat now is connected to W & RC that is not a millivolt tstat unless it stated so on package and has had anticipator adjusted for millivolts. The new furnace should be clearly marked where to attach 2 tsat wires. Probably one wild wire and a terminal. Actually sounds like you have it covered. I don't know offhand what the aux means for a millivolt system unless it is for a spill switch.
Old 07-19-05, 03:09 PM
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The new furnace is clearly marked where the two wires attach. One goes to a screw connection on the gas valve, and the other gets wire nutted to a lead that runs to a block flue shut off device and then back to another screw on the gas valve.

*I just don't know if I should attach the red or white wire to the gas valve or visa versa. The directions with the wall furnace just have one wire going to each location without specifying color.

I'm actually wondering if it even makes any difference. I actually think that this furnace would turn on just by dead shorting both ends of the thermostat red and white wires together.
Old 07-19-05, 03:43 PM
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Millivolt thermostat

I really should not matter which wire goes where. A thermostat is just a switch.
Old 07-19-05, 03:58 PM
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Thanks Grady. Those were my thoughts as well, but comforting when confirmed.

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