Connecting two thermostats ?


Old 01-22-03, 11:23 AM
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Connecting two thermostats ?

I have a two storey house and seem to have a cold upstairs compared to the main level. I noticed the heat loss upstairs is quicker for obvious reasons, but didn't think of that when I positioned the thermostat on the main level. Now I want to either move the old thermostat or add another. I have a gas furnace and there are three wires connected to the thermostat. I assume 1 wire is a common 24 volts, and the other 2 wires go through separate relay closures in the thermostat and back to the furnace to turn on either the heat or air conditioner (which I will never have). If the above is true, then connecting another thermostat in parallel shouldn't be a problem, right? My idea is to have a dual zone control for the house, but in the end I think the upstairs thermostat will do most of the controlling. Thanks for any feedback.
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Old 01-22-03, 11:47 AM
KField's Avatar
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,245
First you need to tell us what the terminal designations are for the wires on your present thermostat. If they are R, W, and B, you can't really get rid of any of them. They would all be used for heat unless changes have been made to the furnace. You understand that what you will be building is not a multizone system, but monster of sorts. I think your vision is for the cooler area to be able to trigger the heating system. At least thats how it will work when finished. I would recommend just putting the thermostat in a cooler location or close a supply register close to the thermostat and you will heat the rest of the house up a little.
Old 01-22-03, 12:22 PM
hvac4u's Avatar
Join Date: Aug 2001
Location: NW atlanta
Posts: 3,147
standard wiring

would indicate one of these wires is 24 volts hot, one goes back to the gas valve or heat relay. the third would go to a relay energizing the fa. adding another tstat is not the cure at all. by keeping the upstairs warm, you will burn up downstairs. get a pro to look at it, you may have a different problem.

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