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I have a normal central heat a/c system in the house.(35x35 two story farm house) We also have a wood burner that sits right beside the hvac in the basement. currently the wood stove blasts 120 deg heat straight up into the main floor of the house and keeps it plenty warm. The upstairs not so much. When we bought the place the wood stove was piped into the hvac unit and required us to run the hvac blower to get the heat up stairs. I didnt want to run that blower, plus the two on the wood burner, all the time. So i moved to just blowing into the main floor.

Here's the ?. There are(i think) 3 wires on the thermo for the hvac system. One of them, doesn't it turn on JUST the blower, when the switch on the thermo is switched? In other words, on the thermostat there is a switch that says "fan-auto or fan-on" It turns the fan on all the time, without calling for heat. What I want to do is control that one wire with another thermostat right beside it, only put it on the heat circuit of the sencond thermo.

Plan is to route the wood burner back into the plenum of the hvac system. Wont be hard to do since it was there before. Then the wood burners two fans will blow into the plenum and ducts and get modest heat into ALL the house. Then, the second thermo would call on the hvac blower to turn on and off to the preset temp and force the wood stove heat up. (without adding the propane burner into to the mix)

Can I do the thermostats this way? Thanks in advance
 

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putting t-stats right next to each other is a bad idea. Shit, even putting two t-stats in the same room is a bad idea. The reason is that they will fight each other.

Why not put a t-stats upstairs and have it only control the blower that feeds the upstairs and keep it in auto mode?

I would comment more but your description is vague.
 

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Discussion Starter #3
putting t-stats right next to each other is a bad idea. Shit, even putting two t-stats in the same room is a bad idea. The reason is that they will fight each other.

Why not put a t-stats upstairs and have it only control the blower that feeds the upstairs and keep it in auto mode?

I would comment more but your description is vague.[/QU

I dont think they will fight each other, becuase the wood heat is going to take the primary heating load. Im only asking the second(new) tstat to turn on the central units fan to help push the wood heat up into the system. It would turn on and off just like if i were heating the house normaly. The wood heats fans are not strong enough to push the heat throught the entire system. Oh, and the duct system is 90 years old, there are NOT up/down stairs zones, its all on or all off.

Help with were I'm being vague so I can try to explain it better! I'll take pics of units downstairs when i get home tonight. thanks
 

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I dont think they will fight each other, becuase the wood heat is going to take the primary heating load. Im only asking the second(new) tstat to turn on the central units fan to help push the wood heat up into the system. It would turn on and off just like if i were heating the house normaly. The wood heats fans are not strong enough to push the heat throught the entire system. Oh, and the duct system is 90 years old, there are NOT up/down stairs zones, its all on or all off.

Help with were I'm being vague so I can try to explain it better! I'll take pics of units downstairs when i get home tonight. thanks

Ok, now im really confused.

You said this is a farm house, so does the unit only control the A/C and the heating aspect is handled by the wood stove?

Im guessing this means when you are in "heat mode" and the room with the t-stat senses a low temp it will just turn on the blower motors to pump in heat from the stove until it warms up?

But then you state another motor pumps heat into the unit, from the wood stove, which is the only way to get it upstairs. And you are having trouble getting heat upstairs?

The simplest way to do that is to have all the blower motors come on at once, but you dont want that to happen? So they next easiest way is to get another tstat setup upstairs to control the second blower motor, but you dont want that either?

Then only other way would be to set up a light switch or something hooked to a blower motor upstairs. So when yo uflick it on, it pumps heat into the ducts leading upstairs.

Putting two t-stats next to each other, controlling the same unit, will only make your system worse.
 

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I'm gonna say yes you can run a second tstat to turn on only the hvac fan.
not sure about...the hvac calling for heat/fan the same time the wood system is also calling for fan
I did not stay at a holiday inn last night:homer:
 

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Yes you can do that. You will need two wires to run over the the semiconductor stat. You will hook up one wire to the R terminal on the old stat and a wire to the G terminal on the old stat. You will run those two wires to the new stat and hook the R wire to the R terminal on the new stat and then you will hook the other wire to the w terminal on the new stat.

This will cause you to supply power to the fan when there is a call for heat. If you have other questions you can PM me and I will give you my number and I will walk you through it.
 

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Why not run 1 stat that has room for multiple stages?

Stage 1 is blower motor only, stage 2 which would only come on if the wood stove wasn't maintaining temp would fire off the furnace.
 

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Discussion Starter #9
Yes you can do that. You will need two wires to run over the the semiconductor stat. You will hook up one wire to the R terminal on the old stat and a wire to the G terminal on the old stat. You will run those two wires to the new stat and hook the R wire to the R terminal on the new stat and then you will hook the other wire to the w terminal on the new stat.

This will cause you to supply power to the fan when there is a call for heat. If you have other questions you can PM me and I will give you my number and I will walk you through it.

this is the info I was looking for, only trouble is there isnt an R terminal in either t-stat! pm sent, thanks a bunch
 

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if you run the blower in the wood furnace and its blowing into your hvac system without your hvac system blower running there is a possibility of your hvac blower starting backwards. normally when we do one like this we use a backdraft damper to keep air from circulating backwards through the hvac system.
 
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