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clarnp49 12-03-2007 10:39 AM

2 furnaces 1 thermostat
This is kinda of my house from hell, it used to a multiple family, we have converted it to a single family (cut some walls out). In doing so we also plan in the future to put in a central source of heat in the basement with ductwork. Right now there is 2 furnaces of equal BTU, same model and fuel source just on opposite sides of the house. I am hoping that someone can tell me a cheap way to start both furnaces at the same time when it's time to warm up the house.

I want to do this because I have noticed that if one runs the other doesn't and the warm air warms up the side that called for heat, then it cools down from the other side not being warmed up and starts the other furnace which it just seems they battle all the time to keep the consitant temperature.

I have 2 thermostats, 2 furnaces and different ductwork in the attic( that doesn't help get heat to the floor either).
I want 1 thermostat, 2 furnaces and different ductwork that run at the same time outputting the same amount of heat equally throughout the 1200sqft house that is one level.

mrkool 12-03-2007 11:02 PM

I am doing a job with 2 furnaces and 1 thermostat right now.
I had to by a furnace "Twining Kit" to make them both use 1
You see, you can't use 2 transformers with 1 thermostat, that's the problem.
So, you either get/buy the "Twining Kit" or remove one transformer.
now with one removed, the one left might not handle the load of the
other furnace, but my guess is it will, if it's just a furnace and not A/C also.

Sounds easy hey? well it is as long as you know how to do it.

But I have a question, you say 2 furnaces in a 1200 sq ft house?
Are they real small? must be, for you can heat 1200 sq ft with 45,000 btuh,
depending on how tight it is of course.

You maybe able to find a wiring setup online if you have time.


s0lidgr0und 12-03-2007 11:35 PM

We had a building similar to this at my last job. Somehow they were used in sequence depending on demand. The second one almost never had to turn on, but the building was always warm.

mrkool 12-05-2007 08:12 PM

That's what's happening here, only the #1 furnace comes on even on the coldest days, the #2 never fires up and both of these furnaces are 2 stage heat with variable speed blowers, so their gas bill will be cut in half.

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