# Can I run my central heating fan and use wood stove together?



## paulestuart (Jan 16, 2010)

Hey,
My installer thought it would be a bad idea to run the wood stove and central heat fan at the same time due to the fact that they would be competing for air.  I have trouble understanding this.  It seems that the fan is throwing out as much air as it is taking back through the return registers and shouldn't affect the wood stove.  What are your thoughts?
Thanks,
Paul


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## webby3650 (Jan 16, 2010)

I run my fan every night that is below 30 °F. In my set-up it really evens out the heat, my registers in the outlying rooms will be warm to the touch in the morning.


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## Archie (Jan 16, 2010)

I think you'll be OK.  I do it all the time.  I believe that a central HVAC system is techically a "closed system" so it works with the air it has, air return = air supply.  On the other hand, the wood stove will require a net draw of air out the chimney, but it shouldn't be a problem unless your house is very airtight.


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## begreen (Jan 16, 2010)

It won't be competing for air, but it may lose a lot of heat trying to move room temp air. 

There are as wide variances in heating systems as there are houses. The majority of ducting systems tend to lose heat, making running the system fan expensive and less than effective. However, if the heating system is well insulated, sealed, and doesn't have long runs through cold spaces, then it sometimes does work.


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## fossil (Jan 16, 2010)

The central heating system should be "pressure-neutral" in terms of your home and the outside atmosphere.  Even if it's a modern unit with air exchange...taking in fresh make-up air and expelling "stale" air, it shouldn't compete for air with your woodstove if you run the system while the stove's burning.  The bigger question is, will doing so get you the results you're hoping for?  The answer is, it depends on your home and how it's all put together.  Some folks report good results, others not so good.  Quite typically, the air ducts associated with a central system are run through unheated attics above the living spaces or unheated crawl spaces beneath the living spaces.  The ducts are typically insulated, but only marginally.  So, you turn the central system to "Fan Only", hoping to distribute warm air throughout your home, only to find nothing but cold air coming from the supply registers in the remote rooms, because what little heat there was available was lost in translation (so to speak).  Depends on your house.  Sometimes it works OK, most times it's a bust.  Give it a try...whaddya got to lose other than a little heat?      Rick


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## paulestuart (Jan 16, 2010)

Thanks for the help, i think I'll go ahead and run the fan.  I can deal with losing some heat due to my old, poorly insulated ducts (house fixer up project #127, currently at #6)


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## mcgvr83 (Jan 27, 2010)

I would like to add my 2 cents to this topic. Not only does it work with my system but I have made modifications that allow us to use the central heating system with thermostatic control. Its a little technical but if you are handy with basic wiring, it shouldnt be an issue.

It wont add wood or anything like that but if the house temp drops below what we have the thermostat set to, it runs just like the gas furnace, until the fire goes out...then the gas system takes over if it gets cold enough. We're usually not gone more than 8-10 hours, so this hasnt been an issue.

The wood furnace and the central furnace fans both come on when the thermostat calls for heat and both stop when the set temp is reached. There are a few HVAC controls to buy but including a 250' roll of thermostat wire. Ive still got less than $200 in the upgrade. 
Ive had it running for almost 3 weeks and the temps in the house have never less than 68. (It has been in the single digits outside). It was 71 inside when I got home today and 18 outside.

As far as the cold air return issue. I have installed a screen door in the doorway that leads to the basement. (keeps the cats out of trouble) The warm air goes up thru the ducts and since cold air falls...the heat pushes the air back down the stairways to the basement. Simple but effective.

I dont have time now to give all the details but if anyone is interested I could draw up a diagram and list the parts etc.

Stay warm!


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## fossil (Jan 27, 2010)

OP's talking about a basic woodstove, I believe..._not_ a woodburning furnace.  No place to hook up any sort of thermostatic controls that might work in concert with an installed conventional central system.  Rick


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## laynes69 (Jan 27, 2010)

Wood furnaces work well, but the poster has a stove and not a furnace. They are completely different when it comes to heat distribution. As far as your woodfurnace is concerned, if the blower is wired to come on and off due to the heating demand of the thermostat its wrong. You want your blower to run all of the time, or whenever there is a call for heat on the fan limit control, not thermostat. The thermostat should control a forced draft, or servo on a damper. With a good fire in a woodfurnace and no blower, things can easily overheat and cause problems. Especially if duct clearances weren't followed to combustibles.


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## golfandwoodnut (Jan 27, 2010)

My furnace guy recommended keeping the fan on all winter and summer, with or without the wood burner.  It is a high efficency furnace with a variable speed fan (Lennox), he said the electric use would be neglicable and it would help eliminate cold spots, keeping the air moving.


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## mcgvr83 (Jan 27, 2010)

Sorry I missed the stove vs. furnace thing...

I mentioned that I upgraded the system...None of the factory installed safeties were disabled. The limit control still works to keep the wood furnace from over heating when the house is warm enough. 

It just seemed silly to have to push the manual switch in to get the blower to run long enough to move any heat into the house. The fan doesnt know if I'm standing there turning the switch on an off or if a thermostat is closing a fan relay which has the same result. When the fan center relay closes, it switches the limit circuit "off" and the fan comes on until the house warms up. At that point, the relay opens and the limit switch circuit operates normally...on at 150 off at 100, hi limit 200.

I thought of every possible scenario before starting this project. It is about as close to perfect as it can be.


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