questions about wood furnace attachment
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Hi,
I need to get some advice from someone who knows this stuff; I’ve had lots of suggestions over the years from people with peripheral knowledge and have not gotten my problem solved.
First, does anyone know of a forum about wood heat installation or wood furnaces specifically? When i google I have to sort through a million sites devoted to outdoor wood furnaces with hot water heat. This is not my situation.
What i’ve got is a good sized wood furnace built by Royal Co. of Elroy Wisconsin. This sits next to my gas forced air furnace.
When I bought the house, the previous owner had routed the duct from the wood furnace down and around the back of the gas furnace to the cold air return intake. His theory was that the heated air would be filtered. It didn’t seem to provide much heat. I had a few different HVAC guys tell me that was not a good way to do it, it should have been directly attached to the plenum of the gas furnace, so I had one of them fabricate ductwork that sits on the wood furnace and takes it straight through to the plenum.
It still doesn’t really heat very well. It definitely helps but I don’t think it’s right. Wouldn’t you think a really good fire would provide a ton of heat? I will admit that the house is a challenge–it is an 1870’s farmhouse with a couple poorly insulated crawlspaces and it is large and spread out from a couple additions but I’m mainly talking about heat output here. Shouldn’t it feel really warm coming out of the vents?
My experience with wood heat in the past is that even free standing stoves crank lots of heat.
there are some weird situations involved with the fan system/thermostat/switch setup too, possibly contributing to this problem. Another problem is that the HVAC guy who built the ductwork did not put a damper on it so when the gas is on and the furnace blowing, it blows back through the duct into the wood furnace! I’m positive that is a serious problem and the only solution I’ve come up with is to manually slide a flat piece of sheet metal at the plenum connection to block most of it.
So with all that, does anyone have some good perspective? Sorry to be long winded.
Scott
Replies
Look at this owner's manual (it's for Yukon, but the principle is the same). #2 (parallel) installation is what you're looking for.
http://www.yukon-eagle.com/pdfs/jack.pdf
http://logancustomcopper.com
http://grantlogan.net/
It's like the whole world's walking pretty and you can't find no room to move. - the Boss
I married my cousin in Arkansas - I married two more when I got to Utah. - the Gourds
Seeyou,Thanks very much. That unit is almost identical to mine and the pdf shows a similar installation to what i have now, except that they show a return air duct surrounding the blower on the back of the unit. Mine is by itself, it gets air for the unit from the basement environment. That's not fantastic because it's not only the leakiest and most poorly insulated area of the house but also draws some air through the crawlspaces...I know that contributes to my overall problem.does anyone know how much help i would get from installing a return duct to the blower on the back? Also, should I try to bring some kind of pipe up to the fan that provides the air for combustion? It's a squirrel cage type thing on the front of the unit. I had considered doing that along with a separate pipe to supply the gas furnace but haven't gone ahead with it.
I've installed several of these add-on beasts (had one myself for several years) and the easiest and most cost effective way is to use 12" rd off the shelf galc duct off the existing return to a small plenum at the intake on the add-on unit. Not optimum, but I think your problem is you've got to pull some air out of the living space to push more in.http://logancustomcopper.com
http://grantlogan.net/
It's like the whole world's walking pretty and you can't find no room to move. - the Boss
I married my cousin in Arkansas - I married two more when I got to Utah. - the Gourds
It would be good if you could sketch your installation, including returns and rough sizing and lengths. . Then more definitive answers may be added.
There are a number of duct pressure drop web sites, but dont have a reference handy.
i could sketch it but not sure how to show it online, i don't have a drawing program that i know how to use! could make a drawing and scan it I guess.One thing that maybe could be a factor is the ductwork my HVAC guy used to run the heat from the wood burner to the furnace is 8" x 18" and it occurred to me that may be on the small side but then again, maybe not.