Chimney size

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TStreet

New Member
Hearth Supporter
Feb 9, 2008
4
Southern Indiana
I am installing a small wood furnace in my basement. It was made by an Amish metal shop and is very heavy built. It is a little bigger than a standard wood stove. The fire box in 12" wide, 24" long, and about 18" high. The firebrick is 9 1/2" tall. The flue outlet is 8". This seems to big to me and want to know if I can use a 6" chimney. I am planning on using Dura Vent insulated pipe. The flue will run through the main floor, and out the roof. Total flue not including stove pipe will be about 18 feet. Any suggestions? I noticed the new woodstoves at rural king are about the same size and they use 6 inch. Thanks for any advice, Terry
 
General rule of thumb is to never reduce further than the outlet size unless it specifically suggests it in the manual.

How old is this thing? Does it even have any sort of UL or equivalent approval? I would check with the local building inspectors to make sure its even going to be legal to install this thing.
 
Its about 10 years old. It is very well built. I used it in my pole barn at our last residence and it did well. I would like to put wood heat in the house for suppliment, and back up heat. I am installing in my basement. It is built out of 3/16 in steel, with an outer jacket the same size, and a squirel cage fan for the blower. I was going to plumb it into by ductwork and put a thermostat on the blower. I really feel the 6 inch is plenty, but wanted some others input. Thanks all.
 
Well, there are a couple factors at play. In general, the reason for the larger flue (in your case) is that the stove may very well pour smoke out the door when you load it. That (IMHO) is the reason for the larger flue on this model.

The other issue is chimney capacity, which related to two things - chimney height and chimney size. The taller the chimney and the larger the cross-section, the more BTU it can handle.

The bottom line in your case is this - if you had an existing masonry chimney that was a little small (7x7), then you might have some reason to compromise and slightly reduce the flue size...as long as the BTU capacity matched up.

But, since you are starting from scratch AND have a relatively short chimney, I would suggest using the matching size.
 
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