Woodstove flue temperature
I just finished replacing a woodstove chimney as part of a fire repair job. The old pipe somehow caused a fire in the roof framing, which was caught and extinguished quickly. It burned away enough framing and sheathing that I can't tell exactly what happened, but it may have been originally installed with inadequate clearance, or roofers may have inadvertently pushed it too close when re-roofing. The new chimney consists of about 6 feet of double-wall on top of the stove, transitioning to insulated pipe as it goes thru a floor, finished attic, and roof above (another 12 feet). The stove is a Vermont Castings "Vigilant", a big honker with an 8" outlet. All the pipe is 8" also.
Yesterday I test-burned the stove. It burned OK but it was hard to get a roaring fire using any combination of damper setting, door closed vs. ajar, etc. The owner's firewood is local Doug fir. I split a couple of pieces and metered them in the middle... 22%.
This is quite different than the woodstove in my shop, which is a Morso Squirrel. Tiny by comparison, but I can start a full-on nuclear conflagration in there using a bit of kindling from the scrap bin and fir firewood that's more like 17%. It just burns like hell.
I'd like to give the owner some operating parameters. I suspect the fires are slow-burning and not that hot, and that too much creosote is building up too quickly. There are a variety of stove-top and pipe-mounted thermometers on the market, and it appears that you can use one or both to try to get the optimal burn. There must be other strategies as well.
I told the owner to get some dry firewood for the remainder of the season. The house is leaky enough to provide plenty of air. I know the stove is way behind the times, but there it sits. What say you?
Posted Fri, 02/04/2011 - 08:29
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