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8" flue to 6" pipe at ceiling - unsafe?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by la44, Oct 15, 2009.

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  1. la44

    la44 New Member

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    PLEASE HELP! Vermont CASTINGS EXPERTS OUT THERE! I purchased a Vermont Castings Encore non-catalytic stove three years ago. The most recent chimney sweep told me that it is not "up to code." The flue is oval, 8". The collar and pipes leading up to the ceiling are 8". At the ceiling level the chimney pipe becomes 6". All pipes are double-walled. Can anyone help me understand the specifications on this? What is an 'optional 6" flue collar'? A reversible flue collar? Anyway, it is snowing and the stove is dismantled in my living room. Jury is out, along with fire inspector...

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  2. Danno77

    Danno77 Minister of Fire

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    yeah, there are several things that nobody here will argue with. reducing a pipe is ALWAYS a no-no. heat build up, gas build up, whatever may happen, you can be assured that it won't have good consequences to take some 500 degree air that's flowing up the chimney and say "hey, hot air, i know you want to ALL move through here, but instead I can only let some of you go at a time."
  3. greythorn3

    greythorn3 Minister of Fire

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    what about running a 6" wood burner into a 8" chimeny pipe at the ceiling?
  4. Danno77

    Danno77 Minister of Fire

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    wouldn't running into a larger pipe slow down the speed of the gasses and then impact draw? I'm not sure. I bet that going larger up by the ceiling is less of a danger and merely presents more of a problem with draft. I mean, when your chimney empties into the world, it's going from 6" to an infinite sized pipe, so as long as your ceiling is super high and you can good a good draft with it, then it should be fine. If your ceiling is 8' and your pipe is running from the top of the stove, then I think you might have problems.
  5. la44

    la44 New Member

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    Thanks all for your help. I've been getting conflicting opinions on how to fix my problem. The stove calls for 8" pipe from the oval opening. There is an "optional 6" flue collar" that they could install, but wouldn't that prevent safely opening and closing the front doors? I think what has to be done is replace all the stovepipe - from flue to chimney top - to be 8", so that I can safely use the stove, open and close the front doors when necessary, etc. Anybody have a different opinion?

    And if I reduced to 6" flue collar, will that affect creosote buildup right in the stove and overall safety?

    Since the dealer installed everything, I'm trying to get my ducks in a row to have them fix the problem. I want the safest solution. Thanks again for all your help.
  6. LLigetfa

    LLigetfa Minister of Fire

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    Back in the old days when it wasn't against code, we would often reduce an 8 inch flue using an 8-to-7 taper and then a 7-to-6 taper. You cannot argue with code however so if a 6 inch collar is available to bring it up to code, do it. It shouldn't make a difference in your draft and won't cause creosote. Think of the flue gasses as a train. The engine and the caboose both travel at the same speed.
  7. Wet1

    Wet1 Minister of Fire

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    Not if the engine is in the 6" and the caboose is in the 8". In this case the caboose would be dragging ass. :)
  8. LLigetfa

    LLigetfa Minister of Fire

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    The point I was trying to make is that the caboose won't travel any faster than the engine.

    Back in the days when we used tapered reducers, we theorized that hot gasses expand and the cooling gasses shrink as they rose up from the stove, so their velocity increased only slightly as the pipe narrowed. This was to counteract the theory that slower moving gasses in an 8 inch flue slowed as it rose and cooled which caused it to cool more and slow more until it eventually stalled.
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