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chimney sizing question

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by kattpound, Mar 28, 2013.

  1. kattpound

    kattpound Member

    Joined:
    May 17, 2011
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    Loc:
    N.W. OHIO
    My wife and i are considering buying our first house it has a hearth and an old smoke dragon that is supposedly damaged. Long story short the present stove has a 8" stack with a thimble through the ceiling and out of the roof. We are looking at the nc-30 but was wondering if i would have to replace the thimble and double wall 8" above, or just tie into the 8" at the ceiling? I think I know the answer but just want to get more input.

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  2. jeff_t

    jeff_t Minister of Fire

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    I'd give it a shot with a reducer.

    How tall is it?
    Prof likes this.
  3. Pallet Pete

    Pallet Pete Guest

    Kattpound you might find this helpful as well http://www.hearth.com/talk/threads/new-englander-nc-30-owner-install-questions.66300/.

    Good luck
    Pete
  4. kattpound

    kattpound Member

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    N.W. OHIO
    thanks pete
    Pallet Pete likes this.
  5. fossil

    fossil Accidental Moderator Staff Member

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    Ideally, of course, the flue would be the same diameter from the stove collar to daylight. Some folks find that they get perfectly satisfactory performance out of a "less than ideal" installation. Increasing from 6" to 8" piping will result in the flue gases slowing down a bunch where the cross-sectional area of the flue increases. This will tend to decrease draft (and thus stove performance), especially if the total flue height is marginally short. It will also result in the flue gases dropping farther in temperature before they are exhausted than they would if the velocity was higher and circumferential area smaller. This will tend to favor increased creosote condensation/buildup in the chimney piping. There's no compelling reason to not try it...if the performance is found to be unsatisfactory, the remedy will be the same as changing everything to 6" now, obviously some non-trivial $$$. I'm betting that odds are you'll be able to make it work, even if you have to add a bit of height and sweep it more often than you otherwise might. Good luck, and keep us posted. And welcome! Rick
  6. Prof

    Prof Burning Hunk

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    Oct 18, 2011
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    Loc:
    Western PA
    I'd give it a shot too. I was in a similar situation, but my chimney has a 9" liner. I was worried about using a 9-6 reducer, but it worked fine. I have a 22' stack--I think that helped. I have good draft and minimal creosote. Hope it works in your situation.
  7. Joful

    Joful Minister of Fire

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    My 6" stove dumped into an 8" chimney for 18 years. I just re-lined to 6" last year, and am still trying to decide if it really made any difference in draft or performance.

    I think the only thing that can be assumed, is that running 6" into 8" will amplify any creosote problems you may have, due to the slowing of the flue gasses. Burn well-seasoned wood properly, and that should not be a big issue either way.

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