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Advice on flue design please

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Noreng, Aug 3, 2008.

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  1. Noreng

    Noreng New Member

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    I have a wooden house with a brick chimney up the middle (ca. 1925). Currently an oil burner and an ugly old enamel wood burner are attached to it. Those two are going to go and a new wood burner installed (Dovre or Jotul). Obviously the existing flue needs to be checked out, However I could do with some advice on flue design.

    The stove will go directly in front of the chimney. The obvious flue design is a rear exit flue from the stove, horizontally into the stack.

    However I have also been pondering a top exit, with a vertical steel flue for say 1 to 1.5 meters, then a 45 or 90 bend to enter the stack. Seems to me this could have the following advantages
    - more heat into the room from the exposed flue
    - inspection hatch just below the bend to see how things are in there

    with downsides of:
    - greater cost
    - colder gases entering the stack leading to greater buildup?

    Any views on my options here?

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  2. begreen

    begreen Mooderator Staff Member

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    Welcome noreng. Both ways will work. The critical point is to minimize the horizontal run and be sure it is pitched upward towards the chimney at least 1.8 cm per meter. You could use 2 - 45 deg elbows instead of a 90 to improve draft and eliminate the horizontal run. In some cases, like the Jotul F400, the stove might actually work better with the top exit.
  3. fossil

    fossil Accidental Moderator Staff Member

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    A rear exit stove sitting on the hearth in front of (or even partially into) the fireplace, connected to a new liner up the existing flue, would be called a hearth stove, and they can be both effective heaters and real pretty. No boring into the masonry chimney structure. A block-off plate where the (presumably) existing damper is will minimize wasted heat loss up the chimney. A top exit stove sitting on the hearth in front of the existing fireplace with a stovepipe straight up to the ceiling, an adapter installed there, and appropriate chimney pipe from there to daylight is also an option. In that case, your woodstove doesn't use the old chimney at all, and the old fireplace could be sealed completely, either where the damper is, or at the hearth opening. I don't know whether or not this is an option in your home...a lot depends on what's directly above the ceiling where the stove's going to be located. In any case, It's not clear to me whether or not your woodburner and your oilburner actually share the same flue or the chimney structure incorporates two separate flues. You didn't say whether or not the single woodburner is going to replace both existing appliances, or you'll still have two. If you have two, they really should have separate flues. Welcome to the forum! Rick
  4. Noreng

    Noreng New Member

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    Thanks for the replies - I will be more specific.

    The current 2 appliances share the same flue, one in the lounge and one opposite in the kitchen. Both are to be removed.

    There is no fireplace, never has been, just a brick (presumably) stack into which the current appliances outlets go horizontally. The stack continues down into the cellar below where there is a hatch at floor level. Thus the new stove will just sit on a floor plate on the existing floor in the lounge.

    The new stove will use the existing flue and will be the only appliance using it. So my question was just about entering the flue directly behind the stove, or a bit higher after a vertical section. I like the idea of top exit plus 2x45deg elbows.

    Cheers
  5. begreen

    begreen Mooderator Staff Member

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    That's what I had visualized. It sounds like you have a good plan. Be sure the chimney is in good condition, seal off the other hole and enjoy the new stove. What make/model are you considering?
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