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6 inch chimney out of 8 inch flu

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Brandon, Feb 23, 2013.

  1. Brandon

    Brandon New Member

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    I'm looking at a stove with an 8 inch flu, what would the draw backs be to using a six inch chimney instead of an 8 inch?

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  2. webby3650

    webby3650 Master of Fire

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    Well first of all it's against code, so if you are getting it inspected, it won't pass. If you reduce the flue size, most stoves will smoke out very badly every time you open the door. Some stoves only needed the 8" flue for open door viewing, and can be reduced down. What stove are you looking at?
  3. Hogwildz

    Hogwildz Minister of Fire

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    There may be some members on here with a similar set up. Maybe they will add input.
    How tall is the chimney?
    If I remember correctly a smaller stack will draft better then an oversized stack.
  4. Brandon

    Brandon New Member

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    its a nashua
  5. begreen

    begreen Mooderator Staff Member

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    oldspark had/has a Nashua. Tell us more about how the stove will be connected and the chimney.
  6. wkpoor

    wkpoor Minister of Fire

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    I've owned 2 Nashua's over the yrs. Very good stove that will really rock the heat. I had mine plumbed into a 6" chimney and still had to put a damper on it.If your chimney is tall and drafts well it won't be a problem at all. From stove to cap for me is 41'.
    The negatives for me were relatively short burn times compare to new stoves. Mine could only be loaded E-W ( other models are N-S) and logs were retained from the door by 1/2" rods.
    Its a 500lb steel stove with a unique smoke path that worked very well at giving off loads of heat. A testament to its durability is my bud now has it heating a large shop and he runs it basically wide open at all times. Usually when I'm over there its at 900+ stove top with the fan on high. Running it at that level requires alot of wood.
  7. leoibb

    leoibb Member

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    as far as my experience goes it will draw quicker taking it from an 8 to a six. ive done similar my self and was surprised what a difference it made. all the 8 inch flue collars on stoves get reduced to a six liner anyway a meter up the chimney , mostly i think to save money no regs here sayin it cant be done ,
  8. begreen

    begreen Mooderator Staff Member

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    That is not a flue, that's an industrial stack.
    BrianK likes this.
  9. begreen

    begreen Mooderator Staff Member

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    ????, maybe in the UK but not here in the states. Our maximum firebox sizes are usually significantly greater than Europe's.
  10. Brandon

    Brandon New Member

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    Well from what I can tell it's the larger of the two wood stoves they built, measurements are supposed to be 36x36x24 and will take a 27 inch log. As for the chimney it will come out of the back of the stove and 90 up toward the celing then 90 again to go out the basement wall then 90 again to go up the back side of the house. I'm not sure how long the runs inside the basement will be but the chimney attached to the back of the house shoulde be 15 to 18 feet long from the T support bracket to the stack cap. I might have to put an offset in the chimney to get around the eve and the gutter, I measured it and theres not enough room to go thru it and come out the roof. Thanks for the info guys.
  11. begreen

    begreen Mooderator Staff Member

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    Given those parameters I say don't do it. There are too many things going against a successful install: basement install (possible negative pressure), choked down stove, 3 90s in the smoke path, average height chimney. Consider selling the Nashua and getting an affordable modern big stove like the Englander 30NC with a 6" flue or go 8" all the way and eliminate one 90 turn by connecting with a pair of 45s and a diagonal connector.
  12. Brandon

    Brandon New Member

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    To tell you the truth I didn't know that you could 45s in stove pipe, and I haven't bought the stove yet still weighing all my options. I dont want to buy a new stove because I just don't have that much to work with. I was hopeing I could use 6 inch pipe to save a few bucks if it could be done safely and still work properly. I'm want to do this to help with the heat bills next winter, having total eletric with an average bill of 350 to 400 a month in the winter really stinks.
  13. Brandon

    Brandon New Member

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    Why would the stove being in the basement create a possible negative pressure problem? Are you talking about back puffing or smokeing out when the door is opened to clean out the stove and or load with wood?
  14. leoibb

    leoibb Member

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    i personally dont think there will be a problem . maybe it may kick a little smoke back when re loading but bein fast helps lol. ive had three stoves now all on the same chimney and same liner. the first two the draw was brilliant could burn happily with door open and no smoke back. the last one i got i cannot open the door without it kicking smoke back. it did state that one cant use these with door open and will fill the house with smoke if i did. i curiosly contacted the makers and the tec chap explained that the longer it takes the fire. smoke to leave the box the more secondaires it will produce there for a hotter fire. . it draws fine with the door closed but re loadin the stove i have to be quick . the other thing is ive a lot more dust in the house from the wood. . apparently a lot of modern stoves will not draw like older ones. sp i guess so long as there is air getting in to the stove and only one way allowed to go out it will go that way ,,
  15. begreen

    begreen Mooderator Staff Member

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    A new stove if you catch it while pricing is good in the next few weeks will not be that much more than a used stove. The savings after that will more than pay for the difference. Call all HD and Lowes stores in your area.
  16. WidowMaker

    WidowMaker Member

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    ===

    I don't understand why one makers 3.5 cu. ft stove needs a 8" pipe and another maker get by on a 6" pipe.
    I have personnally run an 8" stove on a 6" pipe for many years, with no issues... This was prior to the EPA
    stove, but can't beleive that would make a diff...ymmv
  17. mellow

    mellow Resident Stove Connoisseur

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    Depending on the stove some run 6" or 8", mine has an 8" exhaust but is certified to be run on 6" with a supplied adapter. From the way it was explained to me the size of the door is how they rate the exhaust size.
  18. begreen

    begreen Mooderator Staff Member

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    The flue collar size is the call of the stove maker. Most 3 cu ft stoves these days are 6" collared. FWIW, there is a major design difference between older stoves and new ones. Old stoves pulled their air in through a variable intake. Simple. Modern stoves with secondary reburn run the air up a duct (to preheat) to a secondary manifold. It takes stronger draft to pull the air through this manifold system.
  19. Brandon

    Brandon New Member

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    I didn't realize that those stoves were that cheap. But I don't believe that one of those stoves will be big enough my basement is 2000 aq. ft.. My hope is to heat the basement and to let the heat rise to help heat the up stairs, I don't expect to totaly heat the whole house with a wood stove in the basement but I would be happy if I could cut the eletric bill 100 to 200 dollars a month in the winter. I seen on another thread that basement wall could act like a heat sink and absorb the heat put off by the stove. I can kinda see that theaory but I'm not totaly sure about it.
  20. begreen

    begreen Mooderator Staff Member

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    If the basement is uninsulated it about a third of the heat can get sucked out the cement walls. That combined with a big old stove could turn you into a locomotive fireman.

    How many sq ft total in the house? It sounds like you might want to look at a wood furnace instead.
  21. Brandon

    Brandon New Member

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    Total sq. ft. about 3900 give or take can't remember off the top of my head. I'v thought about a wood furnace as an add on to me eletric furnace but have heard that they can be over heated and burnout pretty easy. Also wasen't sure how well a wood furnace would heat the basement with part of the direct out put of the furnace going up stairs, just not sure.
  22. begreen

    begreen Mooderator Staff Member

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    Yes, a furnace can be overfired, but so can a stove. You have a big barn that is going to need some significant btus. A furnace is one option that could work well. Another option is one stove per floor.
  23. jaunty.Joe

    jaunty.Joe New Member

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    Hi everyone, my name is Joe. About 5 months ago, I started working at The Chimney Sweep in Bellingham, Washington. I finished my apprenticeship on the truck and have moved into an office role. I've been browsing the forum for a little while now, but haven't posted yet, so here goes my inaugural post:

    It seems like a couple more questions have popped up since the thread started, but I wanted to address the original question about 8" flue collar and 6" chimney. I do not know anything about the OP's particular woodstove (Nashua brand stoves seem to have a relatively small digital footprint), but here is some information on flue undersizing:

    http://www.chimneysweeponline.com/houndersiz.htm

    Always go with what the manufacturer certified the unit with, and when in doubt, check the owner's manual. I hope this helps.
  24. leoibb

    leoibb Member

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    some interesting reading on that site , not sure it stacks up tho . ive seen small stoves with 8 inch collars and then bigger fires with six inch collars the design of each stove was same size box no magical making involved so i wander.
  25. begreen

    begreen Mooderator Staff Member

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    Congrats on the new job Joe! Couldn't ask for a nicer crew to work with. Just watch out for Sweet Child if you have chocolates. Try to hang on to them and you may get injured.

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