Relationship between chimney draft and height

dafattkidd Posted By dafattkidd, Oct 11, 2013 at 12:21 AM

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  1. dafattkidd

    dafattkidd
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    I generally run my unit pretty hot. 500-700 range is normal. I get spillage pretty much always. I think last year we had a couple of super cold days, and on those days the spillage seemed less. This is when I started considering extending my chimney.

    I also think the offset box contributes to my problem.
     
  2. oldspark

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  3. Jags

    Jags
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    Temps sound good. Back to staring down the chimney.::P
     
  4. mellow

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    You need more draft to compensate for that offset box, a 90 in a chimney takes off 5 feet in overall length, so I would guess an offset box takes off 8 feet.
     
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  5. Sprinter

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  6. brenndatomu

    brenndatomu
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    Sorry, maybe this was already covered elsewhere, but I'm assuming you have a masonry chimney with SS liner? Is it insulated? That would add some draft if it was.
    As to one of your original questions, how to extend your chimney height, again, assuming masonry chimney with a SS liner. They make a top plate that adapts from flex liner to class A pipe. I know I have seen a link to one here somewhere before, maybe someone else can put their finger on it more quickly than I.
    I have no experience with those draft inducer fans, but to me, that looks like a real PITA on a wood burner chimney...
     
  7. Woody Stover

    Woody Stover
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    So you don't have a full-length stainless liner?

    "The chimney must have an acceptable 6" (152 mm) stainless steel chimney liner installed."
    "The 2400 Insert is not approved for use with a positive flue connector into a masonry flue."

    Terminology differs, but what they are calling a 'positive connection' is what I call a 'direct connection,' where the stove connector pipe goes up through a block-off plate, then uses the masonry chimney clay liner tile the rest of the way up. They are saying this is a no-no. I call a liner all the way up, a 'positive connection.'
     
  8. dafattkidd

    dafattkidd
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    I have a 6" liner running from an offset box which is directly connected to my stove. The liner goes up to the cap. Only the lower and upper portions of the liner are insulated.
     
  9. mellow

    mellow
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    He has a liner, he just put insulation at the top and bottom instead of the whole thing.
     
  10. Woody Stover

    Woody Stover
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  11. Woody Stover

    Woody Stover
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    OK, gotcha.
     
  12. oldspark

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    If it is a inside chimney (I think he said it was) the insulation is less of a factor.
     
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  13. Woody Stover

    Woody Stover
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    I don't see an actual minimum flue height figure listed....
     
  14. oldspark

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  15. brenndatomu

    brenndatomu
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    And flue sized correctly for the stove...

    Insulation at the top and bottom only? That is kind of an interesting install, no?
     
  16. Woody Stover

    Woody Stover
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    I gotta believe that the offset box is the culprit here.
    You can get the cheap snap-together black stove pipe at a farm store.

    You won't get as much draft as with a liner, but that's not the issue here.
     
  17. begreen

    begreen
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    Yes, grab a 3 or 4' length of 6" galv. lightweight venting duct, remove the cap and temporarily put it in crimp down. Secure so that it doesn't fall down and light the fire.
     
  18. oldspark

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    A correctly built chimney has a clay liner in it.
     
  19. Woody Stover

    Woody Stover
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    True, but the clay liner is going to have a larger cross-section area, slowing the draft. And according to your previous post, dropping the flue gas temp will slow draft. So an insulated liner will definitely draft better than the clay....
    I don't know if he's got enough room in the clay liner to insulate his stainless liner, but that would have to help. I'm not sure how much it would help, though.
     
  20. Bluerubi

    Bluerubi
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  21. oldspark

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    Inside chimney so insulation may not be that big a deal.
    Chimney is on the short side a little height may be the most bang for the buck.
     
  22. oldspark

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    Getting side tracked here, they used to make a 7 and1/4 round clay liner and yu can go 25% larger with the liner size.
     
  23. oldspark

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  24. dafattkidd

    dafattkidd
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    So what if this does work? How do I connect a 4 foot section of Class A to a liner?
     
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