Relationship between chimney draft and height

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by dafattkidd, Oct 11, 2013.

  1. dafattkidd

    dafattkidd
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 11, 2007
    Messages:
    1,688
    Likes Received:
    319
    Loc:
    Long Island
    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.
     
    Collapse Signature Expand Signature

    Helpful Sponsor Ads!





  2. oldspark

    oldspark
    Expand Collapse
    Guest

  3. Jags

    Jags
    Expand Collapse
    Moderate Moderator
    Staff Member

    Joined:
    Aug 2, 2006
    Messages:
    17,139
    Likes Received:
    5,858
    Loc:
    Northern IL
    Temps sound good. Back to staring down the chimney.::P
     
    Collapse Signature Expand Signature
  4. mellow

    mellow
    Expand Collapse
    Resident Stove Connoisseur

    Joined:
    Jan 19, 2008
    Messages:
    4,437
    Likes Received:
    594
    Loc:
    Salisbury, MD
    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.
     
    Collapse Signature Expand Signature
    Woody Stover likes this.
  5. oldspark

    oldspark
    Expand Collapse
    Guest

  6. Sprinter

    Sprinter
    Expand Collapse
    Minister of Fire

    Joined:
    Jul 1, 2012
    Messages:
    2,384
    Likes Received:
    528
    Loc:
    SW Washington
    Collapse Signature Expand Signature
  7. #32 brenndatomu, Oct 11, 2013
    Last edited: Oct 11, 2013
    brenndatomu

    brenndatomu
    Expand Collapse
    Minister of Fire

    Joined:
    Aug 21, 2013
    Messages:
    1,985
    Likes Received:
    551
    Loc:
    NE Ohio
    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...
     
    Collapse Signature Expand Signature
  8. Woody Stover

    Woody Stover
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 25, 2010
    Messages:
    7,376
    Likes Received:
    2,105
    Loc:
    Southern IN
    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.'
     
    Collapse Signature Expand Signature
  9. #34 dafattkidd, Oct 11, 2013
    Last edited: Oct 11, 2013
    dafattkidd

    dafattkidd
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 11, 2007
    Messages:
    1,688
    Likes Received:
    319
    Loc:
    Long Island
    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.
     
    Collapse Signature Expand Signature
  10. mellow

    mellow
    Expand Collapse
    Resident Stove Connoisseur

    Joined:
    Jan 19, 2008
    Messages:
    4,437
    Likes Received:
    594
    Loc:
    Salisbury, MD
    He has a liner, he just put insulation at the top and bottom instead of the whole thing.
     
    Collapse Signature Expand Signature
  11. Woody Stover

    Woody Stover
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 25, 2010
    Messages:
    7,376
    Likes Received:
    2,105
    Loc:
    Southern IN
    Collapse Signature Expand Signature
  12. Woody Stover

    Woody Stover
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 25, 2010
    Messages:
    7,376
    Likes Received:
    2,105
    Loc:
    Southern IN
    OK, gotcha.
     
    Collapse Signature Expand Signature
  13. oldspark

    oldspark
    Expand Collapse
    Guest

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

    Woody Stover
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 25, 2010
    Messages:
    7,376
    Likes Received:
    2,105
    Loc:
    Southern IN
    I don't see an actual minimum flue height figure listed....
     
    Collapse Signature Expand Signature
  15. oldspark

    oldspark
    Expand Collapse
    Guest

  16. brenndatomu

    brenndatomu
    Expand Collapse
    Minister of Fire

    Joined:
    Aug 21, 2013
    Messages:
    1,985
    Likes Received:
    551
    Loc:
    NE Ohio
    And flue sized correctly for the stove...

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

    Woody Stover
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 25, 2010
    Messages:
    7,376
    Likes Received:
    2,105
    Loc:
    Southern IN
    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.
     
    Collapse Signature Expand Signature
  18. begreen

    begreen
    Expand Collapse
    Mooderator
    Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    60,491
    Likes Received:
    7,634
    Loc:
    South Puget Sound, WA
    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.
     
    Collapse Signature Expand Signature
  19. oldspark

    oldspark
    Expand Collapse
    Guest

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

    Woody Stover
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 25, 2010
    Messages:
    7,376
    Likes Received:
    2,105
    Loc:
    Southern IN
    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.
     
    Collapse Signature Expand Signature
  21. Bluerubi

    Bluerubi
    Expand Collapse
    Burning Hunk

    Joined:
    Nov 26, 2012
    Messages:
    140
    Likes Received:
    49
    Loc:
    Auburn, NH
    Collapse Signature Expand Signature
  22. oldspark

    oldspark
    Expand Collapse
    Guest

    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.
     
  23. oldspark

    oldspark
    Expand Collapse
    Guest

    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.
     
  24. oldspark

    oldspark
    Expand Collapse
    Guest

  25. dafattkidd

    dafattkidd
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 11, 2007
    Messages:
    1,688
    Likes Received:
    319
    Loc:
    Long Island
    So what if this does work? How do I connect a 4 foot section of Class A to a liner?
     
    Collapse Signature Expand Signature

Share This Page