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Fisher Knock Off - Install In 8" Clay Thimble, Masonry Chimney

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Scout_1969, Nov 5, 2010.

  1. Scout_1969

    Scout_1969 New Member

    Joined:
    Sep 29, 2010
    Messages:
    23
    Loc:
    VA
    I am helping someone install a Fisher knock off stove and would like to get a little help. I've tried to do some research here and elsewhere to guide me. But I still need to clarify some things for the conditions and material availability.

    Conditions:

    > Chimney is about 5 years old with little use and has been cleaned.

    > 7X11 clay flue liners and an 8" clay thimble through concrete foundation wall

    > Stove is in basement

    > No interior framing/combustibles between wall and stove, at slightly over 18" from wall.

    > Stove has a 6" flange to attach stove pipe to welded into the top.

    > Chimney seems to have a very strong draw

    Our thoughts:

    > Use 8" single wall pipe inside thimble, sticking 3/8" into 7X11 liners to keep creosote from coming down and into 8" pipe. Extend 8" to inside of foundation wall, seal with furnace cement.

    > Use 8x6 increaser, with 6" to stove with just one 90 degree bend and a damper

    > Run pipe with crimped ends towards stove

    > Run pipe so seams are not at bottom of horizontal stove pipes so as not to be in creosote's path

    > Place three screws per joint and seal with furnace cement

    > Place damper in vertical portion of stove pipe

    Questions:

    > Is this thimble connection good or is there a better method?

    > Increasers available locally are concentric, shouldn't they be eccentric/offset so creosote would flow on bottom and not get damed up at the 8x6 transition?

    > 8" crimped X 6" female increaser could be crimped on the 6" side to maintain the correct flow, is there a way to take the crimp out of the 8"?

    > 6" flange out of stove fits closer to going inside of stove pipe than out. Should we put an extra pointed crimp on the stove pipe to get it inside, to keep the crimps toward the stove?

    > Furnace cementing the joints won't hurt anything?

    > The damper goes in the vertical portion of the stove pipe, correct?

    Thanks in advance.

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  2. Scout_1969

    Scout_1969 New Member

    Joined:
    Sep 29, 2010
    Messages:
    23
    Loc:
    VA
    Other options:

    > I could use 8" through thimble to 90 degree bend and convert to 6"

    > Or just go to the stove and reduce/increase right at the flange.

    I'm thinking about the creosote flow, but would this have an effect in performance etc.
  3. Scout_1969

    Scout_1969 New Member

    Joined:
    Sep 29, 2010
    Messages:
    23
    Loc:
    VA
    Can anyone shed some light on this?
  4. webbie

    webbie Seasoned Moderator Staff Member

    Joined:
    Nov 17, 2005
    Messages:
    12,379
    Loc:
    Western Mass.
    I think that long list in that format is tough to address all at one time!

    I will start by addressing the wall pass through or thimble.
    First of all, if this is relatively close to the ceiling (or to the wood plate which sits on top of the foundation) you would have to be careful. In such a case, a short length of double wall insulated 6 inch pipe mike make a better wall pass through. Even if you have the proper clearances on top, you might consider single wall rigid stainless to cement into the crock and/or wall since it not rot out.

    There is also no harm in stepping down to the 6 inch inside the crock using that double insulated pipe - or using the 8 to 6 adapter in the wall.

    Crimped ends should always run downward - or toward the stove. A crimped end should go down inside the flue collar in most cases.....sometimes you have to recrimp it, etc. to fit.

    A lot of decreasers are either tapered or three piece, either of which might give a better flow than a two pice one.
  5. summit

    summit Minister of Fire

    Joined:
    Aug 22, 2008
    Messages:
    1,903
    Loc:
    central maine
    do everything you listed and itll work fine
  6. Scout_1969

    Scout_1969 New Member

    Joined:
    Sep 29, 2010
    Messages:
    23
    Loc:
    VA
    Thanks guys. I may go with the single wall increaser/pipe for this season and see how it goes.

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