5.5" Reline for a 6" Rated Appliance

caucapon Posted By caucapon, Sep 3, 2010 at 7:32 PM

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  1. caucapon


    Jan 4, 2008
    Last year we installed a 5.5" flexible stainless steel liner in our exterior clay tile lined chimney. While the hearth opening is large, surprisingly, the 5.5" liner just fit. A 6" diameter pipe would have required extensive and permanent modifications that we were unwilling to make. Both appliances would be vertically vented with only one forty-five degree dogleg through the damper area. The chimney is twenty feet high.

    This year we have an opportunity to purchase either a used Hearthstone Phoenix (60,000 btus) or a Regency Classic large insert (75,000 btus). Both of these are factory equipped with 6" flues. Many contemporary stoves I've seen utilizes a 6" outlet regardless of output rating or firebox size. Because of legal considerations, I am reasonably sure that no manufacturer is going to endorse using even a slightly smaller pipe. However I am curious just what the practical consequences of doing so might be.

    Just off the top of my head, I suspect that if all else is reasonable, this minor reduction in pipe size would not have a dramatic effect on function or safety. While I know that there are other extraneous considerations such as being in compliance with insurance mandates, etc., I am really only interested in gaining some understanding of the likely practical and functional results of such an installation.

    Thanks to anyone who might respond.
  2. Rob From Wisconsin

    Rob From Wisconsin
    Minister of Fire

    Nov 20, 2005
    East-Central Wisconsin
    Was your flue 6" x 10"??
    Ours is and we would also like to re-line it to improve draft.
    A 5 1/2" is the only cost effective solution (ovalized systems are very expensive).
    I believe Simpson-Duravent make a 5 1/2" to 6" increaser - Northline Express sells it.

    Will a 5 1/2" liner work for you?
    Probably just fine, especially with the length of flue you have.
    You may run into problems occasionally if you have a proportionately large woodstove door (smoke leak upon opening).
    Using an Outside Air Kit should fix that.
    Let me know how the liner works for you....

  3. BrotherBart

    Hearth.com LLC Mid-Atlantic Division
    Staff Member

    Nov 18, 2005
    Northern Virginia
    I have one twenty one foot outside masonry chimney and one thirty foot+. Both lined with 5.5" flex liners and they both draft like vacuum cleaners. It is my contention that they run hotter and maintain a stronger draft. When I measured the hole in the top of my Englander 30-NC inside the flue collar the hole was exactly 5.5".

    That six inch thing has to be a compromise for lots of stoves.
  4. btuser

    Minister of Fire

    Jan 15, 2009
    Principality of Pontinha
    I've got a lopi Freedom insert. I don't know what the BTU rating is but its the biggest they make. 2.9CF firebox, which is really what tells you how big it is. BTU ratings are pretty haphazzard. Well, my original hole was 8x10 clay or something like that. I heard a rumor that 6" may barely fit, but a 6" insulated definately wouldn't. The chimney is exterior, shaded, and only about 16' tall. I went with the 5.5" and insulated it. When I tried to stuff it down the flue it was just too tight, so I "ovalized" it a bit by leaning my knee into it gently the entire length. Not a full oval, but enough to get it down the chimney.

    So now I've got an oval peg in a rectangular hole. All said and done I've probably got a little bit under a 5.5" insulated liner for a large insert that is never fired more than 75% and is often under 50%. The draft is more than adequate at full blast (on the rare occasion I fall back asleep). I feel better that it's insulated. Chimneys are not a standard construction part, they're closer to a recipie. Draft, lenth, temperature, insulation, material, and how you burn are all factors that contribute.
  5. Chargerman

    Feeling the Heat

    Oct 22, 2009
    SW Wisconsin
    My stove has an 8" flue. In order to get through one bend in my chimney I had to ovalize about half of the pipe to around 6" on the narrow side. I just bought 8" flexible liner and ovalized it with my own homeade ovalizer. I made it with two rolling pins and a 2x4 frame with adjustments for different diameters. It didn't take long to build and worked like a charm. It saved quite a bit of money but 8" liner is expensive either way.
  6. Fsappo

    Minister of Fire

    Apr 9, 2008
    Central NY
    Any decent stove designed to work on a 6" flue should be fine. Do eeet, do eeet now, get in the choppa
  7. yep you'll be fine - we make quite a few 5.5" liner's
  8. Will

    New Member

    Sep 22, 2010
    Central MA
    [quote a
    Post a New Reply
    uthor="TheHeatElement" date="1283562607"]yep you'll be fine - we make quite a few 5.5" liner's[/quote]

    Hi - We Have a 25 ft. chimney centrally located in our house, we are installing a Clydesdale 8490 insert that specifies a 6" chimney liner. The chimney liner supplier is suggesting one half of an inch diameter reduction with make little-to-No difference in performance over a 25 foot length. Is this true?
    NOTE: The chimney was built 7 yr.s ago with a 8 x 12 ceramic sectional liner.

    REASON: They (The chimney liner supplier) suggest we use a 5.5 in.x 25' liner rather than a 6 in. diameter liner because the inside dimensions of the ceramic clay liner is 6.5'' x 11'' in.s and the outside diameter of the 6'' liner is 6.25 inches resulting in a liner that will be very difficult to install.

    For code, safety or performance reasons should we be concerned if we install a 5.5 in. Dia. liner which is 25 ft. long for a Hearthstone Clydesdale insert? (which is spec'd to provide up to 60,000 BTU's)?

    Thank you in advance for any assistance anyone can provide - we are trying to get the insert installed A.S.A.P.
    It's getting colder and we are starting to burn some oil!

    Thanks, Wil
  9. rdust

    Minister of Fire

    Feb 9, 2009
    I have 27' of 5.5" liner and my stove works just fine. It's a tall chimney so I'm sure that helps, when it's single digit cold it drafts too well imo, it's hard to damp it down for a slow burn when it's that cold.
  10. laynes69

    Minister of Fire

    Oct 2, 2006
    Ashland OH
    I have a 5.5 rigid liner on our furnace rated max at 104,000 btus and theres no problems with the system, other than an overdraft on a 32' chimney.
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