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  1. IPLUMB

    IPLUMB Member

    Joined:
    Aug 18, 2006
    Messages:
    102
    I have a Hearthstone morgan insert with a full reline, Interior chimney so I didn't insulate my flex liner, My question is how hot do you guys think it gets inside my masonery chimney between my top plate and my damper block off plate? I always worry about it,This is my third season with this stove. Thanks always thinking Aaron....

    P.S. I've watched this forum for years but this is my 1st post :wow:

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  2. elkimmeg

    elkimmeg Guest

    Welcome Aron we to know if the lines has spacers. Air space is criticle in figuring out if you have a concern. Also the size of your clay flues would be helpfull
  3. Todd

    Todd Minister of Fire

    Joined:
    Nov 19, 2005
    Messages:
    9,226
    Loc:
    Lake Wissota
    Welcome. Are you talking about your liner temp? Do you have room to put a thermometer on your exhaust if you remove your surround? If so, take a reading and add 50% to it to get an idea. ex: 300= 450. Of course as you go up it will decrease. I know what your saying about being a little worried. Nice to have peace of mind.
  4. webbie

    webbie Seasoned Moderator Staff Member

    Joined:
    Nov 17, 2005
    Messages:
    12,099
    Loc:
    Western Mass.
    In normal operation I would expect the flue tile temperature to be from as low as 150 degrees to as high as 300 degrees. The reason chimneys are tested to such high temperatures is only because of short and hot chimney fires, which can occur when tars on the inside of the pipe (that have built up over time) ignite. Luckily for you , a number of things are in your favor....

    1. A clean burning newer stove.
    2. Stove has controlled air, so even if buildup in pipe ignites, it is limited in terms of air - and therefore temperature
    3. You have a liner within a liner within a chimney.

    In real world situations, I have never run into a relined chimney/modern stove combination where the liner has gotten so hot that it presented a danger to the wood framing which is typically 6" or more from the flue liner interior. In other words, the situations of your type that would worry me most would be:

    1. Older creosote hog wood stoves (pre-EPA).
    2. Chimneys with no flue liner and brick/mortar which is falling apart.

    In other words, short and sweet - if your original chimney was 1/2 decent, you are probably OK....given the basics above, I would feel comfortable with that installation. Consider that up until recently, it was OK to install that stove with no liner at all - just a short pipe through the damper. The liner increases the safety factor by a LARGE amount.

    If, on the other hand, you live in a restored 1820 Cape Cod with original chimney....well, I'd want that liner to be either insulated or have some spacers so it was suspended in the center of the chimney flue....or BOTH.
  5. IPLUMB

    IPLUMB Member

    Joined:
    Aug 18, 2006
    Messages:
    102
    Wow, you guys make me feel better thanks. I'm just a worrier No I have no spacers and my liner touches the old 1975 clay lined chimney in at least one place that I know of, I had to have my insert pulled as far forward as possible so it touches the flu coller adapter to the lintel. Its a 10" or 11" clay tile that is only about 13' tall {ranch}.

    I've never even seen spacers? But I'm usually pulling aluminum liners for Water Heaters.
  6. precaud

    precaud Minister of Fire

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    Loc:
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    That would be "lintel"... lentils are beans...
  7. elkimmeg

    elkimmeg Guest

    I plumb Pulling liners out for water heaters Many here donot know that many of Alum gas liners are only good for 10 years

    Spacers should be used to help keep the pipe as straight and centered as possible. Just like many applications if one does not inform the general public, no one knows they exist. They exist but almost no one uses them. If one read there manfuctures liner installation manual and applied NFPA codes They are required. That air space separation inhibits heat transfere to possible combustiables in close proximity. Short it is a good thing to have
  8. seaken

    seaken Minister of Fire

    Joined:
    Nov 21, 2005
    Messages:
    580
    Loc:
    Shokan, NY
    Since this your third season you must have at least two historical chimney cleanings, right? How much "stuff" was removed from the liner on these sweeps? If your are getting only a little dust (which would be expected if you are getting the most from your modern stove) you are probably not in danger of a chimney fire. The temps inside the liner can range from 150 F to over 450 F in normal operation. These temps are not dangerous, even if there is no air space between your liner, the masonry chimney, and the combustible framing of the house. The danger of heat transfer being too much come when you have a chimney fire. During a chimney fire temperatures can increase dramatically, even as much as 2000 F. That temperature could be a problem if there is no air space between your masonry and the combustile framing.

    So, the key to safety in this case is to avoid chimney fires. If you can't be sure you will always avoid a chimney fire you should insulate the liiner. This is why we, as professionals, insulate the liners. You are going to expect us to install the system in the safest manner. There is no way we can assume there will never be a chimney fire. Thus the insulation.

    Sean
  9. webbie

    webbie Seasoned Moderator Staff Member

    Joined:
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    Messages:
    12,099
    Loc:
    Western Mass.
    I have never seen spacers sold with the pipe, but have made them up in certain situations...just sheet metal with a hole in it or simple brackets riveted to the pipe.

    It is almost impossible that a liner would touch the flue tile for a large area - like many sq feet. - for a number of reasons. First is that it is round...so only a small portion of the exterior can rest against the tile.

    Flex liners are often not smooth on the outside, so they can only contact the clay liner in a limited fashion.

    Sooner or later I will get ahold of the UL test spec so we can all see what they are testing to. As I mentioned before, installing a large rectangular flue liner in such a chimney would put MANY TIMES the potential heat on the flue liner....as opposed to a 6" round. On the other hand, I cannot imagine UL testing every size liner from 3" to 16" in flex and rigid.
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