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Gas Furnace: Line the Chimney or Add a Powervent?

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Gas Furnace: Line the Chimney or Add a Powervent? Jonathan Royce 10-01-2006
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Posted by Jonathan Royce on October 1, 2006, 10:56 pm
I recently went through the process of having my 2 flue chimney rebuilt from
the roofline up. I then lined one of the flues with a SS liner for a
woodburning fireplace insert.

The 2nd flue is currently being used by my gas furnace and HWH. I noticed in
the attic that some of the mortar is crumbing on that flue. (This is the
original part of the chimney, not the new part, which is just from the roof
up.) I plan to repoint these sections this spring. After reading some
articles online & in magazines, I think the problem is that my boiler is
causing too much condensation in the cold part of the chimney (in the
attic). This is causing the deterioration of the mortar.

This said, I am thinking of either a) purchasing a power vent and
redirecting the gas exhaust out the side of the house OR b) lining the 2nd
flue with a gas-compatible liner.

The cost seems about comparable ($1000-$1500 if I do it myself).

Any pros/cons to consider?

TIA,
Jonathan
Nashua, NH


--




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Posted by udarrell on October 1, 2006, 11:09 pm
Jonathan Royce wrote:

>I recently went through the process of having my 2 flue chimney rebuilt from
>the roofline up. I then lined one of the flues with a SS liner for a
>woodburning fireplace insert.
>
>The 2nd flue is currently being used by my gas furnace and HWH. I noticed in
>the attic that some of the mortar is crumbing on that flue. (This is the
>original part of the chimney, not the new part, which is just from the roof
>up.) I plan to repoint these sections this spring. After reading some
>articles online & in magazines, I think the problem is that my boiler is
>causing too much condensation in the cold part of the chimney (in the
>attic). This is causing the deterioration of the mortar.
>
>This said, I am thinking of either a) purchasing a power vent and
>redirecting the gas exhaust out the side of the house OR b) lining the 2nd
>flue with a gas-compatible liner.
>
>The cost seems about comparable ($1000-$1500 if I do it myself).
>
>Any pros/cons to consider?
>
>TIA,
>Jonathan
>Nashua, NH
>
>
Only an opinion, - Good idea.
Make sure that the liner will leave it with enough capacity for the
furnace & HWH.
udarrell

--
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(Solving ESP)
http://www.udarrell.com/udarrell-air-conditioning.html

Posted by Brian V on October 1, 2006, 11:12 pm

>I recently went through the process of having my 2 flue chimney rebuilt
>from the roofline up. I then lined one of the flues with a SS liner for a
>woodburning fireplace insert.
>
> The 2nd flue is currently being used by my gas furnace and HWH. I noticed
> in the attic that some of the mortar is crumbing on that flue. (This is
> the original part of the chimney, not the new part, which is just from the
> roof up.) I plan to repoint these sections this spring. After reading some
> articles online & in magazines, I think the problem is that my boiler is
> causing too much condensation in the cold part of the chimney (in the
> attic). This is causing the deterioration of the mortar.
>
> This said, I am thinking of either a) purchasing a power vent and
> redirecting the gas exhaust out the side of the house OR b) lining the 2nd
> flue with a gas-compatible liner.
>
> The cost seems about comparable ($1000-$1500 if I do it myself).
>
> Any pros/cons to consider?
>
> TIA,
> Jonathan
> Nashua, NH
>
>

The flue gases don't touch the brick. There's a clay type liner in there
then surrounded by brick. The brick is structural only. Have it cleaned and
serviced, a decent company will run a camera down there for cracks and
voids.



Posted by Bob F on October 2, 2006, 2:46 am


> The flue gases don't touch the brick. There's a clay type liner in there
> then surrounded by brick. The brick is structural only.

My chimney has no liner. Are you sure?

Bob



Posted by on October 2, 2006, 3:19 am
>
>
>> The flue gases don't touch the brick. There's a clay type liner in there
>> then surrounded by brick. The brick is structural only.
>
>My chimney has no liner. Are you sure?
>
>Bob
>
>

He probably is sure, but he is not correct. Flue liners are required
by many current building codes but go back a few decades or so and
this was not the case. Older houses often had brick chimneys with no
liner, and deterioration was/is a problem. High efficiency furnaces,
which have lower flue temperatures, do tend to make it worse because
of condensation, as some other psoters mentioned. The condensation is
worse than plain water for masonry, because it is slightly acidic,
which is generally harmful to mortar, and possibly the bricks
themselves.
--
No dumb questions, just dumb answers.
Larry Wasserman - Baltimore, Maryland - lwasserm@charm.net

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