I've a Burnham MPO boiler. I called Burnham, whose technicians
suggest that I take the most conservative approach and line my
existing exterior-wall, clay-lined brick chimney with a stainless
liner to minimize flue condensation.
Should this liner necessarily be insulated as well? Or is the dead
airspace (although somewhat cold due to exterior wall) in the chimney
a sufficient buffer? I know the most conservative answer is to
insulate the liner too, but your experiences would be appreciated as
this insulation would be yet another expense on top of the liner.
Thank you very much for your responses.
If it heats water its a boiler, if it heats air its a furnace, so you
have a boiler from your next post. If its a condensing unit you should
be able to vent through a wall, I dont understand why you need to line
a clay lined chimney unless its falling apart, clay is durable.
Thats why you dont do HVAC. Most chimneys were designed long ago with
a big ol flue to handle those huge gravity furnaces that ate large
amounts of gas when no one cared how little it cost.
Now gas is expensive. People are using furnaces that dont require a
huge chimney. They need a smaller one so the flue gasses dont condense
in the chimney and destroy. Thats why you line them with a smaller
flexible flue or a b-vent flue. Thus, effectively reducing the size of
the chimney and preventing condensation where it doesnt belong.
Things becoming a little clearer now, ransley?
I say again.. Size does matter. That chimney must be resized to fit the
venting requirements. A liner is one way to downsize for modern
equipment needs. Check your local building authority if you don't
have a code book.
Just called them again. They expect stack temperatures of below
350F. Considering it's an exterior wall chimney and (I suggested I
may also have a fresh air duct installed in the future), they once
again recommend a stainless liner to prevent condensation from
damaging the existing chimney. As they're not in the liner industry,
they did not want to officially comment on the specific type, although
the individual I spoke with said he's familiar with the single wall
The double wall stainless liners I'm familiar with would seem like
overkill: they are insulated in between layers and are typically the
type that can be in close proximity to combustibles, like those
metalbestos things. And I do not want to switch to a power vent
Any 3-pass boiler (Buderus, Burnham MPO, etc) experts out there
familiar with or observe a similar stainless chimney liner
What does the installation manual say about it??
What do your local codes require??
What did the local building inspector say about it??
What did your insurance company say about it??
We are not here to do your homework for you.
Thanks for the suggestions.
1. Installation manual says use a liner "if condensation is
observed." Per my earlier post, I called the manufacturer and didn't
get too much advice on what type as it's not their product.
2. I didn't think to check the code! Chapt 8 of Mechanical Code of NY
says to use liner that will resist condensate, and is in accordance
with NFPA31. I'll find NFPA31 and see what it says. Hopefully will
provide guidance on insulated vs. non-insulated.
3. Local building inspector cannot (legally) suggest anything beyond
the building code, so I'll need that NFPA31.
4. I didn't check insurance company. Not sure if they'll even
understand what I'm saying. I'll try.
I have two additional thoughts:
1. if flue gas is cooled too much within liner inside chimney, it may
not create sufficient draft up the 25ft tall, exterior wall chimney.
Is there a way I can estimate if I'll have sufficient draft? Reference
would be appreciated.
2. if flue gas is cooled too much and condensation occurs within the
liner, is it such a big deal? It would just drip down, through the
bottom tee, and into the cleanout chamber. In other words, the system
would work as expected, no?
In the meanwhile, any other suggestions or experience is appreciated.
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