So I asked the city bout my chimney

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vwboomer

Member
Hearth Supporter
Dec 5, 2008
84
wisconsin
I emailed the city inspector asking if there was anything special the city would require if I would decide to reline my existing chimney. I stated that it's oversized and would like to get it to a proper dimension. I may or may not have forgotten to mention the new furnace?
The response
"gave me your e-mail about chimney liners. We adopt the National Fuel Gas Code and it states that “Chimneys shall be built and installed per NFPA 112 and lined with approved clay flue lining a listed chimney lining system or other approved material that will resist corrosion erosion softening or cracking from vent gases at temperatures up to 1800 F.” If you can find a lining system that is listed for solid fuel you can install it per the labeling and listing. "

Of course NFPA 112 is a typo.
Since I haven't found a copy of NFPA 211 and a brief check of online retailers didn't list the temp the flex liners were rated at, are they typically rated at least 1800?

I can go with 6" if I do not insulate. Otherwise I would have to go 5.5" or oval which would cost a lot more. It's my understanding that since it will be inside an existing chimney, the issue of 2" (?) clearance to combustibles is irrelevant since there will be an air gap, and then the masonry chimney? The chimney is about 24' from the top to the furnace hole, and is interior with the attic portion open to whatever attic temp is.

Heating season is comin and Menards still hasn't put the furnace on sale, but I can at least get started on ordering chimney parts.
 
I would get the documentation for the lineryou want to use and the Listing spec, and the furnace spec/install manual. Then go have a talk with the inspector.

On a furnace I don't think I'd worry as much about insulating. You may have a harder time lighting it, but once lit the chimney should draw.

Yes - a 2" air gap to combusibles is not an issue since you're inside the masonry chimney.

All the best,
Mike
 
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