Would it be OK to reduce a 8" flue on a Newmac forced hot air wood furnace down to a 6" which is my existing class a chimney? Thanks Chris
8" flue to 6" flue
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Redox
Minister of Fire
Maybe, but it will probably void UL listing or something equally serious. Do you really want to take that chance on something inside your home?
Chris
Chris
webbie
Seasoned Moderator
Definitely not OK in most cases. A furnace like that would have a large firebox and the reason for the 8" is to vent the heat and the BTU. An 8" chimney has about 60% more capacity than a 6" chimney. In any case, it would be against codes and the listing.
If the chimney was especially tall and the BTU input of the furnace was known....then it is possible that a conversation with the factory might produce something.
The furnaces are rated 100,000 BTU output, which probably means about 200,000 input max.
Looking at a common boiler chimney chart:
http://www.engineeringtoolbox.com/chimney-area-heat-load-d_1132.html
you see that a 6: (31 sq in) is rated for up to 119,000, while an 8" is closer to 200,000.....so that is pretty much your answer.....being no.
If the chimney was especially tall and the BTU input of the furnace was known....then it is possible that a conversation with the factory might produce something.
The furnaces are rated 100,000 BTU output, which probably means about 200,000 input max.
Looking at a common boiler chimney chart:
http://www.engineeringtoolbox.com/chimney-area-heat-load-d_1132.html
you see that a 6: (31 sq in) is rated for up to 119,000, while an 8" is closer to 200,000.....so that is pretty much your answer.....being no.
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