Chimney

billmcb · Post by **billmcb** » Wed. Nov. 19, 2014 8:40 pm

our chimney has an 8x8 flue but only has a 6" thimble we have an EFM 520 will we be able to use the chimney the way it is it also is 34' tall

JeepinPete · Post by **JeepinPete** » Wed. Nov. 19, 2014 9:12 pm

Legally, no.

That being said, I've been running my EFM for the last few seasons with just such a setup. I also have a 30'+ chimney with excellent draft. I have no trouble heating the house with a four teeth feed. If you needed to run the boiler harder, the smaller pipe would not work.

I also set the damper at .06" rather than the recommended .04", my logic being the 6" pipe has a cross sectional area roughly 40% less than a 8" pipe.

blrman07 · Post by **blrman07** » Thu. Nov. 20, 2014 7:47 am

Legally? That is a nebulous word depending on where you live. Can it work? Yes. Will it be optimal? No. Has it been done? Yes. Is it best to change the 6 inch thimble to an 8 inch? I'll leave that to the chimney experts that I am sure will chime in soon.

JeepinPete · Post by **JeepinPete** » Fri. Nov. 21, 2014 9:43 pm

Fair enough, change legally to "By code"

blrman07 · Post by **blrman07** » Fri. Nov. 21, 2014 10:59 pm

Ok I'll bite......which code?