6" vs 8" interior flue for 36" oven? Tools, Tips and Techniques Discuss 6" vs 8" interior flue for 36" oven? in the Pizza Oven Design and Installation forums; I realize the general spec is 6" for 36" and 8" for 42", and I realize that going too small ...

[kebwi]

I realize the general spec is 6" for 36" and 8" for 42", and I realize that going too small is worse than going too large...but...would an 8" flue definitely not be too big for a 36" oven? I'm not sure what the risks are. Extra heat loss perhaps? Nonideal airflow?

Thanks.

[dmun]

Lots of us have 8 inch square flue tiles on thirty six ovens, which are even bigger than round ones, and mine, at least, draws like a champ.

[crowtrapper]

I've been using my 42" oven for about 9 months now, and the biggest mistake I made in the construction was using a 6" flue instead of an 8" (it was easily available, and the 8" was going to be hard to get hold of at the time). The smaller flue draws really well but just cannot handle the amount of smoke, particularly when starting, or when the wood is a bit damp, so a lot of smoke goes up the flue OK but a lot also comes straight back out through the front arch opening into the operator's face!
The other mistake I made, although not a big one, was that instead of a poured concrete base supporting a layer of vermiculite and then firebrick hearth, I used a base of AAC panels to support the firebrick hearth. Quick and easy, but not really a good enough insulator, so in spite of having a well insulated dome, I lose a lot of heat through the bottom of the oven and it cools off quicker than I would like. Ah well...next time...