Flue Size

[velvetfoot]

I an estimate last night to install another flue in an existing chase in a colonial house with 2 other flues (basement oil boiler and 1st floor insert). The estimate is based on an 8" diameter duratech pipe. I thought, "the larger size will give me flexibility". Then, this morning I did a little survey of the requirements of a bunch of different wood boilers and, in the 25kw class, 6" seems to be the rule! !There are some 6.3", so I assume 6" would work. Looking at a couple pellet boilers, 5" seems to be the rule there, so I figure, 6" would be acceptable. I know for a fact there are a lot of wood stoves that use a 6" flue. For a pellet stove, I'm not so sure. It'd be a drag if a 4" liner would be needed.

Two notable exceptions are the Econoburn ebw-100 which requires an 8" flue.as does the EKO Orlan from 25kW to 60 kW..

Anyway, it seems that 6" seems to be the norm and I'm going to get the chimney guy to revise his estimate. Nice to save a little money too.

Comments?

 

[maple1]

Only 1 from here. Even though it has an 8" breach, my unit specs a 7" flue, and that's what I had. So I reduced from 8" to 7" right outside the boiler. It's natural draft. The comparable induced draft model (Vedo 37) specs a 4" minimum.

For whatever that's worth.

Maybe that was more than one...

 

[NE WOOD BURNER]

what is the price difference?

 

[Fred61]

Although my 25 has a +- 8 inch take off I plug into a 6 inch class A at the ceiling and my draft is more than adequate. I think EKO uses a standard output size for their exhaust as well as their hot water supply off the top of the boiler.

 

[Vizsla]

There are lots of factors, and ways to control draft besides diameter. Length,height, dampers. And don't forget to make cleaning it easy, as this will be more likely to be done rather than put off if its difficult.