Placement of OAK

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New Member
Jan 25, 2021
Sebago, Maine
I've decided to vent my pellet stove using 4 inch pipe through the wall, with a 3-4 foot rise inside before passing through the thimble. I also want to use that outside air intake, but not sure how far to place it from the vent. I noticed that some dealers have a thimble that also provides a intake line, which would make installation simple as I'm starting from scratch, but not sure if the air supply should be farther away from the exhaust vent.

Another option, would be to vent directly horizontally through the wall and then attach a 3-4 foot riser outside, which perhaps then would make the vent+oak thimble useful. Is it better to have a rise outside than inside?
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Minister of Fire
Oct 7, 2012
Northwest Lower Michigan
There are differing opinions on this, but I prefer to get the venting directly outside, then a cleanout tee, rise, and outlet. That way when you clean it, the junk stays outside. From the outside I can push my brush through the inside pipe, and turn on my exhaust fan to blow it out as the brush knocks it loose.

Some people prefer the rise in the house, because there’s a little more heat off the pipe that gets saved. Or for example a basement install, you have no choice.

I would put the oak directly to the outside. But high enough where you’re not having it blocked by snowbanks or whatever. This may or may not be an issue, but I it should be some distance from the end of the exhaust. That way you’re pulling solid fresh air and not air diluted by exhaust.


Minister of Fire
I see that Duravent (I think) has a dual thimble with the FAK (or OAK) is it's termed here running in the ambient air space around the venting pipe. They say it preheats the combustion air. I call phooey on that. You want the intake (outside air) to be as cold as possible coming into the burn pot. Reason is, the colder the intake air, the more dense it is.

I notice a marked increase in burn quality when the ambient air outside is below freezing coming into the burn pot versus warmer air when the ambient is above freezing.

I want a separate intake not a siamesed one. I get frost on my intake air pipe all the time btw.