Stack Size

[opiejudd]

We are reworking our arch and I'm wondering what size stack we should run on our 30"x8'. It has an 8 inch stack now. I don't think its big enough and in the process I'm adding AOF as well.

Thanks
Ken

[maple flats]

My 3x8 has 12" but many 3x8's have 14", I think even a 10" for a 30" x 8' might fine. I had good draft before AOF and after adding the AOF it was even better. You should realize that the AOF is high pressure, not hi volume. As such, the AOF actually needs less stack diameter than a naturally aspirated arch. When I fire my arch, I even leave the blower on with the firing door or doors open, I still get no smoke nor ashes coming forward out the door. A 10" should be fine if you plan to definitely do the AOF, if not sure you'll get it done before the next season, the 10" is still better than the 8" you now have. Besides, if you need more draft, you can always just add 2-3 more feet in height to get that, and far cheaper than the larger diameter. By the way, may stack (on a 3x8) is 12" x17' (just 1' over the 2 times the evap. length).

[murferd]

When you say your stack is 17 feet, where do measure from, at top of evaporator or top of flue pipe?

[opiejudd]

Thanks Maple flats. We will be upping the stack to 10 inch then. And we will run at least 16ft of stack if not a little more. AOF is high on the modification list.

Thanks
Ken

[maple flats]

I have a 6' tall base stack and 11' of 12' on top of that.