Small arch AOF

[ecolbeck]

I’m wondering if anybody has done AOF for an arch smaller than 2x6. Is it worth it for something that size?

[mol1jb]

I inquired about this last year. Didn't find much. As far as small arches go it works but the common sentiment was that it adds a lot of complexity to the build or retrofit and most thought it wasn't worth the effort or cost. I personally like the idea. If I end up building my dad a 2x4 over the off season I am strongly considering it.

[RileySugarbush]

The benefit of AOF is to burn the unburned gas after it leaves the proximity of the fuel. In a 2x6 or larger, that burning happens under the flue pan when the air jets vigorously mix in new oxygen. In a 2x4, most of it will occur in your stack as opposed to reigniting at the top of the stack as you may have observed when you really get it going. It won't really help much unless you have a longer pan.

[ecolbeck]

The benefit of AOF is to burn the unburned gas after it leaves the proximity of the fuel. In a 2x6 or larger, that burning happens under the flue pan when the air jets vigorously mix in new oxygen. In a 2x4, most of it will occur in your stack as opposed to reigniting at the top of the stack as you may have observed when you really get it going. It won't really help much unless you have a longer pan.

Interesting. My evaporator has a 45” flue pan. Seems like that would be enough distance given that a 2x6 typically has a 48” flue pan. My rig has a much shorter firebox though, only 18”

[maple flats]

AOF would likely help if the firebox is rather short, but might not be cost effective unless you find an old oil gun for the HP blower. The blower bought would otherwise be quite costly for a smaller gain. A cheaper squirrel cage blower will not have enough pressure. By the way, a lot of 2x6's have a 3' flue pan, some have a 42" flue pan.