Air under the fire

[nhdog]

I've done some searches and haven't come up with what I'm looking for.
I have a 18x60 Lapierre Vision, with a raised flue pan. i know an over the air is the most effective but i don't want to change the fire chamber at this time.
The air would come in through the back of the ash pit.

Should the air be distributed through a manifold, and if so ,what should it look like? or should it just be dumped in ?

[Hillcrest Maples]

I have the same evaporator. I started with a small 6” desk fan. Then upgraded to a harbor freight ventilation fan with a foot switch. Works awesome. Just open the draft door, push the fan up to it and hit the foot switch when it’s time to load wood. Zero ash and super hot fires. https://www.harborfreight.com/3-speed-portable-blower-61729.html https://www.harborfreight.com/power-maintained-foot-switch-57200.html

[maple flats]

I ran AUF on my last evaporator by entering from the rear down low. I plumbed it into a 4" heavy gauge round duct. It reached in all but 4" from the front, and there I capped it. I had 3 rows of holes, one top center and one on each side facing the outer grates. Each row was 5/16" about every 2.5-3", but mine was on a high pressure blower. If you are going to use a squirrel cage blower, the same idea will work, but I think you will want the holes larger. Try 3/8" and see how it does, if more air is needed drill the holes 1/8" larger and see if more is needed. Repeat until you find the right size.
While I had a high pressure blower, most will use a squirrel cage blower.

[BAP]

I've done some searches and haven't come up with what I'm looking for.
I have a 18x60 Lapierre Vision, with a raised flue pan. i know an over the air is the most effective but i don't want to change the fire chamber at this time.
The air would come in through the back of the ash pit.

Should the air be distributed through a manifold, and if so ,what should it look like? or should it just be dumped in ?
The first blower you need is Air Under Fire. Air over fire needs air under fire too. You will see a pretty big improvement adding a blower to your ash pit either through the ash door like Hillcrest suggested or cutting a hole in the back side of the ash pit and putting it there. Dave’s comments are good but don’t really apply to you because a 3’x8’ evaporator has much more room to add stuff to than a 18”x60” evaporator does.

[berkshires]

Should the air be distributed through a manifold, and if so ,what should it look like? or should it just be dumped in ?

I have a Mason 2x3XL. I don't know about "should", but I just cut a hole in the back of the ash box, bolted the fan to that, and that's that. I also stopped down the fan and found that for mine, about 1/3 open seems to work well. As I say, I don't know if what I did is "correct", but my boil rate did go from 7.5 GPH before blower to 11.5 GPH after. I also use a lot more wood.

GO