Needing input on my auf

[cpmaple]

Good morning,
Just looking for some idea's on what to do with the blower setup on my 3*10 raise flue G.H. Grimm
The front is the old cast doors so not air tight which I'm fine with just trying to cut down on ash an sparks coming out around doors. Older unit with a factory blower setup that is the width of the arch an just blow straight under the grates. Question is would I better to build a fake wall say 6-8" back from front of arch to deflect the air up? Right now it blows straight out. Not sure how I could build a disturbution header to mainfold due to the duck work into arch is 4"*3'.
Thanks for any input cpmaple (Chad)

[tcross]

i put a row of fire brick on top of my grates right in front of my door. i also have more than 2x stack height compared to my evaporator length which helps with a good draw up the chimney. i am able to open the door and feed the fire without killings the fan each time... i do turn it down to half though. the combination of blocking off the front of the grates and a good draw are key i believe.

[Bucket Head]

You can also "fine tune" the amount air going in by blocking off some of the intake area on the squirrel cage blower. This, too, will help get you to the point Tcross mentioned. Being able to fire it without getting a facefull of smoke and ash, and not losing facial hair is a good thing.

Steve

[maple flats]

I put high pressure air over and under the fire on my old 3x8 evaporator years ago. For the under fire air I had a 4" heavy galv. pipe going in from the back toward the front ending about 6" before the front of the arch. It had a cap on the front and blew the air out 3 rows of drilled holes, one top center and one facing each edge of the grates. The holes were about every 2-2.5" apart and were 5/16" holes. Mind you these were high pressure low volume, not low pressure high volume but I got no ash, sparks nor smoke out the doors, even when I opened the doors with the blower on. That blower ran from soon after initial light up until the final coals burned down after the boil.