i used to see lots of sparks and flame out the top of my stack, before I added air over fire (AOF), that stopped it. The sparks and flame out the top are in indication of incomplete combustion. Study combustion efficiency here: https://mapleresearch.org/pub/combeffic/
It will change that and will improve your boil rate, thus using less fuel.
When I added AOF I made some alterations to what is prescribed. I was using a 3x8 evaporator. I got a 100+ year-old high-pressure blower that came out of an old factory. It was 3 ph which I didn't have so I removed the 3 ph motor and put a 120v single phase. I experimented to find what my 1/2 hp motor could turn and I put the biggest drive pully it could run easily on it, the blower had a 3" pulley, the motor a 7" on a 1750 rpm motor. I did not test the CFM but it blew air with good pressure. I then welded up a manifold to circle the firebox, it sat on a row of fire bricks so the nozzles were 6" below the pan. I had a nozzle every 6" from one side of the fueling door all around to the opposite side of the double doors. The nozzles were pointed down at I believe 12 degrees (memory not perfect) towards the opposite side of the firebox. For my manifold I also skimped, I had lots of 2x2 square tube, so I made the manifold out of that, rather than the 3" pipe suggested in the literature. I likely got less than ideal but it was a huge improvement and all I had to buy was some 4" PVC pipe to channel the air from out under my elevated tank platform to in under my arch. There I actually split the air into 2 3" PVC pipes, one for air under fire AUF) and one for AOF. On each I had a 3" brass ball valve (also free from that closed factory I mentioned, picked from their trash). The AUF valve was open about 20% while the valve for the AOF was open about 65-70%. The AUF went in under the arch and blew air under the grates thru 3 rows of 5/16" holes, one top center and one each pointing towards the outer edges of the grates. The AOF entered the arch thru the ramp in a 2" tube, which then joined the manifold which surrounded the firebox. I had wondered if I'd have been smarter to widen the joint where the two met, but never did widen it.
The results were fantastic, no more sparks out the top, no flames out either and my fueling went from 1 arm full load every 7 minutes to about 80-85% of the wood, every 9 minutes. A significant savings of wood. At the same time my boil rate climbed about 12-15%. a win-win-win in my book.
If you get high pressure AOF you will see no sparks nor flames out the stack and will save lots of wood. The blower must be high pressure (spinning paddles, not a squirrel cage blower. A squirrel cage blower is high volume but rather low pressure. Thew high pressure is needed to create turbulence in the fire increasing the combustion efficiency.
Last edited by maple flats; 10-09-2022 at 10:06 AM.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.
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