Perfect boil

[rayi]

Yesterday I almost had the perfect boil. Had a small continous draw for 4 hours but I had the AUF set at 1/2. Seemed to boil better less foam and was faster. I have an air tight door on a 2 by 6. Is it possible to get to much air into the fire

[mellondome]

Yes.. and it will cool the fire.

[pobryan]

Rayi,

I also have a 2x6 that I put AUF into this year and was wondering the same thing about too much air. We were averaging about 33gph with the blower wide open. Also we have a hood with a preheater. What was you gph if you don't mind my asking?
Pat

[Daveg]

I would think that the limiting factor in AUF would be the size of the chimney. As long as the fuel and temperature are consistent send in as much oxygen as you can as long as there's no blowback.

[Cedar Eater]

This reminds me of my former career. It can pay to recover waste heat from stack gases to preheat combustion air. It might take a cumbersome amount of hardware to do it and it can cause problems if you take too much of the heat out of the stack, but we made substantial efficiency gains in oil refineries by adding gas-to-gas heat exchangers to the stacks of furnaces and getting the combustion air temp up to 150 - 180 while dropping stack gas temps from 850 down to <500. You don't want to get the stack gas so cold that corrosive condensation occurs inside the stack. Something to think about. You might have to burn oil, propane, natgas or an awful lot of wood to justify the expense, but if you could draw or push cold combustion air down through the center of a wider stack and then to your AUF/AOF, that's that much less fuel you have to burn to warm that air. You would draw your combustion air from elsewhere until you got the stack gas up to temp. We used both forced draft and induced draft blowers with variable speed motors and PID controllers, but it doesn't have to be that complicated.

[rayi]

Was getting about 30 GPH This boil was closer to 34