More air?

[nvr2l8]

I resendly reduced the space between the bricks and the pan to about 1 inch. My stack temp went way down(900 to 500 ) which tells me the heat is now going in the pan.I get a better boil now. I am however noticing a gas type smell when am firing or near the back of the arch splitting wood. I actually thought someone spilled some gas but now I think it may be wood gas that isn't burning because not enough air? I am using an air mattress fan right now. Perhaps i need more air volume less velocity. How about secondary air in the flue section? thoughts?

[maple flats]

High Pressure air over fire. If in fact you have unburnt woodgas, by far the best fix is to add air over fire (AOF). It then burns that gas under the pans rather than send it out the stack. It will give you more heat from the same amount of wood. It is far better than adding more air under the fire, but since you likely have a smaller evaporator, changing the air mattress blower to something moving more air will help, just not as much as AOF Adding more air under the fire will help, but it will also burn more wood, not increase the efficiency near as much if at all.

[Ghs57]

Adding AOF was the best thing I did this season. Stack temp is low, under 500 according to the probe thermometer, and the fire box is hot. I ran a bigger rig, 2x6, with essentially the same about of wood as my 2x4 flat pan with no air. Overall I used more wood, but made twice as much syrup. Dave's right, it's the turbulence created by the high pressure fan that makes the difference. I got a used bounce house fan on eBay for under $50. It did take some work to fabricate the air manifold and build it into the arch, which means I got a late start this year.

[treehugger]

Adding AOF was the best thing I did this season. Stack temp is low, under 500 according to the probe thermometer, and the fire box is hot. I ran a bigger rig, 2x6, with essentially the same about of wood as my 2x4 flat pan with no air. Overall I used more wood, but made twice as much syrup. Dave's right, it's the turbulence created by the high pressure fan that makes the difference. I got a used bounce house fan on eBay for under $50. It did take some work to fabricate the air manifold and build it into the arch, which means I got a late start this year.

Do you have any pictures of you aof build?

[nvr2l8]

Thanks guys.I never really understood why some had auf and some had aof. You need lots of air in the right places! I love this hobby I feel like "Tim Tayler" we're aways trying to make things run better!

[Ghs57]

Do you have any pictures of you aof build?

Here are a few of the build. I followed the UVM document for the specs. You can search for it here or go to the UVM web sites. The AUF is not shown in the pictures, but was piped in under the grate via a "U" shaped manifold of black iron pipe. 1/4 inch holes were drilled in the top of the pipe every six inches, and the same fan supplied air to both.

1417114172

After running for a few hours, the ends of the nozzles would be glowing red. With the door open, you could see how the forced air was creating turbulence in the fire box. There was no smoke out the stack, or wood burning smell. I had a welder put the pieces together.

[treehugger]

Nice looking job

[Ghs57]

Nice looking job

Thanks. The manifold was covered with arch board, living only the nozzles exposed. The arch board took a beating from the wood during loading. Aside from the fact that the fire box is too small for my 2x6, I probably wouldn't change anything. Therein lies my dilemma. Make it bigger or leave it alone. I'm not getting the max gph on the pan because I don't have enough heat under the flues. Certainly something to consider when making modifications, such as adding air. The bottom of the flues at the back nearly touch the fire brick. But only the front of the flue section boils hard. Syrup section also boils very well.