preheated AOF manifold build

[mol1jb]

Hey all,

As I was looking through some pictures today I found a good shot of my preheated AOF manifold outside the arch. I'm sure there will be plenty of AOF modifications to evaporators that don't have them in the off season so here is what I did. I hope this helps and would be willing to answer any questions.

Due to the complexity of the manifold and my entry level welding skills I built it outside of the arch and then slid it in the back of the arch and once it was positioned in place I tacked it to the arch in several locations. It consists of a back air inlet 3" wide then to a back piece of tube steel (2"x6"?) then into 4x 1.5" pipes that go under the raised flue pan and transfer the firebox heat to the air passing through and end up in a front piece of tube steel. Off the front tube steel comes 2x 1.5" tube steel arms that have 3/8" pipe as nozzles to distribute the air into the firebox. The front piece of tube steel also have 4 nozzles that put air into the back of the firebox. The pictures below I have sketched some lines that depict the air movement.

18628

In the second picture I have sketched on the arch where the pans sit in relation to the manifold. Half of the flue pan is exposed to the firebox.

18629

The front and back tube steel in the manifold are oddly sized but that was what I had lying around. As far as the effectiveness of this setup, I don't have much to compare against since last year we were boiling on an oil tank arch with steam table pans on natural draft. It was efficiently burning wood as I had no visible smoke out of the stack even right after a reload. And I burned less than a cord for my 34.5 gallons syrup.

[crzypete]

Thanks for posting! I am new to AOF, but thinking it may be a good fit for my evaporator. Do you use a blower to force air through this or does it naturally draw? Were you having issue before doing this with incomplete combustion?

Thanks

Peter

[Flat Lander Sugaring]

FYI leave air on in AOF until inside fire box temperature drops back down to 30C or so, this will prolong the life of the steel exposed to the high temperature and flame.

[maple flats]

Thanks for posting! I am new to AOF, but thinking it may be a good fit for my evaporator. Do you use a blower to force air through this or does it naturally draw? Were you having issue before doing this with incomplete combustion?

Thanks

Peter
AOF needs a high pressure lower, not even a squirrel cage blower will do it. There is lots of information on this forum about AOF, check it out.
One thing that will show you that you have incomplete combustion is to look at the top of the stack in the dark. That ball of fire is not flame that traveled the length of the arch and the stack, it is hot gasses that ran out of oxygen and re-ignited when it got oxygen. That is wood consumed that never added to the boil.

[mol1jb]

FYI leave air on in AOF until inside fire box temperature drops back down to 30C or so, this will prolong the life of the steel exposed to the high temperature and flame.

Ya good tip. I usually let the air run to cool the arch faster after I stop adding wood.

[mol1jb]

Thanks for posting! I am new to AOF, but thinking it may be a good fit for my evaporator. Do you use a blower to force air through this or does it naturally draw? Were you having issue before doing this with incomplete combustion?

Thanks

Peter

I used a bouncy house blower with good success. They work well and you can usually get one for under $100. This evap was built with AOF from the start but I can tell you that an evap with AOF will always have the most complete combustion in comparison to one without.