275 gallon evaporator with pre heater box?

[Maplesugar]

I have an idea that I would like to try. Will this work? If not, why? I have the basic design like many have seen here in the past. The tank was cut in half, minus the back 12 inches or so, where the chimney is mounted. I have a 12 foot by 6 inch chimney. I have a blower that is mounted to the ash pan door. It really kicks up the boil and steam coming off of the pan. My pan is 30x48. The tank was 27.25 x 59 I believe. I flapped the angle iron to the outside to allow for a little larger pan. I have the stove bricked and put an angle cut on the bricks to allow the heat to reach the top edge of the angle iron rails. I felt the larger pan would off set the slight difference in the boil difference if a smaller pan would have been directly over the fire. Not sure if this was a bad idea or not. Seems to boil and steam from edge to edge. NOW FOR MY QUESTION: The back side of the chimney is very hot and I know there is a ton of heat going up the chimney. I would like to grab some of that heat and make a pre heater box on the back side of the chimney. The thought is to cut a 1.5 inch flap in the back side of the chimney area and redirect some of the heat as it goes up the chimney. I have a 24" x 26" inch pan from my old 55 gallon barrel evaporator. I would like to build an angle iron frame to support the pan. Then have some flat steel to cover the sides and bottom of this box. The box would be about 5 inches where it meets at the back of the chimney. The other side would be about 2 inches. The box would be 24 x 30 with a 3 inch chimney with a damper in it. The idea is to have a slight draw but not change the main draft to much. My thought is the small but dampened chimney would create a small draw to allow 600 to 900 degree beneath my old pan. I don't need it to boil. But, I would like it to steam. Please give me your thoughts.

[Bernie/MA]

I built an arch identical to yours except the top angles face inwards and the pan is 28. I tried a shelf against the tank/stack over the pan to pick up heat and it didn't amount to much. Whatever you do, make it so you can put it back original it it doesn't work. Does the 3" pipe tie into the main stack? Check my idea below about the spiral trough. I'll be trying a prototype next week I hope. There's a time crunch because we're leaving on vacation next Wed. Maybe the sap will burn before it gets to the bottom. It so it won't be the first good idea I've had that didn't work, lol. What state is Lugerville in?

[Maplesugar]

Bernie, I plan to make it so I can put it back together if it doesn't work as planned. I don't understand how it will fail, so I have to give it a try. I have it feeling it will not work. Seems like if the idea would work, I would have found pictures of it online. The idea is so simple that it is hard for me to believe someone else has not come up with the idea. I have a few ideas on how to change it. If it doesn't work as planned. It seems to me that the only way it could really fail is if the draft gets screwed up. The heat is wasted that far back in the stove anyway. Even if you heat it 20 degrees.
that is 20 degrees you didn't have before. However, I'm hoping I can get it to steam. I'll likely try it unless I hear from someone why it wouldn't work. But with the blower forcing air in, it seems like the hot gases are going to be forced up the chimney as it is the path of least resistance. Some of those hot gases will likely fill that box that is mounted on the back of the chimney. The top of the box will be the bottom of my old pan. I might have to play with the dampers for a little bit in the beginning to get air flow from both chimney's. But, I think I can figure some out that will increase my overall efficiency. If not, I'm only doing this for fun anyway. I produce less than 100 gallons anyway!

[TomorrowRiverMapler]

As you know there is a ton of wasted heat in that 12 inch portion of your arch. I have a similar set up where my first year was a 26x36 pan in the front and the back 24" was the original tank with an 8" pipe coming out the back versus the top. I had welded some sheet steel along the back sides of the tank and put a 24x24 angle frame on top and kept a 24x24 pre heat tank there. After realizing how much heat was going through that 24" back the next year I cut the top of the tank off and welded a framework like my syrup pan to put a 26x24 flue pan there. It boils just as good as my syrup pan. I even added a 24x48 secondary flue pan after that using an old semi saddle tank cutting the top open and welding a frame work. My boil rate went from about 10 gals/hr to 22 now. Next year I'm going to redesign the back again and swap the two flue pans as I still lose a lot of heat between the oil tank and saddle tank. Long story short but for the time spent building what you describe you may be better off to cut open the back 12" of your tank and put your 24x26 pan there and then just pipe out the back. You will definitely get way more evaporating with not much extra effort. Good luck on your decision.

[Bernie/MA]

Hey MS, if you are in WI I will be about 1.5 hours from you next week.

[barnbc76]

I agree with tomorrowrivermaple, it would make more sense just to extend your tank.