preheater idea for batch pan boilers

[birdmancf]

Hey wondering if anyone has any feedback on my (insightful or insane) idea about a preheater. Been struggling with the external setup this year, not enough heat off the stove pipe...., baked syrup into a pipe wrapped around the upper part of my barrel when I didn't flush it....(see attached)
Anyway the idea was with the same 1/4"i.d. copper tubing I am using now, coiled in the sap in my back pan instead of externally on the stove?! Any thoughts? Would copper pipe in the boiling sap be worse than copper exposed to extreme heat on the outside of the unit? Would I be putting more copper ions into my finished product this way? Would it take the boil away from the rest of the pan?
I want to try it with water, but I don't have the wood to throw away right now, hoping for a few more weeks in the season here, but need to stop killing the boil.
Thanks, Chris

[KenWP]

Cold sap going thru the boiling sap would cool it down almost as bad as dumping cold sap in the pan. I have been useing the tubeing on the smoke stack idea but with it curved back and forth instead of around and have had some sucess. I am finding it does not heat the sap fast enough to keep up with my boiling sometimes. Have to re think the idea for next year somehow.

[DanE.]

I had the same problem, not enough heat transfer. I did find that adding some flashing around the copper helped. I was thinking of running a some 1/2 in copper through the stove pipe for next year. Hm, May I should make a sap jacket for the stove pipe, or one of those inline electric water heater, or ....

:confused:

Dane.

[Johnny Cuervo]

Take a look at my pre-heater. Its 3/8 tubing, and runs about 160-170F @ 12 gallons an hour with 750-850F stack temp. When you run out of sap just remove the springs and pull the unit off.

[Dill]

My tubing dumps the sap into a steam pan which is over my flue pan. The steam coming off the flue pan keeps it warm, then there is just a ball valve that trickles the warmed sap into the flu pan. It raises the sap temp about 30 degrees.

[Amber Gold]

Dill, you need to update you avatar to show your new setup.

[sapsick]

i wrap 1/2" copper tubing around the outside of my stack. i have a 6" stainless pipe for a stack. i have 7 wraps around the pipe and use a ball valve to throttle the flow. i get a 50 degree rise in temp this way. i plan on encasing it inside of another piece of pipr on the next boil to get it alittle hotter.

[lpakiz]

Sapsick--then wrap the outer stove pipe with fiberglass building insulation. And plug the bottom and top with fiberglass or arch blanket to trap the heat. Mine almost boils sap. However, I have to remove it when I run out of sap.

[WF MASON]

I had a customer who had a plumbing background and had played with plumbing his preheater box to copper pipe into the arch and back out. The preheater box is oversized and raised allowing the plumbing , the sap just circulates from the bottom of the box through the arch back up towards the top of the box, out another couplin to the pan. He says it keeps the sap at 140 degress comming into the pan. I'll try to post a photo. He says he doesn't understand why more people don't do this. I'm sure he has a better photo with his plumbing pictured he could post.
The photo didn't attach.

[birdmancf]

I had thought about going through the arch as well, which is very easy to do with a barrel set-up. I guess it comes down to making sure the pipes are always flushed clean with water when done. I've been trying to back/flush the pipe I sugared with vinegar and water to some success but haven't restored full flow yet.

I also played with adding boiling sap from the pan to the preheater bucket before it feeds the copper. I got temps up to about 140 from 45. Still looking for more heat though as half of the sap pan won't maintain a boil. If I slow the feed then I'm not replacing the sap fast enough.

And my girlfriend thinks I just sit there and watch the fire...

Thanks for all feedback,
Chris

[Mac_Muz]

Bill Mason, do you have a link to the picture?
.................................................. .................................................. ..


This year I made a crude take off on Johnny Cuervo's plan. That worked pretty well. I used graviety to feed from low off a 16 qt ss round pot zig zagging copper tubing up as tight as i could form old and already bent tubing to the stack. It spit out boiling sap at times, as the level in the pot got lower, but it never burned any inside the tubing.

I added a shield of use 10 inch cold return air duct which held in heat to the copper and to a part of the pot. Then it rained and i made a make shift hood of old roofing metal which I foumnd held more heat on the pan surface area and since it covered the 16 qt pot and the tubing more it worked even better.

Next year I hope to have the 16 qt pot on a stand next to the stove in a more or less enclosed sheet metal box. It may have a hot and cold closed tubing zig zaggin off the stack, and another zig zagging feed to the pan, but will probably be graviety feed instead of forcing heat to raise the sap in the tubing to the pan.

i also hope to build a shack and add another barrel to the one i have with another pan, so I can use the heat that just goes up the stack. This will either have to be able to move out of the way when sap has run out or have a a shut off so plain water can be added to the 2nd pan so the pan won't burn.

I will also build something of a hood, since it appeared to improve the over all boil.

My little rig can get a boil going over all in the pan being 21 x 34 and not just in the center like it looks your rig would do.

[Jim Powell]

I use a March pump (809) I got at a local brewers supply house that takes sap from my preheater which sits on my 2 x4 pan, and pumps it up through copper tubing underneath my pan and back into the pre-heater tank. It is risky, because you can't have it heat without good flow, but it when you let it recycle long enough it will boil the sap in the tube. But it easily gets the sap to 160° - 180°.

The pump is under a plastic box to keep sap out of the motor.

Message me if you want larger photos.

JCP

[KenWP]

I made a head tank out of a 5 gallon pail thats about 6 ft off the ground atthe bottom with a 3/8 tube attached. I used the back and forth bent 1/2 inch tubeing against the back of the stack and then 3/8 around the part of the stack coming out of the evaporator and then run it into a pail. This has ball valve on it now as with a boiler tap on it it would heat up and close off the dribble and then boil backward back into the head tank. I cut the ball valve back until it keeps the sap at the temp I want. I take this hot sap and put it in either my preheater at the back of the pan which is attached to the stack or the other preheater which sits to the side of the pan and runs sap through 3/8s tubeing around the top of the firebox and then into the pan. It has a tap on it which I can cut it back to a dribble and it runs really hot sap into the pan also.
This was the only way I could figure out how to maintain a constant boil by never haveing cool sap running into the pan. I have all I can get out of the thing now and its just a matter of the fact that the surface area of the pan is not big enough to boil any faster.