More coil around the stack

[dtorrey13]

Hey everyone,
I am a newbie and I am going to play around with the coil around the stack. I was thinking I am going to go with 5/8" copper but it seems a lot of people go with 3/8. I have a float valve so that is the main reason I am going to go with the 5/8" to help avoid vapor lock. I plan on putting a vent out the top as well. Will it even work with the float valve or is that a bad idea? My other question is if it would work to have the cold sap enter the bottom of the coil and out the top. My thoughts is that would increase my chances for vapor lock but maybe not since it would be vented and have the flow going that way. Just bouncing some ideas around, I know a lot of people have done variations of this and wondering if my plan would work. Thanks.

[acerrubrum]

I've read about many people using the coil wrap, but never with a float valve. If you have the wrap, the sap needs to move regularly through it to avoid steam troubles. I'd keep checking into this, it sounds like trouble to me, but I'm no expert.

[wnybassman]

I keep toying with the idea of coils around my stack, but I can't come up with a good plan of what I do when I run out of sap. I don't believe running the coil dry can be a good idea?

[acerrubrum]

I read one idea that might work for when you run out of sap to run through the coil. You just start running water through the tube and divert it away from you pans, I think it could be handy for cleaning up.

[325abn]

Give it try and see if it works, just keep an eye on it. Trial and error my friend.

The copper will be ok! What the melting point of copper, 1200?

[lpakiz]

Just have a pail of clean water handy. When the last of the sap enters the coil, dump in the water. Let it run a few more minutes til all the sap is in the pan, then slip on a short piece of diverter hose over the side of the pan and refill the bucket with it. If you need more water, jut reuse the hot water. Keep doing that until you are finished for the day and the fires about out. You could let the last pailful run out after you leave in case there is still some wood or heat left that might scorch the tube.

[deckers007]

I am using the Coil system as well but find if my flow rate gets to high, system stops working, i was thinking of putting a smaller section of coil directly in the stack. I would put 2 holes in the stack for an input and output. I figure this would give heat to the full circumference of the copper pipe, opposed to only where the pipe is in contact to the stove pipe on my current setup.

[optionguru]

I got 1/2" wrapped 10 times around the stack and then put the next size up stove pipe around the whole thing to insulate and hold the heat in the "pre-heater jacket". I used a brass valve to adjust the flow and I haven't had an issue in testing. I'm going to run water through it at the end and divert the pipe so the water goes into a bucket or the back pan which will help me clean it out.

[Paperman]

I am using the Coil system as well but find if my flow rate gets to high, system stops working, i was thinking of putting a smaller section of coil directly in the stack. I would put 2 holes in the stack for an input and output. I figure this would give heat to the full circumference of the copper pipe, opposed to only where the pipe is in contact to the stove pipe on my current setup.

I can tell you that a foot of 3/8 ss tubing running through the rear of the arch works if you keep it running. Slow it to much and it boils and your hosed, vapor lock even with a few feet of head.

[Big_Eddy]

Without a float valve and a steady flow of sap, you can wrap pretty tight to your pipe, and as long as you keep enough sap flowing through the pipe, it won't boil and burn in the tube. Flow water when done (Hooking top and bottom of the coil to the same tank of water will create a convective flow of water through the coil and eventually heat the whole tank of water) Never leave the coil dry while hot or you will get nasty burnt sugar in it. Drain when cool to avoid freezing.

I would not recommend any pre-heater method that could get over boiling temperature for a system with a float valve. A typical steam-heated pre-heater can get up to boiling temperature and needs to be vented for safety, but is not likely to boil sap in the tubes. A firebox or stove-pipe heated system can reach MUCH higher temperatures and become dangerous when sap starts to boil in the system.

With a float valve closed - sap will stop in the tube, it will then boil in the tube, and then your system will vapour lock if not vented (and could explode!!) or steam will come out your vent. Regardless, you will boil in the tube which will cause it to go dry and burn the sugar in the tube.

An option is to wrap the coil loosely around your stove pipe with an inch or so gap all around. You'll give up something in heat transfer, but gain a lot in safety. Add a feedback line with a valve at the outlet back to your tank so that you can open the valve and recirculate sap (or bypass the preheater to flood the pans if needed) Again - when out of sap - it is critical that you flood the tube with water and allow it to flow by convection back to a tank. If you see steam out of the vent - open the bypass valve immediately.