Simple Preheater

[Sugar Sue]

I saw a picture of some copper pipe wrapped around a flue. does this work for a preheater? if I leave some space and not wrap it tight will it heat it up without boiling it in the pipes or busting the pipes? can't find the pictures any more. Some one had it running outdoors on a cinder block arch.

[3% Solution]

Sugar Sue,
Yup that would do it!!
Will it boil in the pipe ............. yup sure will if your not calling for sap fast enough.
Our other set would do 17.5 gallons an hour it we would get the sap boiling in the pipe.
So, have your self a valve that goes somewhere else besides the flue pan (like a buck) so you can ope to get some sap coming through if you have to.

Dave

[Bucket Head]

Sugar Sue,

Take a look at my Modifications album at the photobucket link. You can see how I had copper around my stack at one time.

I never had any boiling in the tube, and I'll tell you why that was. First, the sap never sat in it long enough. The evaporator was always "calling" for as much as the copper could supply. I should have gone with 3/4 copper, like the heater I'm using now.

The other drawback was the lack of heat transfer. Despite all that copper, there was very little contact between the copper and stack. Also, I should have sheilded and/or insulated it. Being outdoors, and in the wind, the outside of the coil was not receiving any heat.

I hope this info helps with what your planning. Good luck!

Steve

[maple flats]

Another picture to look at is johnny cuervo's set up. To find it go to members, search johnny cuervo and look in his albumn. His set up can be regulated to an extent. Looked real neat. If it works, hewre is the link:
http://flickr.com/photos/57535094@N00/sets/72157601539320490/

[Buckeye mapler]

this is some creative thinking.

[Haynes Forest Products]

Make sure that it will drain completly when your done. you can get sap to freeze and bulge the copper and then split.
If you decide to wrap a pipe with copper a few hints. Use soft copper the kind in a roll at Home Depot. Use a small Bursnomatic torch to help soften the copper even more you dont need to get it red hot just warm it. If possible wrap copper around something the same size as your flue pipe because wraping on the flue pipe it will distort. Get it as tight as possible for good heat transfer.
Now a quick lesson in heat transfer. Heating a pipe wraped around a pipe that is hot is called "radiant heat". Radiant heat will only heat the side that faces the heat source. Just like when you stand next to a camp fire your front overheats and your backside is still cold.
To get all the heat to the preheater the best thing to do is coil copper tight and if the flue pipe is 10" and the coils add about 2" more get from Home Depot a 12" Galvanized heat duct pipe and they come split down the middle. Just snap it over the copper coils and wire tight. The black flue pipe and the shiny duct pipe will work best. You may need to cut small slits for the in and out areas of the copper. What this will do is reflect the heat back to the coil and supper heat the sap.

As mentioned you might get boiling in the tube so use 1/2 tubing with good head pressure.

[Jeff E]

You have to love it when the creative juices start flowing! Mapling at its best!

[TapME]

sue; how many taps on that 2x6? It would help to make a style of pre heater that fits your # of taps. The greater the # of taps the better the pre heater should be. It would give us a chance to get more creative. Just a thought

[SeanD]

I've always liked the coiled preheater on the stack for its simplicity and efficiency of space and heat. The only down side I ran into was just too big for me to overcome - the shutdown. That stack stays very hot long after the last of the sap has run through for the day and unless you have a tank that can feed it for a couple hours and a tank to collect it, the copper is going to dry out and I would guess burn any residual sap in there.

So, I opted for putting a valve on a steam pan and letting it drip into the pan. It was still simple, but couldn't produce the hot sap that a stack system would have. There was a lot more peace of mind though.

I wouldn't mind hearing from more users of that system and ways they work around the issues. Johnny Cuervo's springs look promising. Is the number of coils part of the control?

Haynes, I like the outer pipe idea. Maybe the coils could be tight to the outer pipe so that at shutdown the outer pipe can be popped off. Do you think the inner space would still generate a good amount of heat for the sap?

Sean

[Haynes Forest Products]

It acts like a reflector oven by getting heat to the backside and containing the heat in a small space. That might be a good option is remove the heat consentrater. If the head tank is empty why not flush clear water down the tube maybe a diverter tube past the float box into a bucket or a valve NOT the float valve but one that shuts the flow off compleatly and throw in some clear water and let it sizzle and boil with just water it wont burn or overheat little vinagar and your clean and ready to go in the morning.

[SeanD]

That's a really good point. Running 5 gallons of water through it would do a pretty good job of flushing out most residual sugar I would think. It would also provide some nice hot water for clean-up. Talk about up sides!

[Smitty]

The bigger the tubing diameter the better. There is no way to stop boiling in the tubing, but if you can relieve the pressure the sap will have a more constant
flow towards the pan. At the top of your preheater were the incoming cold sap
enters the coil, put a tee thier, run a small plastic or copper line verticaly straight up. It must go higher than the top of your sap holding tank. This lets any of the pressure out automatically without manually maintaning the preheater. A little pionter, Make sure the mud wasps have not plugged that
line at the beginning of each season.

[Mac_Muz]

I agree, see Bucket Heads, and johnny cuervo's pictures.

I am going to do something like that and jam the tubbing into the stove hard up. But with a way to get it off and away as well.

Last year i wrapped the pipe, and while I was able to spin to wind the tubbing on and off the stack it sure was hard to do when the stack was hot.


I used gravity to feed the copper tubing, and adjusted the level so heating would expand the sap volume, and boiling but not burning would force the tubbing to spit boiling sap into the pan.

Maybe it would be a good idea to see my thread in this room here to sap seeker. There are pics from last year, which will be somewhat different this year using the same ideas as Bucket Heads, and johnny cuervo's pictures have shown me.

[Johnny Cuervo]

Yes you can release 1 or 2 springs to lower temp if flow rate is too slow. I've used this system for 4 years, it works great. The only thing I added was a piece of tin wrapped around the coils, this sandwiched the coils between the stack and the tin. Other thoughts I've had was to run copper through rollers to make it oval (more contact). Also I used 3/8 tubing, you could increase diameter, thus leaving sap in tube longer for faster flow rate. To shut down when out of sap, just pull all three springs and slide coils off stack.

John