pre-heater

[nmerritt]

Is it worth putting together and using a pre-heater if I don’t have a hood?
Leader 2x6 new this year

[WESTVIRGINIAMAPLER]

Without a hood and a way to trap steam, a preheater would be useless to you.

[sweetwoodmaple]

There were some posts about using the stack to preheat. You can use the search engine to take a look back.

[Parker]

Make sure you put the coil on the outside of the stack,,have a vent line and dont run it dry!! good luck

[cheesegenie]

That vent line must be what I am missing. Half inch copper wrapped
around a few times, at least takes the chill off. But sometimes is stops
and then comes spurting out, with steam and a burnt smell.How would
a guy put in a vent , and where?

[WESTVIRGINIAMAPLER]

You can put a vent on anywhere, just make sure the top of the vent is well above the highest level in the feed tank or burping back into the head tank. One of the 1/4 copper valves that self tap and will mount onto different size pipe should be sufficient. :)

[Carl S.]

This summer visited with sugar maker that had a 4' x 16' evaporator. He gave me some tips on making a pre-heater out of copper tubing. The flow of the copper was the same direction as the flue pans and used 1 inch copper tubing, enough to feed the float box; you could use 3/4 or 1/2 to get by. The highest end (4")was on the back of the pan and was just supported by some wooded blocks and the front flowed towards the float box. The copper tubing was supported by stainless steel V,s to catch the condensation off the tubes. This flowed into a bucket on the side of the evapotator for a fress supply of hot water. At the highest end of the tubing, he made a blow off valve to release any excess pressure. He stated that into the float box he temps as high as 185 degrees. He thought it was just as efficent, a portion of the cost, and easily built. I hope to add this to my new rig next season and save the cost of a pre-heater and hoods. Hope this helps.

[White Barn Farm]

Brandon
Where is the vent tube on your preheater? I can't see it in your pictures. I am planning to start building mine tomorrow evening. I am using yours as a pattern along with Ohio State's recommendations as well. I have a clear sight tube in my feed line directly after my equalizing tank that runs higher than my sap level will be. Will that work as a vent or should I incorporate one into the preheater itself?
Thank you.
Ed

[WESTVIRGINIAMAPLER]

Ed,

I don't have one on my preheater and in my opinion, there is not a need for one. Just run your evaporator at least 1" and you shouldn't have a problem. If you would get vapor lock, the evap level will drop maybe a 1/4" and the vapor lock will take care of itself.

Go for it, you can do it! :D

[Maple Hill Sugarhouse]

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[WESTVIRGINIAMAPLER]

Kevin,

I don't follow you there???? 8O To me it seems the head pressure needs to push the sap up hill some?? My preheater is about 52" and has about 3"+ rise. :?

[Maple Hill Sugarhouse]

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[WESTVIRGINIAMAPLER]

Kevin,

The reason I would think you would need head pressure with a parallel flow is that the sap would just flow up the center or the easiest path in the preheater if the preheater didn't have some uphill slope and the sap on the side pipes would be boiling?? With a continuous flow preheater, it wouldn't matter. :?

[maple flats]

I have never had an air block and mine flows downhill from the supply tank to the evap, then it flows up hill to the float valve. In fact mine is a double layer with a set of passes manifolded double deckered. I tilt the whole thing slightly so that the hottest sap rises to the preheater outlet and feeds the float valve. In other words as I look from the back of the evap the preheater inlet is low right and the outlet is about 4" higher and on the left. However I only have a partial drip catch trougth and much drips back into the flues pan, I need to address this to get the condensate out for greater efficiency. With my setup I get between 175 and 180 sap going into the float valve except just after a syrup draw, then I lose a few degrees but it comes back up in a couple of minutes or so. My preheater is set up with a inlet on the rear right end of the flue pan (looking from the back of the evap.)and it tilts up and to the left. Just in from the inlet there is a manifold that joins 5 or 6 tubes on the same plane and a tee that points up to a second layer offset 1/2 way between the lower tubes. The raised end (top left) of the lower tees up also to the upper level. I thought in this way I would get natural convection to the top left of the unit which then supplies the float valve. I however never had a hood on it, which I hope to also correct this year and then might be able to get another10 or 15 degrees hopefully. It is made out of 3/4" copper and I only catch a small portion of the dripping which gave me some hot water but not much. With the hood I should do a lot better. I have a good piece of aluminum 48" x 96" to work with and I just drew a preliminary design for the hood yesterday. I need to think it out so the first attempt is right because i only have one sheet of the aluminum to work with. I am trying to plan out how to bend it to have a good inner trougth for catching condensate and routing it out to catch in a bucket for hot water. I have a 10 1/2' trim brake to make it on and am good friends with a sheet metal fabricator to form the pittsburg on to join the ends ( a pittsburg is what holds the seams together on a typical section of rectangular hot air duct) I will still need to make a tray for under the preheater to channel condensate into the inner trougth of the hood but with the hood in place it should be a simpler design for a tray than without it because it may be able to be nearly solid instead of needing lots of steam passage to get the tubing hot for heating the sap. ( I think a picture would be worth 2000 words but I have none yet)

[Maple Hill Sugarhouse]

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[brookledge]

If you have a parralell style pre-heater and the outlet is lower than the inlet it will not work as efficiently as if it was installed as designed (outlet needs to be higher) Hot sap rises. It is the same theory as a hot water heater tank. cold water comes into the bottom and hot out on the top. Try changing your hot water tank and see how efficient it is.
If you have a series style pre-heater then it would not matter
Keith

[Maple Hill Sugarhouse]

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