Homemade Preheater

[danno]

Do preheaters run the sap back into the float box and if so, does the sap cool again in the float box?

I was thinking of running some copper over my pan and under my cover and run sap from my holding tank, through the copper and than into my float box - but does it cool? Is there a better way?

My preheater on my old DG consists of a 3"x28" box that sits in the end of my pan. Sap enters the box from my float box, warms in the preheater and then runs doown a 1" piece of copper to the fron of the pan.

How much will a copper preheater increase my GPH in my old 30x8 which is probably only doing 40-50 gph now? I'm adding forced air as well.

[Sugarmaker]

danno,
If you build a conventional preheater like Leader style You should gain 5-10 gallon per hour. I also get at least 5-7 gallons of just condensate, off the sweating tubes. As far as cool down I don't think it cools down in the float box. Generally about 200 coming out of the preheater and the float box is probably 205-210 degrees.

Sugarmaker

[powerdub]

I think I gained 10 gph as well. I must add that you will need to put a pan with a drain under the copper pipes to catch the water that condenses and drips off.

[danno]

Does the pan below the preheater interfere from the steam escaping from the sap pan below?

[powerdub]

No, unless you totally cover it but you only need to make it a little bigger than your copper that runs inside. You need to catch that condensation because if you look at sugarmakers numbers, you will gain 5-10 gph and run off 5-7 gph of condensate. If you don't catch that you will not gain anything. It also gives you a good supply of very hot water to wash with.

[danno]

What diameter copper do you use? I think I heard something about sap evaporating in smaller diameter copper? Will I need to put a damper in my steam stack to get preheater hot enough?

Anybody have any pix or able describe how to plumb an outlet drain off of a pan below a preheater?

[powerdub]

I use 1". I bought back before the price of copper went out of control. I think I have mor than 50' in it. I went back and forth five or six times, dropped down at the end and went back the other way the same. It is one continuous flow through. I would but a damper in the stack, you may not need it but that is the way they come from the factory. Mine is dampered but it is more of a box with covers than a hood. As far as a pan goes, made my own and welded a ninety in the bottom center and piped the drain right out the side. Four stainless steel threaded rods pretty much hold the whole sorry contraption together but it works. I will try to get some pics.

[WESTVIRGINIAMAPLER]

Danno,

I have several pics on my website of my hood and preheater. The way I designed my preheater drip pan is that the end of the drip pan lip is bent nearly 90 degrees down about 1" and the lip on each end sits right into the condensation channel on the hood. This kill 2 birds with one stone and I don't need a seperate drain for the drip pan. :) The drip channel on the hood completely supports the preheater and drip pan and I don't have to worry about any brackets for it either. :D

I get about 50 gph evap rate and I use 3/4" thin wall copper pipe and it is plenty of flow rate. 10 to 12% is a realistic gain expectation with a preheater.

[danno]

Thanks for the ideas and nice pix!

How does this sound - use a 25' or 50' spool of copper tube. Keep it right the way it comes. Plumb into it for incoming and the other end for out going sap. As it is already in a circle, for a pan, cut the bottom few inches of a round glavenized stock tank/tub. Drill a hole in the bottom of the tub and plumb an outlet for water to drain.

[WESTVIRGINIAMAPLER]

Just make sure you can drain it at the end of each boil or it will freeze and bust. :?

[Sugarmaker]

Danno Let us know how that works!

[Fred Henderson]

Thanks for the ideas and nice pix!

How does this sound - use a 25' or 50' spool of copper tube. Keep it right the way it comes. Plumb into it for incoming and the other end for out going sap. As it is already in a circle, for a pan, cut the bottom few inches of a round glavenized stock tank/tub. Drill a hole in the bottom of the tub and plumb an outlet for water to drain.


What dia tubing are you going to use?

[danno]

I'm gonna price the stuff out for the best price, but I'm thinking around 3/4 or 5/8 - unless others suggest differently. I was figuring a 25 ' spool would be enough as well. 50' would get pretty cramped under the hood.

[WESTVIRGINIAMAPLER]

I have about 23' of 3/4 thin wall copper pipe in my 2x8 preheater and I get temps of around 175 degrees.

[Fred Henderson]

I have about 23' of 3/4 thin wall copper pipe in my 2x8 preheater and I get temps of around 175 degrees.


I got 20 ft of 3/4" fin tube and 4' of 1 1/4" feet pipe so I will be curious to see what kind of temp I can get with it. My old one had 36' of 1/2" and I got temps of 180 out of it.

[Russell Lampron]

I don't think you should go any smaller than 3/4" pipe. You don't want to be in a situation where you can't get enough sap into your flue pan to keep up with the evaporation rate.

Russ

[Fred Henderson]

The only problem that you might have with a single line is that if it vapor locks there is no flow then. A single line would really give me a bad case of heartburn.

[powerdub]

You will need to put in bleed valve to keep the flow running. I used a piercing valve for putting a residetial ice maker. Also, if it is vapor locking that much you can open your damper and cool it down a touch.

[danno]

Man, copper did get expensive. If I use coil copper, can I use refridgertation tubing?

It's thinner walled than "K". I'm sure PSI is not a concern for a pre heater. I guess the only issue would be it splitting if it was full and froze. That's what the air compressor is for.

[danno]

Also, can you run PVC under your evap. hood. Any problem with the heat/steam reacting with the PVC?

I found a round 27" hot water heater tray that will make a great pan for under the copper coil and the pan already has a pvc fitting for draining. My idea would be to just run the PVC through my hood and drop it down into a 5 gall. bucket.

Also found 50' coils of 3/4 inch refidgeration copper coil (.035 wall) for under $50 - would like to use that if that it will hold up as a pre heater. Standard "K" copper coil (.065 wall) 60' rolls are like $200! Any copper guys following this thread?

[Fred Henderson]

The only difference in ref copper and that used for water is 3/4 ref copper is 3/4 ouside dia. Where as water line that is 3/4 is 7/8 outside dia. It will be almost impossible to use water line fittings on it, unless you braze a water line fitting on it to make the transition.

[brookledge]

Danno
The reason copper is used is that you need a good heat conductor. PVC will not transfer the heat like copper will.
Keith

[WESTVIRGINIAMAPLER]

You would heat the sap very little with the PVC and I don't know how long or how many years if any it would stand up to the constant heat. You should be able to make a preheater similar to mine for under $ 200. My manifolds and everything on it is 3/4" thin wall copper pipe. It is very simple to make, not expensive and works very wall. I also have a brass valve on the low end manifold to drain it every night and I don't have to worry about freezing. :D The 90 degree corners on mine are streeted to allow you to compact it more.

[HanginAround]

Sounds like he is talking about pvc just for the drip tray plumbing. I think it would be okay, but not sure.

[danno]

"Sounds like he is talking about pvc just for the drip tray plumbing. I think it would be okay, but not sure."

That is correct, I was not going to use the PVC to heat the sap. For that I was going to use the copper coil. The PVC is just to drian the condensate out of the pan below the copper.

[ibby458]

I have a vague recollection that PVC gets all soft and mushy not far above 180 degrees. I'd try a piece in a pot of boiling water before installing it in an evaporator. That'll tell you for sure if it'll hold up.

[Fred Henderson]

"Sounds like he is talking about pvc just for the drip tray plumbing. I think it would be okay, but not sure."

That is correct, I was not going to use the PVC to heat the sap. For that I was going to use the copper coil. The PVC is just to drian the condensate out of the pan below the copper.


Cut 4 or 5 feet off that coil and use it, it won't make that much difference. :D

[WESTVIRGINIAMAPLER]

You can buy 5' sticks of copper @ Lowes that are not very expensive. 1/2" would be big enough for the drain. :) I would stay away from the pvc if possible. :)

[Sugarbear]

You may want to consider using CPVC pipe which is made for hot water.I think that regular PVC will get soft when exposed to that much heat.

[danno]

For any of you guys that insulated your arch doors, what guage steel or boiler plate did you wind up using.

Just buttoning up the preheater and I picked up the thermal blacket for the doors, but I want to sandwich it in with steel or plate like others suggested.

[Fred Henderson]

I use 3/16" SS with SS bolts. I got it at a scrap yard for 23 cents a pound, so the total was around 23 bucks. I used a 1"x 1/4" black iron pipe for a spacers so not to compress my ceramic blanket.

[JasonS]

I'm curious about inslulating the arch doors. I must have missed the pervious topics about it. Are you just doing it because the doors are old or does it really help your evap. rate. I have new style leader arch with a blower and every year I have to glue stove gasket around the door opening to keep the smoke and ash inside. However the gasket dosen't really hold up to the high heat and by the end of the season it's rock hard and falling off. Any ideas? I really don't want to drill holes into the door for screws. I'd like to make some type of latch system to hold the door closed completly.
Thanks,
Jason

[partsrus1974]

Not to beat a dead horse ,can anyone tell me why the drip pan under the preheater it self,don't make condensation?The Steam has to condense on it.I realize the pipes will sweat alot cause there colder but how much goes back in the evaparator from the drip tray? I am building a pre heater like wvm's I used 40' of 3/4 soild copper.

[twobears1224]

stick with all copper..pvc can,t take the heat at all.

[Haynes Forest Products]

The tray is thin sheet and gets hot from the steam and sence the pan is heated by the steam it cant also be cooler than the steam SO no condensing because of heat differential. The water that drips of the pipes is warmer than the sap but cooler than the steam but when it hits the pan it heats up quick.

[partsrus1974]

thanks haynes!!!I made a tray tonight.The preheater is almost done.I need 1 more piece of 3/4,I will get it done tomorrow.My pre heater last year only had about 6' or 1" so it will be interesting to see the diffenence.

[tessiersfarm]

I just mounted mine under the hood tonight. It has 3/4" in and out with 3 -1/2" parrallel lines. Total of 48' of 1/2" and 5' of 3/4" on a 2x6. Drip Pan is as explained earlier and sits on the drip channels of the hood.

[xulgiy]

Has any one set up a manifold type preheater with the pan over the sap pan without a hood??....it must help a least a bit. I don't have funds for the hood...put I have the copper ad drip pan ready to go.

Thanks!

[3% Solution]

John,
Go for it, like you said, better than nothing!!!
What do you have to lose!
Anything is better than 38* sap!!
I've still got you on the list of folks to call!!!

Dave

[Haynes Forest Products]

I had a preheater on my old 2x8 and I made it out of baseboard tubing with the aluminum fins on it. It got the sap up to about 90 degrees. There was some dripping back into the pans but I think i was ahead of the game. On the old pans I just set it on the side rails.

Now for my thoughts about heat transfer COLD is the absence of heat.
Heat gravitates to cold. When you stand next to a indoor ice skating rink your face feels cold because its the heat leaving your skin and GRAVITATING to the cold ice. I think if you can overwhelm a preheater with hot steam you will get less condensate because instead of the cold sap cooling the steam causing condensation. If you heat the copper to the point that the out side of the preheater stays warmer then you are getting more heat into the sap and less condensing on the outside of the preheater. I felt with the fins on my copper coils and the thin wall tubing that they are made of it heated the sap quicker and caused less condensate.

[xulgiy]

Haynes... I like the sound of the base board. How many runs were there on the manifold?

3%.... we have 113 taps done with a few more to go. The new drop flues made a "little" difference..:) to the point were I think I'll need splash boards. The sap (water) is really jumping.