Series Loop preheater

[flackvillefarms]

I must apologize for starting another preheater thread but I can't find the answer. I have built a series loop preheater for under my hood. Its current configuration has 12 5' runs plus elbows then exits to the float box for the the flue pan. My questions are.

1. Should preheater only be over the flue pan? mine currently extends over the front pans.
2. How to add a vent and where in the system to add it? Does it matter on location if the tubing is level?
3. Does a bypass double as a vent if I notice vapor lock occuring.
4. Should I tear it apart and build a parallel style.
5. What materials are safe to use for a drip tray? Aluminum, copper, SS.

Thanks in advance.

[Eberzin]

Please post pictures for those of you who have built these. I am interested in putting one over my flue pan as well. Thanks

[flackvillefarms]

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current setup. Hoping someone can give me some tips on how to proceed. I know i need to raise the piping and add a drip tray so far. Need to figure out a vent and by pass.

[mol1jb]

I think parallel flow would be superior because it would reduce vapor lock. In your current setup the sap has to work back down a raised preheater setup plus if at any point in the run vapor lock occurs then there is no alternate path for the sap to flow vs a parallel flow preheater

[flackvillefarms]

Has anyone used an automatic air bleed valve from a heating system? Could this type of vent be used to vent steam in side preheater piping?

[flackvillefarms]

I have a feeling that I will be tearing it apart and re configuring it into a parallel setup. The more I read the more problems I keep coming up with. I wont be happy about it but I believe in the end it may be what needs to be done.

[maple flats]

Unless there is something missing in your picture, your design is flawed. For one thing, with all of the tubing in the steam but having no drain tray to catch the large amount of condensation, you may not see any net gain. With cold sap flowing thru the long tubing it will sweat big time. That will then drip back into the pan to be boiled again and again. Yes, the sap will warm but at a huge loss of potential because of the condensation going back into the pans.
Does your hood set down on the raised flue pan? If not is should, also, it should not be out in the open over the syrup pan, and the stack on the flue hood should have a damper. To use it for the best gain, when you are boiling hard, close the damper slowly, just until steam begins the leak out of any leak spots, the lock it in that position.
You will do far better if you design a parallel flow, even 2 tiers, all in the flue pan portion of the hood, with the hood setting down on the flue pan. Each section (whether 1-2 or even more) of the parallel design should rise from one end to the other. Then the entire system of tubes should join into 1, from there it could exit to the float box, or turn and rise again thru another like the first. With the rise the warming sap climbs the slope(mine is just 1.0" rise in a 54" long preheater, which then goes up to another level and then rises another inch to over the point where the first sap entered and from there it flows to the float box supply pipe).
Under the set of parallel tubes is a catch tray, which is also sloped and it drains of into the hood gutter and out, it also is under the steam stack, catching that condensate too.
If I have missed something I'm sorry if I misjudged it, I just called it as I saw it.

[maple flats]

I suggest you have vents, I used baseboard heat system SS coin vents. However I've never needed to vent. On mine the sap enters the hood just above the gutter in the hood, it then flows thru a header and from there climbs up 1" in 54" to another header. Then it climbs to another header and then climbs another inch in 54" as it goes back over the inlet and a 4th header. Each corner has a coin vent. My head tank is 16" above the preheater inlet, at the outlet the hot sap flows out of the hood and goes to a T (actually a 1" T designed for a coin vent in hot water heating) I have a thermostae in the 1/4 threaded port, and the sap flows past that and flows down to the float box inlet. That design has worked perfectly, except I wish maybe I had built it with more long tubes. Mine has 10 lengths of 1/2" copper, 54" long, plus the 4 headers and elbows. I raise my sap to between 160-170F but only until my auto draw opens, then by the end of the draw my sap is down to 120-130F. Had I made it 4 tiers rather than 2 I would have gotten hotter sap during a draw.
Good luck!

[flackvillefarms]

I really appreciate the replies. I'll be honest until about a day ago I didn't realize how flawed it was until i visited a friends sugar house and realized the condensate issues. This lead to the internet. Unfortunately this also lead me to learn about vapor-lock issues. It seems I fell into the weeds on something I didn't realize was so complicated. I'm glad I did as its a fairly simple fix. I will up date after modifications are made and with pictures. I hope my mistakes help the next person. Can some one post some pictures of what and how the vents are set up. what parts I should look to get at the store to make the vents. Much appreciated for the help guys.

[flackvillefarms]

where do you source those ss coin vents? Would you have part numbers?

[maple flats]

I bought mine at a full line plumbing store. It was called Oneida Plumbing supply. Any plumbing store will have them, but you might not find them at the big box stores.
Don't get too hard on yourself, you are sure not the first one to make such a mistake. Just be glad you didn't get it all up and running before you found out. Most of the materials you used can be re-used. I have to run now, but I will try to give you more ideas later today.

[maple flats]

Ok, I'm back, just had to drop my truck off for snow plow repairs, a solenoid valve is bad.
Here are a few pictures of the one I made http://mapletrader.com/community/showthread.php?27826-I-just-made-a-new-pre-heater
I already mentioned in earlier posts what I would change or at least consider changing.
Obviously those are all from before I installed it.
If my description of it as installed is confusing, ask as many questions as necessary, I will try to help.
This is by far not the only design that will work, but you need to keep the basics in mind that I stated in my original post giving the flaws to your design. A few of those again 1. a good height above the pre-heater for the bottom of the head tank. 2. air needs a way out and that can be done most easily if each set of parallel pipes has an upward slope towards the outlet to help any air move forward. 3. a pre-heater and also a steam stack will cause lots of condensation, that needs to be kept out of the pan or it needs to be boiled away again and again.
Some things, I hope you already know: you must use lead free solder and after soldering you need to clean the flux out and off the tubing. In that old thread I posted I mentioned that cooper is not what you should use, I have not yet found where I heard or read that. My pre-heater is still made of copper.
Good luck, and don't give up. When you get a properly designed pre-heater you will reap the rewards.

[Sugarmaker]

Flackville farms,
Well not the end of the world for sure. I make mistakes all the time because I don't do the research, or just talk to others. You have put a lot of time and effort in building your preheater system.
I may be able to help like others have suggested their ideas too.
But first I have some basic questions.
Looks like a brand new sugarhouse?
I see a releaser so you may be running a lot of taps?
Looks like the front pan is pretty new.
Hood looks to be home made?
Have you boiled with this rig in this sugarhouse?
Looks like maybe a 3 x 8 or 3 x 10 rig?
Keep in mind that a preheater of the best design may get you 10% improvement in sap boiling rate per hour.
With the raised hood system your room may be completely full of steam on a good day. Assuming you already know this?
What are your expectations from the addition of the preheater??
Enough of my questions!:)
Ok to your questions:


1. Should preheater only be over the flue pan? mine currently extends over the front pans. Yes normally they are over the flue pan and the stem hood would be setting on the rear pan
2. How to add a vent and where in the system to add it? Does it matter on location if the tubing is level? Adding a vent in a flat system is not going to be easy to know where it might vapor lock. Most parallel flow systems have vent/s at the upper high end
3. Does a bypass double as a vent if I notice vapor lock occurring. This might work but you only know you have a problem when sap stops flowing into the float box. Might work just something else to watch all the time)
4. Should I tear it apart and build a parallel style. You might try it the way it is, sometimes you find out things are not as bad as them seem and you may get some sap temp improvement. If you dont have it I recommend a gage on the output end to see if its working.
5. What materials are safe to use for a drip tray? Aluminum, copper, SS. I would recommend stainless. I have aluminum and I would much rather have nice clean stainless. Also you may not want a drip tray. They are very common but keep a lot of steam from getting to the preheater pipes. Might want to think about V shapes under each pipe.

Probably the most difficult part of building a copper preheater of the parallel flow type is the need for manifolds on each end. I think you could salvage the majority of your copper if you decide to try a different approach.
Hope this helped just a little. Keep boiling!
Regards,
Chris

[toquin]

I run a loop preheater under a hood that sits on the back flu pan. 1/2 copper 8 runs,5' long,no vent. Puts out 180 degree sap when we get rolling. Drip tray with alum. 1/2" angle under the runs drains to a drip channel on hood. Its gravity fed and we have to keep a eye on it when head tank gets low. Works like a charm.

[Sugarmaker]

Yep there is a good example of this type of a flat system working and providing good sap temps! All is not lost!:)
Regards,
Chris

[flackvillefarms]

To answer a few questions of yours. It is a 2x6 setup. I have boiled with it before. Partly why i am so cautious, I don't want to ruin a good thing. I wanted a preheater last year but never got around to installing it in time.


As of today I have torn it down. I have made a setup fairly similar to the smokey lake version so that I could reuse one end of the loops. I figure if it works for a company it can work for me. I shortened my 3/4" tubes to fit over the flue pan. They are approximately 45" long when measuring manifold to elbow. As of today I will have 6 loops from the bottom manifold to the upper. On one side of the upper I have a thread in "coin vent" to bleed air, the opposite will exit to the float box. on the bottom I have a entrance for sap supply the opposite end is plugged. Currently have it set on a car hoist to try and mock up locations of pipes coming in and out of hood. I have aquirred 1/16" 1" wide "v" aluminum channel to form the drip trays under the loops. This will extend over to the drip rail of the hood and have about a 1/4" of rise 46" from drip rail. as a precautionary measure I am going to be plumbing a preheater bypass to the float box for the just in case moment should it ever occur. I will be posting pictures once I have it finished. and cleaned up.

My plan is if the coin vent ends up being a waste of time I will plumb in a line that exits the hood to a ball valve that will dribble into the flue pan to alleviate air problems.

That is where I am currently at folks. I guess that is a blessing of this weather to give me a chance to get this sorted out.


Stats
We have 200 taps on vaccum.
Surge 11 pump powered by 3hp engine. auto shut off controlled by float switch in primary moisture trap
We have 26 taps on 3/16 line
Another 20 taps on buckets
2x6 evaporator with hood. soon to be added preheater. Wood fired.
12x24 sugar house.
Polaris 6x6 big boss with 125 gallon sap trailer
2500' pump line from sap tanks to sugarhouse. Saves on wear and tear of the property.

[maple flats]

That sounds like you have made a huge gain, good work.

[maple flats]

The V's are actually a good method. Did you also address condensate falling from the steam stack?

[flackvillefarms]

Nope to the steam stack issue. Haven't got that far yet. Any tips or pics out there would be appreciated while I have it all apart and off the rig. I am skilled at fabrication so if I can see I can usually build it.

I will add this, I am a first generation maple producer. I don't have family that does it and honestly before a couple years ago I didn't have any friends that did either. Everything I have learned has been on here, youtube, or from Gavin Mackellar over at Mack's Maple Supply in Potsdam, NY. I super appreciate the help that you all have given and or posted on this and other threads. The information has helped me a great deal. I hope to contribute as I learn a thing or two along the way. My kids are sure having fun watching and my dad gets a kick out of all the projects I come up with to refine our little operation.

[Sugarmaker]

Nice work! Recovery is everything! I redid mine a couple times as I improved it!
Regards,
Chris

[maple flats]

Just build a shallow funnel to be suspended under the stack and make it about 2" larger in diameter than the stack, then channel the condensation over to the gutter on the hood and then out to a bucket for use to help clean up.
I think you are now on the right track.

[flackvillefarms]

I'm tracking on that idea. I'll have to see if I have some sheet aluminum kicking around. I have some extra of the aluminum I'm using for the Vs. Once I build the funnel I could use a piece of that to channel the water to my hoods drip channel or the drip tray below the preheater. Ideas are percolating.

[maple flats]

I really like how you work. Some people get bull headed and want to 'prove" their idea rather than listen to those who have done it in the past. You will do well.

[maple flats]

While there is more than one correct way, it's good to look at many ideas, most of which will work and choose what is best for your situation.

[mellondome]

For vent on the preheater, i put a tee on the highest point with a 1" copper pipe going straight up 1' higher than the top of my head tank. I then set a 1 1/4 cap on top of it. This eliminates the need to check a valve periodically. The large size pipe will allow ample space for the air to pass out of the sap. ( too small of a pipe will give you a nice hot sap shower ) I also have just a drip pan under the preheater . This collects the preheater condensation and the stack condensation.

[flackvillefarms]

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Some photos of the progress. it is current sitting back on the evaporator. Supply lines are reconnected. Just my bypass is left to hook up. I'm actually thinking that I will hook a hose to it and leave on the wall. I have a T and a 2 valves coming from the tank. One is for the feed to the preheater, the other set I was going to have the hose long enough to reach the float box for an emergency bypass so that way I did have sap sitting in a line for no reason. my second though is put a second valve where it would tie into the float box so sap wouldn't reverse fill that line. Tomorrow I will cross that bridge with decisions to be made before I fill it up to check my levels in the pans and give it a test boil. Fingers crossed it all goes to plan. I can see adding a door in my future to the hood as well as a partition between front and rear pans within the hood. For those who may wonder yes it is lead free solder and flux, anything being used to fasten it either a copper bracket or stainless steel nut bolt and washer. Also drip trays are aluminum 1/16"x 1" channel with ss self tapping screws to fasten together for now. May have welded later in the year. After the test boil I will be buttoning up and sealing my hood where the old pipes originally exited and the new ones do now to help with its performance.

[Sugarmaker]

Looks pretty good! You did a bunch of work on it! Vent the high end and put a drain at the low end. You will want to drain it at some point. Drip V's look like they should work.
Regards,
Chris

[mainebackswoodssyrup]

That looks darn good. Not to hijack a thread but how far below then stack are you guys putting a drip pan? We don’t have a preheater but need to deal with the condensation from the stack. I imagine you want it below a ways so you can still get good draft up the stack.

[flackvillefarms]

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So I put a few more pictures up for those interested in looking. Tomorrow is a test boil day after I adjust my feed tank height. I realized it is currently level with the upper manifold of the preheater as I went to get water. Kinda of a bummer but I have some 10x10s I can use to space up my feed tank.

I think I have 3 more hood mods to come. I am going to fashion up a partial partition to separate flue pan from front pan. My thought is it would still allow steam to vent but keep the steam around the preheater more concentrated. The second mod is to fashion a damper for the steam flue. My third and final hood mod will be the condensation tray for the steam flue which will probably happen after the season is finished. Unless I get board......

[maple flats]

That looks a lot better. I hope you put a coin vent at the high point under the hood, even an icemaker self piercing valve just before the down turn as that pipe exits the hood if you find it air locks.

[flackvillefarms]

The coin valve I added is actually the highest point in the preheater system. Still tinkering with it to get it set right. I believe it is set about right now though. Boiled for about an hour or so at full steam didn't see any issues yet. It was pretty neat to hear the valve venting though when it was filling up.

[maple flats]

Good another success story. Good job!

[flackvillefarms]

Test boil was great. averaging in the 150's on the temp coming out of the preheater. Only boiled for about an hour. That was amazing compared to outside temp sap hitting direct into the float box of the flue pans like it did before. I have my levels up in my pans as well pretty conservative at 2" right now as I have much dryer wood this year and the preheater. Since I'm sure I can bump up those temps I will be adding a partition between my flue pan and syrup pan to partially separate the two within the hood but still allow steam to exit out through the hood from the front pan. I will also include drip rails on the partition to move any water to the main drip rail of the hood. I will also be adding a damper to the steam stack. I will probably do that during the first cleaning. I have two front pans so usually I swap them and on the third go I pull the flue pan and pressure wash it out as well, at that point I will have the hood off and will be able to drill and clean it up without contamination.


I also want to add a gasket to the rail of my flue pan where the hood sits. Not sure what to use or where to acquire from?

[Sugarmaker]

You did good! The damper will help the most to get your sap in the preheater to 180+ Don't worry too much about the gasket. The hood needs to have some air going in to get some draft anyway. Your damper doesn't need to be 100% closed, about 70 -80 % is usually about right. You will know when the steam strarts filling the room as it comes out of the cracks in the hood. Open the damper just a little and that's as good as you can do. Sap temp should jump up to 180 or maybe 200?

Regards,
Chris

[Eberzin]

Now I need to make at least a preheater. What kind and size of plastic tubing is it that you are using coming into your rig? I was using cpvc but may switch to something else.

[flackvillefarms]

I will give that a shot. I bought the aluminum to build one just haven't gotten to it yet. Had a snafu in the woods involving my vacuum system. Its all good now. The short version is plastic breaks due to vibration.

Eberzin the hose I'm using is a 3/4" food grade flexible hose I source from my local maple supply place ( Macks Maple supply in Potsdam, NY). I used the line instead of PVC or copper in case of a freeze. That way stuff has room to grow if I forget to drain something. I use it all around besides from the feed tank. Makes great transfer pump hose too. I do have an 8" long piece of 3/4"copper in the system coming from feed tank to give me a place to heat if I need to start thawing out stuff.

I don't remember if I mentioned it but my preheater is built with 3/4" copper and ended up having 6 loops.

[flackvillefarms]

For those following I built the steam stack damper, rain catcher for steam stack( may need revision), and divider plate that helps traps the steam to the flue pan while still venting the front pan. The divider has its own rain cutter "broke" into it that drains the water to the side troughs of the hood. I added a piece of 1"x1"x2' sheet angle between the flue pan and smoke stack to catch condensation and channel it to a bucket. I'll post some picture later if any would like, but it's off to my day job for now.

What does this all matter? At a full boil, while I was sweetening the pans. I had sap temps of +180 degrees coming from the preheater to the float box. Super happy with that. I also filled two and a half stock pots of water that came down the condensation drain tube. So I also had plenty of water to clean stuff up with. Which makes trips back to the house very minimal. Life is good. super happy with the results. I had 100 gallons of sap yesterday here so its starting to move.

[Sugarmaker]

Ok I applaud you for your work and documenting the results! Yes the hot water is a nice plus and you got the sap temp about as hot as possible. Nice!
Regards,
Chris

[mainebackswoodssyrup]

Revived an old thread rather than starting a new one. Is 1/2” pipe the standard for most preheaters? I am going to have one built and he is suggesting 1/2”. I was thinking 3/4” pipe in my head probably because that’s what I have seen before. His reasoning being that the 1/2” will heat better and quicker. I agree, just worried about the vapor lock. Go with the 1/2” and add a small valve to the pipe at the high point as suggested?