Flue pan vs syrup pan on small evaporator

[RyanB]

Hi Everyone- I had all intentions of stepping up to 600+taps this year and building a 3x8 or 3x10 evaporator but time got away from me in the shop (self employed cabinet maker) and I know there is no possible way to jump up 500taps this year. For the past few years I have been running a self built 2x4 flat pan arch and gradually increasing preformance and evaporation. Last season I tore out most of the fire brick and added an AOF manifold and also ran AUF with a 1800cfm dust collector blower and I added a hood/pre heater which both were amazing and could get 22gph out of it with minimum wood used. Seeing I have no time this year anymore to start a whole new build and increase taps from my now 100....I am thinking maybe it would be just benificial to make a new pan and up the GPH yet again. What I am thinking about is doing a combination drop/raised flue pan which will give me aprox 10" deep flues which will no doubt up my evaporation from my current flat pan. What else I am thinking about is either making a solid combination flue/syrup pan or two seperate pans but I am stuck as to the size of the syrup pan. Currently my 2x4 combination pan has a 32" rear and 16" syrup pan. Just curious as to what all your thoughts are on making the flue pan 36" and the syrup pan 12"? is that going to be enough room for the syrup pan or should I just stick with the 32"/16"? The reason I am thinking of doing this is that because of the raised/drop flue pan I am going to lose 2" of flue length compared to the pan length but doing so will increase flue depth/height giving the pan even more surface area.

So far I have the pan fully designed on Auto-Cad...just need to know if I should increase that syrup pan a little.

Thanks in advance...Ryan

[maple flats]

While some opt for a single combination pan, there are advantages to separate pans. I think your current ratio is good for that size arch, 16&32, with a flues pan you might actually do better with a 18 &30. I have run both drop and raised flue, it's almost a Ford VS. Chevy vs. Dodge type question. I prefer raised flue but that requires 2 float boxes. For that reason you might want a drop flue set up. You do want a valve between the pans so you can isolate the front pan for cleaning and at the final boil of the season you can boil water in the flue pan (after draining the sweet) and slowly add to the front pan to finish off. If you do go raised flue I highly recommend the 10" flues you suggest, that is what I have.
My current 3x8 started as a 2' syrup and 6' flues. I found the ratio not ideal. Then I bought new pans, 3' syrup and 5' raised flue with 10" flues. Runs real nice.

[dschultz]

maple flats
Ryan want's to build a drop raised flue not one or the other

[RyanB]

maple flats
Ryan want's to build a drop raised flue not one or the other

ya this pan will have a combination of both dropped and raised flue. In my drawings and in reality I can actually go with up to a 15"x1" V-pointed style flue. These flues will be a 2piece welded together flue with an overlap seam at the top and the bottom of the V and will be constructed out of 22g material (the overlap will be aprox 5/8" on one side of the bottom of the "V" on both ends of the flue). I will probably stick with something closer to the 10" mark though but am open to suggestions. Just trying to max out the boil on this thing and going with another valve/ float assembly doesn't bother me one bit between the flue and syrup pans as I wished I would have had it before.

Thanks...Ryan

[lpakiz]

Maple Flats,
What is your thinking when you recommend less flue pan/more flat pan than his first arrangement? Your post mentioned that you had 6/2 then went to 5/3. And you said you preferred the 5/3 ratio. Just wondering why? Thanks...

[Big_Eddy]

My few cents worth.

I like a 1:4 w:l arch ratio (2x8) as opposed to your current 2x4. I would strongly recommend you lengthen the arch along with building any new pan. You are missing out on so much of the potential heat by having a short arch. 2x6 minimum, 2x8 even better. You will not burn any more wood, but you will extract so much more energy out of the gases you could double evaporation even without adding flues.

That said - with any drop flue pan - you want the flat (syrup) pan to be equal to the depth (door to rise) of your firebox or as close as possible. Flues hanging down into the firebox risk of getting damaged by wood tossed in. I don't know what your current firebox depth is, but I would match that with the syrup pan. Not an issue with a raised flue - with your combo design would depend on the drop portion.

I don't know if there are any fixed rules - but most evaporators seem to run about 1/3 syrup pan, 2/3 flue pan. Bigger flues, less flue pan needed. The goal is to do the bulk of the evaporating in the flue pan without concentrating enough to get close to syrup.

[Robert K]

Just pondering this same idea, my arch is 2x12 and I currently have a 2x7 pan set-up from smokey lake. It works great and boils 35 per hour when I am on the ball and firing appropriately. As with most I am adding taps and would like to use the whole arch to boil. So do I go with 8foot flue and 4 foot syrup or maybe a better combination is out there? My current set up is 3 foot flue with 4.5 inch flue depth (drop) and 4 foot continuos flow syrup pan. i am also thinking about a drop/raised flue pan, I could get 9inch flue depth.
Any thoughts
Thanks Robert

[lpakiz]

I have a 2X10, and 8 feet of that is drop flue pan. 2 feet of front pan seems small, but it works just fine.

[MISugarDaddy]

Take a look at the sizes of new pans for an arch your size from the commercial evaporator manufacturers and then build the pans the same size. They (Leader, D&G, etc.) have done the research, so why not use their work to decide the appropriate pan sizes.
Gary

[n8hutch]

I would get a 7' flue pan made, & use your 4' continuous flow pan for a syrup pan, that way you can set your syrup pan back 6" from the front of your arch & you will get a real nice boil easily in your whole syrup pan, you will find if you look at the new high efficiency archs that the pans are set back from the front.

I also think you will have to put A fair amount of forced draft to A 2x12 arch to get the whole thing to boil well.

[morningstarfarm]

Before we went big a few years ago we ran a 2x6 and learned that there were 2 types made...the 4'flu pan was made for boiling raw sap and the 3' flu pan was made for boiling concentrate where you will really appreciate the extra syrup pan stability...we went with the 3' setup and never regretted it...my buddy down the street had the 4' setup and with his ro has to constantly fight with his 2' syrup pan back flowing every time he fires...that rig will handle 1000 taps comfortably with an ro...

[jrgagne99]

I would make a 5-foot drop flue (deepest flues possible, 9" by the sounds of it) and add that to your existing two pans. It is a cheap option that maximizes your arch. Also, all three pans could be handled by just two guys, which is nice. I think I would put the new pan in the middle since it would have deeper flues than your existing flue pan and would be more able to extract good heat than if you stuck it way at the back. I remember reading an article one time about an old Vermonter with an exceedingly long pan and he claimed it worked great. Not sure if he had AOF/AUF.

[maple flats]

Maple Flats,
What is your thinking when you recommend less flue pan/more flat pan than his first arrangement? Your post mentioned that you had 6/2 then went to 5/3. And you said you preferred the 5/3 ratio. Just wondering why? Thanks...
Sorry, I didn't see this question. On my first 3x8 I had a 6' flues pan and a 2' syrup pan. While it worked OK I often was getting a gradient issue, especially after changing flow direction. When I ordered my new pans, I went to 3' syrup and 5' flues, but since the flues are 10" rather than my original 7" flues, I still got more evaporation in the flues pan because of the height of the flues, but i found it smoother to run with the 3' syrup pan as opposed to the 2'. One thing that may be affecting that is the fact that I run a continuous draw, and I adjust by tweaking the draw off valve open or closed slightly. In fact, I have run continuous draw since back when I had a 2x6 on sap, rather than concentrate on a 3x8 (the draw speed is radically faster and on the 2x6 was hard to keep a draw for more than 20-30 minutes. With what I have now, I've helt a continuous draw for over 2 hrs, but usually about 45 minutes to 1.5 hrs before I need to close the valve.
If someone was not drawing the same way I do, the ratio might want to be different, I don't know.
As for the combination, raised/drop flue, I see no way for it to work without 2 float boxes, or the raised flues would stick up above the sap level, or the syrup pan would be 6+/- inches deep, or more
I have no issue with gradients in the syrup pan when I reverse flow, but I draw a full 2 qt pitcher just before the switch, close the valve feeding the old flow direction and I slowly dump it into the new draw off box. Then I open the valve for the new flow inlet direction. My pan is same side draw. That little bit moved to what will be the new drawoff gets me to drawoff much quicker that before I started doing it.

[Robert K]

The ideas here are good and have got me thinking, now I will throw more fuel to it. What about carmelization? how does syrup/flue pan ratio affect this?
I listened to an engineer from CDL who talked about some of their pan ratios been 1/2 and 1/2 to promote good carmelization? is there flavour differences? do you run higher sap levels to slow boil down to create more ?

[bmbmkr]

Adding a question for clarification. Do you have to keep the raised flues covered with sap to prevent scorching, and if so, the deeper sap in the flue pan requires another float to reggulate less depth in your front, flat syrup pan? Thanks in advance, came home this morning with a 4x8 sheet of 304 20 ga- $104 from Dillon Supply! (They don't stock 22ga here, and shipping would eat me up)

[MISugarDaddy]

You must keep the raised flues covered with sap and you will need a float box for the flue pan and one for the syrup pan, because of the difference in levels of the sap in the two pans.
Gary

[n8hutch]

You must keep the raised flues covered with sap and you will need a float box for the flue pan and one for the syrup pan, because of the difference in levels of the sap in the two pans.
Gary , This is somewhat True, All you really need is a way to regulate the sap level in your flue pan, and A way to regulate the sap level in your flat bottom or syrup pan, If you are building your own rig this can be accomplished with Ball Valves and A little plumbing . I have run an evaporator this way, it just requires more attention, once you get into a rhythm you can more or less leave the valves set where they are, maybe open slighty when drawing off syrup.

Float Box's are A luxury in some ways, they are nice to have & I am sure some people will say that they wouldn't go w/o them.

Some people have made their own float box's as well.

[maple flats]

Technically you could control the different levels with ball valves, but to me it is just asking for trouble. With a real good fire going, a distraction could cost you your pan, and the whole sugar house, and if that is close to your house, maybe that too. I wouldn't want to take that risk. Especially if you are bottling at the same time, as I sometimes do.

[n8hutch]

Technically you could control the different levels with ball valves, but to me it is just asking for trouble. With a real good fire going, a distraction could cost you your pan, and the whole sugar house, and if that is close to your house, maybe that too. I wouldn't want to take that risk. Especially if you are bottling at the same time, as I sometimes do. while All that is true you could have a float stick or hang up & all those things can happen as well, point is you have to pay attention to your right all the time, with or w/o float valves. There's plenty of people boiling without them.

[Flat Lander Sugaring]

Thads runs his 6x16 with a ball valves he does 120+ and hour in syrup

[n8hutch]

Thads runs his 6x16 with a ball valves he does 120+ and hour in syrup That's cooking, I miss Thad's Posts on the trader, he had great perspective on do it yourself type of questions. Especially big production wise.