How Deep is your Boil?

[Helicopter Seeds]

Just wondering what the consensus or general practice for how deep you should run the sap in your pans. I recall from Thermodynamics and Heat Transfer classes that you have better efficiency with the larger difference in temperature. But once you get boiling, that only changes when you add sap.
Last year I originally had my pans inside the bricks, but I ended up burning sap on the sides. I re-arranged my bricks and set pans on top, and eliminated the side burning. It had little impact on boil rate. So seeing traditional flow type pans, I suppose the concentration at the end is key, not sure what effect the depth would have. I have actually considered simple siphon tubes connecting pan to pan to create a flow.

I just added two 4 inch deep pans to the three 6 inch deep pans I used last year. If you only need an inch deep, then they should be just as effective.

[psparr]

As low as you feel comfortable running. The lower the faster boil rate.

[brookledge]

As Omas said the lower the better. That being said going too low will lead to problems. In your case since you have individual pans and im assuming you keep adding to them as you go Id maintain between 1 and 2 inches. When you have an evaporator with floats that is what most maintain for levels
Keith

[boondocker]

It is what you feel comfortable with, the lower you run them the quicker everything happens. I run my flue pan 1/2" over the raised flue and my syrup pans I run 3/4 to 1" deep Depending on how the evaporator is running and weather I am running the blowers or not. I was running only 1/2" in my syrup pans but I found that at full boil things where happening to fast and was unable to draw off fast enough and ended up burning one of my pans. A very costly mistake in the height of the season. I would run as deep as you can and still keep a very rapid boil. Best of luck!

[maple flats]

On a closely watched flat bottom or float controlled pan 3/4-1" is great. With the steam pans with the rounded corners I'd likely go 1.5" and you need to watch it carefully, you can't just walk away and come back several minutes later.

[wnybassman]

I prefer to run 3/4" to 1" but I have to run a little deeper for the thermometer to be halfway accurate for draw-off. Makes for bigger draws though.

[Bucket Head]

Back when we had flat pans we tried to keep it right around an inch. But you had to watch them! But it boiled great. The less liquid you have, the better your boil will be. Less liquid for whatever heat your producing to boil it.

Interesting note: I was curious what LaPierre recommended for my flue pan and ask the owners son yesterday at the V.V.S. maple conference. He put his forefinger and thumb almost together, to about an eigth of an inch and said, "This much. The flues only need to be wet".

Steve

[Helicopter Seeds]

Thanks all for the info. I think I will try the low level for my first boil this year. Now just waiting on tapping and sapping.

[Burnt sap]

We run about 1" to 1.5" in the front pan and 6" in the pre heater.

[blissville maples]

boy you guys running one inch are brave, must not have a single warp in pan!! do you use a lot of defoamer? cant imagine you would want to foam up at that level! wow

[PerryFamily]

I shoot for 1.5-2" on 10-12%. This is on a 3x8 raised flue
Basically you'll just make a bigger batch.

[mellondome]

Couple problems with running deep. If you run deeper than the channel passages in your pans, the defoamer will not follow the sap flow as it resides on the surface. This will cause foaming issues in the front pan. The longer it takes for a bubble of air to break the surface, the slower your evaporation rate becomes.
For what it's worth. On a 2x6 raised, flue pan , sap is always just wetting the top of the flues. With raw sap front pan was @ 1/2 inch. With 18% the flue pan remains just wet, front pan is now @ 3/4 inch with a near constant drawoff. No batching. Also no boiling sodas and no leaving things untended.

[blissville maples]

wouldn't it take about 3 1/2- 5 inches to cover divider passages?? that's a little deep. 18% with just over flues, pphhwweww! yea don't blink, hopefully you have no issues with incoming concentrate, very brave. 1/2'' in front pan, I don't think so. you must have some dark spots on pan cause any high spot of 1/4'' will only leave 1/4'' sweet. I don't know if I could believe that, half inch is thickness of my pinkey. hopefully you can draw off fast, at that low only trickle would come off my pan trying to draw. interesting....

[WESTMAPLES]

18% with just over flues, pphhwweww! yea don't blink, hopefully you have no issues with incoming concentrate, very brave. 1/2'' in front pan, I don't think so. you must have some dark spots on pan cause any high spot of 1/4'' will only leave 1/4'' sweet. I don't know if I could believe that, half inch is thickness of my pinkey. hopefully you can draw off fast, at that low only trickle would come off my pan trying to draw. interesting.... \ dude really..... we are sugar makers not children playing with shinny things ...... nobody asked for your input or opinion, this site is to help others and learn not beat on poeple that know what they are doing.... nobody told you how much milk to put in you cheerios this morning.... 1/2`` i don`t think so lol

[lakeview maple]

I usually run between 3/4 to 1 inch in my front pans and in the flue , Ive done that way for the last 5 years and never had a problem. Its a matter of keeping an eye on equipment ie checking the head tank, watching the float box ect. Its called making syrup and people who are a lot smarter than Ill ever be have done it with success for many many years.

[wiam]

\ dude really..... we are sugar makers not children playing with shinny things ...... nobody asked for your input or opinion, this site is to help others and learn not beat on poeple that know what they are doing.... nobody told you how much milk to put in you cheerios this morning.... 1/2`` i don`t think so lol

Actually the original poster asked for opinions.

[WESTMAPLES]

yes wiam you are right HS did ask for opinions... it just burns my sap to see someone dragging others in the mud and making unuseful comments to others useful info in many threads on this site..... i gets old

[blissville maples]

yea really dude count on it....... exactly opinions, u wanna run 1/2'' west, burn your pans and shorten life of them go ahead im not paying for it, yes shiny things folks like you have too many of them and don't know how to take care of them, youll see, would start looking for a new pan now. ill continue to use my pans for years to come. you can see earlier post guy no longer runs 1/2'' burnt his pan. seriously bud. hhmmm mass.....no wonder (sorry). u know how warps are made, by having your sap over 220 degrees, and if your first compartment is 219 and cant draw fast b/c no push due to low level, good luck keeping 2nd compartment under 220. now with warps how can you possibly run 1/2'' with a 1/4'' warp. that would leave 1/4'' over warp, then figure in a foam up....burnt!!! I sometimes sound like im giving flack but its constructive criticism take it or leave it. top of my window is 2'' I run no less than 1 inch below that as many other say 1 to 1.5'', im not risking a thousand dollar pan, especially when I have 500 gallon 12% stacked up

[blissville maples]

I was running only 1/2" in my syrup pans but I found that at full boil things where happening to fast and was unable to draw off fast enough and ended up burning one of my pans. A very costly mistake in the height of the season.

[adk1]

I set my float box so that the sap is about 2" deep

[WESTMAPLES]

seriously bud. hhmmm mass.....no wonder (sorry). lol hear that alot but im from western mass not southie bud . i drive a nice 1978 chevy 1 ton driving it 16 years,weld for a living with nice used equipment, and live in a house from the 50`s, the shinest thing i have is my evap...... (i take care of what i have ) and yes things happen fast thats why most learn there limits and stay with that..... i haven`t burnt one yet, nore do i want too

[PACMAN]

I just got an ro this year so im looking forward to using it. I have always run my 2 by 8 drop flue at 1 and 3/8 inches. Would that be a good starting point for say 12% concentrate?

[blissville maples]

right on! one other thing ive been thinking. I own a drywall company and hang a ton of board 1/2'' board coincidently. I use tape measure all day every day. sometimes half inch is deceiving to some so be sure your measure is accurate not just eyeball job, also your draw off box is sometimes slightly higher than middle of pan. and on my rig if I wanted 1/2'' in my syrup pan my drop flue pan would dripping solder.

[WESTMAPLES]

yeah like i do and others have suggested if you run a drop flue pan with one float box and want a better boil in the flue pan and still want a good depth in the syrup pan run a 1/4 or 3/8 strip of steel under the rail gasket on both sides of the flue pan. you now have a shallow hard boiling flue pan with a deep level in the syrup pan. setup it up right, level it and now you have the best for both pans. raised flue i have no idea i run a 1/4 strip under the flue pan rails so my syrup pan has 1 in and 3/4 in flue starting, and depending on how hard i run it i may bump it up a 1/4 or 1/2 overall to keep it safe. i also pre mark my float rod with depth measurements and a tape to check pan depth before and during a boil.

[blissville maples]

Its been 12 months and I don't really measure but I run an inch or so in flue pan. not sure if your using oil or not, but I have no issues getting nice boil, I use wood. if your stack isn't tall enough, and or your firebox is too close too floor that will be a major issue for a poor boil, some may compensate by running shallow depth. you wont have proper draft and will not have hot flame. I have my arch up on some 8x4 blocks to get a nice amount of air under firebox. also, don't forget there are poor boiling days and good boiling days where you get a nice full boil all the way back to the flue , based on barometer and humidity.

[WESTMAPLES]

wood fired and i do the pan step for more GPH with everything else already dialed in 100% thats the last thing i could before adding a jet turbine to make it fly ......lol. seriously thought, shallower depth = faster evap rate in flue pan, deeper concentrate in the syrup pan = safety from burning, which to me is the best of both worlds and there you have it

[Helicopter Seeds]

Thanks for all the input, really helps.
As an engineer doing a new hobby, I may over-think and analyze things. But I also like to start with a basis of understanding what has historically been good, tried and true.
So then On the technical side, I had asked the question before researching the thermodynamics. It has been nearly 30 years since Thermo class and I have forgotten a lot, except that it was a difficult subject with words like entropy and enthalpy. One thing I know is that the heat transfer is always more efficient with a larger temperature difference. For my weekend batches I have a given amount to boil through, say 120 gallons, that all must be heated to a boil. So the rationale is to squeeze as much cold sap into the pan to maximize that efficiency. The reality is that before any efficiency is calculated, it takes over 5 times the energy to evaporate a gallon of water as it does to raise the temperature from 32 °F to 212 °F. In practice, engineers try to target our efficiency in the area of most good. So that means making the evaporation phase more efficient means more than the heating to boiling phase. Now the heat equation for the boiling sap basically says energy in = energy out. and of course energy out includes losses. The biggest loss is heat convection from the sides of the pan!. Unless the sides are well insulated, a deep boil will inherently lose much more heat than the shallow boil. So next goals are to insulate the sides, but keep a shallow boil covering the bottom where the heat comes in. And for that matter, using a full 30 qt stockpot for finishing wastes tremendous energy from the sides.

In other words - the thermodynamics tell us what you guys all said - keep the boil depth low. (and yes a flue pan, or preheater can maximize the smaller portion of the equation.) Thanks!