flue pan

[ir3333]

I have used a continuous flow flat pan for the past two years.This year i have upgraded to
a drop flue rear pan and small front syrup pan on the same arch.
For those who have gone from a flat to a flue pan how much did your boil rate increase..25%...50%??

[maple flats]

What are your pan sizes and how deep are the drop flues and how fast did you boil on the same size flat pan? We can give an educated guess once we get those answers.

[ir3333]

OK..last year 18' x 60" flat pans....my best was 14 gph but a lazy enjoyable average after a few boils was about 10
Still 18 x 60 but rear pan is now 18 x 48 drop flue with flues 2" wide x 3" deep.I fire about every 25 min. or so...just enough to relax and maintain the boil.
'kinda like your car will hit 100 but we don't drive them wide open lol Hoping to start at about 9:30 a.m. put a 80 - 100 gallons through and be done at 4:30

[Robert K]

A little info on your arch please, I have a 2x3 drop flue 4.5 inch deep and a 2x4 flat continuous flow . 20-25 per hour boil rate is a easy fire , crank up the blower and 35 per hour, but that is no bevy’s and constant fire. My arch is insulated and blower is pressure (not a furnace blower). You should be fine within the time you stated.
Have fun and 😊 enjoy

[maple flats]

A relaxing boil is not the best to get the best syrup. You want to push it at least some. For example, I can push mine to get 80-85 GPH, I tend more often to run a about 70. A routine of firing every 25 minutes would likely result in only getting maybe 45-50 gph.
Your choice. The faster you boil the better the syrup.

[ir3333]

Thanks MF...maybe i worded that poorly, I keep a good boil but i use bigger wood to last longer...i'm the lazy one.When I was drawing syrup from just my divided flat pan my first year it produced small quantities quickly but made light syrup with not much flavour.So last year i built a new arch and added a front syrup pan where i can hold the syrup and boil longer to get more color and flavour? This year i replaced the divided continuous sap pan with a drop flue pan and added a ramp hoping to increase my gph...but i can still hold syrup in the front syrup pan until it is where i want it. I'm also going to swap pans this year mid season and use the syrup pan as a preheater on fire at the flue and draw syrup from the continuous drop flue pan in front. My ultimate goal is one divided flue pan...sap in, syrup out.No syphons, float boxes. preheaters...just one simple pan.

[ir3333]

A little info on your arch please, I have a 2x3 drop flue 4.5 inch deep and a 2x4 flat continuous flow . 20-25 per hour boil rate is a easy fire , crank up the blower and 35 per hour, but that is no bevy’s and constant fire. My arch is insulated and blower is pressure (not a furnace blower). You should be fine within the time you stated.
Have fun and 😊 enjoy
tx Robert...so your arch has a 2x3 rear drop flue with a 2x4 continuous front section where you draw syrup...2x7 total?

[ir3333]

that sounds like a truly spectacular system at 85 gph MF! What are your thoughts on
putting my drop flue pan at the front of the arch and drawing near syrup from it?
Some have told me this is too risky?

oops..just read my older thread where you cautioned drawing near syrup from the drop flue pan located
at the front.Tx MF

[maple flats]

My thought on having the flue pan in front and syrup pan in back are that you would not get enough heat in the syrup pan. If that would have worked, after evaporators with flue pans have been made for over 120 years, one of the big manufacturers would have one like that. The maple syrup equipment business is trying new ideas to improve the boil rate all of the time, you can't possibly be the first to think of that.
My question is relating to your statement that you "hold the syrup in the syrup pan". Do you mean you go to over density? I'll assume you draw off by temperature, what is the typical draw off temperature of your syrup?
You usually want to draw off syrup at 7.1F above the boiling point of water that day. To get the boiling point you need to test it, for an accurate reading the water needs to be at a full rolling boil, not just as it starts to look like a sort of boil. Also, you will do best if you can set it up to draw off in the front pan, but the end towards the flue pan, that's where it's hottest.
In my evaporator, I have a 3x5' flue pan and a 3x3' syrup pan. I have same side reverse, meaning I switch the flow in the pan, by closing one valve and opening another on the same side of the pan (while both valves are closed I move the float that controls the flow thru the open valve. The design of mine has been improved in later years, but mine has 2 draw off boxes, one at the front of the pan, and another at the end next to the flue pan. I get far better results when the draw is from the rear draw off, but I switch the direction of flow to keep the pan the cleanest during a boil. However, I do run longer when the back draw off is where the draw is, and less time when it's in front.
Newer designs have changed the flows patterns so the draw off can be at or close to the flue pan rather than at the front section. Mine also has another issue, it's a cross flow, meaning the 4 channels go from across rather than front to back. That compounds the draw off a litle, when I draw from the back, I'm getting what is boiling in the back channel, fully heated by excellent flame/heat under it. When I draw from the front, I'm drawing from the front channel, where there's a little less heat and that channel has an overlap on the arch itself, further compounding the issue. If I were 10 yrs younger, I get 2 pans made (I keep two pans, one being cleaned while the other is in use) that are designed so the draw off is by the flue pan, but the flow can be reversed while keeping the draw by the flue pan.

[ir3333]

When i have 219 in the syrup pan i extend the boil by adding from the flue pan so it boils longer.
I was considering putting the syrup pan in the back just to use as a preheater...it would not boil because it will be fed raw
sap from my gravity feed system which i adjust to match my evaporation rate.
With that arrangement i would be taking the syrup off the front drop flue pan.Some guys i know draw at 221 and stop at 218.
I adjust the specific gravity, finish and filter at seasons end on propane.

[maple flats]

Well, I guess whatever works for you.
In my case I use an auto draw and A Marcland Baro/boil meter, then I adjust as needed. The meter gives you the boil temperature at the currant barometric pressure, then I add 7.3 and that's where I set the auto draw. Then I use a hydrometer to test during a draw and adjust if needed. Once I got that meter, I was surprised how much the barometric pressure goes up and down even when you think it would be rather constant.

[ir3333]

you are right about that.I drew syrup last year kissing 221 on the thermometer and when
i checked it with the hydrometer is was still not syrup. I'm very lucky..i'm retired and only
tap 50 trees.So i have lots of time and it is very easy to try different things on such a small
operation. I've welded / made 3 arches in three years and have used at least 6 pans.
This years experiments may not work well at all. I'll know after the season is over? Input
from experienced guys like you is a major bonus!