stack temp

[KING MAPLE]

I have been told the I maybe loosing to much heat out the stack. With my 2x6 wood fired evap it takes about 5 hr. to draw off after start up.
Then 1 and one half to 3 hrs between draws after that.
Sap depth is just a little greater than 1"
I check stake temp, it runs about 260 dregees when boiling.
Any suggestions ????

[psparr]

Not enough heat out the stack. They say 800 stack temp is ideal. Do you have a hard boil in the pans?
How much are you drawing off at a te?

[DonMcJr]

My stack is about 800-900 F... Try smaller split wood and pack it in and criss croos the rows. Once I pack it in I add 4-5 Pieces about every 10 minutes...and keep criss crossing...

[nymapleguy607]

My stack runs at 1200-1300 degrees with an inside probe type thermometer. I might be going a little hot but I can boil off around 52gph.

[PerryW]

I have been told the I maybe loosing to much heat out the stack. With my 2x6 wood fired evap it takes about 5 hr. to draw off after start up.
Then 1 and one half to 3 hrs between draws after that.
Sap depth is just a little greater than 1"
I check stake temp, it runs about 260 dregees when boiling.
Any suggestions ????

When you say 5 hours to draw off after start-up, are you starting with raw sap in the entire evaporator? Because that about right is the pans are NOT sweetened.

Also, time between drawoffs is really not a good measure of evaporator performance. What is your evaporation rate in gallons per hour?

[Teuchtar]

King Maple,
On my 2x6, when the stack temp is under 450, I find the boil is way too slow. I keep mine at about 650 to 750.
I wonder if your temperature indicator is accurate ? Stack temp of 260 sounds way low.

At 12-1300 degrees, wow ! My sugarhouse would be burning down at that stack temperature. Is that indicator accurate ? You'd be able to see it glow even by daylight.
I believe that if the flames are extending past the flues, then you are wasting the heat.

[JAMIE]

On my 2 x 8 inferno with a max set of pans i boil best at 1000-1100 .I have a double wall 10 inch stack and use a 4 inch probe in the stack.Anything less and i get a lazy boil in my syrup pan.

[nymapleguy607]

King Maple,
On my 2x6, when the stack temp is under 450, I find the boil is way too slow. I keep mine at about 650 to 750.
I wonder if your temperature indicator is accurate ? Stack temp of 260 sounds way low.

At 12-1300 degrees, wow ! My sugarhouse would be burning down at that stack temperature. Is that indicator accurate ? You'd be able to see it glow even by daylight.
I believe that if the flames are extending past the flues, then you are wasting the heat.
I have not checked that thermomter against any others so it could be off. I don't get any red glow from the stack.

[michiganphil]

King Maple,
On my 2x6, when the stack temp is under 450, I find the boil is way too slow. I keep mine at about 650 to 750.
I wonder if your temperature indicator is accurate ? Stack temp of 260 sounds way low.

At 12-1300 degrees, wow ! My sugarhouse would be burning down at that stack temperature. Is that indicator accurate ? You'd be able to see it glow even by daylight.
I believe that if the flames are extending past the flues, then you are wasting the heat.

I've been told a stack temp of 650 - 750 would be if you are using one of the magnetic stick on type thermometer. The actual temp. of the flue gases inside the stack will be closer to 1100-1200, so you would get that reading with a probe type thermometer.

[TerryEspo]

Anyting less than 550F on my stack, (magnet thermometer for woodstoves ) and the boil is bad, time to reload. After a reload and it catches good after 3 mins or so, stack goes to 750ish for 10 mins or so. The cycle continues. That is all with no blower at all.
That is with a flat pan, no flues,,,I wish !!

Terry

[maple flats]

I ran up around 800-1100 before AOF and saw a ball of fire in the night sky when unburnt gasses got some air. Now I get about 450-600, because the gasses are being burned under the pans and in the firebox. These are with a probe thermometer in the stack.
If your thermometer is in the stack and is even close to accurate, you need to fire harder, split finer, refuel sooner and give it more air. Any of these can slow the boil. When I had a 2x6 I ran constant draw after it got concentrated enough. I would watch the temp and draw at 7-8 degrees above water boil. I only drew a very slow stream. Sometimes I got it to draw 45 minutes to 75 min. before I had to stop because the temp dropped. With my 3x8 I have gottem a few draws of over 2 hrs. Drawing this slow and steady eliminates mixing in the pans. If you draw too fast you create a mixing as new inflow comes rushing in.

[GratiotCoMiMaple]

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I have not checked that thermomter against any others so it could be off. I don't get any red glow from the stack.

I have a 2x6 grimm lightning raised flue and the condar stem type flue thermometer runs at about 1200 degrees for best boil. It tends to stay in the 1150 to 1250 range but occasionally gets up to 1400. No red glow from the stainless stack (black steel stove pipe may glow). No flames out the stack either, have lots of embers out the stack though. I have air under fire with a 265 cfm blower on a controller. Unfortunately, I don't get close to 52 g/h. Average about 35 g/h with a hood and pre-heater. Have got up to 40 g/h at the most. I would like to know what you are doing to get it up to 52 g/h. I am not sure I could reach that with bone dry wood. I think I would loose a lot of heat up the stack.

Kurt

[nymapleguy607]

7729773077297730

I have a 2x6 grimm lightning raised flue and the condar stem type flue thermometer runs at about 1200 degrees for best boil. It tends to stay in the 1150 to 1250 range but occasionally gets up to 1400. No red glow from the stainless stack (black steel stove pipe may glow). No flames out the stack either, have lots of embers out the stack though. I have air under fire with a 265 cfm blower on a controller. Unfortunately, I don't get close to 52 g/h. Average about 35 g/h with a hood and pre-heater. Have got up to 40 g/h at the most. I would like to know what you are doing to get it up to 52 g/h. I am not sure I could reach that with bone dry wood. I think I would loose a lot of heat up the stack.

Kurt

I'm boiling on and Intensofire style arch, with air under the fire and in front through the door and behind the fire. The day I got 52gph I had probably 3/4 of the flue pan boiling hard. For me I could never get above 44gph burning bone dry wood, it would ignite too fast and then not produce flame. What worked the best was seasoned hardwood about 4" diameter pieces. These had enough moisture in the wood to make smoke which was reburned right under the end of the flue pan.

[mellondome]

I have a grimm lightning raised flue 2x6 with hoods and preheater. I get consistent 50 gph. I also run my pans shallow 1/2 inch in the front and just covering the flues in the rear. I only have a blower under the fire and have to limit it so as to not boil the sap into the preheater drip pan or into the hood channel. Last night, there was a glow all the way around the door (it is an insulated door and arch) and the space between the back pan and the stack also was glowing. ( was pushing closer to 53gph last night) No clue what my stack temps run.. other than you don't stand back there!! I fire every 5 min. and add defoamer in the the flue pan float box before every fire.

Do you clean your flues before every boil?
What size wood do you use? how dry?
How deep do you run your pans?
What is the temp from your preheater?
How much space between your flues and the material under them?
Did you restrict the space under your stack for draft control?
How much air is hitting your pan from breezes? are you inside with the door closed?

all of the above effects your boil rate greatly.

[GratiotCoMiMaple]

I have a grimm lightning raised flue 2x6 with hoods and preheater. I get consistent 50 gph. I also run my pans shallow 1/2 inch in the front and just covering the flues in the rear. I only have a blower under the fire and have to limit it so as to not boil the sap into the preheater drip pan or into the hood channel. Last night, there was a glow all the way around the door (it is an insulated door and arch) and the space between the back pan and the stack also was glowing. ( was pushing closer to 53gph last night) No clue what my stack temps run.. other than you don't stand back there!! I fire every 5 min. and add defoamer in the the flue pan float box before every fire.

Do you clean your flues before every boil?
What size wood do you use? how dry?
How deep do you run your pans?
What is the temp from your preheater?
How much space between your flues and the material under them?
Did you restrict the space under your stack for draft control?
How much air is hitting your pan from breezes? are you inside with the door closed?

all of the above effects your boil rate greatly.

Thanks for the info.
Finally broke down and bought a flue brush and it broke the first time I used it. Couldn't get it all the way to the back of the pan though. After I cleaned the flues up front was when I got up to 40 g/h.

Wood size is 3-5" and some dryer than other. I keep it under 17% moisture.

I keep the pans at 1.5" in syrup and Flue. I would be a nervous wreck running as shallow as you do.

Pre-heater temp is coming in at 160-190 degrees. If I close the damper much more I get steam out the bottom of the hood.

There is 1/4 inch under the flues and there is some restriction under the stack with a couple of half bricks stacked in there.

I keep the air movement to a minimal. If it gets too hot (80 degrees is too **** hot for me) or moist in the shack then I open windows or doors just enough to cool it down some.

Been adding wood every 5 minutes and adding a few drops of defoamer at the same time.


Kurt

[mellondome]

if you start lowering your depth, you will start increasing your boil rate. This will also make your drawoffs smaller but more frequent. which will help make your syrup lighter. From 1.5" , i wouldn't advise jumping to .5 , but try stepping back to 1 or .75 in the flue pan. this is the place most of the evaporation takes place, and you shouldn't have syrup tempting to burn. Nice thing with a raised flue is you can run the pans at 2 different depths.

[GratiotCoMiMaple]

if you start lowering your depth, you will start increasing your boil rate. This will also make your drawoffs smaller but more frequent. which will help make your syrup lighter. From 1.5" , i wouldn't advise jumping to .5 , but try stepping back to 1 or .75 in the flue pan. this is the place most of the evaporation takes place, and you shouldn't have syrup tempting to burn. Nice thing with a raised flue is you can run the pans at 2 different depths.

Thanks, I will give it a try.