What is your stack temp?

[Stoneduester]

I am curious to hear what people are getting for a stack temperature when you're up and running? What is the general configuration of your rig? Thanks in advance, -Alfred

[wiam]

My 2x6 Mason with a tube style back pan and a very large blower would run over 1500 degrees. But that would boil like no 2x6 I have seen. My 3x12 runs about 675 but it is oil fired.

[Woodsrover]

My 2x4 Mason with the blower turned way down low will run 600-700. Without the blower it runs a steady 600.

[abbott]

Just put a thermometer in less than a week ago, so have only had 2 boils so far. Running 800-900. 40"x10' older arch, not airtight, natural draft.

[Tweegs]

One variable that needs to be accounted for when discussing stack temps is how far up the stack folks are getting their readings from.

I use a thermocouple and located it at the top of the first round section of stack.

Two reasons for this:
1. The round sections are cheaper to replace should the hole I drilled in the stack rust out.
2. It puts the thermocouple wire well above the point someone would clothesline themselves on it.

So I’m measuring about 6 feet above the base of the stack.
Here, my 2x6 measures 800-900 degrees without any forced air.
I’ve heard said the temp will drop about 100 degrees per foot, I wouldn’t swear that is correct.

Also, my thermocouple isn’t calibrated so I don’t know how much correction to apply to the measurement and I don’t know if the amount of error is linear throughout the measurement range.
We use this reading only as a reference. What we do know is that when the thermocouple registers 8-900*, we’re in the sweet spot for evaporation rate vs. wood consumption.

Boy, that was a long winded way of saying I don’t really know what my stack temp is.
:lol::lol:

[Robert K]

At eye level which is about 5 1/2 feet the stack probe from leader usually reads 900 after firing. With hardwood I can run 20 minutes between loading, load when it drops below 800. The blower intake is limited in order to control excessive sparks put out the stack. Arch length is 2x12. 
Still experimenting and improving!!

[maple flats]

Since adding high pressure AOF and AUF several years ago, my stack temp is usually between 600-700 with a super hot inferno in the arch. Before the AOF/AUF I ran as high as 1500 at times and was about 900-1200 often.
My set up, besides AOF/AUF is a 3x3 syrup pan and a 3x5 flue pan with 10" tall flues. I have about 1" space under the flues, forcing the heat into the flues and both pans boil real hard.
Also, before AOF/AUF I had a fireball at the top of the stack, where the super heated unburnt gasses re-ignited as they got more oxygen, I now have none of that.

[wiam]

It should also be noted that a probe will read higher than a surface thermometer.

[maplemas]

I run around 1150 after firing and add wood at 950..

[RileySugarbush]

Interesting data points. Last year, 2x6 with 3' drop flue. This year, 2x8 with 6' drop flue. Same firebox, the only other difference is a slight change in AOF nozzle size, a bit smaller and I plugged a few. Huge difference in stack temp on a prob thermometer.

Old rig, 1400 to 1800°F depending on how aggressively fired. Now 600 to 950. Much more efficient with all the improvements in heat transfer. A lot fewer sparks out the stack, too!

[Sugarmaker]

I have a old wood stove temp indicator (its about 4 inches in dia ) it is screwed in place on the exterior of the base stack (no probe) about 5 feet above the arch.
The old pans were very inefficient ran about 600-700 deg F. The new pans: drop flue, 9 inch deep (14) pull that same indicator down to 400 deg F and it stayed withing 20 degrees all season. At first I was concerned, but it boils around 130 GPH so its getting most of the good out of the fire before it exits the arch.
Regards,
Chris

[ennismaple]

I eyeballed the calibration of our stack thermometer so the accuracy is probably ±20 F but our evaporator hums along at about 750 F stack temp. Less than that and the boil isn't rapid enough for me. More than that and we're throwing smoke out the stack and reloading wood too frequently.

[Waynehere]

We started out running the AUF at half throttle and the stack was running 6-700, but our boil rate was about 40 gph. We were firing about every 15 mins. So we went full throttle and got our gph up to 50-55 with stack temp running 900-1000. We are now firing every 10 mins, but the increase was worth it to us. Maybe when we get an RO we can throttle that back to be more efficient. :)

[wmick]

WOW - I'm surprised by the high stack temperatures reported... I have no experience yet, but read in a Leader instruction manual to keep the stack around 150F..

With these kinds of heat in the stack, Id think you could almost add another 8'or10' of Pans...:o

[ennismaple]

I have no experience yet, but read in a Leader instruction manual to keep the stack around 150F..

Something's not right - there's no way our pans would do anything more than simmer if the stack temp was 150 F. At 1900 F at the back of the syrup pan there's no way you can get that much heat out of the combustion gas in a 10 foot contact length. Maybe if you're running a piggyback pan system and routing all the gases through tubes in a secondary pan before the stack but not with a forced air arch.

Lapierre's published numbers from actual testing of their Force 5 is:

http://www.equipementsderabliere.elapierre.com/down/gestion/groupeproduit/436/files/1.pdf

[wmick]

Something's not right - there's no way our pans would do anything more than simmer if the stack temp was 150 F.

Kinda wondered about that..... Must be a typo-- (1500F probably)... below is copied from the instructions for a "Revolution Pan Set"

3. When using a wood fired arch
a. Keep stack temperature in range of 150F
b. Maintain arch ½ to ⅔ full
c. Fire consistently with small amounts of wood to maintain level
d. Use timer to stay on schedule with firings
e. Adjust firing intervals as needed to maintain an even boil

[Ranger_Andy]

I built a new arch last year for our 3x12 and added the Auber digital & probe...We found that we run max temp at 1350 and when the temp drops to 1185 we fire, so we have the Auber alarms set up and fire according to the stack temp...We are running both AUF and AOF with multiple entry points for the AOF much like the store bought arches...Same pans, but different arch...with the old traditional arch with back ramp and small fire box, the stack temps were around 800 - 900 and we got about 1.0 - 1.25 gpm sap flow into the pans...In 2016 we were running 2.25 - 2.5 gpm sap flow in and burned about 30% less wood even though the fire box was twice as large as our older arch.

[Sugarmaker]

Andy,
Impressive numbers on improving your boil rate using stack temp monitoring!
Regards,
Chris

[Brad W Wi]

Wood fired, temp probe at eye level reading 1000F degrees . Feeding wood in 7-10 minutes. 45+ gals/hr. Mostly hard and red maple with some ash in there also.

[Brian Ryther]

I believe there intention is to keep the temp range within 150F. For example we run our stack temp 850F - 1000F.


Kinda wondered about that..... Must be a typo-- (1500F probably)... below is copied from the instructions for a "Revolution Pan Set"

3. When using a wood fired arch
a. Keep stack temperature in range of 150F
b. Maintain arch ½ to ⅔ full
c. Fire consistently with small amounts of wood to maintain level
d. Use timer to stay on schedule with firings
e. Adjust firing intervals as needed to maintain an even boil

[barnbc76]

Anyone used one of those infered lazer thermometer things? I don't have a stack thermometer but my brother had his lazer thing the outside temp read just under 400 using single wall black pipe. Any clue what the inside temps would be?

[maple marc]

We run 900 degrees on our stock Leader 2x6 WSE. Hardwood, stoked every 7 minutes, draft door mostly open half to full. 10" stack, plenty high (stack diameter and height are factors often ignored). Seems to be optimal, getting 30 gph. When we started on a 2x4 without a stack thermometer, we didn't know what we were doing. We were told to run with the draft door wide open. Well, the sap was spitting way out of the pans, the stack and door were red hot, and we warped the grates. We must have been well over 1600 degrees. Longer rigs are certainly more easy to run. A stack thermometer (probe type, not stick-on type) is critical to operation.

[Ptim]

Run 700 -850 on a sunrise metal 2x8 with blower.

[Stoneduester]

I finally boiled again last night, and ran my rig with a probe type thermometer for the first time. 2x4 flat pan, 10" stack 12' tall (including base stack), 18" deep firebox, I was running steady between 1,000 and 1,150, and would reload at 950.

[treehugger]

Does your AOF deliver more air than your AUF?

[treehugger]

When I have everything dialed in my stack temp runs around 1100. I'll get 72-75 gal/hr evap rate. The fire is at an incinerator level. I don't have my AOF and AUF controllable at this point. I'm not sure if it would help with wood consumption or evap rate.

[Russell Lampron]

Anyone used one of those infered lazer thermometer things? I don't have a stack thermometer but my brother had his lazer thing the outside temp read just under 400 using single wall black pipe. Any clue what the inside temps would be?

I just bought a Snap On lazer thermometer. I checked my stack temp at the top of the base stack and was surprised to see that it was only 300*. I have auf and standard arch. When the doors were glowing they were measuring 1200*. Either a lazer measurment isn't accurate or my evaporator is using all of the heat that others are blowing up the stack.

[Sugarmaker]

I just bought a Snap On lazer thermometer. I checked my stack temp at the top of the base stack and was surprised to see that it was only 300*. I have auf and standard arch. When the doors were glowing they were measuring 1200*. Either a lazer measurment isn't accurate or my evaporator is using all of the heat that others are blowing up the stack.

Russ,
I have one of those hand held laser thermometers, but forgot to use it.:) I would guess that I would get a reading of about 400 F on the stack exterior at the top of the base stack bear the bolt on thermometer. Also I know my stack temp on this same exterior thermometer went from 600 -700 F to 400 F when I put on a set of pans with twice the surface area.
Internal probe might show 900 F?
Regards,
Chris

[wiam]

I just bought a Snap On lazer thermometer. I checked my stack temp at the top of the base stack and was surprised to see that it was only 300*. I have auf and standard arch. When the doors were glowing they were measuring 1200*. Either a lazer measurment isn't accurate or my evaporator is using all of the heat that others are blowing up the stack.

Infrared thermometers are not accurate on shiny surfaces. All I have purchased say that in the directions.

[Mark B]

Im not an expert on this topic in any way. 2018 will be my second season sugaring. Keep in mind that I have yet to set up and fire my new 2x4 that I just bought to test my thoughts on, but drawing on my experience as a firefighter, a typical steady state house fire will burn at about 1100-1200 degrees. This is a good old simple wood construction, well vented, drawing outside air, and without the influence of today's modern materials. The smoke you see from this would be a light whitish-gray, not the black as from an incipient stage fire or yellowish-gray from an oxygen starved smolder state. I would think you could extrapolate from this to the small scale of a wood box.

As you near that 1100- 1200f, you should be seeing pretty near complete combustion. This not to say that you wiont ever see higher stack temps or that you won't ever see good complete combution at lower temps. I would think though that much below 800-900f is a good indicator that you are lacking fuel and/or oxygen and much over1200- 1400f and you are wasting heat that could be applied to your pans. Im talking in that 1st foot where the heat and smoke first exit to the stack. There is always the cooling that takes place as the heat rises through the stack.

I said all that to say my best guess is that most will see stack operating temps in the 800-1400f range based on set up.