First boil of 2023 lessons and questions - measuring stack temp

[Openwater]

Just finished my first boil for the season and now got some stuff to do before next boil. One thing is replacing my stack thermometer/thermocouple. I had bought a Thermoworks thermocouple and digital meter last year but just got around to putting it on this year to try to monitor stack temps to determine when to fire. Well, the wiring/insulation inside the threaded part of the sensor melted exposing the bare wires going from the sensor to the digital meter.
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So does anyone have any suggestions for a stack temp probe/sensor/thermometer that can go up to at least 1200*F?

I did get some good info from the thermocouple during this boil, however. My stack temps ranged from 850 to 1300 depending how often and how aggressively I fired. Obviously, I got the best boil at 1300*, but keeping the stack temp there would require firing almost every 1-2 minutes. So, I started firing when the stack temp went below 900 with a small-moderate amount of wood which would typically get the stack temp up to around 1100, then gradually fall back to 900 usually within 3-4 minutes. So I at least figured out how to maintain a more consistent boil using stack temps instead of just the timer; and now I got a sweetened pan.

[ecolbeck]

Any maple supplier will have dial stack thermometers.

[Pdiamond]

Smoky Laky maks a real night temperature gauge, it is a little pricey.

[Paddymountain]

I bought a thermocouple off of ebay a couple of years ago, I’ll
try and find where it came from. My stack temps are only 425
or so. Any more than that and I can’t keep the sap in the pans!
I just see where it is boiling good and use whatever that temperature
is as a firing guide. Usually about a 50 degree swing keeps
things pretty steady

[maple flats]

All I ever used was an magnetic mount thermometer with a stem into the stack. While the SS stack did not hold the magnet, the stem stayed in the stack. I only used it to witness the effectiveness of my AUF and AOF on stack temp. Before the AUF AOF my stack temp ran upwards of 1200-1400F at times, after the normal reading was 800-950F,. With this I was boiling much harder, thus it showed that more combustion was in under the pans rather than up the stack. I fueled by the clock, firing every 9 minutes, where as before adding AOF AUF I fired every 7 minutes. In both cases I used a timer. By the way, with the AOF/AUF I gained between 18-25% increase in boil rate, on less wood. It saved me about 35% of the wood.

[Openwater]

I know my stack temps are pretty high because I only have a flat divided pan w/o flues, so less heat transfer to the pan and more heat up the stack.
My other problem is that my stack is only 6" diameter, so some of the stack probes/sensors are too long to fit in my stack unless I mounted it on an angle.

[ebliese]

Openwater,

I am in the same boat as you-flat, divided pan and high stack temps. I had originally purchased a dial thermometer (200*-1000*F) from Sugar Bush Supplies in Mason, MI. They are a Leader dealer so you could get that particular stack thermometer at any Leader dealer. It probably would have worked fine had I mounted it higher in the stack (8" stack) but I opted for just above the base stack (so about 6ft off the ground). My stack temps are higher than this and the thermometer couldn't handle the heat. Since I already had a hole drilled in my stack, I opted to get the Smoky Lake dial thermometer. That one relies on gas and not a coil. It is, as Pdiamond says, a little pricey.

That is what I have done in my operation. Hopefully this info helps you in some way.

[Openwater]

I'm looking close at the 4" Smokey Lake dial stack thermometer. Do you know how long the stack probe is? Can the 10' lead wire/tube be mounted to the side of the arch, or does it need to be kept away from high temps?
Thanks for the info.

[ebliese]

The probe is 5 15/16" long. No joke. From looking at how the probe is mounted in the stack, the length of the probe inside the stack would be a little bit shorter than the 5 15/16" measurement mentioned. That is because there is a nut screwed into the stack and the probe is screwed into the nut. Kind of hard to explain without a picture and I didn't think to take any. So I think you would be ok using the probe but might want to check with Smoky Lake to be sure.

The 10' coil can be mounted on the side of the arch. There is a video of Smoky Lake employees doing this exact thing (should be on their website somewhere). The advantage there is the dial is closer to you so easier to read. I opted to run my line up and behind my arch so the dial is about 8' from me and mounted it on a 2x on the wall. I did that just because it was an easier mounting point for me. Worked well for me last season.

[Openwater]

Just watched that stack thermometer installation video on Smoky Lake website. Good info. It looks like the probe mounts into a 1/2" npt male-female fitting that screws into the stack. I could probably get 1 or 2 more of those 1/2" stainless npt male-female fittings and stack them together which would adjust how far the end of the probe sticks into the stack. Like they said in the video, would definitely need some high temp anti-seize if screwing those stainless fittings together.

[snakes14009]

I just bought two thermocouples from amazon the are "rated" to 1250C(2282F) each less than $15 i used cheap amazon ones last year and the one in my burn chamber peaked as high as 2100F but I have to replace it again this year the stack temp one is good i believe. no they are not going to last more than a season or two but. Compare that to ones that will survive with costs in the hundreds of dolla rs rangeit will get the job done

[sap_savages]

If you want very consistent boils and willing to spend some money, you may want to check this out. I've been using it for a couple of seasons now. It works amazingly well.

https://tetilengineering.com/product/stack-temperature-controller-maple-syrup-evaporator/

[Backyard boiler]

I ended up getting a Smokey lake 4 dial. It is well worth the money took a lot of guess work out of my old dial type gauge to really help fine tune my rig and keep fire’s consistent.