Newbie Stack Temperature question

[Brokermike]

This is my first year boiling by myself. Years past I have been relegated to shuffling wood around, helping friends tap, and drinking beer. Now that I'm all set up myself I have some questions.

I have a 2x4 oil tank setup (it's all firebricked etc), with the draft door open the rig sounds like a jet plane flying overhead, it heats up quickly, boils sap like crazy and otherwise cranks. It does however shoot flames about 12" out of the top of the stack. I only can see this glowing afterburn at night. Having only been a helper in the past is it safe to run the rig at this level and what should my stack temperature be?

If I close the draft door it still boils well (albeit much slower) and my stack temperature stays at around 300-400 degrees.

I'd gladly take opinions on what level I should pursue

Thanks

[Brent]

Welcome Brokermike

I've and the same flame thrower effect on our first small evap and it when in that mode it will eat wood at an amazing rate.

Your stack temp reading needs to clarification. Are you using a thermometer with a stem that goes through a hole in the stack and into the stack gasses or a magnetic that sticks to the side of the stack.

In the roughest terms, something around 1100 degrees actual gas temp seems top be a good balance between boiling rate and wood consumption.

If you're using a magnetic one the reading can vary quite a bit depending on when you attach it.... on a flat or on a round part of the stack, height etc

[Justin Turco]

Hey Mike, I love seeing flames come out the stack, but oh boy what a waste of heat. How about a damper in the pipe. That might hold the heat in the firebox a bit better. I probably run one of the higher stack temps that you'll see. 12-1,400 degrees in my 2X6. I just build a fire...whatever I get for a stack temp is what I get. If I had a 2X8 I'd build the same fire and see a lower stack temp. Anyway..I'm wasting some wood too. I don't think it is uncommon to see flames out the stack on a flat bottom pan with a relatively short stack. My barrell stove evap. used to do the same thing.

[Brokermike]

It is a magnetic stick on temp gauge stuck about 2' up from the pan.

I think adding a damper might be a good idea.

Any other thoughts?

[Justin Turco]

I'd just like to add, leave the draft door wide open, but block the escape of the heat with the damper in the pipe. Just a my opinion :)

[lenny]

I have a 2X4 pan 6" from my chimney with a 26X16 pan in front of that or right over the firebox. This is my first year cooking so I may not have this exactly correct yet. I put my damper about 16" up on the chimney with the thermometer (with the magnet on the inside) about 8" above the damper. My first cooking I kept the temperature about 1200°. The next cooking I found that 1400° gave me a stronger boil. I have 8' of stove pipe which sticks above the roof about 3' and I have not seen flames shooting out the stack. That was my goal with the damper. with experimentation I found that near the end of the cooking, near the time I need to take the syrup pan off I can control the boil somewhat by pretty much closing the damper to keep more heat in the firebox or opening it all the way to lower the boil.