Hot stack please help!

[Mikemartin274]

So last year I burnt the roof off my new sugar shack. I was using the pipe that came with the evaporator. My supplier told me it wasn't high enough over the peak and caused the fire. This year I put up an insulated pipe inside an insulated pipe 10' over the peak. Boiled about 20 hours and all was good. Last boil two hours in it began to glow from top to bottom. I closed the air shutter below fire and it stopped glowing but my boil rate went down. Everytime I refueled it would glow again. Its so hot it has scorched the back of my pan. Please help I'm at a loss of ideas.

[Urban Sugarmaker]

I would consider installing air-over-fire. Do you have a blower? If so, are you using it at full blast? You should have some kind of double or triple wall pipe where it penetrates the structure. Triple wall is nice because it allows a draft of air to rise up between the out layer and inner layer to help cool the stack and reduce clearance from combustibles.

Air over fire helps a lot on my 2x4. If used just the air-under-fire blower at full speed I could probably burn my building down as well and everything around it. Not good.

This is another reason I want to convert to oil.

[mellondome]

You are burning the gases in the stack due to lack of oxygen in the firebox. Putting in air over the fire is the best fix.
For a quick help, fire more often with less wood. And each fire alternate sides of the firebox you fuel into. You should be firing every 5-7 min.

[maple flats]

Is it the stack that is glowing? If yes, you need air over fire, if it is anything close to the stack you need to protect it better from the extreme heat. It sounds like you need air over fire (AOF). Look up AOF, there are threads on here and a PDF paper on UVM Proctor site giving the specifics.
AOF will enable you to burn the gasses that are in the arch but run out of oxygen where they can add heat to the pans and then burn as they get to the top of the stack/ new air supply and re-ignite in a ball of fire.

[Sugarmaker]

I guess I am a little surprised that a small rig would get that hot? But sounds like it does. Yea you need to change something?
Tell us about how you fire the evaporator? how often? What is your stack dia I assume 6 or 7 inch? How tall is your stack.
Pictures might help too. What type of wood are your burning?

Regards,
Chris

[DrTimPerkins]

You got me all excited with that subject title....I thought you might mean you had a hot stack of pancakes you needed help with.

[maple flats]

Dr. Tim, that was my first thought too, it soon became a fire hazard issue, the stack not the pancakes.

[Super Sapper]

Though aof could help, it seems he is pulling the heat up the stack too fast. If there is not enough air in the firebox the will be no air in the stack to burn. I would look at the space under the pan and reduce it to slow the draft.

[Mikemartin274]

I have a 10" stack. What I think is triple wall. I thought the triple and double was a selling point I thought they were the same. I fire every five minutes or so about five sticks each time. I've boiled at night and don't have a firbeall at the top. The overall length is about 20'. I'm going to see if I can load some pics. And I did have a hot stack of pancakes for breakfast. Yummy!

[Diesel Pro]

Sounds like you have some issues to deal with, but in terms of stack I'd say that the Canadians have the best stuff.

http://icc-chimney.com/en/excel

Not that you are worried about the interior building creosote or anything. We've been firing our RSF delta fireplace for 8 seasons now. We ran a brush down it once just because we were up there, but it hasn't needed to be cleaned yet.

[Mini_Maple_Men]

Does your stack ever look like this? I have less than 1" air gap between my firebrick and the bottom of my pans and if my auf isn't set on low with half the intake blocked my stack looks like this just after firing!16220

[Sugarmaker]

Does your stack ever look like this? I have less than 1" air gap between my firebrick and the bottom of my pans and if my auf isn't set on low with half the intake blocked my stack looks like this just after firing!16220

Yep thats too hot! Shut the draft down and dont fire as often?
Regards,
Chris

[motowbrowne]

Yep thats too hot! Shut the draft down and dont fire as often?
Regards,
Chris

Or stretch that thing out and add a 5' flue pan. :)