Massive smoke in Sugar shack

[Troy D]

Long story short, Dad built a block evaporator, fire brick, for under a 4 by 2 flat pan, 8 inch flue 12 feet long with some type of cap on top. The whole bottom of the pan is open, no ramp just a big square box. It is possible to throw 7 foot pieces of wood into the fire box. There is NO PROBLEM getting a boil, Throwing 5-6 foot pieces of 2/4s, 1 inch square, or just big chunks of wood the whole pan is ripping. Problem is huge amounts of smoke, and flames, plow back into the shack. I would have thought with that big a flue we would be pulling stuff off the floor into the firebox. Would the cap on top be restricting flow out the stack?, the 8 inch flue not big enough, or a combination of both plus we might need more height. This is a new set up this year and he put a ton of work into it. Thanks for any help.

[BAP]

Take the cap off, it is restricting the draft of the stack.

[Troy D]

Thanks Now to convince my Dad. LOL

[Joe Hillmann]

Is your wood dry? Wet wood causes lots of smoke. Do you have a front on your stove? Leaning a piece of sheet metal up against where the door should go helps if it is open to the front. Adding a blower can help. How tall is your stack? Is there anything like trees or a roof that is as tall as your stack within 10-20 feet? That can cause problems with draft. How big of chunks of wood are you burning? If the wood is wet it helps to chop the wood in to sizes not much larger than kindling.

[Troy D]

It did not matter what type of wood. Stack is 12 feet. We tried a bunch of stuff systematically. It almost seemed as if the flue was running backwards at times. There was mirage coming out the top of the stack outside, not much smoke. It had to be drawing some. I was seriously worried the shack was going to go up in flames. There were Flames Jumping out the door back into the shack, Dad's Quote "I have been in enough house fires to tell you this ain't good." LOL We ended up putting a big chuck of steel against the door and just held it in place till the whole crap died down.
We are going to try pulling the cap as suggested and he has an extra 3 feet of stack if needed. Thanks for the help and I will report next week how it went.

[Sugarmaker]

Sounds like you had a good fire. Yes take the lid off and add the extra length of pip. You have a very large fire box area.
Good luck and be safe too! Have a hose near by!
Regards,
Chris

[Troy D]

Never did figure it out, put on more stack and pulled off the cap. smoke still blew back into the shack. There were times flames were coming out the stack at 16+ feet. But when we loaded the box we got massive smoke. I guess we need to rethink our system. Thanks for the help.

[maple flats]

What is the back like where the stack attaches? It must be full or near full width, then it can taper to a round stack. How much wood are you adding at once, in a normal evaporator we generally add only 1 half at a time, then by the clock add to the other half so many minutes later and keep working back and forth. Have dry wood and split it small, if your width is 2' the wood should be split 2-2.5" max, if 3' use 3-3.5" wood. Common fueling times are 7-8 or 9 minutes. Add the wood as fast as safely possible, then push the plate or door over the opening, just have a 4" x 12" air inlet, up to maybe 6x14" max. When burning, use no cover, but when not burning a cover is good. Make sure you have enough air to not choke the air inlet any.

[Troy D]

Thanks again for the input, Dad is Done for the year. We are going to have to try some new ideas for next year. thanks again.

[youp50]

Simply put the comzinta is exceeding the gozatta.

This leaves you with two options; decrease the comzinta. Build a smaller fire. Or increase the gozatta.

It sounds like you are very pleased with the boil rate, so decreasing the comzinta is a poor option. Therefore you need to increase the gozatta. Use 10 inch flue pipe.

[motowbrowne]

Simply put the comzinta is exceeding the gozatta.

This leaves you with two options; decrease the comzinta. Build a smaller fire. Or increase the gozatta.

It sounds like you are very pleased with the boil rate, so decreasing the comzinta is a poor option. Therefore you need to increase the gozatta. Use 10 inch flue pipe.

This is a very eloquent description of what needs to be done.

[MaxJ]

Simply put the comzinta is exceeding the gozatta.

This leaves you with two options; decrease the comzinta. Build a smaller fire. Or increase the gozatta.

It sounds like you are very pleased with the boil rate, so decreasing the comzinta is a poor option. Therefore you need to increase the gozatta. Use 10 inch flue pipe.

Have you been standing too close to the smoke? What the heck are you talking about?

[youp50]

comzinta is the stuff coming into your arch fire, combustion air, and the products of combustion, fire, volatile gasses etc. Comes into or comzinta.

Gozatta is the stuff going out of your flue. Goes out of.

If the comzinta exceeds the gozatta it over flows, this formula is also applicable to other systems, including bathtubs and kitchen sinks.

They are or were US Navy Nuclear Power terms in the 70's, which easily explains why an Ontarian would have trouble understanding the code, I am sorry for that and hope this explanation helps.

[mellondome]

If you have flame coming out the top if the stack, you are starving the fire of oxygen. (Also the reason it flames out the door.. this is where the oxygen is). Think about the size of what you are doing. On my 2x6, the firebox is about 18x18x24 and my stack is 8in diameter. What you are describing is massively larger. Your stack needs to be sized to accommodate the volume of air need for your fire. How is air getting into the firebox? Fan, door, draft opening?

[mellondome]

From your initial description, this is a 4ft x 14ft configuration? And you are only using an 8in stack? You should be looking at 15+in stack diameter.

[Troy D]

The fire box is 2 by 4 feet like 3 feet high. We did try different things like only loading a few sticks at a time, but it did not seem to matter. In the end we piled wood into the fire box and let her rip. We just stayed out of the shack till the smoke died down. LOL Like I mentioned we are going to have to re think our process. Thanks again.

[Daveg]

2X3X4? Are you using grates? With grates, that size firebox will use less than an "armload" per firing and it will help elevate the heat energy closer to the pans. If it is 3 feet tall from the front to the back, you're perfectly set up to build up your arch into a ramp with grates, AND an ash bin, to boot! Get some firebricks here or on craigslist!