tough time in sugar house last night- ideas?

[Stamford sugarmaker]

Went through a lot of wood last night with not much syrup to show for it. My flat pan just didn't seem to be boiling hard at all. I've got a locally-made 2X4 with no ramp. I have arranged the fire brick in the narrow passage to what I thought was a reasonable flame path to extract the most heat.

Normally there is a cone of fire from unburned gases coming out of the stack. I was told to let her rip because it produced lots of heat in the pan. Last night there was something new- above the red cone of heat was yellow flames, much wilder than usual. Then I noticed that there was about a 2 inch gap between the top two sections of the stack. Fortunately it did not pose a fire hazard so I let it go until I can fix it today.

I also noticed when cleaning up that there was a burn mark on the pan about half the size of a dollar bill directly in front of the draw off.

I am assuming that the flames were a result of the added oxygen provided by the gap. My question is, could that have anything to do with the reduced boiling in the pan? I have an external thermometer on the side of the evaporator that was registering the normal temperatures so it seemed like the pan was hot enough. Why was my production much lower than normal? A shower or 2 last night, not much humidity. Re-arrange the firebrick to slow the flame path down? Did that burn mark cause it?

thanks for any ideas offered

Peter

[PerryW]

FIrst, I'm guessing the burn mark is a separate issue, probably a result of running a little too shallow drawing off a little too aggressively (created a temporary defecit of syrup in the draw-off area). You also might have been a little over-density and had a small scorch spot. Almost every year, I develop a few of these spots, but usually the size of a silver dollar or smaller.

As far as the other issue, sounds like a lot of the combustion is happening in you stack. What is the diamater and height of your stack? I'm guessing here, but maybe you are getting too much draft? You could try burning shorter wood, and keeping the wood as close to the door as possible. Also, split is smaller and possibly damper it down some.
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[Jeff E]

Agree with Perry, the scorch is a seperate issue as he described.
I was thinking the gap in your chimney made the draft drop, so you where moving less air through the firebox, and then introducing air in the chimney where a secondary burn was happening. I think if you fix the chimney you will be back to normal.

There is always a challange in balancing the air intake and too much heat going up the chimney. I always thought that if I had 'flames' coming out the stack, I was wasting BTU's, and would cut back on the air intake. This was balanced by trying to get the whole pan to boil. When I used a flat 2x4 the fire was in the front 1/3 of the pan with the 'ramp' angled up and back to the chimney. There was no real flat area near the back of the pan, it was all transition. I used vermiculite so I could shape the ramp profile to maximize the boil.

[PerryW]

I used to run with my damper wide open but I notice the stack looked like a giant candle with a big flame coming out of the top. Now this stack is 20 feet tall and 15 inches in diameter so I figured I was wasting some serious heat. I now run with the damper open 1/4 of the way.

[CampHamp]

If you're getting a burn at the top of your stack, then I would have thought you need more air (not less) in the firebox to get full combustion there. Last year, I raised my stack and the added draft changed the way I had to boil -- needed tons more air and wood. This improved evaporation only slightly and couldn't justify the extra fuel consumption, so I lowered my stack (I didn't have a damper). With a 4-foot-long pan, I don't think you need much draft -- it will just pull your flames back away from the front too much. Good luck to you...

[Stamford sugarmaker]

Thanks for all the informative responses. Sap didn't run yesterday so I worked on other sugar house issues and didn't get time to fix the gap in the stack.

I've got about 10 feet of 7 inch stove pipe with no damper. If a damper is at least part of the answer, where in the stovepipe should I put it? My wood supply is pretty consistent so I don't think that is the issue- everything worked fine previously.

Nobody seemed to comment on the possibility of altering the flame path in the narrow "transition area" between the firebox and the stack. I just placed some firebrick in a way that I thought would elongate the flame path and transfer as much heat up to the pan as possible. Not very scientific. Maybe I should play with that, but for now I don't think that's the issue.

The only thing that's changed is the gap. I think Jeff E may be right. It's gotta be fixed anyway so we will see what happens. I'm also interested in the possibility of adding a damper. Your thoughts?