flue pan boil

[ryan marquette]

I am running a 3x10 arch with a 3x7 raised flue its boiling real hard in first three feet(probably splashes 18" above sap level) then the boil falls to a light boil. I don't have a blower. About 21' 12" stack, I think it draws well. It doesn't smoke at all inside or outside I can only see heat coming out the stack & I even have sparks coming out the stack. The wood I am using is only about 18" long & the firebox is about 32" end to end. I'm going to try to pack more wood in next boil. It does seem to boil better when I don't pack wood in tight under syrup pan. I need to start with finding my stack temps. What do you guys use for thermometers to measure stack temps. Where do you put them, where do you get them,how much are they. I was thinking about maybe using a pyrometer.

[PerryW]

I also have a 3x10 with a 3x7 raised flue sap pan and NO blowers and NO hoods.

My evap comes with 20 feet of 15" stack, so it sounds like your stack diameter is a little too small.

Of course, mine also boils much better in the front half of the pan, but I still can get it going fast enough to require defoamer.

I would try using longer wood (I use 24-30" wood in mine) and running the intake damper wide open.

Another thing it could be is your brick ramp (behind the firebox) is loaded up with ashes and it's forcing the fire up into the flues too soon .

How's your evaporation rate? I'm can consistently get 90 GPH evap rate using nice dry softwood slabs.

[danno]

I'm running a 3x10 as well with 7' flue pan. I've got a tight hood, preheater, air over and under the fire and have to put the peddle to the metal to reach 85 gph. 21' of 14" stack. Good boil and have to defoam.

I put my thermo on the side of my stack about 3' above the arch. I use the magnet kind that does not go through the stack - you can pick them up for $10 at a local wood stove store. HD and Loews carries them in the fall. My outside stack temp maxes at about 650. I know a bunch of guys are using the thermos that measure heat inside the stack. I know there are threads on here about them. They run much hotter cause there inside the stack.

What's your evap rate? Perry, do you what stack temps you're running?

[PerryW]

My evap. rate is about 90 GPH when I get it going.

Actually I take the number of hundreds of gallons and add one for my estimated boil time (from lighting the fire to end of boil).

For example:
400 gallons = 5 hours

600 gallons = 7 hours

800 gallons = 9 hours

[ryan marquette]

Thanks for the input guys. I Boiled 450 gallons yesterday. I lit the fire at 10:40 and the sap was gone and no more boil at 6:40. I figure I'm running in the mid 60 an hour when I am boiling hard. Danno, I think my evap rate isn't that bad compared to your rate with blower, hood, and preheater. What do you think? Perry, my rate isn't even comparable to yours. I have to post some pictures on here so you guys can see what I have. My syrup pan is 30" x 48" with 4 sections. So one 12" section hangs off the side of the arch acting like a giant float box. The other 3 sections boil good. I am sure I am losing some gph with this set up but it's working better than I thought it would have and I saved 600 to 1300 dollars by using the old pan I had. I think I have to adjust my front ramp a little. The front of my flue pan realy makes a mess from splashing sap out.

[Bradenfish]

Try firing one door every 3-5 minutes and make sure you fill up the firebox front to back. I split my firewood 3-4'' in diameter. Doesn't kill your boil as easily, burns hotter. Make sure you keep your grates free of ash too. 18' of 14'' stack.