Not sure about new flue pan

[TIMIKE]

Put in 20hr on our new pan and now we are just confused. We have 2x8 (2x2front pan and 2x6 hybrid drop flue). We went through just over 800gal of sap(2.25%)in that time with only 4 draw offs getting just under 9gal of syrup. Should we be doing better then that? We would get more syrup on our flat pan in a day. With our flat pan our smoke stake would be hot as can be and now with the new pan you can put your hand on it. How close should brick be to the bottom of flues? How big of a smoke stack should we have? Sorry for all the questions we are just confused why we are getting the same amount of syrup as the flat pan in the same amount of time.

[mapleack]

Brick should be within a 1/2 inch or less of the flues, a 2x8 should probably have 8" or 10" stack. How often are you firing it, how dry is the wood, how much? More details will help diagnose what's going on. I will say though that 40 gph evaporation rate is average for some older 2x8s, though some newer ones will boil twice that.

[markct]

You need more heat, more fire and more draft etc. The stack on my 2 x 8 is in the 800 to 1200 deg range

[TIMIKE]

We use mostly pallets (a lot of dry pine)mixed with a little wrist size hickory. We put wood in about every 10-15min. We def a hot fire up front as you can barley stay standing in front and the front of the flue pan goes crazy but the back doesn't do much and we defiantly aren't getting fire to the back like we did with the flat pan. I take it with the flues in there is changing how the arch is working big time. We could try changing from the 7in stack that we have been using to a 10in stack and see if that helps. Just has us scratching our heads that sap is going in and def boiling a lot more sap in a hr them our flat pan but can barley get a draw were we would get a draw every 30-45min in the past yrs with the flat pan. Growing pains I guess.

Thanks for all the help and info.

[TIMIKE]

Also our pipe is 10ft. Would going to 16ft help.

[SPILEDRIVER]

you want at least twice your evap length in stack so if you have a 8 footer you want 16 feet on your stack min. you allso got to remember youve got alot of sap still in that flue pan that will stay in there until your very last boil when you drain it. i burn a 50/50 mix of seasoned hickory and pine,it makes my pans scream...you may want to up the amount of hardwood/hickory your burning as well.

[dcast99]

Mine also has a 10" stack. Arch is less than 1" from the bottom of the drop flues. Also firing every 5 minutes with ash/oak in a cross stack pattern to get plenty of draft thru the fire. Make sure you brush the bottom side of the drop flues at every start up to get rid of ash and carbon build up. I'm boiling 45 - 50 gal per hour. The drop flues hold alot of sap. It takes 30 gal just to fill them plus more to get the 1.5" level above them. On clean up I get about 4 gal of syrup just from what's left in the evap

[Big_Eddy]

Just has us scratching our heads that sap is going in and def boiling a lot more sap in a hr them our flat pan but can barley get a draw were we would get a draw every 30-45min in the past yrs with the flat pan. .

TIMIKE
The way I read it, you are still sweetening the pans. That first half day to full day, you are concentrating the sap in the pans and building your gradient. Nothing much will come off until you have a gradient in place. With a new 2x6 drop / raised flue pan, you're looking at a LOT of sap in to sweeten the flue pan. Much more than your flat pan.

If the sap is going in and boiling off, then the syrup will start coming out. And once it does, you will be drawing off 1 - 1 1/4 gal/hr if your 800gal/20hr boil rate continues.

7" seems a little small for a 2x8 - I would think 10" would give you a better draft.

[michiganphil]

If your flue pan isn't boiling hard all over and you can put your hand on the stack, you're not getting the heat to the back of the arch. 2x the pan length is standard starting point for stack height.
According to what you said though, (800 gal in 20 hrs) 40 gph is a respectable output for a 2x8. If this was your 1st boil, I think you have just sweetened the pan and you should see more frequent draws from here on out.