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northwoods_forestry
03-18-2016, 08:05 AM
Hoping I might get some feedback on this.

We run a wood-fired 3x10 Leader MaxFlue with a preheater on an airtight arch with air-under-fire. When I'm alone in the sugar house I fire every 5 minutes, keep the wood latticed over the grates adding 4-6 chunks, run a stack temp between 900 - 1000, and process between 100 to 125 gallons of sap/hour. On big sap days I have a helper who runs the evaporator while I gather sap, filter, and pack syrup. He fills the entire firebox every 5 minutes with 6-10 chunks, pushes the stack temps to 1200-1400, and gets an evaporation rate in excess of 150 gallons/hour.

A couple of other observations, at stack temps under 1000 there is little or no discernible smoke coming from the stack, but at 1200 or above there is a black column and lots of embers shooting from the stack. The stainless stack has gone a bit off-colored this year after a couple nights when the temps were pushed to the 1400 mark.

I really appreciate the help and the high evaporation rate is great for getting to bed at a reasonable hour, but I'm wondering if we might be pushing the system too hard or losing heat conversion efficiency (wood burned/evaporation rate)?

nymapleguy607
03-18-2016, 10:13 AM
Stack temp vs evaporation vs efficientcy go together somewhat like a bell curve. Most effiecent burn wont mean the highest evaporation rate and best evaporation rate wont be as efficient. Every evaporator seems to have a balancing point, on my rig it seems to be between 1000-1100 degrees. You really need to determine what is important to you, saving wood and boiling slower or boiling faster and using more wood.