stop boil on a flat pan?

[TonyMo]

Greetings,
I am a complete rookie and this is my first year. I have been reading and learning a great deal here. THANK YOU!
I am recently retired and jumping into this both feet. I have 47 acres and with probably 1/3 of that sugar maples. Since its my first year probably 50 taps max....probably won't get bigger than that in the future...right????:)
I am building myself and oil tank evaporator, insulated and bricked. I'm having local supplier build me a 2x4 flat open pan with draw off valve.

So, I will be boiling a batch to near syrup and drawing off to finish and pack in mason jars on propane stove inside.
My question is how to not burn the bottom of my pan when I draw off?
Do I have to somehow remove the pan from the top of the evaporator and then draw off?
As I get down to a certain depth....1 inch??? +/-??? Do I just stop feeding the fire and let it cool down and hope it doesn't evaporate too much more? I realize I will have to "learn" the rate at which my evaporator burns.

EDIT: I guess I put this in the wrong section...would have been better in the evaporator/boiling sap section

[miboss]

Yeah, you'll learn the depth you need to stop firing and let things cool down. it's best to have a bucket of sap handy if things start getting a little low and there's still too much heat.

For me, I learned that when my head tank reads 3" I stop putting wood on, that usually is enough to keep things boiling enough to get everything into the pans till next boil. It took 3 or 4 boils to dial it in.

If the next boil will not be for a couple days, draw everything off into buckets and throw in refrigerator or freezer till next boil.

Good luck and have fun!