We're experimenting with this idea this year. We've only boiled twice, so there are still some bugs to work out.

From the holding tank -> ball valve -> 15' of 3/8" copper wrapped -> needle valve -> batch pan

It needs to be an open system as we've experienced some blow-back into the holding tank.

We added the needle valve with the intent of filling the tubing and trickling the sap into the pan. We still haven't found the sweet spot where we can maintain the level in the pan and not have it boiling in the line.

There are only a few variables to play with - volume in system and flow rate. We're playing with the flow rate.

Sap comes out warmer than it was going in, and it's not killing the boil. We're doing something right.