In my early years I worried and sometimes lit a small fire. Then after reading all those who don't do anything special, I started just leaving it. I do close the head tank valve (butterfly valve) and drain the feed line. then it just sets. lots of slush will form on top but nothing will freeze solid. I have gotten ice on the cold sap box, but I remove the float and no damage is done.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.