2020 update on my copper coil preheater shown in the top of this thread - since that picture, I doubled the length of the copper coil, and continue to wrap it with aluminum flashing to minimize heat loss around the coil, did some experimenting with and without the blower running for air under fire....incoming sap temperature was ambient, so in the 40's; without running the AUF, sap exit temperature around 160 to 170F, but with the AUF and the rig really rocking the sap temperature increased to 194F, so I'm raising sap temperature by 150F just by using heat going up the stack, pretty satisfied with the results.
2010 - 12 taps, turkey fryer, 4 quarts
2011 - 24 taps, homemade arch from old water tank, 16"x24" flat pan, 16+ quarts
2012 - 9 taps, 3 pints, what a season
2013 - 60 taps, homemade oil tank arch with 2'x4' flat pan, 16"x24" finishing pan on electric range, 55 quarts
2014 - 80 taps, homemade oil tank arch with 2'x4' flat pan, 16"x24" finishing pan on electric range, 40 quarts
2015 - 100 taps, 15 gallons
2016 - 115 taps, 13.5 gallons
2017 - 120 taps, 13 gallons
2018 - 130 taps, 11 gallons