I didn't know BTU but I know kJ. I know 3-500 liter of glycol is not capable of chilling down an entire batch of hot brew. I am asking, is the freezer capable of bringing down the glicol (300l in freezer, ~20l in pipes, 100l in jacket) to working temperature, so that it cools down the fermenter from 20°C to 12°C. What do you mean by "mechanical transfer". I was assuming it is a matter of insulation.