Yes, my bad. HE = Heat Exchanger. Burning WVO, IMO, requires pre-heating the grease. This permits at least one full quart to be elevated to 175F-ish at any given time. There is some lost heat from the coolant. That sized HE can handle up to 300K BTUs, so it is "over-sized" for the job since a gallon of #2 or WVO does not even have 200K BTUs in it, but this was the only size to meet my performance objectives.