You are right Ken - the liquid needs to be pressurised to about 45 bar before it is vaporised to create the "hot gas". For CO2 45 bar (about 675psig) is about 10C (50F) saturated, so the defrost works a treat. This seems to be much more efficient than a typical ammonia hot gas defrost, but I don't know why. Perhaps there is a lot less gas passing through the evaporator without condensing, so less dummy load on the compressor when CO2 is used?


Cheers
Andy P