Quote Originally Posted by cmclifton View Post
-150 is an autocascade. Single compressor (3HP scroll iirc) 4-5 different refrigerants in one system. The higher pressure gases act like non-condensibles in the air cooled condenser, after which liquid is dropped out through a cap tube to a heat exchanger that cools the vapor that didnt condense in the air cooled condenser, so on and so forth. At the end you have argon in a saturated vapor state going through the evaporator. I like working on them, most people run screaming. Mostly cause they don't want to do what the manufacturer says needs to be done to get it right...
Best description I seen for an autocascade, depending upon the age, it may also be a 3 stage cascade.