I totally agree w/CKTOY my multiple vac down procedure is a bit of overkill I was just living in the "I have nothing better to do than work on pulling down my refrig system" world. <img src="/forums/images/graemlins/notooth.gif" alt="" /> He is an actual HVAC technican were I am an office puke in the HVAC world. Nitrogen is used because it does not harm the enviroment, it is totally moisture free and can be dispensed under high pressure to blast the crap out of your system (like fiber in your diet), in the bad old days we just used refrigerant to purge. Many manufactures ship equipment with a nitrogen charge and technicians service refrigerant in during start-up.