I am being told several different facts by those wishing to sell me compressors for my new cascade co2/ nh3 system. screw compressors slip and are not efficient for co2 and that screws are more efficient than recipts period. I here most if not all co2 systems in the UK use recips. Nestles built a cascade system in the US, it is considered to be a flop because while it works fine it is very inefficient. I am going to CA this weekend to visit an operating warehouse there and attend their open house. Both companies swear by their systems. Who has information to support one or the other or both? I ask the recip supporter why do you install recipts? he said the molecular weight of co2 is 44, nh3 is 17, co2 is more than 10 times heavier, I thought 17X10 =170 but maybe it isn't the same as regular math more like the rector scale earthquakes are rated on, each number is way more severe not just a little stronger. The other company's refrigeration guy is from Denmark, he seemed fine with a Mycom screw. He wants to fly us to Japan to visit the manufacturing plant and the new Wal-mart facility in operation. What say you all?