I am involved in commissioning plant w/ (3) new McQuay WMC Chillers. We have (2) 290's and (1) 150. One of the 290's is operating outside of what the McQuay IOM's indicate for normal Superheat and Discharge Superheat. The McQuay SU tech adjusted the EXV Gain and Slope during start-up because the EXV was opening/ closing w/o ever leveling out. It is now operating with -10 to -20 degree suction superheat and 5 to -7 degree discharge superheat. How is the EXV controled? The McQuay SU tech was not able to tell me (or he just didn't want to try and explain). I believe the Turbocor compressor cooling line is vented just prior to the suction temperature sensor. How is the refrigerant metered through the compressor? Any input is appreciated. I have not had much experience with centrifical's or Turbocor's.