I looked at a 10 ton (2-5 ton comps.tandem) YORK commercial split system today. The sight glass showed significant vapor circulating through the liquid line. I added refrigerant until the sight was full. It took a significant amount. 20lbs. The system still did not seem to operate at full cooling capacity. After the system had stabilized I took note of the pressures. The head was running around 250 while the suction was running around 110. It was approximately 90 degrees outside ambient and 75 degrees return air (indoor temperature greatly due to 20 ton system functioning properly in attached adjacent conditioned space). My only logical conclusion is that the TXV is not metering properly and allowing too much refrigerant to flow into the evap. This to me explains why so much vapor was present in sight glass on such a new system (excluding the possibility of a leak) thus greatly decreasing cooling capacity and showing disproportional pressure readings on guages. I have not looked at the TXV to examine because of it being located in a very difficult to access AHU hanging from a 20 foot high ceiling. I'm hoping to have some additional input from this MB so as to have a solid plan of action when I do make the effort necessary to access the TXV. Have any of you had this experience and/or have any ideas about what these symptoms indicate? Your input is greatly appreciated.