I have a mcquay wshp around 4 ton I believe. The unit was tripping on freezestat. The head pressure was around 175 suction was around 45-50. I had 5 degrees. subcooling and no superheat. The supply air was 43 degrees return air was 73. I thought I had an airflow issue. blower rotation ok filter/coil clean. This has a weird ductwork run so I cut a hole is supply and return to eliminate that. The suction line freezes back to compressor and coil would eventually freeze. I took txv bulb off and tried to warm and make cold but suction didnt change. I beleive I eliminated airflow. I am thinking txv any thoughts. I did try adding some r22 but superheat is already low???(unless I dont have a full column of liquid}