I am fighting a 92' chiller. the unit will randomly fail but always with a E4 (phase loss) The system had a compressor change about 5yrs ago and the main control board was also changed (1U3). Trane tech. support pushed for oil problems but none of the tests every showed any sign of an oil problem. I have logged the power supply to see if it was actually dropping out even for a split second, however it was normal when the chiller would trip. All the Service bullion listed was changing the unit to run at 50hz instead of 60hz as per Trane it make no sense. This also made no difference. The only thing that logs a failure is the Main control board by inputs from the CT's witch test normal.
My current working theory is the board overheats. I logged the cabinet temps and only peaked at 98. Added cooling fan and the chiller has yet to trip. Has anyone ever had this problem or more important solve it permanently? Any help or thoughts would be great.