I was on a straight cooling system couple of years ago. The HO reported the system would run until the thermostat satisfied, then the condenser electrical service breaker would trip; which of course, didn’t make sense. I suspected the breaker was tripping along about the time the stat satisfied.
All I could do was start the system and observe the operation. The system ran normal for about 10 minutes, then for no apparent reason the head pressure began to rise rather quickly and eventually hit the high limit switch value and shut down.
After observing the subcooling value, it was obvious the problem was overcharge. The system also had a small refrigerant leak and the HO had been calling someone else to charge it up, but they apparently weren’t watching the subcooling. Add to that, the outdoor unit is micro-channel while the indoor coil is tube and fin and TXV metered. Micro-channel coils on both ends are sensitive to charge but when mixed with tube and fin, they can be very sensitive. I ended up recovering enough refrigerant to reduce the subcooling down to 4˚- 5˚.
