Which is the oil inlet and which is the oil return, P or T?
2 Answers
P refers to the oil inlet of the hydraulic system, while T is the oil return port. Below is a related introduction about oil return: Definition: During the operation of a multi-split system, some of the compressor's lubricating oil is discharged along with the refrigerant gas into the system's condenser, piping, and evaporator. Only if this discharged lubricating oil can be successfully brought back to the compressor can the dynamic balance of oil in the entire system be maintained. Otherwise, the compressor may be damaged due to oil shortage. The process from the discharge of lubricating oil to its return to the compressor is called oil return. Reason for oil return: For gasoline engines, oil pressure is regulated through oil return, while for diesel engines, the fuel supply pump delivers more oil than is actually used, hence the oil return.
I've seen many car enthusiasts mix this up. The P port is typically the inlet (pressure side), while the T port is the return. When helping my dad repair his old car, the transmission oil temperature was alarmingly high simply because P and T were reversed. P stands for the pressure port - the high-pressure oil inlet from the pump, whereas T is the return port where cooled oil flows back to the tank. If connected incorrectly, it can cause oil passage blockage, improper cooler operation, and eventually lead to costly transmission damage. Always consult the manual or use a pressure gauge to verify the flow direction before working - P-in/T-out is the industry standard. Never cut corners for speed - safety first. Regular maintenance also helps prevent such issues.
