Compressor HVAC: Description and Operation

Fig.1 TRS90 Compressor:

The TRS9O is a fixed displacement type compressor. The compressor uses an integral thermal limiter switch to protect it from overheating. A high pressure relief valve located on the rear of the compressor housing is designed to protect the system from excessive pressure. The system uses polyalkylene glycol synthetic wax-free refrigerant oil SP-15 PAG.

The compressor is driven by the engine through an electric clutch, drive pulley and belt. The compressor is lubricated by refrigerant oil that is circulated throughout the system with the refrigerant. The compressor draws in low-pressure refrigerant vapor from the evaporator through its suction port. It then compresses the refrigerant into a high-pressure, high-temperature refrigerant vapor, which is then pumped to the condenser through the compressor discharge port.

A high pressure relief valve is located on the rear surface of the compressor housing. The high pressure relief valve vents the system when a discharge pressure of 3445 - 4135 kPa (500 - 600 psi) or above is reached. The valve closes with a minimum discharge pressure of 2756 kPa (400 psi) is reached. This prevents damage to the compressor and other system components. The compressor and relief valve cannot be repaired and must be replaced if damaged.