Thermo King T-500R Maintenance Manual page 54

Solenoid and Check Valves
1. Condenser Inlet Solenoid (CIS)-Closed/ Energized
2. Condenser Check Valve-Closed
3. Receiver Tank Pressure Check Valve-Open
4. Purge Valve (PV)-Open/Energized
5. Purge Check Valve-Closed
6. Hot Gas Solenoid (HGS)-Open/Energized
6 1
5
4
3
2
Heat/Defrost Mode T-500R/T-Dairy
UT-Series
The refrigerant flow in Heat/Defrost Mode is a conventional hot gas heat cycle. The CIS is closed and the HGS is open so high
pressure refrigerant vapor leaves the compressor and flows through the DPR (which maintains a minimum discharge pressure)
to the hot has line. The refrigerant flows through the hot gas line and the drain pan heater to the evaporator. There, the refrigerant
heats the evaporator and returns to the compressor through the heat exchanger, and accumulator.
Solenoid and Check Valves
1. Condenser Inlet Solenoid (CIS)-Closed/ Energized
2. Liquid Injection Solenoid (LIS)-Closed/ De-energized but the microprocessor will open it if necessary to control compressor
temperature.
3. Condenser Check Valve-Closed
4. Purge Valve (PV)-Open/Energized
5. Hot Gas Solenoid (HGS)-Open/Energized
Unit Description 5-20