Thermo King T-500R Maintenance Manual page 68

Purge Mode UT SPECTRUM Units
Purge Mode is used to move the refrigerant out of the condenser into the accumulator when the unit shifts from all zones in
Cool (or Null) to any zone in Heat. The unit goes into Purge Mode for 20 to 100 seconds before shifting to Heat. The ambient
and return air temperatures determine the duration. Lower temperatures cause the unit to stay in Purge Mode longer.
High pressure refrigerant vapor leaves the compressor and flows through the open CIS to the condenser. The PV is open so
most of the refrigerant flows from the condenser through the PV and the PCV to the accumulator.
Some of the refrigerant flows through the CCV, receiver tank, and drier, into the liquid lines.
The LLS1 is open so some of the refrigerant flows through the Zone 1 heat exchanger, expansion valve, evaporator, SLS1,
suction line, and SLCV1, to the accumulator.
The LLS2 is also open so some of the refrigerant flows through the Zone 2 heat exchanger, expansion valve, evaporator, SLS2,
suction line, and SLCV2, to the accumulator.
From the accumulator the refrigerant returns to the compressor through the ETV.
Zone 1 Evaporator
1F. Zone 1 Liquid Line Solenoid (LLS1)-Open/ Energized
2F. Zone 1 Liquid Return Check Valve (LRCV1)-Closed
3F. Zone 1 Suction Line Solenoid (SLS1)-Open/ De-energized
4F. Zone 1 Suction Line Check Valve (SLCV1)-Open
5F. Zone 1 Hot Gas Solenoid (HGS1)-Closed/ De-energized
Zone 2 Evaporator
1R. Zone 2 Liquid Line Solenoid (LLS2)-Open/ Energized
2R. Zone 2 Liquid Return Check Valve (LRCV2)-Closed
3R. Zone 2 Suction Line Solenoid (SLS2)-Open/ De-energized
4R. Zone 2 Suction Line Check Valve (SLCV2)-Open
5R. Zone 2 Hot Gas Solenoid (HGS2)-Closed/ De-energized
Condensing Unit
6. Condenser Inlet Solenoid (CIS)-Open/ De-energized
7. Liquid Injection Solenoid (LIS)-Closed/De-energized but the microprocessor will open it if necessary to control compressor
temperature.
8. Condenser Check Valve (CCV)-Open
9. Receiver Tank Pressure Solenoid (RTPS)-Closed/ De-energized
10. Purge Valve (PV)-Open/Energized
11. Purge Check Valve (PCV)-Open
12. Hot Gas Bypass Solenoid (HGBS)-Closed/ De-energized but the microprocessor will open it if necessary to control suction
pressure.
Solenoid Delays
Purge Mode delays the normal output of the CIS, HGS, and RTPS when the unit shifts from all zones in Cool (or Null) to any
zone in Heat.
Unit Description 5-34