Thermo King T-500R Maintenance Manual page 70

Zone 1 Cool and Zone 2 Heat UT SPECTRUM Units
The CIS is closed so high pressure refrigerant vapor leaves the compressor and flows through the DPR (which maintains a
minimum discharge pressure) to the hot gas lines.
The HGS2 is open so most of the refrigerant flows through it into the Zone 2 evaporator. There, the refrigerant heats the Zone
2 evaporator and condenses into high pressure liquid. Because the SLS2 is closed, the liquid refrigerant flows through the
LRCV2 and the liquid lines to the LLS1.
The LLS1 is open so the refrigerant flows through the Zone 1 heat exchanger and expansion valve into the Zone 1 evaporator.
There, liquid refrigerant absorbs heat as it evaporates into low pressure vapor. The refrigerant returns to the compressor
through the heat exchanger, SLS1, suction line, SLCV1, accumulator, and ETV.
Some of the refrigerant flows through the open RTPS and forces any liquid refrigerant out of receiver tank through the drier
and into the liquid lines, where it joins the liquid refrigerant going to the Zone 1 evaporator.
In the condensing unit, the CIS will open momentarily if necessary to control high discharge pressure. The PV is open
continuously during heat to drain the condenser coil.
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)-Open
3R. Zone 2 Suction Line Solenoid (SLS2)-Closed/ Energized
4R. Zone 2 Suction Line Check Valve (SLCV2)-Closed
5R. Zone 2 Hot Gas Solenoid (HGS2)-Open/ Energized
Condensing Unit
6. Condenser Inlet Solenoid (CIS)-Closed/ Energized but the microprocessor will open it if necessary to control high discharge
pressure.
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)-Closed
9. Receiver Tank Pressure Solenoid (RTPS)-Open/Energized
10. Purge Valve (PV)-Open/Energized
11. Purge Check Valve (PCV)-Closed
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 or Defrost.
CIS Delay – When there is a requirement for the CIS valve to close (energize) and a HGS to open (energize), the CIS will
delay closing (energizing) for 5 seconds.
SLS Delay – When there is a requirement for an SLS valve to close (energize), the SLS will delay closing (energizing) for 120
seconds.
Unit Description 5-36