Thermo King T-500R Maintenance Manual page 46

Sensors, Switches, and Transducers
High Pressure Cutout Switch (HPCO)
This normally closed switch monitors the discharge pressure at the compressor. It opens on high discharge pressure to shut the
unit down to prevent damage.
Low Pressure Cutout Switch (LPCO) (T-500R/T-Dairy)
This normally closed switch monitors the suction pressure at the compressor. It opens on low suction pressure to shut the unit
down to prevent damage.
Discharge Pressure Transducer
This transducer supplies the discharge pressure at the compressor to the microprocessor. This information is used by the
microprocessor and software to determine the unit operating conditions. The discharge pressure transducer is used on units
equipped with an ETV. It is not used on units equipped with an SPR.
Suction Pressure Transducer
This transducer supplies the suction pressure at the compressor to the microprocessor. This information is used by the
microprocessor and software to determine the unit operating conditions and control the ETV. The suction pressure transducer is
used on units equipped with an ETV. It is not used on units equipped with an SPR.
Compressor Temperature Sensor (UT-Series)
This sensor supplies the compressor temperature to the microprocessor. This information is used by the microprocessor and
software to determine the unit operating conditions and control the LIS.
Discharge Pressure Transducer (UT-Series)
This transducer supplies the discharge pressure at the compressor to the microprocessor. This information is used by the
microprocessor and software to determine the unit operating conditions.
Unit Description 5-12