Carrier TRANSICOLD VECTOR 8100, Руководство по эксплуатации и обслуживанию, Страница: 35 / 294

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2.3 CONDENSING SECTION
The condensing section (see Figure 2.1 ) consists of the compressor, condenser fans, condenser, economizer,
refrigerant controls defrost air switch, piping, wiring, and associated components.
2.3.1 Compressor
The unit is fitted with a scroll compressor equipped with suction and discharge service valves and an economizer
connection. The compressor draws refrigerant gas from the evaporator and delivers it to the condenser at an
increased temperature and pressure. The pressure is such that refrigerant heat can be absorbed by the
surrounding air at ambient temperatures.
2.3.2 Compressor Switches, Transducers and Sensors
a. Compressor Discharge Pressure Transducer (CDP)
The CDP provides a signal to the control system equivalent to pressure leaving the compressor. The reading is
displayed, recorded in the DataLink data recorder and used to control the refrigeration system. It is located in the
discharge line leaving the compressor.
b. Compressor Suction Pressure Transducer (CSP)
The CSP provides a signal to the control system equivalent to pressure entering the compressor. The reading is
displayed, recorded in the DataLink data recorder and used to control the refrigeration system. It is located in the
suction service valve.
c. High Pressure Switch (HPS)
The HPS is normally closed and opens on pressure rise to signal the control system to shutdown the refrigeration
system if the discharge pressure rises above the switch setting. It is located in the discharge service valve.
d. Compressor Discharge Temperature Sensor (CDT)
The CDT is a thermistor type sensor that provides a signal to the control system equivalent to the temperature of
the gas leaving the compressor. The reading is displayed, recorded in the DataLink data recorder and used to
control the refrigeration system. It is located on the compressor head.
e. Compressor Suction Temperature Sensor (CST)
The CST is a thermistor type sensor that provides a signal to the control system equivalent to the temperature of
the gas entering the compressor suction service valve. The reading is displayed, recorded in the DataLink data
recorder and used to control the refrigeration system. It is located on the line entering the service valve.
2.3.3 Liquid Injection Solenoid Valve (LIV)
The LIV is opened during periods of high compressor discharge temperature to inject refrigerant into the
economizer connection to cool the compressor. It is located at the front of the economizer.
2.3.4 Condenser Coil
The condenser coil is a microchannel type and acts as a heat exchanger in which the compressed refrigerant gas
is lowered in temperature and condensed into a liquid. A portion of the condenser coil is occupied by the subcooler,
which removes heat from the refrigerant liquid leaving the receiver. Air movement over the condenser, subcooler &
radiator is provided by the condenser fans.
2.3.5 Economizer Circuit
The economizer circuit consists of a compact brazed plate heat exchanger ( Figure 2.1 ) and the economizer
expansion valve (item 17 = ECXV). Both are located above the compressor.
In the economized mode, the frozen and pull down capacity of the unit is increased by subcooling the liquid
refrigerant entering the evaporator expansion valve. Overall efficiency is increased because the gas leaving the
economizer enters the compressor at a higher pressure, therefore requiring less energy to compress it to the
required condensing conditions.
To place the unit in the economized mode, the control system energizes (opens) the ECXV. The ECXV controls the
flow of liquid from the main liquid line through the economizer according to changes in superheat of the refrigerant
leaving the economizer.