Carrier TRANSICOLD VECTOR 8100 Operation & Service Manual Download

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2–6

2.3.6

Economizer Transducer and Sensor

a. Economizer Outlet Pressure Transducer (ECOP)

The ECOP is located in the vapor injection line leaving the economizer. It provides the control system with
economizer outlet pressure information to be displayed, recorded in DataLink data, and used to determine the
required position of the economizer expansion valve.

b. Economizer Outlet Temperature Sensor (ECOT)

The ECOT is a thermistor type sensor located on the suction line leaving the economizer. It provides the control
system with economizer outlet temperature information to be displayed, recorded in the DataLink data recorder
and used to determine the required position of the economizer expansion valve.

2.3.7

Ambient Air Temperature Sensor (AAT)

The AAT is a thermistor type sensor that provides the control system with the temperature of the air entering the
condenser. This temperature information is displayed, recorded in the DataLink data recorder and used to control
the refrigeration system. The sensor is located behind the front grill.

2.3.8

Compressor Suction Modulation Valve (CSMV)

The CSMV opens and closes as required for capacity control of the refrigeration system cooling cycle. It is located
in the suction line just above the compressor.

2.3.9

Filter-Drier

The filter-drier is a cylindrical shell containing a drying agent and filter screen. It is installed in the liquid line and
functions to keep the system clean and remove moisture from the refrigerant.

2.3.10

Receiver

Liquid refrigerant from the condenser flows into the receiver. The receiver serves as a liquid reservoir when there
are surges due to load changes in the system; as a storage space when pumping down the system and as a liquid
seal against the entrance of refrigerant gas into the liquid line. The receiver is provided with two bulls-eye sight
glasses, for the observation of liquid level & moisture content, and a fusible plug.

2.4

EVAPORATOR SECTION

The evaporator (See

Figure 2.2

) fits into a rectangular opening in the upper portion of the front wall of the

refrigerated compartment. When the unit is installed, the evaporator section is located inside the compartment, and
the condensing section is outside.

The evaporator assembly consists of an evaporator coil, evaporator fan, evaporator expansion valve, evaporator
outlet pressure transducer, evaporator outlet temperature sensor, defrost termination temperature sensor, supply
temperature sensor and return air temperature sensor.

Heating and defrost is accomplished by electric heaters mounted on the coil.

2.4.1

Evaporator Coil

The evaporator is a tube in fin type. The operation of the compressor maintains a reduced pressure within the coil.
At this reduced pressure, the liquid refrigerant evaporates at a temperature sufficiently low enough to absorb heat
from the air. Air movement over the coil is provided by the evaporator fan and motor (EVM) assembly.

The electric heaters (HTR1 & HTR2) are mounted on the inlet side of the coil and in the drain pan.

Automatic evaporator coil defrosting is initiated by either a defrost air switch (DAS - which senses the pressure
drop across the coil) or by the control system defrost timer. During defrost the refrigeration system is shut down
and the evaporator fan and heaters operated as required by the defrost mode.

2.4.2

Evaporator Expansion Valve (EVXV)

The EVXV is an automatic device which controls the flow of liquid to the evaporator according to changes in
superheat of the refrigerant leaving the evaporator. The expansion valve maintains a relatively constant degree of
superheat in the gas leaving the evaporator regardless of suction pressure. The valve has a dual function -
automatic expansion control and prevention of liquid return to the compressor.