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2.16 REFRIGERANT CIRCUIT DURING COOLING (See Figure 2-11 thru Figure 2-14)
When cooling, the unit operates as a vapor compression
refrigeration system. The main components of the
system are: the (1) reciprocating compressor, (2)
air-cooled condenser, (3) electronic expansion valve,
and (4) direct expansion evaporator.
The compressor raises the pressure and the
temperature of the refrigerant and forces it into the
condenser tubes. The condenser fan circulates
surrounding air over the outside of the condenser tubes.
The tubes have fins designed to improve the transfer of
heat from the refrigerant gas to the air. This removal of
heat causes the refrigerant to liquify. Liquid refrigerant
leaves the condenser and flows to the receiver.
The receiver stores the additional charge necessary for
low ambient operation. The receiver is equipped with a
relief valve (See Section 2.12)
The refrigerant leaves the receiver and flows through
the manual shut off valve (King valve) to the subcooler.
The subcooler occupies a portion of the main
condensing coil surface and gives off further heat to the
passing air.
The refrigerant then flows through a filter-drier where an
absorbent keeps the refrigerant clean and dry.
The refrigerant flows to the “Liquid/suction” heat
exchanger.
Here the liquid is further reduced in
temperature by giving off some of its heat to the suction
gas.
The liquid then flows to an externally equalized
electronic expansion valve (EVXV) which reduces the
pressure of the liquid and meters the flow of liquid
refrigerant to the evaporator to obtain maximum use of
the evaporator heat transfer surface.
The refrigerant pressure drop caused by the expansion
valve is accompanied by a drop in temperature so the
low pressure, low temperature fluid that flows into the
evaporator tubes is colder than the air that is circulated
over the evaporator tubes by the evaporator fan. The
evaporator tubes have aluminum fins to increase heat
transfer; therefore heat is removed from the air
circulated over the evaporator. This cold air is circulated
throughout the box to maintain the cargo at the desired
temperature.
The transfer of heat from the air to the low temperature
liquid refrigerant causes the liquid to vaporize.
This low temperature, low pressure vapor passes
through the evaporator outlet temperature and pressure
sensors (EVOT and EVOP) which aid in calculation of
superheat. The vapor then passes through the “suction
line/liquid line” heat exchanger where it absorbs more
heat from the high pressure/high temperature liquid and
then returns to the compressor through the compressor
suction modulation valve (CSMV). The CSMV controls
the compressor suction pressure thereby matching the
compressor capacity to the load.
The remote evaporators are equipped with liquid
solenoid valves which open or close depending on the
thermostat, and are also equipped with externally
equalized thermostatic expansion valves (TXV).
2.17 REFRIGERANT CIRCUIT -- HEATING AND DEFROSTING (See Figure 2-12 thru Figure 2-15)
Compressor is turned off for all heating and defrost
cycles. Heating and defrost are accomplished using
electric resistance heaters. See Sections 3.10 and 4 for
more information on heating and defrost.
Summary of Contents for VECTOR 1800 MT
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Page 2: ...OPERATION SERVICE MANUAL for VECTOR 1800 MT Trailer Multi Temp Refrigeration Units ...
Page 19: ...1 5 62 11039 1 3 SAFETY DECALS ...
Page 20: ...1 6 62 11039 62 03958 00 Heat Warning 62 03957 01 High Voltage 62 60280 00 Standby Safety ...
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Page 310: ...10 8 62 11039 BASED ON ENGINEERING SCHEMATIC 62 60926 REV G NEXT SHT ...
Page 311: ...10 9 62 11039 FROM PREVIOUS SHT ...