TM 9-4120-378-14
f.
The expansion valve (8) senses the temperature and pressure of the refrigerant as it leaves the evaporator coil.
By use of the feeler bulb in the bulb well (10) and "external equalizer line:' the valve constantly adjusts the flow
of liquid refrigerant to the evaporator coil (9).
As the high pressure liquid refrigerant leaves the expansion valve (8), it enters the evaporator coil (9). As the
g
liquid enters the coil, due to the size difference between the coil and the tubing, the pressure is suddenly decreased.
As the pressure decreases, the liquid refrigerant "flashes" to a gas. The evaporator blower circulates the warm
air from the conditioned space over and through the evaporator coil (9). Liquid refrigerant absorbs heat when
it changes from a liquid to a gas. As the air from the conditioned spaces comes in contact with the evaporator
coil (9), the air is cooled.
To prevent compressor damage during start-up, the solenoid valve ( 16) is normally open to equalize pressure on
h.
both sides of the compressor.
Bypass System. This unit has a bypass system which allows cooling operation at low cooling loads without
1.9.2
cycling the compressor on and off. In bypass, the refrigerant flow is from the discharge to the suction of the compressor,
bypassing the evaporator coil (9).
a. When the TEMPERATURE SELECTOR on the control panel senses that cooling conditions have reached the
set point, it closes the solenoid valve (7) to shut off refrigerant flow to the evaporator coil (9).
b. As the compressor suction pressure starts to drop, the pressure regulator ( 11) opens to allow flow of hot gas from
the compressor.
c. The quench valve (17) senses the temperature of the gas at the suction side of the compressor. To prevent exces-
sively hot gas from reaching the compressor, the quench valve (17) opens to allow liquid refrigerant to mix with
the hot gas.
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