TM 9-4120-388-14
Section Ill. TECHNICAL PRINCIPLES OF OPERATION
1-9. REFRIGERATION CYCLE.
a. Cooling cycle. Unit operation with mode selector switch set on COOL and the temperature control thermostat
set to DECREASE.
(1)
Compressor (1) starts.
(2)
To prevent compressor overload and damage during startup, equalizer solenoid valve (6) is open at start
of cooling cycle to equalize pressure on both sides of the compressor.
The compressor (1) takes cold, low pressure refrigerant gas and compresses it to a high temperature, high
(3)
pressure gas. This gas flows through the metal tubing to the condenser coil (2A and 2B) and receiver (3).
The condenser fan draws outside ambient air over and through the condenser coil (2A and 2B). The high
(4)
temperature, high pressure gas from the compressor (1) is cooled by the flow of air and is changed into
a high pressure liquid.
The dehydrator (filter/drier) (5) removes any moisture (water vapor) or dirt that may be carried by the Iiquid
(5)
refrigerant.
The sight glass (liquid indicator) (7) indicates the presence of moisture and quantity of refrigerant in the
(6)
system.
The liquid line solenoid valve (6) is controlled by the temperature control thermostat on the control panel.
(7)
This valve will shut off the flow of refrigerant to the evaporator section when the temperature in the condi-
tioned area reaches the set point.