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TM5-4120-387-14
Section Ill TECHNICAL PRINCIPLES OF OPERATION
1-12. REFRIGERATION CYCLE
Cooling cycle.
Unit operation with mode selector switch set on COOL and
the temperature control thermostat set to DECREASE.
Compressor (1) starts.
l 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.
l The compressor (1) takes cold, low pressure refrigerant gas and
compresses it to a high temperature, high pressure gas.
This gas flows
through the metal tubing to the condenser coil (2) and receiver (3).
The condenser fan draws outside ambient air over and through the
condenser coil (2).
The high 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 liquid refrigerant.
The sight glass (liquid indicator) (7) indicates the presence of
moisture and quantity of refrigerant in the system.
l The liquid line solenoid valve (6) is controlled by the temperature
control thermostat on the control panel.
This valve will shut off the flow of
refrigerant to the evaporator section when the temperature in the conditioned
area reaches the set point.
The expansion valve (8) controls the amount of pressure of liquid
refrigerant to the distributor (9) and evaporator coil (10). The expansion
valve (8) senses the temperature and pressure of the refrigerant as it leaves
the evaporator coil.
By use of a sensing bulb and “external equalizer line”
the valve constantly adjusts the flow of liquid refrigerant to the evaporator
coil (10).
As the liquid refrigerant leaves the expansion valve (8) it passes
thru a distributor and enters the evaporator coil (10). As the liquid enters
the coil at a reduced pressure, the reduction in pressure and the warmer air
being forced across the tubes of the coil cause the refrigerant to boil and
change to a gas (vapor).
The evaporator fan circulates the warm air from the
conditioned space over and through the evaporator coil.
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 (10), the air is cooled.
The refrigerant gas is then drawn back to the compressor (1) and the
cycle is repeated.
1-7
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