Section III. PRINCIPLES OF OPERATION
1-12. REFRIGERATION CYCLE. (Refer
to Figure 1-3.) When the control panel assembly mode selector switch
COOL and the temperature control thermostat set to COOL, the cooling cycle of the air conditioner is activated and the air
conditioner refrigeration cycle functions in the following manner.
a. Compressor (2) starts and takes low temperature, 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 (4A) and receiver (5).
b. The condenser fans draw outside ambient air over and through the condenser coil (4A). The high temperature,
high pressure gas from the compressor (2) is cooled by the flow of air and is condensed into a high pressure liquid.
c. The cooler, high pressure liquid refrigerant flows through the refrigerant desiccant dehydrator (filter/dryer) (8) and
removes any moisture (water vapor) or dirt that may be carried by the liquid refrigerant and to the liquid indicator (sight
glass) (7) which indicates the presence of moisture and quantity of refrigerant in the system.
d. The equalizer solenoid valve (13) is controlled by the temperature control thermostat on the control panel
assembly. This valve closes to separate the high and low sides of the refrigerant system when compressor is running and
opens to equalize the high and low pressure sides of the refrigerant system when the compressor is not running.
e. The expansion valve (9) controls the amount and pressure of liquid refrigerant to the restrictor (10) and the
evaporator coil (11). The expansion valve senses the temperature and pressure of the refrigerant as it leaves the
evaporator coil. By use of a sensing bulb and "external equalizer linc" the valve constantly adjusts the flow of liquid
refrigerant to the evaporator coil.
f. As the liquid refrigerant leaves the expansion valve (9) it passes through the restrictor (10) and enters the
evaporator coil (11). 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 fans
circulate 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, the air is
g. The low pressure refrigerant gas is then drawn back through the accumulator (16) to the compressor (2) and the
cycle is repeated.
h. The linear actuating cylinder (12) automatically controls the condenser air discharge louver assemblies to
maintain an adequate discharge pressure.