PRINCIPLES OF OPERATION
See figure 1-3.
a. Cooling Cycle
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 split condenser coil (3) and receiver (4).
The condenser fan draws outside ambient air over and through the two section condenser coil (3).
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 liquid sight glass (5) indicates the presence of moisture and quantity of refrigerant in the system.
The refrigerant desiccant dehydrator (filter drier) (6) removes any moisture (water vapor) or dirt that
may be carried by the liquid refrigerant.
The solenoid valve (7) is controlled by the temperature selector 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 and pressure of liquid refrigerant to the evaporator coil
(9). The expansion valve (8) senses the temperature and pressure of the refrigerant as it leaves the evaporator
coil. By use of the sensing 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 liquid refrigerant leaves the expansion valve (8) it enters the evaporator coil (9). 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 or "flash" to a gas. The evaporator blower circulates the warm air
from the conditioned space over and through the evaporator coil. Liquid absorbs heat when it changes from a
liquid to a gas. As the air from the conditioned spaces comes in contact with evaporator coil (9), the air is
To prevent compressor overload and damage during start up, solenoid valve (16) is open at start of
cooling cycle to equalize pressure on both sides of the compressor.
b. Bypass System. This unit has a bypass system which allows cooling operation at low cooling loads
without cycling the compressor on and off. In bypass the refrigerant is piped from the discharge to the suction
side of the compressor, bypassing the evaporator coil (9).
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).
As the compressor suction pressure starts to drop, the pressure regulator (11) opens to allow flow of
hot gas from the compressor.
The quench valve (17) senses the temperature of the gas at the suction side of the compressor. To
prevent excessively hot gas from reaching the compressor the quench valve (17) opens to allow liquid
refrigerant to mix with the hot gas.
The linear actuating cylinder assembly (15) automatically controls the condenser discharge louver
The service valves (12) are provided for charging, and general servicing of the high and low pressure
sides of the refrigerant system.