OPERATOR'S, UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE
AIR CONDITIONER, HORIZONTAL, COMPACT
THEORY OF OPERATION, COOLING AND HEATING
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 (3A) and (3B) and RECEIVER (4).
The condenser fan draws outside ambient air over and through the two section CONDENSER COIL (3A) and (3B). The high
temperature, high-pressure gas from the COMPRESSOR (1) is cooled by the flow of air and is changed into a high-pressure
The LIQUID SIGHT GLASS (5) indicates the presence of moisture and quantity of refrigerant in the system.
The DEHYDRATOR, DESICCANT, REFRIGERANT (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, 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 air from the conditioned spaces comes in
contact with the EVAPORATOR COIL (9), the air is cooled.
To prevent compressor overload and damage during start-up, pressure equalizing SOLENOID VALVE (15) is closed at start
of cooling cycle. This valve opens when compressor is not running to equalize pressure on both sides of compressor. b.
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 module 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 s tarts to drop, the PRESSURE REGULATOR (10) opens to allow flow of hot gas
from the compressor. The QUENCH VALVE (16) 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 (16) opens to allow liquid refrigerant to
mix with the hot gas.
The LINEAR ACTUATING CYLINDER ASSEMBLY (14) automatically controls the condenser discharge louver
The SERVICE VALVES (11) are provided for charging, and general servicing of the high and low- pressure sides of the
The LOW PRESSURE SWITCH (17), the HIGH PRESSURE SWITCH (13) and the PRESSURE RELIEF VALVE (12) are
provided to protect the unit from damage due to pressure extremes.
The flexible METAL HOSE ASSEMBLIES (2) and (18) provide vibration isolation between the compressor and other
components of the refrigeration system.