1 - 1 1 . REFRIGERATION CYCLE. - continued
e. The EXPANSION VALVE (9) and DISTRIBUTOR (10) control the amount and pressure of liquid
refrigerant to the EVAPORATOR COIL (11). The EXPANSION VALVE (9) senses the temperature and pressure
of the refrigerant as it leaves the EVAPORATOR COIL (11). The valve constantly adjusts the flow of liquid
refrigerant to the EVAPORATOR COIL (11) depending on the heat load to the unit.
f. The liquid refrigerant leaves the EXPANSION VALVE (9) at a reduced pressure and enters the
EVAPORATOR COIL (11). The reduction in pressure and the warmer air being forced across the tubes of the coil
cause the refrigerant to evaporate. The EVAPORATOR FAN (12) circulates the warm air from the conditioned
space through the EVAPORATOR COIL (11). The refrigerant absorbs heat when it changes from a liquid to a gas
and is cooled.
g. The cold, low pressure refrigerant gas flows through the METAL HOSE ASSEMBLY (SUCTION) (13).
The gas is then drawn into the COMPRESSOR (1).
h. To prevent compressor overload and damage during start-up, SOLENOID VALVE (14) opens when
the compressor is not running to equalize system pressure. This valve closes at start of cooling cycle.
i. The SERVICE VALVES (15) are provided for charging, and general servicing of the high and low
pressure sides of the refrigerant system.
j. The PRESSURE SWITCH (LOW) (16), the PRESSURE SWITCH (HIGH) (17) and the PRESSURE
RELIEF VALVE (18) are provided to protect the unit from damage due to pressure extremes.
k. The flexible METAL HOSE ASSEMBLY (DISCHARGE) (2) and METAL HOSE ASSEMBLY
(SUCTION) (13) provide vibration isolation between the compressor and other components of the refrigeration
l. The LINEAR ACTUATOR CYLINDER (19) adjusts condenser discharge air dampers to regulate
system discharge pressure.
When the ROTARY SWITCH (mode selector) is set for HEAT, all heating elements, located behind the evaporator
coil are energized. These elements are protected from overheating by a thermal cutout switch. They are
thermostatically controlled by the POTENTIOMETER (temperature control).