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ARMY TM 9-4120-381-14
NAVY EE-000-CA-MMA-010/7053-AC
AIR FORCE TO 35E9-136-31
(7)
The sight glass (G) indicates the quantity of refrigerant in the system.
(8)
A solenoid valve (L1) is used to control refrigerant flow to the primary expansion valve (V12). When the air
conditioner is operated in redundant unit, remote control configuration the solenoid valve (L1) is always open.
When operated in single unit, local control configuration the solenoid valve (L1) is cycled open and closed by the
cool control thermostat located in the return air section of the air conditioner. The cool control thermostat also
opens and closes solenoid (L2) during the bypass cycle in all modes of operation.
(9)
The primary expansion valve (V12) controls the amount and pressure of liquid refrigerant to the evaporator coil
(E). By use of a sensing bulb and external equalizer line, the primary expansion valve (V12) senses the
temperature and pressure of the refrigerant as it leaves the evaporator coil (E) and constantly adjusts the flow of
liquid refrigerant.
(10)
As the liquid refrigerant leaves the primary expansion valve (V12) it passes through a distributor (D) and enters
the evaporator coil (E). The evaporator fan (B1) circulates warm air from the conditioned space over and
through the evaporator coil (E). As the liquid refrigerant enters the coil at reduced pressure, the combination of
pressure reduction and warmer air being forced across the tubes of the coil causes the refrigerant to boil and
change from a liquid to a gas. Refrigerant absorbs heat when it changes from a liquid to a gas. As the air from
the conditioned space comes in contact with the evaporator coil (E), the air is cooled.
(11)
After the refrigerant gas leaves the evaporator coil (E), it flows through the pressure regulator valve (V3) in
redundant unit configuration, or through the manual bypass valve (V7) if in single unit configuration. The
pressure regulator valve (V3) responds to supply air temperature in redundant unit, remote control configuration
and opens or closes to regulate evaporator coil (E) temperature and pressure. A temperature rise in the supply
air will cause the pressure regulator valve (V3) to open and decrease the evaporator temperature. A
temperature drop will cause the pressure regulator valve (V3) to close and increase evaporator temperature.
In single unit, local control configuration the pressure regulator valve (V3) is bypassed by opening the manual
bypass valve (V7). Temperature control is then performed by the return air cool control thermostat and solenoid
valve (L1) .
(12)
After the refrigerant gas passes through either the pressure regulator valve (V3) or manual bypass valve (V7),
the low pressure refrigerant gas then flows through the other half of the heat exchanger (H) where it is
superheated by the high pressure liquid refrigerant leaving the condenser coil (C).
(13)
The superheated refrigerant gas flows through a refrigerant strainer (F2) to remove any particles from the gas
before it flows into the compressor (B2).
(14)
The refrigerant gas is then drawn back to the compressor (B2) and the cycle is repeated.
(15)
A service valve (V1) allows the condenser fan damper actuator (A) to be isolated from, the refrigerant lines
during maintenance. A second service valve (V2) located between the receiver (R) and the heat exchanger (H)
isolates the low side-from the high side of the refrigerant lines during pump down. Another service valve (V6)
upstream of the hot gas bypass valve (V5) aids in isolating refrigerant flow during pump down.
(16)
Service valves (V8, V9) are provided for charging and general servicing of the high and low sides of the
refrigerant system.
(17)
Discharge service valve (V10) and suction service valve (V11) are provided for isolation of the compressor (B2)
during maintenance or replacement procedures.
(18)
The high refrigerant pressure switch (S4), low refrigerant pressure switch (S5), and low oil pressure switch (S7)
are provided to protect the compressor (B2) from damage due to pressure extremes.
(19)
Vibration eliminators (VE1, VE2) are installed in the compressor (B2) suction and discharge lines to isolate
compressor vibration from the other refrigerant piping.
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