REFRIGERATION SYSTEM-Continued. - TM-5-4120-386-140176

TM 5-4120-386-14

5-9. REFRIGERATION SYSTEM-Continued.

(8) The temperature control switch will activate the normally open liquid

by-pass solenoid valve, and shut off the evaporator section of the unit. You will

notice that compressor will continue to pump as usual, and the suction pressure will

begin to drop.

(9) When the suction pressure reaches about 65 PSIG (4.6 kg/cm 2), the valve

starts to open in an effort to maintain the suction pressure above about 55 PSIG.

(3.86 kg/cm2)

(10) As the suction temperature goes up, due to the opening of the

pressure regulating valve, the quench expansion valve will start to

meter liquid refrigerant into the suction line to maintain the suction

temperature below 75F (24C).

(11) The action of the pressure regulating valve and quench valve is

automatic. This action may also occur at extreme conditions in an

attempt to maintain the suction pressure (even during the cooling mode)

at a point above 55 PSIG (3.86 kg/cm2) and the suction temperature

(measured at the quench bulb well) below 75F (24C).

(12) The condenser louvers are operated by a refrigerant-powered

actuator located in the high-pressure part of the system. This actuator

should be fully extended (louvers open) at approximately 80F (27 oC )

at 260-220 PSIG (18.3-15.5 kg/cm2) dischar e pressure, and fully

closed at 180-150 PSIG (12.67-10.56 kg/cm ). Failure to perform this function

could result in cutout on the high pressure cutout switch.

Refrigeration System Repair

The following paragraphs contain repairs covering commonly used hardware, the tubing

and valves of the refrigeration system. Re-use or repair of seals and gaskets should not

be attempted; new parts should be used at assembly. When heating refrigeration piping to

debraze or unsolder connections (See paragraph 5-12) as well as to solder or braze them,

the piping should be protected with a continuous flow of dry nitrogen to prevent scaling or

oxidation of the inside surface.

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