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Stoppage due to excessively high gas discharge pressure
1) High gas discharge pressure due to excess refrigerant
Analysis of Trouble
Loose frosting and poor refrigerating effect may occur if excessive refrigerant has been
charged into the system. Excess refrigerant will occupy additional space in the evaporator.
This will reduce its heat dissipating area, and the phenomenon of “liquid striking” may
occur. Condensation may occur on the gas return tube, and the gas discharge pressure will
rise. When it reaches the threshold value, the protective relay will actuate and shut off the
power supply to the compressor.
Remedy
Open the tubing. Re-evacuate and charge the system with a proper quantity of refrigerant.
2) Air in the system
Analysis of Trouble
The residual air in the system will circulate with the refrigerant in the system. The major
symptoms are higher gas discharge pressure, higher discharged gas temperature, and
poor refrigerating effect. The gas discharge pressure will exceed its maximum value when
the compressor has run for an extended period, and activates the protective relay.
Remedy
Check the air has been in the refrigerating system. Generally, there are three possibilities.
First, is that the air has been sucked into the system during repairs due to carelessness.
Secondly, it has not been completely purged evacuating the system. The third possibility
is that there are leak points at the low-pressure end of the refrigerating system. Leak
points appear in low temperature parts or assemblies. This is because the evaporation
temperature is lower for such low temperature devices, especially at the low-pressure
end; it is easier for the air to go into the system. Once it has been ascertained that air
does exist in the system, you have to open the tubing, re-evacuate it and then charge it
with refrigerant.
Stoppage due to electrical troubles
Thermostat is out of control due to electric troubles
Analysis of Trouble
In case the thermostat does not work in its good order or its temperature sensor has not
been installed properly, frequent stoppage is also likely to occur.
Remedy
Try to adjust the temperature sensor’s position until the compressor can be started and
stopped normally. If this cannot be achieved, and the stoppage still occurs repeatedly, it is
most likely that the mechanical parts or contacts are out of order, disassemble the
thermostat, make a thorough checkup and repair it.
