A)Too much refrigerant charged into the sy stem
Analys
is of Trouble
The phenomenon, such as loose frosting and poor refrigerating effect, may occur if excessive
refrigerant has been charged into the system. Superfluous refrigerant will occupy a certain
space of the evaporator, thus reduce its heat dissipating area, and the phenomenon of “liquid
striking” may occur, too. Meanwhile, dew or frost condensation may occur on the gas return
tube, and the gas discharge pressure will obviously 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 then charge the system with a proper quantity of refrigerant.
b) Air left in the system
Analysis of Trouble
The residual air in the system will circulate together with the refrigerant in the system. The
major symptoms caused by this residual air is higher gas discharge pressure, higher
discharged gas temperature (the gas discharge tubing is considerably hot when you feel it
with your hand), and poorer refrigerating effect. Furthermore, the gas discharge pressure will
exceed its normal value when the compressor has run for a period not too long, thus making
the protective relay actuate and bring to a stoppage.
Remedy
Check up how the air has been left in the refrigerating system. Generally, there are two
possibilities: one is that the air has been sucked into the system when repairing due to
carelessness, or it has not been purged out totally when evacuating the system; the other is
that there are leak points at the low pressure end of the refrigerating system. Leak points
appear mostly in those low temperature parts or assemblies, because the evaporation
temperature is lower for such low temperature devices, especially at the low pressure end, it
is easier for the air goes 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.
2) Stoppage due to electric troubles
a) Thermostat is out of control
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.
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