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SERVICE MANUAL
Model: HRF10WNDWW/HRF12WNDWW
21
Issue 2009-7-24
Rev. Ref0907S005V0
7-3 Analysis of Troubles
7-3-1 Sudden stop of Compressor during Its running
The cause of sudden stop of a compressor during its running is mostly that the gas suction pressure
and/or discharge pressure exceed their respective prescribed ranges, thus making a
pressure-operated protective relay shut off the power to the compressor and stop it. In the following we
discuss mainly the reasons for causing excessively high gas discharge pressure and low suction
pressure.
1) Stoppage due to excessively high gas discharge pressure
a) Too much refrigerant charged into the system
Analysis 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
