Haier HB21T NN Service Manual page 33

Remedy
According to the operating procedures, it is mandatory to turn the machine off, and several
minutes later, open the refrigerant charging tube and let the refrigerant escape from it, replace
the dry filter, recharge refrigerant after evacuating, and then seal the charging port.
3) There is air left in the refrigerating system
Analysis of Trouble
Residual air in the refrigerating system will reduce its refrigerating efficiency .The prominent
phenomena are the increase in its gas suction and exhaust pressures (however, the gas
exhaust pressure will not exceed its rated value), obvious increase in temperature in the
segment from the compressor outlet to the condenser inlet. Because there is air in the system,
both the gas exhaust pressure and temperature will rise, and moreover, the gas flowing sound
is intermittent and obviously louder.
Remedy
After shut down for several minutes, open the tubing, evacuate it and then recharge the
system with refrigerant.
4) Low efficiency of compressor
Analysis of Trouble
Low efficiency of a refrigerating compressor refers to the actual reduction of gas discharge
capacity, and hence the corresponding reduction of refrigerating capacity, under the condition
that the refrigerant in the system is unchanged. This phenomenon occurs mostly when the
compressor has been used for quite a long time, its moving parts have worn to a considerable
degree, fit clearance between various parts have increased and sealing property of its gas
valve has deteriorated, resulting in an decrease in its actual gas discharge capacity.
Methods of Judgment
Measure the high and low pressures with pressure gauges to see whether they are normal. If
an abnormal sound comes from the compressor or the temperature of its causing is too high,
cut the discharge port open and operate the compressor, feel it if there is pressure at the
discharge port with your finger (For a normal compressor, its discharge port is difficult to be
blocked with your finger if you just apply a little effort).
5) Refrigerating oil left in evaporator tubing
Analysis of Trouble
During the process of refrigerating cycles, a little refrigerating oil may remain in the
evaporator tubing, and after a longer time of operation, if there is considerable refrigerating oil
left in the evaporator, the heat conduction effect will be severely affected, thus causing a poor
refrigerating effect.
Remedy
It is quite difficult to determine whether this trouble is caused by the refrigerating oil left in the
evaporator tubing, because this kind of phenomenon and other several trouble are tends to be
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