Maintenance Service and Trouble Shooting
refrigerating effect is due to the accumulation of refrigerating oil left in the
evaporator tubing in case no other troubles have been found . To clear off
refrigerating oil left in the evaporator ,dismantle the evaporator ,purge it
thoroughly and then dry it .In case it is difficult to dismantle it ,charge
refrigerant from the evaporator inlet to wash it several times ,then purge
and dry it with nitrogen .
7) Flowing obstructed in refrigerating system
Analysis of Trouble
Because the refrigerating system was originally not purged
thoroughly ,some of the filter screen meshes have been clogged by dirt
accumulated in the filter after using it for a certain time of period ,thus
resulting in a decrease in flow rate ,and hence a poorer refrigerating effect .
The abnormal phenomena caused by this kind of slight clogging in the
system are as follows: the gas discharge pressure is lower ,the
temperature of discharged gas drops down ,the position clogged has a
temperature lower than that in normal conditions ,and for a severe
clogging ,even dew condensation as frosting may appear .
Remedy
Purge the tubing , and after replacing the dry filter with a new one or
clearing it thoroughly ,recharge the system with refrigerant and seal the
charging port .
B. No Refrigerating
The phenomenon that the compressor runs normally , but no frost (or
only a little frost ) appears on the evaporator ,and the refrigerator
temperature does not drop down is called "no refrigerating". There are
many causes for this trouble and it is relatively complicated , too . In
servicing ,special attention to finding direct causes for this
phenomenon .Three main potential causes for this trouble are analyzed
below :
1) All refrigerant in the system has leaked out
Analysis of Trouble
Leak points in the refrigerating system have not been found and
repaired timely ,thus resulting in the total escape of refrigerant .There are
two kinds of leakage :I)
slow leakage
for instance ,when we want to use a
refrigerator that has been put out of quite a long time ,we find the leakage
of refrigerant ,or in the course of its operation ,we have found that the
refrigerator is gradually becoming not so cold and finally no refrigerating
cab be achieved ; ii)
fast leakage
in that case ,all the refrigerant will
escape swiftly due to abrupt rupture of system tubing .
Symptoms of total leakage of refrigerant are mainly asfollows : the
compressor can be started easily (if there is no damage to the compressor
parts) and its operating current becomes low ,its gas suction pressure is
high and discharge pressure is lower ,the gas discharge tube feels rather
cold ,no sound of gas eruption from the liquid in the evaporator can be
20
