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Maintenance Service and Troubleshooting
2. Refrigerating system is clogged with ice
Analysis of Problem
The expansion valve can become clogged with ice if the moisture is not
removed properly from refrigerant system, air purging is done improperly, or the
water content in the refrigerant is substandard. The symptoms for this condition
are:
a. irregular refrigeration, sometimes working normally at the beginning, but,
afterward, frost forms at the clogged area;
b. evaporation temperature drops below 32°F;
c. water accumulates at and clogs the narrow part of the capillary;
d. frost melts at the evaporator;
e. no sound of gas flowing can be heard; and
f. The gas suction pressure becomes a vacuum.
Note that these occurrences will appear intermittently; sometimes the
refrigerator works well and other times it does not. In order to determine if the
system is clogged with ice, heat suspicious points with hot water to melt any ice.
If the sound of gas flowing is heard and the gas suction pressure rises, then the
system was clogged with ice.
Solution
If there is too much moisture in the refrigeration system, release the
refrigerant, purge the tubing system with nitrogen, and recharge the system with
filtered refrigerant. Another method is to connect a filter with moisture absorbers,
such as silica gel or anhydrous calcium chloride, to the refrigeration system.
Afterward, replace the filter, evacuate it, and recharge with refrigerant.
3. Refrigeration system is clogged with dirt
Analysis of Problem
Coarse-grained dirt and refrigerant oil tend to settle in and clog the capillary
inlet. If considerable dirt accumulates there, the whole filter screen may be
blocked, preventing the refrigerant from passing through. This problem exhibits
some of the same symptoms as when the refrigeration system is clogged with ice,
namely higher gas suction pressure, lower temperature of discharged gas, and
no sound of gas flowing in the evaporator. The difference between the two
problems is that if the clogging is caused by dirt, tapping the suspicious clogged
point(s)—normally in the capillary or in the connection joint of the filter—may
cause the refrigerant to flow through partially, resulting in some change, whereas
if it is heated with a hot towel, no change will occur. After dismissing the
possibility that the clogging is due to ice, it is safe to assume the clogging is
caused by dirt.
Solution
Dismantle the system, remove the dry filter, purge the tubing with nitrogen,
install a new filter, evacuate it, and charge it with refrigerant.
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