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HVAC
33
e. REFRIGERATION CYCLE TROUBLESHOOTING
Sr.
No.
Problem
Possible Cause
Remedy
4
Refrigerant fails
to circulate
Condition
29. Air conditioner does not cool.
Symptoms in refrigerant cycle
30. Pressure on the low pressure side is
vacuum
31. Pressure on the low pressure side is
vacuum low.
32. Frost or dew is formed on the piping at
the front and rear side of the receiver or
the expansion valve.
Cause
33. Moisture or dirt in the refrigerating cycle
freezes or sticks to the expansion valve
orifice, obstructing refrigerant flow.
34. Gas leaking from the heat sensitizing
tube of the expansion valve obstructs re-
frigerant flow.
Diagnosis
35.
Blocked expansion valve orifice.
Countermeasures
36. Allow to stand for some time
and then resume operation to
decide whether the blockage is
caused by moisture or by dirt.
If caused by moisture; remove
the moisture by evacuation,
Recharge new refrigerant to
the specified amount.
37.
If cased by dirt; remove the
expansion valve and blow out
the dirt with compressed air. If
unable to remove the dirt, re-
place the expansion valve.
Evacuate and charge new re-
frigerant to the specified
amount. If caused by gas leak-
ing from heat sensitizing tube,
replace the expansion valve.
5
Expansion
valve malfunc-
tioning
(opening too
much) and im-
proper
installation of
heat sensitizing
tube.
Condition
38. Air conditioner does not cool effectively.
Symptoms in refrigerant cycle
39. Pressure on both the low and high.
pressure sides is high.
40. Frost or heavy dew is formed on the
piping on the low pressure side.
Cause
41. The expansion valve is malfunctioning
or the heat sensitizing tube is improperly
installed.
42. Flow control is not properly performed
Diagnosis
43. Excessive liquid refrigerant in the low
pressure side piping.
44. Expansion valve opened too far.
Countermeasures
45. Check the installation of the
heat sensitizing tube.
46.
If the installation is proper,
replace the expansion valve.
6
Faulty com-
pression of
compressor
Condition
47. Air conditioner does not cool.
Symptoms in refrigerant cycle
48. Pressure on the low pressure sides is
too high and pressure on the high pres-
sure side is too low.
Cause
49. There is leakage in the compressor
Diagnosis
50. Faulty compression of compressor.
51.
Delivery valve or packing is leaking or
broken or compressor is malfunctioning.
Countermeasures
52. Check the compressor oil for
contamination and quantity.
53.
Replace the compressor.