1002 / 1119
HVAC
29
e. REFRIGERATION CYCLE TROUBLESHOOTING
Sr.
No.
Problem
Possible Cause
Remedy
4
Refrigerant
fails to circu-
late
Condition
Air conditioner does not cool.
Symptoms in refrigerant cycle
Pressure on the low pressure side is
vacuum
Pressure on the low pressure side is
vacuum low.
Frost or dew is formed on the piping at
the front and rear side of the receiver or
the expansion valve.
Cause
Moisture or dirt in the refrigerating cycle
freezes or sticks to the expansion valve
orifice, obstructing refrigerant flow.
Gas leaking from the heat sensitizing
tube of the expansion valve obstructs re-
frigerant flow.
Diagnosis
Blocked expansion valve orifice.
Countermeasures
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.
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 mal-
functioning
(opening too
much) and
improper in-
stallation of
heat sensitiz-
ing tube.
Condition
Air conditioner does not cool effectively.
Symptoms in refrigerant cycle
Pressure on both the low and high. pres-
sure sides is high.
Frost or heavy dew is formed on the pip-
ing on the low pressure side.
Cause
The expansion valve is malfunctioning or
the heat sensitizing tube is improperly in-
stalled.
Flow control is not properly performed
Diagnosis
Excessive liquid refrigerant in the low
pressure side piping.
Expansion valve opened too far.
Countermeasures
Check the installation of the
heat sensitizing tube.
If the installation is proper, re-
place the expansion valve.
6
Faulty com-
pression of
compressor
Condition
Air conditioner does not cool.
Symptoms in refrigerant cycle
Pressure on the low pressure sides is too
high and pressure on the high pressure
side is too low.
Cause
There is leakage in the compressor
Diagnosis
Faulty compression of compressor.
Delivery valve or packing is leaking or
broken or compressor is malfunctioning.
Countermeasures
Check the compressor oil for
contamination and quantity.
Replace the compressor.