Hitachi SAMURAI Series Service Manual page 133

4 Troubleshooting
Analysis and countermeasure of abnormalities
Phenomenon
Automatic
defrosting
mechanism
does not
Abnormal
activate.
adherence
of frost to
Inlet temperature of the condenser is short-
the heat
exchanger
during heating
operation.
Faulty low pressure sensor
Frost and ice adhere easily when it rains with
an outdoor temperature of about 0ºC.
Load bigger than cooling capacity.
Suction
pressure is
too low.
(Low
pressure
interruption
control
The machine
activated)
is working, but
the cooling
effect is poor
Discharge
pressure
too high
(High
pressure
switch
activation)
Malfunction of check valve
125 SMGB0120 rev.0 - 11/2017
Cause
Failure of thermistor for
defrosting
circuited.
Gas leakage or insufficient
amount of refrigerant
Clogging of expansion valve
Malfunction of the expansion
valve
Clogging of suction pipes
Malfunction of check valve
Insufficient volume of water
Pump inverse rotation
Formation of lime deposit
inside heat exchanger
Refrigerant overcharge
Mixture of non-condensable
gas in refrigerant cycle
Clogging of pipes at discharge
side
Clogging of expansion valve
Malfunction of expansion
valve
Faulty compressor
Check Item
Check activation of thermistor
for defrosting
Check and compare the
resistance of thermistor at
actual temperature
Check and compare the
indicated value of low pressure
and the actual pressure
—
Calculate heat load.
Check super heat
Check for clogging
Check operation of expansion
valve
Check whether there is temp
difference in the pipes
There is temperature difference
at the check valve
Check cold water inlet/outlet
temperature difference
Check rotational direction
Check for dirt at the heat
exchanger
Check cycle temperature
Stop the chiller unit and check
the relation between water
temperature and pressure
Check for clogging
Check for clogging
Check operation of expansion
valve
Check temperature difference
before and after check valve
Check pressure, cycle
temperature and current
Action · Countermeasure
Replace thermistor for defrosting
Replace the thermistor
Replace low pressure sensor
Defrost by means of manual
defrosting switch
Set the machine to a larger
capacity
Charge correct refrigerant volume
after checking gas leakage
Remove clogging
Replace expansion valve
Remove clogging
Replace check valve
Increase volume of water
Fix to correct direction
Clean heat exchanger
Charge correct volume
Recharge refrigerant after
vacuum pumping
Remove clogging.
Replace expansion valve
Replace check valve
Compressor replacement
4