Hitachi RAS-(2-3)HVRN(S)(2), Service Manual

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8 Troubleshooting
321
SMGB0064 rev.0 - 08/2011
8
•
Checking procedure for the electronic expansion valve
Valve position Electronic expansion valve Outdoor unit electronic expansion valve
Locked fully closed
Check the temperature of the piping in the heat-
ing process. Failure of the temperature to rise
indicates a fault.
It is abnormal if the liquid pipe pressure does
not increase during the cooling process.
Locked slightly open
The following conditions indicate a fault:
- Where the freeze protection thermistor tempe-
rature is lower than the intake air temperature.
-
Where the unit being inspected stops and
other units continue operating in cooling mode.
Electronic expansion valve
Freeze protection thermistor
It is abnormal if the liquid pipe pressure does
not increase and the outlet temperature of the
expansion valve decreases after the cooling
process starts.
Locked fully open
It is abnormal under the following conditions:
after the heating process for more than 30
minutes, the discharge gas temperature of
the compressor is not 10°C higher than the
condensing temperature and there is no other
faults, such as an excessive charge of refriger-
ant and others.}
• Fault diagnosis of DC fan motor
About fan motor fault diagnosis.
When ISPM/DIP-IPM is faulty and Alarm 53 appears, the fan motor may also be damaged. To prevent ISPM/DIP-IPM
damage which may result from operation combined with a faulty fan motor, check also if the fan motor is not damaged
when ISPM/DIP-IPM is replaced.
C A U T I O N
- For the shake of safety, turn OFF the power before start working.
- Working/checking with the power ON may disturb correct diagnosis and may result in failure.
Models for ES:
DC motor(s) included in different models:
Model Pieces
RAS-(2/2.5)HVRN2 1
RAS-3HVRNS2 1
RAS-(4-6)H(V)RNS2E 1
RAS-(8/10)HRNSE 1
Fault diagnosis procedure
1.
Remove fan motor connectors from the control PCB ISPM or DIP-IPM and turn the fan motor shaft by hand.
Normal: Fan motor shaft turns smoothly.
Faulty:
No continuous rotary torque movement felt when turning the motor by hand. This occurs because the internal
magnet of the fan motor breaks the movement when the internal electronic circuit of the fan motor has a short-
circuit fault
2. Measure the fan motor resistance using a tester.
Measurement procedure:
1.
Remove the fan motor connector from the control PCB, ISPM or DIP-IPM.
2. Connect the black test lead of the tester to the black wire pin of the fan motor connector
3. Connect the red test lead to the wire connector pin to be checked
Results
Normal:
Observed values will be close to the normal values in the table below
Faulty:
Observed values will be deviated from the normal values in the table below.
Generally an open-circuit fault shows ∞, and a short-circuit fault shows several Ω-kΩ.)
Internal electronic circuit fault of the fan motor including short-circuit and breakage can be checked