Hitachi RAS-(4-12)HNP(1)(E) - Checking the Power Source and the Wiring Connection; Burnt-Out Compressor Due to an Insufficient Refrigerant Charge

12 Maintenance notes
472
SMGB0087 rev.0 - 12/2013
12.1 General notes
12.1.1 Checking the power source and the wiring connection
Check the following items in the case of abnormal operation:
No. Check item Procedure
1
Is the breaker or the fuse
cut out?
Check the secondary voltage of the breaker and the fuse by means of a tester.
2
Is the secondary power
source on the transformer
correct?
Disconnect the secondary side of the transformer and check the voltage by means of a tester.
Indoor unit
transformer
Secondary
side
Primary side
220, 230 or
240 V
Circuit and voltage
12 V
12 V
Primary side
220, 230 or
240 V
Indoor unit
transformer
Secondary
side
Circuit and voltage
3
Is the wiring loosened or
incorrectly connected?
Check the wiring connection on the PCB.
• Thermistor connectors
• Connector of the remote control cable
• Connector of the transformer
• Each connector in a high-voltage circuit (power source line)
Check the connectors according to the “4. Electrical wiring”.
12.1.2 Burnt-out compressor due to an insufcient refrigerant charge
Question and answer for the eld work
Example 1: Burnt-out compressor due to an insufcient refrigerant charge
Phenomenon
After commissioning the alarm code “08” sometimes occurred and the compressors were burnt out after ope-
rating for two months.
Cause
The refrigerant piping work was performed during the summer season. The additional refrigerant was not
sufciently charged from the discharge gas side.
This insufcient refrigerant charge resulted in the overheating of the discharge gas and the oil deterioration
which was nally due to the separated operation despite the alarm code “08”.
Countermeasure
1 The compressor was replaced with a new compressor.
2 The correct refrigerant amount was charged according to the refrigerant piping length and the connected
indoor units.
Remarks
Additional refrigerant charge: Open the liquid stop valves slightly when you charge the additional refrigerant
from the check joint of the liquid stop valves (the discharge gas side) during the cooling process. If the liquid
stop valve is fully open it is difcult to charge the additional refrigerant. Do not charge the refrigerant from the
gas stop valve.