Hitachi UTOPIA RAS-4HVRP2E - Checking the Power Source and the Wiring Connection; General Notes; Insufficient Cooling Performance When a Long Piping Is Applied

11 Maintenance notes
General notes
SMGB0136 rev.0 - 07/2021
324
11.1 General notes
11.1.1 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 of the fuse cut out? Check the secondary voltage of the breaker and the fuse by means of a tester.
2
Is the wiring loosened or
incorrectly connected?
Check the wiring connection on the PCB.
• Thermistor connectors
• Connector of the Unit controller cable
• Each connector in a high-voltage circuit
Check the connectors according to the electrical wiring diagram.
11.1.2 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 operating
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.
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.
11.1.3 Insufcient cooling performance when a long piping is applied
Question and answer for the eld work
Example 2: Insufcient cooling performance when a long piping is applied
Phenomenon Sufcient cooling was not available for an indoor unit that was located at the farthest position.
Cause
If the location of an outdoor unit is 20 meters lower than the location of the indoor units resetting of the DIP
switch DSW2 is required.
However no setting was performed. Therefore the largest discharge pressure was not increased. This resulted
in an insufcient cooling performance for the indoor unit.
Insufcient
cooling
Indoor units
Outdoor
unit
Countermeasure The setting of the DSW2 was changed.
Remarks
Pay special attention to the size of liquid pipe. Refer to “3. Piping work and refrigerant charge” chapter for
details.