General Notes; Checking The Power Source And The Wiring Connection; Insufficient Cooling Performance When A Long Piping Is Applied - Hitachi UTOPIA RAS-4HVRP2E Service Manual

11 Maintenance notes

General notes

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
1 Is the breaker of the fuse cut out? Check the secondary voltage of the breaker and the fuse by means of a tester.
Is the wiring loosened or
2
incorrectly connected?
11.1.2 Burnt-out compressor due to an insufficient refrigerant charge
Question and answer for the field work
Example 1: Burnt-out compressor due to an insufficient refrigerant charge
After commissioning the alarm code "08" sometimes occurred and the compressors were burnt out after operating
Phenomenon
for two months.
The refrigerant piping work was performed during the summer season. The additional refrigerant was not
sufficiently charged from the discharge gas side.
Cause
This insufficient refrigerant charge resulted in the overheating of the discharge gas and the oil deterioration which
was finally due to the separated operation despite the alarm code "08".
1
The compressor was replaced with a new compressor.
Countermeasure
2 The correct refrigerant amount was charged according to the refrigerant piping length.
Additional refrigerant charge: Open the liquid stop valves slightly when you charge the additional refrigerant from
Remarks 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 difficult to charge the additional refrigerant. Do not charge the refrigerant from the gas stop valve.

11.1.3 Insufficient cooling performance when a long piping is applied

Question and answer for the field work
Example 2: Insufficient cooling performance when a long piping is applied
Phenomenon
Sufficient cooling was not available for an indoor unit that was located at the farthest position.
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 insufficient cooling performance for the indoor unit.
Cause
Countermeasure The setting of the DSW2 was changed.
Pay special attention to the size of liquid pipe. Refer to "3. Piping work and refrigerant charge"
Remarks
details.
324 SMGB0136 rev.0 - 07/2021
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.
Indoor units
Insufficient
cooling
Procedure
Outdoor
unit
chapter for