Daikin RXYQ96PYDN, Service Manual

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SiUS34-801A_b Troubleshooting (OP: Unified ON/OFF Controller)
Troubleshooting 469
[Check 12] Check for shortage of refrigerant.
In case of VRV Systems, the only way to judge as the shortage of refrigerant is with operating
conditions due to the relationship to pressure control and electronic expansion valve control.
As information for making a judgment, refer to information provided below.
Diagnosis of shortage of refrigerant
1. The superheated degree of suction gas rises. Consequently, the compressor discharge gas
temperature becomes higher.
2. The superheated degree of suction gas rises. Consequently, the electronic expansion valve
opens.
3. Low pressure drops to cause the unit not to demonstrate cooling capacity (heating capacity).
Cooling
High pressure
Low pressure
Frequency
The opening degree of the indoor unit
motorized valve becomes larger.
Either of the motorized valves
becomes fully open.
Frequency comes to the minimum level.
Fan control is activated for HP
protection under cooling control
at low outdoor temperature,
i.e., the fan is hunting at HP.
HP drops with decrease
in compressor capacity.
If frequency comes to the
minimum level, LP
cannot be maintained.
LP rises as the opening
degree of the indoor unit
motorized valve becomes
larger. Frequency slightly
increases under the
capacity control.
To maintain LP,
frequency drops
due to the
capacity control.
Heating
High pressure
Low pressure
Frequency
The opening degree of the outdoor unit motorized valve becomes larger.
The outdoor unit motorized valve fully opens and frequency increases.
Discharge pipe or LP drooping control
(HP is maintained
at a constant level.)
Frequency comes to
the minimum level.
To maintain LP, frequency
drops due to the capacity
control.
Frequency drops
due to the drooping
control.
(Degree of refrigerant shortage)
Higher degree of shortage
Proper quantity
(LP is maintained
at a constant level.)