Daikin REYQ8-48PY1B, Service Manual

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SiBE37-701_B Troubleshooting (OP: Unified ON/OFF Controller)
Troubleshooting 392
[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 judgement, 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
turns open.
3. Low pressure drops to cause the unit not to demonstrate cooling capacity (heating capacity).
Cooling
Heating
The opening degree of the indoor unit
electronic expansion valve becomes larger.
Either of the electronic expansion
valves becomes fully open.
Fan control is activated for high
pressure protection under
cooling control at low outdoor
temperature, i.e., the fan is
hunting at high pressure.
Frequency comes to the minimum level.
High pressure
Low pressure
Frequency
High pressure drops with decrease
in compressor capacity.
(Low pressure is
maintained at a
constant level.)
Low pressure rises as the
opening degree of the indoor
unit electronic expansion
valve becomes larger.
Frequency slightly increases
under the capacity control.
To maintain low
pressure,
frequency drops
due to the capacity
control.
If frequency comes to the
minimum level, low pressure
cannot be maintained.
High pressure
Low pressure
Frequency
The opening degree of the outdoor unit electronic expansion valve becomes larger.
The outdoor unit electronic expansion valve fully opens and frequency increases.
Discharge pipe or low pressure drooping control
Frequency comes to
the minimum level.
(High pressure is
maintained at a
constant level.)
To maintain low pressure,
frequency drops due to
the capacity control.
Frequency drops
due to the drooping
control.
Proper quantity
(Degree of refrigerant shortage)
Higher degree of shortage