Daikin VRV II-Q RQYQ8-48PY1B Service Manual page 195

SiBE341027
CHECK 7
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
2. The superheated degree of suction gas rises. Consequently, the electronic expansion valve
3. Low pressure drops to cause the unit not to demonstrate cooling capacity (heating capacity).
Service Diagnosis
temperature becomes higher.
turns open.
Cooling
The opening degree of the indoor unit
electronic expansion valve becomes larger.
High pressure
Low pressure
Low pressure rises as the
opening degree of the indoor
unit electronic expansion valve
becomes larger. Frequency
slightly increases under
the capacity control.
Frequency
Heating
The opening degree of the outside unit electronic expansion valve becomes larger.
High pressure
Low pressure
Frequency
To maintain low pressure,
frequency drops due to the
capacity control.
Proper quantity
Either of the electronic expansion
valves becomes fully open.
Frequency comes to the minimum level.
High pressure drops
(Low pressure is
with decrease in
maintained at a
compressor capacity.
constant level.)
To maintain low
pressure, frequency
drops due to the
capacity control.
The outside unit electronic expansion valve fully opens and frequency increases.
Discharge pipe or low pressure drooping control
(High pressure is
maintained at a
constant level.)
Frequency drops
due to the drooping
control.
(Degree of refrigerant shortage)
Troubleshooting by Remote Controller
Fan control is activated for high
pressure protection under
cooling control at low outdoor
air temperature, i.e., the fan is
hunting at high pressure.
If frequency comes to the
minimum level, low
pressure cannot be
maintained.
Frequency comes to
the minimum level.
Higher degree of shortage
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