Daikin Aurora Series, Service Manual, Page: 305 / 333

SiUS341802E Check
Service Diagnosis 292
3.6 Refrigerant Shortage Check
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 the information 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).
CHECK 7
Cooling
High pressure
Low pressure
Frequency
The opening degree of the indoor unit
electronic expansion valve becomes
larger.
Either of the electronic expansion
valves becomes fully open.
Frequency comes to the minimum level.
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.
High pressure drops
with decrease in
compressor capacity.
If frequency comes to the
minimum level, low
pressure cannot be
maintained.
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.
Heating
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
(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.
(Degree of refrigerant shortage)
Higher degree of shortage
Proper amount
(Low pressure
is maintained at
a constant
level.)
Frequency comes to
the minimum level.