Daikin VRV II-Q RQYQ8-48PY1B Service Manual page 194

Troubleshooting by Remote Controller
CHECK 6
Check for overcharge of refrigerant.
In case of VRV Systems, the only way to judge as the overcharge 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 overcharge of refrigerant
1. High pressure rises. Consequently, overload control is exercised to cause scant cooling
2. The superheated degree of suction gas lowers (or the wet operation is performed).
3. The subcooled degree of condensing rises. Consequently, in heating operation, the
184
capacity.
Consequently, the compressor becomes lower in discharge pipe temperature despite of
pressure loads.
temperature of outlet air passing through the subcooled section becomes lower.
Cooling
High pressure
Low pressure
Frequency
Heating
High pressure
Low pressure
Frequency
To maintain high pressure,
frequency reduces under the
capacity control.
Proper quantity
High pressure
drooping control
High pressure
gradually rises with
increase in frequency.
(Low pressure is
maintained at a
constant level.)
To maintain low pressure,
frequency increases under
the capacity control.
The outside unit electronic
expansion valve is closed due to
the overload control.
Frequency comes to
the minimum level.
(High pressure is maintained
at a constant level.)
Low pressure rises
due to reduced
frequency.
(Degree of overcharge)
SiBE341027
Frequency comes to
the minimum level.
Subcooled degree
becomes higher.
(Liquid connection
pipe temperature
lowers.)
Low pressure rises
due to reduced
compressor output.
High pressure drops or rises
immediately after the overload
control is complete.
Low pressure drops due to
closed outside unit electronic
expansion valve.
Hot gas bypass is activated
for low pressure protection,
i.e., hunting at low pressure.
Higher degree of overcharge
Service Diagnosis