Daikin REYQ-TA Series, Service Manual

Page: 292 / 324

Check SiUS371614E
279 Service Diagnosis
4.5 Refrigerant Overcharge Check
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 the information below.
Diagnosis of overcharge of refrigerant
1. High pressure rises. Consequently, overload control is conducted to cause insufficient cooling
capacity.
2. The superheated degree of suction gas lowers (or the wet operation is performed).
Consequently, the compressor becomes lower in discharge pipe temperature despite of
pressure loads.
3. The subcooled degree of condensate rises. Consequently, in heating, the temperature of
discharge air through the subcooled section becomes lower.
CHECK 6
Cooling
High pressure
Low pressure
Frequency
High pressure
gradually rises with
increase in
frequency.
Subcooling degree
becomes higher.
(Liquid connection
pipe temperature
lowers.)
Low pressure rises due
to decreased
compressor output.
High pressure
Low pressure
Frequency
Heating
The outdoor 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 decreased
frequency.
To maintain high pressure ,
frequency decreases under the
capacity control.
High pressure drops or rises
immediately after the overload
control is complete.
Low pressure drops due to
closed outdoor unit
electronic expansion valve.
Hot gas bypass is activated
for
low pressure protection,
i.e., hunting at low pressure .
Higher degree of overcharge
(Degree of overcharge)
Proper amount
To maintain low pressure, frequency
increases under the capacity
control.
Frequency comes to
the minimum level.
High pressure
drooping control
(Low pressure is
maintained at a
constant level.)