Daikin VRV III REYQ8PY1, Service Manual

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Troubleshooting (OP: Unified ON/OFF Controller) Si37-701
356 Troubleshooting
[Check 11] 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 judgment, refer to information provided below.
Diagnosis of overcharge of refrigerant
1. High pressure rises. Consequently, overload control is exercised to cause scant 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 supercooled degree of condensate rises. Consequently, in heating operation, the
temperature of outlet air passing through the supercooled section becomes lower.
Cooling
High pressure
Low pressure
Frequency
High-pressure
drooping control
(LP is maintained
at a constant level.)
To maintain LP, frequency
increases under the capacity
control.
HP gradually rises
with increase in
frequency.
Frequency comes to
the minimum level.
Supercooled degree
becomes higher.
(Liquid connection
pipe temperature
lowers.)
LP rises due to
reduced compressor
output.
High pressure
Low pressure
Frequency
Heating
The outdoor unit motorized valve is
closed due to the overload control.
Frequency comes to
the minimum level.
(HP is maintained
at a constant level.)
LP rises due to
reduced frequency.
To maintain HP, frequency reduces
under the capacity control.
HP drops or rises immediately
after the overload control is
complete.
LP drops due to closed
outdoor unit motorized
valve.
Hot gas bypass is activated
for LP protection, i.e.,
hunting at LP.
Higher degree of overcharge
(Degree of overcharge)
Proper quantity