SiENBE28-901
Troubleshooting
Air Cooled Refrigeration Condensing Unit
135
[Check 6] Check for Refrigerant Amount
Due to relationship to pressure control and electronic expansion valve control, the refrigerant
amount needs to be judged according to operating conditions.
Refer to information shown below for making judgements.
Diagnosis of Refrigerant Overcharge
1. High pressure becomes higher. Consequently, overload control is exerted to make the
capacity slightly inadequate.
2. The superheated degree of suction gas becomes lower (or the system is put into wet
operation). Consequently, the compressor discharge pipe temperature becomes lower for
pressure loads.
3. The subcooled degree of condensate becomes higher.
Diagnosis of Refrigerant Shortage
1. The superheated degree of suction gas becomes higher, and the temperature of
compressor discharge gas also becomes higher.
2. The superheated degree of suction gas becomes higher, and the electronic expansion valve
shifts to slightly open.
3. Low pressure is too low to demonstrate cooling capacity (or heating capacity).
4. The liquid level gauge falls into the flash state.
High
pressure
Low
pressure
Operating
frequency
High pressure gradually rises with
increasing operating frequency.
(Low pressure is maintained
at a certain level.)
To maintain low pressure, operating
frequency increases on the capacity control.
(Degree of overcharge)
Proper amount
Further overcharge
High pressure drooping control
Operating frequency comes to the lowest level.
Subcooled degree becomes higher.
(The temperature of liquid
connection piping becomes lower.)
Low pressure rises with lowering
compressor output.
High
pressure
Low
pressure
Operating
frequency
The opening degree of the indoor unit
electronic expansion valve comes larger.
Either electronic expansion valve fully opens.
Fan control, i.e., actually hunting to
maintain high pressure on the cooling
control with low outdoor air
Operating frequency comes
to the lowest level.
(Low pressure is maintained
at a certain level.)
High pressure increases
due to compressor
capcity decreasing.
Low pressure rises with increasing
opening degree of the indoor unit
electronic expansion valve, and the
operating frequency slightly increases
due to the capacity control.
If the operating frequency reaches
the lowest level, low pressure
cannot be maintained.
To maintain low pressure, operating
frequency increases on the capacity control.
(Degree of refrigerant shortage)
Proper amount
Further short
