Operation Characteristics And Refrigerant Charge - Mitsubishi Electric HP120TNU-A Service Handbook

[6-2 Operation Characteristics and Refrigerant Charge ]

6-2

Operation Characteristics and Refrigerant Charge

It is important to have a clear understanding of the characteristics of refrigerant and the operating characteristics of air conditioners
before attempting to adjust the refrigerant amount in a given system.
The following shows items of particular importance.
1) During cooling operation, the amount of refrigerant in the accumulator is the smallest when all indoor units are in operation.
2) During heating operation, the amount of refrigerant in the accumulator is the largest when all indoor units are in operation.
3) General tendency of discharge temperature
Discharge temperature tends to rise when the system is short on refrigerant.
Changing the amount of refrigerant in the system while there is refrigerant in the accumulator has little effect on the discharge
temperature.
The higher the pressure, the more likely it is for the discharge temperature to rise.
The lower the pressure, the more likely it is for the discharge temperature to rise.
4) When the amount of refrigerant in the system is adequate, the compressor shell temperature is 10 to 60°C [18 to 108°F] higher
than the low pressure saturation temperature (Te).
If the temperature difference between the compressor shell temperature and low pressure saturation temperature (Te) is
smaller than 5°C [9°F], an overcharging of refrigerant is suspected.
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chapter 6 HWE18220_GB