Operating Characteristic And Refrigerant Amount - Mitsubishi Electric City Multi PQHY-P72 Service Handbook

[3] Operating Characteristic and Refrigerant Amount

It is important to have a clear understanding of the characteristics of refrigerant and the operating characteristics of air condi-
tioners before attempting to adjust the refrigerant amount in a given system.

1. Operating characteristic and refrigerant amount

The following table shows items of particular importance.
During cooling operation, the amount of refrigerant in the accumulator is the smallest when all indoor units are in
1
operation.
During heating operation, the amount of refrigerant in the accumulator is the largest when all indoor units are in
2
operation.
Discharge temperature tends to rise when the system is short on refrigerant.
General
Changing the amount of refrigerant in the system while there is refrigerant in the accumulator has
tendency of
little effect on the discharge temperature.
3
discharge
The higher the pressure, the more likely it is for the discharge temperature to rise.
temperature
The lower the pressure, the more likely it is for the discharge temperature to rise.
When the amount of refrigerant in the system is adequate, the compressor shell temperature is 10 to 60K
[18 to 108°F] higher than the low pressure saturation temperature (Te).
4
→ If the temperature difference between the compressor shell temperature and low pressure saturation tem-
perature (Te) is smaller than 5K [9°F], an overcharging of refrigerant is suspected.
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