Mitsubishi Electric PU(H)Y-P250YGM-A, Service Handbook

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[
VIII
Test Run Mode ]
[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.
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 60K
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 5K, an overcharging of refrigerant is suspected.