Refrigerant Amount Adjustment; Refrigerant Amount And Operating Characteristics; Adjustment And Judgement Of Refrigerant Amount - Mitsubishi Electric CITY MULTI PUHY-80TMU-A Service Handbook

5

REFRIGERANT AMOUNT ADJUSTMENT

Clarify relationship between the refrigerant amount and operating characteristics of CITY MULTI, and perform service
activities such as decision and adjustment of refrigerant amount on the market.

[1] Refrigerant Amount and Operating Characteristics

The followings are refrigerant amount and operating characteristics which draw special attention.
During cooling operations, required refrigerant amount tends to increase (refrigerant in accumulator decreases)
1
in proportion to increase in the number of operating indoor units. However, the change of increase rate is small.
During heating operations, liquid level of accumulator is the highest when all the indoor units are operating.
2
Discharge temperature hardly changes when increasing or decreasing refrigerant amount with accumulator
3
filled with refrigerant.
During cooling operations, discharge temperature tends to rise at
overload than low temperature.
Tendency of
During heating operations, discharge temperature tends to rise at low
4
discharge
temperature than overload.
temperature
The lower the operating frequency is, the higher the discharge
temperature tends to become of deteriorated compressor efficiency.
Compressor shell temperature is 20~70 (36~126) degrees higher than low pressure saturation temperature
(Te) when refrigerant amount is appropriate.
5
→ Judged as over replenishment when temperature difference from low pressure saturation temperature (Te)
is 10 (18) degrees or less.
Note : ˚C Scale (˚F Scale)

[2] Adjustment and Judgement of Refrigerant Amount

(1) Symptom
The symptoms shown in the table below are the signs of excess or lack of refrigerant amount. Be sure to adjust the
amount of refrigerant in refrigerant amount adjustment mode, by checking operation status, judging refrigerant
amount, and performing selfdiagnosis with LED Dip s/w 1, 1-10, for overall judgement of excess or lack of refriger-
ant amount.
Emergency stop at 1500 remote controller display (excessive
1
refrigerant replenishment)
Operating frequency does not fully increase, thus resulting in
2
insufficient capacity
Emergency stop at 1102 remote controller display (discharge
3
temperature trouble)
Emergency stop occurs when the remote control display is at
4
1501. (insufficient refrigerant)
Excessive refrigerant replenishment
Insufficient refrigerant replenishment
Insufficient refrigerant
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Comparison including
control system