Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook, Page: 122 / 204

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REFRIGERANT AMOUNT ADJUSTMENT
By clarifying the relationship between the refrigerant amount and operating characteristics for Super Y Series, conduct
service activities such as decision on the amount and adjustment of refrigerant on the market.
[1] Operating Characteristics and Refrigerant Amount
The followings are operating characteristics and refrigerant amount which draw special attention.
[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 adjustment
amount in refrigerant amount adjustment mode, by checking operation status, judging refrigerant amount, and per-
forming LED monitor display with LED, for overall judgement of excess or lack of refrigerant amount.
1
2
3
4
5
During cooling operations, required refrigerant amount tends to increase (refrigerant in accumulator decreases)
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.
Discharge temperature hardly changes when increasing or decreasing refrigerant amount with accumulator
filled with refrigerant.
Compressor shell temperature is 20 ~ 70 degrees higher than low pressure saturation temperature (TH2) when
refrigerant amount is appropriate.
→
Judged as over replenishment when temperature difference from low pressure saturation temperature (TH2)
is 10 degrees or less.
Tendency of
discharge
temperature
During cooling operations, discharge temperature tends to rise at
overload than low temperature.
During heating operations, discharge temperature tends to rise at
low temperature than overload.
The lower operating frequency is, the higher discharge temperature
tends to become because of deteriorated compressor efficiency.
Comparison including
control system
1
2
3
4
Error stop at 1500 remote controller display
(excessive refrigerant replenishment)
Operating frequency does not fully increase, thus resulting in
insufficient capacity
Error stop at 1102 remote controller display
(discharge temperature trouble)
Error stop at 1501 remote controller display
(low refrigerant trouble)
Excessive refrigerant replenishment
Insufficient refrigerant replenishment