Refrigerant Amount Adjustment; Operating Characteristics And Refrigerant Amount; Adjustment And Judgement Of Refrigerant Amount - Mitsubishi Electric CITY MULTI PUHY-P400YEM-A Service Handbook

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REFRIGERANT AMOUNT ADJUSTMENT

By clarifying the relationship between the refrigerant amount and operating characterstics, 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.
1 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.
2
During heating operations, liquid level of accumulator is the highest when all the indoor units are operating.
3
Discharge temperature hardly changes when increasing or decreasing refrigerant amount with accumulator
filled with refrigerant.
During cooling operations, at high ambient temperature the
4
discharge temperature tends to rise.
Tendency of
During heating operations, at low ambient temperature the
discharge
discharge temperature tends to rise.
temperature
The lower the operating frequency is, the higher the discharge temperature
tends to become because of deteriorated compressor efficiency.
5
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.

[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 LED monitor display with LED Dip S/W1, 1-10, for overall judgement of excess or lack of refrigerant
amount.
1
Error stop at 1500 remote controller display
(excessive refrigerant replenishment)
2 Operating frequency does not fully increase, thus resulting in
insufficient capacity
3 Error stop at 1102 remote controller display
(discharge temperature trouble)
4 Error stop at 1501 remote controller display
(low refrigerant trouble)
Excessive refrigerant replenishment
Insufficient refrigerant replenishment
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Comparison including
control system