Operating Characteristics And Refrigerant Amount; Adjustment And Judgment Of Refrigerant Amount - Mitsubishi Electric PURY-P200 Service Handbook

[3] Operating Characteristics and Refrigerant Amount

Clarify relationship between the refrigerant amount and operating characteristics of CITY MULTI new refrigerant series,
and perform service activities such as decision and adjustment of refrigerant amount on the market.
1. Operating characteristics and refrigerant amount
The followings are operating characteristics and refrigerant amount which draw special attention.
1 During cooling operation, the amount of refrigerant in the accumulator is the smallest when all indoor units are in operation.
2 During heating operations, liquid level of accumulator is the highest when all the indoor units are operating.
Discharge temperature is more likely to rise when there is a lack of refrigerant.
Tendency of
Little change in discharge temperature is seen, even if the refrigerant is increased or decreased while there
3 discharge
is refrigerant in the accumulator.
temperature
Discharge temperature is more likely to rise when high-pressure is high.
Discharge temperature is more likely to rise when the low temperature is low.
(P250-P650 types)
Compressor shell temperature is 10~60K higher than low pressure saturation temperature (Tc) when refrigerant amount is
appropriate.
→ Judged as over replenishment when temperature difference from low pressure saturation temperature (Te) is 5K or less.
4
(P200 type)
The shell temperature of the compressor is roughly equal to the discharge temperature.
→ Make a judgment from the discharge temperature

[4] Adjustment and Judgment 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
refrigerant amount in the refrigerant amount adjustment mode, by checking operation status, judging refrigerant amount
and performing selfdiagnosis with LED, for overall judgement of excess or lack of refrigerant amount.
1 Emergency stop at 1500 remote controller display (excessive refrigerant replenishment)
2 Operating frequency does not fully increase, thus resulting in insufficient capacity
3 Emergency stop at 1102 remote controller display (discharge temperature trouble)
2. Refrigerant volume
Checking the operating condition
Operate all the indoor units on cooling or on heating, checking the discharge temperature, sub-cooling, low
pressure saturation temperature, inlet temperature, shell bottom temperature, liquid level, liquid step, etc. and
rendering an overal l judgment.
1
Discharge temperature is high. (Normal temperature: 95˚C or below)
2 Low pressure is extremely low.
3 Inlet superheating is high (if normal, SH = 20K or lower).
(P250-P650 types)
Shell bottom temperature is high (the difference with the low pressure saturation
temperature ❉1 is 60K or greater)
4
(P200 type)
The shell temperature of the compressor is roughly equal to the discharge temperature.
→ Make a judgment from the discharge temperature
(P250-P650 types)
Shell bottom temperature is low (the difference with the low pressure saturation
temperature ❉1 is 5K or higher.)
5
(P200 type)
The shell temperature of the compressor is roughly equal to the discharge temperature.
→ Make a judgment from the discharge temperature
6 Inlet super heating is low (if normal, SH = 10K or higher).
❉1 Low pressure saturation temperature (Low pressure shell compressor)
Condition
- 109 -
,
Excessive refrigerant replenishment
Insufficient refrigerant replenishment
Judgement
Refrigerant volume tends toward
insufficient.
Rifrigerant volume tends toward
overcharge.