Mitsubishi Electric CITY MULTI PUHY-400YMF-B Service Handbook page 123

(2) Refrigerant Volume
1) 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, fluid level, fluid step, etc. and rendering an overall
judgment.
Note:
Depending on the operating state, AL = 0 has the meaning does not mean that there is insufficient refrigerant.
1 Discharge temperature is high. (125°C or higher)
2 Low pressure saturation temperature is extremely low.
3 Inlet superheating is high (if normal, SH = 20 deg. or lower).
4 Shell bottom temperature is high (the difference with the low pressure saturation
temperature is 70 deg. or greater)
5 Shell temperature is low (the difference with the low pressure saturation temperature is
10 deg. or lower).
6 Liquid level AL = 2
2) Cautions When Judging the Liquid Level
If you are judging the liquid level, be sure to use it only after making sure the liquid level sensor function (sensor and
heater) is operating normally.
1 Liquid Heater Disconnection Check
2 Liquid Heater Output Check
Turn 1 ON on the LED monitor display switch (SW1)
the signal for the heater relay to LED 5, then check the voltage of the heater terminal (AC
198 ~ 264 V) (leave the heater connections as they are).
3 Use the LED monitor display to check if there is misalignment between the actual
temperature and the detected temperature of TH2 ~ TH4.
3) Check the refrigerant volume by LED monitor display using the LED.
Set the LED monitor display switch (SW1) as shown below and check the past information (history) concerning the
refrigerant volume.
Set SW1 as shown in he figure at right.
If LD3 lights up, it indicates the refrigerant charge abnormal delay state just before emergency stop due to refriger-
ant overcharge (1500).
Condition
Check Items
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
ON
–120–
Refrigerant volume tends toward
insufficient.
Refrigerant volume tends toward
overcharge.
Judgment
Normal if the resistance is 2.8 kΩ ± 7 %.
Normal if AC 198 ~ 264 V is output
, and output
together with the LED lighting.
Judgment