System Controller - Mitsubishi PUHY-P250YJM-A Service Handbook

[ IX Troubleshooting ]

System controller

1. Phenomena
Although cooling operation starts with the normal remote controller display, the capacity is not enough
(1) Cause, check method and remedy
1. Compressor frequency does not rise sufficiently.
Inaccurate TH22 (Te) temperature reading
Protection works and compressor frequency does
not rise due to high discharge temperature
Protection works and compressor frequency does
not rise due to high pressure
Pressure drops excessively.
2. Indoor unit LEV malfunction
Insufficient refrigerant flows due to LEV malfunc-
tion (not enough opening) or protection works and
compressor frequency does not rise due to pres-
sure drop.
3. RPM error of the outdoor unit FAN
Motor failure or board failure, or airflow rate de-
crease due to clogging of the heat exchanger
The fan is not properly controlled as the outdoor
temperature cannot be precisely detected by the
temperature sensor.
The fan is not properly controlled as the pressure
cannot be precisely detected by the pressure sen-
sor.
HWE1018A
Cause Check method and remedy
(1) Check the difference between the temperature
reading by TH22 on the LED monitor and the actual
temperature.
-> Check the thermistor if there is a problem with
the temperature reading.
(Refer to the section that corresponds to error code
5102.)
Note: If the TH22 reading is lower than the actual temper-
ature, the units are operating at a lower perfor-
mance level than it should.
(2) Check temperature difference between the evapo-
rating temperature (Te) and the target evaporating
temperature (Tem) with self-diagnosis LED.
Note: Higher Te than Tem causes insufficient capacity.
SW1 setting
Evaporating temperature Te
Target evaporating temperature Tem
Note: Protection works and compressor frequency does
not rise even at higher Te than Tem due to high dis-
charge temperature and high pressure.
At high discharge temperature:
Refer to 1102.(page 127)
At high pressure:
Refer to 1302.(page 129)
Refer to the page of LEV troubleshooting ([4] -5-
).(page 185)
Refer to the page on troubleshooting of the outdoor
unit fan.
Refer to 5106.(page 143)
Refer to 1302.(page 129)
- 172 -
SW1
1 2 3 4 5 6 7 8 9 10
ON
SW1
1 2 3 4 5 6 7 8 9 10
ON
GB