Mitsubishi Electric PUHY-P1000, Service Handbook

Page: 254 / 334

[8-3 Refrigerant Control Problems ]
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8-3 Refrigerant Control Problems
8-3-1 Units in the Cooling Mode Do Not Operate at Expected Capacity.
1. Phenomena
Although cooling operation starts with the normal remote controller display, the capacity is not enough
2. Cause, check method and remedy
Cause Check method and remedy
1. Compressor frequency does not rise sufficiently.

Faulty detection of pressure sensor.

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.
(1) Check pressure difference between the detected
pressure by the pressure sensor and the actual pres-
sure with self-diagnosis LED.
→
If the accurate pressure is not detected, check the
pressure sensor.
Refer to the following page(s). [8-5-1 Comparing the
High-Pressure Sensor Measurement and Gauge
Pressure](page 253)
Note: Lower inlet pressure by the low pressure sensor than
the actual pressure causes insufficient capacity.
SW4 setting (SW6-10: OFF)

For how to read the SW settings, refer to the follow-
ing page(s). [9-1-1 How to Read the LED](page 289)
(2) Check temperature difference between the evaporat-
ing temperature (Te) and the target evaporating tem-
perature (Tem) with self-diagnosis LED.
Note: Higher Te than Tem causes insufficient capacity.
SW4 setting (SW6-10: OFF)

For how to read the SW settings, refer to the follow-
ing page(s). [9-1-1 How to Read the LED](page 289)
Note: Protection works and compressor frequency does not
rise even at higher Te than Tem due to high discharge
temperature and high pressure.
At high discharge temperature:
Refer to the following page(s).[7-3-1 Error Code
[1102]](page 171)
At high pressure:
Refer to the following page(s). [7-3-3 Error Code
[1302] (during operation)](page 173)
2. Indoor unit LEV malfunction Refer to the following page(s).[8-8 Troubleshooting
LEV Problems](page 258)

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.

Refrigerant leak from LEV on the stopping unit
causes refrigerant shortage on the running unit.
High pressure sensor
Low pressure sensor
ON
SW4
1 2 3 4 5 6 7 8 9
10
OFF
ON
SW4
1 2 3 4 5 6 7 8 9
10 OFF
Evaporating temperature Te
Target evaporating temperature Tem
ON
SW4
1 2 3 4 5 6 7 8 9
10 OFF
ON
SW4
1 2 3 4 5 6 7 8 9
10
OFF