Refrigerant Control Problems; Units In The Cooling Mode Do Not Operate At Expected Capacity - Mitsubishi Electric HP120TNU-A Service Handbook

[8-3 Refrigerant Control Problems ]

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
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.
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.
Refrigerant leak from LEV on the stopping unit
causes refrigerant shortage on the running unit.
ON
1 2 3 4 5 6 7 8 9 10
10
- chapter 8
Cause
The figure at left shows that the switches 1 through 5 are set to ON and 6 through 10 are set to OFF.
Check method and remedy
(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]
Note: Lower inlet pressure by the low pressure sensor than
the actual pressure causes insufficient capacity.
SW4 setting (SW6-10: OFF)
High pressure sensor
SW4
Low pressure sensor
SW4
(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)
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 discharge
temperature and high pressure.
At high discharge temperature:
Refer to the following page(s). [7-3-1 Error Code
[1102]]
At high pressure:
Refer to the following page(s). [7-3-3 Error Code
[1302] (during operation)]
Refer to the following page(s).[8-8 Troubleshooting
LEV Problems]
ON
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
SW4
ON
1 2 3 4 5 6 7 8 9 10
SW4
ON
1 2 3 4 5 6 7 8 9 10
HWE18220_GB