Mitsubishi Electric PUHY-HP120TNU-A, Service Handbook, Page: 209 / 324

[8-3 Refrigerant Control Problems ]
12
- chapter 8 HWE18240_GB
8 Troubleshooting Based on Observed Symptoms
8-3-2 Units in the Heating Mode Do Not Operate at Expected Capacity.
1. Phenomena
Although heating 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.
Œ
Faulty detection of pressure sensor.
Œ
Protection works and compressor frequency does
not rise due to high discharge temperature
Œ
Protection works and compressor frequency does
not rise due to high pressure.
(1) Check pressure difference between the detected
pressure by the pressure sensor and the actual
pressure with self-diagnosis LED.
ĺ
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: Higher inlet pressure by the high pressure sensor
than the actual pressure causes insufficient capac-
ity.
SW4 setting (SW6-10: OFF)
(2) Check the difference between the condensing tem-
perature (Tc) and the target condensing tempera-
ture (Tcm) with self-diagnosis LED.
Note: Higher Tc than Tcm causes insufficient capacity.
SW4 setting (SW6-10: OFF)
Note: Protection works and compressor frequency does
not rise even at lower Tc than Tcm due to high dis-
charge 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)]
High pressure sensor
Low pressure sensor
SW4
SW4
ON
1
2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
Condensing temperature Tc
Target condensing temperature Tcm
SW4
SW4
ON
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
The figure at left shows that the switches 1 through 5 are set to ON and 6 through 10 are set to OFF.