Units In The Heating Mode Do Not Operate At Expected Capacity - Mitsubishi Electric HP120TNU-A Service Handbook

[8-3 Refrigerant Control Problems ]
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
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.
ON
1 2 3 4 5 6 7 8 9 10
12
- 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
pressure 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 Mea-
surement 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)
High pressure sensor
Low pressure sensor
(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)
Condensing
temperature Tc
Target condensing
temperature Tcm
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)]
SW4
ON
1 2 3 4 5 6 7 8 9 10
SW4
ON
2 3 4 5 6 7 8 9 10
1
SW4
ON
2 3 4 5 6 7 8 9 10
1
SW4
ON
1 2 3 4 5 6 7 8 9 10
HWE18220_GB