Mitsubishi Electric PUHY-P168, Service Handbook

Page: 321 / 404

- 312 -
[
IX
Troubleshooting ]
2 Although heating operation
starts with the normal remote
controller display, the capacity
is not enough. 1.Compressor frequency does not
rise sufficiently.
ΠFaulty detection of pressure
sensor.
ΠProtection works and compres-
sor frequency does not rise due
to high discharge temperature
ΠProtection works and compres-
sor frequency does not rise due
to high pressure.
(1) Check pressure difference between the
detected pressure by the pressure sen-
sor and the actual pressure with self-di-
agnosis LED.
-> If the accurate pressure is not de-
tected, check the pressure sensor.(Re-
fer to the page on Troubleshooting of
Pressure Sensor)
Note: Higher inlet pressure by the high
pressure sensor than the actual
pressure causes insufficient ca-
pacity.
SW1 setting
(2) Check the difference between the con-
densing temperature (Tc) and the tar-
get condensing temperature (Tcm) with
self-diagnosis LED.
Note: Higher Te than Tem causes in-
sufficient capacity.
SW1 setting
Protection works and compressor fre-
quency does not rise even at lower
Tc than Tcm due to high discharge
temperature and high pressure.
At high discharge temperature:
Refer to 1102
At high pressure: Refer to 1302
2.Indoor unit LEV malfunction
Insufficient refrigerant flows due
to LEV malfunction (not enough
opening).
Refer to the page of LEV troubleshooting (9.
[4]. -6- ).
3.When the higher temperature
than the actual temperature is de-
tected due to malfunction of the
piping sensor (TH22) on the in-
door unit, the smaller sub cool is
detected, and LEV opening will be
smaller.
Check the thermistor (TH22).
4.RPM error of the outdoor unit FAN
ΠMotor failure or board failure, or
airflow rate decrease, pressure
drop due to clogging of the heat
exchanger leading to high dis-
charge temperature
ΠThe fan is not properly controlled
as the temperature cannot be
precisely detected with the pip-
ing sensor.
Refer to the page on outdoor unit fan ([4] -4-
).
Phenomena Cause Check method and remedy
ON
ON
High pressure sensor
Low pressure sensor
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
Condensing temperature Tc
Target condensing temperature Tcm
ON
ON
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10