Mitsubishi Electric HP120TNU-A Service Handbook page 252

[8-3 Refrigerant Control Problems ]
3. RPM error of the outdoor unit FAN
Motor failure or board failure, or airflow rate de-
crease due to clogging of the heat exchanger
The fan is not properly controlled as the outdoor
temperature cannot be precisely detected by the
temperature sensor.
The fan is not properly controlled as the pressure
cannot be precisely detected by the pressure sen-
sor.
4. Long piping length
The cooling capacity varies greatly depending on the
pressure loss. (When the pressure loss is large, the
cooling capacity drops.)
5. Piping size is not proper (thin)
6. Insufficient refrigerant amount
Protection works and compressor frequency does
not rise due to high discharge temperature.
7. Clogging by foreign object
8. The indoor unit inlet temperature is excessively low.
(Less than 15°C [59°F] WB)
9. Compressor failure
The amount of circulating refrigerant decreases due
to refrigerant leak in the compressor.
10. BC controller LEV 3 actuation failure
Sufficient liquid refrigerant is not be supplied to the
indoor unit as sufficient sub cool cannot be secured
due to LEV3 malfunction.
11. BC controller LEV4 operation failure
(BC controller on JA and KA types only)
LEV4 fails to close, preventing BC controller from en-
suring sufficient subcool. As a result, the indoor unit
is not supplied with a sufficient amount of liquid re-
frigerant.
12. TH12, TH15 and 63HS1 sensor failure or faulty wir-
ing
LEV3 is not controlled normally.
13. The restrictions on pipe lengths have not been ob-
served
14. LEV9 malfunction
Not enough refrigerant is provided to the indoor or
outdoor unit due to high-low pressure bypass that re-
sults from the malfunction of LEV9.
15. Open phase in the power-supply due to improper
power-supply wiring
HWE18220_GB
Cause Check method and remedy
Refer to the following page(s).
[8-7 Troubleshooting Outdoor Unit Fan Problems]
[7-3-3 Error Code [1302] (during operation)]
Check the piping length to determine if it is contributing
to performance loss.
Piping pressure loss can be estimated from the tem-
perature difference between the indoor unit heat ex-
changer outlet temperature and the saturation
temperature (Te) of 63LS. Correct the piping.
Refer to item 1 (Compressor frequency does not rise
sufficiently.) on the previous page.
Refer to the following page(s). [6-3 Evaluating and Ad-
justing Refrigerant Charge]
Check the temperature difference between in front of
and behind the place where the foreign object is clog-
ging the pipe (upstream side and downstream side).
When the temperature drops significantly, the foreign
object may clog the pipe.
Remove the foreign object inside the pipe.
Check the inlet air temperature and for short cycling.
Change the environment where the indoor unit is
used.
Check the discharge temperature to determine if the
refrigerant leaks, as it rises if there is a leak.
Refer to the following page(s).[8-8 Troubleshooting
LEV Problems]
It most likely happens when there is little difference or
no difference between TH12 and TH15.
Refer to the following page(s).[8-8 Troubleshooting
LEV Problems]
This problem may occur when SC16 and SH2 are
small and when the difference between TH5 of the
outdoor unit and the evaporation temperature (Te) is
small.
Check the thermistor.
Check wiring.
Refer to the following page(s). [2-10 Restrictions on
Refrigerant Pipes]
Refer to the following page(s). [8-8 Troubleshooting
LEV Problems]
Make sure that the power-supply wiring is properly
connected. (Refer to item (6) in section [6-1 Read be-
fore Test Run].)
Possible open phase.
11
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