Mitsubishi Electric PQHY-P120THMU-A, Service Handbook

Page: 308 / 414

[
IX
Troubleshooting ]
- 299 - HWE09080 GB
Cause Check method and remedy
3. Long piping length
The cooling capacity varies greatly depending on the
pressure loss. (When the pressure loss is large, the
cooling capacity drops.) Check the piping length to determine if it is contrib-
uting to performance loss.
Piping pressure loss can be estimated from the
temperature difference between the indoor unit
heat exchanger outlet temperature and the satura-
tion temperature (Te) of 63LS. ->Correct the piping.
4. Piping size is not proper (thin)
5. Insufficient refrigerant amount
Protection works and compressor frequency does
not rise due to high discharge temperature. Refer to 1-1. (Compressor frequency does not rise
sufficiently.)(page 298)
Refer to the page on refrigerant amount
adjustment(page 177)
6. Clogging by foreign object Check the temperature difference between in front
of and behind the place where the foreign object is
clogging 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.
7. The indoor unit inlet temperature is excessively.
(Less than 15°C [59°F] WB) Check the inlet air temperature and for short cy-
cling. Change the environment where the indoor
unit is used.
8. Compressor failure
The amount of circulating refrigerant decreases due
to refrigerant leak in the compressor. Check the discharge temperature to determine if
the refrigerant leaks, as it rises if there is a leak.
9. LEV3 malfunction
Sufficient liquid refrigerant is not be supplied to the
indoor unit as sufficient sub cool cannot be secured
due to LEV3 malfunction. Refer to the page of LEV troubleshooting
( [4] -4- ).(page 310)
It most likely happens when there is little difference
or no difference between TH12 and TH15.
10. TH12, TH15 and 63HS1 sensor failure or faulty wir-
ing
LEV3 is not controlled normally.
Œ
Check the thermistor.
Œ
Check wiring.