Mitsubishi Electric City Multi CMH-WM250V-A, Service Handbook

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[8-3 Refrigerant Control Problems ]
BS_08_E chapter 8 -
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Cause Check method and remedy
2. Actuation failure of the flow-control valve on the in-
door unit Refer to the following page(s). [8-8 Troubleshooting
LEV, FCV Problems]

Failure of the flow-control valve (not sufficiently
open) causes a drop in the water flow rate, trigger-
ing the protection mechanism and keeps the wa-
ter-pump frequency down.

Refrigerant leak from the flow-control valve on the
stopping unit causes refrigerant shortage on the
running unit.
3. RPM error of the outdoor unit FAN Refer to the following page(s).
[8-7 Troubleshooting Outdoor Unit Fan Problems]
[7-3-3 Error Code [1302] (during operation)]

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.) 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.
5. Piping size is not proper (thin)
6. Insufficient refrigerant amount
Protection works and compressor frequency does
not rise due to high discharge temperature. Refer to item 1 (Compressor frequency does not
rise sufficiently.) on the previous page.
Refer to the following page(s). [6-3 Evaluating and
Adjusting Refrigerant Charge]
7. 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.
8. The indoor unit temperature is excessively low. (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.
9. 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.
10. LEV1 malfunction
Sufficient liquid refrigerant is not be supplied to the
indoor unit as sufficient sub cool cannot be secured
due to LEV1 malfunction. Refer to the following page(s). [8-8 Troubleshooting
LEV, FCV Problems]
It most likely happens when there is little difference
or no difference between TH3 and TH6.
11. TH3, TH6 and 63HS1 sensor failure or damaged wir-
ing
LEV1 is not controlled normally.

Check the thermistor.

Check wiring.
12. LEV2 actuation failure
A drop in the low pressure that is caused either by a
blockage of liquid pipe or by a pressure loss and the
resultant slowing of refrigerant flow causes a tenden-
cy for the discharge temperature to rise. Refer to the following page(s).[8-8 Troubleshooting
LEV, FCV Problems]
13. 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. Refer to the following page(s). [8-8 Troubleshooting
LEV, FCV Problems]
14. Open phase in the power-supply due to improper
power-supply wiring. Make sure that the power-supply wiring is properly
connected. (Refer to item (5) in section [6-1 Read
before Test Run].)
Possible open phase.
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