Mitsubishi Electric CITY MULTI PUMY-P112VKM6 Service Manual page 45

1503 (P6): Freeze protection of plate heat exchanger / Freeze pro-
Abnormal points and detection methods
The purpose of the error code is to prevent indoor unit
from freezing or condensation which is caused when a
refrigerant keeps flowing into the indoor unit that is not
operating.
All of the following conditions have been satisfied:
• The compressor is operating in COOL mode.
• 15 minutes have passed after the startup of the com-
pressor, or the change in the number of operating
indoor units is made (including a change by turning
thermo-ON/OFF).
• After the condition 2 above is satisfied, the thermistor of
indoor unit in STOP detects TH22j ≤ −5 °C [23°F] for 5
consecutive minutes.
Diagnosis of failure
Check the port to which the piping and
wiring between the indoor unit and branch
box is connected.
Is the piping and wiring connected to the
same port?
Check the port to which the LEV wiring of
branch box is connected.
Is the wiring connected to the same port as
the corresponding branch box?
Check the LEV wiring of indoor unit that is
not via branch box is connected properly.
Disconnect the LEV wiring of branch box or
indoor unit to check the resistance.
Is the resistance detected?
OCH790 _45
tection of branch box or indoor unit
No
Yes
No
Yes
No
Yes
No
Yes
Causes and checkpoints
• Wrong piping connection between indoor unit and
branch box
• Miswiring between indoor unit and branch box
• Miswiring of LEV in branch box
• Malfunction of LEV in branch box
Connect the piping and wiring to the same port.
Connect the LEV wiring to the intended port
properly.
Connect the LEV wiring properly.
Replace the LEV coil.
Replace the LEV assy in branch box or the LEV
of indoor unit that is not via branch box.