174
TROUBLESHOOTING
Error code
Contents Error detection / Judgment
RC
display
Outdoor control PCB
Code Sub code
U7 4 6 Communication failure between
outdoor units 7
<Usual communication failure under combined installation>
Master unit: Among the following list, the same thing occurs
3 times or more within 10 seconds.
1. The master unit receives a reply to usual transmission from
master to dependent 1 when 0 dependent unit is connected.
2. The master unit receives a reply to usual transmission from
master to dependent 2 when 0 dependent unit is connected.
3. The master unit receives a reply to usual transmission from
master to dependent 2 when 1 dependent unit is connected.
4. The master unit receives 1 or more replies to 1 usual trans-
mission from master to dependent 1 when 2 dependent units
is connected.
5. The master unit receives 2 or more replies to 1 usual trans-
mission from master to dependent 1 when 2 dependent units
is connected.
6. The master unit receives 2 or more replies to 1 usual trans-
mission from master to dependent 2 when 2 dependent units
is connected.
7. From the outdoor unit other than itself, the master unit
receives usual transmission from master to dependent 1 or
from master to dependent 2.
U8
－－Main - sub remote controllers
transmission failure
Sub remote controller detection
U9
－－Failure of other indoor units in
the same system
An indoor unit detects an error to be treated with the procedure
A ~ E shown below.
5 n (Air net
address)
Transmission failure between
indoor and outdoor units
The outdoor unit detects transmission failure between indoor
and outdoor units.
－ 3 0 Normal communication is impossible 20 minutes after turning
the power ON or rewiring.
※ 1) A: The system stops the engine immediately and disengages the compressor. The outdoor unit conducts 3-minute forced cooling
(operates fan motor forcibly for 3 minutes, then stops fan motor, and stops the engine coolant pump 10 seconds later).
(As for combined installation, 2 outdoor units stop immediataly and conduct cooling for 3 minutes.)
B: The system stops the engine immediately and disengages the compressor. The outdoor unit conducts ordinary cooling.
(The outdoor unit operates the fan motor until the engine coolant temperature and refrigerant high pressure reach a level below
the specified values, then stops the engine coolant pump 10 seconds later). (As for combined installation, 2 outdoor units stop
immediataly and each outdoor unit conducts cooling individually.)
C: The system stops the engine after the pump down and disengages the compressor. The outdoor unit conducts ordinary cooling.
(As for combined installation, 1 outdoor unit conducts pump down operation. When 2 outdoor units are operating, 1 unit stops
first normally.)
D: The system suspends the outdoor unit start-up procedure.
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