12-6
CONTROL SYSTEM
SM CKDDCI 2-A.3 GB
12.3
General Operating Rules
12.3.1
Communication with Indoor Unit
12.3.1.1 Communication Failures Definition
12.3.1.1.1 Bad Communication’ fault
The system keeps a balance of a good/bad communication packet ratio. When the ratio
becomes high the system enters ‘Bad Communication’ fault. The system recovers from that
fault when the ratio becomes small again.
When in ‘Bad Communication’ fault, system continues its normal operation and fault code is
shown in diagnostics.
12.3.1.1.2 ‘No Communication’ fault
If no legal transmission or no message received for 30 seconds, system enters ‘No
Communication’ fault.
When in ‘No Communication’ fault, the fault code will be shown in diagnostics. In this case,
the system will force the compressor to off.
The system will recover from ‘No Communication’ fault when counter is below 10 and legal
massage is received.
12.3.2 Temperature
Measurements
12.3.2.1 Thermistor failures definition
Thermistor
Thermistor is Disconnected Thermistor is Shorted
OCT
Temp < -35 °C
Temp > 75 °C
OAT
Temp < -30 °C
Temp > 75 °C
CTT
Temp < -30 °C
Temp > 130 °C
HST
Temp < -30 °C
Temp > 125 °C
OMT
Temp < -30 °C
Temp > 75 °C
ICT
Temp < -30 °C
Temp > 75 °C
RAT
Temp < -30 °C
Temp > 75 °C
12.3.2.2 System responses for different thermistor failure
Thermistor
Default value
System Reaction
COOL
HEAT
OCT
1°C
1°C
(1)
OAT
43°C
6°C
CTT
43°C
43°C
Forced compressor to OFF
HST
75°C
75°C
Forced compressor to OFF
OMT
43°C
43°C
Replaced by OCT
(1)
ICT
43°C
43°C
RAT
SPT+4°C
SPT-4°C
Notes:
(1)
Whenever both OCT and OMT are faulty the compressor will be forced to OFF.
(2)
Thermistor is defined as faulty (shorted/disconnected) if it’s faulty for more than 10 seconds continuously.
During this time, the system uses the last valid temperature.
