Service manual
15-4
CONTROL SYSTEM > GC 24
SM HADDCI 1-A.2 GB
15.3.2 Communication with Indoor Units
15.3.2.1 Communication Failures Definition
Two types of communication failures are diagnosed. The communication failures are checked separately for
IDU channel.
15.3.2.1.1 ‘Bad Communication’ fault
The system keeps a balance of a good/bad communication packet ratio for communication channel. When the
ratio getting high , system enters ‘Bad Communication’ fault.
15.3.2.1.2 ‘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 system will act as following:
♣ If there is no communication, the following will be performed:
The unit changes to SB.
1.
The system will scan all the communication.2.
Each channel that is identified as ‘no communication’ channel will be referred as STBY unit.3.
The unit resumes its normal operation with only the operative channels.4.
15.3.3 Temperature Measurements
15.3.3.1 Thermistor failures definition
Thermistor Thermistor is Disconnected Thermistor is Shorted
OCT Temp < -40 °C Temp > 75 °C
OAT Temp < -40 °C Temp > 75 °C
CTT Temp < -30 °C Temp > 130 °C
OMT Temp < -40 °C Temp > 75 °C
HST Temp < -30 °C Temp > 130 °C
15.3.3.2 System responses for different thermistor failure
Thermistor Default value System Reaction
OCT 6°C
OAT Cool 35°C Heat 7°C
CTT 43°C Forced compressor to OFF after 20 minutes.
OMT 43°C
HST 43°C
ICT 43°C
15.3.4 Flash Memory Programming
In order to upgrade the ODU software the auxiliary port will be used. A special application should be run on a
PC to transmit the new firmware.
15.4 Indoor Unit Control
15.4.1 Indoor Fan Control
10 Indoor fan speeds are determined for each model. 5 speeds for each mode cool/dry/fan or heat.
When user sets the indoor fan speed to a fixed speed (Low/ Medium/ High), unit will operate constantly
at set speed.
When Auto Fan is selected, indoor unit controller can operate in all speeds. The actual speed is set
according to the cool/heat load.
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