12-4
CONTROL SYSTEM
SM OU12HP 2-E.2 GB
12.2.10 Base Heater
Heating element designed to melt any ice that is accumulated on the outdoor unit base during
low heating operation.
12.2.11 Cranck case Heater
Heating element designed to heat up the compressor oil cranck case during low heating
operation.
12.2.12 Internal coil heater
Only exists in 6HP unit. The compressor is equiped with built-in heating coils designed to
heatup the compressor oil cranck case during low heating operation.
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 reduced below the threshold.
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
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
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.
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