Hitachi RAS-(4-12)HNP(1)(E) - Abnormal Operation of Thermistor for the Indoor Unit Air Inlet Temperature (Air Inlet Thermistor)

8 Troubleshooting
240
SMGB0087 rev.0 - 12/2013
Alarm code
11
Abnormal operation of thermistor for the indoor unit air inlet temperature (air inlet thermistor)
- This alarm code is displayed when the thermistor is short-circuited (less than 0.24 kΩ) or cut (greater than 840 kΩ)
during the cooling process or the heating process. The system is automatically restarted when the fault is removed.
Is THM1 (inlet) connected to
I.U. PCB?
Connect it
No
Yes
Is the resistance of THM1
between 0.24kΩ and 840kΩ?
Faulty thermistor
No
Yes
Faulty PCB
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Faulty air inlet thermistor
Fault Check the resistance Replace the thermistor if faulty
Incorrect connection Check the connection
Repair the wiring and the
connections
Faulty PCB
Replace PCB and check the
operation
Replace PCB if faulty
N O T E
• This data is applicable to the following thermistors:
- Indoor unit discharge air temperature
- Indoor unit liquid refrigerant temperature
- Indoor unit air inlet temperature
- Outdoor temperature
- Outdoor unit evaporating temperature
- Indoor unit gas piping
Thermistor
resistance
(kΩ)
Air temperature (ºC)
Thermistor characteristics

Examples
Indoor unit air inlet
thermistor (THM1)
in case of 4-way
cassette
Inlet Air Thermistor
Inlet Air Thermistor
Inlet Air Thermistor