Hitachi RAS-(4-12)HNP(1)(E) - Abnormal Operation of the Thermistor for the Indoor Unit Heat Exchanger Liquid Pipe Temperature (Freeze Protection Thermistor)

8 Troubleshooting
242
SMGB0087 rev.0 - 12/2013
Alarm code
13
Abnormal operation of the thermistor for the indoor unit heat exchanger liquid pipe temperature
(freeze protection 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 THM3 (freeze protection con-
nected to I.U. of PCB?
Connect it
No
Yes
Is the resistance of THM3
between 0.24kΩ and 840kΩ?
Faulty thermistor
No
Yes
Faulty PCB
Refer to the thermistor
resistance in Alarm 11
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Faulty freeze protection
thermistor
Fault Check the resistance Replace the thermistor if faulty
Incorrect connection Check the connection
Repair the wiring and
connections
Faulty PCB
Replace PCB and check the
operation
Replace PCB if faulty
Thermistor
resistance
(kΩ)
Air temperature (ºC)
Thermistor characteristics

Examples
Freeze protection thermis-
tor (THM3) in case of 4-way
cassette
Liquid Pipe Thermistor
(THM3)
Liquid Pipe Thermistor
(Freeze Protection)
Liquid Pipe Thermistor
(Freeze Protection)