Hitachi UTOPIA RAS-4HVRP2E - Page 280

10 Troubleshooting
Troubleshooting procedure
SMGB0136 rev.0 - 07/2021
278
Alarm code
24
Abnormality of Thermistor for Evaporating Temperature during Heating Operation (Outdoor Unit
Evaporating Thermistor)
• Thealarmcodeisashedonthe7-segmentdisplayoftheoutdoorunit.
• The alarm code is displayed on the wired controller of the indoor unit.
Thisalarmcodeisdisplayedwhenashortcircuit(0.2kΩorless)ordisconnection(500kΩormore)ofthethermistoris
detected during heating or cooling operation.
Phenomenon Cause
Check Item
Action (Turn OFF
Main Switch)
No
No
Yes
Yes
Is thermistor connected
to THM8 of Outdoor Unit
PCB?
Is resistance of thermistor
between0.2kΩand500kΩ?
Connect it
Failure of Thermistor
Failure of O.U. PCB
Failure of Thermistor
for Evaporating
Temperature during
Heating
Failure
Incorrect Connection
Check resistance
Check wiring to Outdoor Unit
PCB
Replace thermistor if faulty
Repair wiring and connection
Replace Outdoor Unit PCB if
faulty
Replace Outdoor Unit PCB and
check operation
Failure of Outdoor Unit PCB
Thermistor
Resistance
R
T
[kΩ]
Temperature T (°C)
Thermistor Characteristics