Hitachi UTOPIA RAS-4HVRP2E - Page 277

10 Troubleshooting
Troubleshooting procedure
SMGB0136 rev.0 - 07/2021
275
10
Alarm code
20
Abnormality of Discharge Gas 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(0.9kΩorless)ordisconnection(5946kΩormore)ofthethermistoris
detected during a heating or cooling operation.
Phenomenon
Cause
Check Item
Action (Turn OFF
Main Switch)
No
No
Yes
Yes
Is thermistor connected to THM9
of Outdoor Unit PCB?
Is resistance of THM9 within
range shown in “Thermistor
Characteristics”?
Connect it
Failure of Thermistor
Failure of O.U. PCB
Thermistor
Resistance
R
T
[kΩ]
Temperature T (°C)
Thermistor Characteristics
Failure of Thermistor for
Discharge Gas Temp.
on Top of Compressor
Failure
Incorrect Connection
Check resistance
Check wiring to Outdoor Unit
PCB
Replace Outdoor Unit PCB and
check operation
Replace thermistor if faulty
Repair wiring and connection
Replace Outdoor Unit PCB if
faulty
Failure of Outdoor Unit PCB