Important
When connecting a Room Unit/Control Unit to the boiler, the code
“254” is always shown in the event of a fault.. Read the fault code
shown on the boiler display.
8 Troubleshooting
A.02
.06
Low pressure in heating circuit
Check the installation pressure and restore
Check the expansion vessel pressure
Check for boiler/installation leaks
A.02
.36
Functional device disconnected
COMMUNICATION FAULT
Start the auto-detect function (parameter AD)
Check the devices connected to contact X9
A.02
.37
Passive functional device disconnected
COMMUNICATION FAULT
Start the auto-detect function (parameter AD)
Check the devices connected to contact X9
A.02
.45
Connection error
COMMUNICATION FAULT
Start the auto-detect function (parameter AD))
A.02
.46
Device priority error
COMMUNICATION FAULT
Start the auto-detect function (parameter AD))
A.02
.48
Unit function configuration error
ELECTRICAL CONNECTION ERROR
Start the auto-detect function (parameter AD))
Check electrical connections of external devices
A.02
.49
Failed node initialisation
ELECTRICAL CONNECTION ERROR
Start the auto-detect function (parameter AD))
Check electrical connections of external devices
A.02
.54
Open Therm bus power supply error
Check the devices connected to contact X17 -
Terminal board M2 (7-8)
A.02
.55
Incorrect or missing serial number
Contact the Service Network
A.02
.76
Internal memory reserved for full customisation of set
tings.
No further changes can be made
Contact the Service Network
Tab.13 List of warnings
DISPLAY
DESCRIPTION OF WARNINGS BEFORE A FAULT
IS DETECTED
CAUSE – Check/Solution
Group
code
Specific
code
A.00
.28
Solar temperature sensor is either removed or
measures a temperature below range
Check the solar temperature sensor wiring. Re
place the sensor if necessary. In case of removal
of the solar tank, set the parameter DP150=1.
A.00
.29
Solar temperature sensor is either shorted or
measures a temperature above range
Check the solar temperature sensor wiring. Re
place the sensor if necessary.
A.00
.34
Outdoor temperature sensor expected but not detec
ted
OUTDOOR SENSOR NOT DETECTED
Enter the correct value of the parameter AP091
Connect the outdoor sensor
Outdoor sensor is not connected correctly
24
400 Combi 2
