Viessmann B2TF Installation And Service Instructions Manual page 90

Troubleshooting
Fault messages
(cont.)
Displayed fault System characteristics
code
F.425 System in control mode, cal-
culation out of operation
F.430 Control mode operation in
line with set values of heat
generator
F.446 Burner in a fault state
F.447, F.448 Burner in a fault state
F.449, F.450, Burner in a fault state
F.451, F.452
F.453 Burner in a fault state
F.454 Burner in a fault state
F.455 Burner in a fault state
F.456 Burner in a fault state
F.457 Burner in a fault state
90
Cause
Time synchronisation
failed
Communication error,
gateway
Deviation, heat generator
flow temperature sensor/
high limit safety cut-out
Deviation, ionisation volt-
age signal
Error in scheduled pro-
gram run monitoring
Synchronisation error, se-
quence
Incorrect software version
Error in program run moni-
toring
Error in program run moni-
toring
Fan sluggish or blocked.
Measures
Set the time. If external time is
used, check parameters 1504 and
508.
Check gateway module connecting
cable and power supply.
Check the flow temperature sen-
sor/high limit safety cut-out.
Check plug-in connection and lead
to sensor.
Reset the appliance.
Replace BCU burner control unit:
See page 100.
Reset the appliance.
Reset the appliance. If fault recurs,
replace BCU burner control unit:
See page 100.
Reset the appliance. If fault recurs,
replace BCU burner control unit:
See page 100.
Flash the correct software version
for the BCU burner control unit.
Reset the appliance. If fault recurs,
replace BCU burner control unit:
See page 100.
Reset the appliance. If fault recurs,
replace BCU burner control unit:
See page 100.
Reset the appliance.
Check fan for sluggishness. In the
case of severe contamination or
grinding noises, replace fan unit.