Viessmann VITODENS 050-W Installation And Service Instructions Manual page 54

Troubleshooting
Fault display
Fault code System character-
displayed istics
Fd Burner blocked
FF Burner blocked
Burner blocked
–––
Reset (reset burner control unit)
Press À and ¿ simultaneously.
––– is displayed.
If the fault has been removed, "¨"
extinguishes and the default display is
shown or further faults are displayed.
54
(cont.)
Cause
Burner control unit
fault
Burner control unit
fault
Communication
error between
burner control unit
and programming
unit
Checking the programming unit soft-
ware version
Press À and
Measures
Check ignition electrodes
and connecting cables.
Check whether a strong
interference (EMC) field
exists near the appliance.
Press "Reset" (see
page 54).
Replace control unit if
fault persists.
Check ignition electrodes
and connecting cables.
Check whether a strong
interference (EMC) field
exists near the appliance.
Press "Reset" (see
page 54).
Replace control unit if
fault persists.
Check the connecting
lead.
Press "Reset" (see
page 54).
Replace burner control
unit or programming unit
if the fault persists.
simultaneously.