Fault Messages On The Display - Viessmann VITODENS 100-W Installation And Service Instructions Manual

Troubleshooting
Function sequence and possible faults
Yes
Ionisation current
builds (higher than
2 µA)
Symbol A
Yes
Burner in opera-
tion

Fault messages on the display

32
No
Fault F4
No
Stops below the set
boiler water tem-
perature and re-
starts immediately
f 2
(cont.)
Faults are indicated by a flashing fault
code with fault symbol "U" on the dis-
play.
For fault code explanations see the fol-
lowing table.
■ Flashing fault symbol "U": Reset with
"U RESET" (see page 36) after cor-
recting the fault.
■ Constantly displayed fault symbol "U":
Automatic reset after the fault has
been remedied.
Check the ionisa-
tion current, check
the electrode ad-
justment, check
the condensate
drain and the gas
line for airlocks
Check the flue sys-
tem for tightness
(flue gas recircula-
tion), check the
condensate drain,
check the gas flow
pressure