Viessmann Vitovalor PT2 Installation And Service Instructions For Contractors page 122

Troubleshooting
Fault messages on the gas condensing...
Control unit System characteristics
message
F.349 Control mode
Burner is operating with a
limited modulation range.
F.350 Burner in a fault state
F.351 Burner in a fault state
F.352 Burner in a fault state
F.353 Burner locked out
F.354 Burner in a fault state
F.355 Burner in a fault state
122
(cont.)
Cause
Air mass flow rate in fan
unit has not been correctly
recognised.
Ionisation voltage lies out-
side the permissible range
Ionisation current lies out-
side the permissible range
CO limit within appliance
exceeded
Insufficient gas supply,
burner output reduced
Gas modulation valve tol-
erance outside permissi-
ble range
Analogue signal reference
check: Flame signal is al-
ready present at burner
start.
Measures
Check mass flow sensor on the fan
unit. Check flue system for flue gas
congestion.
Check ionisation electrode and
connecting cable.
Reset device.
Check ionisation electrode and
connecting cable.
Reset device.
Check entire flue gas path for the
following:
Flue gas recirculation
■
Leak
■
Flue gas congestion caused by
■
water sack (if the flue gas system
is not steep enough)
Constriction
■
Blockage
■
Repair flue system if necessary.
Reset device.
Check the gas supply.
Optically check input-side screen
in the gas train for contamination.
Reset device.
Check connecting cable for gas
train for damage.
Check gas train.
Check the flue system for conges-
tion, constriction.
Reset device.
Check if condensate banked.
Note
To prevent water damage, detach
fan unit before removing the burn-
er.
Reset device.