Viessmann B0KA Installation And Service Instructions Manual page 69

Fault messages
(cont.)
Displayed fault System characteristics
code
464 Burner in a fault state
467 Burner in a fault state
Cause
Ionisation current too low
during calibration. Differ-
ential compared to previ-
ous value not plausible.
Gas supply insufficient
during calibration. Conta-
minated or insufficiently
sized gas line.
Troubleshooting
Measures
Check ionisation electrode and
■
connecting cable. Check plug-in
connections for loose contacts.
Check whether there is a lot of
■
dust in the ventilation air (e.g.
from construction work).
Check flue system. Remove flue
■
gas recirculation if required.
Check system for condensate
■
backup.
Reset the appliance.
Note
To prevent water damage, detach
fan unit before removing the burn-
er.
If the fault is constantly present, re-
place the HBMU heat management
unit: See chapter "Replacing the
HBMU heat management unit."
Note
Deposits on the electrodes indicate
foreign bodies in the combustion
air. Check the installation room and
flue system for causes of the de-
posits. For example: Laundry de-
tergents, cleaning agents, toilet-
ries, deposits in the ventilation air
supply (chimney).
If burner gauze assembly and ioni-
sation electrode have been re-
placed, also clean fan unit, gas/air
channel and Venturi extension.
Test static gas pressure and gas
■
flow pressure.
Check that on-site gas line and
■
gas flow switch are correctly
sized.
Visually inspect the gas solenoid
■
valve inlet and the inlet strainer
for dirt.
Reset the appliance.
Note
Contamination from a brazed gas
line, for example, can block up the
gas solenoid valve inlet strainer.
69