77
Displayed fault
code
System characteristics
Cause
Measures
464
Burner in a fault state
Ionisation current too low
during calibration. Differ-
ential compared to previ-
ous value not plausible.
■
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.
467
Burner in a fault state
Gas supply insufficient
during calibration. Conta-
minated or insufficiently
sized gas line.
■
Test static gas pressure and gas
flow pressure.
■
Check that on-site gas line and
gas flow switch are correctly
sized.
■
Visually inspect gas solenoid
valve inlet and strainer on the in-
let side for contamination.
Reset the appliance.
Note
Contamination from a brazed gas
line, for example, can block up the
gas solenoid valve strainer on the
inlet side.
Troubleshooting
Fault messages
(cont.)
6167586
Diagnosis
