70
Displayed fault
code
System characteristics
Cause
Measures
345
Burner locked out, automatic
enabling after appliance cool-
down. Independent restart
Temperature limiter has
responded.
■
Ensure adequate heat transfer.
■
Check heating system fill level.
■
Check pre-charge pressure in di-
aphragm expansion vessel. Ad-
just to required system pressure.
■
Check whether flow rate is suffi-
cient (circulation pump).
■
Check function of 3-way diverter
valve. Vent the system.
If the fault occurs during DHW
heating: Check DHW cylinder or
plate heat exchanger for contami-
nation and scaling.
346
Burner in a fault state
Ionisation current calibra-
tion error
■
Check the gas supply pressure.
■
Check gas solenoid valve strain-
er on the inlet side for contami-
nation.
■
Check ionisation electrode for
contamination.
■
Check flue system. Remove flue
gas recirculation if required.
■
Check the condensate drain
(condensate blockage).
Reset the appliance.
348
Burner in a fault state
Gas modulation valve
If several heat generators are con-
nected to a common flue system:
Check whether
"Multiple connec-
tions"
is set in the commissioning
assistant.
Check the flue system for unre-
stricted flow.
If fault remains, replace gas fan
unit.
349
Burner in a fault state
Air mass rate flow not de-
tected correctly in fan unit.
■
Check for dust contamination in
the supply air.
■
Check burner gauze assembly
for contamination.
Reset the appliance. If the fault oc-
curs repeatedly, replace the gas
fan unit.
350, 351
Burner in a fault state
Ionisation current lies out-
side the permissible range
Replace the HBMU heat manage-
ment unit. See chapter "Replacing
the HBMU heat management unit".
352
Burner in a fault state
Combustion CO limit ex-
ceeded
Check entire flue gas path for the
following:
■
Leaks
■
Flue gas back pressure caused
by water pocket (if flue system
fall is insufficient)
■
Constrictions
■
Blockages
Repair flue system if necessary.
Reset the appliance.
Troubleshooting
Fault messages
(cont.)
6167586
Diagnosis
