73
Displayed fault
code
System characteristics Cause Measures
353 Shutdown with restart if de-
mand exists
Insufficient gas supply,
burner output reduced
Check the gas supply.
Optically check input-side screen
in the gas solenoid valve for con-
tamination.
Reset the appliance.
354 Burner in a fault state Gas modulation valve tol-
erance outside permissi-
ble range
Replace gas fan unit.
355 Burner in a fault state Analogue signal reference
check: Flame signal is al-
ready present at burner
start.
Replace the HBMU heat manage-
ment unit. See chapter "Replacing
the HBMU heat management unit".
357 Burner in a fault state Insufficient gas supply
■
Check that the main gas valve
and the gas shut-off valve are
open.
■
Test static gas pressure and gas
flow pressure.
■
Check that on-site gas line and
gas flow switch are correctly
sized.
Note
If the building pressure regulator
has a leak, you may notice rising
pressure when the burner is idle.
When the system is restarted,
the gas flow switch may trip.
■
If the static pressure doesn't
drop, check cable to the fan unit.
Check that the coil resistance at
the fuel valve is approx. 4 k
Ω
(plug 35).
■
Check the ignition electrode for
damaged insulation.
Reset the appliance.
359 Burner in a fault state No ignition spark
■
Check whether the ignition elec-
trode insulation is damaged.
■
Check for a voltage of 230 V∼ at
the ignition module during the ig-
nition phase. If not, replace the
HBMU heat management unit.
■
If 230 V~ is present at the igni-
tion module but there is still a
fault, replace the ignition module.
■
Check connection cables and
leads from ignition module and
ignition electrode.
Reset the appliance.
Troubleshooting
Fault messages (cont.)
6167586
Diagnosis
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