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133
Control unit
message
System characteristics
Cause
Measures
F.468
Burner in a fault state
Ionisation current too high
during calibration
Check gap between ionisation
electrode and burner gauze as-
sembly. See page 79.
Heat generator installation
and service instructions
Check whether there is a lot of
dust in the ventilation air (e.g. from
construction work).
Note
Deposits on the electrodes indicate
foreign bodies in the ventilation 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.
Reset device.
F.471
No heat demand
System pressure sensor
not available
Check system pressure sensor.
F.472
Control mode without elec-
tricity meter data
Communication error,
electricity meter
■
Check CAN bus connection to
the external electricity meter (ob-
serve polarity and correct if nec-
essary).
■
Check setting of CAN bus termi-
nator switch: See page 48.
■
Disconnect electricity meter from
power supply then reconnect.
F.473
No heat demand
Heat management unit
communication error
Check connecting cable between
burner control unit and heat man-
agement unit.
F.474
Burner in a fault state
Error in scheduled pro-
gram run monitoring
Reset device.
F.475/42F1
No power generation
Air in the system separa-
tion circuit or system sep-
aration circuit not filled
Fill and vent the system separation
circuit.
Note
The message can
only
be cleared
on the programming unit of the fuel
cell module.
F.517
Control mode, remote control
unit not functioning
Communication error,
Vitotrol wired remote con-
trol
Check remote control unit connect-
ing cable and setting.
F.523/18F0
No power generation
Fault, reformer burner ig-
nition
Reset the fault once.
If the fault recurs, notify Viessmann
Technical Service.
Troubleshooting
Fault messages on the gas condensing…
(cont.)
5853335
Diagnosis