Viessmann Vitodens 050-W Installation And Service Instructions Manual page 65

Fault messages
(cont.)
Displayed fault System characteristics
code
373 Burner in a fault state
374 Burner restarts
Cause
Heat transfer too low dur-
ing calibration
Temperature limiter has
shut down.
Preparation for ionisation
current calibration: Stabili-
sation conditions for pre-
calibration not met.
Troubleshooting
Measures
Ensure adequate heat transfer.
■
Check circulation pump for faults,
■
scale or blockages.
Check function of 3-way diverter
■
valve. Vent the system.
Check function of flow sensor.
■
Reset the appliance.
Check ionisation electrode and
■
connecting cable.
Check plug-in connections for
■
loose contacts. Check the flue
system. Remove flue gas recir-
culation if necessary.
Check system for condensate
■
backup. Visually check gas sole-
noid valve inlet and inlet strainer
for contamination.
Note
To prevent water damage, de-
tach fan unit before removing the
burner.
Deposits on the electrodes indi-
cate foreign bodies in the com-
bustion air. Check the installation
room and flue system for causes
of the deposits. For example:
Laundry detergents, cleaning
agents, toiletries, deposits in the
ventilation air supply (chimney).
If burner gauze assembly and
ionisation electrode have been
replaced, also clean fan unit,
gas/air channel and Venturi ex-
tension.
Reset the appliance.
65