Viessmann Vitodens 222-F Installation And Service Instructions For Contractors page 96

Troubleshooting
Fault codes
(cont.)
Fault code dis- System characteristics
played
E4 Burner blocked
E5 Burner blocked or in a fault
state
E7 Burner in a fault state
E8 Burner in a fault state
96
Cause
24 V power supply fault
Flame amplifier fault
Ionisation current too low
during calibration
Ionisation current lies out-
side the permissible range
Measures
Replace control unit.
Press reset button R.
Replace control unit if fault is per-
manent.
Check the ionisation electrode and
connecting lead (see page 43).
Check plug-in connections for
loose contacts.
Check flue system; remove flue
gas recirculation if required.
Press reset button R.
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 deter-
gents, cleaning agents, toiletries,
deposits in the ventilation air sup-
ply (chimney).
If burner gauze assembly and ioni-
sation electrode have been re-
placed, also clean fan unit, gas/air
channel and Venturi extension.
Check gas supply (gas pressure
and gas flow switch), gas train and
connecting cable.
Check assignment of gas type (see
page 35).
Check ionisation electrode:
Distance to burner gauze assem-
■
bly (see page 43)
Electrode contaminated
■
Press reset button R.