Viessmann VITODENS 300 Service Instructions Manual page 13

Further details regarding the individual steps
Yes
Differential pres-
sure sensor
enables start
(0.75 V across
terminals X8.5
and X8.6)
Yes
Ignition
Yes
Gas combination
valve opens
Yes
Ionisation cur-
rent builds
(higher than
5 µA)
Symbol A
Yes
Operational bur-
ner
Initial start-up, inspection, maintenance
After approx.
51 seconds
No
Fault
E6
Fault
No
F4
Fault
No
F4
Fault
No
F4
Stops below set
boiler tempera-
ture and restarts
(cont.)
Check fan cables
and fan plug-in
connections,
check fan
Check the ignition
module (control
voltage 230 V
across plugs X2.1
and X2.2)
Check the gas
train (control vol-
tage 230 V) and
gas supply pres-
sure
Check the ionisa-
tion current, the
electrode adjust-
ment and the gas
pipe for airlocks
Check flue gas
system for sound-
ness (flue gas
recirculation),
check gas flow
pressure
13