Viessmann Vitopend 100-W - There is no hot water

37
Display Action
Control unit issues
a heat demand
No
Increase set value
and ensure heat is
drawn off
Yes
Ignition
No
Fault "F4" Check the ignition
module connec-
tion
Yes
Gas train opens
No
Fault "F4" Check the gas
train (control volt-
age 230 V) and
gas supply pres-
sure
Yes
Ionisation current
builds (higher than
2 µA)
Symbol
A
No
Fault "F4" Check the ionisa-
tion current, check
the electrode ad-
justment and the
gas line for air-
locks.
Yes
Burner in opera-
tion
No
Shuts down below
the set boiler water
temperature and
restarts immediate-
ly
Check the flue sys-
tem for tightness
(flue gas recircula-
tion); check the
gas flow pressure
Troubleshooting
Function sequence and possible faults
5848 649 GB
Service