25
System char-
acteristics
Cause
Action
The boiler will
not start
No voltage
Check the MCB/fuse and power cable
connections.
Check the setting of the switch on the
control unit.
Boiler water tempera-
ture too high
Wait until the boiler water temperature
has dropped by approx. 20 K.
The high limit safety
cut-out has responded
Press the reset button on the control
unit.
The flue gas monitor-
ing device (if installed)
has responded
Wait approx. 17 min;
if the boiler then starts automatically,
check the flue pipe and the chimney.
If the boiler does
not
start automatically,
check the flue gas monitoring device (see
page 23).
Strapping plug CN2 is
missing at the burner
control unit
Retrofit strapping plug CN2 or a flue gas
monitoring sensor.
Burner control
unit enters a
fault state
No gas available (air in
the gas line)
Press the reset button at the burner con-
trol unit.
The pilot burner will not
start
Check the ignition electrode (see
page 20).
Check the gas supply.
Ionisation current too
low or cable break
Check the ionisation current (min. 3 µA
when main burner is lit) (see page 17).
Control unit faults:
Boiler control unit service instruc-
tions
Troubleshooting
Diagnosis
5692 704 GB
