Viessmann Vitodens 300 Service Instructions Manual page 90

Troubleshooting
Repairs
(cont.)
Checking the thermocouple
Checking and replacing pressure differential sensor
Check the sensor in case of fault messages concerning the differential pressure
sensor:
&
Correct installation
&
Electrical connection
&
Correct position of the O-rings inside the adaptor
&
Are the test nipples closed with plugs?
Replace the sensor if fault messages persist.
90
If the burner control unit cannot be
reset after a fault shutdown, although
the boiler water temperature is below
approx. 90 °C:
&
Pull the leads from
thermocouple A.
&
Check the continuity of the thermo-
couple with a multimeter.
&
Remove the faulty thermocouple.
&
Install a new thermocouple.
&
After commissioning, press reset
button E on the control unit.