Viessmann VITODENS 300 WB3A, Service Instructions Manual

Page: 106 / 148

Checking the thermocouple
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.
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.
Repairs
(cont.)
90
Troubleshooting
56
92
550
GB