Check Flue Gas Temperature Sensor - Viessmann VITOLADENS 300-W Installation And Service Instructions Manual

Troubleshooting
Repair
(cont.)
20
10
8
6
4
2
1
0.8
0.6
0.4
10 30 50 70 90 110
Temperature in °C
Sensor type: NTC 10 kΩ

Check flue gas temperature sensor

The flue gas temperature sensor locks
out the boiler when the permissible flue
gas temperature is exceeded. Reset
interlock after flue system has cooled
down by pressing reset button "E".
106
1. ■ Boiler water temperature sensor:
Pull the leads from boiler water
temperature sensor A and check
the resistance.
■ Cylinder temperature sensor: Pull
plug % from the cable harness at
the control unit and check the
resistance.
■ Flow temperature sensor: Pull plug
"X3" from the control unit and
check the resistance across termi-
nals "X3.4" and "X3.5".
2. Check the sensor resistance and
compare it with the curve.
3. Replace the sensor in the case of
severe deviation.
Danger
The boiler water temperature
sensor is immersed in the
heating water (risk of scald-
ing).
Drain the boiler before replac-
ing the sensor.