Viessmann VITODENS 200-W Service Instructions Manual page 112

Troubleshooting
Repairs
(cont.)
20
10
8
6
4
2
1
0.8
0.6
0.4
10 30 50 70 90 110
Temperature in °C
Checking the temperature limiter
Check the temperature limiter, if the burner control unit cannot be reset after a fault
shutdown, although the boiler water temperature is below approx. 75 °C.
112
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 the actual values with the
curve.
3. Replace the sensor in 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.