Check Fixed High Limit; Check Flue Gas Temperature Sensor - Viessmann VITODENS 100-W WB1B Series Installation And Service Instructions Manual

Troubleshooting
Correction
(continued)

Check fixed high limit

Fig. 73

Check flue gas temperature sensor

Fig. 74
70
If the burner control unit cannot be reset after a fault shutdown (F2), even
though the boiler water temperature is below approx. 203° F / 95° C, check
the fixed high limit.
Temperature
1. Pull the leads from fixed high limit
A.
2. Check the continuity of the fixed
high limit with a multimeter.
3. Remove faulty fixed high limit.
4. Coat the replacement fixed high
limit with heat conducting paste
and install.
5. To reset, refer to page 66.
1. Pull the leads from flue gas
temperature sensor A.
2. Check the sensor resistance and
compare it with the curve.
3. Replace the sensor in case of
severe deviation.