Viessmann Vitocrossal CRU 800 Service Instructions For Contractors page 44

Troubleshooting
Faults without fault display
Fault
Flame tears off during op-
eration
Flue gas temperature too
high
44
(cont.)
Cause of fault
Intake strainer of gas train
soiled
Excessive gas throughput
Measure
Remove flange. Clean strainer. See page 26.
Adjust gas throughput in accordance with the rated
boiler heating output. Checking the condition of the
heating surfaces. Clean if necessary.