46
6 Commissioning
6.6.1.5 Dynamic Probe Test
The VMS monitors the measured O
2
value for changes during operation. If a fluctuation no
higher than 0.2 O
2
vol.% is detected over a period of 10 minutes, a state of excess air is en-
forced by changing the fuel/air mixture. If there is still no change in the actual O
2
value after 1
minute, the test is repeated with more excess air. If this does not lead to a change in the actual
value, the test is performed a third time with even more excess air. If no change has occurred
in the actual O
2
value at this point, the control unit deactivates itself and displays a warning
on the screen. Thereafter the control unit's output (correction input) corresponds to "Base val-
ue without control”.
NOTICE
The O
2
optimisation fault messages do not affect burner or combustion functions.
6.6.1.6 Probe Blockage
Blockages in the probe can cause the measured value to increase slowly but steadily, in such
a way that the dynamic probe test is not triggered. The main processor monitors whether the
actual O
2
value drops by more than 0.2 vol. % O
2
at least once within 15 minutes. If this is not
the case, then a dynamic test is triggered.
NOTICE
O
2
optimisation fault messages have no effect on the burner's function or that of the combus-
tion system. They only notify that:
- O
2
optimisation was deactivated.
- Note error status and firing rate value.
If desired, it is also possible to have the burner shut down on ’Air shortage’ faults via parameter
897.
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