44
7 O
2
Trim
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 value without control”.
NOTICE
The O
2
optimisation fault messages do not affect burner or combustion functions.
7.6 Control Strategy
These trim strategies have been developed and optimised especially for the conditions obtain-
ing in combustion installations:
– Frequent changes in the burner-firing rate
– Long dead times.
During burner start-up, O
2
trim remains in standby, until it is ensured that plausible measured
O
2
values are displayed.
Factory setting: 90 seconds after ignition - parameter 904 (adjustable).
The "neutral value” is output during standby.
The neutral value depends on the selected correction mode;
e.g. in the case of -50% to +50%, the correction value (neutral value) output is 500; in the case
of -30% to +70%, the output value is 300.
NOTICE
The neutral value corresponds to the base settings of the ETAMATIC OEM without control.
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