Increasing The Manipulated Variable In Case Of Cox Signal (O2Modoffset, Formerly O2Offset) - Siemens LMV52 series User Manual

Building Technologies Division
4.6 Increasing the manipulated variable in case of
COx signal (O2ModOffset, formerly O2Offset)
If the COx maximum value is exceeded, the contact is closed (see chapter Hardware
prerequisite / Connection diagram).
In order to prevent this, the user can use parameters to set an offset for the O2 value in
the event that a COx signal occurs.
The next increase can only be made once the locking time has elapsed (waiting time of
2 x Tau current load).
There will be no increase of the O2 value when O2 trim control is deactivated.
The parameter defines the increase of the O2 value in %.
Example:
O2ModOffset = 0.8%, O2 actual value 1.4%  In the event of COx signal, the O2 value
reached will be 2.2%.
Actual O2 value
O2 setpoint
Figure 1: Increasing the manipulated variable in the case of a COx signal
Parameter Gas: O2ModOffset (0..5%)
Oil: O2ModOffset (0..5%)
Fault response:
The test time Time COx Alarm is started at the same time as the O2 value is increased.
Once the test time is complete, and if the COx signal is still present in spite of
increasing the air supply, a fault response takes place in the form of a safety shutdown
with new startup and, depending on the O2 Control repetition counter, lockout is
performed.
Parameter Time COx Alarm (0..600 s)
User Manual LMV5...
COx supervision and control
2.2%
1.4%
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CC1A7550.5en
07.07.2015