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Siemens Building Technologies
Basic Documentation LMV5...
CC1P7550en
HVAC Products
19 Addendum 4: LMV52... with O2 trim control and O2 module
13.08.2004
19.4.2
Load limitation with O
2
trim control
O
2
trim control can be deactivated below an adjustable load limit. This can be selected
separately for gas- and oil-firing.
Parameter:
O
2
CtrlThreshold
If the load drops below this limit, O
2
trim control will be deactivated and the system op-
erates along the parameterized ratio curves. If the load increases and exceeds the O
2
trim control threshold by 5 percentage points, the O
2
trim controller will be reinitialized.
19.4.3 Startup
With the parameter setting
Parameter:
O
2Ctrl
/Guard (O
2-guard
/ O
2-control
)
startup will be prevented until the O2 sensor has reached its operating temperature.
With the parameter setting
Parameter:
O
2
Ctrl/Guard (conAutoDeac)
starts the burner directly, O
2
trim control will be activated only when the operating tem-
perature has been reached and sensor test has been successful.
Also refer to section 19.4.4
Heating up the O2 sensor after «PowerOn»
.
19.4.4
Heating up the O
2
sensor after «PowerOn»
When the system or the O2 module is switched on for the first time, the cold O2 sensor
is slowly heated up until its operating temperature is reached.
When that temperature
is reached,
the sensor needs
another 10 minutes
to attain its maximum temperature.
With the parameter setting
Parameter:
O
2
Ctrl/Guard (O
2-guard
/ O
2-c
ontrol)
start prevention will take place until the O2 sensor has fully assumed its operating tem-
perature, followed by burner startup. O
2
trim control in the operating position will be ac-
tivated the moment the controller locking time has elapsed.
With parameter setting
Parameter:
O
2
Ctrl/Guard (conAutoDeac)
the burner will immediately be started up. O
2
trim control in the operating position will
only take place when the sensor has fully assumed its operating temperature and after
the sensor test has been successfully completed.
19.4.5
Initialization of O2 trim controller
The system is put into operation with the O
2
trim controller locked (safe ratio curve).
Locking time startup
commences when entering the operating phase. This locking
time is 10*
Tau low-fire
. On completion of this
locking time startup
, the dynamic re-
lease criterion of operation applies (refer to section 19.4.6 Behavior in the event of load
changes). When the above mentioned release criteria are satisfied, the O
2
trim control-
ler will be initialized. To reach the O
2
setpoint quicker, the theoretically required ma-
nipulated variable will be calculated from the currently acquired O
2
value, the O
2
ratio
value determined when making the setting, the O
2
setpoint and the standardized value.
That manipulated variable will then be increased by 3.7 % so that the resulting O
2
value will be somewhat higher than the O
2
setpoint. With an increase of 3.7 %, the re-
sulting O
2
value will be about 0.7 % higher than the O
2
setpoint. Fine-tuning to the O
2
setpoint will be ensured by the O
2
trim controller.