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Siemens Building Technologies Basic Documentation LMV5... CC1P7550en
HVAC Products 5 Fuel / air ratio control (FARC) 13.08.2004
When the burner is shut down, the actuators will be driven to their postpurge positions
in Phase 72.
For that purpose, a maximum time is available → position check.
The postpurge position is defined for all actuators and can be adjusted depending on
the type of fuel.
Parameters: LMV51... LMV52...
PostpurgePosAir x x
PostpurgePosGas x x
PostpurgePosOil x x
PostpurgePosAux x x
Aux2 x
Aux3 x
VSD x
The actuators‘ speed when traveling to the home, prepurge, ignition and postpurge po-
sitions can be parameterized.
Parameter: TmeNoFlame
Outside normal operation, all actuators travel at that speed.
When parameterizing the operating ramp, the speed of the slowest actuator must be
taken into consideration!
Modulating operation is possible for both types of fuel, gas and oil.
In the operating position, the dampers are driven to the defined fuel / air ratio curves in
accordance with the required output. Up to 15 curvepoints can be defined. The spacing
of the points (difference in output) can be freely selected.
The positions of the curvepoints are calculated by making linear interpolations.
To ensure correct fuel / air ratio control at any time, the actuators travel in steps of
maximum 1.2 seconds. This traveling time corresponds to a positioning angle of 3.6° at
an operating ramp of 30 seconds / 90 °.
For each of these steps, an individual speed is calculated for each actuator, so that all
actuators reach the required positions at the same time.
The → position check is always made between the individual steps when the actuators
do not move.
The speed of the fastest actuator can be parameterized.
If there is a curvepoint on the way to the next target on the curve, it will always be ap-
proached.
Parameter: OperatRampMod
When parameterizing the operating ramp, the speed of the slowest actuator must be
taken into consideration!
Postpurging
Actuator speed outside
normal operation
Note
Operating position
Modulating
Note
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