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Building Technologies Basic documentation LMV37.4... CC1P7546en
HVAC Products 9 Electronic air-fuel ratio control 01.12.2009
9.3 Modulating operation
In modulating mode, it is possible to operate 2 actuators and one VSD. The burner‘s
output can be regulated between 20.0% (low-fire) and 100.0% (high-fire) in increments
of 0.1%. Since the actuators are never allowed to operate simultaneously, the output is
increased in small steps of 1%. In the case of an operating ramp of 20% after 100% in
32 seconds, this represents one step in 400 ms. Within such an output step, the air ac-
tuator is operated in the first 200 ms and the VSD, and the fuel actuator in the second
200 ms.
9.3.1 Definition of curves
The air-fuel ratio curves are defined by 10 curvepoints that are firmly distributed across
the output range.
The following assignment applies:
Curvepoint Output Meaning
P0 10% Point of ignition, is not approached in the running position
P1 20% Low-fire
P2 30%
P3 40%
P4 50%
P5 60%
P6 70%
P7 80%
P8 90%
P9 100% high-fire
The actuator positions can be set with a resolution of 0.1°.
Between the curvepoints, the positions are interpolated in a linear manner.
Fuel
Air
VSD
100
90
80
70
60
50
40
30
20
10
0
P0 10 % Ignition point
P1 20 % Low-fire
P2 30 %
P3 40 %
P4 50 %
P5 60 %
P6 70 %
P7 80 %
P8 90 %
P9 100 % High-fire
Bild 385e/1109
Figure 38: Definition of curves
No. Parameter
401 Ratio control curves fuel actuator (only curve setting)
402 Ratio control curves air actuator (only curve setting)
403 Ratio control curves VSD (only curve setting)
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