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Building Technologies
Basic Documentation LMV27...
CC1P7541en
10 Electronic air-fuel ratio control
17.12.2018
10.3 Modulating
operation
In modulating mode, it is possible to operate 2 actuators. 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 1 step in 400 ms. Within such an output step, the air actuator is operated
in the first 200 ms, and the fuel actuator in the second 200 ms.
10.3.1 Definition
of
curves
The air-fuel ratio curves are defined by 10 curvepoints that are fixed and distributed
across the output range.
The following assignment applies:
Curvepoint
Output
Meaning
P0
10%
Point of ignition, not approached in the operating 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
100
90
80
70
60
50
40
30
20
10
0
P
0 10
%
poi
nt
of
ign
iti
on
P
1
2
0 %
lo
w
-fi
re
P2 3
0
%
P3 4
0
%
P4 5
0
%
P5 6
0
%
P6 7
0
%
P7 8
0
%
P8 9
0
%
P
9 100
%
hi
gh
-f
ire
Figure 63: Definition of curves
No. Parameter
401
Ratio control curve fuel actuator (only curve setting)
402
Ratio control curve air actuator (only curve setting)