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Building Technologies Basic Documentation LMV27... CC1P7541en
10 Electronic air-fuel ratio control 17.12.2018
10.4 Multistage operation
This operating mode is only available when firing on oil. There is a choice of 2-stage and
3-stage operation. Hence, the burner’s output can be modulated via 2 or 3 stages.
Modulation is accomplished by adjustment of the air actuator and by switching the fuel
valves for adjusting the amount of fuel.
10.4.1 Definition of curves
Air-fuel ratio control is defined via the 2 or 3 static output points. To switch the valves on
and off, switch-on and switch-off points must be defined.
The following assignments apply:
Curve-
point
Meaning Valve
P0 Point of ignition (not approached in the operating position) V1
P1 Stage 1 V1
P2on Switch-on point stage 2. When the angle exceeds this point, the
fuel valve for the second stage is switched on
V1
P2_d Presetting of point P2 with no approach V1
P2 Stage 2 V2
P2of Switch-off point stage 2. When the angle falls below this point, the
fuel valve for the second stage is switched off
V2
P3on Switch-on point stage 3. When the angle exceeds this point, the
fuel valve for the third stage is switched on
V2
P3_d Presetting of point P3 with no approach V2
P3 Stage 3 V3
P3of Switch-off point stage 3. When the angle falls below this point, the
fuel valve for the third stage is switched off
V3
The actuator positions can be set with a resolution of 0.1°.
10.4.2 Traveling speed
The defined ramp speeds are used.
The setting also acts outside the running position.
The running speed of the actuators is fixed at 5 seconds for a positioning angle of 90°
for SQM33.4, SQM33.5, and SQN1.
The speed is 10 seconds for a positioning angle of 90° for SQM33.6.
The SQM33.7 requires 17 seconds for a positioning angle of 90°.
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