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Building Technologies Basic documentation LMV37.4... CC1P7546en
HVAC Products 9 Electronic air-fuel ratio control 01.12.2009
9.4 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 regulated via 2 or 3-stages. Modu-
lation is accomplished by adjustment of the air actuator or of VSD and by switching the
fuel valves for changing the amount of fuel delivered.
9.4.1 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 assignment is used:
Curve-
point
Meaning Valve
P0 Point of ignition (does not approached in the running position) V1
P1 Stage 1 V1
P2on Switch-on point stage 2. When this point is exceeded, 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 this point is crossed, the fuel valve
for the second stage is switched off
V2
P3on Switch-on point stage 3. When this point is exceeded, 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 this point is crossed, the fuel valve
for the third stage is switched off
V3
The actuator positions can be set with a resolution of 0.1°, the speeds with a resolution
of 0.1%.
9.4.2 Running speed
The air actuator or the VSD is operated like outside the running position. The defined
ramp speeds are used.
The running speed of the actuators is fixed at 5 seconds for a positioning angle of 90°.
For increasing or degrading the speed, the speed of the VSD can be separated ad-
justed.
No. Parameter
522 Ramp up
523 Ramp down
The setting also acts outside the operating position.
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