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Building Technologies Basic documentation LMV37.4... CC1P7546en
HVAC Products 9 Electronic air-fuel ratio control 01.12.2009
9.4.3 Adjustment of output
When the output increases, the system moves from the curvepoint of stage 1 (P1) to the
switch-on point of stage 2 (P2on). If the switch-on point is exceeded, the valve for the
second stage is switched on. Then, the system moves to the curvepoint for stage 2 (P2).
When the output decreases, the system moves from the curvepoint of stage 2 (P2) to
the switch-off point of stage 2 (P2of). If this point is crossed, the valve for the second
stage is switched off. Then, the system moves to the curvepoint for stage 1 (P1).
In 3-stage operation, the output between stage 2 and stage 3 is adjusted analogously to
2-stage operation. As static outputs, only
P1, P2 and P3 can be approached.
The switch-on and switch-off points are crossed only when changes between stages
take place. The running speeds are fixed. Depending on the positioning angles to be
covered, air actuator and VSD do not reach the operating or switch-on / switch-off points
at the same time. The valves are switched on / off only after both actuators have
reached their correct positions.
When parameterizing the curves, the switch-on points can also be approached in a sta-
tionary manner. In addition, when setting the curve via
P2_d (P3_d), curvepoint P2 (P3)
can be readjusted without traveling to it. In that case, the system is at the respective
switch-on point. This procedure is used to cut the operating time if there is shortage of
air.
Figure 40: Adjustment of output
9.4.4 Changing to the running position
The burner is ignited at ignition position
P0. When entering running phase 60, the actua-
tors are driven from ignition position
P0 to the running position of stage 1 (P1) at the re-
spective running speed.
9.4.5 Running position
In the running position, the burner’s output can be adjusted between running positions
P1 and P2 or P3 in accordance with the load controller’s presetting, as described in
subsection 9.4.3 Adjustment of output. Ignition position
P0 does not approached any-
more. It can only be reached via curve adjustment.
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