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Siemens Building Technologies Basic Documentation LMV5... CC1P7550en
HVAC Products 5 Fuel / air ratio control (FARC) 13.08.2004
Multistage operation is only possible when firing on oil. It is possible to parameterize if
multistage or modulating operation is used.
Electronic fuel / air ratio control can be configured for both 2-stage and 3-stage burners.
In this operating mode, the oil actuator is not controlled.
Parameter: Operation Mode (Two-stage / Three-stage / Modulating)
Multistage fuel / air ratio control is defined via different load points. These are the sta-
tionary operating points and separately adjustable switch-on / off points.
Parameter: SetPointStage1
Parameter: StartPointStage2
Parameter: OffPointStage2
Parameter: SetPointStage2
Parameter: StartPointStage3
Parameter: OffPointStage3
Parameter: SetPointStage3
Load
Pos.
A
i
r
7550d02E
S2on S2off S2S1
Multistage operation (here: 2-stage)
Between these points, the actuators are adjusted during their continuous travel. The
speeds of the individual actuators will be calculated such that they reach their targets at
the same time.
The speed of the fastest actuator can be parameterized.
Parameter: OperatRampStage
When parameterizing the multistage operating ramp, the speed of the slowest actuator
must be taken into consideration!
When changing from stage 1 to stage 2, first «switch-on point S2» is approached, starting
from «operating point S1». Now, the second fuel valve is opened.
Then, the system travels to «operating point S2».
If the output shall be cut back to stage 1, first «switch-off point S2» will be approached.
If «switch-off point S2» has not yet been set, «switch-on point S2» will be approached
and the fuel valve closed.
Then, the ratio position of «operating point S1» will be approached again.
The procedure is analogous when switching from stage 2 to stage 3 and back again.
Multistage operation
Note
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