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Building Technologies Basic Documentation LMV5... CC1P7550en
6 Fuel-air ratio control (FARC) 22.05.2018
6.6.2 Limitation of load range
The curves are defined by the 2 limits: Low-fire and nominal load (maximum load). In
certain cases, it has proven practical to limit the burner’s output, either temporarily or
permanently.
This limitation of the burner’s working range can make sense in both directions. The
burner’s working range then looks as follows:
Pos.
Ignition
Low fire
Min. load
Max. load
Nominal load
AIR
AUX
FUEL
7550d06E
Load
Figure 44: Limited working range
The usable load range always lies within the defined curves. This means: If the
minimum load is smaller than the low-fire load, any load below low-fire is ignored. And if
the maximum load is greater than the nominal load, it is ignored as well. If the minimum
load is greater than or equal to low-fire, it assumes the role of the low-fire load, which
means that – after ignition – the minimum load is considered. The 2 parameters
MinLoad... and MaxLoad... can be set depending on the type of fuel,
whereby:
Low-fire load ′ minimum load ′ maximum load ′ nominal load
Parameter MinLoadGas
MaxLoadGas
MinLoadOil
MaxLoadOil
The plant operator can confine the load range further:
Parameter UserMaxLoadMod
UserMaxLoadStg (S1 / S2 / S3)
Here, the plant operator can further confine the maximum output to be delivered. There
is a limit parameter for modulating operation and a limit parameter for multistage
operation.
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