Siemens LMV5 Series Basic Documentation page 249

Siemens Building Technologies
HVAC Products
18.2.3 Lambda factor
The system calculates the lambda factor from the O
the required air rate reduction (standardized value to attain the O
lambda factor reflects the ratio of the actual lambda change and the theoretical lambda
change, in relation to a change of the air rate.
With an ideal burner, a relative air rate reduction of 10 % produces a
lambda change of
corresponding to a lambda factor of 1.
Example:
If the amount of gas is influenced by the fan pressure, a reduction of the air volume can
simultaneously lead to an increase in the amount of gas. In practice, this results in a
more pronounced change of the lambda value. If the change of lambda value is twice
the theoretical value, an air rate change of 10 % produces
λ
a value of
λ
=
Praxis
λ
From the lambda values of the ratio curve, the setpoint curve and the standardized
value (required air ratio reduction), the lambda factor is calculated as follows:
λ λ
Soll - Verbund
Lambdafaktor =
Normierwert
The system should be adjusted such that the lambda factor across the load range will
be as flat as possible. In the future, this can be checked with the ACS450 PC tool.
Without the tool, the lambda factors can be calculated according to the above formula
to be entered in a graph.
Basic Documentation LMV51...
18 Addendum 4: LMV52... with O2 trim control and O2 module
λ
neu
λ
= = 0,9
Theorie
λ
alt
, corresponding to a lambda factor of 2.
neu
= 0,8
alt
100
ratio value, the O setpoint and
2 2
setpoint). The
2
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CC1P7550en
01.10.2003