114
To check the combustion quality, the CO
2
content or
the O
2
content of the flue gas is measured. The pre-
vailing air ratio is determined with the measured val-
ues. The relationship between the CO
2
or O
2
content
and air ratio
λ
is illustrated in the following table.
Air ratio
λ–
CO
2
/O
2
content
Air ratio
λ
O
2
content (%) CO
2
content (%) for
natural gas E
CO
2
content (%) for
natural gas LL
CO
2
content (%) for
LPG P
1.20
3.8
9.6
9.2
11.3
1.24
4.4
9.2
9.1
10.9
1.27
4.9
9.0
8.9
10.6
1.30
5.3
8.7
8.6
10.3
1.34
5.7
8.5
8.4
10.0
1.37
6.1
8.3
8.2
9.8
1.40
6.5
8.1
8.0
9.6
1.44
6.9
7.8
7.7
9.3
1.48
7.3
7.6
7.5
9.0
To achieve an optimum combustion control, the system
regularly carries out an automatic self-calibration; also
after a power failure (shutdown). For this, the combus-
tion is briefly regulated to max. ionisation current (cor-
responding to air ratio
λ
=1). Automatic calibration is
carried out shortly after the burner start and lasts
approx. 5 s. During calibration, higher than normal CO
emissions may occur briefly.
Function description
Electronic combustion control unit
(cont.)
5778741
Functions
