Viessmann FB2A Installation And Service Instructions For Contractors page 120

Function description
Electronic combustion controller
Air factor λ – CO
2
Air factor O content
2
λ
(%)
1.24 4.4
1.27 4.9
1.30 5.3
1.34 5.7
1.37 6.1
1.40 6.5
1.44 6.9
To achieve an optimum combustion con-
trol, the system regularly carries out an
automatic self-calibration; also after a
power failure (shutdown). For this, the
combustion is briefly regulated to max.
ionisation current (equals air factor λ=1).
The 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.
120
/O content
2
CO content (%)
2
for natural gas
E
9.2
9.0
8.7
8.5
8.3
8.1
7.8
(cont.)
CO content (%)
2
for natural gas
LL
9.1
8.9
8.6
8.4
8.2
8.0
7.7
CO content
2
(%) for LPG P
10.9
10.6
10.3
10.0
9.8
9.6
9.3