Viessmann Vitodens 222-F Installation And Service Instructions Manual page 115

Function description
Electronic combustion control unit
(cont.)
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 =1). Automatic calibration is
λ
carried out shortly after the burner start and lasts
approx. 5 s. During calibration, higher than normal CO
emissions may occur briefly.
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