Electronic Combustion Control Unit - Viessmann VITODENS 200-W Installation And Service Instructions Manual

Function description
Assigning heating circuits to the remote control
Note
One heating circuit can be assigned to the Vitotrol
200A and 200 RF.
Up to three heating circuits can be assigned to the
Vitotrol 300A and 300 RF.
A maximum of 2 hardwired remote control units or 3
wireless remote controls may be connected to the con-
trol unit.
If the assignment of a heating circuit is later cancelled,
reset coding address "A0" in the "Heating circuit"
group for this heating circuit to 0 (fault message bC,
bd, bE).

Electronic combustion control unit

The electronic combustion controller utilises the physi-
cal correlation between the level of the ionisation cur-
rent and the air ratio . The maximum ionisation cur-
λ
rent is achieved at an air ratio of 1 for all gas qualities.
The ionisation signal is evaluated by the combustion
controller and the air ratio is adjusted to a value
between =1.24 and 1.44. This range provides for an
λ
optimum combustion quality. Thereafter, the electronic
gas valve regulates the required gas volume subject to
the prevailing gas quality.
Air ratio CO /O content
λ–
2 2
Air ratio
λ
1.20
1.24
1.27
1.30
1.34
1.37
1.40
1.44
1.48
For optimum combustion control, 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 (corre-
sponding to air ratio =1). Automatic calibration is car-
λ
ried out shortly after the burner start and lasts approx.
5 s. During calibration, higher than normal CO emis-
sions may occur briefly.
120
O content (%) CO content (%) for
2 2
natural gas E
3.8
4.4
4.9
5.3
5.7
6.1
6.5
6.9
7.3
(cont.)
To check the combustion quality, the CO
the O content of the flue gas is measured. The pre-
2
vailing air ratio is determined with the measured val-
ues. The relationship between the CO
and air ratio is illustrated in the following table.
λ
CO content (%) for
2
natural gas LL
9.6
9.2
9.0
8.7
8.5
8.3
8.1
7.8
7.6
content or
2
or O content
2 2
CO content (%) for
2
LPG P
9.2 11.3
9.1 10.9
8.9 10.6
8.6 10.3
8.4 10.0
8.2 9.8
8.0 9.6
7.7 9.3
7.5 9.0