Siemens LGB22.330A27 - Flame supervision; Flame supervision with ionization probe

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Building Technologies CC1N7435en
HVAC Products 11.01.2007
Flame supervision
At mains voltage U
N = AC 230 V
Detector voltage across terminals 1 and
2 or ground (AC voltmeter Ri ≥ 10 MΩ)
≤ UN
Detector current required for reliable operation min. 3 µA
Possible detector current in operation max. 100 µA
The conductivity and rectifying effect of hot flame gases are used for flame supervision.
For that purpose, AC voltage is applied to the heat-resistant ionization probe which
projects into the flame. The current that flows in the presence of a flame (ionization
current) produces the flame signal which is fed to the input of the flame signal amplifier.
The amplifier is designed such that it only responds to the DC current component of the
flame signal, thereby ensuring that a short-circuit between ionization probe and ground
cannot simulate a flame signal (since in that case AC current would flow).
Basically, the flame supervision circuit is insensitive to adverse effects of the ignition
spark.
However, should the disturbing effects of the ignition spark on the ionization current
exceed a certain level, the electrical connections on the primary side of the ignition
transformer must be changed and / or the location of the ionization probe must be
checked.
Since the ionization current with burner controls operating on AC 110 V is only about
50 % of those operating on AC 230 V, certain applications make it necessary to in-
crease the ionization current with a transformer.
Capacity of transformer: Min. 2 VA
Transforming ratio: Approx. 1.1...1.5
The primary and secondary windings of the transformer must be galvanically sepa-
rated.
L
N
AC 115 V
LGB2...
12
2
1
AC 115...230 V
7435v01/0504
ION
Flame supervision with
ionization probe
Ionization current su-
pervision with burner
controls operating on
A
C 110 V
Connection of
transformer