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01.09.21, Subject to alterations
Flame control with ionisation
monitor
18 Flame control with ionisation
monitor
In the presence of an alternating-current voltage be-
tween burner and ionisation rod, the rectifying effect
of the flame causes a direct current to flow. This ion-
isation current is the flame signal and is amplified
before being output to the control box. A flame can-
not be simulated, because the rectifying effect col-
lapses if there is a short-circuit between sensor
electrode and burner.
Measuring ionisation current
The ionisation current must be measured during
burner start-up and maintenance or after a fault in-
dication in the control box. Disconnect the plug of
the ionisation cable and connect the ionisation
measuring cable.
Perform measurement straight after the post-igni-
tion time during the safety time period !
The ionisation current must be at least 1.5
µA. Cur-
A. Cur-
rents lower than 1.5
µA cause unstable operation or
A cause unstable operation or
shutdown. If the current is too low clean the ionisa-
tion rod and the inside of the burner tube. It may be
necessary to correct the shape of the ionisation rod.
If the ionisation rod is defective, replace the elec-
trode. Reverse the polarity of the ignition transform-
er, if necessary. Check the cables for moisture
formation and dry if necessary.
