Description
5-4
5.1.4 Variable switch-ON threshold (hysteresis)
The switch-ON threshold of the evaluation channel is
variable and can be set by means of DIP switch S1. The
adjustable range is between 25 and 75% of the analogue
flame signal. The device has been factory set to 25%. A
higher switch-ON threshold may sometimes be used to
block out light from neighbour burners.
A continuous signal from neighbour flames of more than
25% of the analogue flame signal is a safety risk and
must not be turned off by a raised switch-ON threshold.
Given a raised switch-ON threshold, the switch-OFF
threshold remains firmly on 25%.
After having changed the switch-ON threshold, stop the
burner and check whether the switch-OFF threshold falls
short safely, and the flame relay is switched off.
5.1.5 Fixed switch-OFF threshold
The switch-OFF threshold of both channels has been de-
fined at 25% and cannot be changed.
5.1.6 Pre-alarm warning
An pre-alarm warning indicates unfavourable combustion
processes before the system is switching-OFF com-
pletely. The switch threshold is fixed to 50% of the ana-
logue output signal. This function is used to reliably indi-
cate continuous aggravation of the flame signal by soiling
of the lens (flame scanner), change of the flame / fuel
quality or raising of the flame. The availability of the plant
is thus improved.
The MA LED is used as a indicator. A 24 V / 100 mA out-
put is available for external processing.
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