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BCU 580 · Edition 11.15l
13
Application
1 .1 .5 Flame control using the temperature
FCU 500..H1
M
HT
18
HT
HT
BCU 580..D
49
5
8
µC
BCU 580..D
49
5
8
µC
5-8
STM
In high temperature systems (temperature > 750°C),
the flame may be controlled indirectly via the tempera-
ture.
As long as the temperature in the furnace chamber is
below 750°C, the flame must be controlled by conven-
tional methods.
If the temperature in the furnace chamber rises above
the spontaneous ignition temperature of the gas/air
mixture (> 750°C), the FCU signals to the downstream
burner control units via the fail-safe HT output that
the furnace system is in High temperature mode (HT).
When the HT input is activated, the burner control units
switch to High temperature mode. They operate with-
out evaluating the flame signal and their internal flame
control is non-functional.
If the furnace temperature falls below the spontaneous
ignition temperature (< 750°C), the FCU disconnects
the HT output from the electrical power supply. As soon
as the signal to the HT inputs of the burner control
units is no longer present, the flame signals are once
again monitored by a UV sensor or ionization electrode.
In the event of a fault in a temperature monitoring com-
ponent (e.g. sensor discontinuity, sensor short-circuit)
or in the event of a mains failure, the flame control task
is transferred to the burner control units.