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BCU 460, BCU 465 · Edition 11.19
14
Application
1 .1 .7 Flame control using the temperature
FCU 500..H1
M
HT
18
HT
HT
BCU 46x..D1
6
22
µC
BCU 46x..D1
6
22
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 con-
ventional 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 burner con-
trol 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 without evaluat-
ing 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. There is
no longer an active signal at the HT inputs of the burner
control units. The flame signals are monitored once
again by the UV sensor or flame rod.
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.