4 .2 .3 High temperature operation in the case of
BCU . .D2 or BCU . .D3
Operation of firing systems at temperatures above
750°C. The BCU features a fail-safe DI input (DI = Digi-
tal Input). This input supports the "High temperature
operation" function. If firing systems are operated
above 750°C, the system is considered to be a high
temperature equipment (see EN 746-2). Flame control
must be in operation until the furnace wall temperature
has exceeded 750 °C.
Frequently, flame control is dispensed with so as to
achieve a particularly high flexibility of the installation.
This means that no incorrect flame signals, e.g. signals
from a UV sensor which are interpreted as extraneous
signals due to reflection of UV radiation, may lead to
When the DI input is activated, the burner control unit
reverts to this operating mode, i.e.: the BCU operates
without evaluation of the flame signal . The safety
function of the device-internal flame control system
is placed out of operation .
In High temperature mode, the gas valves are opened
without flame control.
The precondition for this operating mode is that an ex-
ternal flame supervision device ensures the presence of
the flame in fail-safe manner indirectly via the tempera-
ture. For this purpose, we recommend a safety temper-
BCU 460, BCU 465 · Edition 03.16l
ature monitor with double thermocouple (DIN 3440).
Sensor discontinuity, sensor short-circuit, failure of a
component or mains failure must set the installation to
a safe state.
The voltage may be applied to the DI input (terminal
6) so as to activate High temperature operation only
when the temperature at the furnace wall has exceeded
750°C. The BCU then starts the burner as usual but
without monitoring the presence of the flame.
If the temperature in the furnace chamber drops below
750°C, the DI input must be disconnected from the
electrical power supply and the furnace must then be
operated with flame control.