BCU 480 · Edition 06.07
23
High temperature operation in the case of
5 .2 .5
BCU . .D2 or BCU . .D3
Parameter 33
Operation of firing systems at temperatures above 750°C.
The BCU features a safety-relevant DI input (Digital Input).
This input supports the “High temperature operation” func-
tion. 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. Note the requirements
of the Standards!
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 faults.
When the DI input is activated, the burner control unit reverts
to High temperature operation. This means: 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 high temperature operation is that an
external flame safeguard ensures the presence of the flame
in fail-safe manner indirectly via the temperature. For this
purpose, we recommend a safety temperature monitor with
twin 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 tem-
perature at the furnace wall has exceeded 750°C. The BCU
starts the burner as usual, without monitoring the presence
of the flame.
t
SA
t
Z
88
04
02
03
00
t
t
FS
4
5
1
7
9
18-19
12
V1
14
V2
16-17
6
DI
1
ϑ
1
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 be operated with the internal
flame control system.
Parameters > Flame control
t
