BCU 370 · Edition 01.19
67
Project planning information
6 .2 Fan control
The BCU features an output for fan control. The max.
start-up current for the fan motor must not exceed the
permitted contact rating of this output, see page 73
(Technical data). If necessary, an external contactor
must be used.
6 .3 Controlling the butterfly valve
The required burner commissioning time depends on
the running time of the butterfly valve actuator.
The BCU 370 waits for the feedback signal to indicate
that the actuator has reached the Open position, for in-
stance, before the pre-purge time is started.
The Ignition position is always approached via the Open
position.
Once the butterfly valve has been set to the relevant
position, a plausibility check takes place. The related
control output is switched off briefly. The feedback sig-
nal must drop accordingly.
6 .4 Safety interlock (limits)
The limiters in the safety interlock (linking of all the rel-
evant safety control and switching equipment for the
use of the application, for example STL [safety temper-
ature limiter]) must isolate terminal 24 from the voltage
supply. If the safety interlock is interrupted, the display
shows a blinking
50
as a warning signal. The program
sequence is interrupted. All of the BCU 370’s outputs
are disconnected from the electrical power supply. The
burner control unit restarts when the safety interlock is
switched on again and the start-up signal (
ϑ
) activated.
6 .5 Too many remote resets
If a remote reset is made 5 times in 15 minutes (termi-
nal 23 or by bus signal), the BCU is locked, shows fault
message
10
, “Too many remote resets”, and can only
be reset by pressing the Reset/Information button.