BCU 480 · Edition 06.07
50
Minimum combustion time
7 .2
Even if the start-up signal (
ϑ
) is applied only briefly, the time
set under parameter 20 elapses before the burner control
unit shuts down the burner or signals a fault. The minimum
combustion time t
B
can be extended beyond the safety time
t
SA
to max. 25 s.
The signal inputs for the pilot/main burner start-up signal can-
not be used for a safety shut-down because the unit controls
the valves until the minimum combustion time has elapsed.
04
06
07
t
t
SA2
t
B
9
12
V1
1
14
V2
2
2
1
24
21
88
4
5
2
18-19
16-17
28-29
ϑ
1
ϑ
2
In the case of pilot/main burner monitoring, the minimum
combustion time only has an effect on the behaviour of the
main burner. The minimum combustion time for the pilot burner
is limited to the safety time on start-up (t
SA
).
Background: The pilot burner is only used in single-stage
operation.
Safety interlocks (Limits)
7 .3
The limiters in the safety interlock (linking of all the relevant
safety control and switching equipment for the use of the ap-
plication, e.g. safety temperature limiter, minimum and maxi-
mum gas pressure, tightness control) must isolate terminal
5 from the voltage supply. If the safety interlock is interrupted
or if fuse F1 has tripped, this is indicated by a blinking
51
on
the display.
If the safety interlocks fail, an immediate program abort with
switch-off of all outputs occurs (even during the safety time).
If the safety interlocks are operational again or the unit is
switched back on, the program run is restarted in standby.
Emergency stop
7 .4
In the event of fire or electric shock
7 .4 .1
If there is a risk of fire, electric shock or similar, inputs L1, N
and 5 (safety interlocks) of the BCU should be disconnected
from the electrical power supply – this should be reflected in
the wiring on site.
Via the safety interlocks (limits)
7 .4 .2
The safety interlock turns off the power to the input 5, such as
in the event of air deficiency or similar.
Project planning information
