Minimum Burner On Time; Safety Interlock (Limits); Protection Of Safety-Relevant Outputs; Emergency Stop - Honeywell BCU 460 Technical Information

Project planning information

6 .4 Minimum burner on time

Even if the start-up signal (ϑ) is applied only briefly, the
time set under parameter 20 elapses. The minimum
burner on time tB can be extended beyond the safety
time t to max. 25 s.
SA
The signal input for the burner start-up signal cannot
be used for a safety shut-down because the BCU con-
trols the valves until the minimum burner on time has
elapsed.
00 02
t
SA

6 .5 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 tem-
perature limiter), Gas
min
purge...) must isolate terminal 5 from the voltage supply.
If the safety interlock is interrupted, the display shows a
blinking 51 to indicate a fault.
BCU 460, BCU 465 · Edition 03.16l
03 04 88
1
5
4
ϑ
7
12
V1
14
V2
9
16-17
18-19
t
t
B
, Gas , tightness control, pre-
max

6 .6 Protection of safety-relevant outputs

When commissioning, do not switch the safety-relevant
outputs to a short-circuit.
Before switching on, ensure that outputs 7, 12 and 14
are not overloaded (> 3 A), using an ohmmeter, for ex-
ample.
All safety-relevant outputs of the BCU are fused with
an internal, replaceable fuse, see page 13 (Connec-
tion diagrams). This affects the outputs for ignition, gas
valve V1 and gas valve V2.
In the event that the second internal, non-replaceable
fuse for these outputs blows, the unit must be sent to
the manufacturer for repair.

6 . 7 Emergency stop

6 . 7 .1 In the event of fire or electric shock

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.

6 . 7 .2 Triggered by the safety interlock (limits)

The safety interlock turns off the power to the input 5,
such as in the event of low air pressure or similar.
69