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Glossary
11 Glossary
11 .1 Safety shut-down
The burner control unit performs a safety shut-down
immediately after receiving a signal from a safety de-
vice or after a fault is detected (e.g. flame or air pressure
failure). The safety shut-down prevents operation of the
burner by closing the fuel shut-off valves and deacti-
vating the ignition device.
For this, the BCU disconnects the gas valves and the ig-
nition transformer from the electrical power supply. The
operation signalling contact and the controller enable
signal are deactivated. The fault signalling contact re-
mains open. The display blinks and displays the current
program step, see page 37 (Fault message (blink-
ing)).
After a safety shut-down, the BCU can restart auto-
matically.
11 .2 Fault lock-out
A fault lock-out is a safety shut-down with subsequent
lock-out. The system can only be restarted following
manual reset. The protective system cannot be reset by
mains failure.
In the event of a fault lock-out of the BCU, the fault
signalling contact closes, the display blinks and shows
the current program step, see page 37 (Fault mes-
sage (blinking)). The gas valves are disconnected from
BCU 370 · Edition 01.19
the electrical power supply. The fault signalling contact
opens if the mains voltage fails.
In order to restart, the BCU can only be reset manually
using the button on the front panel, the OCU or the re-
mote reset input (terminal 3).
11 .3 Warning signal
The BCU reacts to operating faults, e.g. in the case of
permanent remote resets, with a warning signal. The
display blinks and shows the corresponding warning
message. The warning signal ends once the cause has
been eliminated.
The program sequence continues. No fault signal is ac-
tivated.
11 .4 Timeout 25 s/250 s
For some process faults, a timeout phase elapses be-
fore the BCU reacts to the fault. The phase starts as
soon as the BCU detects the process fault and ends
after 25 to 250 s. A safety shut-down or fault lock-out
is then performed. If the process fault ends during the
timeout phase, the process continues as before.
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