FCU 500, FCU 505 · Edition 02.17
145
Glossary
21 Glossary
21 .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 FCU disconnects the gas valves from the
electrical power supply. The controller enable signal is
deactivated. The fault signalling contact remains open.
The display blinks and displays the current program
step, see page 70 (Fault signalling).
After a safety shut-down, the FCU can restart automati-
cally.
21 .2 Fault lock-out
A fault lock-out is a safety shut-down with subsequent
fault lock-out. The system can only be restarted fol-
lowing manual reset. The protective system cannot be
reset by mains failure.
In the event of a fault lock-out of the FCU, the fault sig-
nalling contact closes, the display blinks and shows the
current program step, see page 70 (Fault signalling).
The gas valves are disconnected from the electrical
power supply. The fault signalling contact opens if the
mains voltage fails.
In order to restart, the FCU can only be reset manually
using the button on the front panel, the OCU or the re-
mote reset input (terminal 3).
21 .3 Warning signal
The FCU 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 safety shut-down
or fault lock-out occurs.
