BCU 560, BCU 565 · Edition 02.16
127
20 Glossary
20 .1 Safety time on start-up t
SA1
This refers to the period of time between switching on and
switching off of the gas valve, when no flame signal is detected.
The safety time on start-up t
SA1
(2, 3, 5 or 10 s) is the minimum
operating time of the burner and burner control unit.
20 .2 Ignition time t
Z
If no malfunction is detected during the waiting time t
W
, the
ignition time t
Z
then starts to elapse. Voltage is supplied to the
pilot gas valve and the ignition transformer and the burner is
ignited. The duration of the ignition time is either 1, 2, 3 or 6 s
(depending on safety time t
SA1
selected).
20 .3 Safety time during operation t
SB
04
t
t
SB
04
88
ϑ
1
46
11
9
5
13
V1
14
V2
L1
42
41
If the flame fails during operation, the valve outputs are dis-
connected within the safety time t
SB
.
The default safety time during operation t
SB
in accordance with
EN 298 is 1 second. In accordance with EN 746-2, the safety
time of the installation during operation (including closing time
of the valves) may not exceed 3 s. Note the requirements of
the standards!
20 .4 Safety interlocks
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/maximum
gas pressure) must isolate input from the voltage supply.
20 .5 Safety shut-down
After an installation fault (e.g. flame or air pressure failure), the
burner control unit performs a safety shut-down. The display
blinks and displays the current program step, see page 50
(Fault signalling). This involves disconnecting the power from
the gas valves and the ignition transformer. The operation sig-
nalling contact and the controller enable signal are deactivated.
After a safety shut-down, the BCU can either restart or perform
a fault lock-out, depending on the parameter settings.
20 .6 Safety shut-down with subsequent fault lock-
out (fault lock-out)
In the event of a fault lock-out, the fault signalling contact closes,
the display blinks and shows the current program step, see
page 50 (Fault signalling). The gas valves are disconnected
from the electrical power supply.
After a fault lock-out, the BCU must be reset manually using
the button on the front panel, the OCU or the remote reset
input (terminal 3).
The BCU cannot be reset by mains failure (non-volatile fault
lock-out). The fault signalling contact does, however, open as
soon as the mains voltage fails.
