PFU 780 · Edition 02.12
15
Behaviour of the pilot burner in the
event of flame failure during operation
If the flame fails during operation, either
an immediate fault lock-out occurs or a
restart occurs. This procedure can be
set via the optical interface (parameter
12, “Pilot burner restart”).
Behaviour of the main burner in the
event of flame failure during start-up
If no flame is detected during the safety
time t
SA2
, either a fault lock-out occurs
or up to three further start-up attempts
occur. (Parameter 11, “Main burner start-
up attempts”).
Behaviour of the main burner in the
event of flame failure during operation
If the flame fails during operation, either
an immediate fault lock-out occurs or a
restart occurs. This procedure can be
set via the optical interface (parameter
13, “Main burner restart”).
Function > PFU 780 program sequence
01
02
03
04
08
00
00
08
05
06
07
Switch on
PFU 780
Pilot burner start-up
with
ϑ
1 signal
Safety interlocks (Limits)
In the event of fault signal:
Reset
If parameter P15 = 1:
flame simulation check
Wait until
waiting time t
W
has elapsed
If parameter P15 = 0:
Flame simulation check
If no flame detected:
next start-up attempt (P10)
or fault lock-out
Start-up position/standby
Safety time t
SA1
running (P22),
ignition in process,
V1 opens and min.
combustion time t
B
starts to elapse (P20)
In the event of flame failure:
restart or fault lock-out
Operating signal
Pilot burner closes
Flame proving period t
FS1
running (P23)
In the event of flame failure:
restart or fault lock-out
Main burner start-up
with
ϑ
2 signal
Wait until
min. burner pause time t
BP
has elapsed (P21)
If parameter P15 = 0:
Flame simulation check
If no flame detected:
next start-up attempt (P11)
or fault lock-out
Safety time t
SA2
running (P24),
V2 opens and
min. combustion time t
B
starts to elapse (P20)
Normal shut-down
via
ϑ
signal for
pilot and main burners
If min. combustion time t
B
has elapsed:
Operation signalling contact
opens,
V1 and V2 close,
min. burner pause time t
BP
starts to elapse (P21)
In the event of flame failure:
restart or fault lock-out
Operating signal
Main burner closes
Flame proving period
t
FS2
running (P25)
In the event of flame failure:
restart or fault lock-out
The air valve can be set to open
with V2 or to be activated exter-
nally (display
A7
) via parameter
30.
The air valve can be set to open
with the operating signal or to be
activated externally (display
A8
)
via parameter 30.