PFU 780 · Edition 02.12
13
3 .2 PFU 780 program sequence
Normal start-up
If an “old” fault is still being signalled
after switching on, it will be necessary
to reset this first.
The safety interlocks (terminal 26e) must
be closed and the burner control unit
must be switched on.
The PFU 780 conducts a self-test when
in the start-up position (the burner is
switched off). If it does not determine a
malfunction of the internal electronic cir-
cuitry or of the flame sensors, the burner
can be started. The pilot burner start-up
is activated via the signal input “Start-
up signal
ϑ
1” (terminal 10e). Once the
start-up signal
ϑ
1 has been applied, the
PFU 780 opens valve V1 and ignites the
burner. The ignition time t
Z
is constant. If
a flame is detected during the safety time
t
SA1
, the flame proving period t
FS1
starts
after the safety time t
SA1
has elapsed.
If the pilot burner has been started suc-
cessfully and its flame has stabilised, the
burner control unit issues the Enable
signal for main burner operation. The
operation signalling contact for the pilot
burner (terminals 2c/4c) closes.
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
PFU 780
If the air valve control is used,
the unit offers the following
additional functions:
In start-up position, the air valve
can be opened for cooling
A
(display
A0
).
Using parameter 31, it can be
determined whether the air valve
can be activated externally dur-
ing start-up (display
A1
).
The air valve can be set to open
together with V1 (display
A2
) via
parameter 30.
Function
▼