Krom Schroder PFU 780 Manual

6 Edition 02.12
AGA
Technical Information · GB
Burner control unit PFU 780
• For pilot and main burners of unlimited capacity in thermoprocessing
equipment pursuant to EN 746-2
• Plug-in function unit for mounting in 19" module subracks
• Separate flame control for pilot burner and main burner by UV,
ionisation or a further option of using the furnace chamber temperature
• Display of the program status, unit parameters and flame signal;
Manual mode for burner adjustment and for diagnostic purposes
• Visualisation and adaptation to the specific application via the PC
programming and diagnostic software BCSoft to simplify logistics
management
• Air valve control relieves the furnace control
• Certified for systems up to SIL 3 and compliant with PL e

PFU 780 · Edition 02.12 2
▼= To be continued
Table of contents
Burner control unit PFU 780......................... 1
Table of contents .................................2
1 Application.....................................4
1.1 Examples of application..........................6
1.1.1 Stage-controlled main burner with alternating pilot burner 6
1.1.2 Stage-controlled main burner with permanent pilot burner 7
1.1.3 Modulating-controlled burner ....................... 8
1.1.4 PFU 780..D:
High temperature equipment ............................9
2 Certification ...................................10
3 Function.......................................11
3.1 Connection diagram ............................11
3.1.1 PFU 780 .........................................11
3.1.2 PFU 780..K2......................................12
3.2 PFU 780 program sequence ....................13
3.3 Program status and fault messages..............16
4 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1 Scanning the parameters .......................19
4.2 Flame control.................................20
4.2.1 Flame signal, pilot burner ......................... 20
4.2.2 Flame signal, main burner ........................ 20
4.2.3 Program status when the most recent fault occurred... 20
4.2.4 Switch-off threshold of the flame amplifier ........... 20
4.2.5 High temperature operation with PFU..D..............21
4.2.6 UVS check...................................... 24
4.3 Pilot and main burner monitoring . . . . . . . . . . . . . . . . 25
4.3.1 Permanent pilot burner ........................... 26
4.3.2 Interrupted pilot burner ............................27
4.4 Behaviour in start-up position/standby............28
4.4.1 Flame simulation check in start-up position/standby ... 28
4.4.2 Minimum burner pause time tBP . . . . . . . . . . . . . . . . . . . 29
4.5 Behaviour during start-up ......................30
4.5.1 Safety time on start-up tSA ......................... 30
4.5.2 Flame proving period tFS ...........................31
4.5.3 Minimum combustion time tB......................31
4.5.4 Burner start-up attempts.......................... 32
4.6 Behaviour during operation .....................34
4.6.1 Safety time during operation tSB for pilot and main
burners ............................................ 34
4.6.2 Fault lock-out or restart, pilot burner ................ 34
4.6.3 Fault lock-out or restart, main burner................ 36
4.7 Air valve control PFU..L .........................38
4.7.1 Purge .......................................... 38
4.7.2 Cooling in start-up position/standby ................ 38
4.7.3 Burner start..................................... 38
4.7.4 Air valve opens in the case of external activation (not
during start-up) ...................................... 39
4.7.5 Air valve opens in the case of external activation (even
during start-up) ...................................... 40
4.7.6 Air valve opens with valve V2 .......................41
4.7.7 Air valve opens with operating signal ............... 42
4.7.8 Low fire over run time tKN after a normal shut-down ... 43
4.7.9 Behaviour of the air valve in the event of a fault lock-out 44
4.8 Manual operation .............................45
4.8.1 Manual mode limited to 5 minutes.................. 45
4.9 Password....................................46
5 Selection .....................................47
5.1 Calculating the safety time tSA ...................47
5.2 Selection table................................48
5.2.1 Type code ...................................... 48
6 Project planning information .....................49
6.1 Cable selection ...............................49
6.1.1 Ignition cable .................................... 49
6.1.2 Ionisation cable ................................. 49
6.1.3 UV-Leitung ..................................... 49
6.2 Ignition electrode .............................49
6.2.1 Electrode gap ................................... 49
6.2.2 Star electrodes .................................. 49
6.3 Minimum combustion time .....................50
6.4 Safety interlocks (Limits) ........................50
6.5 Emergency stop...............................50

PFU 780 · Edition 02.12 3
▼= To be continued
6.5.1 In the event of fire or electric shock.................. 50
6.5.2 Via the safety interlocks (limits) ..................... 50
6.6 Reset .......................................51
6.6.1 Parallel reset.....................................51
6.6.2 Permanent remote reset ...........................51
6.6.3 Automatic remote reset (PLC) .......................51
6.6.4 Burner start......................................51
6.6.5 Restart and start-up attempts.......................51
6.7 Fault message................................52
6.8 Protecting the pilot burner from overload ..........52
6.9 Installation ...................................52
6.10 Wiring ......................................52
6.10.1 UVS sensor wiring............................... 52
6.11 PFU switched off ..............................52
6.12 Furnace control ..............................53
6.13 Note on EC type-examination...................53
6.14 Mains switch ................................53
6.15 Changing parameters.........................53
7 Flame control..................................54
7.1 With ionisation sensor ..........................54
7.2 With UV sensor ...............................54
7.3 Via the temperature in high temperature equipment 54
8 Accessories...................................55
8.1 High-voltage cable ............................55
8.2 BCSoft.......................................55
8.3 Stickers for labelling ...........................55
8.4 “Changed parameters” stickers .................55
8.5 Radio interference suppressed electrode adapters . 56
8.6 Socket connectors.............................56
8.7 Module subrack ..............................56
8.8 Power supply PFP 700 .........................57
8.9 Relay module PFR 704 .........................58
8.10 Field bus interface PFA 700.....................59
8.11 Impulse system MPT 700.......................60
9 Technical data................................. 61
9.1 Safety-specific characteristic values...............63
9.2 Operating controls ............................64
10 Maintenance cycles............................65
11 Legend ......................................66
12 Glossary.....................................67
12.1 Waiting time tW........................... 67
12.2 Safety time on start-up tSA .....................67
12.3 Ignition time tZ...............................67
12.4 Flame simulation/Flame simulation delay time tLV . 67
12.5 Safety time during operation tSB .............. 67
12.6 Flame signal.................................68
12.7 Fault lock-out ................................68
12.8 Safety interlocks (Limits) ........................68
12.9 Pilot gas valve V1 .............................68
12.10 Main gas valve V2 ...........................68
12.11 Continuous operation.........................68
12.12 Air valve ...................................68
12.13 Diagnostic coverage DC ......................69
12.14 Mode of operation ...........................69
12.15 Safe failure fraction SFF .......................69
12.16 Probability of dangerous failure PFHD...........69
12.17 Mean time to dangerous failure MTTFd..........69
Feedback ......................................70
Contact........................................70
Table of contents

PFU 780 · Edition 02.12 4
Module subrack
BGT for instance
serves to accom-
modate several
function units. It
is provided with
a backplane with
screw terminals
for simple, reliable
wiring.
1 Application
The burner control units PFU 780 control, ignite and monitor
gas burners for intermittent or continuous operation. As a
result of their fully electronic design they react quickly to vari-
ous process requirements and are therefore also suitable for
frequent cycling operation.
The PFU 780 can be used for industrial burners of unlimited
capacity which are ignited by pilot burners. Pilot and main
burners are controlled and monitored independently. This
reduces the main burner start-up time. The pilot burner can
burn permanently or be switched off. The main burners may
be modulating or stage-controlled.
On industrial furnaces, the PFU 780 reduces the load on the
central furnace control by taking over tasks that only relate
to the burner, for example it ensures that the burner always
ignites in a safe condition after it has been restarted.
The burner control unit is used for burners with mechanical
combustion air supply where the fan is controlled by a separate
logic and for atmospheric burners.
The air valve control on the PFU 780L assists the furnace control
for cooling, purging and capacity control tasks.
The program status, the unit parameters and the level of the
flame signal can be read directly from the unit. Pilot and main
burners can be controlled manually for commissioning and
diagnostic purposes.
If the local requirements on the burner control units change,
the PC software BCSoft can be adjusted to the unit parameters
of the application by using the optical interface.
To support service personnel, BCSoft offers a convenient visu-
alisation system of the input and output signals and the error
history.

PFU 780 · Edition 02.12 5
Application
Bogie hearth forging furnace
in the metallurgical industry
Intermittent shuttle kiln
in the ceramics industry
Walking beam furnace
with overhead firing

PFU 780 · Edition 02.12 6
VR..L
VAG
SPS
PLC
CPE
DI
L1, N, PE
P
2
1
t
1
2
ϑ1
ϑ2
A
P
DI
UV
02–0402–04 06–08 06–08
VBY
PFU 780 10e
2c
4c
18a
26e10c
22e
22a
28c16c18e
6a
6e
2e
4e
14a30e 10a
TZI
2
1
ϑ1 ϑ2
µC
1.1 Examples of application
1.1.1 Stage-controlled main burner with
alternating pilot burner
Control: Main burner ON/OFF.
The main burner can be started with
reduced capacity after the operating
signal from the pilot burner has been
detected. The pilot burner is switched
off automatically after the main burner
has started up. When the main burner is
switched off, the pilot burner automati-
cally switches on again.
A UV sensor monitors the flame signal
from pilot and main burners. UV sensor
UVD 1 is used for continuous operation,
UV sensor UVS for intermittent operation.
Application

PFU 780 · Edition 02.12 7
VR..R
VAG
SPS
PLC
CPE
DI
L1, N, PE
P
2
1
A
P
DI
VBY
PFU 780 10e
2c
4c
18a
26e10c
22e
22a
28c16c18e
6a
6e
2e
4e
14a30e 10a
TZI
t
1
2
0402–04 06–08 06–08 04
2
1
ϑ1 ϑ2
µC
ϑ1
ϑ2
26a
Application > Examples of application
1.1.2 Stage-controlled main burner with
permanent pilot burner
Control: Main burner ON/OFF.
The main burner can be started with
reduced capacity after the operating
signal from the pilot burner has been
detected. Pilot and main burners can
be operated simultaneously. Both are
ionisation-controlled independently.

PFU 780 · Edition 02.12 8
VAG
VBY
SPS
PLC
CPE
DI
L1, N, PE
2
1
P
DI
BV+IC
mA
PFU 780 10e 2e
4e
2c
4c
6a
6e
26a
26e10c
TZI
22a
28c
16c18e
14a
18a
M
2
1
ϑ1 ϑ2
µC
Application > Examples of application
1.1.3 Modulating-controlled burner
Control: Main burner continuous
The butterfly valve for air BV is moved
to ignition position in order to start the
main burner. The main burner can be
started at low-fire rate after the operat-
ing signal from the pilot burner has been
detected. The control system controls the
burner capacity via the butterfly valve for
air BV after the operating state has been
signalled. Pilot and main burners can be
operated simultaneously.

PFU 780 · Edition 02.12 9
STW
L1
>750 °C
µC
PFU 780..D
18a
26a
DI
22a
µC
PFU 780..D
18a
26a
DI
22a
Application > Examples of application
1.1.4 PFU 780..D:
High temperature equipment
The flame is controlled indirectly on the
basis of the temperature. During the
start-up process, as long as the wall
temperature is below auto ignition tem-
perature the flame must be controlled by
conventional methods. When the work-
ing temperature has exceeded 750°C,
the safety temperature monitor (STW)
takes over the indirect flame control.

PFU 780 · Edition 02.12 10
2 Certification
Certified pursuant to SIL
For systems up to SIL 3 pursuant to EN 61508
Pursuant to EN ISO 13849-1:2006, Table 4, the PFU can be
used up to PL e.
EC type-tested and certified
pursuant to
– Gas Appliances Directive (2009/142/EC) in conjunction
with EN 298:2004-01,
Meets the requirements of the
– Low Voltage Directive (2006/95/EC),
– EMC Directive (2004/108/EC).
PFU..T is FM approved
Factory Mutual Research Class: 1997.
Suitable for applications pursuant to NFPA 86.
www.approvalguide.com
AGA approved
AGA
Australian Gas Association, Approval No.: 5597
www.aga.asn.au/product_directory

PFU 780 · Edition 02.12 11
N (L2)
22e
16c
N
26e
30a
32c
230 V
F1
18e
2a
4a
a
2e
4e
s
2c
4c
m
sk1
V2
V1
L1 (L1)
max. 1 A, 24 V
v2
v1
6a
6e
n
c1
24 V
0 V
c2
10c
12c
10a
12a
30e
22a
P
DI
A
2
1
1
N
2
28c
26a
ϑ1
ϑ214a
14e
10e
12e
24c
20c
18a
l
20c
18a
N
26a
26a
N
28c 28c
18a
Z
I
UVS 1
2
324c
L
N
M
V2
V1
C
µC
SK
A
S
PFU 780
3 Function
3.1 Connection diagram
For cable selection and wiring, see page 49 (Project plan-
ning information).
3.1.1 PFU 780
For the explanation of symbols, see page 66 (Legend).

PFU 780 · Edition 02.12 12
N (L2)
22e
16c
N
26e
30a
32c
230 V
F1
18e
2a
4a
a
2e
4e
s
2c
4c
m
sk1
V2
V1
L1 (L1)
max. 1 A, 24 V
v2
v1
6a
6e
n
c1
24 V
0 V
c2
10c
12c
10a
12a
30e
22a
P
DI
A
2
1
1
N
2
28c
26a
ϑ1
ϑ214a
14e
10e
12e
24c
20c
18a
l
20c
18a
N
26a
26a
N
28c 28c
18a
Z
I
UVS 1
2
324c
L
N
M
V2
V1
C
µC
SK
A
S
PFU 780..K2
Function > Connection diagram
3.1.2 PFU 780..K2
As a replacement unit for burner control unit PFU 798.
For the explanation of symbols, see page 66 (Legend).

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 ϑ1” (terminal 10e). Once the
start-up signal ϑ1 has been applied, the
PFU 780 opens valve V1 and ignites the
burner. The ignition time tZis constant. If
a flame is detected during the safety time
tSA1, the flame proving period tFS1 starts
after the safety time tSA1 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 ϑ1 signal
Safety interlocks (Limits)
In the event of fault signal:
Reset
If parameter P15 = 1:
flame simulation check
Wait until
waiting time tW
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 tSA1
running (P22),
ignition in process,
V1 opens and min.
combustion time tB
starts to elapse (P20)
In the event of flame failure:
restart or fault lock-out
Operating signal
Pilot burner closes
Flame proving period tFS1
running (P23)
In the event of flame failure:
restart or fault lock-out
Main burner start-up
with ϑ2 signal
Wait until
min. burner pause time tBP
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 tSA2 running (P24),
V2 opens and
min. combustion time tB
starts to elapse (P20)
Normal shut-down
via ϑsignal 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
tFS2 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
▼

PFU 780 · Edition 02.12 14
01
02
03
04
08
00
00
08
05
06
07
Switch on PFU 780
Pilot burner start-up
with ϑ1 signal
Safety interlocks (Limits)
In the event of fault signal:
Reset
If parameter P15 = 1:
flame simulation check
Wait until
waiting time tW
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 tSA1
running (P22),
ignition in process,
V1 opens and min.
combustion time tB
starts to elapse (P20)
In the event of flame failure:
restart or fault lock-out
Operating signal
Pilot burner closes
Flame proving period tFS1
running (P23)
In the event of flame failure:
restart or fault lock-out
Main burner start-up
with ϑ2 signal
Wait until
min. burner pause time tBP
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 tSA2 running (P24),
V2 opens and
min. combustion time tB
starts to elapse (P20)
Normal shut-down
via ϑsignal 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
tFS2 running (P25)
In the event of flame failure:
restart or fault lock-out
The PFU coordinates the correct program
run for the pilot and main burners. The
main burner can be started via the sig-
nal input “Start-up signal ϑ2” (terminals
14a/14c) if required.
Once the start-up signal ϑ2 has been
applied (terminals 14a and 14e), the
PFU 780 opens valve V2. The main
burner is ignited by the pilot burner.
If a flame is detected during the safety
time t
SA2
, the flame proving period t
FS2
starts after the safety time tSA2 has
elapsed. If the main burner has been
started successfully and its flame has
stabilised, the operation signalling con-
tact (terminals 6a/6e) closes.
Start-up of the pilot burner without
flame signal
If no flame is detected during the safety
time t
SA1
, either a fault lock-out occurs
or up to three further start-up attempts
occur. (Parameter 10, “Pilot burner start-
up attempts”).
Function > PFU 780 program sequence
The air valve can be set to open
together with V1 (display
A4
) via
parameter 30.
The air valve can be set to open
together with V1 (display
A3
) via
parameter 30.
The air valve can be set to open
together with V1 (display
A5
) via
parameter 30.
The air valve can be set to open
with V2 or to be activated ex-
ternally (display
A6
) via param-
eter30.
▼

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 tSA2, 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 ϑ1 signal
Safety interlocks (Limits)
In the event of fault signal:
Reset
If parameter P15 = 1:
flame simulation check
Wait until
waiting time tW
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 tSA1
running (P22),
ignition in process,
V1 opens and min.
combustion time tB
starts to elapse (P20)
In the event of flame failure:
restart or fault lock-out
Operating signal
Pilot burner closes
Flame proving period tFS1
running (P23)
In the event of flame failure:
restart or fault lock-out
Main burner start-up
with ϑ2 signal
Wait until
min. burner pause time tBP
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 tSA2 running (P24),
V2 opens and
min. combustion time tB
starts to elapse (P20)
Normal shut-down
via ϑsignal 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
tFS2 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.

PFU 780 · Edition 02.12 16
Function
Program status DISPLAY Fault message (blinking*)
Start-up position/standby 00
Cooling A0
Waiting time/Pause time 1 Flame simulation, pilot burner
Safety time on start-up, pilot burner 2 Start-up without flame signal, pilot burner
Flame proving period, pilot burner 3 Flame failure during flame proving period, pilot burner
Operation, pilot burner 4 Flame failure during operation, pilot burner
Waiting time, main burner 5 Flame simulation, main burner
Safety time on start-up, main burner 6 Start-up without flame signal, main burner
Flame proving period, main burner 7 Flame failure during flame proving period, main burner
Operation, main burner 8 Flame failure during operation, main burner
Purge P0
Air valve A
High temperature operation** . .
10 Faulty remote reset
32 Supply voltage too low
33 Faulty parameterisation
35 Short-circuit on a valve output
3.3 Program status and fault messages
During operation, the 7-segment display shows the program
status. In the event of a fault, the PFU halts the program run,
the display blinks and it then displays the cause of the fault.
The burner control unit can be reset using the Reset button
or the remote reset.
▼

PFU 780 · Edition 02.12 17
Program status DISPLAY Fault message (blinking*)
36 Short-circuit on ignition or valve output
51 Safety interlock failure
52 Permanent reset
53 Time between two start-ups is too short
* In Manual mode, two dots will blink on the display in program status 01 – 08 .
** Optionally available.
Function > Program status and fault messages

PFU 780 · Edition 02.12 18
4 Parameters
Description Parameter Value range Factory default
setting Adjustable*
Flame signal, pilot burner 01 0 – 30 μA
Flame signal, main burner 02 0 – 30 μA
Program status when the most recent fault occurred 03 x0 – x8
Switch-off threshold, pilot burner 04 1 – 20 µA 1 µA 
Switch-off threshold, main burner 05 1 – 20 µA 1 µA 
Start-up attempts, pilot burner 10 1 – 4 1
Start-up attempts, main burner 11 1 – 4 1
Restart, pilot burner 12 0; 1 0
Restart, main burner 13 0; 1 0
Safety time during operation for V1 and V2 tSB 14 1; 2 s 1 s 
Flame simulation check in start-up position/standby 15 0; 1 1
Permanent pilot burner 16 0; 1 1
Minimum combustion time tB20 25 s tSA 
Minimum burner pause time tBP 21 0 – 250 s 0 s 
Pilot burner safety time on start-up tSA1 22 3; 5; 10 s 
Pilot burner flame proving period tFS1 23 0 – 25 s 0 s 
Main burner safety time on start-up tSA2 24 3; 5 s 
Main burner flame proving period tFS2 25 0 – 25 s 0 s 
Air valve control 30 0; 2; 3 0
Air valve can be activated externally on start-up 31 0; 1 0
Air valve closed/can be activated in the event of malfunction 32 0; 1 1
High temperature operation** 33 2; 3
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PFU 780 · Edition 02.12 19
Description Parameter Value range Factory default
setting Adjustable*
Manual mode limited to 5 minutes 34 0; 1 1
UVS check (1 x in 24 hours) 35 0; 1 0
Low fire over run time 36 0; 5; 15; 25 s 0 s 
Purge 42 0; 1 1
Multi-flame control 45 0; 1 0
Password 50 0000 – 9999 1234 
* Adjustable using BCSoft software and a PC opto-adapter
** Please quote in your order.
0 = Function inactive
1 = Function active
On parameterisation, ensure that the program sequence
started matches the application. Select the parameters so that
the burner can restart as intended in all operating phases.
4.1 Scanning the parameters
During operation, the 7-segment display shows the program
status.
The flame signal and all following parameters of the PFU can
be scanned one after the other by repeatedly pressing the
Reset/Information button (for 2 s).
In the event of a fault, the PFU halts the program run, the
display blinks and it then displays the cause of the fault in
coded form.
Parameters

PFU 780 · Edition 02.12 20
4.2 Flame control
4.2.1 Flame signal, pilot burner
Parameter 01
Flame signal of the pilot burner, display in µA, measuring
range: 0 – 30 µA.
4.2.2 Flame signal, main burner
Parameter 02
Flame signal of the main burner, display in µA, measuring
range: 0 – 30 µA.
4.2.3 Program status when the most recent fault occurred
Parameter 03
Program status when the most recent fault occurred
This indicates the program status in which the last burner fault
occurred (e.g. the unit indicates that a flame simulation has
been detected with a blinking 01 ).
In parameter 03, it is now shown which program position the
unit was in when the fault was detected (waiting time 01 or
standby 00 ).
Result: A flame simulation was detected during the waiting
time or standby.
4.2.4 Switch-off threshold of the flame amplifier
Parameter 04, pilot burner switch-off threshold
Parameter 05, main burner switch-off threshold
The sensitivity at which the burner control unit still detects a
flame can be set between 1 and 20 μA.
Example: In the case of UV control with the UV sensor UVS,
the signal of the burner to be monitored is influenced by other
burners.
The set value can be incremented in parameter 04 so that only
the flame of the system’s “own” burner is detected.
The measured flame signal of the system’s “own” burner should
be at least 3 μA (empirical value) higher than the set switch-
off threshold.
Parameters