Krom Schroder PFU 780 Technical Information

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Burner control unit PFU 780

Technical Information · GB

6 Edition 02.12

AGA

• 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

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 t

4.5 Behaviour during start-up ......................30

4.5.1 Safety time on start-up tSA ......................... 30

4.5.2 Flame proving period t

4.5.3 Minimum combustion time t

. . . . . . . . . . . . . . . . . . . 29

...........................31

......................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 t

4.7.9 Behaviour of the air valve in the event of a fault lock-out 44

after a normal shut-down ... 43

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 t

...................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 2

= To be continued

▼

Table of contents

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 t

12.4 Flame simulation/Flame simulation delay time t

12.5 Safety time during operation t

...............................67

. 67

.............. 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 PFH

12.17 Mean time to dangerous failure MTTF

...........69

..........69

Feedback ......................................70

Contact........................................70

PFU 780 · Edition 02.12 3

= To be continued

▼

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.

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 visualisation system of the input and output signals and the error

history. 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.

PFU 780 · Edition 02.12 4

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 5

VR..L

VAG

SPS PLC CPE

L1, N, PE

ϑ1

ϑ2

02–04 02–04 06–08 06–08

VBY

PFU 780

10e

2c 4c

18a

26e 10c

22e

22a

28c 16c 18e

6a 6e

2e 4e

14a 30e 10a

TZI

ϑ1

ϑ2

µC

Application

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 automatically 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.

PFU 780 · Edition 02.12 6

VR..R

VAG

SPS PLC CPE

L1, N, PE

VBY

PFU 780

10e

2c 4c

18a

26e 10c

22e

22a

28c 16c 18e

6a 6e

2e 4e

14a 30e 10a

TZI

04 02–04 06–08 06–08

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 7

VAG

VBY

SPS PLC CPE

L1, N, PE

BV+IC

PFU 780

10e

2e 4e

2c 4c

6a 6e

26a

26e 10c

TZI

22a

28c

16c 18e

14a

18a

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 operating 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 8

STWL1>750 °C

µC

PFU 780..D

18a

26a

22a

µC

PFU 780..D

18a

26a

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 temperature the ﬂame must be controlled by conventional methods. When the working temperature has exceeded 750°C, the safety temperature monitor (STW) takes over the indirect ﬂame control.

PFU 780 · Edition 02.12 9

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

AGA approved

AGA

Australian Gas Association, Approval No.: 5597 www.aga.asn.au/product_directory

Factory Mutual Research Class: 1997. Suitable for applications pursuant to NFPA 86.

www.approvalguide.com

PFU 780 · Edition 02.12 10

L1 (L1)

N (L2)

24 V

0 V

30e

26e

22a

30a

20c 230 V

28c

26a

18a

ϑ1

10e

12e

ϑ2

14a

14e

10a

12a

10c

12c

32c 24c

PFU 780

sk1

µC

22e

16c

18e

3.1 Connection diagram

For cable selection and wiring, see page 49 (Project planning information).

3.1.1 PFU 780

For the explanation of symbols, see page 66 (Legend).

6a 6e

max. 1 A, 24 V

3 Function

26a

28c N

18a

26a

28c

UVS

18a

1 2

20c

24c

PFU 780 · Edition 02.12 11

Function > Connection diagram

L1 (L1)

30e

26e

22a

PFU 780..K2

sk1

3.1.2 PFU 780..K2

22e

16c

18e

As a replacement unit for burner control unit PFU 798. For the explanation of symbols, see page 66 (Legend).

N (L2)

24 V

0 V

26a

ϑ2

30a

32c 24c

20c 230 V

28c

26a

18a

ϑ1

10e

12e

14a

14e

10a

12a

10c

12c

28c N

µC

28c

26a

18a

UVS

18a

1 2

20c

24c

max. 1 A, 24 V

PFU 780 · Edition 02.12 12

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 t

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 tB

starts to elapse (P20)

Function

▼

PFU 780

If the air valve control is used, the unit offers the following additional functions:

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

In start-up position, the air valve can be opened for cooling (display

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-

Using parameter 31, it can be determined whether the air valve can be activated externally dur- ing start-up (display

cuitry or of the ﬂame sensors, the burner can be started. The pilot burner start-up is activated via the signal input “Startup 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 tZ is constant. If

The air valve can be set to open

together with V1 (display parameter 30.

) via

a ﬂame is detected during the safety time t

, the ﬂame proving period t

SA1

after the safety time t

SA1

has elapsed.

starts

FS1

If the pilot burner has been started successfully 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.

PFU 780 · Edition 02.12 13

If no ﬂame detected:

next start-up attempt (P10)

or fault lock-out

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 ϑ2 signal

Wait until

min. burner pause time t

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 tB

starts to elapse (P20)

▼

Function > PFU 780 program sequence

The air valve can be set to open together with V1 (display parameter 30.

) via

The PFU coordinates the correct program

run for the pilot and main burners. The main burner can be started via the signal 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 starts after the safety time t

, the ﬂame proving period t

SA2

FS2

has elapsed. If the main burner has been started successfully and its ﬂame has stabilised, the operation signalling contact (terminals 6a/6e) closes.

Start-up of the pilot burner without ﬂame signal

If no ﬂame is detected during the safety time t

, either a fault lock-out occurs

SA1

or up to three further start-up attempts occur. (Parameter 10, “Pilot burner startup attempts”).

PFU 780 · Edition 02.12 14

The air valve can be set to open with V2 or to be activated ex- ternally (display eter30.

) via param-

If no ﬂame detected:

next start-up attempt (P11)

or fault lock-out

Normal shut-down

via ϑ signal for

pilot and main burners

If min. combustion time t

has elapsed:

Operation signalling contact

opens,

V1 and V2 close,

min. burner pause time tBP

starts to elapse (P21)

In the event of ﬂame failure:

restart or fault lock-out

Operating signal

Main burner closes

Flame proving period

FS2

running (P25)

In the event of ﬂame failure:

restart or fault lock-out

Function > PFU 780 program sequence

The air valve can be set to open with V2 or to be activated exter- nally (display

30.

The air valve can be set to open with the operating signal or to be activated externally (display via parameter 30.

) via parameter

)

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

, either a fault lock-out occurs

SA2

or up to three further start-up attempts occur. (Parameter 11, “Main burner startup 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”).

PFU 780 · Edition 02.12 15

Function

▼

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.

Program status

Start-up position/standby Cooling Waiting time/Pause time Safety time on start-up, pilot burner Flame proving period, pilot burner Operation, pilot burner Waiting time, main burner Safety time on start-up, main burner Flame proving period, main burner Operation, main burner Purge Air valve High temperature operation**

DISPLAY

. .

Fault message (blinking*)

Flame simulation, pilot burner Start-up without ﬂame signal, pilot burner Flame failure during ﬂame proving period, pilot burner Flame failure during operation, pilot burner Flame simulation, main burner Start-up without ﬂame signal, main burner Flame failure during ﬂame proving period, main burner Flame failure during operation, main burner

Faulty remote reset

Supply voltage too low

Faulty parameterisation

Short-circuit on a valve output

PFU 780 · Edition 02.12 16

Function > Program status and fault messages

Program status

DISPLAY

* In Manual mode, two dots will blink on the display in program status 01 – 08. ** Optionally available.

Fault message (blinking*) Short-circuit on ignition or valve output

Safety interlock failure

Permanent reset

Time between two start-ups is too short

PFU 780 · Edition 02.12 17

4 Parameters

▼

Description Parameter Value range

Factory default

setting 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 t

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 t Minimum burner pause time t

Pilot burner safety time on start-up t Pilot burner ﬂame proving period t

FS1

Main burner safety time on start-up t Main burner ﬂame proving period t

SA1

24 3; 5 s

SA2

FS2

20 25 s t

21 0 – 250 s 0 s

22 3; 5; 10 s 23 0 – 25 s 0 s

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

Adjustable*



PFU 780 · Edition 02.12 18

Parameters

Description Parameter Value range

Factory default

setting 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.

Adjustable*



PFU 780 · Edition 02.12 19

Parameters

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

In parameter 03, it is now shown which program position the unit was in when the fault was detected (waiting time standby

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 switchoff threshold.

PFU 780 · Edition 02.12 20

06 07 0800

SA2tFS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

ϑ1

ϑ2

SA1

0402 03

FS1

Parameters > Flame control

▼

4.2.5 High temperature operation with PFU..D

Parameter 33 Operation of ﬁring systems at temperatures above 750°C. The PFU features a safety-relevant DI input (Digital Input). This input

The voltage may be applied to the DI input (terminal 22a) so as to activate High temperature mode only when the temperature at the furnace wall has exceeded 750°C. The PFU starts the

burner as usual, without monitoring the presence of the ﬂame. supports the “High temperature operation” function. If ﬁring systems are operated above 750°C, the system is considered to be a high temperature equipment (see EN746-2). Flame control must be in operation until the furnace wall temperature has exceeded 750°C. Note the requirements of the Standards!

Flame control can be dispensed with during high temperature operation to improve the system availability. This means that no incorrect ﬂame signals, e.g. signals from a UV sensor which are interpreted as extraneous signals due to reﬂection of UV radiation, may lead to faults.

When the DI input is activated, the burner control unit reverts to High temperature mode. This means: the PFU operates without evaluation of the ﬂame signal. The safety function of the device-internal ﬂame control system is placed out of operation.

In High temperature mode, the gas valves are opened without ﬂame control.

If the temperature in the furnace chamber drops below 750°C,

the DI input must be disconnected from the electrical power

supply and the furnace must be operated with the internal

ﬂame control system. The precondition for high temperature operation is that an external ﬂame safeguard ensures the presence of the ﬂame in fail-safe manner indirectly via the temperature. For this purpose, we recommend a safety temperature monitor with twin thermocouple (DIN 3440). Sensor discontinuity, sensor short-circuit, failure of a component or mains failure must set the installation to a safe state.

PFU 780 · Edition 02.12 21

06 07 0808

SA2tFS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

V2 2

ϑ1

ϑ2

SA1

0402 0301

FS1

2a–4a

06 07 0808

SA2tFS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

V2 2

ϑ1

ϑ2

SA1

0402 0301

FS1

2a–4a

Parameters > Flame control > High temperature operation with PFU..D

▼

The PFU then responds, depending on setting: Parameter 33 = 1

If the ﬂame fails during high temperature operation, the ready contact opens for the duration of the ﬂame failure (FA).

When High temperature mode is ended, the PFU switches off the burner and restarts with ﬂame simulation check (recom- mended in the case of UV control with UVS).

Parameter 33 = 2

When High temperature mode is ended, the PFU switches off

the burner and restarts with ﬂame simulation check (recom-

mended in the case of UV control with UVS).

PFU 780 · Edition 02.12 22

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

V2 2

ϑ1

ϑ2

04 04

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

V1 1

ϑ1

ϑ2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

V2 2

ϑ1

ϑ2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

22a

ϑ1

ϑ2

2a–4a

Parameters > Flame control > High temperature operation with PFU..D

Parameter 33 = 3

When High temperature mode is ended, the burner remains in operation and the PFU performs ﬂame control again (recommended in the case of ionisation control or UV control with UVD).

If no ﬂame signal is present when High temperature mode is ended, the burner control unit performs a fault lock-out, regardless of parameter 33.

Fault, pilot burner

Fault, main burner

Parameter 33 = 4

If the ﬂame fails during high temperature operation, the ready

PFU 780 · Edition 02.12 23

contact is opened for the duration of the ﬂame failure.

When High temperature mode is ended, the burner remains

in operation and the PFU performs ﬂame control again

(recommended in the case of ionisation control or UV control

with UVD).

Parameters > Flame control

4.2.6 UVS check

Parameter 35 An automatic restart of the burner control unit can be activated every 24 hours via this parameter. The time starts each time the start-up signal (ϑ) is applied.

Parameter 35 = 0: Unlimited burner operation. Parameter 35 = 1: An automatic restart is activated once every

24hours. It must be ensured in this case that the program sequence

started matches the application. This parameter may be set in this way only if the burner can restart as intended in all operating phases.

PFU 780 · Edition 02.12 24

ϑ1

ϑ2

88 02–04 06–08 04 06–08 04

Parameters

4.3 Pilot and main burner monitoring

Burner control unit PFU 780 for pilot and main burner combi- nation of unlimited capacity.

Pilot burner: single-stage-controlled. Main burner: modulating or stage-controlled. The burner control unit PFU 780 has separate start-up signal

inputs for the pilot burner (terminal 10e) and the main burner (terminal 14a). The burner control unit coordinates the program run (the interplay) of both burners. If required, the main burner can be started once the pilot burner has reached its operating position. Beneﬁt: The time for starting up the main burner can be reduced as low as its safety time. By using two ﬂame ampli- ﬁers, the pilot and main burners can be monitored separately.

The PFU 780 can also be used on indirectly ignited surface burners with end point monitoring.

Three different operating modes are possible:

Permanent pilot burner

For applications which require a high system availability or where a continuously burning ﬂame is necessary. The pilot burner is ignited once and remains constantly in operation. The main burner is controlled separately.

Intermittent pilot burner

88 02–04 06–08 00 02–04 06–08 00

Pilot and main burners are controlled with one start-up signal

(terminals 10e and 14a in parallel). The main burner starts

automatically after the operating signal from the pilot burner

has been detected. Operation is terminated simultaneously

for both burners.

Interrupted pilot burner

88 02–04 06–08 02–04 06–08

ϑ1

ϑ2

The pilot burner is switched off during the main burner safety

time t

. This type of ﬂame control is required if no distinc-

SA2

tion can be made between the ﬂame signals of the pilot and

main burners (e.g. if both burners can be monitored with a

single UV sensor). If the start-up signal for the pilot burner is

applied continually, the pilot burner restarts immediately after

the main burner has been switched off.

PFU 780 · Edition 02.12 25

Parameters > Pilot and main burner monitoring

SA1

04 06 07 08 02 03 00

FS1

SA2

FS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

ϑ1

ϑ2

4.3.1 Permanent pilot burner Parameter 16 = 1

Operating mode: Permanent pilot burner

In the “Permanent pilot burner” operating mode, the pilot

burner remains in operation until its start-up signal drops.

If this parameter is activated (P16 = 1), both ﬂames are con-

trolled independently in the case of pilot and main burner

monitoring.

PFU 780

VBY

VAG

VR..R

SPS

PLC CPE

TZI

Operating mode: Intermittent pilot burner

Start-up as in the illustration “Permanent pilot burner” with

the difference being that the start-up signal for pilot and main

burners is applied synchronously and that immediately after

the ﬂame proving period t

, the main burner is started.

FS1

PFU 780 · Edition 02.12 26

Parameters > Pilot and main burner monitoring

SA1

04 06 07 08 02 03 00

FS1

SA2

FS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V1 1

ϑ1

ϑ2

4.3.2 Interrupted pilot burner Parameter 16 = 0

Operating mode: Interrupted pilot burner

If parameter 16 = 0, the pilot burner is switched off once the

safety time t

can be connected to terminals 18a or 26a.

The pilot burner is switched off after the main burner safety

time t

SA2

has elapsed. In this setting, the ﬂame signal

SA2

has elapsed.

VR..R

PFU 780

VAS

VAG

SPS

PLC CPE

TZI

PFU 780 · Edition 02.12 27

26a 16c 18e 2c–4c

10e

26e

30a

28c

2e–4e

V1 V2

ϑ1

ϑ2

88 00 02 06

ϑ1

ϑ2

88 00 01 05

ϑ1

ϑ2

88 00 02 06

ϑ1

ϑ2

88 00 01 05

Parameters

4.4 Behaviour in start-up position/standby

4.4.1 Flame simulation check in start-up position/standby

Parameter 15

Flame simulation check depending on parameter 16 (Pilot

burner operating mode):

Parameter 15 = 1, Parameter 16 = 1

This deﬁnes the instant for the ﬂame simulation check.

Parameter 15 = 0, Parameter 16 = 1

If the PFU notices an extraneous signal during the ﬂame simu- lation check, it starts the ﬂame simulation delay time tLV (25s). If the extraneous signal is discontinued during this period,

Parameter 15 = 1, Parameter 16 = 0

the burner can start up. Otherwise, a fault lock-out occurs.

blinks on the display if an extraneous signal is detected by the pilot burner and 5 blinks if an extraneous signal is detected by the main burner.

Parameter 15 = 0: The ﬂame simulation check is conducted after applying the start-up signal (ϑ) during the waiting timetW.

Parameter 15 = 0, Parameter 16 = 0

Parameter 15 = 1: The ﬂame simulation check is conducted provided no start-up signal (ϑ) is applied (during the so-called start-up position/standby). This allows fast start-up of the burner since there is no waiting time tW.

The burner must have been switched off for at least 4s before start-up in order for the ﬂame simulation check to be con- ducted correctly.

PFU 780 · Edition 02.12 28

SA2

88 08 06 07 08

FS2

7 9

18-19

14 V2

16-17

05 04

28-29

Parameters > Behaviour in start-up position/standby

4.4.2 Minimum burner pause time tBP

Parameter 21 Programmable time between 0 and 250 s.

The time should be set such that the system can be moved to ignition position, i.e. butterﬂy valves can be closed and, possibly, gas can be ﬂared off, before a restart occurs.

See examples of application Stage-controlled main burner with alternating pilot burner and Stage-controlled main burner with permanent pilot burner.

The pause time has an effect on the behaviour of the main burner only. Background: The pilot burner is only used in singlestage operation.

An immediate restart of the main burner after a normal shut- down, a start-up attempt, restart, cooling or purging is pre- vented by the pause time. The pause time starts when the air valve is switched off. If a start-up signal (ϑ2) is applied before expiry of this time, the start-up is delayed until the end of the pause time.

After the pause time, the burner is started if the start-up signal (ϑ) is applied.

The minimum burner pause time t

serves to adapt the pro-

gram sequence to the requirements of the application.

PFU 780 · Edition 02.12 29

SA1

04 02 03 00

26a 16c 18e 2c–4c

10e

26e

30a

28c

2e–4e

ϑ1

SA1

04 06 07 08 02 03 00

FS1

SA2

FS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V1 1

ϑ1

ϑ2

Parameters

4.5 Behaviour during start-up

4.5.1 Safety time on start-up tSA

Pilot burner

Parameter 22

Safety time on start-up t

for the pilot burner.

SA1

Main burner

Parameter 24

Safety time on start-up t

for the main burner.

SA2

PFU 780 · Edition 02.12 30

SA1

04 02 03 00

26a 16c 18e 2c–4c

10e

26e

30a

28c

2e–4e

ϑ1

SA1

04 06 07 08 02 03 00

FS1

SA2

FS2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V1 1

ϑ1

ϑ2

04 06 07

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

2e–4e

6a–6e

ϑ1

ϑ2

Parameters > Behaviour during start-up

4.5.2 Flame proving period tFS Pilot burner

Parameter 23

Main burner

Parameter 25

4.5.3 Minimum combustion time t

Parameter 20 Programmable time to maximum 25 s during which the main burner remains in operation. In the case of brief activation of the start-up signal input (ϑ2) (e.g. with a pulse), the combustion time tB is started, and the main burner remains in operation for at least this period.

Programmable time between 0 and 25 s.

This time elapses before the PFU starts the next program step

so as to give the ﬂame time to stabilise.

PFU 780 · Edition 02.12 31

02 00

26a 16c 18e 2c–4c

10e

26e

30a

28c

2e–4e

V1 V2

ϑ1

SA1

02 00

SA1

26a 16c 18e 2c–4c

10e

26e

30a

28c

2e–4e

V1 V2

ϑ1

Parameters > Behaviour during start-up

4.5.4 Burner start-up attempts

Pilot burner

Parameter 10 This indicates the number of possible start-up attempts of the burner.

If no ﬂame is detected during start-up, either a fault lock-out is performed or further start-up attempts in accordance with EN 746-2 occur.

Pursuant to NFPA 86, only one start-up attempt is permitted in the event of ﬂame failure during start-up. For units approved by FM Approval (see type label), it is only possible to select one start-up attempt.

1 start-up attempt

Parameter 10 = 1

2 or 3 start-up attempts

Parameter 10 = 2, 3

If several start-up attempts are set and if the PFU detects a ﬂame failure during start-up, it closes valve V1 after the safety time t

has expired and attempts to start up again. After the

SA1

last programmed start-up attempt has been completed, the burner control unit conducts a fault lock-out. The display blinks and shows the cause of the fault.

If no ﬂame forms during start-up, a fault lock-out is performed after expiry of time tSA. The display blinks and shows the cause of the fault.

PFU 780 · Edition 02.12 32

SA1

04 06 02 03 00

FS1

SA2

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

ϑ1

ϑ2

SA2

SA1

04 06 02 03 00

FS1

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

ϑ1

ϑ2

Parameters > Behaviour during start-up > Burner start-up attempts

Main burner

Parameter 11 This indicates the number of possible start-up attempts of the main burner.

In accordance with EN 746-2, three start-ups are permitted in speciﬁc cases in the event of ﬂame failure during start-up, if the safety of the installation is not impaired. Note the require- ments of the Standards! If no ﬂame is detected during start-up, either a fault lock-out is performed or further start-up attempts in accordance with EN 746-2 occur.

1 start-up attempt

Parameter 11 = 1

2 or 3 start-up attempts

Parameter 11 = 2, 3

If several start-up attempts are set and if the PFU does not detect a ﬂame signal during start-up, it closes valve V2 after the safety time t

has expired and attempts to start up again.

SA2

After the last programmed start-up attempt has been completed, the burner control unit conducts a fault lock-out. The display blinks and shows the cause of the fault.

If no ﬂame forms during the start-up of the main burner, a fault lock-out is performed after expiry of time t blinks and shows the cause of the fault.

PFU 780 · Edition 02.12 33

. The display

SA2

26a 16c 18e

2c–4c

10e

26e

30a

28c

2e–4e

ϑ1

Parameters

▼

4.6 Behaviour during operation

4.6.1

Safety time during operation tSB for pilot and main burners

Parameter 14 This indicates the safety time during operation tSB for valves V1 and V2. The default in accordance with EN 298 is 1 s. The PFU has also the available option of a safety time during operation tSB of 2 s. Prolonging the time increases the installation avail- ability in the case of brief-duration signal fades (e.g. fades of the ﬂame signal). In accordance with EN 746-2, the safety time

4.6.2 Fault lock-out or restart, pilot burner

Parameter 12 This parameter determines whether the PFU starts a one-off restart or performs an immediate fault lock-out for the burner after an installation fault such as a ﬂame failure or failure of air ﬂow (see also Project planning information).

Immediate fault lock-out following ﬂame failure

Parameter 12 = 0: Pilot burner fault lock-out.

of the installation during operation (including closing time of the valves) may not exceed 3 seconds (note the requirements of the Standards).

After a fault lock-out, the burner control unit can be reset, either with the button on the front panel or using an external button. Several burner control units can be reset in parallel using the external button.

The PFU cannot be reset by mains failure. The fault signalling contact does, however, open as soon as the mains voltage fails.

See also parameter 32, Behaviour of the air valve in the event of a fault lock-out.

PFU 780 · Edition 02.12 34

SA1

04 04 03 01

FS1

>2 s

26a 16c 2c–4c

10e

26e

30a

28c

2e–4e

ϑ1

Parameters > Behaviour during operation > Fault lock-out or restart, pilot burner

Restart following ﬂame failure

Parameter 12 = 1: Restart following ﬂame failure.

If the PFU detects a ﬂame failure after a minimum operating time of 2 s, the valves are closed and the operation signalling contact is opened within time tSB.

The burner control unit now attempts to restart the burner once. If the burner does not function, a fault lock-out occurs. The display blinks and shows the cause of the fault.

In accordance with EN 746-2, a restart may be conducted only if the safety of the installation is not impaired. Restart is recommended for burners which occasionally display unstable behaviour during operation.

The precondition for a restart is that activation of the restart allows the burner to restart as intended (in all operating phases). In this case, it must be ensured that the program sequence started by the PFU matches the application.

PFU 780 · Edition 02.12 35

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V1 1

ϑ1

ϑ2

Parameters > Behaviour during operation

▼

4.6.3 Fault lock-out or restart, main burner

This parameter determines whether the PFU starts a one-off restart or performs an immediate fault lock-out for the main burner after a ﬂame failure (see also Project planning infor- mation).

Immediate fault lock-out following ﬂame failure

Parameter 13 = 0: Main burner fault lock-out

The PFU cannot be reset by mains failure. The fault signalling contact does, however, open as soon as the mains voltage fails.

See also “Behaviour of the air valve in the event of a fault lock-out”.

After a ﬂame failure, the burner control unit performs a fault lock-out within the safety time during operation tSB. This in- volves disconnecting the power from the gas valves and the ignition transformer. The fault signalling contact closes, the display blinks and shows the current program status (see table “Program status and fault messages”).

PFU 780 · Edition 02.12 36

SA2

FS2

>2 s

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V2 2

ϑ1

ϑ2

Parameters > Behaviour during operation > Fault lock-out or restart, main burner

Restart following ﬂame failure

Parameter 13 = 1: Restart following ﬂame failure.

If the PFU detects a ﬂame failure after a minimum operating time of 2 s, valve V2 is closed and the operation signalling contact is opened within time tSB.

The burner control unit now attempts to restart the main burner once. If the burner does not function, a fault lock-out occurs. The display blinks and shows the cause of the fault.

PFU 780 · Edition 02.12 37

Parameters

4.7 Air valve control PFU..L

Parameter 30, Behaviour of the air valve during operation Parameter 31, Behaviour of the air valve during start-up Parameter 32, Behaviour of the air valve in the event of a

fault lock-out The PFU..L features an adjustable air valve control. The display

shows that purging is currently being carried out with

indicates that the air valve is being activated for cooling

or heating. The PFU..L supports the following functions:

– Purge – Cooling in start-up position/standby – Switching of the burner between low and high burner out-

put during operation via the air valve

– To start up the burner as intended, external activation of

the air valve can be blocked during start-up (prevents

synchronisation problems between the PFU and the cen-

tral control system) – Controlling the air valve so that it – opens with valve V2, – opens once the main burner has reached its operating

position – Low ﬁre over run time t

after a normal shut-down

P 0

4.7.1 Purge

Parameter 42 = 0: The air valve is closed when voltage is applied to terminal 30e.

Parameter 42 = 1: The air valve is opened when voltage is applied to terminal 30e.

In the case of multiple burner applications, burners with mechanical combustion air supply are used. The air for combus-

tion and pre-purge is supplied by a central fan controlled by a separate logic. This logic determines the purging time.

The PFU..L supports centrally-controlled pre-purge or postpurge. The PFU..L is informed that purging is currently being performed by input 30e. It then opens the air valve, regardless of the status of the other inputs (purging has priority). The display indicates

PFU 780..K2: For purging, the safety interlock (limits) must activate input 26e and input 30e of the PFU.

4.7.2 Cooling in start-up position/standby

The air valve can be activated externally via input 10a for cooling in the start-up position. During activation of the air valve the display shows being carried out.

4.7.3 Burner start

Parameters 30 and 31 determine the behaviour of the air valve during burner start.

P 0

A 0

, indicating that cooling is currently

PFU 780 · Edition 02.12 38

00 A0 00

SA2

A807

FS2

SA1

FS1

10a 22e

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V1 1

ϑ1

ϑ2

PFU 780

SPS PLC CPE

VR..R

VAG

TZI

VAS

Parameters > Air valve control PFU..L

4.7.4 Air valve opens in the case of external activation (not during start-up)

Parameter 30 = 0: The air valve opens if it is activated externally by input 30e.

Parameter 31 = 0: The air valve remains closed during start-up even if it is activated externally.

These settings are required on burners on which the gas/air ratio is controlled via a pneumatic link and which also need to be started at low ﬁre, e.g. on two-stage-controlled burners. In this case, activation of the air valve during burner start via input 10a must be prevented.

External control allows switchover between low ﬁre and high ﬁre during operation.

The air valve can be activated externally via input 10a for cooling the burner in the start-up position/standby.

PFU 780 · Edition 02.12 39

00 A0 00

SA2

A8 A7

FS2

SA1

FS1

10a 22e

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V1 1

ϑ1

ϑ2

Parameters > Air valve control PFU..L

4.7.5 Air valve opens in the case of external activation (even during start-up)

PFU 780..L

VAS 1

VAG

TZI

Parameter 30 = 0: The air valve opens if it is activated externally via input 10a.

Parameter 31 = 1: The air valve can be activated even during start-up.

These settings may be selected only if the burner can start with full air capacity.

The air valve can be activated externally via input 10a for cooling the burner in the start-up position/standby.

VAS

PFU 780 · Edition 02.12 40

00 A0

SA2

A8 A7

FS2

SA1

FS1

10a 22e

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

V2 2

ϑ1

ϑ2

Parameters > Air valve control PFU..L

4.7.6 Air valve opens with valve V2

PFU 780..L

VBY

VAG

TZI

Parameter 30 = 2: The air valve opens simultaneously with valve V2. Application: Single-stage-controlled main burner is switched ON/OFF via the ϑ input.

The air valve can be activated externally via input 10a for cooling the burner in the start-up position/standby.

SPS PLC CPE

VR..R

PFU 780 · Edition 02.12 41

A8 07

10a 22e

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

ϑ1

ϑ2

Parameters > Air valve control PFU..L

4.7.7 Air valve opens with operating signal

PFU 780..L

VBY

VAG

SPS

PLC CPE

TZI

Parameter 30 = 3: The air valve opens simultaneously with the operating signal. Application: Two-stage-controlled main burner is switched ON/OFF via the ϑ input.

The air valve can be activated externally via input 10a for cooling the burner in the start-up position/standby.

VR..R

PFU 780 · Edition 02.12 42

22e

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

28c

2e–4e

6a–6e

ϑ1

ϑ2

Parameters > Air valve control PFU..L

4.7.8 Low ﬁre over run time tKN after a normal shut-down

PFU 780..L

VG..N

VR..R

GIK..B

VAS 1

TZI

SPS PLC CPE

Parameter 36 Settings: 0; 3; 5; 10; 15; 25 or 60 (low ﬁre over run time in

seconds) This parameter is applicable to systems with a pneumatic link

between gas and air and On/Off control. Parameter 36 = 0 (low ﬁre over run time t

= 0 s):

Without low ﬁre over run, the gas side is closed immediately owing to the quick-closing gas valve in the case of On/Off control. The air side closes more slowly. The air ﬂowing in during the closing time increases the O2 content in the combustion chamber.

Parameter 36 = 3; 5; 10; 15; 25 or 60 (low ﬁre over run time t

= 3, 5, 10, 15, 25 or 60 s):

The air valve closes slowly after the activation signal has been switched off. The gas valve remains open for tKN. This means that the burner, after deactivation of the main burner start-up signal (ϑ2), is initially adjusted down to low ﬁre and then switched off completely.

Using the low ﬁre over run function reduces the O

content in

the furnace atmosphere. Flame control is still operational. Can be used only in the case

of pneumatic link and On/Off control. It must be ensured that no excess gas occurs.

The low ﬁre over run time has an effect on the behaviour of the main burner only.

Background: The pilot burner is only used in single-stage operation.

PFU 780 · Edition 02.12 43

Parameters > Air valve control PFU..L

4.7.9

Behaviour of the air valve in the event of a fault lock-out

Parameter 32: This determines whether the air valve can be activated in the case of a fault lock-out.

Parameter 32 = 0: The air valve is closed in the event of a fault. It cannot be activated externally via terminal 10a.

Parameter 32 = 1: The air valve can be activated externally via input 10a even during a fault, e.g. for cooling.

PFU 780 · Edition 02.12 44

Parameters

4.8 Manual operation

For convenient setting of the burner or analysing faults. The parameter display is not available in Manual mode.

Manual mode can be accessed only if the unit was not in Fault state before switching off. The following times/functions are not active in Manual mode: start-up attempts, restart, minimum combustion time and cycle lock.

If the Reset/Information button is pressed for 2 s during switch- on, the PFU reverts to Manual mode. Two dots blink on the display.

In this operating mode, the burner control unit operates inde- pendently of the status of the inputs (apart from the pre-purge input and the safety interlocks. These are of higher priority and will be processed ﬁrst).

Each time after the button is pressed again, the PFU moves to the next section of the program sequence and stops there. After approx. 3 s, the ﬂame signal will be displayed instead of the program parameter. Brieﬂy pressing the Reset/Informa- tion button (< 1 s) displays the relevant Manual mode step. If there is ﬂame simulation during the start-up, the ﬂame signal is displayed immediately.

On units with air valve control, the air valve can be opened and closed repeatedly by pressing the button during operation.

Manual mode can be terminated by switching off the PFU (On/Off button).

4.8.1 Manual mode limited to 5 minutes

Parameter 34: Parameter 34 determines when Manual mode is terminated.

Parameter 34 = 0: Manual mode is not limited in time. If this function has been selected, operation of the furnace may be continued manually in the event of failure of the central control system.

Parameter 34 = 1: Manual mode ends automatically ﬁve minutes after the last time the button was pressed. The PFU then moves abruptly back to start-up position/standby.

PFU 780 · Edition 02.12 45

Parameters

4.9 Password

Parameter 50: (Four-digit) password saved to protect parameter settings. To prevent unauthorised changes to parameter settings, a password is stored in parameter 50. Changes to parameter settings can only be made once this number has been entered. The password can be changed using BCSoft.

Note the effect of parameter settings on the safe functioning of your system.

The password set at the factory can be found in the delivery note supplied.

PFU 780 · Edition 02.12 46

5 Selection

5.1 Calculating the safety time tSA

PFU 780 · Edition 02.12 47

Selection

* If “none”, this speciﬁ cation is omitted.

5.2 Selection table

Type L T N D* U* K2* PFU 780



= standard,  = available

Order example

PFU 780LT

     

5.2.1 Type code

Code Description L Air valve control

Mains voltage T 220 – 240 V~, -15/+10 %, 50/60 Hz N 110 – 120 V~, -15/+10 %, 50/60 Hz

U* Preparation for UV sensor for continuous operation UVD 1 K2* Compatible with PFU 798

to interrupt ﬂ ame control

Digital input

PFU 780 · Edition 02.12 48

6 Project planning information

6.1 Cable selection

Use mains cable suitable for the type of operation and com- plying with local regulations. Do not route PFU cables in the same cable duct as frequency converter cables or cables emitting strong ﬁelds.

6.1.1 Ignition cable

Use unscreened high-voltage cable, see page 55 (Acces- sories). Cable length: max. 5 m, recommended < 1 m. Screw the ignition cable securely into the ignition transformer and run to the burner by the shortest possible route.

The longer the ignition cable, the lower the ignition capacity. Only use radio interference suppressed electrode adapters (with 1 kΩ resistor) for ignition electrodes, see see page 55 (Accessories) . Do not lay UV/ionisation cable and ignition cables together and lay them as far apart as possible.

6.1.2 Ionisation cable

Use unscreened high-voltage cable, see page 55 (Acces- sories) . Cable length: max. 100 m. Avoid external electrical interference. Install as far as possible from mains and igni- tion cables and interference from electro-magnetic sources. If possible, do not lay in a metal conduit. Several ionisation cables can be routed together.

6.1.3 UV-Leitung

Cable length: max. 100 m. Avoid external electrical interference. Install as far as possible from mains and ignition cables and interference from electro-magnetic sources. If possible, do not lay in a metal conduit. Several UV cables can be routed together.

6.2 Ignition electrode

6.2.1 Electrode gap

Gap between electrode and burner earth: 2 mm ± 0.5mm.

6.2.2 Star electrodes

We recommend using 7.5kV ignition transformers on burners with star electrodes.

PFU 780 · Edition 02.12 49

Project planning information

04 06 07

26a

16c

18e

2c–4c

18a

14a

10e

26e

30a

2e–4e

6a–6e

ϑ1

ϑ2

6.3 Minimum combustion time

Even if the start-up signal (ϑ) is applied only brieﬂy, the time set under parameter 20 elapses before the burner control unit shuts down the burner or signals a fault. To stabilise the burner operation, a minimum combustion time can be set independently of the central control system. If the start-up signal (ϑ) drops once the second safety time t to elapse, the burner remains in operation for at least time tB. The minimum combustion time tB starts to elapse following controller enable. If the start-up signal drops before the second safety time t

, e.g. during pre-purge, the control unit reverts

SA2

directly to standby and the burner is not ignited. The signal inputs for the pilot/main burner start-up signal can-

not be used for a safety shut-down because the unit controls the valves until the minimum combustion time has elapsed.

has started

SA2

6.4 Safety interlocks (Limits)

The limiters in the safety interlock (linking of all the relevant safety control and switching equipment for the use of the application, e.g. safety temperature limiter, minimum and maximum gas pressure, tightness control) must isolate terminal 26e from the voltage supply. If the safety interlock is interrupted, this is indicated by a blinking

on the display.

If the safety interlocks fail, an immediate program abort with switch-off of all outputs occurs (even during the safety time). If the safety interlocks are operational again or the unit is switched back on, the program run is restarted in standby.

6.5 Emergency stop

6.5.1 In the event of ﬁre or electric shock

If there is a risk of ﬁre, electric shock or similar, inputs L1, N and 26e (safety interlocks) of the PFU should be disconnected from the electrical power supply – this should be reﬂected in the wiring on site.

6.5.2 Via the safety interlocks (limits)

The safety interlock turns off the power to input 26e, such as in the event of air deﬁciency or similar.

In the case of pilot/main burner monitoring, the minimum combustion time only has an effect on the behaviour of the main burner. The minimum combustion time for the pilot burner is limited to the safety time on start-up (t

Background: The pilot burner is only used in single-stage operation.

PFU 780 · Edition 02.12 50

SA1

Project planning information

6.6 Reset

6.6.1 Parallel reset

Several burner control units can be reset in parallel using the external button. The PFU cannot be reset by mains failure.

6.6.2 Permanent remote reset

Permanent remote reset gives rise to a malfunction. If a remote reset signal is permanently applied to terminals 10c/12c, ﬂashes on the display to indicate a fault.

Reset with a pulse < 1 s.

6.6.3 Automatic remote reset (PLC)

In the case of automatic remote reset (PLC), the reset pulse duration should not exceed 1 second. Check compliance with standards.

If a fault is acknowledged by remote reset too often, error (Too many remote resets) is displayed. The error can only be acknowledged with the Reset/Information button on the unit.

The burner malfunction must be remedied. The malfunction can not be remedied by changing the method of activation.

6.6.4 Burner start

A furnace start may only be initiated, if it has been ensured using an appropriate procedure that there is no combustible mixture in the combustion/processing chamber, in the connected areas or in the exhaust gas system (heat exchanger, dust collector). This can be achieved by pre-purge, which occurs immediately before ignition or within the period speciﬁed in the operating instructions.

In the case of multiple burner applications, pre-purge is not necessary after a normal burner shut-down.

Note the requirements of the Standards. For exceptions, see Standards.

6.6.5 Restart and start-up attempts

The precondition for a restart/start-up attempt is that activation of the restart allows the burner to restart as intended (in all operating phases). In this case, it must be ensured that the program sequence started by the PFU matches the application.

Note the requirements of the Standards. For exceptions, see Standards.

PFU 780 · Edition 02.12 51

Project planning information

6.7 Fault message

The fault signalling contact opens, as soon as the mains vol- tage fails.

6.8 Protecting the pilot burner from overload

To protect the unit against overload by frequent cycling, the maximum number of start-ups per minute is limited for the PFU. Excessive cycling triggers a fault message (blinking The max. number of start-ups per minute depends on the safety time tSA:

[s] Ignition transformer TZI Max. start-ups/min.

3 5-15/100 6 5 5-15/100 5

10 5-15/100 4

6.9 Installation

Installation position: any. Installation in 19” module subracks only, see page 56 (So-

cket connectors) Install in clean environment ensuring enclosure IP 54 or higher,

whereby no condensation is permitted. Cable length between PFU and burner: max. 100 m.

6.10 Wiring

The PFU is suitable for hard wiring only. Do not reverse phase and neutral conductor. Different phases of a three-phase current system must not be installed at the PFU. No voltage may be connected to the valve and ignition outputs.

6.10.1 UVS sensor wiring

Connect the UVS sensor directly to the PFU. Operating the sensor with incorrect polarity or voltage can lead to destruction of the sensor.

6.11 PFU switched off

The PFU cannot be activated when no mains voltage is applied or when it is switched off. The fault signalling contact is only closed when the unit is supplied with voltage and switched on.

If the unit is switched off, an immediate program abort with switch-off of all outputs occurs (even during the safety time). When the unit is switched on, the program run is restarted in standby.

PFU 780 · Edition 02.12 52

Project planning information

6.12 Furnace control

Switch on the system to start up the furnace, then release the burner start via the safety interlocks and afterwards start the burner control so that the burner control unit may monitor the burners as intended. To shut down the furnace, ﬁrst disconnect the burner control unit from the temperature control (burner ON signal), then disconnect the safety interlocks and ﬁnally switch off the system.

6.13 Note on EC type-examination

Since EN 298 (1993) does not describe all functions of the PFU, the operator is responsible for ensuring that all parameters and functions are matched to the respective application.

6.14 Mains switch

The mains switch in the unit isolates the PFU on two poles from the mains. It does not meet the requirements of EN50156- 1:2004 (5.2.2 Switch disconnectors) set out in chapter5 for a device to disconnect the power supply. Although the mains switch cannot be used for disconnecting from the electrical power supply in accordance with EN50156, it does allow the burner to be isolated functionally from the central control system. This function is required for manual operation and, in the case of PROFIBUS units, to switch off the unit without causing BUS errors. Disconnection for electrical maintenance work is to be implemented with an external switch per unit or group only, in accordance with Standard “EN50156”.

6.15 Changing parameters

In certain cases, it may be necessary to change the default settings. Using a separate software package and a PC optoadapter, it is possible to modify certain parameters on the PFU, such as the switch-off threshold of the ﬂame ampliﬁer, the behaviour in the event of a ﬂame failure or if the pilot burner is to burn permanently in the case of pilot and main burner monitoring.

The software package with PC opto-adapter, as well as

“Changed parameters” stickers, are available as accesso-

ries– see section entitled page 55 (Accessories) . The unit parameters set at the factory are speciﬁed in the

delivery note. Document changed parameters in BCSoft using the protocol

function and enclose the protocol with the plant documentation. If a replacement is ordered for a PFU with changed parameters,

refer to the protocol for details.

PFU 780 · Edition 02.12 53

7 Flame control

7.1 With ionisation sensor

The PFU generates an alternating voltage (230 V AC) between the sensing electrode and burner earth. The ﬂame rectiﬁes this voltage. Only the DC signal (depending on the switch-off threshold for the pilot and main burners) is recognised by the burner control unit as a ﬂame signal.

A ﬂame cannot be simulated. Ignition and monitoring with a single electrode is possible.

7.2 With UV sensor

A UV tube inside the UV sensor detects the ultraviolet light of a ﬂame. It does not respond to sunlight, incandescent bulb light or infrared radiation emitted by hot workpieces or red- hot furnace walls.

In the event of incident UV radiation the UV sensor rectiﬁes the supplied alternating voltage. As with ionisation control, the burner control unit only detects this DC signal.

When using UV sensors of Type UVS, the burner control unit may be used for intermittent operation only. This means that operation must be interrupted at least once every 24 hours. This can be programmed using parameter 35.

For further information, see brochure UVS. The burner control unit PFU..U is prepared for UV sensor UVD1.

This enables continuous operation. For further information, see Technical Information Bulletin UVD.

7.3 Via the temperature in high temperature equipment

High temperature equipment is deﬁned as a thermoprocessing installation, in which the wall temperature of the combustion chamber and/or the processing chamber exceeds 750°C. Burner control unit PFU..D features a special “High temperature operation” function. During heating up, standard monitoring methods (ionisation or UV) must be used for ﬂame control. When the working temperature has exceeded 750°C, indirect ﬂame control can be taken over by a central monitoring device. When the DI input (terminal 22a) is activated, the burner control unit reverts to this operating mode.

Important: In “High temperature operation”, i.e. with the DI input being activated, burner control unit PFU..D does not evaluate the ﬂame signal. The safety function of the burner control unit’s ﬂame control is deactivated during this operating phase.

PFU 780 · Edition 02.12 54

8 Accessories

Brenner 1 Zone 3

D-49018 Osnabrück, Germany

Achtung, geänderte Parameter!

Die Angaben auf dem Typenschild gelten nicht mehr in vollem Umfang. Aktuelle Parameter direkt auslesen.

Important, changed parameters!

The details on the type label are no longer completely accurate. Read the current parameters direct from the unit.

Attention, paramètres modifiés !

Les informations figurant sur la plaque signalétique ne sont plus valables dans leur intégralité. Veuillez vous référer directement aux paramètres actualisés.

8.1 High-voltage cable

FZLSi 1/7 up to 180°C, Order No.: 04250410.

FZLK 1/7 up to 80°C, Order No.: 04250409.

8.2 BCSoft

Opto-adapter including BCSoft CD-ROM, Order No.: 74960437.

The current software can be downloaded from our Internet site at http://www.docuthek.com. To do so, you need to register in the DOCUTHEK.

8.3 Stickers for labelling

For printing with laser printers, plotters or engraving machines, 27 × 18 mm or

28 × 17.5 mm. Colour: silver

8.4 “Changed parameters” stickers

Afﬁx on the connection diagram of the PFU following changes to unit parameters set at the factory.

100 pcs, Order No.: 74921492.

PFU 780 · Edition 02.12 55

Accessories

8.5 Radio interference suppressed electrode adapters

Plug cap, 4 mm, interference-suppressed, Order No. 04115308.

Straight adapter, 6 mm, interference-suppressed, Order No. 04115306.

8.6 Socket connectors

Type

Socket connector E, 48-pin solder tag connection Socket connector E, 48-pin wire-wrap connection

Order No. 04120148 04120158

8.7 Module subrack

Module subrack BGT SM-8/1/1 for MPT 700, PFU 780

comprising: module subrack, printed-circuit board with rear terminal strip,

function-tested, standard documentation, guide rails, without partial front plates, screw terminals at the rear, single-zone operation for MPT 700 operating modes 1 – 4, two-zone operation for MPT 700 operating modes 1 – 4, but max. 4 burners per zone.

Slot 1 for MPT 700, slots 2 – 9 for PFU 760/780, slot 10 for PFP700 Order No. 84402282 (no illustration provided)

Module subrack BGT SA for PFA 700/PFU 760 and PFA 710/ PFU 780

consisting of: odule subrack, printed-circuit board with rear terminal strip, function-tested, standard documentation, guide rails, without partial front plates, screw terminals at the rear, relays and screw terminals for four free inputs and four free outputs, connection to PROFIBUS DP with D-Sub socket.

BGT SA-9: slot 1 for PFA 700, slots 2-10 for PFU 760, BGT SA-8: slot 1 for PFA 710, slots 2-9 for PFU 780

Order no. BGT SA-9U/1 DP700: 84402291 BGT SA-8U/1 DP710: 84402292 (no illustration provided)

Module subrack BGT S-9U/1 for PFP 700, PFU 780

comprising: module subrack, printed-circuit board with rear terminal strip, function-tested, standard documentation, guide rails, without partial front plates, screw terminals at the rear.

Slots 1 – 9 for PFU 760/780, slot 10 for PFP 700, Order No. 84402281

PFU 780 · Edition 02.12 56

8ace

30a

32c

12ace

PFP 700

24 V= 600 mA

0 V

230 V

115 V

Accessories

8.8 Power supply PFP 700

For supplying the control inputs of burner control unit PFU or for supplying the auxiliary voltage to relay module PFR 704. Operating status display on the front plate. PFP switches off in the event of an output overload.

Output voltage 24 V, output rating 14 VA. Order No. 84366510

PFU 780 · Edition 02.12 57

2e 2a 2c

115 V~

max. 2 A, 264 Vmax. 2 A, 264 Vmax. 2 A, 264 Vmax. 2 A, 264 V

PFR 704

230 V~

24 V=/~

0 V

10e 10a 10c

12e

16c

14e

14c

14a

16e

16a

0 V

18e 18a 18c

20e

24c

22e

22c

22a

24e

24a

0 V

26e 26a 26c

28e

32c

30e

30c

30a

32e

32a

0 V

115 V~

230 V~

24 V=/~

115 V~

230 V~

24 V=/~

115 V~

230 V~

24 V=/~

Accessories

8.9 Relay module PFR 704

For contact multiplication, e.g. if several air valves are activated via a single control signal for pre-purge, or for heating/cooling switchover when using an MPT. Switching status display on the front plate.

Input voltage: 110/120 V AC, -15/+10%, 50/60 Hz, 220/240 V AC, -15/+10%, 50/60 Hz, 24 V AC/DC, ± 10%.

Current per relay: 25 mA. Contact rating of ﬂoating outputs: max. 2 A, 264 V (not

fused internally). Order No. 84373510

PFU 780 · Edition 02.12 58

32b 30a

8b 11b 12b

PFA 700

µC

15b 16b

1. PFU

9. PFU

RxD/TxD-P

RxD/TxD-N

DGND

0 V

24 V=

…

10c

1. PFU

9. PFU

…

1. PFU

9. PFU

…

10a

18a

1. PFU

9. PFU

…

19a

23a

1. PFU

5. PFU

…

20c

23c

6. PFU

9. PFU

30c

…

24 V

0 V

24 V

…

14b

18b

21b 22b

…

23b

26b

24 V

I/O

18c

PFU

19c

17b

30e

26e

PFU

24 V

PROFIBUS DP

Accessories

8.10 Field bus interface PFA 700

For connection of up to nine automatic burner control units PFU760 to industrial communication networks using PROFIBUS-DP, in order to transfer measuring, control and regulation signals as a bundle.

4 digital inputs: 24 V DC, ± 10%, < 10 mA, 4 digital outputs: relay contact, max. 1 A, 264 V (not fused internally).

Mains voltage: 110 – 240 V AC, -15/+10%, 50/60 Hz. Further information can be found in Technical information

PFA.

PFU 780 · Edition 02.12 59

2b 4b

MPT 700

12–24 V

0 V

12–24 V

–

100%

GND

16b

14z

14d

16z

14b

10b

12b

0 V

6b 8b

COM

30b

30z

30d

28b

28z

28d

32b

32z

32d

20b

20z

20d

GND 100% – 0

18b

18z

18d

10z

12z

10d

µC

8888

Accessories

8.11 Impulse system MPT 700

With 11 outputs for activation of burner control units PFU 780. The furnace atmosphere is circulated thanks to intermittent operation, and thereby constant temperature distribution and shorter heating-up periods for all gas-ﬁred heat treatment furnaces are ensured.

Mains voltage: 95–240 V AC, ± 10%, 50/60 Hz. Power consumption: 10 VA. Additional auxiliary voltage: 12–24 V DC, ± 10%, max. 1.1 A. Controller inputs: 2 x 0(4)–20 mA with common earth, ﬂoating,

load impedance approx. 225 Ω. Three-point step input: ﬂoating, 12–24 V DC, load impedance

approx. 2.7 kΩ. Digital inputs E1–E3: with common earth, ﬂoating, 12–24 V DC,

load impedance approx. 2.7 kΩ. Order No. 84395050 Further information can be found in brochure MPT.

PFU 780 · Edition 02.12 60

9 Technical data

▼

Mains voltage: 220/240 V AC, -15/+10%, 50/60 Hz or 110/120 V AC, -15/+10%, 50/60 Hz, for grounded and ungrounded mains.

Power consumption: < 8 VA. Control inputs:

Input voltage/current: Pilot burner, main burner, air valve, multi-ﬂame control and remote reset: 24 V DC, ± 10%, < 7 mA per input.

Input voltage for safety interlocks, digital input DI and purge = mains voltage.

Input voltage of signal inputs:

Rated value 110/120 V AC 220/240 V AC Signal “1” 80 – 132 V 160 – 264 V Signal “0” 0 – 20 V 0 – 40 V Frequency 50/60 Hz 50/60 Hz

Rated value 24 V DC Signal “1” 24 V, ±10% Signal “0” < 1 V

Inherent current:

Signal “1” typ. 5 mA

Output voltage for voltage-related outputs = mains voltage.

Contact rating Gas valve V1, V2 Max. 1 A resistive

Air valve Max. 1 A resistive

Ignition Max. 1 A resistive Number of operat-

ing cycles

Max. 1,000,000,

typically 400,000

Max. 1 A cos ϕ 0.3

Max. 250,000,

typically 100,000

Output current: max. 2 A per output, but total current for valves and ignition transformer max. 2.5 A.

Operation and fault signalling contacts: dry contact (ﬂoating), max. 1 A, 24 V, not fused internally.

Number of operating cycles: Mains switch: 1000, Reset/Information button: 1000.

PFU 780 · Edition 02.12 61

Technical data

Flame control: Sensor voltage: approx. 230 V AC. Sensor current: > 1 µA, Length of sensor cable: max. 100 m.

Fuse in unit: F1: 3.15 A, slow-acting, H pursuant to IEC 127-2/5, F2: 3.15 A, slow-acting, H pursuant to IEC 127-2/5.

Ambient temperature:

-20 to +60 °C (-4 to +60.00 °C), Climate: no condensation permitted.

Enclosure: IP 00 pursuant to IEC 529, after installing in a 19” module subrack according to the in- structions, e.g. type BGT, the front corresponds to IP 20.

Input/Output safety circuit: All the inputs and outputs marked “ grams) may be used for safety tasks.

Weight: approx. 650 g (23 oz.).

” (see connection dia-

PFU 780 · Edition 02.12 62

Technical data

9.1 Safety-speciﬁc characteristic values

In the case of ionization control, suitable for Safety Integrity Level Diagnostic coverage DC 97.9%

Type of subsystem

Mode of operation

Mean probability of dange- rous failure PFH

Mean time to dangerous failure MTTF

Safe failure fraction SFF 99.2%

The speciﬁed values apply for the combination with ionization electrode (sensor) and PFU 780 (logic).

Relationship between the Performance Level (PL) and the Safety Integrity Level (SIL)

PL SIL

a – b 1

c 1 d 2 e 3

SIL 3

Type B to EN 61508-2,

7.4.3.1.4 High demand mode pursu- ant to EN 61508-4, 3.5.12

1.34 x 10-8 l/h

Max. service life under operating conditions: 20 years after date of production, plus max. 1/2 year in stor-

age prior to ﬁrst use. For a glossary of terms, see page 67 (Glossary).

Pursuant to EN ISO 13849-1:2006, Table 4, the PFU can be used up to PL e.

PFU 780 · Edition 02.12 63

Technical data

3 HE =

133.4 (5.3“)

8 TE =

40.6 (1.6“)

9.2 Operating controls

A: 2-digit 7-segment display B: Reset/Information button to reset the system after a fault

or to scan parameters on the display C: Mains switch D: Optical interface

E: Type label

PFU 780 · Edition 02.12 64

10 Maintenance cycles

Burner control unit PFU requires little servicing.

PFU 780 · Edition 02.12 65

11 Legend

Display

Blinking display

Ready Safety interlocks (Limits) Start-up signal, pilot burner

Start-up signal, main burner

Digital input Ignition transformer

Gas valve

Air valve

Purge

Ext. air valve control Flame signal Operating signal, pilot burner

Operating signal, main burner Fault signal Reset Input signal Output signal Flame simulation check

Waiting time ≥ 2 s

Safety time on start-up 3 s, 5 s or 10 s

Safety time during operation < 1 s or < 2 s

Ignition time 2 s, 3 s or 6 s

Flame simulation delay time 25 s

Flame proving period 0 – 25 s

tBMinimum combustion time tSA up to max. 25 s

Minimum burner pause time 0 – 250 s

Low ﬁre over run time 0 s, 5 s, 15 s or 25 s

Input/Output safety circuit

PFU 780 · Edition 02.12 66

12 Glossary

12.4

Flame simulation/Flame simulation delay time t

12.1 Waiting time t

02 02

30e

10e 28c

16c

26a

18e

2c–4c

2e–4e

Once the start-up signal ϑ has been applied, the waiting time tW starts to elapse. During this time, a self-test is conducted to detect errors in internal and external circuit components. If no malfunction is detected, the burner will start up.

12.2 Safety time on start-up tSA

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 tSA (3, 5 or 10 s) is the minimum operating time of the burner and burner control unit.

12.3 Ignition time tZ

If no malfunction is detected during the waiting time tW, the ignition time tZ then starts to elapse. Voltage is supplied to the pilot gas valve V1 and the ignition transformer and the burner is ignited. The duration of the ignition time is either 2, 3 or 7seconds (depending on safety time tSA selected).

01 88

30e

10e

28c

16c

26a

18e

2c–4c

2e–4e

An extraneous signal (ﬂame simulation) is a ﬂame signal that is detected, although there should be no ﬂame according to the program sequence. If such an extraneous signal is detected, the ﬂame simulation delay time tLV starts to elapse. If the ﬂame simulation is discontinued during the ﬂame simulation delay time tLV, start-up can be initiated or operation continued. Otherwise, a fault lock-out occurs.

12.5 Safety time during operation t

04 04

2c–4c

2e–4e

30e

10e

28c

16c

26a

18e

If the ﬂame fails during operation, the valve outputs are disconnected within the safety time tSB.

PFU 780 · Edition 02.12 67

Glossary

The default safety time during operation tSB 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 seconds (see “Project plan- ning information”). Note the requirements of the Standards!

12.6 Flame signal

If a ﬂame is detected, the ﬂame detector will supply a ﬂame signal.

12.7 Fault lock-out

In the event of a fault lock-out, all valves and the ignition trans- former are disconnected from the electrical power supply, and a fault is signalled. Resetting must take place manually following a fault lock-out.

12.8 Safety interlocks (Limits)

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.

12.9 Pilot gas valve V1

The start fuel ﬂow rate for the pilot burner is released by pilot gas valve V1. It opens when the safety time on start-up t starts to elapse. It remains open until the burner is switched off again by a normal shut-down or fault lock-out.

SA1

12.10 Main gas valve V2

The start fuel ﬂow rate for the main burner is released by main gas valve V2. It opens when the safety time on start-up t

SA2

starts to elapse. It remains open until the burner is switched off again by a normal shut-down or fault lock-out.

L1 (L1)

N (L2)

30e

26e

22a

30a

20c 230 V

32c 24c

PFU 780

sk1

22e

16c

18e

12.11 Continuous operation

The gas burner runs continuously for more than 24 hours.

12.12 Air valve

The air valve can be used

– for cooling, – for purging, – to control the burner capacity in ON/OFF mode and in

High/Low mode when using a pneumatic air/gas ratio

control system.

PFU 780 · Edition 02.12 68

Glossary

12.13 Diagnostic coverage DC

Measure of the effectiveness of diagnostics, which may be determined as the ratio between the failure rate of detected dangerous failures and the failure rate of total dangerous failures

NOTE: Diagnostic coverage can exist for the whole or parts of a safety-related system. For example, diagnostic cover- age could exist for sensors and/or logic system and/or ﬁnal elements. Unit: %.

from EN ISO 13849-1:2008

12.14 Mode of operation

High demand mode or continuous mode Operating mode, where the frequency of demands for opera-

tion made on a safety-related system is greater than one per year or greater than twice the proof-test frequency

from EN 61508-4:2001

12.15 Safe failure fraction SFF

Fraction of safe failures related to all failures, which are as- sumed to appear

from EN 13611/A2:2011

12.16 Probability of dangerous failure PFHD

Value describing the likelihood of dangerous failure per hour of a component for high demand mode or continuous mode. Unit: 1/h

from EN 13611/A2:2011

12.17 Mean time to dangerous failure MTTFd

Expectation of the mean time to dangerous failure

from EN ISO 13849-1:2008

PFU 780 · Edition 02.12 69

Feedback

Kromschröder AG

Michael Rehkamp

m.rehkamp@kromschroeder.com

Osnabrüc

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PFU 780 · Edition 02.12

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03250720

Krom Schroder PFU 780 Technical Information

Specifications and Main Features

Frequently Asked Questions

User Manual

Burner control unit PFU 780

Table of contents

1 Application

1.1 Examples of application

1.1.1 Stage-controlled main burner with alternating pilot burner

1.1.3 Modulating-controlled burner

1.1.4 PFU 780..D: High temperature equipment

3.1 Connection diagram

3.1.1 PFU 780

3 Function

3.1.2 PFU 780..K2

3.2 PFU 780 program sequence

3.3 Program status and fault messages

4 Parameters

4.1 Scanning the parameters

4.2 Flame control

4.2.1 Flame signal, pilot burner

4.2.2 Flame signal, main burner

4.2.3 Program status when the most recent fault occurred

4.2.5 High temperature operation with PFU..D

4.2.6 UVS check

4.3 Pilot and main burner monitoring

4.4 Behaviour in start-up position/standby

4.4.1 Flame simulation check in start-up position/standby

4.4.2 Minimum burner pause time tBP

4.5 Behaviour during start-up

4.5.1 Safety time on start-up tSA

4.5.2 Flame proving period tFS Pilot burner

4.5.4 Burner start-up attempts

4.6 Behaviour during operation

Safety time during operation tSB for pilot and main burners

4.6.2 Fault lock-out or restart, pilot burner

4.6.3 Fault lock-out or restart, main burner

4.7 Air valve control PFU..L

4.7.1 Purge

4.7.2 Cooling in start-up position/standby

4.7.3 Burner start

4.7.4 Air valve opens in the case of external activation (not during start-up)

4.7.5 Air valve opens in the case of external activation (even during start-up)

4.7.6 Air valve opens with valve V2

4.7.7 Air valve opens with operating signal

Behaviour of the air valve in the event of a fault lock-out

4.8 Manual operation

4.8.1 Manual mode limited to 5 minutes

4.9 Password

5 Selection

5.1 Calculating the safety time tSA

5.2 Selection table

5.2.1 Type code

6 Project planning information

6.1 Cable selection

6.1.1 Ignition cable

6.1.2 Ionisation cable

6.1.3 UV-Leitung

6.2 Ignition electrode

6.2.1 Electrode gap

6.2.2 Star electrodes

6.3 Minimum combustion time

6.4 Safety interlocks (Limits)

6.5 Emergency stop

6.5.2 Via the safety interlocks (limits)

6.6 Reset

6.6.1 Parallel reset

6.6.2 Permanent remote reset

6.6.3 Automatic remote reset (PLC)

6.6.4 Burner start

6.6.5 Restart and start-up attempts

6.7 Fault message

6.8 Protecting the pilot burner from overload

6.9 Installation

6.10 Wiring

6.10.1 UVS sensor wiring

6.11 PFU switched off

6.12 Furnace control

6.13 Note on EC type-examination

6.14 Mains switch