High Temperature Operation With Pfu - Honeywell Krom Schroder PFU 780 Technical Information

Parameters
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 supports the "High tempera-
ture 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 tem-
perature 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 sys-
tem is placed out of operation.
In High temperature mode, the gas valves are opened
without flame control.
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 tempera-
ture. For this purpose, we recommend a safety tem-
PFU 780 · Edition 02.12l
perature 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.
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.
00 02 03 04
t t
Z FS1
t
SA1
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 oper-
ated with the internal flame control system.
▼
06 07 08 88
30a
26e
10e
1
28c
22a
DI
16c
V1
26a
1
2c–4c
1
14a
2
18e
V2
18a
2
6a–6e
2
2e–4e
t
t t
SA2 FS2
21