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ถ.บรมราชชนนี ศาลาธรรมสพน์ ทวีวัฒนา กทม.
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Mode of operation of the flame safeguards in the case of multiflame supervision with pilot burner and a PLC,
intermittent operating mode
Wait for standby
Test for prematurely aged UV cell
Program time
tw
tan
Phase number AZL2
oP:P2
0
Parameter number AZL2
0
7
.
1
2
LED steady on
LED flashes
Terminal
Function / inputs
Ro3
T / B
hr1
No. 4 / 5
FS
(LFS1...)
Ro2
V2
Safety shutdown V2 = OFF
Terminal
Function / outputs
If the fr2 signal disappears due to extraneous
T
light (e.g., from an aged UV cell), burner startup
/
must be prevented.
B
Dix
hr1
fr1
Burner 2)
Diy
fr2
Burner 2)
In the case multiflame supervision with a
pilot burner, a fail-safe PLC performs the
central control function (the example shown
uses a Simatic ET200SP F-CPU and input /
output modules ET200SP F-I/O).
The pilot burner has its own ignition
equipment (Z1), its own fuel valve (V1), and
its own flame supervision system made up of
a flame safeguard LFS1.2 and an ionization
probe (ION).
The main burner has its own fuel valve (V2)
and its own flame supervision system made
up of a flame safeguard LFS1 and a UV flame
detector QRA.
The main burner does not have its own
ignition equipment (Z1) as its flame is safely
ignited by the pilot burner. The flame relay
control contacts for both flame safeguards
LFS1.2 are connected in series.
This means that both burners can only be
switched on and off together with the other
burner in each case. The flame ON signal at
terminals
Dix
/
Diy
on the digital input module
F-DI can therefore only occur when both
flame signals are present.
Extinguishing 1 of the 2 flames, or even both
flames, leads to a flame OFF signal. The flame
signal is evaluated in the PLC on a non-
equivalent basis in line with the evaluation
principle 1oo2 (1-OFF-2).
This means that the 2-way start pulse is
tested at terminals
Dix
and
Diy
. In the event of
a flame ON signal, the fr1 (NO) contact closes
and the fr2 (NC) contact opens at the same
time.
In the event of a flame OFF signal, the fr2
(NC) contact closes and the fr1 (NO) contact
opens at the same time.
The test mode switchover for the pilot burner
flame safeguard is inactive (terminal 6 is
permanently connected to phase conductor
L). The test mode switchover for the main
burner flame safeguard is active.
This means terminal 6 is switched off by the
PLC via a fail-safe relay output (Ro3) at set
intervals or after 24 hours of uninterrupted
burner operation at the very latest; refer to
the adjacent control sequence.
The PLC must prevent further burner operation
until the cause of the error has been rectified.
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Building Technologies CC1N7782en 18.04.2018