Siemens LFL1.333 - Interrupted Pilot Burner Startup Sequence; Interrupted Pilot Burner Operation

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Building Technologies Division CC1N7451en
20.11.2017
Startup sequence (cont'd)
Interrupted pilot burners
t3
t3´
Preignition time
Release of fuel for pilot burner via terminal 17
TSA
TSA´
Ignition safety time
On completion of «TSA», a flame signal must be present at terminal 22. It must not be interrupted until
controlled shutdown takes place
 otherwise non-volatile lockout
t4
t4´
Interval «ZBV-BV1»
Up to the release of the fuel valve at terminal 19 for the main burner’s start load
t9 Second safety time
On completion of the second safety time, the main burner must have been ignited by the pilot burner since
terminal 17 becomes dead as soon as this time has elapsed, causing the pilot valve to close
B Operating position of the burner
B-C Burner operation
-
During burner operation, «LR» drives the air damper to the high-fire or low-fire position, depending on
the demand for heat
- Release of high-fire is enabled by auxiliary switch «v» in the actuator
- In the event of loss of flame during operation, the LFL1… will initiate lockout
C Controlled shutdown
On controlled shutdown, the «BV...» will immediately be closed. At the same time, the sequence switch
starts and programs «t6»
C-D The sequence switch travels to start position «A», postpurging
When burner off time starts, control terminals 11 and 12 carry voltage to drive the air damper to the fully
CLOSED position. Flame signal supervision also remains active during burner off times
t6 Postpurge time
-
Fan «M2» connected to terminal 7
- Shortly after the start of «t6», power is fed to terminal 10
 air damper will be driven to the MIN position
- Full closing of the air damper starts only shortly before «t6» has elapsed
 triggered by the control signal at terminal 11
- During the following burner off period, terminal 11 remains live
t13 Permissible afterburn time
During «t13», the flame signal input can still receive a flame signal
 no lockout
D-A End of control sequence

start position
As soon as the sequence switch has reached the start position – thereby switching itself off – the flame
detector and extraneous light test will start again.
During burner off periods, the flame supervision circuit is live. A faulty flame signal of a few seconds will
initiate lockout.
Short ignition pulses of the UV tube, caused for instance by cosmic radiation, do not lead to lockout.
Times «TSA´», «t3´» and «t4´» only exist with burner controls of the 01 series.