Siemens LMS14 User Manual page 549

Special cases (deviations)
Building Technologies Division

Forced prepurging
Forced prepurging takes place via parameter Req speed prepurging min (9505) after ...
- an off time of more than 24 hours,
- power ON,
- shutdown due to an interruption of gas supply during the safety time.
Forced prepurging takes place in phase TV.
It lasts 21 seconds, or >21 seconds if the prepurge time is set to >21 seconds.
The deviations marked Z in the sequence diagram cause the burner control to execute
forced prepurging during the next start phase.

Number of start attempts at the end of the ignition safety time (TSA)
If no flame is established by the end of the safety time (TSA), the burner control ...
- can go to lockout, or
- can trigger a repetition by changing to home run.
Refer to section Maximum number of start attempts for establishment of flame.

Loss of flame during operation
If parameterized, in the event of loss of flame during operation, a change to home run
with restart takes place (refer to section
of flame during operation

Prepurging
Prepurging can be deactivated by setting the prepurge time to 0 seconds. In that case –
as shown in the sequence diagram – a change from phase THL1 to phase TW1 takes
place.

Preignition time
If parameter Preignition time (9517) is set to 0 (no ignition prior to safety time (TSA)),
phase TVZ is completed within the minimum time of 0.2 seconds.

Forced intermittent operation
After a maximum of 24 hours of uninterrupted operation, the unit is forced to shut down,
ensuring regular shutdown to the standby phase. The timer for forced intermittent
operation will be reset in the standby phase. Fast startup with forced intermittent
operation is not possible.

Ignition safety time (TSA)
As described above, when evaluating the flame at the end of the ignition safety time,
the behavior of the burner control can be influenced. Also, the second safety time
(TSA2) should not be selected too short, thus making certain that there will be no
erroneous evaluation of the flame due to simulation resulting from ignition.

Postpurging
Postpurging can be parameterized in 2 different ways. Either postpurging at the
prepurge speed or at the speed used last in operation. The postpurge time is set via the
prepurge time (Tn) (see above).
User Manual LMS14...
6 The settings in detail
Maximum number of start attempts upon loss
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CC1U7471en
28.01.2015