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Building Technologies Basic Documentation LMV5... CC1P7550en
4 Burner control 22.05.2018
4.2 Control sequence
The sequence diagrams show the control sequence in detail (refer to chapter
Sequence diagrams).
4.2.1 Parameters
4.2.1.1 Time parameter
The most important time parameters for the control sequence are the following (for
values, refer to Setting Lists, I7550):
∂ Prepurge time
∂ Preignition time / circulation time heavy oil
∂ First safety time
∂ Second safety time
∂ Interval 1
∂ Interval 2
∂ Postpurge time 1 (t8-1) with flue gas recirculation (FGR) damper shut (this part of
the postpurge time is always executed)
∂ Postpurge time 3 (t8-3) with flue gas recirculation (FGR) damper open (this part of
the postpurge time is interrupted when there is a heat request)
∂ Postpurging in the lockout phase (if fan motor (G) = ON before lockout occurred)
All the times mentioned above – with the exception of Postpurge in the lockout phase –
depend on the type of fuel, which means that different times can be set for oil and gas.
The prepurge time and the safety times are safety-related. This means that, using the
AZL5, the heating engineer can only readjust them in the «safe» direction (against
internal maximum or minimum values).
In other words, safety times can only be shortened and «tv» times can only be
extended.
Attention!
On the OEM access level, it is possible to make parameter settings that differ
from application standards for the maximum safety time (MaxSafetyTGas or
MaxSafetyTOil). For this reason, check whether the parameter settings made are
in compliance with the application standards (e.g. EN 676, EN 267, etc.), or
whether the respective plant requires special approval!
4.2.1.2 Reaction time for loss of flame / safety time in operation
The reaction time to a loss of flame during operation (phases 44, 52, 54, 60, and 62)
can be set via parameter ReacTmeLossFlame.
The safety time in operation results:
∂ With internal flame supervision (flame detector at input X10) by adding
ReacTmeLossFlame + 0.8 second
∂ With external flame supervision (flame detector at input X6-01 pin 3 / pin 1) by
adding ReacTmeLossFlame + 1 second + reaction time of the external flame
safeguard (see also section External flame supervision (LMV50 / LMV52)
Examples of internal flame supervision:
∂ With the basic setting for ReacTmeLossFlame of 0.2 second, safety time during
operation is less than 1 second (0.2 second + 0.8 second)
∂ At the maximum setting for ReacTmeLossFlame of 3.2 seconds, safety time during
operation is less than 4 seconds (3.2 seconds + 0.8 second)
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