Siemens LMV50 Series Manual page 188

Cold start thermal shock
protection (CSTP)
Description
Example
Parameters:
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Building Technologies
When the cold start thermal protection function is activated, a boiler – after having
dropped below a predefined switch-on threshold – is heated up in multistage operation.
This approach ensures that when cold, the boiler does not have to satisfy the maximum
request for heat within a very short period of time. Thermal strain on the boiler will thus
be prevented.
The cold start sequence is activated when, upon startup, the actual value lies below the
switch-on threshold. When cold start thermal shock protection is activated, the
manipulated variable – upon cold start – is increased in a stepwise fashion using the
adjusted output step (or the next stage is switched on).
The load is increased by one load step (15% in the example below):
1. as soon as the actual temperature has increased by the set setpoint step (in the
example below, by 5% = 4°)
2. or if this temperature increase was not reached by the end of the set maximum
time.
When the switch-off threshold is reached, the cold start sequence is ended and normal
control operation started.
Modulating burner with pressure control
For the output step, any output value in % can be predefined. 100% divided by the
output step gives the number of possible steps.
Shock protection on/off
Shock protection activation level
Output step (only for modulating
operation)
Setpoint step modulating
Max. time modulating per step
Shock protection deactivation level
Setpoint
Spacing of temperature lines
corresponds to the setpoint steps
from the actual setpoint, e.g. 10 % = 1 bar
Load steps
e.g. 15 %
Burner start at
low-fire, e.g. 25 %
1.
Burner off, Setpoint step not reached,
actual value but max. time exceeded.
below Therefore, increase of
threshold ON. manipulated variable by
Burner will be load step,
switched on e.g. MaxTmeMod = 5 min.
Figure 85: Cold start thermal shock protection
Basic Documentation LMV5...
9 Commissioning instructions for the LMV5
ColdStartOn
ThresholdOn
StageLoad
StageStep_Mod
MaxTmeMod
ThresholdOff
Threshold OFF
Load 85 %
Load 70 %
Load 55 %
Load 40 %
2.
Setpoint step is reached
before max. time has elapsed.
Increase of manipulated variable
by load step.
Activated
40% of setpoint
15% of burner output
10% of setpoint
5 minutes
80% of setpoint
Actual value
10 bar = 100 %
8 bar = 80 %
7 bar
6 bar
5 bar
4 bar = 40 %
Manipulated
variable
Threshold ON
Actual value reached.
⇑
Threshold OFF
Change to control
7550d30E/0502
CC1P7550en
22.05.2018