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Building Technologies Basic Documentation LMV5... CC1P7550en
9 Commissioning instructions for the LMV5 22.05.2018
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.
Parameters: Shock protection on/off ColdStartOn Activated
Shock protection activation level ThresholdOn 40% of setpoint
Output step (only for modulating
operation)
StageLoad 15% of burner output
Setpoint step modulating StageStep_Mod 10% of setpoint
Max. time modulating per step MaxTmeMod 5 minutes
Shock protection deactivation level ThresholdOff 80% of setpoint
Spacing of temperature lines
corresponds to the setpoint steps
from the actual setpoint, e.g. 10 % = 1 bar
Manipulated
variable
Actual value
Setpoint
Threshold OFF
Threshold ON
Load steps
e.g. 15 %
7550d30E/0502
10 bar = 100 %
8 bar = 80 %
7 bar
6 bar
5 bar
4 bar = 40 %
Load 85 %
Load 70 %
Load 55 %
Load 40 %
Burner start at
low-fire, e.g. 25 %
1. 2.
Burner off,
actual value
below
threshold ON.
Burner will be
switched on
Setpoint step not reached,
but max. time exceeded.
Therefore, increase of
manipulated variable by
load step,
e.g. MaxTmeMod = 5 min.
Setpoint step is reached
before max. time has elapsed.
Increase of manipulated variable
by load step.
⇑
Actual value reached.
Threshold OFF
Change to control
Figure 85: Cold start thermal shock protection
Cold start thermal shock
protection (CSTP)
Description
Example
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