Cstp - Multistage Operation; Cstp With Temperature Sensor In Pressure Plants - Siemens LMV5 Series Basic Documentation

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6.8.2 CSTP - multistage operation

The difference between multistage and modulating control is that with multistage
control the output steps are defined by the number of burner stages. With modulating
control, any output value in % can be entered.
With multistage control, a maximum of 3 output stages are available:
1. Stage 1
2. Stage 1 and stage 2
3. Stage 1, stage 2 and stage 3
Use of the output stages 2 and 3 can be locked. In that case, the boiler is heated with
stage 1 only.
Parameter: Release Stages (release / no release)
When stages 2 and 3 are locked, the system may stay in low-fire mode until the cold
start function is terminated, if the output delivered by stage 1 is not sufficient to reach
the switch-off threshold for thermal shock protection.
Setpoint
Spacing of temperature lines
corresponds to the setpoint steps
Stage 1
Burner off, Setpoint step not
actual value reached, but max. time
below thresh- exceeded.
old ON. Therefore, start of 2nd
Burner will be stage
switched on
with stage 1

6.8.3 CSTP with temperature sensor in pressure plants

In pressure plants, thermal shock protection can also be accomplished with a
temperature sensor (additional sensor), as an alternative to the pressure sensor.
Parameter: Additional Sensor (deactivated / PT100 / PT1000 / NI1000)
If an additional sensor is selected, the temperature setpoint for the additional sensor
applies. «Threshold_Off» refers to that value.
Parameter: Setpoint AddSens
Parameter: Threshold_Off
Note: When using the pressure sensor, the temperature limiter is not active.
This function may only be used in combination with temperature or pressure sensors.
Parameter: SensorSelection (Temp Sensor, Press Sensor)
Basic Documentation LMV51...
6 Temperature or pressure controller (internal load controller LC)
Threshold OFF
Stages 1, 2 und 3
Stages 1 und 2
Setpoint step is reached
before max. time has elapsed.
Start of 3rd stage.
Max. output will be delivered.
Actual value
Manipulated
variable
Threshold ON
Actual value reached.
⇒
Threshold OFF
Change to multistage
control
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CC1P7550en
01.10.2003