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Siemens Building Technologies Basic Documentation LMV5... CC1P7550en
HVAC Products 6 Temperature or pressure controller (internal load controller LC) 13.08.2004
6.8.2 CSTP – multistage operation
The difference between multistage and modulating control is that with multistage con-
trol the output steps are defined by the number of burner stages. With modulating con-
trol, 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.
Spacing of temperature lines
corresponds to the setpoint steps
Manipulated
variable
Actual value
Setpoint
Threshold OFF
Threshold ON
Stage 1
Stages 1 und 2
Stages 1, 2 und 3
Setpoint step is reached
before max. time has elapsed.
Start of 3rd stage.
Max. output will be delivered.
7550d05e/0704
Setpoint step not
reached, but max. time
exceeded.
Therefore, start of 2nd
stage
Burner off,
actual value
below thresh-
old ON.
Burner will be
switched on
with stage 1
⇒
Actual value reached.
Threshold OFF
Change to multistage
control
6.8.3 CSTP with temperature sensor in pressure plants
In pressure plants, thermal shock protection can also be accomplished with a tempera-
ture 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)
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