Modulating Control, Conventional - Siemens LMU54 Series Basic Documentation

Modulating control,
conventional
54/171
Siemens Building Technologies
HVAC Products
The boiler circuit is a single temperature control loop:
Preset setpoint Controller
K
P
∆
Tsoll T
Boiler
setpoint
+
Basic structure of boiler controller
In the boiler circuit, the boiler temperature is maintained at the predefined setpoint. The
controller can be used for the heating circuit or the DHW circuit.
The overriding 2-position controller releases the above mentioned control loop and
ensures that the predefined setpoint will be maintained.
The result of the temperature controller is matched to the PWM signal of the controlling
element. The output is adjusted via the fan and via pneumatic or electronic ratio control.
In all cases, the temperature limiter overrides the temperature control loop. This means
that the temperature limiter switches off the boiler when «TkMax» is reached (triggering
safety shutdown).
Based on the control differential (∆T = Tsoll - Tist) and the selected controller
parameterization, the PID control algorithm calculates the required manipulated
variable. Using the controller parameters, the relevant controller part can be activated /
hidden or adapted to the controlled system.
It is also possible to set the sampling time for the boiler circuit and the DHW circuit.
The heat output determined by the PID controller is limited to the permissible output
range.
Basic Documentation LMU54... / LMU64...
3 Functions
Adaption of Pneum. / el.
manipulated ratio control
variable
T
N
T K PWM K Stell
V
PWM
Sensor
K T
Fühler Fühler
Burner and
heat exchanger
K T
Strecke Strecke
P TIst
7494b06e/0201
CC1P7494en
07.11.2002