CE1P2522E / 30.03.2000
Basic Documentation RVL470
Siemens Building Technologies
30/68
Function block "Three-position actuator heating circuit"
Landis & Staefa Division
The rate of increase of the flow temperature setpoint can be limited to a maximum. In
that case, the maximum rate of increase of the flow temperature setpoint is the selected
temperature per unit of time (°C per hour).
This function
•
prevents cracking noise in the piping
•
protects objects and construction materials that are sensitive to quick temperature
increases (e.g. antiquities)
•
prevents excessive loads on heat generating equipment
This function can be deactivated (setting ---).
9.3. Three-position control
Three-position control operates as weather- or demand-compensated PI flow tempera-
ture control. The flow temperature is controlled through the modulating regulating unit
(slipper or seat valve). Thanks to the I-part, there is no control offset.
The control's positioning commands to the actuator of the regulating unit are fed to the
output relays and indicated by LEDs.
9.4. Excess mixing valve temperature
In interconnected plants, an excess mixing valve temperature can be entered on the
RVL470. This is a boost of the heating zone's flow temperature setpoint. The higher
setpoint is delivered to the heat generating equipment as the heat demand signal.
The excess mixing valve temperature can only be set on controllers driving a mixing
valve (controller N2 in the example below, operating line 84).
Example:
N2
w
N2
w
N1
= w
N2
+ w
2522
S
0
7
w
N1
Boiler temperature controller (heat generation)
N2
Flow temperature controller (heating zone)
w
N1
Setpoint of the boiler temperature controller
w
N2
Setpoint of the flow temperature controller
∆
w
Excess mixing valve temperature (to be set on controller N2)
9.5. Locking of pulses
If the actuator receives only closing or opening pulses for a period of time equivalent to
five times the actuator running time, all additional pulses delivered by the controller will
be locked, thus reducing the strain on the actuator.
For safety reasons however, the controller delivers pulse in the opposite direction at 10-
minute intervals.
An pulse in the opposite direction negates the pulse lock.