Siemens RDG400 Basic Manual page 26

3-position control
signal
Synchronization
PWM control
PWM for thermic
valve actuators
Note!
PWM for electric heaters
26/44
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Building Technologies
Output Y1 provides the OPEN command, and Y2 the CLOSE command to the 3-
position actuator.
The factory setting for the actuator's running time is 150 seconds. It can be
adjusted via parameter P44 (Y1 and Y2).
The parameter is only visible if 3-position is selected via DIP switch 5.
1. When the thermostat gets powered up, a closing command for the actuator's
running time + 150% is provided to ensure that the actuator fully closes and
synchronizes to the control algorithm.
2. When the thermostat calculates the positions "fully closed" or "fully open", the
actuator's running time is extended + 150% to ensure the right actuator
position synchronized to the control algorithm.
3. After the actuator reaches the position calculated by the thermostat, a waiting
time of 30 seconds is applied to stabilize the outputs.
The demand calculated by PI control from the current room temperature and set-
point is provided via Y1 to the valve actuator as a PWM signal (pulse width
modulation) for thermal actuators. The output is switched on for a period proportio-
nal to the heating/cooling demand and then switched off for the rest of the PWM
interval.
The interval is 150 seconds (factory setting). It can be adjusted via parameter P44
(Y1). The parameter is only visible if 2-position is selected via DIP switch 5.
For thermal valve actuators, set the running time to 240 sec.
· Never apply PWM to a motoric actuator
· It is not possible to ensure exact parallel running of more than 2 thermal valve
actuators. If several fan coils are driven by the same thermostat, preference
should be given to motoric actuators
For electric heaters, set the running time to 90 seconds.
To avoid burn-off of mechanical contacts by frequent switching, use a current valve
in place of a relay or contactor.
RDG400 Basic Documentation CE1P3182en
2015-05-20