Siemens RDG20 KN Series Basic Documentation page 101

Synchronization
PWM control
(RDG20..KN only)
Note
PWM for valve actuators
(RDG20..KN)
Note
PWM for electric heaters
(RDG20..KN)
Note
DC 0...10 V control
A6V11545892_en--_c
1. When the thermostat is powered up, a close command for the actuator run time
by + 150 % is issued to ensure the actuator closes fully and synchronizes to
the control algorithm.
2. When the thermostat calculates the positions "fully close" or "fully open", the
actuator run time is extended by + 150 % to ensure the correct actuator
position is 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 from the current room temperature and setpoint is supplied
via Y1, Y2, Y3 and Y4 to the valve actuator as a PWM (pulse width modulation)
signal for thermal actuators. The control output is activated for a period
proportional to the heating/cooling demand and then switched off for the rest of the
PWM interval.
The PWM algorithm cycle time is 1200 seconds (factory setting). It can be adjusted
via P206 (Y1), P207 (Y2), P208 (Y3) or P209 (Y4). These parameters are only
displayed if PWM is selected via DIP switches 7 and 8 and if PWM is selected via
P201, P203, P204, P205.
●
For a more accurate control temperature with PWM signals, the integral action
time (P057 and P058) must be set to 0 (Proportional control).
●
For P-band (P050, P052, P054), see Control sequences [➙ 75].
For thermal valve actuators (STA, STP), set the PWM algorithm cycle (P206, P207,
P208, P209) to 1200 seconds. Proposed setting range for optimization: 900 to
1800 seconds.
●
It is impossible to ensure exact parallel running of 2 or more thermal valve
actuators. Motorized actuators with On/Off or 3 position control take
precedence if several fan coil systems are controlled by the same room
thermostat.
To control electrical equipment, we recommend using a suitable external switching
element to switch the maximum current.
If output Y2 controls external mechanical relays, the optimal run time (P207)
depends on the technical characteristics of the equipment.
As initial setting, we suggest the following values, which can be modified within the
described setting range as needed:
●
Electric heater applications:
●
Electric radiator applications:
●
Electric floor heating:
If output Y2 controls one external solid state relay:
●
Electric heater applications:
●
Electric radiator applications:
●
Electric floor heating:
To avoid burn-off of mechanical contacts by frequent switching, use a current valve
in place of a relay or contactor.
To avoid possible supply problems, when many consumers are switching on at the
same time in a building, consider the following:
●
Set slightly different PMW cycles
●
Do not switch all rooms to Comfort at the same time
This function is available with RDG26..KN only.
300 s (5 min) / range 30...60 s
1200 s (20 min) / range 120...1800 s (30 min)
1200 s (20 min) / range 30...1800 s (30 min)
60 s / range 15...60 s
300 s (5 min) / range 30...300 s (5 min)
600 s (10 min) / range 30...900 s (15 min)
Functions
4
Control outputs
101 | 180