Controller Type: Proportional - Integral (Pi); Valve Control By Pwm Method - Rehau NEA SMART 2.0 Service Manual

4.6.2 Controller type: Proportional – Integral (PI)
Room temperature control works on base of a proportional – integral
(PI) controller. The proportional part of the control signal gives an
immediate reaction when the difference between set point and actual
value changes.
The integral part changes slowly and has the objective to eliminate the
remaining difference between set point and actual value. To avoid
negative effects, caused by the thermal storage of the used system,
there are some special rules implemented, how the I-part is
calculated.
Relevant parameters
Web page:
Home  Installer  Settings  Control
App:
Settings  Installer  Control parameter  Rooms
4.6.3

Valve control by PWM method

The calculated controls signal, which is a value from 0 % to 100 %, is
transferred to the puls-width-modulation (PWM) method.
PWM method means, that the valves of the manifold, which control
the flow of heating and cooling medium, are opened in a percentage
of the PWM cycle time, which is equivalent to the control signal
calculated by the PI controller.
Figure 4-3 shows a control signal of 100 %, 50 % and 20 % and the
principle how it is transferred to a PWM signal.
Fig. 4-3 Control signal and corresponding PWM signal
There are minimum times to switch the thermal actuators for the
valves on or off which have its reason in the opening and closing
times of the actuators.
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Typical cycle times are 20 minutes for floor and wall systems, 10
minutes for ceiling systems.
Relevant parameters
Web page:
Home  Installer  Settings  Control
App:
Settings  Installer  Control parameter  Rooms