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System-wide functions
* Only in systems Anl 4 to 7
Note!
The control mode is configured separately in Co2 -> Fb14 or Fb15 for the separate heating cir-
cuit in systems Anl 1 to 3 (Co5 -> Fb13 = ON).
8.11.1 Three-step control
The set point can be controlled using a PI algorithm. The valve reacts to pulses that the controller
emits when a system deviation occurs. The length of the first pulse. in particular, depends on the
extent of the system deviation and the selected Proportional gain K
(the pulse length increases
P
as K
increases). The pulse and pause lengths change continuously until the system deviation
P
has been eliminated. The pause length between the single pulses is greatly influenced by the Re-
set time T
(the pause length increases as T
increases).
N
N
The Transit time T
specifies the time required by the valve to travel through the range of 0 to
Y
100 %.
8.11.2 On/off control
The output signal of the controller is switched on or off.
Depending on the controlled variable, the output signal is switched on or off when the tempera-
ture falls below or exceeds the required set point by T = 0.5 x Hysteresis . The greater the Hyster-
esis selected, the less the signal is switched on and off. The Minimum activation time and Mini-
mum deactivation time determine the time interval between changes in the output signal.
8.11.3 Continuous control
The set point can be controlled using a PID algorithm. The valve receives an analog 0 to 10 V
signal from the controller. The proportional component causes an immediate change in the 0 to
10 V signal when a system deviation occurs (the greater the K
, the greater the change). The in-
P
tegral-action component only comes into effect when a certain time has passed: T
stands for
N
the time passing until the integral-action component has changed the output signal to the extent
that the proportional component directly changed the signal (the greater the T
, the slower the
N
rate of change). The derivative-action component determines how strongly a change in the sys-
tem deviation affects the output signal (the greater the T
, the stronger the change).
V
58
EB 5474 EN
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