Gira KNX 2139 00 Product Documentation page 130

Room temperature controller | Room temperature controller - General
y: Command value
x : control difference (x
d
P = 1/K : Configurable proportional band
K = 1/P : Gain factor
T : parameterisable reset time
N
PI control algorithm: Command value y = K x
Deactivation of the reset time (setting = "0") ->
P control algorithm: Command value y = K x
Parameter
setting
P: Small proportional
range
P: Large proportional
range
T : Short reset time
N
T : Long reset time
N
Effects of the settings for the control parameters
2-point feedback control
2-point feedback control represents a very simple temperature control. For this type
of feedback control, two hysteresis temperature values are set. The actuators are
triggered by the controller via switch-on and switch-off command value commands
(1-bit type). A constant command value is not calculated for this type of control.
The room temperature is also evaluated by this type of control in cycles every 30
seconds. Thus the command values change, if required, only at these times. The dis-
advantage of a continuously varying temperature as a result of this feedback control
option is in contrast with the advantage of this very simple 2-point room temperature
control. For this reason, quick-reaction heating or cooling systems should not be
Heating actuator 6-gang with controller | Order no. 2139 00 | 21393100
Image 28: Function of the command value of a PI control
= x - x
d set act
)
[1 + (t / T
d
d
Effect
Large overshoot in case of setpoint
changes (possibly permanently), quick
adjustment to the setpoint
no (or small) overshooting but slow ad-
justment
Fast compensation of control deviations
(ambient conditions), risk of permanent
oscillations
Slow compensation of control deviations
)]
N
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