
Application manual
KNX room temperature controller EK-EQ2-TP
Release 3.00 - Updating: 27/06/2017
Application Manual
© SBS S.p.A. - All rights reserved
Page 84
The integral time is the time required to repeat the value of the control variable of a purely proportional regulator, when
the error remains constant in time.
For example, with a purely proportional controller in heating and with a value of proportional band of 4 K, if the setpoint is = 20°C
and the measured temperature is = 18°C, the control variable assumes the value of 50%. With an integral time = 60 minutes, if the
error remains constant, the control variable will take the value = 100% after 1 hour, i.e. a contribution equal to the value given by
only proportional contribution will be added to the control variable.
In heating and air conditioning systems, a purely proportional controller is not able to guarantee the achievement of the setpoint.
You should always introduce an integrated action for achieving the Setpoint: that is why the integral action is also called automatic
reset.
9.1.1.3
PWM Proportional-Integral control
The PWM (Pulse Width Modulator) proportional-integral controller uses an analog control variable to
modulate the duration of the time intervals in which a binary output is in the ON or OFF state. The controller
operates in a periodic manner over a cycle, and in each period it maintains the output to the ON value for a
time proportional to the value of the control variable. As shown in the figure, by varying the ratio between the
ON time and the OFF time, the average time of activation of the output varies, and consequently the average
heating or cooling power supplied to the room.
T room [°C]
0%
100%
T Setpoint
T room [°C]
T Setpoint
Tight proportional band
50%
Wide proportional band
0%
100%
50%
Tight proportional band
Wide proportional band