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The actuating variables calculated by the control algorithm are output via the "Actuating variable heating" or
"Actuating variable cooling" communication objects. The control algorithm selected for the heating and/or cooling
operation determines, among other things, also the format of the actuating variable object. Thus, it is possible to
create 1-bit or 1-byte actuating variable objects.
The control algorithm is determined via the "Type of heating control" or "Type of cooling control" parameters on
the "Controller general" parameter page, possibly also for the additional stages.
Each of the following three algorithms can be selected:
1.
Continuous PI control:
A PI control is an algorithm consisting of a proportional and an integral part. A combination of these control
characteristics allows to accurately adjust the room temperature as fast as possible without or with only small
control deviations.
This algorithm lets the room temperature controller calculate a new continuous actuating variable periodically
every 30 seconds. This one will be output to the bus via a 1-byte value object, if the calculated actuating variable
has changed by a predetermined percentage. The "Automatic transmission if value changes by..." parameter on
the "Actuating variable and status output" parameter page determines the change interval in percent.
An additional PI controlled heating or cooling stage works exactly as the PI control of the basic stage. The
difference is that the setpoint will shift by taking into account the parameterized stage offset.
Characteristic feature of the PI control:
If the setpoint/actual value deviation of the room temperature results in an actuating variable of 100%, the room
temperature controller uses the maximum actuating variable until the determined room temperature reaches the
setpoint. This special control behaviour is known as 'clipping'.
This will quickly heat up or cool down the temperature in chilled or overheated rooms. In two stage heating or
cooling systems, this control behaviour also applies to the actuating variables of the additional stages.
07/17
Subject to change without notice
Variable (0 ... 100 %)
Integral part
Proportional part
instabus KNX/EIB System
Sensor
Time
2100-xx/2101 xx Page 37/82
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