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Room temperature controller | Room temperature controller - General
(28)
Actual temperature (room temperature)
The controller evaluates the actual temperature (28) and compares it with the spe-
cified setpoint temperature (20). With the aid of the selected control algorithm (22),
the command value (23) is then calculated from the difference between the actual
and the setpoint temperature. The command value controls valves or fans for heating
or cooling systems (24), meaning that heating or cooling energy in the heat or cold
exchangers (25) is passed into the room (27). Regular readjustment of the command
value means that the controller is able to compensate for setpoint / actual temperat-
ure differences caused by external influences (26) in the control circuit. In addition,
the flow temperature of the heating or cooling circuit influences the control system
which necessitates adaptations of the variable.
The room temperature controller facilitates either proportional/integral (PI) feedback
control as a continuously working or switching option, or, alternatively, switching 2-
point feedback control. In some practical cases, it can become necessary to use
more than one control algorithm. For example, in bigger systems using floor heating,
one control circuit which solely triggers the floor heating can be used to keep the lat-
ter at a constant temperature. The radiators on the wall, and possibly even in a side
area of the room, will be controlled separately by an additional level with its own con-
trol algorithm. In such cases, distinction must be made between the different types of
control, as floor heating systems, in most cases, require control parameters which
are different to those of radiators on the wall, for example. It is possible to configure
up to four independent control algorithms in two-level heating and cooling operation.
The command values calculated by the control algorithm are output via the "Heating
command value" or "Cooling command value" communication objects. Depending on
the control algorithm selected for the heating and/or cooling mode, the format of the
command value objects is, among other things, also specified. In this way, 1-bit or 1-
byte command value objects can be created. The control algorithm is specified by the
parameters "Type of heating control" or "Type of cooling control" in the "Room tem-
perature control -> RTCx - General" parameter branch and, if necessary, also with a
distinction of the basic and additional stages.
Continuous PI control
PI control is an algorithm which consists of a proportional part and an integral part.
Through the combination of these control properties, you can obtain room temperat-
ure control as quickly and precisely as possible without or only with low deviations.
When you use this algorithm, the room temperature controller will calculate a new
continuous command value in cycles of 30 seconds and transmit it to the bus via a
1-byte value object if the calculated command value has changed by a specified per-
centage. The parameter "on change by (0 = inactive)" in the parameter branch
"Room temperature controller -> RTCx - General -> Command value output" spe-
cifies the change interval in percent.
Heating actuator 6-gang with controller | Order no. 2139 00 | 21393100
Page 125 of 257
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