Art. No. SC 1000 KNX
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It should be noted that the command value limit has no effect with "2-point feedback
control" and with "Transmitting of command values for heating and cooling via a common
object"! In that case it is still possible to configure the command value limit in the ETS, but it
will have no function.
The "Command value limit" parameter on the parameter page "Room temperature control ->
Controller general -> Command values and status output" defines the mode of action of the
limiting function. The command value limit can either be activated or deactivated using the 1-bit
communication object "Command value limit", or be permanently active. When controlling via
the object, it is possible to have the controller activate the command value limit automatically
after bus voltage return or an ETS programming operation. Here the "Command value limit after
reset" parameter defines the initialisation behaviour. In the "Deactivated" setting, the command
value limit is not automatically activated after a device reset. A "1" telegram must first be
received via the "Command value limit" object for the limit to be activated. In the "Activated"
setting, the controller activates the command value limit automatically after a device reset. To
deactivate the limit a "0" telegram must be received via the "Command value limit" object. The
limit can be switched on or off at any time using the object.
With a permanently active command value limit, the initialisation behaviour cannot be
configured separately after a device reset, as the limit is always active. In this case it is also not
possible to configure any object.
As soon as the command value limit is active, calculated command values are limited according
to the limiting values from the ETS. The behaviour with regard to the minimum or maximum
command value is then as follows...
-
Minimum command value:
The "Minimum command value" parameter specifies the lower command value limiting
value. The setting can be made in 5 % increments in the range 5 % ... 50 %. With an active
command value limit, the set minimum command value is not undershot by command
values. If the controller calculates smaller command values, it sets the configured minimum
command value. The controller transmits a 0% command value if no more heating or
cooling energy has to be demanded.
-
Maximum command value:
The "Maximum command value" parameter specifies the upper command value limiting
value. The setting can be made in 5 % increments in the range 55 % ... 100 %. With an
active command value limit, the set maximum command value is not exceeded. If the
controller calculates larger command values, it sets the configured maximum command
value.
If the limit is removed, the device automatically repositions the most recently calculated
command value to the unlimited values when the next calculation interval for the command
values (30 seconds) has elapsed.
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If the controller executes a valve protection function, the command value limit is temporarily
deactivated in order to make use of the full motion range of the valve.
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An active command value limit has a negative effect on the control result when the
command value range is very restricted. A control deviation must be expected.
Page 208 of 347
Software "Smart Control 501511"
Functional description
