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Siemens
RXB (KNX) application library
FNC Description of functions for FC-10, FC-11, FC-12
CM110385en_05
Building Technologies
Fan control
28 Feb 2009
The fan runs at
fan speed 1
for
as long as the heating/cooling valve remains partly
open, or in the case of an electric heater, while the heater is in operation.
•
It is enabled as soon as the controller specifies a valve position or an electric
heating output greater than 0.
•
It is disabled when the controller specifies a valve position or electric heating output
equal to 0 and the minimum fan switch-on time has elapsed.
When the valve is fully open or the electric heater is operating at 100% (in the range
marked "a"), a
sequence controller
enables
fan speeds 2 and 3
.
In addition to the control deviation, an
integrator
also comes into operation in the
range marked "a". This ensures that the fan switches to speed 2 (and later to speed 3)
if the control deviation has remained >0 for a period of time, even if the room
temperature has not reached the switching point for fan speed 2.
The fan does not switch back down to speed 2 and later to speed 1 until there has been
no control deviation for a period of time.
If the
room operating mode changes
(
Comfort, Economy etc.),
the sequence
controller is reinitialized by the application. This produces the following response: If the
room temperature is within the dead band after the change of room operating mode,
the controller specifies valve positions of 0%, or in the case of electric heaters, these
are disabled, and the fan is switched off. However, any delay time (minimum switch-on
time, switch-off delay in conjunction with electric heating coil / reheater or
periodic fan
kick
) is allowed to expire first.
Controller
Outputs required
RXB21.1
RXB22.1
3
Q14
80283
Q24
Q34
1. Stufe
2. Stufe
3. Stufe
1 ... 3-stufiger Ventilator
The fan can also be operated via the KNX bus.
In S-mode, control is shared between two communication objects:
–
Fan command value
–
Enable fan command value
(activates input
Fan command value
).
When
Enable fan command value
is
disabled,
the controller controls the fan
automatically, and the
Fan command value
input is disabled.
Enable fan command value
(Input communication object)
Flags
R W K T U
Type Receive
timeout
Value
0 1 1 0 0 1.003
DPT_Enable
no
0 = Disabled / Off
1 = Enabled / On
Fan command value (Input communication object)
Flags
R W K T U
Type Receive
timeout
Value
0 1 1 0 0 5.001
DPT_Scaling
no
0...100% 0 = 0%
255 = 100%
Controller outputs
KNX
R
CO
