Operating Instructions

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Siemens RXB (KNX) application library RXB Description of functions for FC-10, FC-11, FC-12, FC-13 CM110385en_08
Building Technologies Fan control 2013-06-17
9.3.4 Values representing fan speed
Besides operation via a PPS2 room unit, he 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
Type Receive timeout Value
R
W
K
T
U
0 1 1 0 0 1.003
DPT_Enable
no 0 = Disabled / Off
1 = Enabled / On
With FNC03 (electric re-heater) the fan must not be switched off while the re-heater is
active, and a fan overrun must be parameterized, in order to avoid overheating.
Fan command value (Input communication object)
Flags
Type Receive timeout Value
R
W
K
T
U
0 1 1 0 0 5.001
DPT_Scaling
no 0...100% 0 = 0%
255 = 100%
The commanded fan value via KNX bus is handled as an absolute value.
The displayed fan stage on the room unit will be calculated based on
the commanded fan value
the room temperature setpoint Comfort
the parameterized fan speed-ranges (Smin/Smax, heat/cool).
If a commanded fan value (X) results in different fan stages on the room unit for heating
and cooling, the switching will be in the middle of the two active comfort setpoints.
A hysteresis of 0.2 K is implemented to avoid jumping of the room unit cursor between
the stages.
Example with:
S1 = 5%, S2 = 50%, S3 = 80%
SminH = 20%, SmaxH = 80%, SminC = 30%, SmaxC = 100%
CO
Warning!
S
maxH
S
max
C
S
min
C
100%
0%
Sp
CCmf
Sp
HCmf
TR
Speed
(Sp
HCmf +
Sp
CCmf
)/2
0.2 K
0.2 K
X
23%
50%
80%
33.5%
65%
100%
S
minH