Operating Instructions

Table Of Contents
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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
The fan speed is controlled by a PI controller depending on the control deviation of the
valve or reheater.
The fan starts running at the min speed when the valve or reheater demand exceeds
4%; it is deactivated when the demand is 0% (hysteresis).
Control strategy fan in sequence Control strategy fan in parallel
When the valve or/and electric reheater is fully open
AND the room temperature exceeds the fan offset
(P162, P163), the fan output signal grows up to the max.
value (P152, P154).
When the valve or electric reheater passes the fan
starting point (P160, P161), the fan output signal grows
up to the max value (P152, P154) in parallel to the valve
or electric reheater control deviation.
Note: ACS and ETS
For tool architecture reasons, the parameters
P162…P167 are visible but they have no function
In Comfort the min. values for heating and cooling can be defined separately (P153,
P155).
In Pre-comfort, Economy and Protection there is only one min. value for heating and
cooling (P156…P158).
In Comfort, Pre-comfort and Economy mode it is also possible to have the fan
running at min speed in the neutral zone.
In Comfort mode the hysteresis is between the two min. values (heating, cooling)
and between the heating setpoint and the center of the neutral zone.
In Pre-comfort and Economy mode, there is no hysteresis because there is only
one min. value.
Function
Sequence
Parallel
Fan speed in dead zone
100%
0%
Fan
Valve
S
maxH
S
minH
Sp
CCmf
Sp
HCmf
S
max
C
TR
S
min
C
Speed
4%
0%
FanStartDmd
Heat
FanStartDmd
Cool
100%
0%
Fan
Valve
S
maxH
S
minH
Sp
CCmf
Sp
HCmf
S
max
C
TR
S
min
C
X
PFanH
Ofs
FanH
X
PFanC
Ofs
FanC
Speed
4%
0%