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
If the fan coil is equipped with a return air sensor, the fan has to run at least periodically
in order to measure a correct temperature. This running is activated by means of the
sensor selection (return air sensor). The fan running time and period can be defined,
see "Periodic fan kick", section 9.7.
With an active electric heater, min fan speed can not be lower than 10% (safety, see
page 102).
The fan is disabled when the controller specifies an electric heating output equal to 0
AND the minimum fan switch-on time has elapsed (P098, P159).
If the room operating mode changes (Comfort, Economy etc.) and the room
temperature is within the dead band after the change, the sequence controller is
reinitialized by the application. This implies:
Valve positions of 0%
Electric reheater disabled
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.
Please observe the safety notes on el. reheaters on page 102.
9.3.2 Automatic mode (FNC08 only)
Room supply air cascade control only supports the control strategy "fan in
sequence".
This means that parameters P162...P167 cannot be set.
The min fan speed values for Comfort, Pre-comfort, Economy and Protection
must be configured to > 0%.
At low energy demand, the following sequence overrides the minimum fan speed
setting to assure a smoother dynamic behavior of the fan. The sequence reduces
potential cold air flows by using higher air speeds, e.g.in cases of transient valve
positions / fan speeds. Thus the overall user comfort at low energy demand is
usually better.
Demand < 4%: Fan runs at min. fan speed for heating / cooling.
An overrun timer is started (6 min, fixed value).
Demand 0%: Fan keeps running at 10% speed (fixed value) if the overrun time
has not yet elapsed. Otherwise the fan stops.
Sequence and parallel
Fan coils with return air
sensor
FNC03
WARNING
STOP
Note!
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