Operating Instructions

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Siemens RXB application library (KNX) RXB – Fan coil applications from FC-10, FC-11, FC-12, FC-13 CM110672en_05
Building Technologies 8BFNC18 – Two-pipe fan coil (changeover) and radiator 2013-06-07
Two-pipe fan coil (changeover) and radiator
FNC18
• Heating/cooling coil: heating only (with LTHW), cooling only (with CHW) or
changeover.
• Changeover signal via KNX bus.
• Outside air temperature sensor via KNX bus.
• Heating with LTHW radiator.
• Downdraft compensation
• Modulating control of heating/cooling valve and radiator valve.
• Automatic or manual fan control.
Plant diagram
N1 Room controller.
R1 Room unit with temp.
sensor.
B1 Return air sensor.
B2 Outside temp. via KNX bus.
D1 Window switch.
D2 Presence detector.
D3 Changeover signal via KNX
bus.
Q1 Fan (1… 3-speed).
YH Heating valve (radiator).
YHC Heating/cooling valve (fan
coil).
10385S21
B1
YHC
Q1
N1
R1
D1 D2
T
YH
T
D3
B2
T
T
KNX
R
Operating diagrams
100
0
TR [°C]
Y [%]
SpH SpC
YH
H
C
100
0
TR [°C]
Y [%]
SpH SpC
Change-over (Fan-Coil)
YHC
H
C
10385D50
YHC
Heating sequence:
The heating coil in the fan coil system operates
in sequence with the radiator, i.e. the
heating/cooling valve is only operated after the
radiator valve is fully open (thermal valves are
operated in alternation, because fully open
here means 1 second ON / 1 second OFF).
Cooling sequence:
Control of heating/cooling valve.
Y Output signal.
TR Room temperature.
SpH Effective heating setpoint.
SpC Effective cooling setpoint.
H Heating sequence.
C Cooling sequence.
YH Heating valve (radiator).
YHC Heating/cooling valve (fan
coil).
Q14 Fan speed 1.
Q24 Fan speed 2.
Q34 Fan speed 3.
10385D51
Change-over
TR [°C]
Y
H
C
Q14
Q24
Q34
SpH SpC