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 2BFNC03 – Two-pipe fan coil with changeover and electric reheater 2013-06-07
Two-pipe fan coil with changeover
and electric reheater
FNC03
• Heating only (with LTHW), cooling only (with CHW) or changeover.
• Changeover signal via KNX bus.
• Modulating control of heating/cooling valve.
• Automatic or manual fan control.
Plant diagram
N1 Room controller.
R1 Room unit with temp.
sensor.
B1 Return air sensor.
D1 Window switch.
D2 Presence detector.
D3 Safety thermostat, electric
heating coil.
D4 Changeover signal via KNX
bus.
Q1 Fan (1...3 speeds).
YHC Heating/cooling valve.
YR Electric reheater.
10385S11
T
B1
Q1
N1
R1
D1 D2
T
YHC
D4
YR
D3
KNX
R
Operating diagrams
Valves
Changeover = Heating.
In "Heating" mode, the electric heating coil
operates as a reheater for LTHW heating, i.e.
only when the valve is fully open.
Changeover = Cooling.
In "cooling" the electric heating coil acts
as the only heating as soon as
temperature falls below SpH.
1-stage
OFF
TR [°C]
Y
ON
YR
H
10385D30
1 K
YHC
SpH
OFF
TR [°C]
ON
10385D31
SpH
YR
SpC
YHC
Y
C
Y Output signal.
TR Room temperature.
SpH Effective heating setpoint.
SpC Effective cooling setpoint.
H Heating sequence.
C Cooling sequence.
YHC Heating/cooling valve.
YR Contactor or solid state
relay for electric heating
coil.
Mod.
OFF
TR [°C]
ON
H
10385D32
YHC
SpH
YR
Y
0%
TR [°C]
100%
H
10385D33
SpH
YR
Y
SpC
YHC
C