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Siemens
RXB (KNX) application library
FNC Description of functions for FC-10, FC-11, FC-12
CM110385en_05
Building Technologies
Control sequences
28 Feb 2009
8.1.4
Actuator type selection
All actuators have threads suitable for fitting to both normally-closed (push to open) and
normally-open (pull-to-open) valves. However, the RX applications do not support
inverse control, which means that only actuators with a pulling action can be used with
"pull-to-open" valves and only actuators with a pushing action can be used with "push-
to-open" valves. This is why, in RX applications, valves with mounted actuators are
always closed when de-energized.
Different applications support different valve actuators, and these do not all require the
same number of outputs on the controller.
– Thermal actuators are driven with an AC 24 V PDM signal
– Motorized actuators with an AC 24 V 3-position signal.
– Electromechanical actuators (motors with spring return) have a special PDM
algorithm that ensures that 50 position changes per day are not exceeded.
This causes a slower control behavior.
Thermal and electromechanic actuators thus require one output, motorized actuators
two.
The table below shows the possible combinations:
System
Actuator
type
Controller
Outputs required
Four-pipe fan coil (thermal)
RXB21.1
RXB22.1
Heizen
Kühlen
80261
Y1
Y2
(motorized)
RXB21.1
M
M
Heizen
Kühlen
Y1
Y2
Y3
Y4
80262
Electro-
mechanic
(ON / OFF)
RXB21.1
RXB22.1
Heizen
Kühlen
Y1
Y2
M
M
Two-pipe fan coil
(thermal)
RXB21.1
RXB22.1
Heizen oder Kühlen
80263
Y1
(motorized)
RXB21.1
RXB22.1
M
Heizen oder Kühlen
Y1
Y2
80264
Electro-
mechanic
(ON / OFF)
RXB21.1
RXB22.1
Y1
M
Heizen oder Kühlen
The RXB2… room controllers also support the use of motorized EIB/KNX bus
actuators. In the tool, select
Bus motorized
.
STOP
Note!
Directly connected
valve actuators
Motorized
KNX/EIB bus actuators
