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Siemens
RXB24.1 – Room controller
CM2N3874en_04
Building Technologies
02 Apr 2010
Engineering notes
The KNX / EIB Building Services Management Manual and system principles
supplement (see "Reference documentation ", page 10) contains the information
relevant for the engineering of the KNX / EIB bus (topology, bus repeaters, etc.)
and for the selection and dimensions of connecting cables for the supply voltage
and field devices.
The RXB24.1 room controller operates with a mains supply voltage of AC 230 V.
The controlled devices (valve actuators) receive their power directly from the
room controller. This means that a separate AC 24 V supply is not necessary for
the controllers and associated field devices.
The sizing and fuse protection of the power supply cables depends on the total
load and on local regulations. The power supply cables connected to the room
controller must be secured with cable restraints.
If serial wiring is applied on the terminal block 19/21, the connection will be inter-
rupted if the block is removed from the controller (the jumpers 19-19 and 21-21
are on the PCB, not in the block, see terminal diagrams on pages 11 and 12)
The supply cables must be secured with cable restraints.
The
simultaneous
load on outputs Y1 … Y4 must not exceed 9.5 VA.
Y1 (heating)
2 thermic valve actuators, type STP72E / STA72E 5 W
Y2 (cooling)
2 thermic valve actuators, type STP72E / STA72E 5 W
The maximum load is 9.5 VA for the heating sequence and 9.5 VA for the cooling
sequence.
This is acceptable because the two sequences never operate at the same time.
With low loads (< 2VA) the voltage tolerance may be greater than +20%
(see technical data).
AC 230 V
supply cables
AC 24 V triac outputs
Example:
