Siemens RXB Series Basic Documentation page 18

Devices without a bus
power supply
Note
Rule of thumb
Optimization
Notes
18 / 88
Siemens
Building Technologies
Devices without a bus power supply
QAWZ40 room unit
RXB/RXL room controllers
Room thermostats RDG/RDF/RDU
RMZ792 bus operator unit
OZW771.xx central communication units
OZW772.xx web server
OCI700 service interface
Area/line couplers and IP router
Devices without a bus power supply require devices on the same line with a DPSU
or a power supply unit, PSU.
The rule is: One device with a DPSU can operate two devices without a bus power
supply plus the OCI700 service interface plus the OZW771 central communication
unit.
Per line, the rule is:
1 device with a DPSU + 2 devices with no bus power supply + OCI700 + OZW771
up to a maximum of
8 devices with a DPSU + 16 devices with no bus power + OCI700 + OZW771.
An RM... controller with a DPSU delivers a net current of 25 mA. This covers the
power consumption of 5 devices without a bus power supply (5mA each required).
8 devices with a DPSU on one line deliver 200mA. This covers the power
consumption for 40 devices or 38 devices plus OCI700 plus U/W771.
Even with devices having a low current requirement (< 3 mA), the number of
devices in a line must not exceed 64.
See the data sheets for the power consumption of the new Synco devices.
KNX bus communications
Engineering notes
For internal use only
CE1P3127en
2013-04-08