Bus Load Number E; Bus Power Supply; Distributed Bus Power - Siemens RXB Series Basic Documentation

Device data traffic
Introduction
Note
Devices with a bus
power supply
Notes
Caution!
For internal use only
Siemens
Building Technologies
2.1.3

Bus load number E

Bus load E, or E-characteristic, applies to the average data traffic of a device on
the bus.
The E-characteristic does not have to be calculated for a line containing the
allowed 64 bus devices (because the total E-characteristic is less than 300).
Bus load characteristic E of a device is indicated in the related data sheet.
2.2

Bus power supply

2.2.1

Distributed bus power

A bus power supply is always required for bus communications. There are two
options:
Distributed bus power
Central bus power supply
In any one line (including a main line) either the DPSU or PSU may be used.
The following devices are delivered factory-set with the bus power supply enabled,
and supply power to the bus.
Synco 700 RM...controllers DC 29 V, 25 mA
QAX9x3 central apartment unit
Since the devices which are factory-set to "Decentral bus power supply = On" are
distributed on the bus, they are referred to as "Distributed bus power supply units"
(DPSU).
Devices with the setting "Decentral bus power supply = On" must not be installed
on the same line as third-party devices. In such cases, the devices must be set to
"Decentral bus supply = Off" and a power supply unit must be installed (see next
section "Central bus power supply").
In devices with a bus power supply, the bus power section is electrically isolated
from the KNX bus.
In addition to its own intrinsic consumption, the QAX9x3 central apartment unit
when set to "Bus power = On" delivers the bus power supply for one OZW771
central communication unit or OZW772 web server, or for the OCI700 service
interface.
If other devices are installed on the same line, the central apartment unit must be
set to "Bus power supply = Off". In this case, the bus power must be supplied by
setting other devices such as the RM... controllers to "Decentral bus power supply
= Off", or by installing a power supply unit.
KNX bus communications
Engineering notes
DPSU = Decentral Power Supply Unit
PSU = Power Supply Unit
See the caution notice below .
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CE1P3127en
2013-04-08