Bus Power Supply; Decentral Bus Power Supply - Siemens Synco 700 Series Basic Documentation

Introduction
Note
Devices with bus power
Notes
Caution!
Devices without a

bus power supply

Note
Building Technologies
HVAC Products
2.2 Bus power supply
2.2.1

Decentral bus power supply

A bus power supply is always required for bus communications. There are two
options:
• Decentral bus power supply DPSU = Decentral Power Supply Unit
• 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 "Decentral bus power supply =
On" and supply power to the bus:
• Synco 700 type RM...controllers
• OZW775 central communication unit DC 29 V, 25 mA
• QAX910 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 "Decentral bus power supply, 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 power 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 QAX910 central apartment unit
when set to "Bus power supply = On" delivers the bus power for one OZW771
central communication unit 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.
Devices without a bus power supply:
• QAW740 room unit
• RXB/RXL room controllers
• RMZ792 bus operator unit
• OZW771.xx central communication units
• 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.
Basic documentation: Communication via the KNX bus
Engineering notes
PSU = Power Supply Unit
DC 29 V, 25 mA
See the warning note below, marked
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CE1P3127en
30.08.2007