Siemens SIMATIC ET 200SP System Manual page 33

AUX bus (AUX(iliary) bus)
BaseUnits with additional AUX terminals (e.g. BU15-P16+A10+2D) enable the additional
connection of a potential (up to the maximum supply voltage of the module), which is applied
via the AUX bus.
The AUX bus can be used individually:
● As PE bar (the requirements according to EN 60998-1 apply). To comply with this
standard, a maximum of 8 I/O modules may be plugged into the corresponding potential
group.
● For additionally required voltage
NOTICE
AUX bus as PE bar
If you use an AUX bus as a protective conductor bar, attach the yellow-green color
identification labels to the AUX terminals, and establish a functional connection to the
central protective conductor connection.
If you stop using the AUX bus as a protective conductor bar, make sure you remove the
yellow-green color identification labels and remove the connection to the central protective
conductor connection again.
The AUX bus is designed as follows:
● Maximum current-carrying capacity (at 60 °C ambient temperature): 10 A
● Permitted voltage: depending on the BaseUnit type (see BaseUnit manual
(http://support.automation.siemens.com/WW/view/en/59753521))
Self-assembling voltage buses
You must feed the supply voltage L+ in via BaseUnit BU...D.
Each BaseUnit BU...B allows access to the supply voltage L+ via terminals (red/blue).
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF
Application planning
3.3 Forming potential groups
33