Siemens SIMATIC S7-400 Hardware And Installation Manual page 65

With ...
stationary equipment and
systems without all-pole
disconnector
load power supplies and
power supply modules
all circuits of the S7-400
residual-current devices
(RCDs)
24 VDC supply
The following table shows the points you must observe when connecting the
S7-400 to a 24 VDC supply.
With ...
buildings
24 VDC supply cables and
signal lines
24 V supply
load power supplies
Protection Against External Electrical Effects
The following table shows what you must observe for protection against external
electrical effects.
With ...
all plants and systems in
which the S7-400 is
installed
connecting cables and
signal lines
signal lines
S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01
www.gkbpx.com
... you must ensure ...
that a supply disconnector (switch) is installed in the
building.
that the set line voltage range corresponds to the local line
voltage.
that fluctuations of line voltage from the rated value are
within permissible tolerances (see Technical Data of the
modules).
that the RCD is suitable for the total discharge currents of
the power supply module.
... you must ensure ...
that suitable external lightning protection measures are
provided.
that suitable internal and external lightning protection
measures are provided.
that the supply voltage produced is an isolated extra-low
voltage.
that only isolated load current power supplies are used.
... you must ensure ...
that the plant and all system sections are properly
connected to protective ground to discharge
electromagnetic interference.
that all cables are correctly routed and connected.
that an open circuit in a signal line does not place the
equipment in an undefined state.
Wiring the S7-400
4-3