Siemens SCALANCE W784-1 Compact Operating Instructions page 80

Connecting up
5.1 Lightning protection, power supply, and grounding
Safety extra low voltage
WARNING
Danger to life from overvoltage, fire hazard
SCALANCE W-700 devices are designed for operation with a directly connectable safety
extra-low voltage or with the power supply adapters available as accessories (available
only for the SCALANCE W786-xPRO device). Therefore only safety extra-low voltage
(SELV) with limited power source (LPS) complying with IEC950/EN60950/VDE0805 may
be connected to the power supply terminals (exception: Power supply adapter for 110 - 230
V AC for the SCALANCE W786-xPRO).
Measures must be taken to prevent transient overvoltages of more than 40% of the rated
voltage. This is the case if the devices are operated exclusively with SELV (Safety Extra
Low Voltage).
The power supply unit to supply the SCALANCE W-700 must comply with NEC Class 2
(requirements of class 2 for power supply units of the "National Electrical Code, table 11
(b)") or SELV with LPS (Limited Power Source) EN 60950-1. If the power supply is
designed redundantly (two separate power supplies), both power supplies must meet these
requirements.
Exceptions:
• Power supply with PELV (according to VDE 0100-410 or IEC 60364-4-41) is also
possible if the generated rated voltage does not exceed the voltage limits 25 V AC or 60
V DC.
Earthing
CAUTION
Damage to the device due to potential differences
To avoid the influence of electromagnetic interference, the device should be grounded.
There must be no potential difference between the following parts, otherwise the device or
other connected device could be severely damaged:
• Housing of the SCALANCE W-700 and the ground potential of the antenna.
• Housing of the SCALANCE W-700 and the ground potential of a device connected over
Ethernet.
• Housing of the SCALANCE W-700 and the shield contact of the connected Ethernet
cable.
Connect both grounds to the same foundation earth or use an equipotential bonding cable.
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SCALANCE W-784-1xx / SCALANCE W-74x-1
Operating Instructions (Compact), Release 08/2007, A5E01174713-02