Operating instructions

Connecting up
SCALANCE W788-xPRO / W74x-1PRO/RR
A5E02280448-02, Release 11/2008
39
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 100 - 240 V AC for the SCALANCE W786-xPRO).
Take measures to prevent transient voltage surges of more than 40% of
the rated voltage. This is the case if you only operate devices 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.
Redundant power supply
CAUTION
Setup with redundant power supply (Power over Ethernet + 24 V DC or 48 V DC)
To use a redundant 24 V power supply (or 48 V with SCALANCE W786) and Power
over Ethernet (PoE), a separate floating 24 V source (or 48 V source for W786)
must be available for each SCALANCE W-700. Otherwise there is no longer
isolation of the input voltages of different devices required for the PoE function and
functionality may be disturbed.