Siemens SIMATIC PC 670, Equipment Manual

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Starting Up the Computing Unit
Release 04/02
2-7
Panel PC 670 Computing Unit, Equipment Manual
2.3 Ensuring Readiness for Service
Measures for equipotential
Low-resistance grounding connections ensure that the user of the installation is
protected against electric shock (for example, if a short-circuit occurs or if there are
defects in the system). Moreover, they discharge interference transmitted by
external power supply cables, signal cables or cables to I/O devices.
You should therefore create a low-resistance connection (a large surface acting as
the contact) between the grounding point on the system housing and the central
grounding point of the cabinet or the installation in which the computer is to be
installed. The minimum cross-section should not be less than 5 mm
2
.
The grounding terminal is located on the side of the device and is identified by a
symbol.
Connection to the power supply
Power supply connection
Unit power plug
Figure 2-2 Power supply connection (device socket for non-heating appliances)
!
Caution
The computing unit is equipped with a safety-tested power supply cable and may
be connected only to a socket outlet with grounding contact.
Make sure that the socket outlet on the device or the socket outlet with grounding
contact of the building wiring system is freely accessible and located as near to the
device as possible.
The computing unit does not have a mains switch. To completely disconnect the
PC from the mains power supply, you must pull the plug. This connection must be
easily accessible.
If the PC is to be installed in a cabinet, a central disconnector must be provided.