Guidelines For Grounding And Wiring - Siemens Simatic S7-200 System Manual

S7-200 Programmable Controller System Manual

Guidelines for Grounding and Wiring

Proper grounding and wiring of all electrical equipment is important to help ensure the optimum operation
of your system and to provide additional electrical noise protection for your application and the S7-200.
Prerequisites
Before you ground or install wiring to any electrical device, ensure that the power to that equipment has
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been turned off. Also, ensure that the power to any related equipment has been turned off.
Ensure that you follow all applicable electrical codes when wiring the S7-200 and related equipment.
Install and operate all equipment according to all applicable national and local standards. Contact your
local authorities to determine which codes and standards apply to your specific case.
Warning
Attempts to install or wire the S7-200 or related equipment with power applied could cause electric
shock or faulty operation of equipment. Failure to disable all power to the S7-200 and related equipment
during installation or removal procedures could result in death or serious injury to personnel, and/or
damage to equipment.
Always follow appropriate safety precautions and ensure that power to the S7-200 is disabled before
attempting to install or remove the S7-200 or related equipment.
Always take safety into consideration as you design the grounding and wiring of your S7-200 system.
Electronic control devices, such as the S7-200, can fail and can cause unexpected operation of the
equipment that is being controlled or monitored. For this reason, you should implement safeguards that
are independent of the S7-200 to protect against possible personal injury or equipment damage.
Warning
Control devices can fail in an unsafe condition, resulting in unexpected operation of controlled
equipment. Such unexpected operations could result in death or serious injury to personnel, and/or
damage to equipment.
Use an emergency stop function, electromechanical overrides, or other redundant safeguards that are
independent of the S7-200.
Guidelines for Isolation
S7-200 AC power supply boundaries and I/O boundaries to AC circuits are rated 1500 VAC. These
isolation boundaries have been examined and approved as providing safe separation between AC line
and low voltage circuits.
All low voltage circuits connected to an S7-200, such as 24V power, must be supplied from an approved
source that provides safe isolation from AC line and other high voltages. Such sources include double
insulation as defined in international electrical safety standards and have outputs that are rated as SELV,
PELV, Class 2, or Limited Voltage according to various standards.
Warning
Use of non-isolated or single insulation supplies to supply low voltage circuits from an AC line can result
in hazardous voltages appearing on circuits that are expected to be touch safe, such as
communications circuits and low voltage sensor wiring.
Such unexpected high voltages could result in death or serious injury to personnel, and/or damage to
equipment.
Only use high voltage to low voltage power converters that are approved as sources of touch safe,
limited voltage circuits.
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