Siemens SIMATIC S7 System Manual page 57

Ensure that you follow all applicable electrical codes when wiring the S7-1200 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.
Installation or wiring the S7-1200 or related equipment with power applied could cause
electric shock or unexpected operation of equipment. Failure to disable all power to the S7-
1200 and related equipment during installation or removal procedures could result in death,
severe personal injury, and/or damage due to electric shock or unexpected equipment
operation.
Always follow appropriate safety precautions and ensure that power to the S7-1200 is
disabled before attempting to install or remove the S7-1200 or related equipment.
Always take safety into consideration as you design the grounding and wiring of your S7-
1200 system. Electronic control devices, such as the S7-1200, 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 S7-1200 to protect against
possible personal injury or equipment damage.
Control devices can fail in an unsafe condition, resulting in unexpected operation of
controlled equipment. Such unexpected operations could result in death, severe personal
injury and/or property damage.
Use an emergency stop function, electromechanical overrides, or other redundant
safeguards that are independent of the S7-1200.
Guidelines for isolation
S7-1200 AC power supply boundaries and I/O boundaries to AC circuits have been designed
and approved to provide safe separation between AC line voltages and low voltage circuits.
These boundaries include double or reinforced insulation, or basic plus supplementary
insulation, according to various standards. Components which cross these boundaries such
as optical couplers, capacitors, transformers, and relays have been approved as providing
safe separation. Isolation boundaries which meet these requirements have been identified in
S7-1200 product data sheets as having 1500 VAC or greater isolation. This designation is
based on a routine factory test of (2Ue + 1000 VAC) or equivalent according to approved
methods. S7-1200 safe separation boundaries have been type tested to 4242 VDC.
The sensor supply output, communications circuits, and internal logic circuits of an S7-1200
with included AC power supply are sourced as SELV (safety extra-low voltage) according to
EN 61131-2.
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
WARNING
WARNING
96BInstallation
3.4 Wiring guidelines
57