Installing The Field Wiring; General Guidelines - Siemens SIMATIC S7-200 System Manual

2.3

Installing the Field Wiring

Warning
!
Attempts to install or remove S7-200 CPUs or related equipment when they are
powered up could cause electric shock or faulty operation of equipment.
Failure to disable all power to the S7-200 CPUs and related equipment during
installation or removal procedures may result in death or serious personal injury,
and/or damage to equipment.
Always follow appropriate safety precautions and ensure that power to the S7-200
is disabled before installing field wiring.

General Guidelines

The following items are general guidelines for designing the installation and wiring
of your S7-200 Micro PLC:
Ensure that you follow all applicable electrical codes when wiring the S7-200
Micro PLC. 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.
Always use the proper wire size to carry the required current. The S7-200
accepts wire sizes from 1.50 mm
Ensure that you do not over-tighten the connector screws. The maximum
torque is 0.56 N-m (5 inch-pounds).
Always use the shortest wire possible (maximum 500 m shielded, 300 m
unshielded). Wiring should be run in pairs, with a neutral or common wire paired
with a hot or signal-carrying wire.
Separate AC wiring and high-energy, rapidly switched DC wiring from
low-energy signal wiring.
Properly identify and route the wiring to the S7-200, using strain relief for the
wiring as required. For more information about identifying the terminals, see the
specifications in Appendix A.
Install appropriate surge suppression devices for any wiring that is subject to
lightning surges.
External power should not be applied to an output load in parallel with a DC
output point. This may cause reverse current through the output, unless a diode
or other barrier is provided in the installation.
S7-200 Programmable Controller System Manual
A5E00066097-02
Installing an S7-200 PLC
2 2
to 0.50 mm (14 AWG to 22 AWG).
2-9