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2.2.2 Grounding Requirements
Chassis ground must be used. DC ground is not directly coupled to Earth ground
internally. It is preferable not to ground DC negative return to chassis ground as poor
site earths can introduce noise into a system, but if necessary an earth connection
should be made, from the power supply return point to the central star earth point.
Ground conductors should be as short and as large in size as possible. The conductors
must always be large enough to carry the maximum short circuit current of the path
being considered. Ground conductors should be connected to a tree from a central star
earth ground point. This ensures that no ground conductor carries current from any
other branch.
2.2.3 CE Requirements
To make an NP-600S comply with EMC directives, and to reduce susceptibility to
electrical interference, a separate #14 AWG ground wire should be taken to the chassis
ground terminal of the power connector. This ground connection should be run
directly to the central star earth connection point (as recommended in most
Installation Instructions).
2.2.4 Safety Guidelines
This section presents recommended installation practices, and procedures. Since no
two applications are identical, these recommendations should be considered as
guidelines.
Hardware Considerations WARNING!
The system designer should be aware that devices in Controller systems could fail and
thereby create an unsafe condition. Furthermore, electrical interference in an operator
interface, such as an NP-600S, can lead to equipment start-up, which could result in
property damage and/or physical injury to the equipment operator.
If you, or your company, use any programmable control systems that require an
operator or attendant, you should be aware that this potential safety hazard exists and
take appropriate precautions. Although the specific design steps depend on your
particular application, the following precautions generally apply to installation of
solid-state programmable control devices. In addition, these precautions conform to
the guidelines for installation of Controllers as recommended in the NEMA ICS 3-304
Control Standards.
