semaphore KINGFISHER PLUS+ Hardware Reference Manual page 247

Kingfisher Plus+ Hardware Manual
Safety Earth / Ground
Although safety of the Power Supply Module and other modules with the potentially
hazardous voltage levels have been assessed and found to be in compliance with the
appropriate requirements, an additional level of protection from a potential electrical shock
can be provided by connecting the RTU backplane to the safety earth / ground.
The Earth / Ground rail of the backplane PCB can be grounded by mounting screws to the
metal back-plate of the backplane when properly installed. Additional grounding wire straps
should be used in case reliable screw connections cannot be assured. Earth / Ground
connections should be made from one of the PCB mounting tabs to a system earth / ground
terminal (usually a threaded stud) using a minimum AWG#12 wire and ring terminals. Use of
a nut and star washer for each wire on the ground connection lug is recommended to ensure
adequate grounding. Ensure the paint coating is removed under the lug to make good
electrical contact.
All backplanes grouped together in a RTU system must have a common ground connection.
This is especially important for backplanes that are not mounted in the same enclosure.
The best way to provide proper ground connections is to ensure that the RTU backplane
metal frame is directly connected to the mounting panel (or rear plate) by connecting a
ground strap from one of the ground lugs on either side of the backplane to the mounting
panel or cabinet in accordance with local safety requirements.
Functional Earth / Ground
Yellow / Green wire in the mains power cord provides only functional (NOT Safety) Earth /
Ground connection and cannot be relied upon for safety purposes.
Hardware Manual Version 7.16 http://www.servelec-semaphore.com/ Page 247