We Wrote The Book on Grounding and Earthing

Toll Free: 888.367.0888

Ask The Experts Blog

What is the the advantage of isolating power supplies return from the unit, and ground the signal shields at the unit enclosure ground?

Hi Lenny,

Thank you for your question regarding shield grounding and power supply returns.  It is our pleasure to help.

The power supplies return path is commonly called the “neutral” conductor and is often a white wire.  While this wire must in fact be grounded at the first service disconnect, it may not be grounded at any other point in the system.  This is because the neutral wire actually carries as much current, if not more, than the hot wires carry.  Consider a Ground Fault Circuit Interrupter (GFCI); it works by detecting the difference between the hot and the neutral wires.  Any difference greater than a few milliamps results in the opening of the breaker.  The GFCI breaker is a great reminder to people that the neutral wire does in fact carry as much current as the hot wires.  This is why the return path (neutral) of the power supply is said to be “current-carrying”, or a “current carrying grounded conductor”. 

The shield wires are to be bonded to a non-current carrying grounded conductor (the green ground wire) in order to provide a path for stray currents, transients, and harmonics a path to the earth.  If you were to tie the shield wires of your data lines to the neutral, you would actually be forcing electrical energy on to the lines.  This is not only a violation of the National Electrical Code (NEC) but could damage the equipment tied to your data lines.


In conclusion, you must ensure that the power supplies return path is isolated from all other metallic objects, that you provide an effective non-current carrying ground path to the power supply, and that you ground your data lines in accordance to the manufacturer’s instructions. We recommend that you consult an electrician as to proper neutral and ground wire routing from the electrical panel to your power supply.

We hope you have found this information useful.  If you should have any further questions, please do not hesitate to call us at 310-318-7151 California time.

Best regards,

The Engineering Team at E&S Grounding Solutions


Photo credit: http://www.flickr.com/photos/40987321@N02/5580348753/sizes/l/in/photostream/

Leave a Reply