Isolated grounding on UPS loads

[nullsig]

I work at an industrial facility and we are replacing ~20 year old UPS systems that provide power to critical process control equipment, network racks, and servers.

Currently these systems/loads are not on an isolated ground but the question was raised as to if we should implement an isolated ground when replacing the old UPSs.

Is there a convention or recommendation for when isolated ground is appropriate? As I said before, these systems have been in for ~20 years and we haven't had any grounding or noise related issues to date. However, I feel newer electronic systems are becoming more sensitive so it is prudent to address the issue.

Some of these loads are "dual sourced"- they have ATSs with normal power and UPS power inputs, or particular equipment might actually have two separate power inputs/power supplies for UPS and normal. Are there any consequences or considerations for dual fed loads when one of the sources is on isolated ground and the other is not?

 

[ron]

Newer equipment and associated communications are more immune to common mode noise and IG are generally not done anymore. Sometimes on an audio system or and old point of service computer system, the manuf will require it, but it isn't done in data centers anymore, so your plant probably doesn't need it either.

 

[nullsig]

Newer equipment and associated communications are more immune to common mode noise and IG are generally not done anymore. Sometimes on an audio system or and old point of service computer system, the manuf will require it, but it isn't done in data centers anymore, so your plant probably doesn't need it either.

Thanks for the response. Do you happen to have any literature or articles on how IG is being phased out due to increased equipment tolerances? It would help support the discussion we are having here.

 

[iwire]

Thanks for the response. Do you happen to have any literature or articles on how IG is being phased out due to increased equipment tolerances? It would help support the discussion we are having here.

It just is not needed anymore due to the fact that modern equipment is not interconnected with cables that carry the ground from one piece of equipment to the other. Coax, IBM, RS232 etc all carried the ground with them. Cat 5, cat 6, fiber etc do not.

Often IG is more voodoo than real need.

As Ron mentioned audio systems can be an exception because they still do use cabling that carries the ground between equipment which can result on current flow and audible hum on the system.

 

[ron]

Do you happen to have any literature or articles on how IG is being phased out due to increased equipment tolerances? It would help support the discussion we are having here.

You can google it and find a bunch of references. This is an article that just describes the use.
http://ecmweb.com/content/demystifying-isolated-grounding-systems-part-1