Grounding of IT Equipment Branch Circuits 1

[richanton]

I searched on this, but didn't find a real answer. If I run multiple circuits in the same conduit, and my practice is to run an insulated ground with the phase conductors, should I be running multiple ground conductors. Some references say YES. I personally think it's overkill. Any opinions.

As an example, I am running 4 - 208v, 1phase,30A services in a single conduit(derated as necessary). My design engineers want to run 4 separate ground conductors in the conduit.

 

[resqcapt19]

250.122(C) in the NEC permits the use of a single equipment grounding conductor. It would be sized based on the largest overcurrent protective device for the ungrounded conductors in the raceway. Note, this assumes that you are asking about the equipment grounding conductor and not the grounded (neutral) conductor.

 

[richanton]

Yes, I am referring to the grounding conductor. I know NEC allows it. I was asking more if this is done from an IT equipment noise standpoint.

 

[ghostbuster7]

IT eqpt has "typical type corcom" filters in it that bleed current to ground.
Racks and racks of eqpt can add up to sometimes a couple of amps returning on the ground.
This creates an IR drop and voltage potential differences between racks.
Signal grounds between eqpt. will now have current flow and thus possible signal contamination (noise).

The lower you can keep the ground impedance.the smaller is this IR drop.Therefore,yes the more parallel grounds is better(lower impedance).

 

[rob46]

Ghostbuster,

Thank you for the information. Are corcom filters used in the server room equipment? Does all IT equipment provided with corcom filters?