Grounding Question Continued...

[Timmkatt]

My prior question is posted below but after further evaluation here is more information on my server room electrical feed/ground. The secondary panel is fed from the main panel with 3 thick #4 stranded cables (Black insulator). There is a hot, a common and a third ground lead which is connected from the grounding bus in the secondary panel to the grounding bus in the main panel. The main panel has a #4 stranded bare copper cable from it's ground bus run to a metal cold water pipe nearby and a 4AWG solid bare copper cable connected to two 8'grounding rods and as mentioned in the original question below, the secondary panel also has a #4AWG solid copper running from it's ground bus to two 8' grounding rods. I'm not sure how much more grounding can be done but this seems like it should suffice to have the copper TGB in the rack bonded to the ground bus in the secondary panel and complete the loop. Wouldn't it be redundent to now run another cable from the grounding bar in the rack all the way to the main panel 80-90 feet away rather than the 8-10 feet to the grounding bus in the secondary panel since it is already connected to the grounding bus in the main panel via the third leg of the feed? I'll be consulting an electrician but want to be educated for future reference. Thank you

I previously posted this:
>>I'm setting up a new server room with one Rack. 2 servers will go into the rack and a new telephone system will also be installed in the rack in March which will require a #6 ground. The server room will be in a separate small stand alone building and is approximately 80 feet from the main service panel. There is a secondary panel fed from the main panel which in turn feeds the room. The secondary panel is on the building and is grounded with #4 solid copper going from the ground bus in the panel to 2 8' grounding rods. Is this a sufficient ground and if so can we have an electrician run a #6 stranded ground cable from the grounding bus bar on the rack to the grounding bus in the secondary panel or does it need to go all the way to the main panel? It does not seem practical to have to run it all the way to the main panel but I'm no an electrician so any help would be appreciated.<<

 

[trav87]

You should be fine with running your ground back to the secondary panel grounding bus. That secondary panel is what's distributing power to your outlets in the standalone building, so by grounding to that panel you are removing any potential ground difference.

 

[Timmkatt]

Thank you and you are absolutely correct. I had a licensed electrician out yesterday and he and our telecom provider confirmed that exact answer. He did the work right then and to remain in code he ran a #6 stranded w/green insulation in 1/2" pvc conduit from the secondary panel grounding bus on the west side of the building around the back wall to the east side of the building and through the wall right to the rack. The telecom provider will be terminating the ground on the rack next week when they terminate the network cables on the patch panel at the top of the rack. Even though I ran the network cabling for the ip phones that will be going in I'm being smart and having the telecom provider terminate and test both ends and the ground to eliminate any potential finger pointing when the Avaya IP office goes in if there are issues. Thanks again