grounding / Bonding for Racked equipment

[maxelrod]

In a data center containing equipment racks with servers, etc, it has always been my position to ground the rack, and bond the
cases of all equipment to the rack using a suitable bonding wire.

This complies with NEC 645.15

"All exposed noncurrent-carrying metallic parts of an information technology system has to be grounded as noted in Article 250"

and NEC 250.4 (2)

"Any noncurrent-carrying conductive material enclosing electrical conductors or equipment, or part of equipment must be
connected to earth"

Further, everything I have read indicates this is best practice.

However; there are those that state that the third prong on the electrical plug provides this and is sufficiant.

Please advise why the third prong is not sufficiant, or if it is, why I am incorrect in this matter.

Thank you

 

[bob]

In a data center containing equipment racks with servers, etc, it has always been my position to ground the rack, and bond the
cases of all equipment to the rack using a suitable bonding wire.

This complies with NEC 645.15

"All exposed noncurrent-carrying metallic parts of an information technology system has to be grounded as noted in Article 250"

and NEC 250.4 (2)

"Any noncurrent-carrying conductive material enclosing electrical conductors or equipment, or part of equipment must be
connected to earth"

Further, everything I have read indicates this is best practice.

However; there are those that state that the third prong on the electrical plug provides this and is sufficiant.

Please advise why the third prong is not sufficiant, or if it is, why I am incorrect in this matter.

Thank you

The third prong is connected to the equipment grounding conductor and it
does ground the electrical enclosure assuming that it is connected to said enclosure. I do not see how the rack would be grounded unless you do as you said and bond the rack and enclosure. If the rack and enclosure are in some way bolted together, that would seem to me to make the bonding connection.

 

[tallgirl]

The third prong is connected to the equipment grounding conductor and it
does ground the electrical enclosure assuming that it is connected to said enclosure. I do not see how the rack would be grounded unless you do as you said and bond the rack and enclosure. If the rack and enclosure are in some way bolted together, that would seem to me to make the bonding connection.

The entire rack should be electrically connected to the EGC by default, and everything installed and mechanically connect to it (as opposed to electrically ...) should be as well.

If there is some kind of power controller in the rack, its case is grounded and when it's mechanically connected (installed within ...) to the rack proper, that should ground the rack. If there isn't a power controller (meaning, some cheapo racks have something that is nothing more than a glorified power strip with push button circuit breakers), that contraption should do the grounding for the entire rack. There might be an additional jumper of some sort, but I can't say as I've seen one in 17 years of messing with rack mounted gear.