IT Racks

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jazer

Senior Member
Location
Gibsonia, Pa
I have three individual IT server racks, on wheels not bolted down, that are not grounded to the GES. Within this small IT room is a distribution panel and x-former. The xf is grounded properly, including building steel, as well as the panelboards. My question is: Can the IT racks be grounded by simply running a #6 copper to any ground bus within these panelboards, or do I have to hit the bldg steel as well, or may I just use the bldg steel, or am I missing something? 645.15 talks about grounding this equipment, built in UPS aside, but I cannot find the minimum requirements without interpretation. Need a solid reference. Thanks in advance.
Jazer
 

tryinghard

Senior Member
Location
California
The tech's usually want zero potentiial with the equipment grounding because they terminate their drains/shields on it. You can get zero potential with a #12 +/- as long as it originates the same place as the power. I don't see what earth ground can do for safety with IT racks.
 

jumper

Senior Member
I found this here:

Q. What are the requirements for grounding metal equipment racks supporting computer servers?

A. The Code requires 'bonding' not 'grounding' as follows: All exposed metal parts of an information technology system must be bonded to the equipment grounding conductor [645.15]. This 'bonding' requirement is accomplished when the metal equipment rack is secured and in direct electrical contact with the metal case of the servers, which are connected to an equipment grounding conductor as per 250.134 [250.136(A)].

Are you on 2005? 645.15 is a little different in 2008.

645.15 Grounding. All exposed non?current-carrying
metal parts of an information technology system shall be
bonded to the equipment grounding conductor in accordance
with Article 250 or shall be double insulated.
 

jazer

Senior Member
Location
Gibsonia, Pa
I pulled from the 2005. So it seems that IT racks are properly bonded thru the servers, equipment and such that are bolted into them; thru the cord and plug ground? Am I interpreting this correctly?
 

iwire

Moderator
Staff member
Location
Massachusetts
I am not an IT guy but I see it the same way.

This is the same as the bonding requirements for gas lines, the EGC supplying the equipment likely to energize it can serve as the bonding means.
 

jumper

Senior Member
That is how I interpret it. Let's see if one of the IT guys chime in.

I am not an IT guy but I see it the same way.

This is the same as the bonding requirements for gas lines, the EGC supplying the equipment likely to energize it can serve as the bonding means.

Well, I"ll be darned, Bob! That is three times in two years that you have agreed with me. You getting soft or am I getting better?:)
 

ceb58

Senior Member
Location
Raeford, NC
Ground (earth) bus conductors interconnect the MGB, SSGB, RGB and the equipment grounding
conductor with the cabinets, racks or individual system or subsystem components. The end of the
conductor opposite the MGB or SSGB typically remains unterminated, although this end of the
conductor may be terminated to a cabinet, rack, individual system component or RGB.
Ground bus conductors typically originate at the MGB and radiate throughout the equipment area
generally within the cable tray system. These conductors may extend into an adjoining subsystem
equipment area and may serve as the grounding conductor for a SSGB, or RGB. Ground bus conductors
shall be bonded to the MGB, SSGB, or RGB using methods described within this chapter.
Ground bus conductors may have ground bus extension conductors to provide a ground bus within cross
section segments of a cable tray system. These ground bus extension conductors shall be of the same
specification as the ground bus conductor and shall be routed with all connections to the ground bus
conductor pointed in the direction of the MGB or SSGB. The ground bus extension conductor shall be
bonded to the ground bus conductor using suitable methods described within this chapter.
Equipment grounding conductors from each cabinet, rack or individual system component chassis shall
be bonded to the ground bus conductor or ground bus extension conductor using methods described
within this chapter. See Figure 5-17. Ground bus conductors are not required to be installed at all
locations, provided that equipment grounding conductors from each cabinet, rack and individual system
component extend to the MGB or SSGB

This is an excerpt from Motorola's R-56 standard for grounding in communication buildings.
In our buildings each rack has a separate #6 tied to a #2 grounding conductor that is taken to the MGB.
Your best bet is to install a MGB that is tied to the electrical system grounding conductor (single point grounding system) then you have a point to ground all the metal frames of equipment to.
 
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jazer

Senior Member
Location
Gibsonia, Pa
well, the last sentence of this excerpt basically states as long as the egc is present, a seperate ground conductor isnt necessary.
 

ceb58

Senior Member
Location
Raeford, NC
well, the last sentence of this excerpt basically states as long as the egc is present, a seperate ground conductor isnt necessary.

That is true it is not requried. But we still install the grounding system because it is for communication equipment and we have 400 - 1200ft steel towers out side that just love lightning. Along with the NEC we must meet the requirement of R-56 due to warranty issues with all of the Motorola equipment.
Its kinda a joke that if you stand still long enough in the building someone will run a ground wire to you and try and bolt it on.:roll:
 

dbuckley

Senior Member
I'm an IT guy; I dont need require my racks to be specifically bonded because as soon as I screw something (or several somethings) into the rack there is continuity to ground. Almost always there is a power distribution rail of some sort screwed to the rack, and that'll bond the rack too.

Mostly stuff is connected to these servers using Cat5 ethernet, which is transformer isolated at both ends, or fibre (networking or fibre channel disks / SANs), so frankly the whole issue of relative ground potential with server racks is so last century. It used to matter enormously in the days of coax 10Base2 "cheapernet", and ubiquitous RS232; its now just a footnote in the history of IT.
 

jazer

Senior Member
Location
Gibsonia, Pa
That is true it is not requried. But we still install the grounding system because it is for communication equipment and we have 400 - 1200ft steel towers out side that just love lightning. Along with the NEC we must meet the requirement of R-56 due to warranty issues with all of the Motorola equipment.
Its kinda a joke that if you stand still long enough in the building someone will run a ground wire to you and try and bolt it on.:roll:

That's hilarious, may I use that? Thanks for the info, I appreciate it.
 
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