Bonding Telecom Racks

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JdoubleU

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If a room telecom room is being put together what is ok for bonding the Rack? Can you go to the nearest panel?
 
Not sure if I am reading this right but can you bond the rack to the 120v receptical equipment ground.
 
I don't think the code tells us. Equipment Rack is used in a few places in the code, and it generally says equipment racks must be grounded. How and what size are not mentioned. I've never understood why a rack with no power connections would need to be grounded. A rack with power connections will most likely have an item bolted to the rack rails which generally will cause the rack to get bonded (I've even got some special rack grounding screws with thread forming threads and teeth under the head to bond painted equipment). With some of the power coating being done, I'm not so sure there is good electrical contact between various structures of a rack. So where to bond to be effective and where are possible hazards?

Most listed racks will have a grounding screw or thread hole. I'd connect that to a ground stud on a PDU if the rack has one. If there is no power cord going to the rack (or it is an ungrounded system), I would think taking a ground from a panel or branch circuit would be acceptable.
 
suemarkp said:
I've never understood why a rack with no power connections would need to be grounded.
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Usually, it's not that the rack needs a connection to the GES for fault protection (the EGC takes care of that), but that it need to be bonded to it's fellow racks for signal integrity. That's a big concern in analog audio/video setups and others where signals use a ground reference.
 
copper chopper said:
we typicaly run a bare #6 around the rack and any cable tray, bonding it to everything and then back to the panel serving that room.
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In large Tele comm rooms I've seen, they (sometimes) have both normal and emergency receptacles, Also in most cases I've seen there is a vertical ground running through each floor which the structure is attached to via the interconnected ground bar.
 
zbang said:
Usually, it's not that the rack needs a connection to the GES for fault protection (the EGC takes care of that), but that it need to be bonded to it's fellow racks for signal integrity. That's a big concern in analog audio/video setups and others where signals use a ground reference.
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But that is making a lot of assumptions about what is in the rack. If you've got balanced signals, it shouldn't matter. If you have unblanaced ones, I'm not so sure rack grounding is going to help much with all the parallel shields also connecting things. We've taken different approaches to dealing with unbalanced video signals, from isolating each feed through or rack device, to just not worrying about it. If the distance is long, it is best to change to fiber or a balanced converter and eliminate the problem.

Seems like a design decision and not a safety one (e.g. an ethernet patch rack with nothing but punchdown blocks or plastic feedthrus -- why should that rack be bonded)?
 
Speedskater said:
This paper from who else? a rack company! Has several pages on rack power and grounding.

http://www.middleatlantic.com/pdf/PowerPaper.pdf
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Kevin, that paper starts in the first couple pages by stating that it is not for data, but for A/V.

I am very interested in understanding the need for bonding cable trays and racks containing data only, I'm in the middle of such a job right now.
 
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