Racks and grounding 2

[Jtodd]

I have a couple questions regarding racks and bonding and Zone 4 seismic.

First of all, standard aluminum data racks, are they rated for seismic Zone 4, or do they need to be steel for Zone 4?

Second, aluminum rack that are painted, does any modification done to make a good bond? Also, the difference between powder coat or paint vs. anodizing. Does the anodizing keep the conductive properties of the alluminum?

Thanks for any help.
Let me know if more info is needed.


Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[franklin97355]

Bonding requires bare metal. anything that will bite through the coating to bare metal should do OK. Don't know much about Zone 4 but all our racks are supported from above to the wall.

 

[Servamatic]

Justin
As far as siesmic rating, I know Datatel specifically notes in their literature which ones are rated, I have not had a need to really investigate that...YET...

As for bonding, anytime you have a painted surface you should scrape down to metal under the point of contact, another way is to use the star washers, this is typically what we do, since many manufacturers include them with their patch panels. I follow the same guidelines regardless of type of coating.

Richard S. Anderson, RCDD

http://www.servamatic.net

 

[Jtodd]

Well, what I've run into is a lot of manufactures have info on Zone 4 CABINETS, no one seems to have anything on racks. Driving me crazy.
Anyway, thanks for the tips. I'm guess our consultant is going to come back that star washers aren't going to cut it for the bonding, and that expecting the contractor to scrape the paint is unrealistic, but I don't want the Yellow Zinc Dichormate (or what ever it is) racks. Ugly!
Oh well. I'll just argue with him over it.

Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[Servamatic]

What is it exactly that you are bonding? What to what?
Star washers are quite adequate for UTP patch panels, for screened or shielded a cable is required to the TGB.
A wire brush works wonders in a cordless drill for removing paint for bonding.
Generally racks are bolted to the floor, cabinets would not be, so they would be much more prone to falling over in an earthquake. I would imagine that is why you don't see the info on racks.

Richard S. Anderson, RCDD

http://www.servamatic.net

 

[daronwilson]

We usually bond to painted aluminum racks by sanding down a spot to bare aluminum and using a grounding lug. I have a drum sander that goes in the drill and I just grind a small bare spot for the grounding lug.

The rack gets bonded to the cable tray overhead and it gets a bonding jumper at each junction. Again we grind the paint down before attaching the grounding lug.

I'm curious to hear more on the siesmic ratings too, I've never been quite sure what needs to be done. We did a bunch of banks and they shipped siesmic bracing parts which consisted of a 5/8 or 3/4" all thread rod with angle brackets. We essentially bolted the brackets to the top of the rack and then ran the all thread to the ceiling and put brackets there. Seemed to make the customer happy.

When we do enclosed racks for equipment like cellular sites, we are required to run stainless steel cables through eye bolts on the top of the racks up to the ceiling.

Good Luck!

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[franklin97355]

Try this

http://www.gocsc.com/start/whitepapers/Seismic_Rated.pdf

 

[Jtodd]

Thanks franklin for the link, but I had already found that one, and its for cabinets anyway.

As for Servamatics question of what I'm looking for, I'm looking for solid justification to give to our consultant that black racks (paints, powder coated, anodized, whatever) can be bonded without much effort and tell him to forget the Yellow Zinc Dichromate racks.

Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[Servamatic]

Justin

On the Seismic issue...

http://middleatlantic.com/wp/wpseis.htm

I will do some more research for solid justification instead of just my $.02. I have never actually found anything from a manufacturer, so now I am curious.

Richard S. Anderson, RCDD

http://www.servamatic.net

 

[Servamatic]

Justin

Here isa what I have found so far:

http://www.enersysreservepower.com/documents/58_15_standard_rack.pdf

Also in the NEBS (Network Equipment Building Systems) requirements for Telco installation, namely a Verizon Document, 2 hole lugs are to be used for all grounding bonding connections and star (or Tooth type) washers are to be used.

http://www22.verizon.com/wholesale/attachments/NEBS_CL.doc

As far as I can tell none of them state any special metal requirements or scraping any finish, just star washers between all surfaces and 2 hole lugs.

Hope this helps.

Richard S. Anderson, RCDD

http://www.servamatic.net

 

[mcall]

just jumping in but should racks be connected to common ground by independent wire? Or is sufficient ground provided by rack mounted equip through power connection to isolated outlet?

 

[franklin97355]

Anixter has a good short excerpt from EIA/TIA607 on grounding. You use a wire from the main electrical ground and building metal structure to the frame.

 

[Servamatic]

An overly simple explanation of the 607-A Standard......

All metal parts in a Telecomm room should be properly bonded to a Telecomm grounding bus bar. Each rack should have its own bonding conductor to the bus bar as well. The building metal should also be bonded to the bus bar.
The more connection points the more equalization within the building, the less chance of ground related issues.

Since it is conceivable to have a difference when relying strictly on the ground wire of the electrical circuit, due to length and resistance, you should not rely on that as your bonding source.


Richard S. Anderson, RCDD

http://www.servamatic.net

 

[mcall]

thanks, all. looks like I need to schedule work in my server farms.