I also have recieved shocks.I agree with the writer. I install electronic equipment for radio and telephone equipment. We also repair equipment and often find that equipment racks are not grounded. Our policy is that any racks that are not grounded they will be grounded when we leave. Most customers are happy with this but once in a while one will say " It has always worked. "

Bob

It shouldn't be that hard. Most racks, especially the roll arounds, have a power strip. Just bond the incoming ground to the frame of the rack - done.

I always do this.

Ungrounded racks are certainly not the rule in the world of pro audio. Most pro audio systems in North America utilize star-connected Isolated Ground systems that conform fully with NEC 250. In such a system, all audio equipment is isolated from RANDOM contact with conductive objects (building steel, condult, concrete, etc.) using suitably rated conduit fittings and mounting methods. Conventional (not IG) mains power outlets are installed inside those racks in back boxes (or wiremold) that is bonded to the rack(s). One or more green wires, suitably sized per NEC, run with the phase and neutral conductors and bond the rack (and those backboxes) to the panelboard that feeds it.

Alternatively, equipment inside the isolated racks may be powered by plugging into IG outlets outside the rack. Since the equipment is screwed down solidly to the rack, this also bonds the rack and the equipment safely. Both of these are good engineering practice from an EMC (hum and buzz) perspective, and conform to NEC.

Video systems are often installed in this manner too, with IG outlets for equipment that is outside of racks. This can get mechanically tricky when you're trying to isolate a big video projector from building steel and stil achieve a safe structural suspension, but it is electrically proper and avoids noise problems.

This methodology is described in the tutorial that I wrote for Sound Contractors a few years ago, and can be downloaded at no cost as a pdf from my website. Soon after I wrote it, you requested my permission to link to it, and I granted it.

http://audiosystemsgroup.com/SurgeXPowerGround.pdf

Regards,

Jim Brown Audio Systems Group, Inc. http://audiosystemsgroup.com

These comments are provided via my IT Technical folks. Quote "Grounding kits are available for Equipment racks. Example check out the Rittal racks as an example. They have not only internal grounding but additional grounding kits for there equipment cabinets. Having been involved in the installation of these racks. Properly installed racks will have grounding either by the binding to the floor, connecting to upper structures above the racks. Basically if the installation was done properly the rack will be grounded when installed. Do note that the grounding is also checked/or can be checked at the electrical connection to include correct polarity, variance in voltage, leakage and grounding (checked with a properly calibrated meter).

http://www.rittal-corp.com/literature/download.cfm?id=49&action=view

By the way Rittal racks meet the requirements for earthquake areas and will handle the needs for most IT departments at a extremely reasonable cost!" UNQUOTE

BROOK (BAMBAM) MORRIS Industrial Occupational Safety & Health Professional McAlester Army Ammunition Plant SJMMC-DMS, (918)420-6497 DSN: 956-6497 1 C Tree Road, Bldg. 5 McAlester, Oklahoma 74501-9002 brook.morris@us.army.mil Do not go where the path may lead, go instead where there is no path and leave a trail...Ralph Waldo Emerson

Mike is right. I also believe the intent of the NEC code (art.250) is to require any metal likley to be become energized to be grounded. These racks should always be bonded. In addition they are also in danger of being energized by a lightning strike.

With two different potientials that close you could easly have a flash over. I have seen this take out an entire communication rooms.

Jim Yancey-NCDOI Engineering,Code Consultant

In my early daze as a labor-helper, I was building a holding rack of 1x12 shelving above and to one side of a commerical fabric cutting table that had a powered fabric bolt feeder. This unit kept the fabric in perfect edge-toedge alinement for the 'cutters'. The person(s) that installed this unit used the metal legs and rim guide bar as the point of grounding. In those early days, Skil saws were ALL METAL bodied. It was plugged into the same point of power as the roller unit. At end of work day I started to get off the table top and the saw touched the guide rim bar- my left arm started to sting w/ amperage, but since I was leaning over to get off the table, the shock pulled me forward and out of harm. It took about a week for the twitching to stop in my left arm.

Grounding and bonding or IT equipment racks & cabinets is required by 2 standards: - J-STD-607 Commercial Building Grounding (Earthing) and Bonding Requirements for Telecommunications (October 2002) - ANSI/TIA-942-2005 (Telecommunications Infrastructure Standard for Data Centers)

There should be a Telecommunications Grouding Busbar (TGB) in each Telecommunications Room and all racks and cabinets should be grounded and bonded to this TGB.

Good web resources are: www.panduit.com and www.erico.com.

IEEE Std 1100-1999, IEEE Recommended Practice for Powering and Grounding Electronic Equipment, has covered this area in significant detail. Cabinet grounding to the signal reference grid below the raised floor should be included in the contract documents for data center installation. Often this is omited by IT equipment iinstallers.

I worked as an electrician for over 16 years before getting my electrical engineering degree and becoming a licensed engineer. My electrician observations are from my own experience as an electrician and from verifying construction compliance with my engienering designs.

Grounding is not something all electricians understand from an overall perspective. Young journeymen electricains may not know enough to understand ground/bond concepts. NEC 250 is not always clear on the "how" to install grounding and bonding conductors. Some engineers take the "isloated ground" concept literelly and do not connect it to the same point as the equipment ground conductor.

Computer rooms and rooms containing computer equipment racks should be bonded as good as hospital patient rooms where the panel ground bars of all panels serving these rooms are required to be bonded together. A computer room is the "nerve" center of a company's operation and is vital to their existence. Each room containing computer racks should have a wall mounted ground bar connected to all metal objects in the room, the ground bars of all panels serving equipment in the room, and to the building service grounding point. It is my opion the all exposed metal objects and panel ground bars be at the same potential. In my designs, I require a rack line-up to have a bond wire from the wall mounted ground bar to each end rack and jumpers between all racks in the line-up.

Think about what happens when a 120 volt phase conductor comes into contact with an unbonded metal rack. Equipment on the same rack connected to another 120 volt phase conductor from the same panel has a difference of potential of 208 volts between phase conductor and the metal frame. A technician working on this equipment could get a jolt of 208 volts instead of 120 volts. Or, two racks side-by-side could be "hot" from two different phases and have 208 volts difference between them. this could be even more dangerous.

I have seen installations designed by engineers that did not comply with NEC 250.146(D). The isolated ground conductor riser in the building was not intentially connected to the equipment ground riser and was connected to a separate ground point outside the building. I guess they did not realize the shields in data cables would be the unintentional connection path. Thanks for this opportunity to offer my opinions on a serious safety issue.