Grounding in Data Centers
Grounding in Data Centers
(OP)
I am looking for people's experience with data centers, in regards to the grounding of rack enclosure cabinets. I have a customer you has lost several power supplies. The utility service ground is fine (less than 1 ohm), as is the panelboard grounds for the circuits feeding the racks sitting on the raised floor. There is an under-floor ground grid, but none of the enclosure cabinets in the data center have their frames grounded. They appear to be relying solely on the plug ground of the 120V cord power strips. Any thoughts on what is typically done with rack enclosures and grounding?? Any obscure code or IEEE requirements anyone is aware of??






RE: Grounding in Data Centers
Have the power supply failures been related to any other events such as thunderstorms, transfers to generator, etc?
You might take a look at the IEEE Emerald Book.
RE: Grounding in Data Centers
Regarding rack earthing, over here in the UK the Regulations are the minimum required for safety, not the design requirement for reliability and longevity of equipment. I'd expect to see the cabinet frame earth bonded down to the main earth grid.
Slight aside: when we have traditionally installed racks we have connected them to one or more BS4343 sockets installed under the computer room floor. We consider the rack as a piece of 'portable' equipment by virtue of being connected to a socket and size protection to meet the 0.4s fault clearance time required by the UK regs. Fixed equipment has a 5.0s fault clearance time although obviously we don't design right up to these limits. I'm curious whether others treat banks of racks as being 'fixed' or 'portable' equipment and whether you hardwire them or use a plug & socket?
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RE: Grounding in Data Centers
Good point about temperature. My experience has been that there is a wide range in quality of power supplies. They are probably the most common failure item in server equipment.
In the U.S. we almost always connect racks with cords and plugs. Overcurrent protection requirements in the U.S. are the same either way.
RE: Grounding in Data Centers
I would certainly look for a heat source or other cause for the power supply failures, it seems a stretch to think that an ungrounded rack would directly contribute to a power supplies' failure. If the power supply is properly mounted and connected there would not be much of a connection between the racks and the power supply.
Is the room properly air conditioned? Is the air supplied from the raised floor? Is there a supply air opening below the racks?
Does your system utilize UPS equipment?
RE: Grounding in Data Centers
http://www.erico.com/products/SRG.asp
RE: Grounding in Data Centers
RE: Grounding in Data Centers
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Sometimes I only open my mouth to swap feet...
RE: Grounding in Data Centers
RE: Grounding in Data Centers
2. See also IEEE sTANDARD 1100.
RE: Grounding in Data Centers
RE: Grounding in Data Centers
RE: Grounding in Data Centers
Next in line (probable causes) would be the quality of the power supplies themselves. They could be just dirt cheap items. The look for look for votlage transients.
RE: Grounding in Data Centers
One of the probable causes: Check the voltage rating on the power supplies vs actual voltage. Are they really rated for your voltage? Specially the server/computers are not made in the country they are used in.
For example, make sure they are not rated for 110V and your actual voltage is 120 nominal but is 125V actual?
RE: Grounding in Data Centers
The PC in my office, and the 2 I have at home, all suffer the extreme indignity of being forced to chug away day and night without benefit of any signal reference grounding system. Perhaps my data thruput suffers as a result. But the power supplies hold in there just fine, despite being some of the cheapest PC equipment available anywhere.
RE: Grounding in Data Centers
TIA 942 is a great first-pass attempt to bring some standardization to the data center design process, and to provide a good starting-point reference and list of typical considerations. It's a great overview for architects and engineers who have never designed a data center before, and for the data guys. But it is only that, and should not be misinterpreted as anything nearly so stringent as a true code or building standard.
RE: Grounding in Data Centers
Did you do any investigations on Power supplies?
Any surge suppressors on the 120/208V?
Any UPS power supplies?
Our client had this happening 2 years ago.
10 PS in less than 1 month.
Power Quality survey did not find anything.
Investigation of some brand name PS revealed design flaw in some PS on component level.
Good luck please post results.
Actually I am surprised that this type of problem does not happen more often. Maybe IT people just live with it.