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We are in the construction phase of building a data center. we are gfacing an issue with the grounding inside the computer room. thie issue is basically is whether to use spearate ground buses for power (PDUs, power panels) equipment and communication equipment? these buses are connected to one common ground grid.

Hi Fahad,

Thank you for your question regarding computer room grounding, it is our pleasure to help.

There are often many questions regarding the various grounding and bonding systems found within a computer data center, and this mostly has to do with the difference between the low-impedance ground fault path required by the National Electrical Code (NEC), and the grounding systems required by computer manufacturers.  Remember that the grounding systems required by the NEC are only to ensure that Over Current Protection Devices (OCPD) such as circuit breakers and fuses will function properly.  These systems require that a low-impedance ground fault path exists so as to enable a massive flow of current to temporarily pass through the OCPD, tripping the breaker and/or blowing the fuse.  This grounding system is not designed to eliminate transient currents, stray voltages, or to reduce differences in potential that could harm sensitive electronic equipment. 

It is usually helpful, to consider swimming pools as an example.  Swimming pools must have two (2) grounding systems.  One for the fuses and circuit breakers (the low impedance ground fault path), and another grounding system to provide an equipotential grounding plane, referred to as “equipotential bonding”.

When we ground a swimming pool, the rebar that is in the concrete making up the pool is of special importance to us.  If the rebar and other metal components (hand rails, etc.) are not bonded to form a common equipotential ground plane, serious voltage differentials can form that could injure occupants of the pool.  As such, the NEC requires an additional and separate grounding system bonding the rebar and other metal components together.  This system is separate from the green grounding wire that would also be required for the pool lights, and is used to ensure that the circuit breaker trips.  Here is a link with some more info:

http://www.esgroundingsolutions.com/blog/661/which-atricle-in-nec-references-swimming-pool-grounding

Now, as far as a computer data center goes, they have a similar requirement for a separate equipotential grounding plane.  You should refer to whichever standard you are building the data center to for more details, however most of them spell out in some detail how these systems are to be bonded.  Typically, grounding bars tied back to a dedicated grounding electrode systems (often 5-ohms or less) is specified, with bonding to such items as: computer racks, components within the racks, the metal components of the air conditioning systems, metal parts of the fire suppression systems, steel conduit used to route Cat 5 cables, cable tray supports, metal chassis of junction boxes, elevated floor components, metal ceiling components, etc.  You may want to refer to ANSI/TIA/EIA-J-STD-607-A and Motorola’s R56 standard for some guidance.  Remember, that these computer systems actually generate RF interference, and a good grounding system is necessary for proper data system functions.

So, to finally answer your question, the grounding system used to bond your electrical panels must be a different grounding system from what is used to ground your computer system requirements.  However, these two systems must be bonded together to form a common system at the main electrical panel.  How and where you make these bonding connections is very important so as to not inject dangerous electrical energy back into your computer systems.

Can we be completely honest here?  This is pretty basic stuff and you should already have blue prints detailing these requirements.  If you are already in the construction phase and don’t have a grounding system designed for a data center, someone has really done the end user a big disservice.  Copper is one of the most expensive materials you can buy, and it is not unusual for a computer data center to have millions of dollars in grounding alone.  Even the most basic of grounding systems for a computer data center will have major grounding requirements for both inside the structure, and out.  Let alone the lightning protection system requirements and the human safety requirements for the substations and backup generators.  It must be properly designed and modeled by engineers specializing in this very complex field.

Please give us a call at 310-318-7151 California time so that you can make arrangements to get an engineer out to your site as soon as possible.  It sounds like you need immediate on-site guidance to get this site up to code while it is still in the construction phase.  But if not us, please get someone with the experience and knowledge to provide you the guidance you need to get your data center built so that it is safe for the personnel working in it, and that it will protect the equipment and enable the site to function as it should.

Best regards,

The Engineering Team at E&S Grounding Solutions

 

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