Flooring — 17 September 2010

Tom Turner, product manager of grounding and bonding and power connectors at PANDUIT (www.panduit.com), says:

Many data centers have loose busbar connectors. One reason that they loosen has to do with how the grounding cable (conductor) attaches to the connector. There are two options. First, mechanical connectors have a set screw that the installer bolts onto the conductor to hold it in place. The other type, known as compression connectors, has a barrel that the conductor slides into. Once in the connector, the installer uses a special tool to permanently deform the barrel to the conductor. The advantage of mechanical connectors is that they can be installed with a simple screwdriver or Allen wrench. The disadvantage of mechanical connectors is that they tend to loosen over time, requiring periodic maintenance. While compression connectors require special installation tooling, they never loosen, and so are preferred for telecommunications grounding applications.

Most industry-recognized telecommunications grounding design standards require that two-hole compression lugs be used on busbars. However, in practice, many one-hole mechanical lugs are used. So, the recommendation is to always specify “two-hole compression connectors on all telecommunications grounding busbars.” If you already have one-hole or mechanical busbar lugs and you cannot replace them, plan to re-torque the busbar attachment bolts and the conductor set screws every six months to make sure the connections stay tight.

Besides loose connections, another common problem is missing grounding connections. Most data centers have some form of bonding grid beneath the access floor. The bonding grid is recognized as the bare copper electrical wires that run throughout the length of the floor. This grid needs to be periodically bonded to the access floor, the cable pathways, the grounding busbar, and to most of the other large metal items in the room. Sometimes, the jumper wires that are used to connect the conductive surfaces are either not installed or taken off during a data center renovation and not replaced. Problems can be eliminated by utilizing infrastructure components that automatically create electrical bonds when assembled without the need for bonding jumpers.

Panduit addresses the risks inherent in complicated grounding systems like those found in data centers by designing our pathways, racks, and cabinets to be electrically continuous without the need for bonding conductors to connect their structural elements. In parts of the grounding system where grounding conductors are still required, Panduit offers kits with features like pre-terminated two-hole compression lugs. Use of these kits helps ensure that best-in-class installation practices are used so that your risk and maintenance requirements are significantly reduced.

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