R&M Data Center Handbook

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3.10.7 Consolidating the Data Center and Floor Distributors
When planning a new floor distributor system as part of a cabling system redesigning, a new floor distributor is
usually placed in the data center or server room. This offers the advantage of using a quality infrastructure that
generally already exists, including a raised floor, cooling system, USP, etc.
However, modern EMC-based designs advise against this if copper is used as a tertiary medium. The reason is
that these modern EMC designs are based on a division of a building into different lightning protection zones. The
overvoltage caused by an indirect stroke of lightning will be greatest in the outer area of the building (lightning
protection zone 0) and will lead to an extremely high induction current.
To put it simply, metallic lines into a building from the outside will lead this high current into the building (lightning
protection zone 1). Therefore, in a conventional telephone cabling system surge protection was provided at the
entry of the building. However, there are other also zones in the building itself that would have a problem with the
remaining residual current behind the surge protection element. Electronic components could be destroyed by this
current. This resulted in the definition of other lightning protection zones, where the remaining current diminishes
after each surge protection element in subsequent zones.
Data center server units have a very high protection requirement. These units are “packed” in lightning protection
zone 2, so one must take care to minimize the lightning’s residual current within the data center. Designs in accordance
with standards make provisions that each metallic conductor that is routed into or out of the data center be
secured with a surge protection element.
If a floor distributor with a Twisted Pair concept is placed in a data center, each twisted pair line would therefore
have to be protected with a surge protection element of sufficient quality (suppliers for this include Phoenix and
other companies). This is very rarely put into practice in the data cabling system (in contrast to the power cabling
system!), yet the risk does exist.
Recommendation
When setting up a high-availability data center, disregarding this generally established lightning protection zone
concept (DIN EN 62305 / VDE 0185-305) would be negligent, and a floor distributor should therefore not be
placed in the data center if at all possible.
R&M Data Center Handbook V2.0 © 08/2011 Reichle & De-Massari AG Page 155 of 156