R&M Data Center Handbook

www.datacenter.rdm.com
Tray
The advantage of a cable tray is that cables are better protected mechanically. According to the results of a test
carried out by the laboratories of Labor, AEMC Mesure and CETIM, a tray does not essentially provide better
electromagnetic protection than a mesh cable tray. Both produce the same “Faraday cage” effect (source:
www.cablofil.at). A key disadvantage of trays that must be mentioned is that only trays should be used which
prevent cable damage at the cable entry and exit points using appropriate edge protection In the case where an
exit point is added later, it is very difficult to implement the edge protection and thus the cable could be damaged.
Providing an additional cover reduces the danger that “external cables”, such as power cables for postconstruction
cabling, may be laid on data cables and impair their operation.
Mesh Cable Tray
A mesh cable tray does not provide the same mechanical protection as the regular cable tray described above.
The cable support points on grid bars may mechanically damage cables at the bottom of the tray, in the case of
higher cable densities. This risk can be definitively reduced if a metal plate, which prevents cable point pressure,
is placed on the base of the mesh cable tray. The advantage of the “open” mesh cable tray lies in its improved
ability for cables to be routed out. The option of using an additional cover is an exceptional case when using mesh
cable trays, but is a possibility with certain manufacturers.
Laying Patch Cords
If appropriate solutions exist for laying installation cables, the question remains: where should patch cords be put,
if not in the raised floor
This concept, and in turn the solution for the problem, is again made clear by comparing the distribution elements
found in EN 50173-1 and EN 50173-3: In principle, the Area Distributor (HC: horizontal cross connect) assumes
the function of the Floor Distributor, and the Device Connection (EO: Equipment Outlet, in the Distribution Switchboard)
assumes the function of the telecommunication outlet (accordingly in one room). This telecommunication
outlet is located in a cabinet that is comparable in principle to an office room. No one would think of essentially
supplying another room by means of a long patch cord from an outlet in an office. Similarly, in in the data center
only one element (e.g. a server) should be supplied from a device connection in the same cabinet. If this principle
is followed, there will be no, or at least significantly less, patch cords routed from one cabinet to another, sparing
the raised floor. Of course, patch patching from one cabinet to another cannot be excluded completely. Nevertheless,
this should be implemented outside of the raised floor. Three technical variants for this are worth
mentioning:
• Implementing trays or mesh cable trays above cabinets. The advantages and disadvantages of both
systems were already described above.
• The clearly more elegant alternative to metal trays or mesh cable
trays are special cable routing tray systems, such as the
Raceway System from R&M. This system, with a distinctive
yellow color, is likewise is mounted on top of the cabinet. It
provides a wide variety of shaped pieces (e.g. T pieces, crosses,
exit/entry pieces, etc.) which fit together in such a way as to
ensure that cable bending radius are maintained, an important
factor for fiber optic cables.
• If no option is available for installing additional cable routing
systems above the row of cabinets, or more space in the cabinet
is needed for active components, the “underground” variant is
one possible solution. In this case patch panels are mounted in
the raised floor in a box, e.g. the Raised Floor Solution from R&M,
where up to 288 connections can be realized. A floor box is
placed in front of each cabinet and the patch cords are then
routed directly from it into the appropriate cabinet to the active
components.
The same savings in rack space can achieved with R&M’s Robust Cabinet (CMS), where patch panels
are installed vertically and at the sides. Here as well, patch cords remain within one rack.
These solutions were already shown in a cabling architecture context, in section 3.4.5 “Other Variants”.
Clear cable patching makes IMAC (Installation, Moves, Adds, Changes) work in the data center significantly
easier.
Page 74 of 156 © 08/2011 Reichle & De-Massari AG R&M Data Center Handbook V2.0