S 1.67 Dimensioning and use of cabinet systems

Initiation responsibility: Head of IT

Implementation responsibility: Head of IT

To improve the operational safety of servers and of active and passive network components, these devices should be installed or mounted in cabinet systems. Cabinet systems are often referred to as 19-inch racks, server cabinets, or even network cabinets, depending on the type of application.

System cabinets are standardised according to DIN IEC 60297 and DIN 41494 "Mechanical structures for electronic equipment". This allows installation of devices from any manufacturer as long as the device complies with these standards. Components complying with the standards mentioned above can frequently be recognized by the phrase "19-inch installation".

Cabinet systems are available with various inside and outside dimensions. The most widely used cabinets provide a net space for a total of 42 rack units (42 U). Depending on whether the cabinet systems are installed in closed distribution rooms or in rooms accessible to the general public, the cabinet systems must be equipped with doors, side panels, and closing devices appropriate for the corresponding protection requirement. Pedestals under the cabinets make it easier to insert the required cabling. Another advantage of using a pedestal is that there is extra space between the floor of the room and the IT systems. In this case, minor flooding will not automatically lead to damage of the IT systems since the devices are in a higher position. If the distribution rooms are secured correspondingly, the cabinets do not necessarily need doors and side panels upon checking the ambient conditions.

The internal design of the cabinet absolutely must take into account maintenance aspects. For example, it must be possible to swap modules quickly in a patched switching system without adversely affecting neighbouring systems. This requires the components to be installed accordingly to anticipate this as well as a corresponding patch cable management. It is therefore advantageous if the electrical cabling and the IT cabling can be routed stably and with protection. Many cabinet system manufacturers offer components that can be used to adapt the cable routing inside the cabinet to the specific wishes and requirements of the user. Excessively long patch cables must be avoided.

When planning the equipment to be installed in the cabinet, note that the capacity of the cabinet is usually limited by the amount of heat dissipated by the installed devices and not by the available installation dimensions. Problems with heat dissipation may arise when the thermal load of the devices installed is too high.

Similar problems may arise in network cabinets containing a large number of passive components (patch panels) when too many cables are installed.

In this case, the flow of air through the cabinet may become so disrupted that parts or active components malfunction. This aspect must also be taken into account when planning the devices to be installed in the cabinet.

If cabinets are set up next to each other, the air flow to the active components in neighbouring cabinets must also be taken into account. The warm air flowing out of a component absolutely must not be allowed to adversely affect the flow of cold air to neighbouring components. Sealing each of the cabinets in the row of cabinets may counteract this problem.

The cabinets must be equipped in such a way that the active components can be operated within the prescribed temperature ranges. In the simplest case, passive cooling of the cabinet will suffice when there is enough cool ambient air available in the room. Fan systems can be used in closed cabinets to support passive cooling of the cabinet. If the thermal load is to high, active cooling systems of various designs can be used. There are two types of active cooling: room cooling and cooling systems that can be attached to or on top of the cabinets.

To be able to operate compact IT components with very high heat dissipation, the use of special cabinet systems with independent climate control systems may be considered. Such cabinets, which usually use a liquid coolant internally, should only be used after performing a requirements and risk analysis.

All types of climate control require exact planning that takes into account all possible influencing parameters, including a corresponding examination of the cost-effectiveness. When using cabinets containing their own climate control units, it must also be noted that climate control devices mounted on side panels or doors can reduce the opening angle of cabinet doors and may project out into escape routes under some circumstances. Wherever possible, the room layout should be planned in such a way that climate control technology can be added to the cabinets if necessary.

It is recommended to create uniform specifications in the organisation for the equipment and use of cabinet systems. The cabling running between cabinets must also be planned carefully (see also S 1.69 Cabling in server rooms).

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