The height is usually determined by the required height units in the rack, i.e. the hardware that is to be installed in the rack. Future plans must also be taken into account, as well as any height units occupied by accessories or free height units that certain hardware requires for heat dissipation.
The required width of the rack results from the 19″ (48.26 cm) installation width between the mounting rails (standard width for servers, switches, …) and the additional space required on the sides. Here, for example, cabling, air-conditioning units or accessories must be taken into account.
The smallest rack width is 600 mm, which consists of 19″ mounting width, frame and side panels. If PDUs and or cabling are to be mounted on the side, an 800 mm wide rack is usually required.
The maximum installation depth results from the cabinet depth minus approx. 15 cm (free space in front of and behind the 19″ mounting rails). That means, a 1000 mm deep rack has a maximum installation depth of 85cm.
If more space is needed in front of or behind the mounting rails (e.g. for cabling, power strips), this must be taken into account accordingly, as well as the installation depth for future planned hardware and ultimately also enough space for the supply of the cold or removal of the warm air flow. Due to ever deeper hardware, the standard rack depth is now 1200 mm.
An issue in two senses: both the rack must be designed for the total weight of the installed hardware (rarely an issue these days, except for very heavy hardware, such as a UPS or UPS battery packs) and the subfloor/floor/rack must be designed for the total weight of the equipped rack(s).
For the required space, the rack dimensions with open doors must be taken into account. A rack with a depth of 1200 mm and a width of 800 mm therefore requires a total of 2.80 m in depth. Split doors at the front and rear allow the space requirement to be reduced – in this example to 2 m required depth.
The accessibility of the space to bring in the racks must be considered in the selection, possibly only a demountable rack is suitable because the paths are too narrow/low/angled to transport a complete rack.
Suitable measures must be taken to ensure that the cold and warm air flows take the desired path in the rack and to prevent turbulence of the cold and warm air: Blind plates cover free height units, brush seals prevent unwanted air leakage, e.g. at cable outlets, a frame around the 19″ rack takes over the function of blind plates at the side or top and bottom.
Depending on the requirements and, if applicable, the existing air-conditioning solution, airflow management is also an issue outside the rack: from enclosure to airflow guides in the raised floor.
Various systems are available to monitor the rack against physical hazards, depending on the requirements. At least basic protection against the main hazards of temperature, dew point, fire, burglary makes sense. Temperature sensors are best placed at the rear of the rack by the blowing fans. If the value here is correct, it is also okay on the blowing-in side. At least 3 temperature sensors per rack are recommended.
Another rack issue is proper power distribution planning and equipment. The PDU must have enough ports, with/for the appropriate connectors and enough capacity. Additional functions such as measurability and switchability of individual connections or the entire PDU may be required, and the range of power distribution strips is correspondingly wide.
Acoustic cabinets provide significant noise reduction with an acoustic foam lining, and fans that are usually less than 30 dB(A) quiet. Especially recommended if the rack should/must be placed in an office environment or similar. Complete soundproofing is not possible. The noise of the external rack fans and the internal hardware (or their fans) cannot be completely eliminated, but only dampened. Another source of noise to consider when selecting a rack location may be air conditioning.
To prevent overheating of the hardware installed in the rack, it is important that sufficient cooling is provided. Powerful hardware in the rack also generates corresponding waste heat. Thus, the topic of air conditioning is one in which special consideration must be given to future plans to expand the hardware, since retrofitting is often difficult or requires a great deal of financial effort. For dimensioning, it is therefore important to know which current load and thus heat load is or is to be installed in the rack. From approx. 1 kW in the rack, the necessity of air conditioning should at least be checked in the planning.