Tips for Efficient Air Conditioning

If you want to install the hardware of a smaller IT environment or a stand-alone IT cabinet, you should first think about the right cooling concept. Does the entire room really have to be air-conditioned or is it sufficient to cool the IT cabinet specifically? Because only with the right climate management can energy costs be optimised and reliability increased. Here HVAC provides useful tips on air-conditioning server cabinets.

Today, small and medium-sized enterprises as well as large corporations rely on high-performance IT systems to support their business processes. The difference, however, lies in the number of computers: while large companies need a complete data center, smaller companies need just an air-conditioned room or the targeted cooling of individual racks.

Determining the energy requirement

The first step in planning was to determine the energy requirement resulting from the occupancy of the IT cabinet. A glance at the data sheets of the IT components to be installed shows the level of electrical power consumption. These values add up to the total energy consumption. In smaller IT installations, IT cabinets are rarely occupied with active components in their full height over all 42 height units. Rittal’s experience has shown that a value of around 5 kW per IT cabinet is a common mean value for a smaller IT environment. By way of comparison, fully equipped high-end systems can consume up to 30 kW of electrical power per IT rack.

Clarifying the type of air conditioning

Depending on the application, it can be more cost-effective to cool individual racks than to air-condition a complete room. In particular, smaller companies with only a few IT cabinets will not be able to afford complex room air conditioning with chilled water systems. Air conditioning units mounted directly on the IT rack provide a remedy. These consist of an indoor unit with integrated speed-controlled compressor and an external condenser, which is installed outdoors.

An example of this is the LCP DX cooling solution from Rittal (Liquid Cooling Package Direct Expansion), which can be mounted on the side of the IT rack. The special feature here is that the LCP DX was specially developed for cooling small IT rooms and supplies the cold air directly to the IT equipment at the correct temperature. The heat is not transferred to the installation room, but to the environment at the location of the external condenser. Roof air conditioners mounted on the IT cabinet can also be used in particularly confined spaces. When the LCP DX is used, outputs of up to 12 kW per IT rack can be cooled. Alternatively, the unit can be mounted between two racks so that two IT cabinets can be cooled with just one air conditioner.

Observe external conditions

There are only a few criteria to consider when installing rack-based cooling. Of course, a power supply at the installation site of the outdoor unit is required. It must also be ensured that residents are not disturbed by the appearance or noise. In the case of older buildings, it is always forgotten to check whether they are listed.

Selecting the right coolant

In IT air-conditioning technology, it is generally possible to choose between water and refrigerant as the cooling medium, whereby R-410A is generally used as the refrigerant.

In smaller IT environments, the cost of water cooling is usually too high, as the entire infrastructure for the water supply must be installed here. The use of refrigerants is generally cheaper to implement, since, for example, breakthroughs for thinner copper lines can be produced more cheaply.

Pay attention to air supply and ventilation

If the use of split air-conditioning systems is not possible, cooling is often implemented with cooling units directly at the IT rack. However, the thermal energy absorbed by the rack is transferred directly to the IT room. When using this technology, good ventilation with fresh air must be ensured.

This can be done, for example, by drilling two core holes through the wall, similar to an extractor hood for the kitchen. One opening serves for the air supply, the other for the ventilation. The performance of the fans used there should harmonise with the cooling performance of the air conditioner.

Alternative for larger IT environments: Room air conditioning

If a company needs more IT and network technology than can be accommodated in an IT cabinet, room air conditioning is the right solution. The basic idea is to cool the entire technical room. This can include IT and network cabinets, telephone systems, printers or copiers. With this variant, when purchasing the IT rack, care must be taken to ensure that the front and rear sides of the housing are sufficiently perforated to ensure air circulation.

In practice, doors are offered with a perforation of around 80 percent, while suppliers such as Rittal achieve values of 85 percent with the TS IT Rack. The higher the air permeability, the more efficient the cooling of the IT systems. This principle achieves front-to-back airflow: cold air is supplied from the front and blown out again via the fans at the rear.

Separating cold and warm air

In order to achieve the most efficient cooling possible, care must be taken to ensure that cold and warm air do not mix. The Delta T on the air side should be as large as possible so that the air conditioners operate with the best possible efficiency. For this reason, the IT cabinet is partitioned and divided into a cold and a warm area. Some suppliers promise 100 percent complete partitioning of the cold/warm area.

In practice, the additional costs incurred are not profitable. Accessories supplied by rack manufacturers such as blind strips, magnetically coated sealing strips, air baffles and brush strips ensure adequate sealing.

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