For large rooms having similarly high heat loads we use units similar to those described in this section for Computer Rooms. However they do not usually require the humidification or filtration functions.

For smaller rooms we can provide the required amount of cooling and air distribution, by using smaller split system units. These work on exactly the same principles as described for the larger air handling units, but with coarser temperature control and less air velocity and volume.

They simple blow cooled air from their tops or bases and collect returned warm air through filtered grilles mounted in their fronts. They contain an evaporating or cooling coil, over which the returned air is passed. The heat is extracted and absorbed by the medium contained in the coil. Vanes in the discharge vary the path of the supply air and provide some direction control.

The principal of air distribution is to discharge cool air at high level over the equipment producing the heat. This cool air is dense and drops. It mixes with the heat rising from the room equipment. At mid level, we attempt to achieve comfort temperature levels.

The warm air is drawn back to the air handling equipment to be filtered cooled and recirculated. In the process of being cooled, the return air loses moisture – condensate.

Heat removed from the room by the air handling unit cooling coil is carried by pipework to externally mounted heat exchangers. Depending on the cooling medium used, these are referred to as condensing units, condensers, chillers or water towers.

They pass the air handling unit air heated cooling medium through an arrangement of tubes, over which air or water is passed to collect the heat, before the medium is returned to the air handling units for the cycle to be repeated.

The closer the units are located to their associated air handlers, the lower the pipework installation cost. There are limits to height and distance for their location.

These units need access to fresh air or a mains water supply. There are alternative means of achieving this, both outside and inside the building – usually the former.

All emit sound, and so consideration has to be taken regarding local environmental impact. There are means of reducing the sound levels to residentially acceptable levels.

Planning permission from relevant bodies may also be required.

Whilst the air conditioning system’s prime job is to remove the heat produced by the room equipment, building fabric, lighting, fan and solar gains etc. it also requires a heating facility.

This is to prevent condensation forming in the event of the room equipment being shut down during cold external ambients.

Heating may be provided by the installation of separate thermostatically controlled heaters, or by heating elements in the air handling equipment. An alternative, in the case of direct expansion cooling systems, is a reverse cycle valve – heat pump.

The manufacturers of equipment commonly found inside Server/Telecoms rooms do not call for fine levels of air filtration.

It is therefore only necessary to provide coarse filtration within the return air path in the air handling equipment and the fresh air source.

However, the fresh air intake needs to be checked to ensure fine particulate pollution is unlikely from engine exhausts and the like.

A Server/Telecoms room does not usually need control of humidity levels. However in large installations it may be considered prudent to install humidification to reduce static build-up. In this case, stand-alone units are available which produce water vapour by either boiling a body of water with a heater element or its surface by means of an electrode.

The Server/Telecoms room has a more comfortable environment for human occupation than a computer room, because the temperature is higher and the noise and air movement are less. However sound levels and noise are still much higher than in a normal office environment.

It is possible therefore to allow operators to spend longer periods working inside the room. Where this is likely we have to provide a source of fresh air.
The source needs to be fresh by definition and forced. It is best introduced via the room air handling equipment in order to be quickly dispersed.

Its volume needs to be taken into account when calculating the room heat load – for the air conditioning design.