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Temporary Air Conditioning Hire Information

Choice of Equipment

This page provides some information on temporary air conditioning equipment for hire in offices, server rooms and for events. There are good reasons why the right equipment for the right application is important. for example, for you office you may need units powerful enough to cool your office but which are quiet enough to work beside all day whereas for your server room a unit which will run continuously, without attention, with a fan powerful enough to circulate air behind the racks, may be the priority. For these applications evaporative coolers are definitely not recomended, though they appear more convenient to use.

To help you to understand why certain types of equipment are or are not suitable for particular applications, we have provided some useful information, below.

You can, of course, phone us, here in London SE1, for advice. Tel 0207 582 8950 - we look forward to speaking to you.

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For those portable air conditioning problem applications we have devised our own solutions over the years and we will be pleased to talk through your application. You can email us with your details and we will respond promptly - contact Air conditioning hire (London) Ltd.

Temporary Air Conditioning - some background information

How air conditioners work

All air conditioning works in a similar way. A refrigerant is circulated around a system which condenses and evaporates the refrigerant. A compressor is used to compress the gas. This compression creates gas at high pressure and high temperature. It passes through the condenser coil to cool it down and that cooling process condenses the gas into a liquid state. The condenser coil therefore gives off heat and a fan is used to drive air through the coil and make the process more effective. This heat is discharged to outside. After passing through the condenser coil the refrigerant is in the form of a cool liquid at high pressure. This liquid refrigerant is discharged into the evaporator coil (the indoor unit in the case of a split system) and the heat required for that process of evaporation is drawn from the air passing over the coil, so cooling that air. Again a fan is utilised to force air over the coil and increase the effectiveness of the process.

Differences Between Temporary Air Conditioning and Installed Systems

In a fully air conditioned environment not only is the temperature controlled but also the humidity and the proportion of fresh air which is introduced. In some systems the air is also filtered to remove pollen, dust and other pollutants. Such systems are usually an integral part of the building infrastructure and controlled by a computerised building management system. This level of control is not possible with temporary or portable air conditioning.

Portable air conditioners normally provide 'comfort cooling' which involves some degree of humidity reduction. Humidity reduction takes place as the air passes over the cold evaporator coil and water is condensed out. This is collected in a tank within the unit which needs to be emptied periodically, or discharged automatically, depending on the design. Some units also have filters to remove some pollutants.

Monobloc and Split Type Portable A/C Units

Monobloc units are a complete system in one casing which exhausts hot air through a pipe to the outside and passes the room air over a cold coil and back into the room. These units constantly exhaust air to the outside which causes some replacement fresh air to come into the building.

Temporary split air conditioners have two parts. The condenser is placed outside and this is connected to the evaporator which is placed inside the room by flexible refrigerant pipework. As the unit does not discharge air to the outside, the room air is retained and recirculated across the evaporator coil so cooling the room air. For this reason split units are capable of reducing the room temperature further than monobloc units. When comparing monobloc units and split units, in most situations the split unit of the same rating (KW of cooling) will be more effective in bringing down the room temperature, particularly in very hot weather.

Noise levels for Temporary Air Conditioners

In office and domestic environments noise levels will almost always be important. The noise level of any unit will depend on a number of factors: type of compressor, fan design and speed, sound insulation installed inside the machine and the type of unit.

Monobloc units normally contain two fans, one to circulate air through the evaporator coil and discharge the cold air into the room and the other to push air through the condenser coil and down the exhaust tube to outside. The condenser fan is usually the larger and noisier of the two but the evaporator fan noise is more noticeable as it discharges air directly into the room.

In a split unit the condenser fan is outside so the indoor unit is quieter than a similar duty monobloc unit.

Sound levels of portable equipment are quoted in dB(A) measured at 1 mt from the equipment and are normally in the range of 46-56 dB(A) for office equipment and as high as 66 dB(A) for larger industrial units. The quoted sound levels should be treated with some care as the location, surrounding materials and background noise are significant factors in determining what is an acceptable noise level. The frequency and nature of the noise can also be factors in our tolerance of noise. Noise levels are often quoted at minimum fan speeds at which the full cooling output is not available.

Many of the portable air conditioner designs are manufactured in China to Chinese specifications and these tend to have high evaporator fan speeds to enhance the impression of cooling. For UK office applications this can mean noisier operation and unacceptable draughts.

Evaporative Coolers

As the name suggests these units provide a stream of cool air by evaporating water into the airstream. The process of evaporation requires heat to be taken out of the air so in this way the air is cooled. This is quite different to temporary air conditioning and does not utilise refrigerant. Evaporative cooling is suitable for very well ventilated areas, for example a room with open doors at each end. The cooled and moistened air will circulate through the room and out of the other door. This type of unit is not suitable for a closed room as the moist air will be trapped in the room and the moisture content of the air will quickly reach near 100% relative humidity, at which point not only does the evaporation/cooling stop working but the room becomes very humid and uncomfortable.


Dehumidifiers operate in a very similar way to monobloc air conditioners but they do not exhaust the hot air to the outside. They are designed to remove moisture from the air so that drying of the walls, carpets etc will be accelerated. The moisture is normally collected in an internal water tank which needs to be emptied regularly. We can provide a pump system to continuously discharge the water collected to a drain.