When the temperature rises, it reduces our performance and vital equipment can fail. To avoid these problems, Andrews offers a wide range of portable air conditioners. These include both air and water cooled versions, with exhaust tubes or external heat exchangers, as well as a wide range of evaporative coolers
The basic principle of air conditioning:
An air conditioner has a closed refrigerant system, comprising an evaporator, a compressor, a condenser and an expansion valve (or capillary), which are all connected to each other with refrigerant piping. Refrigerant gas is circulated within the system in the direction shown in the below drawing.
The indoor unit, which is usually installed in the room to be cooled, contains the process where the refrigerant evaporates within the cold element (evaporator). This evaporation is caused because the refrigerant has a very low boiling point at atmospheric pressure. To enable the evaporation, a rise in temperature is necessary. This rise is supplied by the air of the room which is to be cooled and in which the evaporator is situated. As air is passed over the evaporator the air temperature will drop and therefore enable the room air temperature to be reduced.
The compressor draws the vapour refrigerant and reduces the pressure in the evaporator. Because of this pressure reduction, the refrigerant evaporates. The vapour which is drawn by the compressor is then compressed. The pressure and temperature of the gas rises as it is compressed into the condenser, where the warm gas is cooled down to the condensation temperature of the refrigerant. Subsequently the vapour returns back to liquid again.
In the condenser, the process is almost directly opposite to the evaporator. The condenser requires cooling otherwise the temperature and gas pressure will rise too high. For this cooling process either water or air can be used. The vapour which has now returned to liquid again is now passed through the expansion valve (or capillary) to the evaporator. Because of the narrowing of the pipe work the pressure decreases and the refrigerant evaporates once more. To enable this evaporation the warm air is needed and so the circuit is closed.
The operation of portable air conditioners
We offer 3 types of portable air conditioners
Exhaust tube units:
With these units both the evaporator and condenser are positioned within the room unit. The majority of the air that is passed through the unit is directed over the evaporator and returns back into the room, as cooled air. A smaller volume of air is passed across the condenser to cool the refrigerant gas. This air needs to be removed from the room as it becomes hot. An exhaust tube is used to remove this hot air via an opening in the room (usually through a window), in some cases the exhaust tube may be positioned into a false ceiling void, advice should be sought before using this system.
Split type units (refrigerant):
These are models similar to the PAC14, such units have 2 parts, a room unit and a condenser. The room unit placed within the area to be cooled comprises of an evaporator and a compressor. The room air enters the unit and once passed across the evaporator is returned into the room as cooled air. The external unit (which is connected to the room unit by a flexible pipe) contains the condenser which needs to cooled by ambient air, therefore the external unit needs to be positioned outside of the room. Typically the condenser is hung from a window.
Split type units (water):
This range includes the PAC15, Zephyr (PAC), PAC22 and PAC60. These units are also supplied in 2 parts, a room unit and a heat exchanger. The principle in operation is very similar to that of the refrigerant units. The major difference is that the condenser is placed within the room unit and cooled by water. The water is then circulated to the external unit (heat exchanger) via flexible pipes before returning to the room unit. The system is totally sealed and requires no further water once the unit is in place. The main advantage of this system is that the connection pipes can be extended, allowing the heat exchanger to be positioned up to 30 metres away from the room unit.
Applications for temporary air conditioning equipment
- Events & Exhibitions
- Temporary accommodation
- Shops and Restaurant
- Storage of heat-sensitive products
- Computer server rooms
- Spot Cooling
- Telecommunication rooms
- Production Facilities
- Process control rooms
- Hotel and conference centres
- Printing and reprographics
- or any application where a fixed unit has broken down or needs to be shut down for maintenance.
Calculating the cooling capacity required and choosing the type of air conditioning
The heat load for each individual room can vary considerably. The amount of cooling required depends on the number of lights, the number of people, the amount of glass area facing the sun and also the number of computers or other heat generating electrical equipment in the room. It is important to consider these factors in order to determine the capacity correctly.
An Andrews specialist will be pleased to visit your premises at a time to suit you, they will provide you with an accurate cooling calculation for you and recommend the best unit for your application. Alternatively you can use our online calculator to select the best unit for your application by clicking here.
Selection and installation of your portable air conditioner
To select what size and which type of temporary air conditioner you need, you must first consider the capacity of the unit and the possible alternatives to remove the condenser heat. The follow can be used to estimate the amount cooling required.
Normal Modern Offices: 46 W per m3
Portable Buildings: 57 W per m3
Tents/Marquees: 95 W per m3
In addition to the type and size of the area to be cooled, consideration must be given to any electrical appliances that generate heat in the area. Such appliances are listed below along with the approximate heat emission that they generate.
Personal computer: 100 watts
Printer: 300 watts
Photocopier on standby: 200 watts
Photocopier in use: 800 watts
TV screen: 300 watts
Coffee machine: 800 watts
Before you select your Andrews portable air conditioner we suggest the following issues should be considered.
- The indoor unit (evaporator) needs to be positioned within 1.5 metres of a 13 amp 230 volt socket. Always ensure that the electrical supply for the unit is adequate and that the operation of the unit will not cause any problems to other sensitive electronic equipment on the same ring main.
- Ensure the room unit is located in a manner to avoid any obstruction to the airflow. This will ensure an even distribution of the cooled air. Make sure the room unit is level and that any condensate can be safely removed.
- If you are to use a split type unit, the heat exchanger (condenser) will need to be positioned outside of the building or in a very well ventilated area that can withstand the heat transferred from the room being cooled. Condensation is discharged from the room unit to the heat exchanger where it is allowed to drain to the outside of the building. If the heat exchanger is placed within the building a separate means of discharging the condensation needs to be provided.
- When using a PAC unit it is always advisable to position the heat exchanger away from direct sunlight or any position where its operation is likely to cause disruption. The heat exchanger can only be positioned within the distance specified by PAC line length. Always aim to keep the PAC line length to a minimum.
Portable evaporative coolers for hire
There are many applications where it is impossible or impractical to use portable air conditioners. In such cases an alternative may be the use of an evaporative air cooler. These units are often used where access to an external source is unavailable, the Andrews range of evaporative air coolers can help overcome uncomfortable conditions.
The evaporative concept is designed to cool fresh air through the process of natural evaporation by drawing air across a wet filter they provide a refreshing cool air flow. As the air passes the wet filter, the moisture evaporates and a drop in temperature will result, although the overall room temperature will not be reduced, the unit does provide localised comfort cooling.
Applications for evaporative coolers
- Sports halls and gymnasiums
- Large manufacturing areas
- Outdoor events and marquees
- Retail outlets
- Night clubs