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Air Conditioning

Air conditioning treats the air to control temperature, humidity, cleanliness, distribution, and quality. Two main types of air conditioning are used in most businesses - refrigerative and evaporative. 

Below you will also find some air-conditioning tips.

Refrigerative air conditioning systems

A refrigerative air conditioner transfers heat from the air inside the cooled space to outside the space. 

The heat is absorbed by refrigerant in the evaporator (inside the cooled space) and then transferred to the condenser (outside the cooled space). The refrigerant is ‘pumped’ from the evaporator to the condenser by the compressor. This compressor is the main user of energy in a refrigerated air conditioner.

Figure 1: Refrigerative air conditioner.

The diagram above shows the basic set-up of a refrigerative air conditioner. There is usually at least one ‘supply air’ fan which forces air over the evaporator and into the space. There may also be a fan which forces air over the condenser to help remove heat from the condenser.  

Larger systems may use water to cool the condenser and they may have a central chiller (compressor) to cool water which is then pumped to a number of air conditioners to cool the air. Larger ducted air conditioning systems may also have a return air fan. 

Improve the efficacy of an air conditioner and you’ll need less energy to generate the same amount of cooling. That is, the compressor won’t need as much energy to cool the space. 

Evaporative systems

You could probably guess that evaporative cooling systems work by evaporating water to provide cooling. More specifically, outside air is drawn through a wet filter pad and cools as the water evaporates. The cooled, humidified air is then pumped through the building. 

Evaporative cooling only works effectively in low humidity areas – in Western Australia this is mainly the southern and inland areas. In these climates evaporative cooling is the most energy efficient cooling available. And the humidified air is usually welcome relief from Western Australia’s typically hot, dry outdoor air. 

Evaporative systems naturally supply 100% fresh air, making them particularly cost effective where fresh air requirements are high. It also means that evaporative systems are ideal for buildings with poor air sealing or where doors must be left open, as is often the case in retail businesses. The large air flows provided by the evaporative systems also result in a pleasant breezy atmosphere. 

Evaporative coolers are available in a large range of sizes, from small portable units that must be manually filled with water up to very large ducted systems, which are the most common in businesses. The portable units may provide some valuable spot-cooling when other types of cooling are not available, such as cooling points where staff are working in a mechanical workshop.

Air conditioning tips

Minimise external heat gains and losses

The most critical factor in minimising external heat gains is the design of the building being cooled. Compared to a poorly designed building, well-designed premises can reduce cooling requirements (excluding internal heat gain) by at least 50%.  

Although it is rarely possible to raise the performance of a poorly designed building to that of a well-designed one, some installations worth considering include:

• insulation
• double glazing
• shading
• window tinting/reflective coating
• blinds/curtains

You can also help to reduce cooling costs by keeping leaks and openings (doors and windows) to a minimum. 

Minimise internal heat gains

Internal heat gain (from occupants, lighting, refrigeration and cooking equipment, office equipment and even some components of the cooling system itself) can significantly increase cooling requirements. This is particularly true in larger commercial buildings, where it may contribute to 30% to 50% of your cooling costs. In fact, most of the energy used in a building ends up as waste heat that must be extracted by the cooling system.

Reducing internal heat loads provides a double energy saving – not only is the energy used by the equipment reduced, but reducing your cooling requirements can save an additional 10% to 40% energy, depending on the cooling system used. 

To minimise internal heat gains:

• Use energy efficient lighting
• Avoid using electrical equipment unnecessarily
• Provide a separate ambient air supply and extraction system for equipment that generates heat
• Locate heat-generating equipment outside the building

Set appropriate temperature limits

Naturally, you’ll need more energy to cool the air if you choose a low cooling temperature set-point, and vice-versa. Normal air conditioning temperature set-points are in the range of 22°C to 24°C.

Other ways to reduce your need for a low temperature include:

• allowing the temperature to drift within a range of values
• encouraging employees to dress ‘appropriate to the season’
• consider the use of evaporative air conditioning where closely controlled temperatures are not required

Maintain equipment properly

It goes without saying that a properly maintained system will be more efficient than one that is not being regularly maintained. Most components of air conditioning systems involve mechanical moving parts that need regular maintenance and adjustment to ensure that they operate as designed:

• Keep heat transfer surfaces (such as condensers, evaporators, cooling coils, heater elements) clean – dust and dirt can act as an insulator, reducing the ability to heat or cool the air
• Regularly check and adjust controls such as timers and thermostats
• Ensure dampers and valves are opening and closing fully
• Maintain refrigeration equipment to keep it working efficiently
• Fix any leaks in ducts and pipes
• Keep your insulation in good condition

Further information

Find out how to reduce your energy costs, by contacting your account or business manager.

For more information on energy efficiency in your business visit the Sustainable Energy Development Office at http://www1.sedo.energy.wa.gov.au