Premium air conditioners

[edit] Introduction

Air conditioning systems are used to control the temperature and, in some cases, the humidity and air quality of internal spaces. The term can encompass a wide range of systems, from small self-contained and split units serving individual rooms to centralised systems serving multiple spaces.

The performance of an air conditioning system depends on factors including its cooling capacity, energy efficiency, controls, installation, maintenance and the characteristics of the building in which it operates. A high-quality system is not necessarily the most expensive system, and the appropriate choice depends on the requirements of the building, its occupants and the intended pattern of use.

[edit] Characteristics of high-quality air conditioning systems

[edit] Energy efficiency

Energy efficiency is an important consideration when selecting and operating air conditioning equipment because cooling can represent a significant proportion of a building's energy consumption. Efficient equipment can reduce electricity consumption while providing the required cooling output.

Inverter-driven systems can vary the speed of the compressor to match the cooling load rather than repeatedly operating at full capacity. This can improve efficiency, particularly where the cooling demand varies over time. However, the efficiency of the complete installation also depends on system sizing, controls, operating conditions, installation and maintenance.

Energy performance should be assessed using appropriate efficiency ratings and performance data rather than relying solely on general descriptions such as 'premium' or 'high quality'.

[edit] Thermal comfort

A suitable air conditioning system should provide adequate control of internal environmental conditions without creating excessive temperature variations or draughts. Thermal comfort is influenced by air temperature, humidity, air movement, radiant temperature, clothing and occupant activity.

Oversized equipment may cool a space rapidly but can operate for short periods and may provide less effective humidity control. Undersized equipment may operate continuously without being able to maintain the required internal conditions. Correct assessment of the cooling load is therefore an important part of system selection.

[edit] Air filtration and indoor air quality

Some air conditioning systems incorporate filters that remove particulate matter from recirculated air. The effectiveness of filtration depends on the type and performance of the filter, the airflow rate, its condition and whether it is maintained correctly.

Air conditioning should not be regarded as a substitute for adequate ventilation. Filtration of recirculated air does not necessarily remove all indoor pollutants or provide the outdoor air required for ventilation. Where indoor air quality is an important consideration, air conditioning should therefore be considered as part of the wider heating, ventilation and air conditioning (HVAC) strategy.

[edit] Reliability and maintainability

The reliability of an air conditioning system depends on the quality of its design, components, installation, commissioning and maintenance. Regular maintenance can help maintain performance, identify faults and reduce the risk of refrigerant leakage, blocked filters, fouled heat exchangers and other problems.

The availability of replacement components, access for servicing and the expected operating conditions should also be considered when selecting equipment. Equipment intended for continuous or heavy-duty operation may require different specifications from equipment used intermittently.

[edit] Selecting an air conditioning system

The choice of air conditioning system should begin with an assessment of the building and its intended use rather than simply selecting equipment with the highest nominal cooling capacity.

Important considerations include the size and geometry of the spaces, insulation and air permeability of the building envelope, solar gains, occupancy, lighting and equipment loads, ventilation requirements and local external conditions. The required cooling capacity can then be determined from an appropriate cooling-load assessment.

Different types of system may be appropriate depending on the application. Local air conditioning equipment can serve individual rooms or zones, while larger buildings may use fan coil units, air handling units, chillers or other centralised systems.

Controls are also important. Programmable operating schedules, appropriate temperature set-points and variable-speed components can help reduce unnecessary energy consumption. Smart controls and remote monitoring can provide additional functionality, but their value depends on the requirements of the building and how effectively they are used.

The external climate should be considered when selecting equipment. High outdoor temperatures can affect the available cooling capacity and efficiency of air-cooled equipment. Manufacturers' published operating limits and performance data should therefore be checked for the conditions in which the equipment will operate.

[edit] Refrigerants and maintenance

Refrigerant is the working fluid used in the refrigeration cycle of an air conditioning system. Different refrigerants have different thermophysical properties, safety characteristics and environmental impacts. Refrigerant selection can therefore involve consideration of efficiency, operating conditions, flammability, toxicity, environmental impact, regulatory requirements and compatibility with the equipment.

The use and handling of refrigerants is subject to applicable legislation and technical requirements. Refrigerant should not be selected or handled simply on the basis of its availability or a claim that it is 'high quality'. The refrigerant specified for a system should be compatible with the equipment and installed and recovered by appropriately qualified personnel where required.

Regular maintenance should include inspection and cleaning of filters and heat-transfer surfaces, checking condensate drainage, assessing system performance and checking for signs of refrigerant leakage or other faults. Poor maintenance can reduce efficiency, impair comfort and shorten equipment life.

For larger installations, inspection and assessment of controls, cooling capacity, operating schedules, air filters, ductwork and refrigerant systems can identify opportunities for improving performance.

[edit] Conclusion

A high-quality air conditioning system is one that is appropriately designed, correctly sized, efficiently operated, properly installed and adequately maintained. Equipment selection should consider the cooling load, thermal comfort, energy performance, indoor air quality, ventilation, controls, refrigerant characteristics and maintenance requirements.

Air conditioning is only one component of building environmental control. Effective results depend on considering the system in conjunction with the building fabric, ventilation, heating, controls and patterns of occupancy.

[edit] Related articles on Designing Buildings

• Air conditioning
• Air conditioning in non-domestic buildings
• Air conditioning inspection
• Air conditioning inspection procedure
• Cooling systems for buildings
• Local air conditioning
• Heating Ventilation and Air Conditioning HVAC
• Air handling unit
• Fan coil unit
• Refrigerant selection