How Does Central Air Conditioning Work?

I'm sure you are aware that air conditioning comes in many forms, and what we are looking at here is just another method, but just how does central air conditioning work?

All air conditioning systems tend to work on similar principals and central air conditioners are purpose built to cool the entire home and makes use of ducts to disperse and recycle cooled air throughout rooms on a continual basis. Some models may also move chilled water via pipes and heat exchangers.

Most frequently you will find a split system where the condenser and compressor are located outdoors and connected by refrigerant lines to a coil (or evaporator) in the in the air handler unit. Such a unit basically resembles a metal box that may comprise of a blower, filters, heating/cooling elements, mixing chamber, humidifier, controls and vibration isolators. In contrast, with a 'packaged' system, everything is normally located in a single outdoor unit.

Heat from the home is transferred to the outside using a compressor cycle that works similarly to a refrigerator. A refrigerant fluid is passed through an expansion device which changes from liquid to gas when it absorbs heat and is then released outdoors at high pressure as vapour before changing back from gas to liquid. The fluid will then return to the expansion device and the process repeated.

The air in the home is cooled as it travels over the evaporator; the moisture removed from the air and disposed of by the unit via the household drainage system.

Central air conditioning has a few benefits over other systems as the air is drawn through a filter from parts of the building. This filter extracts any dust and lint particles cleaning the air as well as cooling it. Additionally, specialist filters can also remove microscopic pollutants which can affect health. A further benefit is that noise is reduced as the unit is external to the building.

Central air conditioning is an efficient system but you do need to try and get the highest SEER rating you can afford (the range is 10 to 17). (SEER refers to the Seasonal Energy Efficiency Ratio.) If the unit carries the Energy Star label, it will have a SEER of at least 13 for a split system and 12 for a single unit. A unit with a lower SEER will be uneconomical so if you are considering buying anything second-hand, do watch out for this as the newer units are mostly over 12.