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Emerson
 
Central A/C refers to any system where single condensing units can simultaneously cool/heat more than one room. Essentially, a single condensing unit drives the whole refrigeration cycle for a central A/C, and the cooling/heating work derived from this cycle is sent to multiple rooms via various possible medium, including air, water, and refrigerant. Due to the need to cool and heat multiple rooms from a single driving source, the design of central A/Cs require a lot more consideration in terms of load calculations and piping needs.
Capacity range for central A/Cs is very wide, from small residential types (as low as 7100W) to large commercial types for entire buildings. Given this wide range, the range of central A/C types is also wider than the other A/Cs, including window-type, single-split wall-mounted, and packaged A/Cs. |
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Central A/C is one type gaining in popularity for residential use, and is a good choice in cases where multiple rooms exist and floor area is above 100 m2.
In choosing a suitable central A/C, we need to further compare the various central A/C sub-types. Look at the current market, we find three main types of central A/C (by medium of heat transfer): air duct type, water chiller, and VRF. |
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An air duct type central A/C uses air as the medium of heat transfer to individual rooms, while the condensing unit is centralized. Hence, the refrigeration cycle takes place in a single unit, and a heat exchanger is then used to cool/heat the air that runs through the multiple rooms. In this case, air ducts are used to carry the cooled/heated air. A powerful centralized fan moves the air through the duct and at the same time can draw in fresh air to ventilate the rooms. Air duct types are usually used for residential (such as villa) or small commercial applications. |
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Water chiller A/C systems are most commonly used for large commercial applications especially an entire office building. However, some smaller versions are now in use for residential or small commercial applications.
As the name suggests, water is the medium of heat transfer in a chiller system. As with the air duct system the refrigeration cycle is centralized, but a heat exchanger is used to cool/heat water rather than air. This water then cycles through the individual rooms and a fan coil unit in each room exchanges heat with the water before delivering air into the room. |
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| Where the application covers a large area (like an office building), an air duct system for each floor might be used to cycle air through individual rooms rather than the water. In this case, the water exchanges heat in a centralized air-handling unit, and then the air is delivered as per the usual air duct system. |
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VRF Central A/C system uses refrigerant as the medium of heat transfer to individual rooms. This type of system is generally suited for residential or small commercial application, but multiple systems can be pieced together to cover a larger area.
Current applications of VRF system apply modulation in one form or another. Copeland Digital Scroll is one of these forms, and is the latest technology in the market. Other variable capacity forms include the inverter technology and hot bypass. |
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