There are two types of central air conditioning systems: Direct Expansion (DX) type of central air condition plants and Chilled Water type of the central air conditioning plants. In the DX system the air used for cooling the room or space is directly passed over the cooling coil of the refrigeration plant. In case of the chilled water system the refrigeration system is used to first chill the water, which is then used to chill the air used for cooling the rooms or spaces.
Direct Expansion (DX) Type of Central Air Conditioning Plant
In the direct expansion or DX types of air central conditioning plants the air used for cooling space is directly chilled by the refrigerant in the cooling coil of the air handling unit. Since the air is cooled directly by the refrigerant the cooling efficiency of the DX plants is higher. However, it is not always feasible to carry the refrigerant piping to the large distances hence, direct expansion or the DX type of central air conditioning system is usually used for cooling the small buildings or the rooms on the single floor.
Centrifugal chillers are highly energy efficient and are equipped with the new generation centrifugal compressors with magnetic bearings. These two-stage compressors, coupled with the in-built Variable Speed Drives, enable significant reduction in the operating cost as well as reduce emissions.