The window and split air conditioners are usually used for the small air conditioning capacities up to 5 tons. The central air conditioning systems  are used for where the cooling loads extend beyond 20 tons. The  packaged air conditioners are used for the cooling capacities in between  these two extremes. The packaged air conditioners are available in the  fixed rated capacities of 3, 5, 7, 10 and 15 tons. These units are used  commonly in places like restaurants, telephone exchanges, homes, small  halls, etc.
As the name implies, in the packaged air  conditioners all the important components of the air conditioners are  enclosed in a single casing like window AC. Thus the compressor, cooling  coil, air handling unit and the air filter are all housed in a single  casing and assembled at the factory location. 
Depending  on the type of the cooling system used in these systems, the packaged  air conditioners are divided into two types: ones with water cooled  condenser and the ones with air cooled condensers. Both these systems  have been described below:
Packaged Air Conditioners with Water Cooled Condenser
In  these packaged air conditions the condenser is cooled by the water. The  condenser is of shell and tube type, with refrigerant flowing along the  tube side and the cooling water flowing along the shell side. The water  has to be supplied continuously in these systems to maintain  functioning of the air conditioning system. 
The  shell and tube type of condenser is compact in shape and it is enclosed  in a single casing along with the compressor, expansion valve, and the  air handling unit including the cooling coil or the evaporator. This  whole packaged air conditioning unit externally looks like a box with  the control panel located externally.
In the  packaged units with the water cooled condenser, the compressor is  located at the bottom along with the condenser (refer the figure below).  Above these components the evaporator or the cooling coil is located.  The air handling unit comprising of the centrifugal blower and the air  filter is located above the cooling coil. The centrifugal blower has the  capacity to handle large volume of air required for cooling a number of  rooms. From the top of the package air conditioners the duct comes out  that extends to the various rooms that are to be cooled.  
All  the components of this package AC are assembled at the factory site.  The gas charging is also done at the factory thus one does not have to  perform the complicated operations of the laying the piping, evacuation,  gas charging, and leak testing at the site. The unit can be transported  very easily to the site and is installed easily on the plane surface.  Since all the components are assembled at the factory, the high quality  of the packaged unit is ensured.
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