Widely used, domestic air-conditioners come in two types: window type and the split type. The split type is divided into two units: the compressor, which is the heart of the air-conditioner and also the noisier part which works outside the room, and the evaporator which works inside the room. The split type is more convenient because the noise of the AC is kept well outside the room. Choosing an AC's tonnage depends on where you instal it & the size of the room. For an average sized living room or office cabin, you would need a 1-ton or 1.5-ton AC. A 1-ton AC can cool approximately 180 sq. ft. If installed in a restaurant of the same proportions, added tonnage is required since the head count and the body heat are greater, increasing the load on the AC. For an office set up, the best choice is an Air Cooled Split Ductable which conveys cool air through ducts into space. This is recycled with some fresh air. If soft water and space for a cooling tower are available, go for water-cooled self- contained units. For rooms with computers and in electronic telephone exchanges, where control of temperature, humidity and air cleanliness are important, close control units of 7.5 tons to 10 tons are recommended. If your AC is exposed to sunlight, insulate. Reduce glass area in a room with an AC, since glass allows a lot of heat inside. Always allow for free circulation of air behind the condenser.