Fig. Chilled Water Central Air Conditioning for home Systems
The fans are used to blow air over the coils to improve their ability to dissipate heat to the outside and give cool air to the inside. There isn’t much difference between a window type and a split unit, and thus the same parts are also present in a split, except for the fact that in a split, these parts are separated into two different units, one placed inside the building and one outside.
Split-system units are used mostly to cool off larger areas. These units split the hot side from the cold one; i.e. the cold side consisting of the expansion valve and the cold coil is placed into a furnace or some air handler that blows air over the coil and distributes the cold air throughout the building using a series of ducts. The hot side, i.e. the condensing unit is placed outside the building. This separation enhances the split’s overall performance as the noise is reduced due to wall separation, and cooling is greater too as the hot side is further apart as compared to the window type.
The unit consists of a long, spiral coil shaped like a cylinder. Inside the coil, there is a fan that blows air through the coil, along with a weather-resistant compressor and some control logic. This approach has evolved over years as it has many advantages such as low cost and less noise inside the house (at the expense of increased noise outside). There is not much difference between a split unit and a window type air conditioner except that in a split the cold and hot sides are apart and its capacity is greater (due to the larger coils and compressor).
In large business offices, warehouses, malls, big department stores and other huge buildings, the condensing units are normally placed on the roof and can be quite massive. You may be able to see them clearly if you pass over them in an airplane. Alternatively, there may be many smaller units on the roof, each attached inside to a small air handler that cools a specific zone in the building.
In larger building, especially in multi-story ones, the split-system approach begins causing problems forcing you to turn to other alternatives. The problem starts if running the pipe between the condenser and the air handler exceeds distance limitations i.e. if the pipe runs too long, it starts to cause lubrication difficulties in the compressor, or the amount of duct work and the length of ducts becomes unmanageable. Therefore, other alternatives such as a chilled-water system have to be considered.
