Systems of Air-Conditioning

Based on the location of air-conditioning equipment, the systems of air-conditioning are classified into the following four systems:

1. Central System
2. Self-contained system
3. Semi-contained system
4. Combined system

All the above systems invariably adopt the same cycle of operations as given below.

1. Sucking the air through the filter media.
2. Cooling the air in summer and heating it in winter.
3. Dehumidifying if it is to be cooled or humidifying if it is to be heated.
4. For using the processed air into the rooms or space for proper circulation through grills.
5. Collecting the used air through exhaust and mixing with the outside air and sucking again the air through the filter medium, which completes the cycle.

1. Central System

In this system all the equipment and accessories needed are installed one focal point or central point. From this point the conditioned air is distributed to all the room and intended spaces through concealed ducts.

This system requires less accommodation as all the units are placed at one place and for the same reason it is also economical. Maintenance is also simple. However, the ducts occupy more space at the ceiling level, Fig. 28.3 (Sharma, 1988).

Figure 28.3 Layout of a central system of air-conditioning

2. Self-contained System

This is also called a unit system. In this system, the conditional air and distribution are kept in place that is why it is called self-contained system. Here no ducts are provided. Special, portable and attractive cabinets are provided for the distributing unit. Window air-conditioner is a typical self-contained system, Fig. 28.4.

Figure 28.4 Layout of self-contained system of air-conditioning

3. Semi-contained System

In this type of system, every room is provided with an air-conditioning unit. This unit receives the supply from a central system. Because of this, lesser size of ducts are used. In another set up of this type, the conditioned air may be supplied from a central unit but the heating or cooling may be done in the room itself.

4. Combined System

This combined system comprises of.

1. Central and self-conditioned system,
2. Central and semi-contained system and
3. Self-contained and semi-contained system.