**3. Conclusion**

This chapter reviews the types of central air conditioning systems. Specifically, the types and applications of all-air, all-water, and air-water systems are provided. In addition, this chapter gives further insight to all systems through several developed schematic diagrams as various components and working principles of these diagrams and systems can be identified and figured out, respectively. Moreover, the differences among the given systems can be easily distinguished through this chapter.

*2.3.1 Induction unit system*

*A schematic diagram of an induction unit system. Readapted from [5].*

**Figure 19.**

**16**

**Figure 18.**

*Low-temperature Technologies*

*2.3.2 Primary air fan coil systems*

Induction unit systems in air-water central air condition are used in building of multi-surrounding rooms such as offices, hotels, hospital patient rooms, as well as apartments. These systems are used where higher thermal loads are present. In addition, these systems are suitable where some rooms require cooling, while the next other rooms require heating. Besides that, these systems are suitable for buildings such as skyscrapers where the spaces are limited. **Figure 19** shows a schematic view of induction unit system which uses primary air and external air. Return air can be used if all primary air is greater than the minimum ventilation requirements [1–5].

*A schematic diagram of a fan coil unit of four-pipe system. Redrawn with modification from [2].*

The working principle of primary air fan coil systems is very similar to the induction unit system. The main difference is the use of fan. These systems are *Low-temperature Technologies*
