**1. Introduction**

Heating, ventilation, and air conditioning (HVAC) system is designed to achieve the environmental requirements of the comfort of occupants and a process.

HVAC systems are more used in different types of buildings such as industrial, commercial, residential and institutional buildings. The main mission of HVAC system is to satisfy the thermal comfort of occupants by adjusting and changing the outdoor air conditions to the desired conditions of occupied buildings [1]. Depending on outdoor conditions, the outdoor air is drawn into the buildings and heated or cooled before it is distributed into the occupied spaces, then it is exhausted to the ambient air or reused in the system. The selection of HVAC

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

systems in a given building will depend on the climate, the age of the building, the individual preferences of the owner of the building and a designer of a project, the project budget, the architectural design of the buildings [1].

**i.** Heating and cooling coils

**k.** Cooling tower

**n.** Water chiller

Temperature, humidity, and space pressure requirements

**l.** Boiler **m.** Control

**j.** Self-contained heating or cooling unit

**o.** Humidification and dehumidification equipment

The major classification of HVAC systems is central system and decentralized or local system. Types of a system depend on addressing the primary equipment location to be centralized as conditioning entire building as a whole unit or decentralized as separately conditioning a specific zone as part of a building. Therefore, the air and water distribution system should be designed based on system classification and the location of primary equipment. The criteria as mentioned above should also be applied in selecting between two systems. **Table 1** shows

Fulfilling any or all of the design parameters

Types of HVAC Systems

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• Maximum capacity is required for each

• Equipment sizing diversity is limited

• Possible of no equipment room is needed • Equipment may be located on the roof and the ground adjacent to the building

• Less energy efficient primary equipment • Various energy peaks due to occupants'

No backup or standby equipment

• Affordable capital cost

preference • Higher operating cost

equipment

the comparison of central and local systems according to the selection criteria [3, 4].

**Criteria Central system Decentralized system**

reduce the installed equipment capacity • Significant first cost and operating cost

the conditioned area, or adjacent to or

• Considering longer equipment services life to compensate the high capital cost

• A proposed operating system which

Fulfilling any or all of the design

troubleshooting and maintenance

remote from the building • Installing secondary equipment for the air and water distribution which

requires additional cost

primary equipment

saves operating cost

parameters

Capacity requirements • Considering HVAC diversity factors to

Redundancy Standby equipment is accommodated for

Special requirements • An equipment room is located outside

Operating cost • More significant energy efficient

First cost • High capital cost

**4. Classification of HVAC systems**

HVAC systems can be classified according to necessary processes and distribution process [2]. The required processes include the heating process, the cooling process, and ventilation process. Other processes can be added such as humidification and dehumidification process. These process can be achieved by using suitable HVAC equipment such as heating systems, air-conditioning systems, ventilation fans, and dehumidifiers. The HVAC systems need the distribution system to deliver the required amount of air with the desired environmental condition. The distribution system mainly varies according to the refrigerant type and the delivering method such as air handling equipment, fan coils, air ducts, and water pipes.
