**7. Local HVAC systems**

Some buildings can have multiple zones or have a large, single zone, which needs central HVAC systems to serve and provide the thermal needs [4, 5]. However, other building may have a single zone which needs equipment located inside the zone itself, such as small houses and residential apartments. This type of system is considered as local HVAC systems since each equipment serving its zone without crossing boundaries to other adjacent zones (e.g., using an air conditioner to cool down a bedroom, or using an electrical heater for the living room). Therefore, a single zone requires only one-point control point connected to a thermostat to activate the local HVAC system. Some buildings have multiple local HVAC systems as proper equipment serving specific single zones and controlled by the one-point control of the desired zone. However, these local systems are not connected and integrated to central systems, but still part of a large full-building HVAC systems. There are many types of local HVAC systems as shown in **Figure 12**.

#### **7.1. Local heating systems**

A single zone will require a complete, single package of heating system which contains heat source and distribution system. Some examples include portable electric heaters, electric resistance baseboard radiators, fireplaces and wood stoves, and infrared heaters [8].

#### **7.2. Local cooling systems**

Local cooling systems can include active systems as air-conditioning systems that provide cooling, a proper air distribution inside a zone, and control of humidification, and natural systems as convective cooling in open window, evaporative cooling in fountains [5, 6].

**Figure 12.** Horizontal hierarchy representation of the main types of local HVAC systems.

#### **7.3. Local ventilation systems**

occupants and the radiant panels, and the natural convection mode between the air and panels. Temperature restriction is recommended for radiant floor panels, a range of 66–84°F, to achieve thermal comfort for occupants (ASHRAE Standard 55). Radiant ceiling or wall panels can be used for cooling and heating process. The surface temperature should be higher than the air dew point temperature to avoid condensation on the surface during the cooling process. Also, the maximum surface temperature is 140°F for ceiling levels at 10 ft. and 180°F for ceiling levels at 18 ft. This temperature is recommended to avoid too much

The installation of such systems is often expensive compared to other types as mentioned above, but they can be useful and has a lower running cost mainly because of the surface temperature restriction. A control signal is connected to the thermostat of each zone to manipulate the medium temperature to condition the space. The used medium can be refrigerant or water mixing with inhibited glycol (anti-freeze) instead of plain water to prevent icing inside the tubes for the cooling process. The main advantage is no space required, only a few inches for the panels to be installed and no more collected dirt in the standard ceiling or the ductwork.

Some buildings can have multiple zones or have a large, single zone, which needs central HVAC systems to serve and provide the thermal needs [4, 5]. However, other building may have a single zone which needs equipment located inside the zone itself, such as small houses and residential apartments. This type of system is considered as local HVAC systems since each equipment serving its zone without crossing boundaries to other adjacent zones (e.g., using an air conditioner to cool down a bedroom, or using an electrical heater for the living room). Therefore, a single zone requires only one-point control point connected to a thermostat to activate the local HVAC system. Some buildings have multiple local HVAC systems as proper equipment serving specific single zones and controlled by the one-point control of the desired zone. However, these local systems are not connected and integrated to central systems, but still part of a large full-building HVAC systems. There are many types of local

A single zone will require a complete, single package of heating system which contains heat source and distribution system. Some examples include portable electric heaters, electric

Local cooling systems can include active systems as air-conditioning systems that provide cooling, a proper air distribution inside a zone, and control of humidification, and natural systems as convective cooling in open window, evaporative cooling in fountains [5, 6].

resistance baseboard radiators, fireplaces and wood stoves, and infrared heaters [8].

heating above occupants' heads.

62 HVAC System

**7. Local HVAC systems**

HVAC systems as shown in **Figure 12**.

**7.1. Local heating systems**

**7.2. Local cooling systems**

Many designs are available to produce attractive panels.

Local ventilation systems can be forced systems by using devices such as window fan to allow air movement between outdoor and a single zone without changing in the thermal environment of the zone. Other systems used for ventilation are air circulation devices such as desk or paddle fans to improve thermal comfort of the space by allowing the heat to be transferred by conventional mode [5, 6].

#### **7.4. Local air-conditioning systems**

A local air conditioning system is a complete package that can contain cooling and heating source, a circulation fan, a filter, and control devices. There are three main types listed below [5, 6].

#### *7.4.1. Window air-conditioner*

This system is a packaged device consisting of a vapor compression refrigeration cycle that contains a compressor, a condenser, an expansion valve, and an evaporator, in addition to a fan, a filter, control system and housing. Window air-conditioners can be installed in a framed or unframed opening in building walls and in window openings without any ductwork and distribution the cooling or heating air effectively inside the conditioned space. The air conditioning contains both evaporator and condenser where the condenser is located outside the space while the evaporate is inside the space, however, it serves the entire single zone with the thermal requirements. The heating process can be achieved by adding electric resistance coil in the air conditioning or reversing the refrigeration cycle to act as a heat pump. Many feature designs are produced to provide aesthetical values and improve the quality and response.

#### *7.4.2. Unitary air-conditioner*

It is similar to window air conditioners from the equipment perspective, but it is designed for commercial buildings. It is installed on the exterior wall of the building and generally located near the floor-wall intersection, as shown in **Figure 13**. Every single zone will contain one unitary air-conditioner as in each guest room in many hotels.

#### *7.4.3. A packaged rooftop air-conditioner*

It consists of a vapor compression refrigeration cycle; heat source such as heat pump and electric resistance; an air handler such as dampers, filter, and fan; and control devices, as shown in **Figure 14**. This system may be connected to ductwork and serve a large-size single zone that cannot be served by unitary or window air conditioners.

#### **7.5. Split systems**

The split systems contain two central devices [5, 6]: the condenser, located outdoor, and the evaporator, located indoors. The two devices are connected by a conduit for refrigerant lines and wiring. This system solves some issues of small-scale single-zone systems since the location and installation of window, unitary or rooftop air conditioners may affect the esthetic value and architectural design of the building. The split systems can contain one condenser unit and connected to multiple evaporator units to serve multiple zones as possible under same conditions or different environmental conditions.

**8. Conclusions**

**Figure 14.** Packaged rooftop air-conditioning unit.

**Author details**

Shaimaa Seyam

**References**

This chapter presents the types of HVAC systems. HVAC systems have several requirements including primary equipment such as heating equipment, cooling equipment, and delivery equipment; space requirement such as HVAC facilities, equipment room, and vertical shaft; air distribution; and piping. Type of HVAC systems can be divided into central HVAC systems and local HVAC systems. This classification depends on zone types and the location of HVAC equipment. The central HVAC systems can serve multiple and single zones and locate away from the building, which needs distribution devices. They also can be sub-classified into all-air HVAC systems, air-water systems, all-water systems, water-source heat pumps, and heating and cooling panel systems. The local HVAC systems are mostly placed inside or adjacent to the living spaces and serve one single zone. They consist of local heating systems,

Types of HVAC Systems

65

http://dx.doi.org/10.5772/intechopen.78942

[1] ASHRAE Handbook. HVAC Systems and Equipment. Atlanta, GA: American Society of

Heating, Refrigerating, and Air Conditioning Engineers; 1996. pp. 1-10

local air-conditioning systems, local ventilation systems, and split systems.

Address all correspondence to: shaimaa.seyam@mail.utoronto.ca M.A.Sc. at the University of Toronto, Toronto, Ontario, Canada

**Figure 13.** Unitary air-conditioner package.

**Figure 14.** Packaged rooftop air-conditioning unit.
