Introduction to HVAC
What is HVAC?
It controls Temperature, Humidity and Air quality inside a building.
Especially important in medium to large buildings such as Office / Residential Towers.
All preferably integrated into one system.
Heating – It is defined as a process of increasing the temperature of a substance or a body or a
thermodynamic system.
Heating systems are designed for colder or chilled climates.
Central heating often used in cold climates to heat private houses and public buildings.
Heating systems usually comprise of a boiler, furnace, heat pump, or district hot
water toheat water, steam or air.
Piping distributes heated fluid and radiators transfer this heat to air and structures,
Ex:Floor Heating System.
Cooling – It is defined as a process of decreasing the temperature of a substance or a body or a
Thermodynamic system.
Cooling systems are designed for warmer or hot climates.
Cooling is designed for warm climates to keep the indoor conditions as per
humancomfort.
Cooling systems usually comprise of a chiller, indoor units like FCUs or AHUs to
coolthe room air.
Piping distributes chilled fluid and Indoor units (IDUs) transfer the cooling to air
andstructures. Ex: Floor Cooling System.
Ventilation – It is defined as the process to maintain the Indoor Air Quality (IAQ).
The process of ‘’changing’’ or ‘’replacing’’ air in any space to control
temperature orremove moisture, smoke, carbon dioxide etc.
Ventilation includes both the exchange of air to the outside as well as circulation of
airwithin the building.
It is one of the most important factors for maintaining acceptable Indoor Air
Quality inbuildings.
Supply air used for ventilation is filtered and cooled and/or heated inside Air Handling
Units.
This system is further classified into 2 sub-systems:
1. Fresh Air System: In Fresh Air System, fresh ambient air is been supplied from outdoor
environment to the indoor space to maintain oxygen requirement in the room. This air
can be partially or completely treated before been supplied to the room space.
2. Exhaust Air System: In this system, the bad or unwanted air is removed from the indoor
space to the outdoor environment.
Air-conditioning: It is defined as the process of conditioning or modification of air as per the
indoor conditions like temperature, moisture levels (humidity), dust levels, noise levels and
smell/odor.
It refers to the cooling and dehumidification of indoor air for thermal comfort.
Air conditioning systems are designed to stabilize the air temperature and humidity
within an area.
Excess heat from the circulating air is usually removed by a cooling coil that is supplied
with cold water / refrigerant.
To decrease relative humidity the circulating air needs to be cooled to a temperature
below the dew point and then heated back to meet the requirement.
HVAC systems control the temperature, humidity, and quality of air in buildings to a set
of chosen conditions.
The term ‘Refrigeration’ may be defined as the process of removing heat from a
substance under controlled conditions. It also includes the process of reducing and
maintaining the temperature of a body below the general temperature of its surroundings.
In other words, the refrigeration means a continued extraction of heat from a body whose
temperature is already below the temperature of its surroundings.
The basic motive of designing an HVAC system for the building industry is to maintain the
human comfort conditions inside the building space.
Human Comfort Condition:
- Temperature: 24.4oC / 76oF
- Relative Humidity: 50 %
- Air Quality: Fresh Air for Oxygen, Dust Filtration, Noise Criteria (NC) [25 – 50], Smell /
Odor
This human comfort conditions is as stated by ASHRAE, which stands for American Society of
Heating, Refrigeration, and Air-conditioning Engineers.
ASHRAE standards are followed worldwide for design, drafting and site installation of HVAC systems.Air conditioning has got wide range of applications and it is very much essential in these days.
Air conditioning is provided for some of the following reasons:
To improve productivity in offices and factories by maintaining comfort conditions to the
people.
To maintain comfortable conditions for working in hotels, labs, etc.
To avoid malfunctioning of some control panels in Electrical Control Buildings.
To maintain pressure inside the premises for avoiding outside (dusty) air in to the room.
To create healthy atmosphere inside the room by supplying fresh and filtered air into the room.
To provide clean, filtered, healthy, comfortable conditions in hospitals etc.
