What is HVAC system? A very common question. HVAC is a very common word now a day to make ourselves comfortable. The weather conditions are different based on the locations, seasons etc. In a room, if there is heat-generating equipment, the temperature my very high even in the winter.
Now, how does HVAC makes us comfortable as well as helps to control the temperature?
Let’s explore the details of the HVAC system!
HVAC is an abbreviation of heating, ventilation, and air conditioning. Here,
H – Heating
V – Ventilation
A – Air
C – Conditioning
HVAC is a system by which heating, or ventilation of air conditioning together or individually can be done.
This system can provide the required heating and cooling capacity to the residential and commercial buildings.
HVAC units are available in various capacities based on the applications.
HVAC is a system that is able to provide heating, or ventilation, or air conditioning based on the requirements.
Alfred Wolff made the first comfortable air conditioners and Willis Carrier first invented the first process air conditioners.
The use of heating or cooling to control environmental (room) space;
The process of changing or replacing air in a space. It is used to remove moisture, odors, heat, carbon dioxide, etc, and replace it with ‘fresh air’. It is considered to be one of the most important factors for good indoor air quality. The design process would specify a number of ‘air changes’ within a room, depending on usage;
The supply air is ‘conditioned’ to control the temperature and humidity. Humans like a room temperature of 18 – 23°C and a relative humidity of 30 – 70%. ‘Relative’ humidity is a measure of humidity compared to the maximum possible humidity.
The main purpose in short,
The main purpose of the air conditioning system is as follows:
There are so many components in the HVAC system, and it varies based on the type of system.
However, to understand a basic concept, few components are listed:
HVAC principle is based on three things
We will learn the basic of the HVAC system, briefly,
Heaters are necessary for many places to increase the temperature as required. In this process, steam or air or hot water or electric heating coils are used.
Heat can be transferred in three ways,
Ventilation is the process by which indoor contaminated or polluted air is replaced.
The air conditioning system is totally based on a refrigeration cycle consists of,
The basic of the refrigeration process, are follows,
Heating is one part of the HVAC system, In the cold area, as well as where humidity is very high, heaters are required to increase the temperature as well as to reduce the moisture level within acceptable limits.
Various kinds of heaters are used to generate heat in residential as well as commercial applications. The followings can be used to produce heat,
The boiler is basically a pressure vessel. It has a combustion chamber to generate heat.
Boilers can be made of,
In the furnace, there is a combustion chamber where fuel is burned. Here, no secondary working fluid is required. Air is heated and it is transferred through a duct to the space to be conditioned.
The furnace consists of,
Heat pumps, now a day widely used to have duel functions like furnace & air conditioners.
Heat pumps can be,
Air to air heat pumps is widely used in normal residential applications.
In a hydronic system, water is heated or cooled and circulated to the areas to be conditioned through pipes.
Solar heating is widely used now a day. Water is heated by the sun or solar energy and that energy helps for the heating of the space. There is various way, to harness solar energy & use to get heat energy.
Chimneys are used to control the heat by controlling the draft to convey flue gas from a furnace or boiler to the outdoors.
Electricity is widely used to heat the heating elements & control the heating requirements.
Ventilation is one of the main parts of HVAC. It helps to provide fresh air into the conditioned space. It helps to limit a certain temperature range. Odors or fumes from an enclosed area can be removed by the ventilation system.
There many different ventilating methods:
Natural ventilation is the primitive method and it is used for a long. In our home, we see small openings are given at a higher level. This is due to maintaining natural ventilation.
Now a day, there are many modern methods have been created to make proper natural ventilation system.
Push type ventilation
In the supply ventilation system, fresh air is forced to provide into the room and maintain positive pressure.
Supply air fans are used and it may be non-ducted or ducted based on the capacity or requirements. This ventilation is also called as push ventilation.
Pull type ventilation
There are so many areas, where fumes or odors are produced like battery room or toilets or pantry etc. and it is required to be removed. In this case, exhaust fans are used to create negative pressure and remove it.
This ventilation is known as pull ventilation.
When supply and exhaust systems are required, we called the system as push-pull type ventilation system.
It can be done by providing supply fans for the supply system and exhaust fans for the exhaust system.
Air conditioning systems used to cool the conditioned space. How air conditioning system works, is described in the simplest way to get a basic idea,
Air Handling Unit – This unit is used to handle air. It consists of a cooling coil, filters, moisture eliminators, etc. Refrigerant is circulated through this cooling coil (evaporator) and gets the heat from the air.
Refrigerant pickup heat – Air loses heat and becomes cool. On the other hand, refrigerant picks up the heat and gets heated. This refrigerant then passes through the compressor and condenser and comes back to the cooling coil through an expansion valve.
Cooling of air – Cold air is circulated to the rooms and cool it. After sometimes, it takes the heat from the room and circulated back to the air handling unit through fan suction. This recirculation continues.
Filters – Air handling unit is having filters so that filtration is done and we get clean air.
Moisture eliminator – Air handling unit is having moisture eliminator, if the air is having moisture content, it separates from the air.
Duct – Ducting system is used to circulate the air, definitely it depends on the type of system and the air quantity.
Diffuser, grilles – Supply air is circulated through the duct at many points, these points are fitted with diffusers or grilles.
Condensing units – Refrigerant release heat in the condensing units. In this unit, condenser coils are used and with the help of condenser fans, heat transfer happens between refrigerant and air.
Don’t be confused between HVAC and air conditioning. Air conditioning is simply a part of HVAC.
Don’t think HVAC means big systems like a central system and air conditioning means a normal split system. Just remember, air conditioning is a part of HVAC.
There are so many types of the HVAC system, and the working principle of air conditioners are different. However, few of the standards system is explained for understanding;
For small capacity and to meet normal residential cooling, window type air conditioners are used.
Split AC means air conditioning divides into two parts, indoor and outdoor.
This can be floor mounted, ceiling mounted or wall mounted.
Packaged AC means all components are packed in a single unit. If you observe, you will see both indoor and outdoor units are placed in a single packaged.
Normally, packaged air conditioners are used when medium capacities are required. Ductwork is connected to get the supply air into the conditioned space. To get return air from the room, a separate return duct is also provided.
Normally condenser of packaged units is cooled by air, but it can be cooled by water as well
Central AC is of two categories. DX type and chilled water type.
DX Central AC – In this case, the chiller is cooled by air.
Water-cooled chiller – In this case, condensers are cooled by water circuits that connect with cooling towers.
Advantage of HVAC system
The advantage of HVAC system simply is a lot in human comfort as well as all industries.
The disadvantage of the HVAC system
There are a few disadvantage as well,
There are so many codes and standards available for the HVAC design, construction, system design, equipment design, operation & maintenance, quality, safety, etc. Few are listed,
In this lesson, we have learned the basics of the HVAC system. Hope, it is clear, any doubt please let us know.
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