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What is HVAC system and how does it work

Many definitions of an HVAC system and the principle of the HVAC system are given, but not enough to clarify, and detail makes the reader vague and not profoundly understood. Through the following article, we will present knowledge about HVAC control systems and the operating principle of the HVAC system.

1. What is HVAC? Structure and working principle of HVAC system

1.1: What is HVAC?

HVAC stands for Heating, Ventilating, and Air Conditioning (Heating, Ventilation, and Air Conditioning), collectively referred to as the air conditioning system.

An HVAC control system is a system that controls the temperature, humidity, and air quality in an indoor or vehicle space. The system’s design is based on the principles of heat transfer, thermodynamics, and fluid mechanics. The purpose of the HVAC system is to create a space with the highest temperature, quality, and humidity. Providing an acceptable level of indoor air quality and thermal comfort is a requirement for an HVAC system.

Plays an essential role in ensuring the climate in the structure is comfortable, and the old air is replaced by fresh air from outside. HVAC systems are used in both commercial and residential premises.


1.2 Structure and working principle of the HVAC system
  •  Air handling unit (AHU), whose function is to supply air and control the quality of air brought in from outside.
  • When introduced, excess humidity, odors, and environmental contaminants will be diluted or replaced with air from outside.

In apartments, the kitchen or bathroom location is often installed with ductwork to conduct odors or moisture.
Ventilation methods:

  • Natural method: A method of circulating air outside without using exhaust fans or other mechanical systems. The air is passed through the small vent window. Some buildings use the “stack effect” to get the best amount of outside air in. This method takes very little energy, so sometimes, the air quality may not be as expected.
  • Artificial method (Ventilation by exhaust fan): This method uses exhaust fans, ducts, and controllers to control the quality of air circulating in
  • The building.
1.3: Functions of the HVAC system
  •  As an important and indispensable structure in the project, heating, ventilation, and air-conditioning systems have a close relationship.
  • The HVAC system has one important function: To provide the best air quality for people in any environmental condition.
1.4 HVAC air conditioning system

Take cold air:

  • The air conditioning system will remove the temperature in the air with refrigerants such as water, air, ice, chemicals…
  • Heat removal takes place through radiation, convection, or conduction.
  • The refrigeration system will use a reversing valve, which switches from cooling to heating by reversing the flow of refrigerant when warm temperatures are needed.

The basic components in a standard central HVAC system are:

1. Fan for air circulation and return air

2. Air supply pipe in which the airflow from the fan is supplied to the conditioned space.

3. Air equipment such as the air supply and return air inlet.

4. Return air passage or duct in which air returns from the conditioned space to the mixed gas chamber.

5. Air outside the device.

6. Mixed air chamber to receive room air and mix it with outside air.

7. Filter section to remove dirt particles from mixed air.

8. Heat exchangers such as hot water coils, steam coils, evaporative refrigerants, or chilled water coils add heat or remove heat from circulating air.

9. Auxiliary heating equipment such as a natural gas furnace or electric heating element.

10. Compressor to compress refrigerant vapor and pump refrigerant around the system.

11. Condensate to remove heat from the refrigerant and condense it into a liquid.

12. Fan to circulate outside air through air cooling

13. Pump to circulate water through a water-cooled condenser; condensate water pump (CWP); and condensate water supply (CWS) and vice versa (CWR).

14. Pump to circulate hot water from the boiler through the hot water coils and return or circulate cold water from the chiller through the chilled and chilled water coils.

15. Water or a boiler is a central heating source for the main system.

16. A water chiller is a central cooling source for the main system.

17. For the central system, a cooling tower with a water-cooled condenser.

18. Controls to start, stop, or regulate the flow of air, water, steam, refrigerant, and electricity.

2. What does the HVAC system include?

2.1: Heating
  • Devices that generate higher heat than the ambient (warm) temperature for space are called heating systems. A central heating system does heat generation.
  • Heart.
  • The equipment that makes up a complete heating system includes:
  • Equipment used to heat water, steam, and air in a central position: Boiler, heat pump:
  • Heat is transferred by convection and conduction by radiation. Fireplaces are operated through different fuel sources such as solid fuel (coal, firewood ..), liquid fuel (gasoline, oil ..), gas, and electric fuel. Electric fireplaces are often used as backup heat or heat pump systems.
  • Heating in HVAC is used to generate heat (warmth) in buildings or commercial centers; usually, this is done by a central heating system.


2.2: Ventilation system in HVAC

People always want the best air quality to ensure health and safety, especially in the current period, when industrialization and modernization take place like a “storm.” The birth of many industrial plants and means of transportation… entails emissions of gases being introduced into people’s living environment, causing severe consequences for the quality of life.

  • HVAC ventilation systems are responsible for changing or displacing the airflow in any space to control the temperature or remove any combination of moisture, odors, smoke, heat, and dust. Or bacteria in the air or CO2 and supplemental Oxygen.
  • In addition, the ventilation system in HVAC also includes the exchange of air with the outside as well as the circulation of air in the building.
  • The ventilation system in HVAC is considered one of the very important factors in maintaining the quality of the air inside each area in the buildings.


For more infomation about other electrical system, visit us at Colorado electrician.

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