WHAT IS AN HVAC SYSTEM? WHAT ROLE DOES THE HVAC SYSTEM PLAY IN CONSTRUCTION 

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2. HVAC system installation diagram
Basic components of the HVAC system:

• Inlet air assembly: Helps prevent insects and dust from flying inside.
• Sound absorber: Helps reduce noise during use.
• Air control valve: Can have 1 blade or multiple blades, adjusting the amount of air and wind entering the room through the system. 
• Control valve: To control air flow and pressure.
• Heating coil: Adjusts the air temperature to the appropriate temperature.
• Cold coil: Helps separate moisture and reduce the humidity of fresh air entering the room when it reaches the appropriate cold temperature.
• Humidifying cluster: Helps increase air humidity to the appropriate level if the air humidity is low compared to the humidity in the room.
• Filter: Removes many types of dust of different sizes 
• Coarse filter helps remove large bacteria and dust.
• The fine filter helps remove small sized microorganisms.
• Air duct: Helps circulate air to help regulate air from the air handler to the environment.

3. Structure and operating principle of the HVAC system

3.1. Structure 

- The air handling unit (AHU) has the function of providing air and controlling the quality of air brought in from outside.

- Excessive humidity, odors and environmental contaminants when introduced will be diluted or replaced with air from outside.
- In apartments, the kitchen or bathroom is often installed with a ventilation system to guide odors or humidity.

- Ventilation methods:

• Natural method: A method of circulating outside air without using ventilation fans or other mechanical systems. Air is passed through small vent windows. Some buildings use the “stack effect” to get the best amount of air from outside. This method takes very little energy, so sometimes, the air quality may not be as expected.
• Artificial method (ventilation with ventilation fans): This method uses ventilation fans, ducts, and controllers to control the quality of air circulating in building.

3.2. Principle of operation 

In the HVAC system there are 3 types of air: fresh air, return air and exhaust air. In a normal GMP clean room, 80 - 90% of the air is returned, the remaining 10 - 20% of the air is fresh air filtered and supplied from the outside environment, this helps ensure the amount of oxygen supplied to the people. operate in the factory.

Particularly for clean rooms producing vaccines and microorganisms that require high requirements for cleanliness and infection limits, the air in the clean room is continuously changed with 100% of the air in the room being fresh air.

The HVAC system uses the following operating principles:

• Fresh air in the air after being dehumidified will pass through the inlet air cluster to remove dirt and dust.
• Then go through the coarse filter to remove some large particles.
• The amount of fresh air after filtering is controlled by the air adjustment valve, adjusting the appropriate amount of air entering the room.
• After passing through the AHU device, the fresh air will have its temperature adjusted to about 22 degrees.
• Finally, the fresh air is filtered again with a fine filter membrane to remove small particles and bacteria. At this time, fresh air will be supplied to the clean room for use.

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4. Functions of the HVAC system
- As an important and indispensable structure in the project, the heating, ventilation and air conditioning system are closely related to each other. 

- The HVAC system has an important function: Providing the best air quality for humans in any environmental condition.

- HVAC air conditioning system

- Get cold air:

• The temperature in the air will be removed by the air conditioning system 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, switching from cooling to heating by reversing the flow of refrigerant when warm temperatures are needed.

The basic components in a common central HVAC system are:

1. Fan to circulate air and return air
2. The air supply pipe in there is the air flow from the fan supplying the air-conditioned space.
3. Gas equipment such as air supply inlets and return air intakes.
4. Return air ducts or ducts in which air flows from the conditioned space to the mixed air 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 to add heat or remove heat from circulating air.
9. Auxiliary heating equipment such as natural gas furnace or electric heating element.
10. Compress air to compress cold vapor and pump refrigerant around the system.
11. Condenser to remove heat from cold vapor and condense it into a liquid.
12. Fan to circulate outside air through air cooling
13. Pump to circulate water through the 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 water coils and back.
15. For central systems, water or boilers serve as a source of central heating.
16. For central systems, water chillers serve as a central cooling source.
17. For central system, cooling tower with water cooled condenser.
18. Controls to start, stop, or regulate the flow of air, water, steam, refrigerant and electricity.

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5. What does the HVAC system include?
Currently, HVAC systems include two main types: heating systems and ventilation systems. 

5.1. Heating system
- Devices that aim to generate heat higher than the ambient temperature (warm) for a space are called heating systems. Heat generation is done by a central heating system.

- Equipment that makes up a complete heating system includes: Equipment used to heat water, steam, and air in a central location: Boiler, heat pump.

- Heat is transmitted by convection and conduction by radiation. Fireplaces are operated through different fuel sources such as: solid fuel (coal, firewood...), liquid fuel (gasoline, oil...), gas (gas...), electric fuel. Electric heaters are often used as backup heat or heat pump systems.

- HVAC heating systems are used to create heat (warmth) in buildings or commercial centers, usually this is done by a central heating system.

General structure of the heating system in HVAC 

• Boilers
• Heater or heat pump: Used to heat water, steam or possibly air in a central location such as a furnace room in a house, a mechanical room in a large building. Heat can be transferred by convection, conduction or radiation.

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5.2. Ventilation system in HVAC

The HVAC ventilation system's job will be to change or replace the air flow in any space to control temperature or remove any combination of moisture, odors, smoke, heat, dust , or bacteria in the air or CO2 and supplemental oxygen.

In addition, the ventilation system in HVAC also includes the exchange of air flow with the outside as well as the circulation of air flow within the building.

The ventilation system in HVAC is considered one of the very important factors to maintain the quality of air inside each area of ​​buildings.

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6. Notes when using the HVAC system
Normally, when using the HVAC system, some problems will occur that cause the system to fail. Users should carefully grasp the following notes when using the HVAC system:

• The air valve may become stuck and the pipes may leak.
• The chiller compressor is missing or out of gas, causing the system to operate poorly.
• Drainage stops or works poorly, causing the system to become clogged and water to flow to the surface, affecting the product.
• The filter membrane is heavily punctured, making it less effective in removing dust and bacteria that affect the air in the working environment.
• Unstable power supply or short circuits or phase loss cause the system to stop working.

Hopefully this article has provided useful knowledge about this system in construction. Hung Nghiep Phu – with a staff of engineers, skilled workers, and construction supervisors. Hung Nghiep Phu's projects are always implemented on schedule, ensuring absolute technical safety for the project. Please contact Hung Nghiep Phu Construction Investment Co., Ltd. for advice today!

>>> See more: 

• What is MEP electromechanical system? What role does MEP play in factory construction?
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