What is an HVAC system?

The "HVAC" system, also known as the air conditioning system, is a heating, cooling, and ventilation system that is larger than a typical home air conditioner, giving it the potential to transfer air to improve air quality. It is therefore suitable for office buildings, department stores, houses of two stories or more, as well as warehouses and industrial plants that require temperature and humidity control for production.

Now, let's take a look at what an HVAC system is and how it works.

What is HVAC?

HVAC system is an air conditioning system that manages air to control temperature, humidity, cleanliness, and distribution as required for a given space. It consists of H-heating, V-Ventilation, and AC-Air conditioning.

The HVAC system consists of three main components:

1. Heat: Piping systems for heat-conducting fluids or ducts, if it's a forced air system.

2. Ventilation: Either natural or forced. Forced ventilation is most commonly used for air purification.

3. Air conditioning: This is the process of removing heat from the interior of the building.

The HVAC system's structure is that all three systems work together at all times to ensure efficient air management. Therefore, it is suitable for industrial locations with complex closed systems or locations that require temperature and humidity control.

What is the function of an HVAC system? What is it like?

Appropriate control of the climate in a room depends on the type of room use. However, in general, the temperature and humidity that create a comfortable feeling, or Thermal comfort, are controlled at 22-25 degrees Celsius, with relative humidity controlled at 30-60% RH and an air ventilation rate of approximately 20% of the total amount of circulating air. Other uses are determined according to the standards of each type of room as follows:

1. Temperature control

The system controls temperature by using a coil panel as a connector between the refrigerant and the air. This allows the air inside and outside to exchange only heat. The cooling coil draws heat from the air inside the room and the hot coil dissipates heat from the refrigerant, which absorbs heat from the air inside the room, to the outside. The outside air dissipates heat from the hot coil. Depending on the usage pattern, each room will have a different optimum temperature. Therefore, we divide it as follows:

• Room temperatures for humans generally range from 20 to 26 degrees Celsius, according to ASHRAE Standard 55-1992. This range depends on the type of room used and the user's preferences.

• Room temperatures for animals vary, and the body temperature of each animal is typically designed to be between 18 and 26 degrees Celsius.

• Room temperatures for plants: The type of plant determines the temperature used. Designs can range from temperate to tropical plants, and optimum humidity is often considered. The design temperature range can range from 18 to 40 degrees Celsius.

• Room temperatures for chemicals or equipment used to store chemicals, including some types of equipment, require an appropriate temperature range to prevent chemical reactions and minimize damage to electronic components.

2. Humidity control

Normally, in reducing the temperature, the cooling coil panel will function to reduce the temperature of the air and reduce the humidity in the air at the same time. When the air hits the cooling coil at the condensing temperature, the humidity in the air will condense into water droplets. However, for the cooling coil panel, the efficiency in reducing the temperature will be greater than reducing the humidity in the air. Therefore, the temperature must reach a predetermined point before the humidity drops to the predetermined point. Therefore, in reducing the humidity in the air, the cooling coil panel that is still working will cause the room temperature to decrease continuously. And there must be a device to increase the heat to raise the air temperature to be equal to the predetermined point.

There are many systems for increasing heat, but the most popular system currently used is the installation of an electric heater. This system can immediately add heat to the system and is easy to control, but in exchange for increased heating energy.

 

3. Air circulation

Air circulation is extremely important. If air is not distributed evenly, it will create dead corners, which will result in a lack of air circulation in that area, causing the accumulation of carbon dioxide and various germs, causing people in that area to feel uncomfortable, stuffy, or even infected by germs. Research has shown that the appropriate air circulation in a room used for various activities is calculated by the air circulation rate in units of room volume per hour (Air Chang per Hour, ACH). General air circulation systems are designed based on the ratio of indoor air to outdoor air. They are divided into 2 systems:

• Single-Pass Air: This system does not recirculate indoor air. Instead, all outdoor air is taken through the air conditioning system and used to condition the room. The entire room is then exhausted.

• Recirculation Air: Because air conditioning requires energy to reduce temperature and humidity, the larger the room, the more energy is consumed. Recirculation involves taking approximately 80% of the pre-conditioned and humidified indoor air, mixing it with approximately 20% of the outside air, and then re-entering the system.

4. Air pressure in the room

To control contamination between the interior and exterior, there must be a difference in air pressure. Air is a collapsible fluid, typically flowing from high pressure to low pressure. Based on this principle, contamination prevention can be divided into two types:

• Negative Pressure Rooms: These rooms have lower air pressure than the surrounding room or environment. These rooms are used to control the spread of pathogens to the outside environment, such as isolation rooms for airborne infectious diseases, laboratory equipment, etc.

• Positive Pressure Rooms: These rooms have higher air pressure than the surrounding room or environment. These rooms are used to prevent external pathogens from mixing with the air inside the room, such as dust-free parts production rooms, operating rooms, and sterile rooms for infectious-prone patients.

5. Air filtration

The air is mixed with dust and various particles, which are the root cause of many causes of harm to humans, manufacturing processes and research errors, especially the spread of germs. In order to separate these foreign objects, it is necessary to have an air filtration system that is efficient and consistent with the standard air flow rate of each type of room. The standards that are accepted worldwide are:

• The pre-filter is the first filtering stage, reducing large dust particles, increasing efficiency and extending the life of the next, finer filter.

• The medium filter is the final stage, filtering up to approximately 95% of dust particles.

• The HEPA filter is the final stage, before the air is delivered to the room, filtering up to approximately 99% of dust particles as small as 0.3 microns.

HVAC System

The difference between HVAC and air conditioning

• HVAC vs. Air Conditioning: Air conditioners are the final part of HVAC, but they are often used interchangeably. When referring to all types of heating or cooling equipment in a home, HVAC is considered an umbrella term, while air conditioners are only one part of the system.

• HVAC System Lifespan: The lifespan of an HVAC system depends on how long the equipment lasts and whether it is regularly maintained or serviced. If the operator or user follows maintenance recommendations, the equipment will function efficiently for many years. Choosing the right air conditioning system for your application can significantly save energy, especially in large office buildings, shopping malls, and factories where temperature control is essential. HVAC systems are ideal for maintaining a constant indoor temperature and removing moisture, which can lead to problems down the road.

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