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air conditioning system

How air conditioning systems work and how to design them

How air conditioning systems make environments comfortable, healthy, and sustainable: a guide to BIM-MEP design and tools selection

The air conditioning system is a mechanical system used to ensure thermal comfort and air quality in the buildings we live in.

In this article, we will provide a practical guide for designing air conditioning systems, together with a short analysis of the components and their technical characteristics, the indication of the main types of systems, the correct selection and sizing criteria.

We’ll also be taking a look at how the design of an air conditioning systems can be easier with a BIM software for MEP systems and show you in a short video all the advantages and opportunities that such tools can offer.

System created with Edificius-MEP

System created with Edificius-MEP

What are air conditioning systems?

Air conditioning systems are designed to control and regulate environmental conditions inside a building in order to ensure adequate thermal comfort. These systems are widely used in various types of structures, such as residences, offices, shopping centers, hospitals, and hotels.

The main objective of air conditioning systems is to manipulate the temperature, humidity, and air quality within a specific environment. These systems play a fundamental role during different seasons, providing cooling in hot periods and heating in cold ones. Air conditioning systems also help improve indoor air quality with the help of a filter system that intercepts particles, allergens, and other contaminants.

There are mainly two types of air conditioning systems: those designed for cooling and those designed for heating. Cooling air conditioning systems remove heat from the indoor environment, using refrigerants to absorb heat from the air and dissipate it through a compression and expansion cycle. On the other hand, heating air conditioning systems provide heat to the indoor environment during colder periods, using different energy sources such as natural gas and electricity.

Analysis of air conditioning system components

Let’s now examine in detail the key components of these advanced systems, understanding their essential role in the correct operation of the system.

Cooling unit

The cooling unit represents the technological core of air conditioning systems. Composed of elements such as a compressor, evaporator, condenser, and expansion valve, this crucial part of the system works together to manipulate the refrigerant and regulate the temperature of the indoor air. The compressor plays a key role, compressing the refrigerant and increasing its temperature and pressure. The evaporator then absorbs heat from the indoor air, transforming the refrigerant from liquid to gas. The condenser releases heat into the external environment, causing the refrigerant to condense back into liquid. Finally, the expansion valve reduces the temperature and pressure of the refrigerant, completing the cycle.


Fans, which are essential for the operation of air conditioning systems, are divided into two main categories: cooling unit fans and air fans. The former push air through the evaporator and condenser, while the latter distribute conditioned air in the environments. This combination ensures proper air circulation, contributing to the overall effectiveness of the system.


Ducts are a network of tubes and represent the structural part of a forced air conditioning or ventilation system, used for air distribution or recycling between the cooling unit and the conditioned environments. Made of metal or flexible materials, these ducts are equipped with vents and regulation to control the direction and flow of air. A component often overlooked but crucial for the overall effectiveness of the system.


The thermostat, the control center, allows you to regulate the desired temperature. Programmable to maintain specific levels, the thermostat goes beyond, also controlling parameters such as fan speed and system operating modes, ensuring total and personalized control of the system.

Air filters

Essential for improving indoor air quality, air filters remove particles, dust, allergens, and other contaminants. In addition to protecting the system from dirt and debris, these filters contribute to creating a healthier indoor environment.

Operation diagram of an air conditioning system

Operation diagram of an air conditioning system

How does the air conditioning system work?

Air conditioning systems work using thermodynamic principles and refrigeration cycles to regulate the temperature, humidity, and air quality inside an environment. Below is a detailed explanation of the basic operation of an air conditioning system:

Air cooling:

  1. compression refrigeration systems: the cycle begins with the compressor, which compresses the refrigerant, increasing its temperature and pressure;
  2. condensation in a refrigeration system: the high-pressure and high-temperature refrigerant passes through the condenser, where it releases heat to the external environment and condenses into a liquid;
  3. expansion valve: the low-pressure and low-temperature liquid refrigerant passes through an expansion valve, expanding rapidly and further decreasing the temperature;
  4. indoor air cooling: the low-pressure and low-temperature refrigerant enters the evaporator, where it absorbs heat from the indoor air, transforming from liquid to gas. This process cools and dehumidifies the indoor air;
  5. air distribution: the cooled air is distributed in the environments through ducts and fans.

Additional functions:

  • heating: for the heating function, the refrigeration cycle is reversed using a heat pump or a separate heating system;
  • humidity control: air conditioning systems can use dehumidifiers to remove excess moisture or humidifiers to add moisture to dry air.

System control:

The entire system is controlled by a thermostat or a control system that monitors and regulates the desired temperature, humidity, and other parameters to ensure comfort and energy efficiency.

Types of air conditioning systems

Air conditioning systems can be classified as single-split and multi-split, with significant differences in their structure and utility.

In single-split, a single indoor unit is connected to an outdoor unit, suitable for cooling or heating a single room. This indoor unit can be of different types such as wall-mounted, ceiling-mounted, or floor-mounted.

The multi-split system, on the other hand, allows multiple indoor units to be connected to a single outdoor unit. This flexibility allows for conditioning of different rooms or areas simultaneously, with each indoor unit independently controllable.

The choice between single-split and multi-split depends on the specific needs of the user: the former is ideal for individual rooms, while the latter offers a more suitable solution for conditioning different areas, ensuring individual control.

How to choose and size the air conditioning system

Selecting the right air conditioning system requires careful evaluation of several factors:

  1. room size: the size of the room affects the required power of the system. Larger spaces require more powerful systems to ensure uniform distribution of conditioned air;
  2. thermal load: accurately calculating the thermal load is essential to determine the required cooling or heating capacity. Factors such as thermal insulation, sun exposure, and the number of people present influence the thermal load;
  3. energy efficiency: to reduce long-term energy costs, it is essential to consider the energy efficiency of the system. Check the coefficient of energy efficiency (CEE) or the coefficient of performance (COP) to ensure optimal energy consumption;
  4. types of systems: evaluate the various types of systems, such as centralized systems, standalone units, or heat pumps. Analyze the advantages and disadvantages based on the specific needs of the environment;
  5. maintenance and support: verifying after-sales support and the availability of spare parts is essential to ensure the correct long-term operation. Ensure that the supplier offers adequate maintenance services;
  6. budget: establish a comprehensive budget, considering initial costs, operating costs (such as energy and maintenance), and the lifespan of the system.

How to use BIM software for MEP system design

Now let’s see why it is convenient to use a BIM software for MEP system design. Applications of this type offer you a clear view of all the components of the system in real-time, faster calculations (with dynamic checks for every project hypothesis), more precision in design, greater predictive capacity.

With a MEP software, you can design your systems in 3D directly on the architectural model, always have control over the positioning of each element, in addition to preventing interference and problems on-site.