The air conditioners in homes, offices, cars and other vehicles, shopping centers, schools, hospitals, and all large or small indoor areas, keep us cool in the summer and warm in the winter. Even though they have become such common in our daily lives, air conditioning users do not know how do air conditioners work and the principle of operation of air conditioner

In this article, we will share details about the principle of operation of air conditioner, which is essential for a comfortable life, and try to answer the question ‘How do air conditioners work?’

What Is an Air Conditioner?

Invented by Willis Carrier in 1902, the first modern air conditioner is a system that provides artificial air conditioning indoors. Air conditioners provide a comfortable living space by allowing indoor areas to cool or heat up, adjusting humidity levels in the environment, and filtering the particles and dust.

Air conditioners are used in a wide range of indoor environments, from narrow and small spaces like automobiles to massive structures like factories or airports, to provide a comfortable ambient temperature. Today, air conditioners are preferred not only for ambient temperature control but also for a healthy atmosphere.

How Do Air Conditioners Work?

The operation of air conditioning is based on the second of the four fundamental laws of thermodynamics. According to this law, heat always flows from hot (high energy) to cold (low energy). The air conditioner’s primary function is to cool or heat up the indoor air. A special chemical liquid known as R22/R410 is used for this. Evaporation and condensation of this liquid reveal heating and cooling actions. In other words, the continuous movement of the refrigerant from hot to cold allows the desired ambient temperature to be obtained. The air conditioner’s main components ensure that this process proceeds in the correct order.

In order to understand the principle of operation of air conditioner, it is necessary to first know the components of the air conditioner. The following are the main parts of an air conditioner:

Evaporator: Converts refrigerant fluid into a gas, allowing the gas to absorb heat from the environment.

Condenser: Releases the heat absorbed by the refrigerant gas in high pressure and heat, allows it to condense, and thus converts it into liquid.

Expansion valve: Reduces the pressure of the refrigerant that is moving to the evaporator to the level of evaporation.

Compressor: Sends the low-pressure refrigerant from the evaporator to the condenser at high pressure. In short, the compressor acts as a pump that pressurizes the refrigerant fluid.

How Do Air Conditioners Cool Air?

When the air conditioners were first invented, they were not intended for heating purposes. In other words, the main principle of operation of air conditioner is completely based on the cooling cycle. The heating function was later developed based on the cooling process described below:

  • The refrigerant that evaporates in the evaporator absorbs the heat in the environment. As a result, the temperature in the environment decreases. This happens in the air conditioner’s indoor unit.
  • Hot steam is transferred to the condenser by the compressor.
  • The refrigerant releases the heat in the condenser and condenses, that is to say, it becomes liquid. This happens in the air conditioner’s outdoor unit. This is why the outdoor unit blows hot air during cooling.
  • The refrigerant that becomes fluid progresses from the condenser to the expansion valve. The expansion valve reduces the pressure of the fluid and prepares it for evaporation in the evaporator. 
  • The refrigerant moves to the evaporator and the cycle is repeated. As a result, the heat in the indoor environment is constantly expelled and cooling is maintained.

How Do Air Conditioners Heat?

The heating function of the air conditioners depends on whether they have a heat pump. Without a heat pump, air conditioners only provide cooling. The task of the heat pump is to change the direction of the refrigerant according to the purpose of the use of the air conditioner. Heating in air conditioners is based on evaporating and condensing the air conditioning fluid, as in cooling.

  • The compressor transfers the gaseous refrigerant it pressurized to the evaporator instead of the condenser. 
  • In the evaporator located in the indoor unit, the evaporating refrigerant releases the hot air it absorbs from the outside. Thus, as the temperature rises in the environment, the temperature of the refrigerant decreases. 
  • The fluid moves from a different pipeline to the condenser as it loses its heat and condensed because it cannot pass through the expansion valve in liquid form.
  • The refrigerant that enters the condenser in liquid form evaporates by absorbing the heat in the outdoor environment. Therefore, the colder the air outside, the more difficult it is for the air conditioner to perform its heating function. 
  • The evaporating fluid is then transferred to the compressor for pressure adjustment, and the cycle is repeated. This allows for continuous hot air transfer from the outside to the inside.

Air Conditioner Automation

A smart air conditioner is a kind of AC that is integrated into smart home systems and can be controlled remotely via phone, computer, tablet, or smart control. They are similar to standard air conditioners in terms of appearance and installing methods. An AC must have both a standard air conditioning system and Wi-Fi access in order to be considered as a smart air conditioner.

Air conditioner automation is usually provided with the support of a KNX gateway. The fact that smart air conditioners are rare and expensive makes automation with KNX gateway technology far more advantageous. The KNX gateway allows technological products to be integrated into smart home systems.

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How to Save Energy on Air Conditioners?

There are some essential points to consider to save energy when both using and purchasing the air conditioner.

Energy Efficiency Rating

The most important factor to consider when purchasing an air conditioner is its energy efficiency rating. Air conditioners with a high energy efficiency rating are both environmentally friendly and more cost-effective in the long run due to lower energy consumption.

Energy efficiency ratings are sorted from A to G. Class A represents the highest energy efficiency and ecological sensitivity, while class G is considered as the lowest efficiency. Classifications that were previously as ‘A+++’ are no longer valid. According to the new classification provisions, the number of technological products that can be included in class A is extremely limited. This includes air conditioning and cooling technology products. Class A is designed for the development of energy efficiency and environmentally friendly approaches in the future.

The most energy-efficient air conditioners, which used to be classified as class A, are now included in class B. That is why it is recommended to purchase a class B air conditioner for higher energy efficiency at the present time.


Installation of air conditioning is critical for the efficient operation of the air conditioner. The air conditioner should be installed at the point where the airflow in the environment is as efficient as possible, the air released outside should not have a narrow space. This ensures an even distribution of ideal ambient temperature and the air conditioner and the air conditioner consumes less energy to maintain the current heat when it receives the correct heat data from the thermostat.


Heat insulation prevents heat loss in the environment where the air conditioner is used. Since the ideal heat provided in the environment should be maintained for an extended period of time, the air conditioner consumes less energy to maintain the desired degree.

In addition, it is important to keep the windows and doors closed while the air conditioning is running to save energy. Otherwise, cold air comes out, causing the air conditioner to both works inefficiently and expends more energy in order to provide the ideal heat.


Regular maintenance of the AC should be done periodically in order for the air conditioner to operate efficiently. If the recommended maintenance, such as engine maintenance, filter cleaning, and gas exchange is done at least twice a year, the air conditioner functions efficiently for a long time. Since there is a possibility of exposure to toxic chemicals during air conditioning maintenance, maintenance should be carried out by professional service personnel with extensive technical knowledge about the principle of operation of air conditioner.