Operation of the air conditioning system

The operation of an air conditioning system installation is aimed at cooling and dehumidifying the indoor space of a home or a public building. To achieve this, it uses the vapor compression cycle which consists of circulating a refrigerant material inside the system that significantly increases its temperature when compressed and cools rapidly when it is allowed to expand.

The outside part of an air conditioning system is called a condensing unit and contains the compressor, which consumes most of the energy, and the condensing coil. The internal mechanical equipment, called air control unit, contains the evaporator coil, the internal blower, and the expansion valve or regulator. The controls and ducts through which the cold air circulates complete the system.

Air conditioning system. Vapor compression cycle

The vapor compression cycle consists of four steps:

1. The compressor (located in the outdoor unit) pressurizes a gaseous refrigerant. The refrigerant heats up during this process.
2. The fans in the outdoor unit draw air through the hot pressurized gas to the condensing coil; the refrigerant gas cools and condenses into a liquid.
3. The pressurized liquid is transported through tubes to the air control unit. It enters an expansion or regulating valve, where it expands and cools.
4. The cold liquid circulates through the evaporator coils. The cooled air is filtered through the ductwork. The refrigerant, which is now a gas, returns to the outdoor unit where the process repeats.

Ventilation and indoor air quality

Adequate conditioning of the indoor environment of a home through an air conditioning system that cools the rooms in summer must be accompanied by a ventilation system that guarantees health conditions and indoor air quality all year round. These systems must renew the contaminated air and also reduce excessive humidity levels. Therefore, the construction of inefficient homes that allow air leakage should be avoided, and instead, the installation of hybrid or mechanical ventilation systems should be promoted as required by the Technical Building Code. DB-HS3.

This requirement is due to the fact that in older buildings, ventilation occurs through natural ventilation and air leakage. However, these leaks are not a controllable source of the amount of renewed air. For example, air leakage is greater during cold and windy periods and tends to be quite low during hot periods.

With mechanical ventilation systems, contaminated air can be extracted from humid areas (kitchen, bathrooms, and toilets) and clean, filtered air introduced into dry areas: living rooms and bedrooms. These systems also help dilute the contaminating elements that are routinely produced inside a home, such as humidity, CO2 produced by people's metabolism during their activities, as well as other elements suspended by construction materials, furniture, or the finishes of the home.

Moreover, the installation of a mechanical ventilation system that incorporates fans with heat recovery has advantages: this system retains heat in the indoor environment in winter and cools it in summer. To achieve this, heat exchangers recover 92% of the extracted air so that the air is introduced into the interior of the house at 19 °C when there is a 15 °C temperature gradient between the outside and the inside. In summer, air is introduced at 22 °C when the outside temperature is 30 °C and the indoor temperature is 21 °C.