Air conditioning is a godsend in the summertime, helping us enjoy some cool air away from the heat which dominates the time from June through to late September. How an AC unit works however is unexpectedly a little different. Instead of focusing on making a space cooler, air conditioning works by transferring heat. As heat is lost and removed, only the cold air is left to fill the home. Here are a few things to remember about how an AC unit works:

1. The chemicals

The chemicals used in an AC unit are used to convert from gas to liquid and then from liquid to gas back again quickly. The two main chemicals in an AC unit are refrigerants known as R-22 as well as R-410A. Both are hydrochlorofluorocarbons, or HCFCs.

2. Indoor units

Indoor AC units are typically found in a closet, basement, or near your furnace. These units have a coil box with what’s called an evaporator inside. The evaporator allows refrigerant to evaporate and absorb heat. Refrigerant is a cooling fluid inside the coil piping, sometimes referred to by its brand name, Freon. Once heat is absorbed in an indoor air conditioning unit, the cold air remaining is what blows out back into the home.

3. Outdoor units

An outdoor AC unit will use a compressor, condenser oil, and fan. Heat is absorbed from the home’s air and is transferred to the refrigerant. It is then pumped into the outdoor unit. As heat moves to the outdoor coil, it passes through a compressor which has the primary job of moving refrigerant through the system. Refrigerant, in this way, can be reused again and again. At this stage, refrigerant is compressed to a higher pressure, moved through the condenser, and a fan then delivers ambient air across the condenser coil resulting in it cooling. This means the hot air from inside the house is then dispersed outside and only the refrigerant-touched air is pumped back indoors.

4. AC works similar to a fridge

An AC unit and a refrigerator are very close in how they operate. The big difference though is a refrigerator’s cooling a much smaller and insulated space. An air conditioner has to work harder to keep a larger space at a comfortable temperature.

5. Moisture

An AC unit does not work purely to remove heat but also conditions the air and can help control humidity. Air conditioning units will dehumidify the air, albeit unintentionally. As air moves across the evaporator coil, the coil absorbs heat and at the same time eliminates moisture. The air pushed out ends up being a cooler temperature and drier. Although inside a home or place of business there can be a lot of moisture, what’s getting pushed out is cold, dry air which helps to balance out the climate.

6. The original purpose

When air conditioners were first invented, it was to address humidity. Today’s AC units can be traced back to a design from the early 1900s by New York engineer Willis Carrier who came up with a method to remove humidity from the air at his printing company. The cooling aspect of Carrier’s air conditioning was just a by-product or at least, that’s what he thought of at the time. By the 1930s and 1940s, rich homes in the United States were installing AC units as they were commercialized. By the 1960s, middle-class homes began to be able to afford them. Today, obviously, you’d be hard-pressed to find a home that doesn’t have some aspect of air conditioning. How today’s AC units work are the same as to how they worked 100 years ago.

7. To keep products safe

AC units are so inexpensive today that they are used liberally for many different purposes. Computer servers, power amplifiers, and similar high-use electronics need to ensure they are kept at a comfortable temperature and so, AC units are commonly used for this purpose. Secondly, regarding the storage of delicate items such as artworks which could melt, air conditioning is applied in this case as well. AC units are built into cars and mobile transportation units, industrial environments and warehouses, and healthcare facilities where temperature is key.

8. Another type of AC unit

Outside of the air conditioning unit type we’ve discussed and how AC units work, there are also free cooling AC units. These use pumps to circulate an external coolant – such as air, water, or a cold water-glycol mixture – to remove heat. Some systems utilize storage capacities varying in size and some AC units are hybrid systems, employing free cooling in the early summer and then employing a heat pump later on to chill the circulation coming from the storage. Free cooling systems are generally highly efficient and sometimes combined with seasonal thermal energy storage (STES) which allow for the cold of winter to be repurposed as summer air conditioning.

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