The cooling process in air conditioning has more to it than most people realize. For example, did you know that air conditioners don’t actually cool the air?

Maybe you’re nodding your head yes, in which case you’re ahead of most homeowners. But HVAC can be complicated, and it’s no one’s fault that you don’t have time in the day to study things like airflow dynamics and refrigerant properties.

This article breaks down the air conditioning process into easily understood terms. The goal is twofold:

Give you a basic understanding of a major appliance in your home that affects your comfort.
Give you some knowledge that can help you as you choose an HVAC contractor to work with.

Let’s get moving, starting with the different types of air conditioners. They all work similarly in many respects, but not identically.

Types of Air Conditioners

You’re probably thinking about a specific type of air conditioner when you imagine one, and you’re not wrong. But there are several types. Common ones are covered below.

Split AC Systems

This is your basic home system that’s linked to ductwork and is usually located in a closet or basement.

The “split” refers to the fact that there’s an indoor and outdoor unit that are linked to one another. The indoor unit collects heat and humidity and it’s transferred and expelled outside via several mechanical processes, before being recirculated in the home.

It’s this type of system that we’ll discuss in more detail below.

Ductless Mini-Split Air Conditioners

Ductless units are often called “capsule” air conditioners, and usually sit in a finished basement, livable attic, guest bedroom, or other room that’s hard to cool or which doesn’t have ductwork running to it from a central air split system.

Ductless mini-splits often also heat as well, making them an all-in-one heating and cooling unit. But they’re typically more well-known for their cooling capabilities.

They run to an outdoor unit that mirrors a split system, but they are standalone and unconnected to ductwork.

Window Air Conditioners

The noisier, less efficient version of the options above, window ACs can still provide a lot of cooling power and can be a more initially affordable option to cool a problem area like a bedroom or attic.

Cassette Air Conditioners

Cassette air conditioners operate similarly to ductless systems, but they typically emit cool air from the ceiling and are installed there. They can offer efficient comfort in a room or small area without taking up a lot of indoor space.

Commercial Systems

Commercial systems are often much more powerful than residential air conditioners, and the air usually runs on a closed-loop system that circulates air through the building. Larger commercial units will in fact be numerous air conditioners, not one.

Basics of the Cooling Process

The key to the cooling process is in the circulation of air and how refrigerant absorbs or emits moisture and heat. It’s this transfer that drives the entire process.

Refrigerants can shift back and forth between gaseous and liquid states, and it’s the air conditioner’s job to facilitate this state transfer. The refrigerant’s properties in these two states are what allow it to cool the air.

When refrigerant is inside the evaporator coil inside, it’s in its gas state. In this state, it’s able to absorb heat from the air around it, which in this case is air that’s been collected by the HVAC system and circulated throughout the ductwork’s return vents. Heat is absorbed by the refrigerant and it travels back to the outdoor unit.

Here the unit’s compressor shifts it back into a liquid state and it loses the ability to store the heat it absorbed. This is expelled by the outdoor unit.

So rather than adding cool air, the air conditioning process is more about removing warm air. With this heat removed, the air is recirculated throughout the home via the ductwork and you experience it as cooling, conditioned air.

This cycle is repeated until your home is the temperature set on your thermostat.

Parts in a Central Air Home Air Conditioner

Knowing the parts involved can point you to problem areas, and also give you a checklist for whenever an HVAC mechanic repairs or performs maintenance on your air conditioner.

This is not a complete parts list, but covers several major parts and subsystems in your air conditioning system.

Blower Motor. This powers the system’s fan and moves air through the system. Without this, warm air from the home wouldn’t travel over the evaporator coil.
Compressor. The compressor is the key to compressing (surprise surprise!) the refrigerant so that it changes states.
Condensate Drain. Air conditioners remove moisture from the air, since humidity is largely equivalent to warmth. This excess moisture has to go somewhere, and the condensate drain line removes it from the system.
Condenser Coil. The compressor and condenser coil work in tandem to shift refrigerant from gas to liquid in your outdoor AC unit.
Evaporator Coil. This converts refrigerant into gas, allowing it to absorb heat from the air around it.
Filter. Your filter is sometimes called a “furnace filter” but it really shouldn’t be, because it’s crucial to ensuring smooth airflow and clean air any time your run your HVAC system.
Liquid and Electrical Lines. Lines need to be run between indoor and outdoor equipment, and both the refrigerant and electrical lines need to be properly protected and insulated to be safe and efficient.
Refrigerant. The lifeblood of the unit. If your AC has a leak, refrigerant can escape in its gaseous state and your air conditioner can lose its ability to cool.

Staging in Air Conditioners

Staging is an important aspect of cooling, and it can vary a lot between air conditioners.

Think of stages like shifting gears in a car. Except it is a bit inverted, because the “default” gear is the highest setting.

So an air conditioner with only one gear (this is most ACs) will operate at 100% power at all times when it’s running.

However, it might be more efficient – and often is – when you can shift between, say, 40%, 60%, 80% and 100% depending on the cooling needs of the home.

The most cutting-edge air conditioners have hundreds of stages. They can tune your home to within half a degree of temperature, and are shifting stages frequently to maintain the best cooling balance while also maintaining cost efficiency.

ADDITIONAL INFORMATION: One-Stage, Two-Stage and Variable Speed Air Conditioners

Capacity of an Air Conditioner

The capacity of an air conditioner is often referred to as its “size” or power. Size can refer to physical size, but more so it’s referring to an air conditioner’s capacity for moving air through your home.

For example, what changes between homes that are 1,000 square feet vs. 5,000 square feet. A lot.

The air conditioner has to treat a lot more air before the entire home will be cool, and it’s also having to move that air through a much larger space.

Home size isn’t the only thing that affects the need for more cooling power, but it’s an easy one to use as an example.

So the capacity – the amount of air a system can efficiently cool – has to go up to keep up with this increase.

Capacity is measured in tonnage, which is a calculation of the British Thermal Units (BTUs) that can be processed by a system. Systems generally start at 2-ton and go up to 5-ton. Anything larger than that (say, for enormous homes or businesses) and you’ll probably need multiple cooling units installed to properly cool the entire space.

The process remains the same, but the upper limits change on the workload an AC system is capable of.

Other HVAC Systems That Affect the Cooling Process

You probably don’t think about your thermostat as being part of your air conditioner. Or your ductwork. But maybe you should.

Of course, these items are specific to your cooling system. However, if they’re not working properly, your entire HVAC system will suffer.

That’s why when we think about air conditioning, we’re not only thinking about the AC unit itself. Other items that contribute to your cooling include the following:

Blower Motor and Fan. This circulates the air regardless of whether you’re heating, cooling, or just circulating air throughout your home.
Ductwork. Leaky or poorly insulated ductwork can result in terrible cooling efficiency. Improperly sized ductwork can also lead to airflow backups in the system and rooms that never get as cool as you’d like them to.
Thermostat. This is the “brain” of your entire system and controls cooling output and often other factors such as humidity level.
Windows and Attic Insulation. If these are poor quality, your air conditioner will have to work harder and will struggle to keep the home cool. AC upgrades are the best way to improve cooling efficiency, but other upgrades to your home can assist in this efficiency.

This is not a comprehensive list, but gives you a sense of how home cooling goes beyond just the air conditioning process itself.

Choosing the Best Air Conditioner

Understanding how an air conditioner works isn’t just about curiosity. It can help you as a homeowner in better understanding what can go wrong, what the fix will look like, and it can help you spot “snake oil” contractors who try to sell you services you don’t need and are hoping you don’t understand enough about HVAC to question them.

Knowledge is power, and when an HVAC system can easily cost over $10,000 in even smaller homes, it pays to understand yours.

If you’re interested in learning more about your home HVAC system, how it might be improved, or are looking for quotes on any type of HVAC service, we hope you’ll consider CABS and look forward to speaking with you!

How Does an Air Conditioner Work? The Science Behind Home AC