How Does an Air Conditioner Work? A Guide to the Home Cooling Cycle

How Does an Air Conditioner Work? A Guide to the Home Cooling Cycle
Roger Bakies
Residential Sales Professional

I have been in the residential/light commercial HVAC business for 30 years. I grew up in a sheet metal fabrication shop and have installed, serviced, sold and helped people choose new systems to best fit their needs and lifestyle. I look forward to helping you pick the best fit for your home!

About This Article

Do you know how your air conditioner cools your home? Let’s walk through the home cooling cycle.

Your air conditioner has offered you respite from the heat on hot summer days. But have you ever wondered how an air conditioner works?

Air conditioners rely on a few physical processes to cool your home. But your air conditioner doesn’t actually produce cold air – it removes heat from your home. 

Over the last 30 years, I’ve worked with air conditioners from every possible angle – from installation to service to sales. I know the mechanical steps of the home cooling cycle like the back of my hand. And because each Fire & Ice service technician and installer is required to complete over 200 hours of training, they do too.

But why is this important to a homeowner?

When you know more about how your air conditioner works, you benefit in a few ways:

  1. If your system breaks down, you can better understand why and how it happens.
  2. You’ll be able to choose HVAC partners who follow best practices for installations and maintenance.

In this article, we’ll go over how air conditioners cool your home and more. By the end, you’ll know the major parts and components of an air conditioner as well as the home cooling cycle. We’ll also go over a few other factors that can affect your air conditioner’s performance.

So let’s get started.

An air conditioner.

Parts of an Air Conditioner

Before we dive into the mechanics behind how air conditioners work, let’s discuss the parts that help cool your home.

1.    Refrigerant

Refrigerant is the substance that’s responsible for cooling your home. Refrigerant can easily switch from a liquid to a gas (and vice versa). This ability powers the home cooling cycle (which we’ll discuss later in this article).

2.    Compressor & Compressor Fan

Your system’s compressor is located in your outdoor unit. The compressor is responsible for turning refrigerant into a liquid.

Your system’s compressor fan helps exhaust heat absorbed from your home. This is the fan inside your outdoor unit.

3.    Condenser Coil

Your system’s condenser coil is located in your outdoor unit. The condenser coil works with the compressor to turn refrigerant into a liquid.

4.    Metering Device & Evaporator Coil

Your system’s metering device controls how quickly refrigerant moves into the evaporator coil. This allows the refrigerant to evaporate inside the evaporator coil.

Your system’s metering device and evaporator coil are located inside your home.

If you have a furnace, you’ll likely find your evaporator coil on top of your furnace. If you have an air handler, your evaporator coil is likely located inside your air handler’s cabinet.

5.    Liquid Line

Your air conditioner’s liquid line is copper tubing that connects your indoor and outdoor units. When refrigerant is in liquid form, it travels through the liquid line from your outdoor unit to your indoor unit.

6.    Suction Line

Your air conditioner’s suction line is also copper tubing that connects your indoor and outdoor units. When refrigerant is in gas form, it travels through the suction line from your indoor unit to your outdoor unit.

7.    Condensate Drainage

Your air conditioner helps remove moisture from the air inside your home. The condensate drainage helps drain this moisture from your evaporator coil.

8.    Blower Motor

Your system’s blower motor controls air circulation within your home. This helps distribute conditioned air throughout your home.

Both your heating and cooling systems rely on your blower motor to move air throughout your home. In fact, your blower motor is located within your furnace or air handler. This is one of the reasons your air conditioner must be compatible with your furnace or air handler.

An explanation on how an air conditioner works.

The Home Cooling Cycle

The home cooling cycle begins when temperatures inside your home rise. Then your thermostat signals your air conditioner.

In a liquid state, refrigerant travels through the liquid line to the metering device and evaporator coil in your inside unit.

From here, your air conditioner relies on the same technique that your body uses to cool down: evaporation.

Your metering device and evaporator coil change the refrigerant to a gas. When it evaporates, the refrigerant absorbs heat from your home.

Just like your body uses the evaporation of sweat to cool down, the evaporator coil cools down when the refrigerant evaporates. The blower motor pushes air over the evaporator coil, which cools the air. The conditioned air is distributed throughout your home through your ductwork.

Then, the refrigerant travels through the suction line to the compressor and condenser coil in your outdoor unit. The compressor and condenser coil change the refrigerant back to a liquid.

When it condenses into a liquid, the refrigerant releases the heat that it absorbed from your home. The compressor fan exhausts this heat into the atmosphere.

Then the refrigerant cycles back to the metering device and evaporator coil inside.

Factors that Affect Your Air Conditioner’s Performance

Outside of the home cooling cycle, there are other factors that affect your air conditioner’s performance.

These factors include:

  1. Your air conditioner’s capacity
  2. Your air conditioner’s efficiency
  3. Other HVAC equipment

Your Air Conditioner’s Capacity

In order to adequately cool your home, your air conditioner must be the right capacity for your home. In HVAC, we frequently refer to the capacity of your air conditioner as its “size.”

If your air conditioner is too big or too small for your home, it could cost you comfort and efficiency.

If your air conditioner is too big for your home, it’ll kick on and off more frequently than it should as it struggles not to over-cool your home. This can increase the amount of energy your air conditioner consumes.

In multi-story homes, kicking on and off, or short cycling, also means your upper floors won’t receive the same level of cooling. This also means that your system won’t be able to properly remove humidity from your home.

If your air conditioner is too small for your home, it’ll run more than it should as it attempts to cool your home to the set temperature.

In both cases, incorrect sizing increases the amount of wear and tear on your air conditioner. This can decrease the life expectancy of your air conditioner by as much as 5-10 years.

In order to determine the size of your air conditioner, your HVAC partner must perform a load calculation.

Load calculations account for factors that could create challenges for your air conditioner.

These factors can include:

  • The total square footage your air conditioner must cool
  • The number, size and condition of your home’s windows and doors
  • The direction your windows face
  • The square footage of your walls, ceilings and floors
  • How recently your home was insulated

If your HVAC partner doesn’t perform a load calculation, your air conditioner’s performance will suffer.

Your Air Conditioner’s Efficiency

Manufacturers score an air conditioner’s efficiency with a Seasonal Energy Efficiency Ratio (SEER) rating.

The U.S. Department of Energy requires air conditioners to be a minimum of 13 SEER in northern states and 14 SEER in southern states.

Some air conditioners can get up to 28 SEER. But a high SEER rating isn’t everything.

HVAC contractors generally use SEER ratings to compare energy consumption and estimate savings. And while air conditioners with higher SEER ratings can save you money, they also cost more upfront.

In some cases, higher-SEER air conditioners can pay for themselves over time. But the highest-SEER air conditioners may take longer to pay for themselves.

Of course, air conditioners rated 20 SEER or higher can also offer the most comfort. But if your primary goal is to cut down on energy costs, a 20 SEER air conditioner may be the most efficient, but your home may not need it.

If you’re replacing an older air conditioner, most newer models will be more efficient.

To learn more, check out this article on the factors that make a good SEER rating.

Other HVAC Equipment

Your air conditioner works with other components of your HVAC system. Because of this, your air conditioner must be compatible with other parts of your system, like your furnace and ductwork.

It’s easy to think of your furnace and air conditioner as completely separate systems. But without your furnace, your air conditioner wouldn’t be able to cool your home at all.

Your system’s blower motor is located in your furnace. As I mentioned earlier, your blower motor circulates air throughout your home. If your air conditioner and furnace aren’t compatible, you could lose comfort or efficiency.

It’s also important to make sure that your ductwork is sized correctly. Sizing ductwork is similar to sizing your system – and if ductwork is sized incorrectly, your entire system’s performance can suffer.

Occasionally, an HVAC contractor may need to update your ductwork so it’s compatible with your system. Your HVAC partner should be able to assess whether your ductwork is the correct size for your home and system.

A thermostat, air conditioner, and furnace.

Next Steps

As you continue to explore the intricacies of air conditioners, here are a few articles we think you may appreciate:

At Fire & Ice, we believe that homeowners can make the best decisions for themselves and their homes when they have more information. We commend you for taking that step.

If you live in Central Ohio and you’re looking to replace your air conditioner, we’d love to help!

We offer free in-home estimates, during which we take the time to learn about your comfort needs and preferences.

To take the first step toward your free in-home estimate, enter your zip code below. We look forward to meeting with you!

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