How Air Conditioning Works

It might seem like magic. After all, how could your air conditioner blow cold, chilled air throughout your house even when it’s 100℉ outside? Are you wondering how air conditioning works? The real answer might be a little complex, but it certainly isn’t magic—it’s science!

In today’s blog post, the HVAC experts at Air Works Heating & Air explain how your home’s central AC system creates cool air on a hot summer day. We’ll cover the various aspects of the refrigeration cycle, explain what each piece of the equipment is doing, and shed some light on an interesting piece of engineering that many people take for granted.

The Parts of Your Central AC System

To understand how air conditioning works, first you need to know about the major parts and equipment these systems use.

  • The Condenser Unit (Outside): Possibly the largest, loudest, most visible part of your home’s air conditioner, the condenser unit is the vented box with the large fan that’s most often located outdoors in your home’s yard. Inside the condenser unit, there’s a large motor-driven fan, an electric compressor, a big condenser coil that’s similar to your car’s radiator, and electrical switching systems to control everything. The condenser is where the excess heat from inside your home is blown out into the outside air to cool your home.
  • The Blower Unit (Inside): The part of your central AC system that’s inside your home, often located in a closet or in the attic, is the blower unit. These consist of a powerful fan, the blower, that blows warm air from inside your home across a cold evaporator coil to chill it before forcing it into your ductwork and out into the rooms of your home. The blower unit will also have an air filter built into it that needs regular changing to keep your air-conditioned air clean and ensure proper airflow in the system.
  • Refrigerant Lines (Inside & Outside): Refrigerant, a specialized substance that gains and loses heat very efficiently, is carried between your AC’s condenser unit outside and the blower unit inside via your refrigerant lines. These are usually small pipes with a diameter of one inch or less. They’re also often insulated because they carry warm refrigerant out to the condenser unit and cool refrigerant back inside.
  • Ductwork & Vents (Inside): Your air conditioner is connected to ductwork and vents that route your air-conditioned air throughout your home, where it is blown through vents into each room.
  • Thermostat (Inside): The thermostat is the wall-mounted control panel inside your home that allows you to control your HVAC system. Your thermostat can switch between air conditioning and heating, allow you to run your blower fan only, and set a desired inside air temperature. Most modern thermostats can even be programmed to change temperatures on a set schedule, which can be a great money-saving strategy.

Understanding the Refrigeration Cycle

The refrigeration cycle is the science behind your home’s central air conditioning system. Possibly the most common misconception with air conditioning is that it “adds cold” to the inside of your home. Not true! Heat is what’s exchanged, not cold. This means that air conditioning “removes hot” by transferring the excess heat from your inside air out to be released into the outside air. Exactly how this process works is a little technical, but it can be explained using fairly simple terms.

Let’s explore the four main stages of the refrigeration cycle. Please note that the order listed below is not important, because the cycle is continuous rather than having a distinct start or end. It’s also important to note that this is a slightly simplified explanation that touches on the main points and leaves out some of the details.

1. Vapor, Low Temperature, Low Pressure

As your air conditioner’s refrigerant flows away from the blower unit (evaporator) and outside toward your condenser unit, it was just used to chill the hot air inside your house. That means it’s carrying the excess heat you’re trying to remove from your home. At this point, the refrigerant is a vapor (gas) at relatively low temperature and low pressure.

2. Vapor, High Temperature, High Pressure

Once the refrigerant enters your outdoor condenser unit, it runs into a powerful electric compressor that forces pressure into the vapor. That squeezing compressive force causes the temperature of the refrigerant to increase substantially, far higher than the outside air even on the hottest summer day. The high-temperature, high-pressure vapor then enters the condenser coil, which works much like your car’s radiator. A fan blows ambient outside air through the condenser coil, releasing all that excess heat into the air and away from your home.

3. Liquid, High Temperature, High Pressure

After releasing its excess heat in the condenser, the refrigerant becomes a high-pressure, high-temperature liquid. This liquid is pumped back into your home and toward an expansion valve, which removes the pressure and causes the liquid refrigerant’s temperature to plummet.

4. Liquid, Low Temperature, Low Pressure

After the expansion valve, the low-temperature, low-pressure liquid refrigerant is forced into your blower unit, where it enters the evaporator coil and converts to an ultra-cold vapor as it expands. The blower fan then forces warm inside air through the evaporator coil, where the ultra-cold vaporized refrigerant chills it, and the cycle starts again.

Summing it All Up

In basic terms, your home’s air conditioner forces the excess heat inside your house into a refrigerant that carries this heat outside and releases it into the outside air. The science of matter as it changes phases between a liquid and a gas, known as Boyle’s Law, makes it all possible. It enables us to keep the refrigerant cold enough inside to pick up excess indoor heat (chilling your air) and then getting the refrigerant hot enough to release that heat into the hot outside air.

If the process is still mysterious to you, don’t worry! The experts at Air Works Heating & Air have all the knowledge, training, and experience needed to inspect, maintain, and repair your air conditioning no matter what the issue. We have you covered! Just call us at (919) 551-3514 or contact us today if you have any questions or need your HVAC system serviced.