It’s sweltering outside. You enter your house and press a button. Instantly you feel cooler. Magic? No way. Air conditioners operate on very scientific principles. Once you know how an AC works, you will never perceive your cooling system the same way again.
Air conditioners don’t make cold air
When you think about how air conditioners work, start here. Most people think an air conditioner produces cold air. Not so. Your AC doesn’t create a cold at all. It moves heat from the inside of your house to the outdoors.
An air conditioner takes warm air from inside your room and transports heat from that air to the outside. What remains feels cool and refreshing. Knowing this lets you unravel the mystery of your AC.
Remember how a can of compressed air gets cold when you spray it? That’s because the gas inside is expanding rapidly, absorbing heat from the metal can. An air conditioner operates on nearly the same principle. The process just happens on a larger scale.
The Four Components of an Air Conditioner
There are four major components to any air conditioner. The parts work together to carry heat from inside your house to the outdoors.
The evaporator coil is inside your house. Warm air releases its heat to this coil. A fan blows your room’s air over the evaporator coils. Because these coils are cold, they suck heat out of the air. This air blows back into the room cooler than before.
The compressor’s motor is usually in the outdoor unit. The compressor squeezes refrigerant gas. When you compress a gas, you heat it up. Think about when you pump up a bike tire. The compressor forces refrigerant through the entire system.
The condenser coil is usually located outside as well. After the compressor heats up the refrigerant gas, it flows through the condenser coils. A large fan blows outdoor air over the condenser coil. Heat from the refrigerant flows into the outdoor air and is dispersed. That’s why you feel hot air blowing from the back or side of your AC unit.
The expansion valve connects the condenser and evaporator. Just as its name implies, the valve reduces pressure on the refrigerant before it enters the evaporator coil. When pressure decreases, the temperature plummets. When this happens quickly enough, the refrigerant liquefies. From here, it flows back into the evaporator coil and begins the process anew.
The refrigerant does all the work
Let’s take a closer look at the ingredient that does all the heavy lifting. It’s the refrigerant (remember, not creating cold, just moving heat). Refrigerant flows through all four components of your AC. As it travels through the system, it switches between liquid and gas forms. This transformation is what allows it to absorb heat from inside your house and release it outside.
Keep in mind that if liquid refrigerant experiences a loss in pressure, it becomes a gas. When that happens, it absorbs heat from the surrounding air. This is what makes the evaporator coil cold. Once the compressor compresses the gas again, it becomes hot. The condenser coil releases that heat outside. When the refrigerant loses that heat, it turns back into a liquid. Then it travels back through the expansion valve until it starts the cycle over again.
Refrigerants used in modern air conditioners include R-410A and newer units use R-32. If your AC is older, it probably uses R-22. That particular refrigerant was banned because it damaged the ozone layer.
An Easy Step-by-Step Guide
Now it’s time to put all the pieces together. Here’s how an air conditioner works step-by-step:
- Air from your room enters the AC system through a vent.
- This air flows over the cold evaporator coil. Heat from this air transfers to the coil.
- Refrigerant within the coil absorbs heat. When this happens, it turns from liquid to gas.
- This gas travels to the compressor. There it gets compressed (pushed together) and heated.
- The hot gas goes to the condenser coil located outside your home. A fan blows outdoor air over the coil.
- Heat transfers from the refrigerant to the outdoor air and dissipates outside. Refrigerant returns to liquid form.
- Liquid refrigerant travels through the expansion valve where it experiences a loss of pressure. As it does this, the refrigerant becomes cold.
- Cold refrigerant makes its way back to the evaporator coil and starts the cycle over.
Your thermostat controls how often the cycle repeats. Once your room reaches the desired temperature setting, your thermostat tells the system to stop. Then, when your space heats up again, it kicks right back on.
Tip: Did you know your AC removes humidity as well? Warm air transfers its moisture to the evaporator coil along with its heat. The moisture collects on the coil like dew on a blade of grass. It drips into a drain pan and flows out of your house through a drain line. Less humidity in your air equals a cooler, more comfortable room.
How do portable air conditioners work?
Not Every AC Unit Looks The Same
You know how the basic process works. Now it’s time to learn how different types of AC units apply that process.
- Central AC units push cooled air through your home through ducts.
- Window units are self-contained boxes. They cool a single room at a time through your window.
- Ductless mini-split systems don’t use ducts. They have an indoor unit on your wall and an outdoor unit, just like central air. Ductless systems are great for homes without existing ductwork.
- Portable air conditioners rest on the floor. They vent the hot air through a hose that you can run out of a window.
You may have to buy a specific type of air conditioner to match the needs of your living space. But once you get it, you can use your newfound knowledge to figure out how it works.
Case Study: Learn How AC Works and Solve Cooling Issues
A homeowner was frustrated because their air conditioner was cycling on and never seemed to reach the desired temperature inside. They figured their AC wasn’t working properly and thought they would need to buy a new unit.
THE PROBLEM
It felt like their air conditioner wasn’t efficient enough, particularly on hotter days. Cooling took longer, and their energy bills continued to rise. They thought their AC “wasn’t putting out enough cold air.”
THE SOLUTION
The homeowner called an HVAC technician and discovered how AC units really work. Air conditioners don’t produce cold air; they remove heat from the air. The problem wasn’t that their system wasn’t producing cold air. It had restricted airflow and a buildup was blocking the outdoor condenser coils.
Understanding how their AC worked led them to a couple easy solutions:
- Changed their dirty air filter
- Cleaned up debris around the outdoor unit
- Checked for closed vents
THE RESULTS
Not only did these steps make a difference almost immediately, but they kept lasting effects:
- Cooling their home took much less time.
- The air conditioner didn’t have to work as hard.
- Electric bills were lower each month.
- Temperatures in their home were more consistent
MORAL OF THE STORY: When you understand how air conditioners work, you can troubleshoot issues more efficiently. AC units rarely stop working. If you’re experiencing poor performance, look for airflow restrictions or issues with heat transfer instead of faulty equipment. See more.
FAQs
How do AC units cool the air?
Air conditioners cool air by removing heat and humidity from the air in your home and expelling it outside.
Does my AC system have refrigerants?
Yes! That’s how heat transfer happens inside your air conditioner. Refrigerant absorbs heat and rids your home of it by changing from a liquid to gas.
What parts does an air conditioner use to do this?
There are four parts that play key roles in an air conditioner: evaporator coil, compressor, condenser coil, and expansion valve.
How does AC remove humidity from the air?
Warm air holds moisture. As air cools over the evaporator coil, moisture is extracted from the air and drained out of your home.
Do portable air conditioners work the same way?
Yes! Just like a traditional air conditioner, portable air conditioners vent the hot air through a hose. Typically, this hose is vented through a window.
