How Does a Window Air Conditioner Work?

It's a hot summer day, and you're relishing in the coolness brought to you by your new window air conditioner. Since relaxing in a comfortable home is very conducive to letting your thoughts wander, you may begin wondering how exactly this miracle of modern living cools things off so quickly and easily.

Remember our article "How Does a Refrigerator Work?" A window AC works in a way very similar to a refrigerator, but instead of an airtight food storage appliance, it's cooling an entire room. The unit pulls warm air out of the room and runs it over cooled coils, which operate thanks to a cycle of expanding and compressing the system's coolant. Here's a step-by-step look at how a window air conditioner cools a room.

Step 1: The temperature in the room rises above the set temperature on the air conditioner's thermostat, causing the unit to switch on.

Step 2: The humming noise you hear soon after it switches on is the system's pump compressing its coolant into a liquid. That's why your AC doesn't start blowing cool air the moment you turn it on  the coolant's pressure needs to build up before it can begin working. Any excess heat created by the compression is blown out the back of the unit.

Step 3: Once enough coolant has been compressed into liquid, it travels through the system until it reaches the expansion valve. This valve only lets a tiny bit of coolant through at a time, slowly releasing its pressure and turning it into an intensely-cooled gas. This cooled gas travels through the unit's cooling coil.

Step 4: Hot air from inside the room gets pulled into the air conditioner by the blower, it passes through the filter to minimize dust, and then passes over the cooling coil. This cools the air and also ends up creating some condensation, which is the dripping water you tend to see falling from the back of the unit.

Step 5: The cooled air passes through a small duct inside the air conditioner and is blown back into the room. The coolant moves back into the pump, where it becomes compressed, and the cycle begins again. These steps continue repeating until the air inside the room reaches the temperature set on the air conditioner's thermostat.

To keep your air conditioner in top working condition, make sure there's a tight seal around the window to keep air leakage to a minimum. Also, don't forget to clean your window AC regularly to keep it in good working order. Enjoy your summer!

Image credit: Wikimedia Commons