How Window Air Conditioners Work

Window air conditioners are a popular choice among homeowners for cooling small spaces with limited square footage, including converted garages or storage sheds. Whether it’s a home office, a workshop, or a guest room, window AC units offer a convenient and effective way to beat the heat during hot summer months.

A window air conditioning unit is a compact cooling system designed to cool a small space. These units mount on windows or walls and extract warm air from the room, cooling it through a refrigeration process. They then circulate the cold air back into the space. Window air conditioners are affordable ac systems and many are designed for energy efficiency.

In this article, I’ll talk about how window air conditioning units operate, and help you have a better, more confident understanding of this portable cooling system.

Front Panel

From inside the room where the window air conditioner is installed, the user sees the front panel of the window AC unit, which features a user-interfaced control including a thermostat. This ac unit control is either electronic or mechanical. Older window air conditioning units feature mechanical controls, including rotary knobs for adjusting the thermostat temperature and fan speed of the air conditioning system.

Newer window ac units are energy efficient. These ac units are equipped with an electronic control system that allows users to manage functions like the thermostat via remote control or a touch panel featuring a digital display.

The front panel window ac unit has adjustable horizontal and vertical (some models) louvers. The direction of airflow is adjustable to suit the comfort of users.

The window air conditioner panel offers a fresh intake of air, referred to as VENT (ventilation), for users who desire a specific amount of fresh outside air.

Mechanical window air conditioners are usually lower in price compared to electronic window ac units. If you want a cooler room temperature and are not too particular about aesthetics or additional functions, the mechanical window air conditioner is a good choice.

Operations

During operation of a window air conditioner, the unit mounts a thermostat on the return air. This temperature serves to control the on or off function of the compressor. Once the room temperature reaches the desired level, the compressor switches off.

To prevent damage to a portable air conditioner it typically requires at least a 3-minute cooldown period before it can be turned on again. Mechanically controlled ac units usually caution users to wait 3 minutes after shutdown before restarting the ac unit. Electronic control ac units often incorporate a timer to automatically manage compressor cycling.

The evaporator blower fan will suck the indoor air from the room to be conditioned through the air filter and the cooling coil. Room air that has been conditioned is then discharged to deliver the cool and dehumidified air back to the room. This cool air mixes with the room air to bring down the temperature and humidity level of the room.

The introduction of fresh outside air is done through the AC damper which is then mixed with the return air from the room before passing it over the air filter and the cooling coil.

The air filter which is mounted in front of the evaporator on the ac unit acts as a filter to keep the cooling coil clean in order to obtain good heat transfer from the coil. Clogged air filters are one of the reasons window AC units fail. Regular washing and cleaning of the air filter is a good practice to ensure efficient operation of the window air conditioner.

Heat Pump Window Air Conditioner

If you live in a climate that requires a heating system as well as a cooling system, you may want to consider a heat pump window air conditioner. The biggest difference between regular AC and heat pumps is that a heat pump window air conditioner unit is able to cool the room during summer and heat the room during winter. A reversing valve (also known as a 4-Way-Valve) is used to accomplish this.

During the heating operation of a heat pump ac system, it reverses the flow of the refrigerant which results in the evaporator acting as a condenser and the condenser as an evaporator.

Instead of purchasing a window ac unit for cooling and a space heater for heating, window heat pump ac units are much more efficient. These units can effectively warm entire rooms, unlike space heaters which only heat small areas.

How Do You Pick the Right Model AC Unit for Your Home?

The most important thing to consider when selecting a window AC unit is size. The square footage of the room you want to cool is important. One square foot of space will require a window ac unit of 20 BTU’s (British Thermal Units).

Ac units that are too small will be overworked trying to cool the room and won’t make the room temperature comfortable. If the window air conditioner unit is too big, the humidity wont be properly removed and you will have a cool room that still feels sticky.

Homeowners with smaller spaces to cool can truly benefit from a comprehensive understanding of how window AC units function and the suitable type and size to select. Their efficiency in both cooling and heating makes them a practical and effective solution for maintaining comfort throughout the year. Whether it’s a converted garage, home office, or bedroom, I recommend a window AC unit to provide reliable temperature control and comfort. 

Related: What is a Fan Speed Controller?