How a Central Air Conditioner Works

A central air conditioning unit
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When the heat of spring, summer, and early fall comes rolling in, it's nice to have some cooling system in place in your home to be able to beat the heat. Some people have portable window air conditioners to cool the home, while others have central air conditioners.

Two Different Coils Used to Cool Your Home

Central air conditioners incorporate two different coils to cool your home. This type of cooling system is used to cool the entire home, versus a window air conditioner that is used to cool a specific area or room of your home. The cooling compressor is set outside the home, separate from the fan unit used to blow the cool air throughout the home on the central air unit, unlike the ​window air conditioner that utilizes everything within one concealed unit. By using the existing heating/cooling ducts that encompass the entire home, the central air unit can cool the entire home evenly.

The coil that is placed outside of your home is called the condensing coil. It consists of a compressor, condensing coil condenser fan, a grill to protect persons from coming into contact with the fan blade, a case built around all of the components, controls, and two refrigerant lines that run into the home to the evaporator coil.

The refrigerant inside the compressor is pumped through the evaporator coil inside, which cools the air as the furnace fan blows air through the coil. The coil absorbs the heat from the air. Then the refrigerant flows back outside to the condenser coil, and this is where the heat that was absorbed is released. At this point, the refrigerant (known as freon) is returned to a liquid form as it is cooled and the cycle of refrigerant flow continues.

Regular Maintenance Is Required

To keep the central air conditioner working properly, regular maintenance is required. This includes replacing filters regularly, oiling the fan motor, and keeping the parts clean and free of debris. To oil the motor, you must first turn the power off to the system and remove the fan cage, which holds the fan motor in place. Turn the cage assembly upside down to access the oil ports on the motor.

These ports will be located on the top of the motor, just below the fan blade of the motor. Remove the oil plugs that protect the motor from debris. Each port should be oiled with three drops of all-purpose, three-in-one oil. Spin the fan blade slowly by hand to disperse the oil within the fan. Now, replace the oil plugs and wipe any excess oil that might have spilled. This process should be repeated each season to ensure proper lubrication and long wear for your fan motor. 

Cleaning the Cooling Fans

At least once a year, especially before the season starts, turn off the unit and use a garden hose to clean the cooling fins to remove any dirt, grass clippings, leaves, and other debris from the unit. Hot, dry summer days and windy, sand-blowing winds helped cake the fins of the condenser and lessen the cooling capacity. 

You need to change the filter on your furnace's return air duct often to ensure that good airflow is achieved. A dirty filter will cause low air flow and can cause the unit to freeze up, restricting airflow even more.

One last thing to consider is the furnace's fan that is responsible for blowing the cool air out into your home. It too needs a fair amount of maintenance. The fan needs to be oiled from time to time, just like the outdoor unit.