It's a common myth that the sole purpose of an air conditioning system is to provide cool air. While cooling is the primary purpose of an air conditioning system, reducing humidity is another important one.

To do this, the system must be sized properly because one that is too small will not adequately remove moisture from indoor air. By contrast, an air conditioning system that is too big will cool a home so quickly that the system will shut off the blower before the cool air can circulate fully. This, in turn, can increase indoor humidity levels.

Excess humidity is not only uncomfortable; it can be unhealthy, too. Excess humidity promotes mold, mildew and bacteria growth. And for people who suffer from asthma, allergies and upper respiratory problems, it can make the simple act of breathing very difficult.

Even when a home does cool down properly, it can still feel damp, clammy and even musty if there is too much humidity in the air.

So why can your air conditioning system reduce - but might not be able to eliminate - humidity from the air? Let's start with an overview of how this complex system works.

The ABCs of air conditioning

Ironically, humidity control was what motivated Willis Carrier to develop indoor air conditioning at the turn of the 20th century. Today, the American Society of Heating and Air-Conditioning Engineers provides a straightforward explanation of how his invention works:

“Air conditioners blow cool air into your home by pulling the heat out of that air. The air is cooled by blowing it over a set of cold pipes called an evaporator coil...It is filled with refrigerant, which changes from a liquid to a gas as it absorbs heat from the air. The refrigerant is pumped outside the house to another coil, where it gives up its heat and changes back into a liquid. This outside coil is called the condenser because the refrigerant is condensing from a gas back to a fluid. A pump, called a compressor, is used to move the refrigerant between the two coils and change the pressure of the refrigerant so that all the refrigerant evaporates or condenses in the appropriate coils.”

As household air is drawn over the refrigerant coils in an air conditioner, moisture as well as heat is extracted from the air. The excess moisture, known as condensate, is directed through a condensate drain outside of a home.

Air conditioning is more complex than heating

Much can go awry during this process. First, remember the importance of size; an air conditioning system must be sized to meet the energy load a household will place on it.

The system also must operate with the correct amount of refrigerant. If there is a leak, it will undercut the cooling capacity of the system, as will a reduction in the amount of air that moves across the refrigerant coils. When it's hot and humid outdoors, your air conditioning system might not be able to achieve an optimal indoor relative humidity level of between 45 and 55 percent. And that's before it battles any indoor influences; activities such as cooking and showering can add as much as 25 pounds of moisture to your indoor air every day.

Given all of these circumstances, it's little wonder that the society seeks to lower expectations about the ability of air conditioning systems to dehumidify: It's “incidental to their main job of controlling temperature. They cannot independently control both temperature and humidity.”

Reach for, but don't throw in, the towel

All hope is far from lost, however. Whole-house dehumidifiers and portable consoles are two viable options. Also:

• Do not leave your thermostat set to the “fan” position because it will blow air constantly, including moist air right back into your home before it can drain away.
• Use exhaust fans while cooking and bathing.
• Keep windows closed on days when it's humid outdoors.

If you suspect that other conditions might be contributing to humidity problems in your home, don't hesitate to contact Experts In Your Home. Our Chico air conditioning repair technicians are ready to help you out. Your air conditioning system is inherently more complex than your heating system, but we can remedy any problems to help you breathe dryer, more comfortable air, every day.

Next time you have problems with your air conditioning system, know the right questions to ask a service company by downloading the free eBook below!