Proper Maintenance for the Forced-Air Central Cooling System in the Fight Against Mold

Protect Your Home

In an article, titled The HVAC System and Mold Prevention, a brief overview of the function of the HVAC system as a whole and in collaboration with the homeowner’s preventative measures against mold were discussed. While many of the same concepts will be covered here, the purpose of this article is to equip the homeowner with knowledge concerning the maintenance of the forced-air central cooling system so as to shield the home even further from mold infestation.

How the Forced-Air Central Cooling System Works

The main part of the central cooling system is found outside the home in a cabinet that contains a condenser coil, compressor, and an indoor evaporator coil. The central cooling system (CCS) doesn’t actually “produce” cool air like the central heating system’s (CHS) furnace directly produces heat. Instead, the CCS’s compressor pumps a chemical coolant commonly referred to as “refrigerant” through the system, which absorbs the heat of the house and carries it outdoors to be released.
As the CCS is running, its compressor draws cold, low-pressure liquid refrigerant through the tubing in the evaporator coil. The evaporator coil is found within or close to the air handler, which is where the blower fan is located. In some cases, the blower fan of the central heating system (CHS) is used for this process in conjunction with the CCS, which is an example of how these split systems are matched.
Before the refrigerant can pass through the evaporator coil, it must travel through the expansion valve, which relieves pressure from the chemical coolant, rapidly cooling it in the process. As the refrigerant continues along its flow, the blower fan draws hot air from the home over the evaporator coil. The refrigerant absorbs that heat and, as a consequence, it warms up and evaporates.
The water vapor formed from that portion of the CCS meets the cold evaporator coils and condenses into liquid form. It then drips down into the condensate pan, which drains the water outside. This is how the central cooling system’s evaporator coil can reduce the humidity in your home and the risk of developing mold.
Without the condenser coil, however, the evaporator coil would be useless in the struggle to cool your home. The condenser coil’s purpose begins with the copper tubing that leads the already-heated refrigerant to the outside condenser unit. Here is where the low-pressure, warm coolant gas enters the compressor, which then pressurizes the refrigerant and turns it into a hot, high-pressure gas. This same gas exits the compressor and flows into the condenser coils. Most of the heat from your home is released from the refrigerant at this particular point before it returns to the expansion valve and the central cooling operation begins again.

How to Maintain the “Health” of the Central Cooling System So It Can Maintain Your Health

The “life” of the central cooling system relies heavily on its main elements. For example, without the full functionality of the evaporator and condenser coils, the entire system would run inefficiently and, over time, stop working altogether.
It’s important to properly monitor and maintain the various features of the CCS to ensure it has a long, prosperous, mold-preventing career. Listed below are the most essential components—as well as those that are easily accessible to the homeowner—and their individual upkeep needs:

Filter

The filter was designed to trap dust, hair, and lint—not microscopic mold spores. If the filter is not regularly replaced, there could accumulate enough debris to block the filter and catch mold spores. Since most of the debris probably originated from decomposing organic material (dust from human skin cells, hair, and even lint from plant- or animal-based fabrics), the mold will have no trouble finding plenty of nutrients to jumpstart its growth.
In addition, poor air supply due to a dirty filter could result in frost or ice build-up on the evaporator coils and condenser coils, which will impair heat absorption and heat release. This will cause the entire system to be overly taxed, resulting in unstable levels of pressure and temperature.

Registers or Vents

If the intake and outtake floor, ceiling, or wall vents are not free from obstruction, they will cause the same issues for the CCS as a dirty filter would.

Ducts

Any blockage in the ductwork of a home will result in poor air flow, which causes the system to use more energy, and eventually, impairs and damages the main components if the air flow isn’t reestablished. (Parents take note: Even if your vents are secured in place, children tend to find a way to pass items through the vents and into the ducts. Pet owners should also be aware that their pet’s hair and dander builds up over time—regardless of sweeping, vacuuming, and replacing the CCS air filter frequently—and travels through the floor vents and piling into the ducts.)

Outdoor Cabinet/Box/Unit

The exterior unit is often referred to as the cabinet or air-conditioning box. This is where the process begins, but most importantly, this is where the heat—that the refrigerant has absorbed from the house—is released into the outdoor air, which cools the refrigerant and prepares it to cycle through the process again. The box must be kept free of outside debris, such as dirt, leaves, snow, ice, etc. to avoid poor air flow and unneeded insulation of the components inside, such as the coils. Some homeowners make the mistake of covering their exterior unit with plastic during the winter, thinking that it is protecting their box from snow and other debris, but this only provides an insulation that encourages rust by trapping excessive moisture inside. Various animals will also find the unnecessary plastic wrap to be a most welcome shelter during the cold seasons, causing further issues.
During the colder seasons—when the CCS won’t be in use—the best way to provide protection against the winter elements is to cover the top of the exterior unit with a wooden board and secure it in place with a brick or stone on each corner.

Evaporator Coils

Dirt, dust, and debris are the main catalysts to inefficiency and eventual damage throughout the central cooling system as a whole. The components most affected by such issues are the coils, especially the evaporator coils.
While it is common for the filter, vents, and ducts to accumulate filth, it is also possible for the evaporator coils themselves to be covered with dust over time. Dirty evaporator coils result in impaired heat absorption for the refrigerant which, in turn, results in higher energy use by the entire system. Further consequences of dust build-up are higher pressures and temperatures and the development of damaging frost and ice on the coils and throughout the other components. This is due to the dust acting as an unneeded insulator on the coil, which keeps the blower fan from transferring the home’s hot air to the cold refrigerant-filled evaporator coil, resulting in an extended running time just to reach the temperature set on the thermostat.

Condenser Coils

If the evaporator coil isn’t kept clean (or there is poor air flow from the vents, ducts, and filter), the condenser coil could develop frost or ice, severely impairing its function and wreaking havoc on all the other components of the CCS. (Note: Leaky refrigerant can also cause condenser coil frosting.)

If the central cooling system and all its components are well-maintained—and assuming there are no preexisting water or mold issues—the home will be well-guarded against mold’s most notorious avenues for overtaking a house. However, if any of these components are not kept clean and maintained, then the entire system will require greater energy use and extended run-time, which will heavily tax the machine and cost the homeowner not just a large sum of money, but it could cost them their health.

For more information, please contact your local HVAC specialists or heating and cooling technician. Please be advised that there are possible dangers associated with checking and maintaining the “health” of your central cooling system. Components such as the filter, vents, ducts, and exterior unit are generally safe to clean and remove debris from; but it is advised that you switch off power before removing debris from the exterior unit. Issues regarding the coils or leaky refrigerant should be left to the professional.