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Many times, when it comes time to perform annual maintenance service on your HVAC system, components that are out of sight inside the system cabinet or air handler enclosure are often forgotten or overlooked. One of these important components is your AC unit’s evaporator coils. When the AC coils get dirty, the system loses efficiency and performance and can also result in a breakdown or damage to the system itself.

Why Evaporator Coils are Important
The evaporator coil’s primary function is to capture the heat from your home’s indoor air. While the evaporator coils do their job, the condenser coils (also commonly called the fan coils) release the trapped heat into the air around the outdoor unit. Both coils are typically made of copper and are encased by multiple aluminum fins that help improve the transfer of heat. They are located in separate areas of the HVAC system – condenser coils are in the outdoor cabinet of your system while the evaporator coils are located inside your home in the indoor air handling unit.

Evaporator coils play a vitally important role in the performance of the cooling function of your AC system by providing the cooling that is necessary to generate the cold air that keeps the indoor air of your home or business comfortable, even during the hottest of temperatures. They also play a role in the dehumidification that your HVAC system provides. Water condenses onto the coils as they become cooler, which is then removed from your indoor air. This water is then collected in the drain pan, safely flowing away from the system.

The effectiveness and performance of these two vital functions are greatly reduced when the evaporator coils get dirty. The coils are typically damp from the dehumidification process, so the dust, pollen, and other particulates in the air will stick to the coils as the air passes by them. If the air filter is dirty, or no air filter is used at all, this can also increase the number of contaminants that come in contact with the coil. When all of these factors come into play, enough dirt and dust can collect on the coils to affect their performance in a relatively short amount of time.

Problems that occur when the condenser and evaporator coils get dirty:

  • Ice buildup on the coil
  • Increased wear on the system (leading to damage and malfunctions)
  • Lowered cooling capacity
  • Lowered heat transfer
  • Higher energy consumption
  • Higher temperatures and operating pressures

Dirty coils use up to 40% more energy than air conditioning units with clean coils, as well as reducing the cooling function by an estimated 30% or more. Not only will your AC unit continue to lose performance and efficiency, but your monthly utility bills will continue to sky-rocket if dirty coils are left to wreak their havoc. Evaporator coils should be checked regularly and cleaned as needed. Sometimes coils can be prone to easily collecting dirt and debris, therefore monthly cleaning may be necessary. A typical system, however, usually needs to be cleaned every 3 months during the cooling season and at the very least annually during scheduled HVAC maintenance.

How to Clean Your AC Coils
The first step in cleaning your AC coils is obviously getting access to them. The evaporator coils are found inside your indoor handling unit behind the removable access panel. Before doing anything, make sure you turn the air conditioner off at the thermostat. You may want to shut off your circuit breaker just to be safe! Then, remove the screws or fasteners and loosen the panel, making sure to place the panel and screws aside where they won’t get lost.

Next, use one of the following techniques to clean your AC evaporator coils:

1. Using compressed air

If there isn’t a large buildup of dirt on your coils, it can usually simply be removed with the use of compressed air to blow the dirt off the evaporator coil. You’ll want to direct the compressed air in the opposite direction of the normal airflow across the coil. Also, make sure that you use a consistent airflow across the coil, wear eye protection, and use a shop vac to clean up the dirt and debris as it becomes dislodged.

2. Using a brush

This can be an effective technique for removing light amounts of dirt from the coils, also providing you more control over the pressure and areas that are being cleaned. With this method you’ll use the brush directly on the coils to sweep the dirt away, scrubbing if necessary for harder to remove dirt. You’ll want to use a soft brush, avoiding hard bristles or wire brushes as they can cause damage to the fins.

3. Using commercial cleaners

You’ll have choices when it comes to the selection of cleaners available for cleaning your evaporator coils. After selecting your preferred brand, follow the instructions that come with the cleaner. Let the cleaner sit and foam until both the foam and debris drain away. Reapply as necessary (or per the instructions) until the coils are free of buildup and are clean.

4. Using mild detergents and water

If you prefer not to use a commercial cleaner, a mild detergent and water work just as well sometimes to clean the coils. Mix a simple detergent and warm water in a spray bottle or garden sprayer. Spray the solution onto the evaporator coils and give it a few minutes to soak in and loosen the dirt and debris. Wipe away any loosened material with a soft brush or cloth and reapply as needed.

5. Heavy-duty cleaning

If your evaporator coils are heavily soiled, you may need to use heavy-duty cleaning chemicals and equipment like a steam cleaner or pressure washer. It may also mean you need to take apart more of your AC unit than just a regular cleaning, such as the removal of the coil, cutting of the refrigerant lines, and then reassembly afterward. If this is the case for you, you’ll want to consult with a professional HVAC contractor who can assess the job and will have the correct equipment, training, and supplies to clean the coils and restore your AC system back to normal without incurring the risks of damage.