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How to Clean and Maintain an HVAC Evaporator Coil

Although it’s not normally seen, your HVAC unit’s evaporator coil is one of the most important parts of the cooling unit, and a dirty coil can seriously reduce your unit’s ability to do its job. Fortunately, coil cleaning is fairly easy to do, even if your don’t have a lot of experience. Generally speaking, it’s a good idea to do a coil cleaning at least once a year, either at the beginning of the cooling season or a little before. It can also helpful to make sure that you are regularly changing your unit’s air filters, which can reduce the amount and rate of dust build-up on the coils. Read on for a few tip for cleaning an evaporator coil, which can improve your AC unit’s functioning and keep your home at your desired comfort level.


How an Evaporator Coil Works

An evaporator coil is a component of your HVAC system’s air conditioning unit, typically made of copper coils equipped with a set of aluminum fins to improve their ability to move heat. The primary purpose of your evaporator coil is taking in heat from the interior of your home and transferring it to the air conditioning system.

Evaporator coils also frequently have a secondary purpose that you should be aware of. During the process of cooling, air’s ability to hold water vapor is reduced, and the extra moisture condenses on the coils that are providing the cooling. This water is collected below the coil in a drainage pan, which usually feeds it to a drain outside the building.


Why Coils Need Cleaning

The key to maintaining a working evaporator coil is making sure your coil is able to to interact with the air around it. When dust and other air contaminants such as smoke residue from cooking or smoking collect on the surface of the coils, they act as insulation that reduces how effectively the coil transfers heat from the air to the coil. In cold weather, collected moisture on the coils can freeze, which will also prevent the unit from working properly. None of this will necessarily stop the unit from working, but it will make it less efficient, affect the lifespan of the HVAC unit, take up more power and decrease your home’s air quality.

If you ever notice that your HVAC unit is not cooling as well as it normally does, it’s a good idea to check the coils for layers of accumulated dust and dirt or ice. Iced coils should be left to thaw before trying to use the air conditioning again, but solid debris needs to be cleaned off by hand. Fortunately, coil cleaning is usually not difficult. Sometimes you can simply reach in (after turning the power off!) and peel off a layer of lint and dust. Other times, it takes a little scrubbing. However, if you’re at all uncertain about cleaning the coils and fins, it’s a good idea to call a professional.


Useful Cleaning Tools and Techniques

Before you attempt to clean your evaporator coil, always ensure that you have shut off power to your HVAC unit. In a pinch, especially with minor dirt build-up, you can use a rag and a little dishwasher detergent to scrub off the dust and dirt. If your household has a lot of smoking residue or smoke and grease residue from frequent cooking, or if you have not had a coil cleaning in a long time, you’re going to want something with a bit more cleaning power.

Make sure the evaporator coil is warm – a cold coil is much more difficult to clean – and apply an alkaline cleaner or some type of solvent to scrub away the residue. It’s not normally a good idea to use any acid-based cleaner on an evaporator coil, since these cleaners can damage the more delicate parts. Use a pulling motion to clean the coils and fins, moving the debris out and back the way they entered; this will prevent you from jamming the dirt farther in.

If you open the unit to find that the build-up is heavier than you expected, or if you’re not sure you can do a coil cleaning without bending or damaging parts of the coil and fins, you can call a professional to have the unit cleaned and get its yearly service at the same time.


If you want to make sure that your AC works the way you need it to, you need to make sure to properly maintain your evaporator coil. When you clean an evaporator coil, you ensure a properly functioning air conditioner and a comfortable home.


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