How to Clean AC Evaporator Coils Inside House

  • In this article we’ll discover how does the air conditioner function and how to take good care of it. After all, our indoor air quality depends fully on these devices. 
  • When speaking about the maintenance of air conditioning systems, it’s essential to pay attention to system components that are out of sight within the system cabinet or air handler enclosure—such as unit’s evaporator coils.
  • Keep reading to learn how to ensure your indoor unit has it’s best cooling capacity and how to successfully clean AC evaporator coils.

A few words about the AC system

Let’s start with the essentials. How do AC units work and what are evaporator coils?

An evaporator coil is a component of your AC system whose job is to absorb the heat from the air inside your home or business location. 

So, how does the cooling system function in your interiors? 

The evaporator coil captures the heat from the air circulating in your home. The condenser coil helps deliver the hot air outside your home.  

An evaporator coil is such an important part of the heat transfer process, that a dirty coil can lead to a drop in the whole AC unit’s efficiency levels.

It can be 

  • attached to your furnace, or 
  • on the inside of your air handler;

With a condenser coil, an AC evaporator works on the heat exchange process that produces cool air.

AC evaporator coil is usually made of copper and surrounded by aluminum whose job is to improve heat transfer. You’ll find evaporator coils inside the indoor air handling unit, and condenser coils in the outdoor cabinet.

To go into detail with how AC evaporator coil cooling function—it’s full of evaporated refrigerant that the compressor pumps to the metering device as a liquid and then into the evaporator. The air pushed through the coil from the blower fan moves over the coil, where the refrigerant in the evaporator absorbs the heat. (read more on Samm’s Heating and Air)

Dirty evaporator coils compromise the efficiency of your system. In the following paragraph, we’ll get to the proper way of cleaning AC evaporator coils.

Clean AC evaporator coils

Poorly maintained coils aren’t only an aesthetical problem.

Dirty coils can significantly increase the energy use of your AC unit! As a result, you can undergo up to 40 percent loss. Not to mention your sky-rocketing monthly utility bills!

You can also expect to experience further problems with your central air conditioners and their cooling function, such as

  • poor cooling performance (because of the reduced heat transfer), 
  • ice buildup on coils, 
  • increased wear on the system (leading to damage and malfunctions),  
  • an overheating compressor;

First off, clean coils regularly. Monthly cleaning is a good, sensible idea. We’ll explain how to do it in the paragraphs below.

Also, change your air filter at least once a month. When your filter gets clogged, the dirt and dust start to settle on the evaporator coils (instead of the air filter). 

Tip: Don’t forget to schedule HVAC maintenance once or twice a year. It’s essential to have this kind of sophisticated equipment inspected by professionals periodically.

So let’s get down to business. Clean your evaporator coils following these five steps.  

Tip: Equip yourself with a pair of gloves, a flat-head screwdriver, a roll of reflective metal tape, and a can of no-rinse coil cleaning solution.

1. Find your air handler and cut the power by turning off the unit switch or the circuit breaker.

2. Remove the metal tape sealing the edges of the coil access panel.

3. Loosen the screws that hold the access panel in place with a screwdriver and take the panel down completely.

4. You’ll recognize the coils on the sides of the metal A-frame by their curving shape. Check them for dust, dirt, and mold. 

Important: In case of mold, call your local HVAC contractor to treat the issue with a special biocide. Read also our article “How To Remove Mold From Air Conditioner Ducts

5. Spray the coils with the no-rinse cleaner—this liquid will slowly drip off up to collecting in the air conditioner’s condensate pan below.

Since you’re here, check the condensate pan for mold or mildew and the condensate drain pipe for blockage (pour some water down through the drain tube to make sure it is clear). 

Finally, put the access panel back in place and reinstall the screws. Cover the panel edges with fresh strips of metal tape.

Important: After you’re done, turn on the air conditioner immediately. It’s going to create moisture condensation on the coils, helping to rinse off any cleaning solution leftovers.

There are five ways to ensure your AC evaporator coils are clean and well-maintained. 

Compressed air

This method is ideal for an average amount of dirt buildup on your coils.

Simply use compressed air to blow the dirt off the evaporator coil. 

But, there’s a trick!

You should direct the compressed air in the opposite direction of the normal airflow across the coil. Remember also to

  • wear eye protection,
  • use a consistent airflow across the coil,  
  • use a shop vac to clean up the dirt and debris as it becomes dislodged.

Use a brush

Again, a technique that works perfectly for light amounts of dirt.

This elementary method for removing grime from the coils gives you control over the pressure and exact areas you’re cleaning. 

Take the soft brush and use it directly on the coils to sweep the dirt away (scrub if necessary).

Tip: Avoid stiff bristles or wire brushes as they can cause damage to the fins.

Commercial cleaners

It’s helpful to have a commercial cleaner at hand—the market selection is vast. 

Just pick your favorite brand and follow the instructions on the cleaner. 

Let the cleaner sit and foam until the foam and debris drain away. 

Reapply until the coils of your air conditioner are free of buildup completely.

Mild detergents and water

Instead of heading to the store for a commercial cleaner, you can prepare your own concoction.

Can you clean evaporator coils with a mild detergent and water?

Yes, you can, and it’s not that hard!

Simply mix a mild detergent and warm water and pour it into a spray bottle or garden sprayer. 

Now you need to spray the solution onto the evaporator coils of your indoor air handling unit and give it a few minutes to soak.

After your mixture starts to loosen the dirt and debris on your coils, wipe it away with a soft cloth. Reapply if needed.

Heavy-duty cleaning

The methods to clean AC evaporator coils we shared above are helpful for a little to medium amounts of dirt. 

But what if your air conditioning unit is heavily soiled and the cooling season is getting closer?

In this case, you may need to use heavy-duty cleaning chemicals and more advanced equipment, such as

  • a steam cleaner, or 
  • pressure washer;

Other than that, you may be forced to take apart more of your air conditioning system than for regular cleaning. We mean the removal of the coil, cutting off the refrigerant lines, and then reassembly.

Get in touch with your local HVAC contractor, who’s perfectly prepared to clean the coils and restore your AC system to normal without incurring the risks of damage.

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Frequently Asked Questions

AC coils should be cleaned at least once a year to minimize energy usage and reduce utility costs. Dirty evaporator and condenser coils can significantly increase the energy usage of your AC system.
Cleaning the coil in place will cost you $100 to $400, removing and cleaning the coil from $400 to $700.
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