Keeping our home’s HVAC systems shipshape all year round is an important part of necessary home maintenance. After all, we wouldn’t be able to stay warm during the winter months or survive the warm summers if not for these systems. 

While repairs are reactive in nature, it is the preventive maintenance activities we conduct that ensure the longevity of our HVAC systems. One such maintenance activity is cleaning our air conditioner’s evaporator coils at least once a year. But, how to clean evaporator coils?

What are evaporator coils?

All ACs have two kinds of coils: condenser coils and evaporator coils. Evaporator coils are responsible for capturing the heat from indoor air, while condenser coils are responsible for releasing that heat through the outside unit of the AC. 

Therefore, it is no surprise that evaporator coils are found inside the indoor unit of an air conditioner, while condenser coils are found in the outside unit. Both of these coils are made out of copper in most cases and are surrounded by aluminum fins to transfer heat more efficiently.

Evaporator coils are responsible for cooling down the hot air from the outside, making them an integral part of the system responsible for keeping your home cool even when outdoor temperatures are scorching.

Another important role evaporators play is they also help dehumidify your home. The excess moisture is removed from the room and settles on the coils, from where it flows down into a drain pan before being disposed outside of through a pipe.

Understanding how air conditioners function

Most air conditioners have two units: an indoor one and an outdoor one. The indoor unit has the evaporator, evaporator coils, and the airflow system, while the outdoor system is made up of the compressor, condenser, and condenser coils.

The evaporator coils capture heat, while the condenser coils disperse it.

A refrigerant circulates through the system, and depending on where in the cycle it is, changes from a gas to a liquid state and back to a gas. During this process, hot air is cooled and pumped into your home, cooling it down.

The cooling agent in these air conditioners is a gaseous refrigerant, which actually contains heat and is pressurized in the compressor. As it enters the compressor, the condenser coils release the heat in it and it changes to a liquid state. 

As this liquid enters the evaporator, it changes to gas again, and as a part of the process, absorbs the heat from the air surrounding it. This makes the evaporator coils very cold, and when the air handler blows air across these cold coils into the air ducts, your home gets cold air. The return ducts then bring warm expended air back into the system, where the air filters filter the air and the entire cycle begins again.

Signs of dirty evaporator coils

clean air thanks to clean coils

A dirty evaporator coil translates to a less efficient air conditioner. But let’s first understand how these coils get dirty.

Evaporator coils are moist most of the time, thanks to the condensation of the humid air they capture. This moisture on the surface of the coils makes dust, pollen, and other pollutants present in the air being sucked in stick to them. 

Another factor we need to consider is that as air filters in the ACs get dirtier, more dirt is allowed to enter and sit on the coils. Here are some telltale signs of dirty evaporator coils.

  1. Your AC’s cooling capacity is reduced by almost 30%.
  2. The heat transfer happening is inefficient.
  3. Your utility bills are increasing, thanks to an increase in energy consumption by up to 40%.
  4. An increased load on the system, leading to excessive wear and tear, breaking down of components, and possible system malfunctions.
  5. A marked increase in operating pressures and temperatures.
  6. Ice builds up on the coils.

Read more: What is a plenum

How to clean evaporator coils

Depending on where you live, you may need to clean the dirty evaporator coils every month if they are prone to collect a lot of dust. Otherwise, once every three months during the summer is a good idea, and once more during your annual HVAC maintenance cycle. 

Let’s now discuss how you can access the coils and hope to clean them with different cleaning agents.

Getting access to the coils

  • Check the owner’s manual to locate the location of the access panel on the indoor unit of the air conditioning system.
  • Use the thermostat to turn off the air conditioner.
  • Use a screwdriver to loosen the screws holding the access panel.
  • Once removed, place the panel and screws aside.

Cleaning the coils using compressed air

  • Direct pressurized air through the pressure washer from the cleaner side of the coil to the dirtier side.
  • To remove stubborn pieces of dirt, get the nozzle closer and direct the airflow towards the bottom of the dirt and debris.
  • To prevent damage to the coils fins, direct air either through the fins or at a 90-degree angle.
  • Make sure you maintain a constant airflow across the foil to avoid dirt being forced into the fins.
  • Air should be directed such that none of the dust blows into your home’s ductwork.
  • Always wear protective eyewear to prevent dust from getting into your eyes. 

Cleaning the coils with a brush

  • This method is useful for minor dust buildup.
  • Use the brush to remove dust from the surface of the coils. In the case of stubborn debris, apply pressure with the dust to dislodge it.
  • Avoid using abrasive wire brushes and hard bristle brushes. You do not want to damage the fins.

Read more: Prepare HVAC for home renovation

Cleaning the coils with commercial cleaners

  • Most commercial cleaners are the foamy type that breaks down and drain away into the drain pan. However, consult your local HVAC contractor as to which one you ought to use.
  • Read the product instructions thoroughly before you begin.
  • Spray the cleaner on the coils.
  • Wait for it to foam and drain away by itself.
  • Repeat the process until the coils are clean.

Read more: Winterize an AC window unit

HVAC maintenance: How to clean evaporator coils was last modified: December 28th, 2022 by Narayan Shrouthy
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Evaporator coils may require strong chemicals or heavy-duty cleaning techniques, I think is not a DIY task…