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How to Clean A/C Evaporator Coils

Posted on: August 1, 2013

When it’s time for the annual preventive maintenance on your air conditioner, don’t forget to pay particular attention to system components that are out of sight within the system cabinet or air handler enclosure. The unit’s evaporator coils are among the more important of these hidden components. When problems develop with dirty evaporator coils, your A/C’s efficiency can drop, it’s performance will decrease, and damage or breakdowns can occur. Here is some basic information on air conditioner function and the importance of evaporator coils, along with some instructions on how to clean A/C evaporator coils.

The importance of evaporator coils

Evaporator coils capture heat from the air inside your home, while condenser coils release that captured heat into the air around the A/C’s outside unit. These coils are usually made of copper and are surrounded by a series of aluminum fins that improve heat transfer. Evaporator coils are found inside the indoor air handling unit, while condenser coils are contained in the outdoor cabinet.

Evaporator coils are vitally important to the cooling performance of your air conditioning system. They provide the cooling that is required to produce the cold air that keeps your home or business comfortable even when temperatures are at their hottest.

Evaporator coils are also involved in the dehumidification your air conditioner provides. As these coils become cooler, water condenses on them and is removed from the air inside your home. This water is collected in a drain pan, where it flows away safely.

When evaporator coils get dirty, their performance in these two functions is significantly reduced. Air blowing across the coils can contain dust, pollen, and other particulates. Since the coils are usually damp from the dehumidification process, it is very easy for contaminants to stick to them. Dirty air filters in the system (or the lack of filters entirely) can increase the amount of material that makes contact with the evaporator coil. In just a short amount of time, enough material can accumulate on the coils to affect their performance.

When evaporator coils and condenser coils get dirty, there can be problems such as:

  • Reduced heat transfer.
  • Decreased cooling capacity.
  • Increased energy consumption.
  • Increased operating pressures and temperatures.
  • Increased wear on the system, which can lead to component damage, system malfunctions and reduced life expectancy
  • Buildup of ice on coil

In general, you can expect an air conditioner with dirty coils to use almost 40 percent more energy than one with clean coils. Cooling function can be reduced by 30 percent or more. Your monthly utility bills will soar even as your air conditioner continues to lose efficiency and performance.

Basic air conditioner function

Split-system cooling systems such as central air conditioners consist of an indoor and outdoor unit. The outdoor unit contains the condenser, condenser coils and compressor, while the indoor unit contains the evaporator, evaporator coils and the air handling system. Heat is absorbed by the evaporator coils and dispersed by the condenser coils.

As refrigerant circulates through the system, it changes state from a liquid to a gas and back again, depending on where it is in the cycle. Heat is absorbed or released during these changes of state, and in the process cooling is produced for your home or business location.

Gaseous refrigerant contains heat, and in the outdoor unit, it is pressurized in the compressor. The refrigerant then enters the condenser, where the heat it contains is released to the outdoor air via the compressor coil. In the process, the refrigerant returns to its liquid state.

The liquid refrigerant then flows into the evaporator, where it evaporates into a gas. As this process occurs, the refrigerant absorbs heat from the air around it. The evaporator coil gets very cold and becomes the source of the cool air that is distributed to your home. The air handler blows air across the cold evaporator coil, and as the cool air passes beyond the coil, it is directed into the ductwork system. There, it is sent into your home through vents and registers at the ends of the duct network. Return ducts bring warm expended air back to the system, where the air is filtered and the cycle starts over again.

The importance of regular A/C maintenance

Regular preventive maintenance is critical to keeping your air conditioner working properly. Maintenance should be performed at least annually, usually before cooling season starts. In most cases, seasonal maintenance should be done by an HVAC professional. Tasks performed include system testing and adjustment, minor repairs and component replacements, air filter changes and cleaning of evaporator and condenser coils.

You can perform some of these maintenance tasks yourself, such as changing air filters. If you are mechanically inclined, you can also clean the evaporator coils. Here are some useful steps for how to clean A/C evaporator coils, based on the type and extent of cleaning performed. These steps can also be used to clean the compressor coils in the outside cabinet.

How to clean A/C evaporator coils: the basics

Evaporator coils should be checked and cleaned as needed. If the coils are prone to collecting dirt and debris easily, monthly cleaning may be required. Otherwise, you may need to clean them every three months during cooling season or annually during regularly scheduled preventive maintenance.

How to clean A/C evaporator coils: getting access

Your indoor air handling unit should have an access panel that can be removed to expose the evaporator coil. If necessary, check your A/C owner’s manual to locate the access panel and evaporator coil.

  • Turn the air conditioner off at the thermostat.
  • Remove the screws or other fasteners to loosen the access panel.
  • Place the panel and screws aside where they won’t get lost or separated.

How to clean A/C evaporator coils using compressed air

Light accumulations of dirt and other material can often be removed using compressed air to blow them loose from the evaporator coil.

  1. Direct compressed air across the coil in the opposite direction of normal airflow, from the cleaner to the dirtier side.
  2. For more stubborn pieces, place the air nozzle close to the bottom side of the debris.
  3. If using high pressure air, direct it either at a 90-degree angle or directly through the fins. This will prevent damage to the fins.
  4. Maintain consistent airflow across the coil. This will dislodge buildup without forcing it further into the fins and making it more difficult to remove.
  5. Avoid blowing dust, dirt and debris into the ductwork system or into your home’s living spaces. Wear eye protection to keep the material out of your eyes. If necessary, use a shop vacuum cleaner to collect material as it is dislodged.

How to clean A/C evaporator coils using a brush
Brush cleaning can be a very effective technique for removing minor accumulations of dirt from evaporator coils. Brush cleaning allows you to avoid the use of liquids or chemicals and gives you greater control on the pressure applied to the coils and fins.

  1. Apply the brush to the coils and sweep dirt accumulations away.
  2. Scrub with the brush to break loose harder-to-remove material.
  3. Avoid using wire brushes or hard-bristle brushes since they may damage the fins.

How to clean A/C evaporator coils using commercial cleaners

Several brands of commercial cleaners are available for cleaning evaporator coils. Most are a foaming type that breaks down and drains away into the unit’s drainage system. Consult with your trusted local HVAC contractor for suggestions on which cleaner would work best for your situation.

  1. Follow instructions and precautions that accompany the product.
  2. Spray the cleaner on the coils as directed.
  3. Allow the foaming action to occur and wait until the foam and debris drain away.
  4. Reapply the cleaner until the coils are clean and free of buildup.

How to clean A/C evaporator coils using mild detergents and water

In place of a commercial cleaner, you can use a mild detergent and warm water to clean the coils.

  1. Mix warm water and a simple detergent in a spray bottle, hand sprayer or garden sprayer.
  2. Apply the water and detergent solution to the evaporator coils.
  3. Give the solution a few seconds to a few minutes to soak in and loosen debris. Reapply as needed.
  4. Wipe away the loose material with a soft cloth or brush.

How to clean A/C evaporator coils: heavy-duty cleaning

Heavily soiled evaporator coils may require strong chemicals or heavy-duty cleaning techniques and equipment such as a pressure washer or steam cleaner. The process could also require revisions to your A/C system, such as removal of the coil, cutting and reattachment of refrigerant lines, restoring the vacuum in the refrigerant lines and recharging/refilling the system with refrigerant.

If your A/C evaporator coils are heavily soiled or are dirty enough to seriously affect air conditioner function, you should schedule a professional cleaning and maintenance appointment with your local HVAC contractor. Your HVAC technician can properly assess the job and will have the correct equipment, training and material to clean your evaporator coil and restore cooling system function without causing damage to the coils, fins or other components.

Black Diamond Plumbing & Mechanical provides professional heating, air conditioning and plumbing services. Contact us today for more information on how to clean A/C evaporator coils or to schedule a professional maintenance and cleaning appointment for your home or business cooling system.

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