Cleaning Evaporator Coil Pan: A Step-By-Step Guide

Cleaning the evaporator coil pan is an important part of maintaining your HVAC system. The evaporator coil is responsible for capturing heat from the indoor air and transferring it to the outdoor unit. Over time, the coil can accumulate dirt and debris, reducing its efficiency and affecting the performance of the cooling function of the AC system. Therefore, it is recommended to clean the evaporator coil pan at least once a year to maintain the efficiency of the HVAC system. This can be done by following a few simple steps, including turning off the power to the system, locating and exposing the coil, and using a vacuum, brush, or mild detergent solution to remove built-up dirt and debris.

How to Clean Evaporator Coil Pan

Remove the access panel

Removing the access panel is the first step to cleaning your evaporator coils. This is a simple and straightforward task, but it requires careful attention to detail.

First, locate the access panel. It is usually found near the bottom of the air handler. Depending on the make and model of your unit, the panel may be screwed in place or held in place by clips. If it is a Carrier Evap coil pack, you will find three 5/16" hex screws along the bottom of the service panel and a single 5/16" hex screw at the top right. You may need to use a socket wrench, nut driver, or screwdriver to remove the screws. If your installer used mastic or silicon caulking, you may need to cut through this to remove the panel.

Once you have located and removed any screws or other fasteners, carefully lift the panel away from the unit. Place the panel and screws aside somewhere safe, where they will not get lost or separated.

With the access panel removed, you will now be able to see the evaporator coils. These are typically made of copper, steel, or aluminium, and consist of tubes bent into a U-shape within an A-frame design of two panels.

Now that the access panel has been successfully removed, you can move on to the next steps of cleaning your evaporator coils.

Inspect the evaporator coils

The evaporator coils are responsible for removing heat and humidity from the air that passes over them. Over time, the coils can accumulate dirt and debris, reducing their efficiency and performance. Therefore, it is important to periodically inspect and clean the evaporator coils to ensure optimal function.

To inspect the evaporator coils, first turn off the air conditioner and shut off the electricity to the air handler. This is an important safety precaution as it prevents the risk of electrical shock. The evaporator coils are typically located inside the air handler unit, which is usually found indoors in a closet or attic. Once you have located the air handler unit, remove the access panel by unscrewing it or lifting it out of its clips.

With the access panel removed, use a flashlight to inspect the evaporator coils. They are usually made of copper, steel, or aluminium, and consist of tubes bent in a U-shape set into an A-frame design of two panels. If you see any buildup of dirt, dust, or debris on the coils, use a soft brush or cloth to gently remove it. Be careful not to damage the coils and avoid brushing across the fins, as this can cause them to bend and block airflow.

In addition to visual inspection, you can also check for a dirty evaporator coil by gauging the temperature gradient before and after the air passes over the coils. A normal range for the drop in temperature is 20 to 25 degrees Fahrenheit. If the values are below this range, it indicates that buildup on the coils is affecting system efficiency.

Another method to identify a dirty evaporator coil is to check the air pressure at the intake and output of the air conditioning unit. Compare the pressure difference with the values in the instruction manual. If the values are significantly off, it is likely that the evaporator coils need cleaning.

It is recommended to have a qualified technician perform a complete system check-up once a year, which should include inspecting and cleaning the evaporator coils as necessary. Regular maintenance of the evaporator coils is crucial for ensuring optimal performance and longevity of your air conditioning system.

Use a pump sprayer and brush

To clean your evaporator coils using a pump sprayer and brush, you will need a few specific supplies. These include a pump sprayer (1-2.5 gallons), a professional cleaning solution, and a brush.

First, mix your cleaning solution according to the product instructions. You will need about 1 gallon of the solution for a routine cleaning. Adjust the spray wand to a narrow 0.25-inch spray. Spray the coils and allow them to dry for a few minutes. Ensure that you can see the dirty solution running down to the condensate drain pan. If there are clumps of debris, direct the spray at the coils from a low angle to peel them off.

Next, use your brush to scrub the coils. Rinse the brush often in a new bucket of clean water to avoid adding residual chemicals or dirt to the coils. Brush in straight lines, working slowly and carefully. Never brush across the fins, as this can cause them to fold and block airflow. Use short brush strokes to ensure precise, straight-up, and down motions.

After brushing, respray both sides of the coils with the cleaning solution to remove any loose dirt. Finally, reattach the evaporator coil access panel and seal it with HVAC tape.

Clean with mild detergent and water

To clean your evaporator coil pan with mild detergent and water, start by turning off your air conditioning system and removing the access panel to expose the evaporator coil. You can refer to your user manual for instructions on how to do this. Once you have access to the coil, vacuum or wipe away any loose dirt and debris.

Next, mix a solution of warm water and mild dishwashing detergent in a spray bottle. Ensure that you only use a few drops of detergent, and that it is not highly acidic, as this can cause corrosion to the coil. Spray the solution onto the coil, allowing it to soak for a few seconds or minutes. You can then either let the coil drain naturally or rinse it with water. Finally, wipe away any remaining loose material with a soft cloth or brush, being careful not to bend the thin metal fins on the coil.

Once the coil is clean and dry, you can replace the access panel and turn your air conditioning system back on.

Spray with commercial cleaners

Purchase a commercial cleaner designed for cleaning evaporator coils. These are readily available at most home improvement stores. The majority of these cleaners are of the foaming type, intended to break down debris and then drain away into the unit's drainage system.

Spray the cleaner directly and evenly onto the coils. It is best to do this on a warm day, as the A/C will have been running, helping to rinse the coils with condensate water.

Pour 1 US quart (0.95 L) of a bleach/water solution into the drain pan. This will ensure the drain line is free of algae and unclogged. When the foam rinses itself off and drains away, it will collect properly in your unit.

Alternatively, you can buy time-release algae tablets to drop into the drain pan.

Pour water down the condensate drain tube. This will help you verify that the tube is draining properly. If the tube seems blocked, indicated by standing water in the drain pan, discontinue use of the air conditioning system and call an HVAC contractor to clear the blockage.

Reapply the cleaner. Repeat until the coils are clean and free of buildup. Make sure you wait until the cleaner liquifies the debris and drains away before applying more.

Frequently asked questions