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AC Tune-Up: How to Clean Evaporator Coils

evaporator coilsIt’s officially summer and high-use time for your air conditioner. To make sure you’re getting the most efficient, comfortable cooling from your system, it’s essential to keep your AC tuned up.

What are Evaporator Coils?

Your AC system has two types of coils: condenser and evaporator. They’re both typically made out of copper or aluminum tubing with aluminum fins surrounding them. The evaporator coil is the indoor coil and sometimes called the “cold” coil because it’s what provides your indoor cooling. It may also be called the A-coil since many are shaped like an “A”.

The coils in your unit, both indoor and out, are vital to cooling your home and controlling humidity. If your coils are dirty, the system can’t work efficiently and you’ll soon feel the effects. Cleaning outdoor coils is a pretty simple DIY project and should be done on a regular basis. But evaporator coils may be a bit more difficult.

The good news is that you have an indoor air filter that keeps the evaporator coil clean. Usually evaporator coils only require cleaning if the system has been run without a filter, if the filter is the wrong size (it’s so loose that air bypasses the filter), or some other event has occurred that allowed unfiltered air to circulate through the coil.

NOTE: Never operate the air conditioner in the presence of sheetrock dust! The wet surfaces of the coil combine with the rock dust to make a cement-like substance that sticks to the coil surfaces.

When Should I Clean the Coils?

If your system has poor airflow, not just to one or two rooms, a plugged coil will inhibit airflow to the entire system. When in cooling mode, the coil may form ice or frost if the restriction is significant. In the heating mode, the furnace may trip on high limit.

You may be able to visually inspect your coil, depending on its location and the duct it is installed in. Many “cased coils” have a painted metal casing with an access door in the front for just that reason. Remove the screws and the metal cover to see the top of the coil. What you’re seeing is downstream side, but you need to look at the upstream side (where the crud accumulates).

Remove the triangle piece of metal to see the underside of the coil surfaces. Lint and dander will accumulate on the surface of the coil and is easy to spot. Use a mirror and a flashlight to see if there is crud impacted in-between the fins. Shine a light above the coil and use the mirror underneath to try and see through the finned coil surfaces. You should be able to see through the coil.

If the coil is inside of a galvanized sheet metal duct without an access door, then its best to hire a professional to perform the inspection and cleaning.

How Do I Clean the Coils?

Cleaning dander and lint is easily accomplished with a vacuum cleaner. If necessary, you can use a soft-bristle brush to help loosen any stubborn dust or dirt. Be careful not to bend the aluminum fins; they are delicate, and if bent, they will restrict airflow. Caution: Wear gloves; the fins have sharp edges.

If cleaning requires more than a vacuum, you may want to consult with a pro. Applying plain water or a mild detergent solution to the coil may be all that is needed and may sound easy, but consider how you’re going to capture the fluid runoff. The coils are at an angle and although there is a drain pan, it is designed to handle clear water condensate that forms at a moderate pace, not large quantities from a heavy cleaning spray. If you attempt a water or solution cleaning process, be sure to protect the expensive electronic controls in the furnace and the blower motor in the base of the furnace.

When in doubt, contact your HVAC pro. They have the know-how and the tools to perform evaporator cleaning and can verify the need.

Don’t Forget Your Filter

Possibly the most important, and easiest, step you can take to maintain your air conditioner is making sure it’s always running with a clean filter! During the cooling months, be sure to check the filter monthly and replace or clean it, as needed.

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