How to Clean Air Conditioner Evaporator Coils

For homeowners with adequate DIY skills, knowing how to clean air conditioner evaporator coils can save money and increase the comfort level in your home this summer.

Many people mistakenly assume that the frigid refrigerant circulating through the evaporator coil adds coolness to the air in your home. Actually, it extracts heat energy. After the heat energy is removed from the air, coolness is just what’s left behind. Anything that interferes with the transfer of heat from the air to the refrigerant, such as a layer of dust or dirt on the coil surfaces, degrades the efficiency of your A/C and costs you money in increased utility bills. Your system runs longer to achieve thermostat settings and the humidity extraction process — an important function of an A/C system — is much less effective. Dirty coils can also lead to coil icing which, if it goes unchecked, may eventually freeze up the entire coil and trigger an automatic system shutdown.

Since the evaporator coil is installed directly in the airstream of your system, it’s a magnet for accumulation of dust or other contaminants. An annual inspection of the evaporator coil is critical. The external surfaces of the evaporator coil that face the airflow in the duct are accessible and cleaning is generally within the skill level of most do-it-yourselfers. However, if dust or dirt contamination is so extensive that the inside coil surfaces are affected, too, schedule a more extensive, heavy-duty cleaning procedure with your HVAC contractor. Here’s a basic primer on how to clean air conditioner evaporator coils.

1. Purchase a can of commercially available no-rinse coil cleaner. This is normally a foamy substance in a spray can that is applied directly to the coil surfaces.
2. Locate the air handler unit, usually installed in a closet or attic. 
3. Turn off power to the air handler at the main switch or circuit breaker.
4. Remove the metal reflective tape that seals the seams around the coil access panel.
5. Remove the screws that secure the coil access panel to the air handler. 
6. The evaporator coil is configured in an A-frame design with two sides. Examine the external surfaces of the coil for dirt or dust residue. Also be alert to any signs of mold growing on the coil. Mold contamination will need to be treated by your HVAC contractor using biocides approved for use in cooling systems.  
7. Spray the coil cleaner on all exposed surfaces of the coil. Allow the cleaner adequate time to soak in and  drip down into the condensate drain pan below the air handler. 
8. While the cleaner is soaking the coil, examine the drain pan. Look for any evidence of mold growth or algae. Minor contamination can be treated with a 50/50 mix of bleach and water. Severe contaminations, however, should be addressed by your HVAC contractor.  
9. Pour some water down the condensate drain tube that leads away from the drain pan to verify that the tube is open and drains properly. If you see evidence that the condensate drain tube is blocked, such as standing water in the drain pan, discontinue use of the A/C and call your HVAC contractor to clear the blockage.
10. After the coil cleaner has dripped off the coils, examine the coil surfaces for any areas that may need another application of cleaner and re-apply as necessary.  
11. Reinstall the coil access cover and tighten the screws. Tape the seams around the access cover with metal tape. Restore power to the air handler and turn on the system to generate condensation on the coils for additional rinsing. 

While knowing how to clean air conditioner evaporator coils comes in handy, remember that the best prevention for dirty coils is purchasing a quality system air filter and changing it regularly. During cooling season, monthly changes are a good idea.

Serving the homeowners of Beaumont, Orange, Port Arthur and surrounding areas, the experienced staff of Thermacon Service Company are the heating and cooling professionals. Contact us for more information on how to clean air conditioner evaporator coils yourself, or to schedule a professional cleaning by one of our trained technicians and let us do the work for you.