I often hear contractors complain about "dirty sock" syndrome. It's caused by a dirty coil that has begun to feed bacteria. As the bacteria grows and blooms, the air passing over the coil picks up a lovely odor similar to dirty socks. I was in the chemical industry before I joined the HVAC industry, so I've had a great deal of success dealing with dirty sock syndrome. In the chemical industry, it's commonly known that disinfectant must be in contact with a non-porous surface for 10 minutes to effectively kill bacteria. This is a half-truth. You do need to let a disinfectant sit for 10 minutes, but you must keep the surface wet with the disinfectant for those minutes. Apply your disinfectant generously, and spray more on as needed to keep the coil wet.
You also must be sure that you have cleaned the entire coil — this means deep inside the coil as well as its surface. Use a high sudsing detergent that's safe for evaporators. The sudsing action gets deep in the coil, and helps bring the dirt and bacteria to surface.
You don't need a special chemical to do the job. I use a combination of a standard coil cleaner, and concentrated Lysol that I buy from the grocery store in the good old brown bottle. I use the maximum strength mixture (or even a little stronger) that's recommended by the directions on both of the chemicals. I reapply the solution two or three times to be sure the coil is clean and disinfected.
How do I know when a coil is clean? If I don't get a lot of foaming action, I know the coil isn't clean. It's only when the coil is filled with foam that I know the job is being done.
Your work area can become very messy with all of this foam, so be sure you take care not to let it get everywhere. Be prepared to control the foam!
After this thorough cleaning, rinse both the coil and the drain line. This will get rid of all the disinfectant, as well as the bacteria that was causing the odor in the first place.
If you follow these simple rules, you'll have success cleaning up your customers' dirty socks. Believe me, getting rid of that odor will make them very happy.
Mitchell Bagwell is co-owner of O'Neill-Bagwell Cooling and Heating, Myrtle Beach, SC. He can be reached at 843/385-1917.