Dirty sock odor in air ducts

By · April 28, 2010 · Filed in Industry News

Do you have the smell of dirty socks when your air conditioner comes on? Your HVAC unit may be experiencing Dirty Sock Syndrome (clever name, huh?). The bad smell is coming from your air conditioner condensation drain pan.

In English, a condensation drain pan is where the condensate made on the evaporator coil drains before is travels out the condensation line. Okay, let me try again. When your air conditioner is on, the air goes through a coil, thin slices of aluminum, that are made colder by the freon (that is why you set your AC thermostat to “auto” so it can cycle on and off and not grow mold). As the air travels through the coils, it gets colder, plus it loses moisture because of dew point. The moisture it loses is collected on the evaporator coil (get it? The evaporator coil evaporates moisture from the air as it passes through). The water made from condensation runs down the coil into the pan and then out the condensation line (usually a one inch PVC line that has water running out the other end when the air conditioner is running).

If the water gets stuck in the condensation pan, it starts to “sour” and smell like, well, dirty socks.

So how do you fix it? It depends on why the water is stuck in the pan.

  • If the air conditioner unit is not installed properly, the drain could be at the high side of the pan, so the water would always be in the pan. Put some kind of shim under the air conditioner unit so that water drains freely to the opening in the pan.
  • If the condensation line gets clogged due to insects, mud, slime build up, etc, water cannot drain out of the pan. What most people do is take some kind of air line and blow it out, from the unit side (don’t blow it from the outside back into the unit).
  • If the pan is dirty, it is probably because your coils are dirty. Use an approved coil cleaner to clean the coil, making sure to clean the condensation pan and blow out the condensation line.

After fixing the problem, the smell should go away, and not return until one of the problems returns.

If you need any help with an inspection or solving any of these problems, call HVAClean at 615-371-5355.

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