Central air conditioning systems bring in outside air, cool it, and push it through the home's ductwork and vents to lower the overall temperature. When it runs, you may occasionally notice small droplets of moisture on vents, which is normal. However, extensive condensation around the outdoor unit or ducts can harm the system and damage the home. Here are several reasons why this issue occurs.

Why Does Condensation Form When Running the Air Conditioner?

1. Boot Leaks

Boots are L-shaped metal tubes that join ducts with vents. Cracks or gaps in the boot can cause warm, humid air to enter the duct and collide with cold metal surfaces, which produces condensation. When this happens, the moisture within the duct may drip into indoor areas. While this generally isn't a cause for concern, excess moisture requires a contractor to patch or replace the boot to prevent further issues.

2. Damaged Ducts

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Ducts are tubes made from thin sheet metal. They contract when exposed to cool air and expand with warm air, and repeated temperature changes can warp the metal and cause small fissures to form. This allows warm indoor air to enter the ducts and create condensation. A contractor can replace damaged segments and wrap ducts with insulation, keeping the system closed.

3. Drain Line Clogs

Air conditioning units produce condensation as a byproduct of removing humidity from intake air. This liquid collects in the evaporator coils, leaves the system through a drain line, and empties into a pan. However, if debris clogs the drain line or the pan fills up, the moisture can leak outside the unit. Alternatively, it may travel with the conditioned air through the vents, which can contribute to mold growth throughout the home. A technician may remove blockages from the drain line or repair the condensate pump so that the unit functions correctly.

4. Frozen Coils

When excess dirt and debris collect within the air conditioning unit, warm air cannot flow properly over the evaporator coils. This causes them to freeze, preventing the appliance from cooling the air. You may notice this issue if the vents are producing warm or lukewarm air. Then, when the frozen coils thaw, the melted fluids may leak into ducts. This is a relatively simple issue that requires a contractor to clean the coils.


When you notice condensation leaks, contact Air One Heating & Cooling LLC in Foley, AL. These contractors provide residential and commercial HVAC installations, repairs, and maintenance to clients throughout Baldwin County. Call (251) 967-1665 to request an estimate on air conditioning repairs, and visit the website to learn more about how they can keep your HVAC system functional.