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Air Handler Sweating

Your A/C system is no stranger to moisture. In fact, your air handler pulls moisture from the air and drains it away from your home.

However, air handler sweating is different. Condensation on the outside of your air handler can be an effect of an underlying issue. Moreover, the excess moisture can lead to a damaged plenum, mold, or termites.

Related articles: A/C unit lifespan. What is HVAC?

Here are the most common reasons for air handlers sweating so you can stop the condensation.

Please note: sweating on the A/C system could be from a combination of the items listed below. Also, it could be due to the unit’s age.

Humid Air and Air Flow

If an air handler is in a garage, attic, crawlspace, or closet, it might experience less air flow and humid air. This is a common occurrence in Florida garages. Hot, humid air mixes with the cold internal air of the air handler by the cold metal of the unit causing condensation.


Add more air flow around the air handler by adding vents or a physical fan. If the unit is in a closet or garage keep the doors open, or add a fan.


There is a such thing as cooling the air too much. This happens when the A/C system cools the air more than 24 degrees. 14-24 degrees is the sweet spot of cooling.


Really the only solution to this problem is servicing the unit by a licensed HVAC technician. You can find out if your unit is super cooling by using a thermometer to get the temperature of the air at the air filter, and then right as the air comes out of the unit.

Poor Insulation

In some cases, the air handlers simply are not insulated well enough in areas. This is typical if you find condensation or microbial growth around the air handler joints/connections to ductwork to the plenum.


Simply put, add more insulation. You could also use an insulating HVAC paint they use on ducts.

Thermostat Setting

If the house is getting too cold in comparison to the outside air, it might be impossible to insulate the unit enough to stop the condensation.

Condensation Line Blocked

If the condensation line is backed up, it can prohibit the unit from “breathing” like it should.


Use a wet dry vacuum to suck out the water and debris from the condensation line. If you need assistance, read this article about mold around air handlers that explains it more in depth.


Minor air handler sweating is okay and normal. However, too much condensation and moisture can lead to mold, termites, and other damage.

You should always try to add as much as circulation as possible and ensure your unit is performing efficiently.

If your air handler is over 10 years old, it might be time to replace the unit anyway. Read about air handler life expectancy.