Condensation in AC vents is most common during the spring and summer and occurs when moisture-saturated air makes contact with a colder surface. The cold surface cools the water vapor, causing it to condense into drops that collect on the surface of vents.
The temperature of the vent is less than the dew point of the air surrounding it causing water to condense from vapor (humidity) to liquid. As others have said, it's probably because the room is humid. The higher the dew point, the higher the humidity.
The cause of sweating vents is simple. Air that's humid enough finds a surface cold enough. When vents start beading up with water--or worse, dripping--either the humidity is too high or the vent is too cold. It's not hard to figure out which of those two is the culprit. Just find the dew point of your indoor air.
Without prompt attention, excess condensation could overwhelm your air conditioner's drainage system, causing damage within your home. This damage can range from high humidity levels that lead to mold and mildew proliferation and spots, to structural damage from drainage water that accumulates and puddles.
Set the Fan to AUTO
As the refrigerant coils in your air conditioner absorb heat and moisture, cold air is blown in. The moisture stays behind and collects on the coils. If you keep the fan set to ON, the moisture will continue to be blown back inside.
A small amount of ductwork sweating is not going to cause irreparable harm. If you start noticing a lot of condensation on your ducts that might be a sign of a bigger issue. Ductwork sweating can drip onto your home's insulation which compresses and then lowers its efficiency over time.
The problem is that the condensate pan is open all the time. Aside from water, it also collects dust, dirt and other small particles. This accumulation can enter the drain line system and eventually clog it. Once the passage is blocked, there is nowhere for the condensation to go, and your AC unit might blow it out.
Potential Solution: Insulation
Your plumber may suggest insulating cold water pipes in certain areas to help prevent problems with sweating. Sometimes failed sealant can also create condensation problems, so resealing plumbing with new insulating materials may also be an appropriate solution.
Air conditioner sweat happens when the air temperature is below the dew point temperature. The dew point temperature is the temperature at which water vapour will start to form. The excess moisture – or air conditioner sweat – created can also lead to damage to your walls, termites and mould.
Ideally, there should be a temperature differential of around 14° to 20° Fahrenheit between the incoming air and the air being blown out by your air conditioner. This means that if the air entering the system is 75°F, the air coming out of the vent should be between 55°F and 61°F.
Mold Growth
Closed air vents can lead to condensation occurring in other rooms where the air coming out is too cold compared to the room's temperature. The condensation can then result in mildew and or mold growth which you will likely be able to smell before you see it.
Try to reduce the humidity level in the air near the air ducts. You can go for a dehumidifier if that helps to reduce the condensation. Unblock any ducts that are restricting airflow and have them cleaned regularly. Regularly clean your air filters and change them once every three months.
Moisture will cause acid to form in the system causing serious damage to the compressor and expansion valve parts. It also deteriorates the insulation of the motor windings in the compressor.
Dust, dirt, and other debris can clog the drainage system that carries water from your AC and away from your home. When this happens, it can cause your system to leak. Damaged Drain Pan: If you inspected your condensate line and it's free of blockages, your drain pan may be damaged.
Condensation gathering and overflowing in your AC unit can lead to water damage in your home. Indoor units with untended leaks can cause extensive damage to floors and walls. Leaking water raises humidity levels in your home as well. Humidity in Hawaii isn't just uncomfortable; it can cause mold and mildew to grow.
The air conditioner draws warm air, which is then cooled. This naturally results in condensation. If the heater box has condensation buildup, the condensation can turn into vapor and go out of the vents with the cooled air. As a result, you'll see white fog or “smoke” coming out of the AC vents.
High home humidity levels and poor insulation can cause condensation on AC ducts. Dirty air filters and ductwork with blockages can also trigger AC condensation. Combat condensation on AC units by maintaining ductworks, adding insulation in key spots, and using a dehumidifier.
Condensation in AC vents is most common during the spring and summer and occurs when moisture-saturated air makes contact with a colder surface. The cold surface cools the water vapor, causing it to condense into drops that collect on the surface of vents.
One of the most obvious signs is a puddle of water in your AC's drain pan, which proves the water isn't draining as it should. Other signs include: Standing water near your air conditioner's condenser unit. A moldy smell around the drain or from your system's vents and registers.
Causes of HVAC condensation
Poor ventilation can allow humidity levels to climb. A clogged or dirty air filter can hamper proper airflow. Clogged condensate drain lines or drain pan problems can lead to stagnant water and overflow.
Dirty evaporator coils and clogged air filters can hinder your air conditioner's ability to dehumidify the air. When the evaporator coil is dirty, it can't absorb heat and humidity as effectively. Similarly, a clogged filter restricts airflow, reducing the system's overall efficiency.
Use exhaust fans in bathrooms and kitchens to remove moisture to the outside (not into the attic). Vent your clothes dryer to the outside. Turn off certain appliances (such as humidifiers or kerosene heaters) if you notice moisture on windows and other surfaces.
Generally, it can take anywhere from 15 minutes to a few hours to significantly reduce humidity levels. For best results, the AC should run in cycles, with each cycle lasting at least 15-20 minutes. Short cycles may cool the air but won't run long enough to remove much moisture.