One of the basic functions of an air conditioner is to remove moisture from the air. Water retains heat, so taking some of it from the home's atmosphere helps the appliance cool the space. Sometimes, though, it's still too moist in your home even after your A/C unit has been running most of the day. Here are three reasons why this happens and what you can do to fix the problem.
The Unit is Oversized
An improperly sized air conditioner is one common reason why a house may remain humid even though the unit appears to be blowing out cold air. The issue with oversized air conditioners is they cool the house too fast. Removing water from the air takes time, and the machine needs to stay on long enough (e.g., about 20 to 30 minutes or 2 to 3 cycles per hour) to make a difference in the humidity level. However, an oversized air conditioner may only run for half that time (e.g., 10 to 15 minutes) to get to the desired temperature; after which it shuts off, leaving you with a cool but clammy house.
A sure sign your air conditioner is too big is the number of times it cycles on and off in a given time period. If it's more than 3 times an hour, there may be an issue. More frequent repairs can also indicate a bigger-than-needed machine. Rapid cycling causes parts to wear out faster, leading you to repair and replace them more often than is commonly necessary. Lastly, oversized air conditioners use up more energy, so your electricity bills may be higher than normal for a house your size during hot months when you're more likely to use the A/C.
The only long-term solution for an oversized air conditioner is to swap it out for something more appropriate. If it's not time to replace your A/C, the alternative is to use a dehumidifier to supplement your unit's efforts.
Too Much Outside Air Being Drawn In
A second reason for high humidity in an air-conditioned home is that too much air is being pulled in from the outside. This is actually caused by excessive negative pressure in the space, which is the result of poor ventilation and/or leaks. For one reason or another, too much air is expelled from inside the home, creating a negative pressure environment. To obtain equilibrium, more air is drawn in from the outside from every available opening, which mixes with the already treated air inside. The result is muggy exterior air increasing the water content of interior dry air.
Negative pressure in a residential home is most often caused by either the kitchen hoods or the dryer, both of which expel air outside the house. When there's negative pressure in your house, there may be back drafting of the hot water heater or furnace, mold or mildew may form around the window sills, and the air may seem stagnant or stale. If your home appears to be sucking in air every time you open a door or window, you may have a pressure issue.
To fix this problem, it's critical to have an expert inspect your ventilation system to figure out what is causing it.
Leaving the Fan On
Many people leave the fan blowing on their air conditioning units with the hope it will continue to circulate the cold air in the house. While the machine's fan is fairly effective at this, it can also blow all the moisture the air conditioner extracted from the home back into the space before the water has a chance to drain away.
If you want to circulate air in your home, use a ceiling or regular fan. Alternatively, only run your air conditioning fan for short periods of time throughout the hottest parts of the day.
For more information about this issue or to get your air conditioner repaired, contact an air conditioning contractor.