In air conditioning operation, the compressor in your outdoor unit pushes the liquid refrigerant through copper tubing into the evaporator coil located in your fan coil unit or attached to your furnace. As the refrigerant is compressed, it turns into a gas. When it moves through the evaporator coil, the refrigerant takes on heat from the air circulating over the coil. The cooler air is then recirculated into your home. Meanwhile, the heat absorbed by the refrigerant is carried outside through the copper tubing and given off to the outside air as a fan pulls the air over the condensing coil in your outdoor unit.
While it's keeping you cool, your air conditioner also works as an effective dehumidifier. As warm air passes over the indoor evaporator coil, it can no longer hold as much moisture as it carried at its higher temperatures. The extra moisture condenses on the outside of the coils and is carried away through a drain. The process is similar to what happens when moisture condenses on the outside of a glass of ice water on a hot, humid day.
