Condensation in Duct Work: My Air Conditioner Is Not Working

Condensation in the System

• Central air conditioners produce condensation as a byproduct of their cooling method due to the humidity in the air. Air conditioners pull air in from the home, through a filter, and blow it across cold copper coils filled with refrigerant. These coils "sweat" the humidity in the air just as a cold glass of water sweats in a hot room. This sweat, or condensation, is drained from the coils and dumped outside the home, thereby reducing indoor humidity and improving comfort.

Dirty Filter

• One potential cause of condensation in a central air conditioner's ductwork is a dirty filter. When a filter becomes clogged with dirt and debris, the air conditioner cannot pull in sufficient air to keep the system cycling and running efficiently. The air that is expelled from the system, through the ducts and registers, is therefore more humid than it should be. Over time, condensation can build up in low points in the duct work and even drip from registers. Clean or replace the filter and dry the ductwork, replacing any ducts that show signs of mold or mildew growth.

Clogged Condensation Pan

• The condensation pan that catches water dripping from the coolant coils can become clogged, which frequently happens when an air conditioner has not been serviced recently or when it has been run without a filter for a prolonged period. Hair and other debris from the home clog the pan and do not allow water to drain, reducing the air conditioner's ability to dehumidify and leading to humid air being circulated back into the home. Clean the pan and ensure it is draining properly before turning your unit back on.

Failing Condensation Pump

• The condensation in the condensation pan is pumped to a floor drain or outside gutter by way of a condensation pump, which turns on when water is present in the condensation pan and pushes it out through a length of PVC or hose and safely away from the system. If the condensation pump is not functioning, or is beginning to fail, water may be backing up in the condensation pan with no obvious sign of a clog. Pour some water into the condensation pan to see if it drains away. If it does not, and the pump does not power on, it needs replacing.