Will a Clogged Condensate Drain Cause Loss of Cooling?

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If your air conditioner shuts off automatically and you can't seem to restart it, there's a good chance that the problem might lie with the condensate drain. These drains carry moisture away from the air conditioner unit. A clogged consensate drain needs to be cleared as soon as possible, as it may contribute to a loss of cooling.

Air Conditioner Operation

Air conditioners consist of two main parts: the evaporator and the condenser. The two parts are connected by a series of pipes. Coolant flows from the condensor to the evaporator. On the way to the evaporator, the coolant passes an expansion valve. This valve causes the coolant to expand into gas. This has the effect of immediately lowering the temperature in the surrounding area. The coolant is then pumped into the condenser, where it is compressed back into liquid and starts the cycle again.

Evaporator Drain

As the coolant expands in the evaporator, it also causes the moisture in the air to condense. This moisture, in the form of water, drips down into a the drain pan located beneath the evaporator. A drain connects the drain pan to the outside of the building where the air conditioner is installed. This drain is called the evaporator drain or the condensate drain.

Loss of Cooling

A clogged evaporator drain won't cause a loss of cooling directly, but it can sometimes trigger devices that automatically switch off the air conditioner. Many condensate drain pans are equipped with a float switch. When the water in the drain pan rises to a certain level, which would happen if the drain was clogged, the water triggers the switch to turn off the air conditioner. The purpose of this is to prevent damage to the building from an overflowing condensate drain pan.

Clearing a Clogged Condensate Drain

If the drain entrance is below water in the drain pan, run your hand along the sides of the drain pan to locate the opening. Insert a length of plastic tubing into the drain pipe long enough to reach to the drain exit. Push the tubing back and forth against the clog when you feel it with the tubing until it breaks up. The drain pan should clear after the clog is removed. Mix a capful of bleach with a pint of warm water and pour this down the drain opening to kill any bacteria inside.


Nathan McGinty

Nathan McGinty started writing in 1995. He has a Bachelor of Science in communications from the University of Texas at Austin and a Master of Arts in international journalism from City University, London. He has worked in the technology industry for more than 20 years, in positions ranging from tech support to marketing.