Central air conditioning systems usually have two main components — the condenser, a large unit typically mounted on a concrete pad outside the home; and an evaporator, usually installed on a forced-hot-air furnace or adjacent ducting, to take advantage of the heating system’s blower motor. Both of these components need regular cleaning to keep the home environment clean and to save energy.

 

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Condenser: The outside unit must be kept free of vegetation, leaves, grass clippings, or anything else that will impede airflow. At least once a year, shut off power to the unit — building codes in many jurisdictions require a shutoff switch to be mounted within easy reach — and remove the cover. Gently brush dust and dirt away from the aluminum fins surrounding the coil (or vacuum the fins with a brush attachment), being careful on two fronts: The fins are easily bent out of shape, which will reduce efficiency, and the edges of the fins can be very sharp and will cut exposed skin quickly.

 

Soap, harsh detergent or ammonia should not be used on the fins, but spraying a mild all-purpose cleaner between them will help remove surface soil. Then use a garden hose to “backwash” any remaining dirt from the inside of the fins and coil toward the outside.

Evaporator: Shut off power to both furnace and air conditioner. Gaining access to this component requires opening one or more panels on the furnace or ductwork. As with the condenser, be careful of the aluminum fins while cleaning them with a stiff brush. The condensation tray located under the coil may be cleaned with a 1:4 mixture of chlorine bleach and water to kill mold and mildew; use a soft brush or white nylon pad to dislodge stubborn deposits. If necessary, use a stiff wire to clear a plugged drain hole or drain line leading away from the tray. The drain line should be flushed once a year and a chlorine bleach solution poured through it to minimize algae growth.

 

To avoid injury, wear long sleeves and work gloves while cleaning the fins on both the condenser and evaporator.

 

Clean and/or replace filters at least monthly during the cooling season.