Air Conditioner Filters

The most important maintenance task that will ensure the efficiency of your air conditioner is to routinely replace or clean its filters. Clogged, dirty filters block normal airflow and reduce a system's efficiency significantly. With normal airflow obstructed, air that bypasses the filter may carry dirt directly into the evaporator coil and impair the coil's heat-absorbing capacity. Filters are located somewhere along the return duct's length. Common filter locations are in walls, ceilings, furnaces, or in the air conditioner itself.

Some types of filters are reusable; others must be replaced. They are available in a variety of types and efficiencies. Clean or replace your air conditioning system's filter or filters every month or two during the cooling season. Filters may need more frequent attention if the air conditioner is in constant use, is subjected to dusty conditions, or you have fur-bearing pets in the house. If you use a disposable type filter, it's always wise to keep several spares inside the house.

An enormous waste of energy occurs when cooled air escapes from supply ducts or when hot attic air leaks into return ducts.

Recent studies indicate that 10% to 30% of the conditioned air in an average central air conditioning system escapes from the ducts.

Sealing and Insulating Air Ducts

For central air conditioning to be efficient, ducts must be airtight. Hiring a competent professional service technician to detect and correct duct leaks is a good investment, since leaky ducts may be difficult to find without experience and test equipment. Ducts must be sealed with duct "mastic." The old standby of duct tape is ineffective for sealing ducts.

Obstructions can impair the efficiency of a duct system almost as much as leaks. You should be careful not to obstruct the flow of air from supply or return registers with furniture, drapes, or tightly fitted interior doors. Dirty filters and clogged evaporator coils can also be major obstructions to air flow.

The large temperature difference between attics and ducts makes heat conduction through ducts almost as big a problem as air leakage and obstructions. Ducts in attics should be insulated heavily in addition to being made airtight.

Outside dirt, leaves, grass and other debris clog the condenser coils, straining the system.

Once a month, inspect the outdoor unit to insure that nothing is obstructing the airflow across the coil. Remember, before you do any work on your condenser unit to turn off the power at the disconnect switch mounted on the wall near the unit. If you don't have a disconnect switch, turn off the breaker. If you find that your unit is becoming dirty, you can follow the procedures below.

Performing Outside Maintenance

After disconnecting the power, if leaves or other debris have collected inside the condensing unit, open the unit by undoing the screws on the top panel and tipping it up. Remove any debris from the enclosure. Then, reverse the procedure insuring the screws are replaced before restoring power. Do not open the electrical panel cover. This is best left to a certified technician.

Check to be sure your compressor unit is level. An unleveled unit will be nosier, less efficient, and cause excessive wear. Check the level in both directions, making adjustments if necessary. Be careful how much you move the unit. It has rigid connections to the electrical and refrigerant lines. Too much (and it doesn't take much) movement could cause a refrigerant leak to occur.

Finally, check the condensate line for a bacterial slime that tends to grow in condensed water. The condensate line is the drain that removes water that has condensed from your indoor coil. Pour a 1:9 bleach-and-water solution through the line. Find the fitting for the hose, pull it out, and flush the line all the way to the floor drain. If the drain is difficult to reach, you may be wiser to call your HVAC contractor to do the job.
Always be careful when using lawn mowers and trimmers around your condensing unit. Flying debris can damage the coil and fins.