Dear Jim: I am ready for a new, quieter and more efficient central air conditioner. My old one doesn’t always keep the house comfortable. It feels clammy in here sometimes. What should I look for in new models? – Ronnie L.

Dear Ronnie: You have picked a good year to replace your central air conditioner. There have been some significant changes and improvements in the most efficient and comfortable models for 2003. Also, sound levels have been seriously addressed and they are much quieter, indoors and outdoors.

This year, the efficiencies, or SEER, have skyrocketed to more than 19 and the comfort level is improved. If your existing air conditioner is older than 10 years, installing a new one will cut your cooling electric bills by more than 50 percent. Depending on your climate, it can provide a quick payback.

These high-efficiency models also provide the best comfort, particularly during the milder weather of early and late summer. This is when you often sense that clammy feeling. The indoor air gets cool enough, but the air conditioner has not run long enough to also adequately dehumidify the air.

Using a two-stage compressor and a multispeed condenser fan, these models fine-tune the cooling output to the cooling needs of your home. During mild weather, they operate in the slow, superefficient stage with reduced cooling output. In this slow stage, they run longer and dehumidify better.

There are several designs of two-stage compressors. Some use a two-piston compressor. When it rotates in one direction, only one piston moves. When the rotation reverses, both pistons move to double the cooling. Another design uses a two-speed compressor.

Some models use two small compressors. These run on only one compressor except for very hot days with high cooling needs.

The newest design (brand new in 2003) is a two-stage scroll compressor. A scroll compressor has very few moving parts and operates quietly. This new two-stage scroll uses ozone-friendly R410A refrigerant. Compressors using old freon R-22 gradually will be phased out of production by law by 2010.

Models that use R410A instead of freon tend to operate quieter. R410A requires higher operating pressures, so the tubing and materials must be made stronger. This changes the sound frequency, making it less annoying. Many other sound-deadening design changes also are used now.

Whether you choose a super-efficient two-stage or a lower-priced one-stage model, consider replacing the indoor air handler (furnace) with one using a variable-speed blower. This will increase the year-round (heating too) efficiency and comfort level with much less indoor noise. Also install a new compatible thermostat that controls cooling and humidity independently.

Write for (instantly download – www.dulley.com) Update Bulletin No. 533 – buyer’s guide of the 19 most efficient one- and two-stage central air conditioners listing cooling outputs, SEERs, comfort features, warranties, and a savings chart. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.