New Air Conditioners More Energy-Efficient
QUESTION: I must replace my old central air conditioner soon. I want one that is super-high-efficiency, reliable and quiet. What types of units are available to meet my needs?
ANSWER: There have been many recent significant improvements in residential-sized central air conditioners. Some of the new super-high-efficiency central units have efficiencies (called SEER) as high as 17. Installing one of these can cut your cooling bills by more than 50%.
The most energy-efficient central air conditioner uses a totally variable speed compressor and fan. This allows the unit to operate at maximum efficiency for varying cooling needs and weather conditions. On very hot days, it operates at a higher speed than on cooler days. An electronic microprocessor determines the most efficient operating speed.
Since it doesn’t cycle on and off as often, the more steady-state operation improves the efficiency and your comfort. The cooling output and air circulation are more constant throughout your home. It also operates more quietly at the lower speeds.
Central air conditioners with two-speed compressors are also available with SEERs up to 15. (Your old single-speed air conditioner probably has a SEER of only 6 to 7). Another unit has a single-speed compressor, but a two-speed condenser fan to boost efficiency to more than 12.
The scroll compressor design is now used in many of the super-high-efficiency air conditioners. Its advantages are its quiet operation, high efficiency and simplicity. The noise levels from a scroll compressor can be 10% to 20% lower than from a standard reciprocating compressor.
With only a few moving parts, a scroll compressor is less prone to mechanical and lubrication breakdown. This makes it very reliable, and it actually becomes more efficient the older it gets as it wears in.
When you select a central air conditioner, it is important to have it properly sized. Your contractor should do a detailed heat gain analysis of your house and economic pay-back analysis for units of various efficiencies.
An oversized unit not only operates inefficiently by cycling on and off too often, but it decreases the comfort level. In all but the very hottest weather, it won’t run long enough to adequately dehumidify the air. This is where the variable- and multiple-compressors help.
You can write for Utility Bills Update No. 394 showing a buyer’s guide for 21 manufacturers of super-high-efficiency central air conditioners, listing models, cooling capacities, rated efficiencies, sound levels, types of compressors and numbers of speeds. Please include $1.25 and a business-size return envelope. Send your requests to James Dulley, c/o Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.
Should Damper in Fireplace Be Closed?
Q: I have a wood-burning fireplace with a brick chimney on the west side of the house. When I air condition in the summer, should I close the chimney damper or leave it open for natural ventilation?
A: If you are operating a central air conditioner, you should keep the chimney damper closed. The brick chimney holds the sun’s heat well into the evening. This creates an upward draft and draws out cooled air.
If you don’t air condition, leave the chimney damper open. The natural draft from the warm chimney draws cool outdoor air in the windows at night. It is actually a form of free solar energy replacing an electric fan.
