Up-to-Date Air Conditioner May Save Energy
QUESTION: Even though my old central air conditioner still works, does it make economic sense to replace it with a new one? It does not cool enough on the hottest days. What is new for 1997 and what features are best?
ANSWER: New central air conditioners have been peaking at seasonal energy efficiency ratios of 15 to 16 for the last couple of years. Your old one probably had a ratio of 8 when it was new. Installing a new one can cut your cooling bills in half.
The most significant improvements in the last year have been in comfort, improved indoor air quality (especially for allergy sufferers) and reduced noise at super-high efficiency levels.
A more stable indoor temperature and better air quality allow you to set the thermostat higher without sacrificing comfort. Each degree that you raise the thermostat can cut your electric bills 2% to 3%.
For the greatest efficiency and comfort, select a three-cooling-stage central air conditioner. This provides three cooling output levels to match the varying cooling needs of your house throughout the day and night. There is also a new natural gas-powered model, Triathlon, with 17 output levels.
Some new units have two different-size compressors in the outdoor unit. When the outdoor air temperature is below 88 degrees, it starts on the small compressor. During this mild weather, it runs longer on the small compressor for better dehumidification, air cleaning and air circulation.
When the outdoor temperature is above 88, it switches to the large compressor. On very hot days, when neither compressor alone can cool your house adequately, they both run for maximum cooling.
Other multistage designs use a two-speed compressor instead of two separate compressors. These are effective in high humidity climates with varying summer weather conditions. You can expect to pay about 25% to 30% more for these units than for a standard single-stage unit.
Variable-output units are most effective with variable-speed indoor blowers. The blower speed automatically changes to match the cooling output required.
Lower-cost single-stage units also have ratios up to 15 for significant electricity savings. They provide satisfactory comfort, especially in dry, hot climates. In humid climates, consider installing a dehumidification kit. It has a humidistat to control the blower speed for more moisture removal.
Single-stage units with scroll compressors are quiet and reliable. Scroll compressors use few moving parts with no reciprocating pistons, valves, etc.
Write for (or instant download at https://www.dulley.com) Update Bulletin No. 624, which lists the 20 most efficient three-, two- and single-stage central air conditioners, cooling outputs, energy-efficiency ratings, blower speeds, comfort features and payback chart. Please include $2 and a business-size self-addressed stamped envelope and mail to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.
Protect Children From Open Windows
Q: I try to use natural ventilation as much as possible, but I am afraid that my young children will break through the screens. Are there any tips to protect them with the windows opened?
A: Your concern is justified. Thousands of children are hurt each year because of falling from windows. Even the strongest fiberglass solar screens are not designed to stop a determined child from breaking through it.
First, use safety bars on all windows except ones used for emergency exits. Never open windows more than a few inches and use some type of positive stop on it. Opening them just a few inches provides adequate ventilation.
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Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244; or for instant download: https://www.dulley.com.
