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Calculate savings before buying air conditioner |

Calculate savings before buying air conditioner

James Dulley
| Saturday, June 11, 2016 9:00 p.m
A variable-speed compressor can vary the cooling output from 25 percent to full maximum for excellent comfort.

Dear Jim: I should replace my noisy, old central air conditioner with a more efficient one. I want steadier room temperatures and humidity along with cleaner indoor air. What type of system do you recommend?

— Cyndee O.

Dear Cyndee: Your old central air conditioner probably has a SEER (seasonal energy efficiency ratio) of 10 at best. By replacing it with the most efficient new model with a SEER of 26, your electric bills savings can be about $2,500 over just five years.

These new systems also provide the steadiest room temperatures and excellent humidity control. Controlling indoor humidity level is as important for comfort as keeping the house cool. This also impacts the indoor air quality, particularly for people with allergies.

Consider replacing your old central air conditioner with a heat pump model. It is basically the same as a central air conditioner except it has a reversing valve to also produce heat. During mild weather, it heats at a lower cost than running a furnace. During colder weather, the furnace takes over.

Your three basic options are fully variable, two-level and single-level cooling output models. Because you are seeking high efficiency, steady room temperatures, humidity control, less noise and cleaner indoor air, a variable-output model is your best choice. It also is the most expensive system, so do a payback analysis first.

Variable-cooling models use variable-speed rotary compressors, which are often called inverter technology. They continually vary the cooling output to the instantaneous cooling needs of your house. The cooling varies in 1 percent increments, from about 35 percent to maximum output.

In early morning when cooling needs are low, the compressor slows to about one-third of its maximum output. It runs longer and more efficiently at this lower speed. These long efficient run cycles maintain room temperatures within just one-half degree of the thermostat setting.

These systems use a matching variable-speed blower. At the lower compressor speed, the indoor blower and outdoor condenser fans also run slower, making the entire system, indoors and outdoors, much quieter than single-level models.

When you set the desired humidity level on the thermostat, the blower speed automatically varies to control humidity. It can continue to dehumidify even when the room air is already cool enough. This eliminates that cool but muggy feeling, which may occur with a single-level system.

The next step down in comfort, efficiency (SEER in the 20 range) and initial cost is a two-level cooling system. This type of system runs at the more efficient low-output level the majority of the time. On hot afternoons or when you want quick cooling, it switches to the high-output level.

Single-level output models with a single-speed blower speed are the least expensive to install. Because they have only one cooling output level, you can expect a room temperature swing of about three degrees between run cycles.

Send inquiries to James Dulley, c/o Tribune-Review, 6906 Royalgreen Drive, Cincinnati, OH 45244; or visit

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