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 Central Air Conditioning

When it comes to home appliances, air conditioners are at the top of the list of improvements in energy efficiency over the past decade. The newer units allow you to remain comfortably cool in hot weather and save you money. If your air conditioner is more than 10 years old, there is a good chance that it is inefficient and should be replaced. New models are expected to last 15 years or longer and are twice as efficient as those made only 10 years ago. Moreover, if your current system is in need or repair, it is likely more cost efficient, as well as more energy efficient, to replace your system with a new one.

Central air conditioning is rated different from most other appliances. They will still have an EnerGuide label, but rather than listing a kWh rating (or some variation thereof), air conditioners use a SEER (Seasonal Energy Efficiency Rating). These rating typically range from 10-17 on new units. The higher the number on the unit, the more efficient it is. Older units have very low ratings when compared to new models. The average rating for an air conditioner manufactured prior to 1992 is approximately 6.0. Government regulations have mandate a minimum SEER of 13.

ENERGY STAR models are of course the most efficient models available, with 25% of the most efficient models carrying the ENERGY STAR label. In order for a unit to qualify for the label, split system models must have a minimum SEER of 13, as well as a minimum Energy Efficiency Ratio (EER) of 11.5 for split systems, while packaged systems must have a SEER of at least 12 and an EER of 11.00. Models with the highest SEERs will almost always have a variable-speed or a two-speed high-efficiency compressors.

Central air conditioning is part of the Heating, ventilation and air conditioning (HVAC) system. Central air conditioning flows through ducts and is distributed evenly throughout the home. Generally speaking, central air conditioning units go hand in hand with a gas or oil furnace to provide heat through the same ducts.

Typical air conditioning units use a “split system” that uses and outdoor condenser and an indoor evaporator coil. The air conditioner’s job is to remove heat from the inside of the home and transfer it outside, leaving cooler air to be recalculated through the ducts by a fan.

The air conditioner unit changes the refrigerant within from a gaseous state to a high temperature, high-pressure gas. As it flows through the outdoor coil, it loses heat and condenses the refrigerant to a high temperature high pressure liquid that flows through piping connected to the evaporator coil and expands to a low temperature, low pressure gas. The gas absorbs the heat from the air in the ducts, leaving the cooler air behind to be redistributed through your home. The remaining low temperature, low pressure gas returns to the compressor and begin the process all over.

In addition to cooling, central air conditions also dehumidify. The warm air passing over the evaporator coil is unable to hold as much moisture as it carried at a higher temperature prior to being cooled. Extra moisture condenses; similar to condensation on a cool glass on a warm day, and exits through a drain.

In addition to the “split system,” there are also packaged systems that combine the condensing unit and evaporator coil into a single outdoor unit. The principles in the above information still apply. The type of home you live in and its location will determine what type of system you use.

For more ways to save energy with central air conditioning, see the list of tips below.

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 Central Air Conditioning Tips
Make use of a programmable thermostat
Purchasing a programmable heater will allow you to automatically adjust the temperature while you are at work, when you are sleeping and while you are on vacation. Adjusting the thermostat by just 2 degrees can save a ton of CO2 each year.
Use ceiling fans to conserve energy
Use ceiling fans to circulate air and keep cool in the summer. Reverse the fan in the winter to push warm air down and conserve heat.