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Buying a New Air Conditioner

The Department of Energy website gives advice on the purchase of a new air conditioning system. A Trane Comfort System is the finest product you can have in your home to meet your heating and cooling needs. However, there are hundreds of ways to install a comfort system, which is why an estimator from Integrity Air would prefer to meet all the adults in your home to find out your needs and quote you the best system at the best price.

FROM THE DEPARTMENT OF ENERGY WEBSITE (www.doe.gov)

Buying New Air Conditioners

Today's best air conditioners use 30% to 50% less energy to produce the same amount of cooling as air conditioners made in the mid 1970s. Even if your air conditioner is only 10 years old, you may save 20% to 40% of your cooling energy costs by replacing it with a newer, more efficient model.

Sizing Air Conditioners

Air conditioners are rated by the number of British Thermal Units (Btu) of heat they can remove per hour. Another common rating term for air conditioning size is the "ton," which is 12,000 Btu per hour.

How big should your air conditioner be? The size of an air conditioner depends on:

  • how large your home is and how many windows it has;
  • how much shade is on your home's windows, walls, and roof;
  • how much insulation is in your home's ceiling and walls;
  • how much air leaks into your home from the outside; and
  • how much heat the occupants and appliances in your home generate.

An air conditioner's efficiency, performance, durability, and initial cost depend on matching its size to the above factors.

Make sure you buy the correct size of air conditioner. Two groups—the Air Conditioning Contractors of America (ACCA) and the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE)—publish calculation procedures for sizing central air conditioners. Reputable air conditioning contractors will use one of these procedures, often performed with the aid of a computer, to size your new central air conditioner.

Be aware that a large air conditioner will not provide the best cooling. Buying an oversized air conditioner penalizes you in the following ways:

  • It costs more to buy a larger air conditioner than you need.
  • The larger-than-necessary air conditioner cycles on and off more frequently, reducing its efficiency. Frequent cycling makes indoor temperatures fluctuate more and results in a less comfortable environment. Frequent cycling also inhibits moisture removal. In humid climates, removing moisture is essential for acceptable comfort. In addition, this cycling wears out the compressor and electrical parts more rapidly.
  • A larger air conditioner uses more electricity and creates added demands on electrical generation and delivery systems.

Air Conditioner Efficiency

Each air conditioner has an energy-efficiency rating that lists how many Btu per hour are removed for each watt of power it draws. For room air conditioners, this efficiency rating is the Energy Efficiency Ratio, or EER. For central air conditioners, it is the Seasonal Energy Efficiency Ratio, or SEER. These ratings are posted on an Energy Guide Label, which must be conspicuously attached to all new air conditioners. Many air conditioner manufacturers are participants in the voluntary EnergyStar® labeling program (see Source List in this publication). EnergyStar-labeled appliances mean that they have high EER and SEER ratings.

In general, new air conditioners with higher EERs or SEERs sport higher price tags. However, the higher initial cost of an energy-efficient model will be repaid to you several times during its life span. Your utility company may encourage the purchase of a more efficient air conditioner by rebating some or all of the price difference. Buy the most efficient air conditioner you can afford, especially if you use (or think you will use) an air conditioner frequently and/or if your electricity rates are high.

Central Air Conditioners—SEER

National minimum standards for central air conditioners require a SEER of 9.7 and 10.0, for single-package and split-systems, respectively. But you do not need to settle for the minimum standard—there is a wide selection of units with SEERs reaching nearly 17.

Before 1979, the SEERs of central air conditioners ranged from 4.5 to 8.0. Replacing a 1970s-era central air conditioner with a SEER of 6 with a new unit having a SEER of 12 will cut your air conditioning costs in half.

Choosing a Contractor

Choosing a contractor may be the most important and difficult task in buying a new central air conditioning system. Ask prospective contractors for recent references. If you are replacing your central air conditioner, tell your contractor what you liked and did not like about the old system. If the system failed, ask the contractor to find out why. The best time to fix existing problems is when a new system is being installed.

When designing your new air conditioning system, the contractor you choose should:

  • use a computer program or written calculation procedure to size the air conditioner;
  • provide a written contract listing the main points of your installation that includes the results of the cooling load calculation;
  • give you a written warranty on equipment and workmanship; and
  • allow you to hold the final payment until you are satisfied with the new system.

Avoid making your decision solely on the basis of price. The quality of the installation should be your highest priority, because quality will determine energy cost, comfort, and durability.

Installation and Location of Air Conditioners

If your air conditioner is installed correctly, or if major installation problems are found and fixed, it will perform efficiently for years with only minor routine maintenance. However, many air conditioners are not installed correctly. As an unfortunate result, modern energy-efficient air conditioners can perform almost as poorly as older inefficient models.

Be sure that your contractor performs the following procedures when installing a new central air conditioning system:

  • allows adequate indoor space for the installation, maintenance, and repair of the new system, and installs an access door in the furnace or duct to provide a way to clean the evaporator coil.
  • uses a duct-sizing methodology such as the Air Conditioning Contractors of America (ACCA) Manual D.
  • ensures there are enough supply registers to deliver cool air and enough return air registers to carry warm house air back to the air conditioner.
  • installs duct work within the conditioned space, not in the attic, wherever possible.
  • seals all ducts with duct mastic and heavily insulates attic ducts.
  • locates the condensing unit where its noise will not keep you or your neighbors awake at night, if possible.
  • places the condensing unit in a shady spot, if possible, which can reduce your air conditioning costs by 1% to 2%.
  • verifies that the newly installed air conditioner has the exact refrigerant charge and air flow rate specified by the manufacturer.
  • locates the thermostat away from heat sources, such as windows, or supply registers.

If you are replacing an older or failed split system, be sure that the evaporator coil is replaced with a new one that exactly matches the condenser coil in the new condensing unit. (The air conditioner's efficiency will likely not improve if the existing evaporator coil is left in place; in fact, the old coil could cause the new compressor to fail prematurely.)

Courtesy of "Trane" 

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