It is extremely important to choose a room air conditioner of proper cooling capacity. A unit with too much cooling capacity will be inefficient and expensive to operate. A unit that's too small won't do a satisfactory job. There is also a close relationship between cooling capacity and dehumidifying the air. An oversized unit will quickly cool the air without remaining in operation long enough to dehumidify it and a "cold, clammy" feeling will result.

Under the AHAM Certification Program the cooling capacity ratings are certified accurate in accordance with AHAM's Standard RAC-1. To make sure you choose the right size unit, use the Cooling Load Calculator. The result will be in Btu/h which can be found on the product packaging and also found in the AHAM Room Air Conditioner Certification Directory, available at your local dealer.

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After determining the size unit needed, consider its operating efficiency. An efficient room air conditioner uses less electricity so it costs less to operate. To measure efficiency, engineers have established a room air conditioner Energy Efficiency Ratio (EER). It is computed by dividing Btu/h (cooling output) by the watts of power (electrical input) in accordance with Department of Energy Test Procedures. Federal Trade Commission regulations require that this value be placed on the label attached to the product. Thus a 12,000 Btu/h model might use 1,900 watts and have an EER of 6.3 while another model of the same capacity might use 1,350 watts and have an EER of 8.8. The higher EER is the more efficient of the two. The Certification Directory lists EER's for all certified units.

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Check your home wiring for the right circuit amperage and voltage. Avoid lines already loaded with appliances. Do not connect a 208-V unit to a 115-V line or a 115-V unit to higher lines. If a fuse blows, shut off the unit and check load and wiring. Be sure the outlet is properly grounded. Never remove the grounding prong from the plug. Install the unit in a shaded window, if possible. Keep warm air out by weather stripping doors and windows and keeping them tightly closed. Close fireplace dampers and seal openings to the attic of other uncooled areas. Seek professional advice on recommended ceiling and wall insulation.

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• Turn off the unit and open doors and windows during cooler periods.

• Use the unit fan and portable fans to draw in cooler outside air and increase circulation.

• Although air conditioners also dehumidify, a dehumidifier in the basement can prevent excess moisture seepage through the house.

• Use a higher (warmer) thermostat setting during peak periods or when the area is unoccupied. A 75 to 80 degree setting will cut power consumption by 15%.

• Don't let heat build up all day and then try to cool areas quickly by turning the controls to maximum settings. Start units earlier in the day and cool areas slowly before they are occupied.

• Avoid activities that generate high heat and humidity (i.e.,cooking, bathing laundering) during high heat hours.

• Draw the shade or window blinds to reduce solar and outdoor heat. Reflecting and double pane glass, awnings, overhangs, louvered sunscreens, plantings, fences or adjoining building also help - but be sure you do not block the back of the unit.

• Regularly change or clean filters and check air flow for blockage or frost on evaporator coil.

• Use the vacuum cleaner attachment on accessible parts but be careful not to damage them.

• Have the unit checked and cleaned at the start of the season. During the off season, make certain it is cleaned and properly covered and disconnected.

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It's really up to you. First, you need to know how many BTUs you need to treat the air. You can do this by using the Cooling Load Calculator. Then, search and print a list of models that meet your cooling needs. You compare other features and benefits such as design and other functions by visiting the manufacturers' web sites.

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