Air conditioners

Hardware Retailing, August, 2006

Window-mounted air conditioners cool, circulate, filter and dehumidify the air. They range in size from small units with a cooling capacity of 5,000 BTUs (enough to cool a small room) to as high as 14,000 BTUs for normal home voltage.

It is crucial that retailers sell the consumer the right size air conditioner. An oversized unit will cool but leave a damp and clammy feeling because of high relative humidity. An undersize unit will not operate effectively on very hot days.

An air conditioner should always be selected by BTU rating, not horsepower. Horsepower is just the size of the motor driving the compressor; BTU is the actual cooling capacity of the unit.

An effective rule of thumb to determine the BTUs needed to cool a room is to multiply the square feet of the room by 25, adding 1,000 for every window and 400 for each occupant. Example: A room measures 12' x 15' with two windows and two occupants. The formula works out to 180 sq. ft. x 25 = 4,500 + 2,000 for the windows + 800 for the occupants = 7,300, or a 7,000-8,000 BTU air conditioner.

The U.S. Department of Energy has established minimum efficiency standards for air conditioners. Every unit is given an efficiency rating, called a SEER (Seasonal Energy Efficiency Rating), which is listed on the yellow Energy Guide label posted on each unit. The higher the number, the more efficient the unit.

The minimum allowable SEER rating for new central air conditioners used to be 10, but that has changed to 13 as of January 2006. The most efficient models have SEERs of 15 to 17.

Units with 115 volts (having less than a 9,000 BTU capacity) will not overload average house wiring. For larger capacity units and those requiring 220V wiring (high BTU capacity), an electrician should be consulted.

Mounting kits are included with most models, including sill brackets for extra support of the unit and side panels to ensure an airtight fit in the window. For maximum cooling efficiency, a window unit should be placed in a window that will afford maximum air circulation into the room or rooms to be cooled and is shaded most of the time.

Split ductless air conditioners are another option, although they are designed more for whole-house cooling.

There are several energy-saving points that should be emphasized to consumers. The filter should be cleaned periodically, or cooling efficiency will be sharply reduced. Most units are permanently lubricated and require no oiling; advise customers to follow manufacturer's instructions on this point.