The Air Conditioner

by Don Ames

The Air Conditioner

How Much Cooling Capacity do you need?

          How Much Space can a Ton of Cooling Capacity Serve?

from Inspectapedia.com

Maybe 450 sq.ft. to 1000 sq.ft. of a typical home can be cooled per ton of cooling capacity: that is, one ton (or 12,000 btuh) of air conditioning can cool about 500 sq.ft. of space. Sketch courtesy of Carson Dunlop

But the real answer is, it depends. Some of the factors that affect the ability of an air conditioner to cool a space need to be considered besides just the number of square feet. These include at least the following questions about air conditioning load and cooling requirements:

  • What are the sun and heat characteristics of the geographic area where the building is located (southern U.S. vs. northern U.S. or Canada, for example)?
  • How much direct sunlight is falling on the building?
  • Is it bright hot sun or only partly sunny?
  • What are the exterior colors of surfaces on which sunlight is falling?
  • How well the building is insulated?
  • How drafty is the building?
  • How many occupants are in the building?
  • What other heat sources (or cooling sources) are in the building?
  • How high are the interior ceilings?
  • How does air circulate within the occupied spaces?
  • What defects in the air conditioning system need to be overcome, such as duct system errors or damage, dirty filters, blocked cooling coils, etc. ?

Do not buy an air conditioner which is oversized (too many BTUh) for the area you need to cool. You may think that bigger is better, but not in the case of air conditioning.

To make a room comfortable the air conditioner needs to both cool the room air AND dehumidify the room air. If the air conditioner is too large for the space to be cooled, the temperature will drop quickly and the A/C unit will shut off before the air has become adequately dry.

Typical BTU Cooling Capacity Range for Air Conditioners

Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for:

Single Room Air Conditioner Capacity – typically for rooms up to 20′ x 20′ or 400 sq.ft. in area. BTUs in this product range are typically from 6,000 BTUh to 10,000 BTUh.

Portable room air conditioners – 7,500 to 14,000 BTUH, portable, using one or in some cases two flexible ducts to move heat from the room, through cooling coil and the compressor, to outdoors

Multiple Room Air Conditioner Capacity – typically for a total area of up to 800 sq.ft. BTUs in this product range are typically from 10,000 BTUh to 16,000 BTUh.

Large Capacity Air Conditioner Capacity – typically for multiple rooms or very large rooms up to a total area from 900 sq. ft. to 2,000 sq.ft. BTUs in this product range are typically from 16,000 to 28,000 BTUh.

Central Air Conditioning – typically to cool an entire floor or multiple floors in a home. Also see A/C TYPES, ENERGY SOURCES