How to Determine the Tonnage of a Central Air Conditioning Unit

Rather than listing central air conditioners' cooling capacity in terms of total tonnage -- the amount of power it would take to melt a ton of ice in 24 hours -- manufacturers rate an air conditioner total British thermal units or BTUs. Calculating your unit’s cooling capacity in terms of tons, based on its BTU rating, requires simple division. To determine your central air conditioner's BTU rating, you’ll need to locate the unit’s model number and determine which number indicates BTUs. Finding that number is fairly simple, since the cooling capacity in most units is represented by figures at set intervals.

Instructions

1. • 1

     Locate the model number on the face of your central air unit. The model number typically appears on the left side of the front plate. It is usually a combination of letters and numbers.

   • 2

     Look for a number that indicates the unit’s BTUs. The BTUs of a central air unit is almost always hidden within the model number itself. Look for a number that is greater than or equal to 24, in intervals of six. Most central air units start out at 24,000 BTUs and increase in intervals of 6,000. So 24 would equal 24,000 BTUs.

   • 3

     Divide the unit’s BTUs by 12,000 to find the air conditioner's cooling capacity in terms of tons.