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How Can I Determine How Many Tons My Air Unit Is?

The size of a central air conditioner can be expressed in tonnage. One ton of cooling capacity is the amount of energy required to melt 1 ton of ice, which is equal to 12,000 British thermal units (BTUs). You can decode your air conditioner's size from its model number. This information is also included in the owner's manual, or you can look up the model number of your AC on the manufacturer's website to determine the size.

  1. Decode the tonnage of your air conditioner from its model number. The number is listed on a thin metallic sheet stamped on the compressor, the unit outside your home. The model number consists of a series of letters and numbers. Look for any of the following multiples of 12: 12, 18, 24, 36, 48 or 60. Divide the number you find by 12. For example, if the number is 18, dividing by 12 will show that the air conditioner is a 1.5-ton model.

  2. Look in the owner's manual of the AC unit to determine its cooling capacity. In the section that lists the unit's features, you will find the cooling capacity in BTUs -- for example, 18,000 or 24,000 BTUs. Divide the number by 12,000 to determine the tonnage.

  3. Enter your air conditioner's model number in the search box on the manufacturer's website and pull up the online documents related to your AC. Look up the unit's size in these documents, dividing by 12,000 if the capacity is listed in BTUs.

About the Author

Riz Khan started writing professionally in 2005. He has written for IT blogs, such as AddictiveTips. He owns a blog where he shares information, tips and tricks relating to IT, PDAs and graphics software. Khan has a diploma in digital media arts from Seneca College. He is currently enrolled in a bachelor's program in computer information systems at Yorkville University.