A/C Capacity Measured in Tons? Here’s the Story
If you’re having a new air conditioning system installed in your Orlando area home, and your HVAC technician says your home requires a three-ton A/C, you may be surprised at the need for such a heavy piece of equipment. The fact is, in air-conditioning parlance, the word “ton” is a measurement of A/C capacity, not the weight of the equipment. A three-ton A/C unit doesn’t weigh three tons but, rather, is capable of providing approximately three tons of cooling capacity per/hour. Here’s the story.
More than 100 years ago, when blocks of ice were used to keep food cold, they were also used to provide a basic type of air conditioning in homes/businesses. With Willis Carrier’s 1902 invention of the first modern-day air conditioner, ice blocks were no longer needed to cool indoor air. To measure A/C capacity, however, the relative cooling power of ice blocks was adopted as a measurement and continues to be used today.
A block of ice cools its surroundings by absorbing heat until eventually melting to water. It’s been determined that, during this melting process, a one-pound block of ice will absorb a total of 143 BTUs (British Thermal Units) before melting completely. One BTU is equal to about the amount of heat produced by burning a single kitchen match.
Carrying out this calculation further, one ton (2,000 pounds) of ice will absorb 143 x 2,000 BTUs before completely melting. That’s a total of 286,000 BTUs. A one-day time period is used to factor total cooling capacity. Dividing 286,000 BTUs by 24 hours then gives the per/hour figure, which is 11,917. This was rounded up to 12,000 BTUs, which now expresses the A/C capacity of a one-ton unit. If your HVAC technician is recommending a three-ton A/C system, he’s likely determined by his Manual J calculations that your cooling load is 36,000 BTUs per/hour.
Founded in 1969, Rinaldi’s Energy Solutions, located in Orlando, is a community-based, family-owned business proudly serving Central Florida. For expert A/C advice, sales and service, contact the professionals at Rinaldi’s.