How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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What is a ton of air conditioning?
Friday, August 10, 2018
It is a measurement of capacity that equals the cooling accomplished by melting one ton of ice per day, and is a holdover from the era when refrigeration was transitioning from stored natural ice to mechanical refrigeration. But the ton is still used today in North America as a shorthand way of expressing the size of an air conditioning system, similar to the use of horsepower, another archaic term, to rate car engines.
The rest of the world uses the BTU (British Thermal Unit) as the standard measurement, and a ton is equal to 12,000 BTU. The advantage of the BTU is that it’s more accurate and universally used, but the ton persists.
Most residential air conditioning systems are between 1.5 and 5 tons, measured in half-ton increments; except that there is no 4.5 ton size available. So a 2-ton system is 24,000 BTU, for example, and a 3.5 ton is 42,000 BTU. A system rated at 2.5 tons may a little over or under 30,000 BTU and still be considered “two-and-a-half-tons.”
The first two digits of the BTU rating is typically embedded in the model number on the manufacturer’s data plate of the condenser (outdoor unit} of the system. Look for a number divisible by 12 or 6. Here’s a few examples from different companies, with the BTU number circled. They are 3, 3-1/2, and 4 tons.
Also see our blog post How can I find out the age of my air conditioner or furnace?
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To learn more about heating and air conditioning systems, see these other blog posts:
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