When it comes to measurements & scales, the United States is on a different page than the rest of the world. Other countries measure the capacity of an HVAC system in the form of BTU (British Thermal Units) per hour, while the US standard measurement is in Tons, or Tons of Refrigeration. Most HVAC manufacturers will provide cooling capacity in both BTU per hour and Tons.
A BTU is a unit of energy (heat), while a ton of refrigeration and BTU per hour are units of power. Power is the rate at which energy is used over time. It’s like driving a car — a mile is a unit of distance, while speed is distance traveled over a period of time.
A ton of refrigeration is the amount of heat needed to melt a 1-ton (2,000 lb.) block of ice over a 24-hour period of time and is equivalent to approximately 12,000 BTU per hour.
To put it into perspective, a BTU is the amount of heat given off by a four-inch kitchen match burnt completely.
This means that a 1-ton air conditioning unit is responsible for cooling the amount of heat generated by 12,000 matches every hour, or 288,000 matches every single day!
If we take it a step further with a 5-ton air conditioner, it would take 10,000 lbs of ice in a 24-hour period to provide the same amount of cooling. This is equivalent to absorbing the heat generated from 1.44 million matches!
People, equipment, and outside temperature are just three of a multitude of things that add heat to an indoor space. When deciding how much cooling an area needs, engineers must account for the application, location, and square footage of the space.
When looking at a model number on a piece of HVAC equipment, there will sometimes be a number that is divisible by 12. This is typically the BTU per hour measurement (in the thousands).
For example, a Trane model number TSC060 is a 5-ton unit. This can be found by taking the 060 in the model number and dividing it by 12, yielding 5 tons.
A Daikin model number DCC090 tonnage can be found by taking the 090 in the model number and dividing it by 12, yielding 7.5 tons.
Use this trick with a bit of caution; not all manufacturers use this numbering system for their equipment!
