| ton of refrigeration | |
|---|---|
| Unit of | Power |
| Symbol | TR |
| Conversions | |
| 1 TRin ... | ... is equal to ... |
| SI units | 3.51685 kW |
| Non-SI metric | 3,025.97 kcal/h |
| US Customary and Imperial | 12,000.00 BtuIT/h 2,593.90 ft⋅lbf/s |
Aton of refrigeration (TR orTOR), also called arefrigeration ton (RT), is aunit ofpower used in some countries (especially in North America) to describe the heat-extraction rate ofrefrigeration andair conditioning equipment.It was originally defined as the rate ofheat transfer that results in the freezing or melting of 1short ton (2,000 lb; 907 kg) of pureice at 0 °C (32 °F) in 24 hours.[1][2]
The modern definition is exactly 12,000 BtuIT/h (3.516853 kW). Air-conditioning and refrigeration equipment capacity in the U.S. is often specified in "tons" (of refrigeration). Many manufacturers also specify capacity in Btu/h, especially when specifying the performance of smaller equipment.
The ton of refrigeration is equivalent to the consumption of oneshort ton of ice per day and originated during the transition fromstored natural ice tomechanical refrigeration. Just ashorsepower andcandlepower were intuitive units of measure for people living through the transition fromhorse to steam power[3] and from flame-based toelectric lighting, so was the ton of refrigeration an intuitive unit of measure during atechnological change, as theice trade gradually included growing percentages of artificial ice (ice from ice-makingplant) in addition to its natural ice supplies. The TR unit was developed during the 1880s. Its definition was set at the level of an industrystandard in 1903, when Thomas Shipley of theYork Manufacturing Company led the formation of anindustry association (the Ice Machine Builders Association of the United States) along withstandardization of several equipment specifications.[4] In 1904 these efforts led to the founding of the American Society of Refrigerating Engineers (ASRE),[4] which was one of the predecessors ofASHRAE.