What is a ton of refrigeration (TR)?

A ton of refrigeration (TR) is a unit of cooling capacity equal to 3.517 kW or 12,000 BTU/hr. It originated from the cooling effect produced by melting one ton (2000 lbs) of ice at 0°C over 24 hours. This unit is commonly used in India and the USA for rating air conditioners and chillers, with typical window ACs rated at 1-2 TR and industrial chillers ranging from 50-1000 TR.