Ton of refrigeration
Also known as: TR, RT, refrigeration ton
Short definitionA capacity unit found in US catalogues. 1 ton of refrigeration is 12,000 BTU/h, about 3.52 kW; the name comes from one ton of ice melting in a day.
The unit dates from the years when ice was made in factories and sold. The heat rate needed to melt 907 kg (2,000 lb) of ice in 24 hours counts as 1 ton of refrigeration, shortened to TR or RT. It equals 3.517 kW. Chiller and air handling unit catalogues still use it; a 40-ton chiller is a machine of about 141 kW.
Cold room quotes state capacity in kW. To compare a unit rated in tons with a quote in kW, multiply the figure by 3.5; put side by side without converting, a gap of about three and a half times goes unnoticed. It is also confused with product tonnage: a 10-tonne apple store describes the weight of the product, and the cooling capacity it needs can only be found by a load calculation.