What is meant by a ton of refrigeration?
Confusingly the unit has little to do with weight, as used in common parlance. One ton of refrigeration is the term used to refer to 12,000 B.T.U.s/hour (British Thermal Units/Hour) of cooling effect. Thus a chiller or condensing unit with a cooling capacity of 60,000 B.T.U.s/hour is said to have a capacity of 5 tons. It should be noted that the unit B.T.U./hour is a unit of heat flow still widely used in North America, Canada and parts of Asia whereas Europe uses the ‘watt’. One ton of refrigeration approximates to 3.5kW of cooling. The origin of the term is the amount of heat absorbed by one ton of ice when melting from solid to liquid state at 32°F and assuming a latent heat of ice of 144 B.T.U.s/lb. The heat absorbed is found to be 288,000 B.T.U.s over 24 hours, or 12,000 B.T.U.s/hour (in reality the latent heat of ice is slightly less than 144 B.T.U.s/lb.
A. The term ton is of course 2000 pounds which primarily has nothing to do with refrigeration, but ice was the only means of refrigeration for many years and was harvested from frozen lakes and was stored for food preservation. By definition, a ton of refrigeration is 12,000 BTU (British thermal units). This is found by taking the heat of fusion of water, which is 144 BTU per pound of water and melting the ice, still at 32 degrees Fahrenheit for 24 hours: 144 x 24 = 288,000 BTU. Then to divide 288,000 BTU by 24 hours resulting in 12,000 BTU. That 12,000 BTU per hour is a ton of refrigeration, and is the basis of air conditioning calculations.
Confusingly the unit has little to do with weight, as used in common parlance. One ton of refrigeration is the term used to refer to 12,000 B.T.U.s/hour (British Thermal Units/Hour) of cooling effect. Thus a chiller or condensing unit with a cooling capacity of 60,000 B.T.U.s/hour is said to have a capacity of 5 tons. It should be noted that the unit B.T.U./hour is a unit of heat flow still widely used in North America, Canada and parts of Asia whereas Europe uses the watt. One ton of refrigeration approximates to 3.5kW of cooling. The origin of the term is the amount of heat absorbed by one ton of ice when melting from solid to liquid state at 32F and assuming a latent heat of ice of 144 B.T.U.s/lb. The heat absorbed is found to be 288,000 B.T.U.s over 24 hours, or 12,000 B.T.U.s/hour (in reality the latent heat of ice is slightly less than 144 B.T.U.s/lb.) 8, Why should I replace my existing heating or air-conditioning system? You may wish to consider replacing your air-conditioning
