Dr-Fix-It! The Refrigeration Ton
Dr-Fix-It Defines the Term Refrigeration Ton and provides practical examples as well as rules of thumb.
With the introduction of refrigerating machines in the first half of the 20th century, the new refrigeration industry was faced with a challenge. What recognizable measurement for "coldness" could be easily understood by the public?
Refrigerating machines and air conditioners moved heat and therefore could be rated in terms of BTU's per hour. The British Thermal Unit ( BTU ) is defined as the amount of heat necessary to raise the temperature of one pound of water one degree Fahrenheit from 58.5 to 59.5 degrees Fahrenheit. (See BTU )
But, to the general public, "BTU's" were used in the measurement of something hot like a heater or boiler. "Coldness" was generally perceived to be something entirely different than heat !
Most consumers were used to iceboxes and cold storage ice warehouse facilities were common. So, in a stroke of marketing genius, the recognizable measurement for "coldness" was defined as a relationship to melting ice!
Melting Ice at 32 degrees Fahrenheit requires 144 BTU's per pound to become liquid at 32 degrees Fahrenheit. The Refrigeration Ton was defined as the heat ABSORBED by one ton of ice (2000 pounds) causing it to melt completely by the end of one day (24 hours). Therefore:
Note that the Refrigeration Ton is a defined as a BTU's per hour which is work units divided by time units. Work done in a time frame is defined as power. (See POWER) Therefore, the Refrigeration Ton can be related directly to other definitions of power such as horesepower or watts.
However, the idea of Refrigeration Ton made it easier to sell equipment to the common person of the day. The machine's capability could be compared to a quantity of ice. Imagine a salesperson trying persuade a customer that a new-fangled "refrigerator" is equivalant to an icebox holding several hundred pounds of ice! "And just imagine...no more ice deliveries!" Today, the term is still in common use. The capacity of most air conditioners, larger coolers and freezers and even icemakers nearly always described in terms of the Refrigeration Ton.
Rules of thumb (Assuming Usual Ceiling Heights):
1 ton of air conditioning for every 400 square feet of floor space.
Each ton of air conditioning requires 400 CFM airflow.
Walk in coolers: one ton to 175 square feet of floor space.
Walk in freezers: one ton to 85 square feet of floor space.