Refrigeration systems are basically designed to remove heat energy from the product to be refrigerated. The removal of this heat energy reduces the product to a safe temperature for either long- or short-term storage. This heat energy is not destroyed, but is rather transferred from the product to an area where it does not matter such as the outside air or a water source. In its simplest form, the first law of thermodynamics states that energy can neither be created nor destroyed. The amount of energy in the universe is constant — energy can be changed, moved, controlled, stored, or dissipated. This is one of the major operating principles behind the refrigeration systems used today.
The amount of heat energy a system can transfer is its refrigeration capacity. One of the ways a system’s capacity is rated is in tons of refrigeration (sometimes abbreviated as TR). When referring to a system’s capacity, most technicians define a ton of refrigeration as 12,000 Btu per hour. It is the “per hour” that is important to remember when discussing a ton of refrigeration. A ton of refrigeration can also be stated as the heat transfer of 288,000 Btu per 24 hours, or 200 Btu per minute.