In refrigeration and air conditioning (HVAC) terminology, a ton-hour is a unit of measurement used to quantify the cooling capacity or the amount of heat removed by a refrigeration system over a specific period of time. It is primarily used in commercial and industrial applications to assess the performance and cooling efficiency of large HVAC systems.
One ton-hour is defined as the amount of heat required to melt one ton (2,000 pounds) of ice at 32 degrees Fahrenheit (0 degrees Celsius) into water over the course of one hour. This quantity is equivalent to 12,000 British Thermal Units (BTUs) of cooling capacity. So, if a refrigeration or air conditioning system has a cooling capacity of 1 ton, it can remove 12,000 BTUs of heat per hour.
The ton-hour measurement is useful for calculating the cooling load of a building or an area and determining the appropriate size and capacity of the HVAC system needed to maintain comfortable indoor temperatures.
It's important to note that the term "ton" in this context refers to a cooling capacity and not weight. It originates from the early days of refrigeration when ice was used for cooling, and the term "ton" was a reference to the amount of ice required to produce a specific cooling effect. While modern HVAC systems no longer use actual tons of ice, the term "ton" is still used to represent cooling capacity in the industry.