The two most common units for stating the heat quantity are the British thermal unit (Btu) and the Calorie (cal).
- The Btu is the quantity of heat needed to raise the temperature of 1lb. of water by 1° Fahrenheit.
- The Calorie is the metric unit of heat quantity. It is the has needed to raise the temperature of 1 gram of water by 1 Celsius. Since a calorie is a very small measurement, it is practical to use thousand calories as the unit for Air-conditioning and it is expressed as Kilo Calorie (K Cal).
*One Ton Refrigeration was originally conceived to describe the quantity of heat removed to freeze 1 Ton (1 American Short Ton is 2000 pounds) of water at 32 Fahrenheit to ice at the same temperature in 24 hours.
**The Air-conditioning engineer uses the term “Ton Refrigeration” (TR), popularly referred to as ‘Ton’, when associated with refrigeration and Air-conditioning. We will use the term ‘Ton or its abbreviation ‘TR’ in this book.