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The modern definition is exactly 12,000 Btu IT /h (3.516853 kW). Air-conditioning and refrigeration equipment capacity in the U.S. is often specified in "tons" (of refrigeration). Many manufacturers also specify capacity in Btu/h, especially when specifying the performance of smaller equipment.
Another unit common in non-metric regions or sectors is the ton of refrigeration, which describes the amount of water at freezing temperature that can be frozen in 24 hours, equivalent to 3.5 kW or 12,000 BTU/h. [1] [2] [3]
Air-conditioner sizes are often given as "tons" of cooling, where 1 ton of cooling equals 12,000 BTU/h (3.5 kW). 1 ton of cooling equals the amount of power that needs to be applied continuously over a 24-hour period to melt 1 ton of ice. The annual cost of electric energy consumed by an air conditioner may be calculated as follows:
The Btu should not be confused with the Board of Trade Unit (BTU), an obsolete UK synonym for kilowatt hour (1 kW⋅h or 3,412 Btu). The Btu is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in Btu required to generate 1 kW⋅h of electrical energy.
A ton of air-conditioning is defined as the removal of 12,000 British thermal units per hour (3.5 kW). The equivalent ton on the cooling tower side actually rejects about 15,000 British thermal units per hour (4.4 kW) due to the additional waste-heat–equivalent of the energy needed to drive the chiller's compressor.
HVAC (heating, ventilation, and air conditioning) is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many ...
In the United Kingdom, a Seasonal Energy Efficiency ratio (SEER) for refrigeration and air conditioning products, similar to the ESEER but with different load profile weighting factors, is used for part of the Building Regulations Part L calculations within the Simplified Building Energy Model (SBEM) software, and are used in the production of Energy Performance Certificates (EPC) for new ...
So, for a boiler that produces 210 kW (or 700,000 BTU/h) output for each 300 kW (or 1,000,000 BTU/h) heat-equivalent input, its thermal efficiency is 210/300 = 0.70, or 70%. This means that 30% of the energy is lost to the environment. An electric resistance heater has a thermal efficiency close to 100%. [8]