BTU th
BTU (thermochemical)
Energyexact by definition
The thermochemical BTU is exactly 1054.35026448889 joules, derived by putting the thermochemical calorie on a pound of water and a Fahrenheit degree. It is the BTU of chemistry, explosives work and US military specifications.
Watch out: The site's plain BTU is the International Table BTU of exactly 1055.05585262 J, which is the one used by ASHRAE, the gas industry and every HVAC nameplate. The gap is 0.07 percent. It never matters on a furnace rating and it does matter when a standard specifies which one, so check the standard rather than assuming. Other BTUs exist too, defined at 39 °F, 59 °F and 60 °F, spanning about 0.2 percent in total.
| 1 BTU th | 1,054.3503 J |
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