Eli5: why is the Air conducting measured in ton?

Question

Eli5: why is the Air conducting measured in ton?

In: 5

Answer 1

Etymology seems to come from when “tons” of ice were needed to keep a room cool.

1 Ton is 12000 BTU/hrs (British Thermal Units). 1 BTU is the amount of energy needed to increase 1lb of water by 1°F (why do British units use Fahrenheit, who knows). 1 Ton is also 3.5kWh. So going back to ice, 1 ton of ice at 32°F will melt in 24hrs if it absorbs 28800p BTU (definitions state 144 BTU/lb, so 144•2000), which is 12000/hr.

Square footage is used to determine how powerful a unit you need, which already isn’t ideal as volume of the space would be more useful (a 2000ft^2 building with 15ft ceilings needs more cooling than a 2000ft^2 building with 8ft ceilings). Windows and whatnot are also used for consideration.