Question: why are arcs measured in tons?
Answer: The use of tons to measure cooling capacity comes from this time. A ton refers to the amount of heat it takes to completely melt a ton of ice. Melting this amount of ice requires 286,000 Btu (British thermal units). ... Rounding up 11,917 Btu/hr gives you 12,000 Btu/hr, which is one ton of air conditioner capacity.