Ton of cooling
ton · ton of refrigeration · tonnage
A ton of cooling is a unit of air conditioning capacity equal to 12,000 Btu per hour, about 3.52 kW; it comes from the heat absorbed by melting 2,000 pounds of ice in 24 hours.
A “3-ton” air conditioner or heat pump has a nominal cooling capacity of 36,000 Btu per hour. The kilowatt figure, 12,000 ÷ 3,412 per ton, is thermal capacity, not the electricity the unit uses.
Tonnage is a nominal size. Real capacity varies with outdoor temperature, indoor humidity and airflow, so sizing uses the manufacturer’s performance data at the conditions that matter, and a load calculation for the house, rather than the tonnage alone.
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