Definition
A unit of cooling capacity equal to the rate of heat removal required to freeze one short ton (2,000 pounds) of water at 32°F into ice at 32°F in 24 hours. It equals 12,000 BTU per hour, or 288,000 BTU over a 24-hour period.
Plain English
A way of measuring how much cooling a system can do. One ton of refrigeration is the amount of cooling it would take to turn a ton of water into ice in a day.
Context Anchor
Seen in aircraft air-conditioning, cooling-system, and maintenance discussions when describing how much cooling a system can provide.
Derivation
The term comes from the early ice industry, before mechanical refrigeration was common. Cooling capacity was originally rated by comparing it to the amount of ice (one ton) that would need to melt to provide the same cooling effect. The name stuck even after ice was no longer involved.
Why Pilots Care
Aircraft air conditioning packs must deliver enough tons of refrigeration to maintain safe and comfortable cabin temperatures at altitude.
Grounding Statement
Picture the cooling power needed to turn two thousand pounds of ice into water over one day; that amount of cooling is called one ton of refrigeration.
Intuition Check
Do not read “ton” here as the weight of the air conditioner or the weight of refrigerant in the system. It means a rate of heat removal, not a physical load being carried.
Example Sentence 1
The aircraft's air conditioning pack is rated at about three tons of refrigeration, enough to cool the cabin on a hot ramp.
Example Sentence 2
During preflight checks the technician confirmed the refrigeration unit was still delivering its full rated tons of refrigeration.