What is a ton of AC?

This explanation by coldfuse on the web site onlineconversion.com looks quite good.

Re: Ton of air conditioning
by coldfuse on 02/06/02 at 20:53:16

Just wanted to provide background on the derivation for tons of refrigeration, and provide information on the similar SI standard.

The latent heat of fusion for ice is 144 BTU/lb. For one ton, that is 2000 lb x 144 BTU/lb, or 288,000 BTU. Refrigeration's roots are in the ice making industry, and the ice guys wanted to convert this into ice production. If 288,000 BTU are required to make one ton of ice, divide this by 24 hours to get 12,000 BTU/Hr required to make one ton of ice in one day.

This is simply the requirement for the phase change from liquid to solid -- to convert +32 deg F water into +32 deg F ice. As a practical matter, additional refrigeration is required to take city water and turn it into ice.

One BTU is the heat removal required to lower the temperature of one pound of water by one degree F. In SI units, kilocaries are used. One kilocalorie is the heat removal required to lower the temperature of one kilogram of water by one degree C. One ton of refrigeration is equal to 3024 kilocaries per hour. It is basically the 12,000 BTU/Hr divided by pounds per kilogram divided by 1.8 (to get from degrees F to degrees C).

I hope this explanation hasn't been too cumbersome and will be helpful for someone out there! I'll :-X now!