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Re: The chilling truth about cold horsepower

Aquarium chiller manufacturers seem to equate 1 hp, a
commonly used unit of measurement for the capacity of their
chillers, with 12,000 BTU/hr.  Although, one must admit
that some of them follow a rather loose set of arithmetic

What's interesting to me is that every engineering
reference I've been able to dig up equates 1 HP to 2540
BTU/hr (give or take a few BTU).

The reference works and engineering tables do commonly
equate 1 hp to 12,000 tons refrigeration, but not 12,000
BTU/hr.  Tons Refrigeration is a still used but somewhat
antiquated standard of measure for chilling capacity,
having originated as a measure of the amount of ice a
device could produce in a fixed period.

I checked my 1965 World Book Encyclopedia and found the following information in the article on Air Conditioning. Air conditioners are rated in three ways, by B.T.U.'s, Tons of Refrigeration, or by Horsepower. One Ton of Refrigeration removes the amount of heat needed to melt one ton of ice in 24 hours. One Ton of Refrigeration can remove 12,000 B.T.U.'s of heat in one hour. The B.T.U. is the amount of heat needed to raise 1 lb. of pure water 1 degree F. An air conditioner rated at 12,000 B.T.U./hr. can remove the heat needed to raise 12,000 lbs. of water 1 degree F. Horsepower is the amount of power needed to run the refrigeration equipment that cools the air.

I am not an expert at all on refrigeration, but answering this question has helped me with understanding what Tons of Refrigeration means as I couldn't understand why such a term was used. Thanks Scott for the question and provoking me to search it out.


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