[time-nuts] Obscure terms

[Lux, Jim (337C)]

Or, what about "boiler HP" which has almost no relation to the HP used in connection with motors and engines.

They still use that measure of insulation, slightly changed, as R value: BTU/hr = 1/R * delta T(deg F) * square feet

Tons, as a unit of refrigerating capacity (12000 BTU/hr) is still widely used (e.g. My house has a 5 ton air conditioner).  Small AC units are rated in BTU/hr (e.g. The window type units are 5000 or 9000 BTU/hr)

While somewhat weird, they DO have a practical basis.  Before mechanical refrigeration, one bought ice by the ton, at least if you were big enough to be interested in a mechanical refrigerator, so it's natural for the makers of such systems to give the performance in units familiar to the customer (Hey, Mr. Meat Locker owner, I'm Mr. Carrier, and you're buying 10 tons a day of ice. I've got this machine here that can replace that, for only $X.  Such a deal)

Once you marched down the BTU path, the (U.S.) R-value numbers make total sense.  I think that in Europe, the R value is calculated differently.


On 8/20/09 2:25 AM, "Neville Michie" <namichie at gmail.com> wrote:



> One of the more interesting units used in the air conditioning
> industry in USA in the past was
a measure of wall insulation which was tons per square foot per inch
per degree Fahrenheit.
That is the number of tons of ice per 24 hour period that must melt
to sustain a temperature difference
of one degree F per square foot of wall one inch thick.
Not far off furlongs per cubic fortnight.
cheers, Neville Michie


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