On Aug 29, 5:10 am, Jon Elson wrote:
Karl Townsend wrote:
After only 30 years it looks like one of my apple cooler's compressor and
evaporator unit needs to be replaced. It uses 502 refrigerant. This was the
best choice for low temperature coolers with electric defrost when I got it
new.

Not many 502 systems are installed today because 502 is so hard to get. (Its
very similar to the now banned R12) But I own a 30 lb. jug plus about a 10
lb. charge in the old system.

A fella told me the 502 systems are inherently more efficient because they
run at lower operating pressure. Efficiency is important, the electric is
north of $1K per month when it runs.

It is a lot more complicated than that. Operating pressure has
nothing to do with efficiency. R502 is a mixture of two
different gases, see
http://www.free-ed.net/sweethaven/MechTech/Refrigeration/coursemain.a...
for more info.

Efficiency has to do with how much work it takes to condense the
gas, compared to how much heat that vaporizing gas absorbs.


Doesn't a lower operating pressure imply that less work is done
to condense the gas?

It IS much more complicated than that, but operating pressure is
relevant.

--

FF