Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old August 31st 07, 05:12 PM posted to rec.crafts.metalworking
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Default refrigerant efficiency

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




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Old August 31st 07, 10:40 PM posted to rec.crafts.metalworking
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Default refrigerant efficiency

On Aug 31, 10:57 am, Gunner wrote:
On Fri, 31 Aug 2007 08:32:35 -0600, Lew Hartswick





wrote:
Gerald Miller wrote:
On Thu, 30 Aug 2007 20:23:22 -0700, wrote:


I've several old engineering manuals that put ammonia gas as #1 for
overall efficiency. Nasty stuff, but still used for large warehouse
and ice-making operations. Also biodegradeable and ozone-friendly.
You probably won't find the information you need out of a catalog,
efficiency depends on a lot of things, one reason the books are so
thick...


Stan


But have you ever been near a leaking SO2 system?
Gerry :-)}
London, Canada


Back when I was in grade school (1940s) a family had one (household
refrigerator using amonia) leak, fortunately only the pet (forget
what kind of pet) was home. Did it in. Nasty stuff to breathe.
...lew...


The reefer here in my RV was ammonia charged. Blew a fitting about a
year ago (which is why its now my dry storage).

Prior to that..Id had an ant problem here in the RV park.

Havent seen an ant, spider, moth, roach or any other critter since
then inside the RV.

Nasty!

Gunner- Hide quoted text -

- Show quoted text -


Most of the RV fridges are absorption types, can use propane or
electric heaters to do the boiling. Active stuff is ammonia gas,
water and a little hydrogen. Uses heat of solution rather than heat
of vaporization. Not as efficient and doesn't work at as high a
pressure as compressor-type ammonia systems. Also needs to be held
level to work. But well-suited for the purpose, no electric current
needed and it's quiet.

Stan

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Old September 1st 07, 04:15 AM posted to rec.crafts.metalworking
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Default refrigerant efficiency

I didn't get the original message but Karl, you can use R-408 as a drop in
replacment for R-502. The tech manuals will not agree but We have done it
many times, sometimes on a unit with a hermeticly sealed compressor where
there was not an easy way to change the oil. On an apple box I suspect you
have semi-hermetic compressors. The efficiency will be very close to
original with only slightly higher head pressures. Keep those condensers
clean! If you equipment is shot maybe it is time to upgrade. But if the
system has lost it's charge then use the R-408. I recommend if the system is
very short, remove the refrigerant change oil to alkybenzine (avoid poe if
possible it cleans the system and cloggs strainers) change filter, evacuate
and charge with R-408. If system is only slightly short of refrigerant top
it off . BTW R-502 is closer to the very popular R-404 today's choice than
R-12 in terms of pressures.
Good Luck Lyndell

wrote in message
ps.com...
On Aug 28, 6:29 pm, "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.

I'm searching all the commercial cooler units catalogs and I'm finding
nothing on efficiency. Most compressor/evaporators can be set up for more
than one refrigerant.

So, what's best?

Karl


I've several old engineering manuals that put ammonia gas as #1 for
overall efficiency. Nasty stuff, but still used for large warehouse
and ice-making operations. Also biodegradeable and ozone-friendly.
You probably won't find the information you need out of a catalog,
efficiency depends on a lot of things, one reason the books are so
thick...

Stan





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