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(J Jensen) wrote in message om...
"~KJPRO~" KJPRO @ STARBAND.NET wrote in message ...
"J Jensen" wrote in message
om...

7. It isn't worthwhile to check on the amount of Freon (or whatever) that
is
in the system -- all that matters is measuring the temperature of the
cold air coming out (say 62 F) and the outside temperature or maybe the
attic temperature.
--Jeff

This has to be some of the purist BS I have read lately.

~kjpro~

This was what an a/c technician told me when I called him out to the
house
with the specific request to check if any Freon had leaked out of the
system over the years, or if it was still operating at 100%. He would
not do it,
although he did check some other things. On the bright side, he did
encourage
me to sign up for yearly maintenance by his company...
--Jeff

Your technician was correct. He would determine if it was operating at
100% though use his gauge set for pressure measurements, and the
temperatures measured on the evaporator and condensor coil surfaces to
approximate this determination. If these are within the prescribed
ranges, there likely is little need to top off the refrigerant charge
in the system.

So long as the freon in the system is at a sufficent level to
continuously provide bubble free liquid in the high pressure line, it
makes little difference in the operating characteristics of the air
conditioning system.

In fact, larger industrial systems always include a view port in the
liquid freon line to check for excess bubbles. Too many bubbles may
also reflect a need for the addition of freon to the system or the
installation of the system was faulty and contains trapped air.

A refrigeration gauge set is incapable of revealing this information,
and indicates only that the pressures in the low and high pressure
sides of the system are consistent with the particular variety of
freon in use for the measured surface termperature on both the
condensor and evaporator coils. It reveals very little helpful
information about the adequacy of the freon charge in the system.
Usually a pocket sized card for the freon in use (typically Freon-22
in small to medium size -- 3 to 30 tons -- central A/C systems).

On smaller home systems which lack a view port, most competent
refrigeration techs will, after checking the operating pressures,
charge the system up to the point where frost begins to appear on the
evaporator low pressure tube fitting. This is the point of optimal
cooling and presumably optimal system efficience.

I'm not a refrigeration engineer (although I am a physicist/engineer),
but over the years (at least 30) I've maintained or installed some
reasonable large refrigeration systems and air conditioners (some of
which were two-stage special purpose systems capable of reaching test
chamber temperature of below -80-degrees F), sever 30-60 ton air
conditioning systems, and installed 3 central systems in homes that
I've owned.

During these years, out of necessity I learned how to replace
compressors, braze joints, pull a vacuum and "dry" the systes, employ
leak detectors and repair leaks, all basic to the HVAC trade,
consequently I'm pretty sure of the correctness of the info I post,
and I would challenge any A/C or HVAC tech to specifically cite and
correct any error. In fact, over 30 years I never had to employ an
HVAC tech to correct any of my work. (In fact, it was the inadequance
of the HVAC techs that I encountered that first cause me to get my
hands dirty!)

Harry C.

p.s., Never SMOKE when you're working with freon. Any competent
refrigeration engineer can explain to you why this precaution is
needed, but your average HVAC tech is little more than a glorified
plumber and likely hasn't a clue (unless of course his supervisor has
informed him)!