There is no real true settings for superheat, you as tech
must find what is best for your type of condition you are
working on. example while 10 degree of superheat may be
ideal for AC system with 25 feet line it might not be for 150 feet,
you need to know what is more important to you efficiency of
your system or life of compressor don't forget that compressor
gets cooling from gas coming back to it, some time compromised
got to be taking, but if compressor can not stay cool then suction
liquid injection must be added, it all depend on you application
ideal superheat is always around 10-20 degree however it should
never be less then 10.
The reason for asking this question is I'm working on a high rise
building that the engineer designed and that is why it requires a 150
ft to 200ft line. Also consider putting 10 SEER units adding
accumulator and a TXV.
Truth be told, you have to take into account the *pressure loss* the extra
line length presents. If there is an increase in the suction line to
overcome line loss, you might be restricting the oil return process.
[Suction return velocity.] Most aren't aware of this excpet Paul... :)
Lenghty suction lines should be avoided, but, if you must know, after the
first 50 feet, you should expect pressure loss. [And capacity loss.] The
best method would be to measure the suction line temperature and pressure at
the evaportor, [using an adaptor on the TXV equilizer tube] then perform the
same process at the outdoor unit [condenser]. You'll discover the pressure
and temperature differences. [In the case of a fixed metereing device -
you are out of luck.] Understand that depending on the route the suction
line takes, there will be some increase in suction temperature as well.
Asking this question means you should seek some additional education from
your local community college or the manufacture of the equipment you sell.
Yes...Paul is my personal hero.
The fact remains, however, that superheat is superheat.
It doesn't give a shit about linesets, desuperheaters, hot gas by-pass feeds
or anything else.
PS- I'm a reprobate
comply with refrigeration suggested formulas and you might
find that are some far out of suggested superheats as for my
line of work superheats can vary from 5 to 150 degrees but
that is another story. what's important in superheat that you
keep compressor happy rest of it is all secondary
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