Sounds like an overflow drain to me.
I don't understand why a copper pipe would be pulled into
a "receptacle"... Do you mean an electrical receptacle ?
If so, please ignore anything I say, cause that would make
no sense to me at all....
Otherwise, airconditioners have water drains to get rid
of water accumulation across the coils that happens when
you aircondition in humid weather. You will ALWAYS have
a drain running either outside the house, or into your
plumbing drain inside the house. Very little water goes thru
this and there is NO pump, just gravity..... Occasionallly
these get clogged, and you just go upstairs and pour a
little bleach ( Clorox or equiv) into it each year , if needed.
Don't worry about not seeing anything in a new system.
If you are worried, put a glass under the end to catch the
water, and watch it all summer. You should get something
thru sooner or later......depending on your attic ventilation and
the humidity and temp...
If you didn't have this overflow line, if too much water formed
in the air conditioner, it would leak out and wet your ceiling and
make a mess.
Even window mount units have this overflow valve in the
back of them to drain the water outside.
Like I said, if this "tube" goes into an electrical receptacle,
forget anything I have said....... exxcept the useful parts :>)))))
Andy in Eureka, Texas
PS Check the manual or documentation that came with the
new unit. It should talk about it somewheres...