Many years ago I worked as a installer of HVAC systems. Mostly
the air handling part. Before they required the saving of used
freon I did all my AC work, at work and home.
About 30 years ago I got out of the HVAC installing part and
centered mostly on sheet metal fabrication. Ductwork, flashing,
and other custom work.
Being retired I only work on my own equipment now days.
I haven't really kept up with the new systems, so wouldn't be
much help explaining them.
Old Rabbit