After making the connection all pex fittings are installed with a crimping tool eliminating.
Lines in attic copper.
This is why i m thinking the upstairs handler is exposed to much more humid air as it can enter the attic space the unit is sitting in which may be contributing to the sweating lines.
The attic space it s in is much smaller with no outside vents and no sweating little copper lines.
In other areas the use of copper is widespread.
That should fix your problem with the sweaty copper pipe.
The most common gas piping is black steel.
For some homes the pipes will run underneath a subfloor or at the bottom of the attic.
Line the split up and make sure the adhesive glues the rubatex split together.
You want to create a vapor barrier to keep the humidity out and away from the pipe.
Galvanized steel copper brass or csst corrugated stainless steel tubing also can be used in some areas but some utilities specifically prohibit the use of copper.
Connecting to a copper line under the slab will require that a copper to pex fitting be soldered on.
Find out where the pipes are located to see if a ladder is needed to reach them or if you will have to work on your knees installing the insulation.
You should know what is acceptable in your area.
Thinner copper pipe carries liquefied refrigerant its temperature is approximately 110 f 43 3 c does not require insulation but in some installations insulating liquid refrigerant line is recommended.