What brand of units have the recommended SubCool amount in the unit nameplate tag? What are those #'s of SC? What is the lineset length limited to at the nametag SC rating? Trane's nametag rating is 8-10*SC and their tubing length is 25' ,otherwise consult the factory! What do you guys see?
I believe you will see most manufacturers are going to 15' from 25', so check the unit manual. But that is not lineset length; it is the factory refrigerant charge. You need to add "x" ounces per foot over 15'; again, that info is in the manual. Lineset TEL is in the manual too. It might be 60' for some models and 50' for others. Beyond those limitations you need the software we talked about or call your distributor. Regarding your question about sub cooling numbers: if you have 10 degrees of sub cooling, that means your actual LL temperature is 10 degrees cooler than your LL PSIG converted to temperature. This ensures your 100% column of liquid at the TXV. For example, if your LL is 295 PSIG with R-410A and your LL temperature is 85 degrees, then you have 10 degrees of sub cooling.