I'm completing a remodel, and am looking at options for air conditioning. I had installed a 25' line set (1/4" x 1/2") last year in anticipation of having a mini-split heat pump installed. This size was used per the advice of a HVAC technician. According to my engineer, I will only need about 12k BTU for my application. Since then, I'm finding that the most common line set for high SEER heat pumps of that size is 1/4" x 3/8". This is discouraging, as I would like to go for higher efficiency from the start.

The question is, can I use the existing installed line set for the high efficiency models? If not, is there a manufacturer with mini splits higher than 13 SEER that would work?

I am not installing this unit myself, BTW, but I have learned throughout my remodel to not trust a single contractor's opinion on a matter. Once I've done the research, I will have a licensed HVAC professional provide and install the unit.