I got a 1.5 ton unit to replace. Old unit has 3/16"ID liquid line, but new 10 SEER unit has 1/4" ID line size. Both units run R22. One of our techs say use the old 3/16" line size is OK, I'd rather change out the line to what the new condensing unit has (1/4"). Total run is small, maybe 20 feet with minimal bends. Suction line size is the same amoung both units, if it matters.