Just replaced my a/c condenser,3 ton, with a new 2.5 ton unit. It had a charge of r-22 good for a 25 ft line set. Mine is 20 ft. When I run it the suction line gets very cold but I get no rise in temp on the liquid line. The air at the vents is slightly cooler the ambient, but never gets any cooler.On a 100 degree day my pressures are low side 65 and high side 265-275. Wondering if any suggestions on why it is not cooling.

Did you do the installation or was it done by a professional? If you did it, good luck to you. If you hired a professional, call them back to readjust the unit.