I have a customer looking to replace his 3.5 ton 22 year old Lennox A/C and coil with a 13 SEER system. He currently has a 3/4 X 5/16 line set @ 30' long. I told him we needed to install a 7/8 X 3/8. All other contractors told him he was OK with what he has. Where can I get some information to back me up, or am I wrong here?