Have an old Lennox heatpump to change out and me and the boss whose been in the industry much longer than me but not a Lennox dealer disagree on the size. He says a M/n 10HP48-1p, S/n 5193E32877 is a 5 ton because Lennox used odd numbering back in the day but it sure looks like a 4 ton to me by those numbers. Can a Lennox guy chime in and settle this ? Thanks