I have installed a three and half ton condenser unit and a 4 ton evap coil in my modular home. I am having trouble with it wanting to freeze up. This is a Payne system, 13 SEER. It is a down flow system. The service tech from Carrier said that I wasn't getting enough air across the coil. So from his instructions I put a make shift sheet metal plemnom under neath it but still not sure that it's going to work (only 65 degrees today). I am thinking about going and getting a coil from a mobile home dealer and trying that. Any advise would be so helpful.