Just watched episode 1209 of season 12 where an A/C unit was diagnosed
as being too large by a ton. They reduced it from 4 ton unit to a 3 ton unit and this apparently cured the problem the homeowner had of a freezing coil.
As I watched the show, I noted that Richard skipped right over the issue of whether or not the return ducts matched the supply ducts...a VERY common problem when you have HVAC vendors/installers who do not understand what they are doing. Richard probably correctly diagnosed why the coil was freezing but from what I saw, it appeared that the system had one 12" return and had multiple (at least 3) supply ducts that were as large as the return duct. Thus, there was an imbalance of return to supply (not nearly enough return air) which could cause the same problem of a freezing coil or at least be the cause of the inability to cool the home down to the desired temp in the summer.
Re: Just watched episode 1209 of season 12 where an A/C unit was diagnosed
The supply ducts were either 6 or 8" flex ducts. There is 2" of insulation under the outer foil cover. Personally I think the thing either had a bad evaporator valve or was under charged.