Coils freezing up!

The refrigerants is related to a system preassure and temperature relationship! If too low preassures the refrigerant cools too low.. If just right it will stay above freezing temperatures ((32*)) If too high of a preassure, or too much refrigerants ,the temperatures will stay too high and not cool down the return air at manufacture specs. and not remove the designed btu's and humidity... ....(bottom line, just check out a reputable hvac serviceman.) Oh yes, also low air flow across the indoor coils!