The answer to 'ductless system freezing up' is that a ductless air conditioning system (also called a mini-split) can freeze up due to a few common causes. This typically happens when the system is not functioning properly and the refrigerant is not flowing correctly, causing ice to build up on the indoor coil.
Some common causes of a ductless system freezing up include low refrigerant levels, a blocked air filter, a malfunctioning thermostat, or a problem with the compressor. If the system is freezing up, it's important to address the root cause quickly to prevent further damage. In many cases, a frozen system is a sign of an underlying issue that needs professional diagnosis and repair.