The most common cause of frost and ice buildup on a dehumidifier is because the unit is operating in temperatures that are too cold. Many dehumidifiers are not equipped to run at temperatures below 65 degrees Fahrenheit. There are some models made for cooler basements that operate down to temperatures of 36 degrees. Poor airflow, due to a dirty filter, also can cause freezing of the coils. Do not operate a dehumidifier when the coils are frosted.
Position the dehumidifier in an area where there is at least one foot of clearance around the unit in order to allow for proper air circulation during its operation. Close all windows, doors and other outside openings to make sure your unit isn't attempting to remove moisture from areas outside of the immediate room.
Determine the temperature of the room by checking a nearby thermostat or by using a hand-held thermometer. Many Frigidaire models can only operate without frosting when temperatures are above 41 degrees. Certain Soleus brand units can operate in temperatures down to 36 degrees. If it is colder than this, turn off your unit until the temperatures rise above these thresholds.
Check the filter for dirt and buildup. Unplug the unit from the electrical source and check the filter by opening the filter compartment. If the filter is dirty, it will restrict airflow through the unit and lead to freezing. Soleus recommends lightly vacuuming the surface of the filter to remove dirt. The filter also can be washed in warm water if it is extremely dirty. Once clean, place the filter back in its compartment. Allow for the ice to melt and then restart your dehumidifier.
Elevate the unit in order to take advantage of warmer temperatures off of the floor. Unplug the dehumidifier and empty the water from the tank. Place the unit on a table or other sturdy surface. Replace the tank, reconnect the unit to a power source and restart the dehumidifier once the frost or ice has melted.