When the temperature goes below 60 degrees F, frost or ice can form on the coils, which prevents moisture removal. When the room temperature falls below 60F, the unit will go into an Auto Defrost (electronic controls) or Auto Frost (knob controls) mode to remove frost from the coils before starting dehumidification again. During the defrost cycle the compressor turns off but allows the fan to continue running. If frost build up is continuous, verify the room temperature is above 41 degrees F.
When the dehumidifier is first plugged in after purchase or for the season, the unit may ice up This is normal and will usually disappear within 60 minutes unless the temperature in the room is below 60 degrees F.