Dehumidifier coils icing up or frosting over (Meaco & De’Longhi)

Visible ice or frost forming on a compressor dehumidifier’s internal coils is a very well-known symptom, and in most cases it’s the appliance responding correctly to conditions it’s not designed for, rather than a fault.

What’s normally happening

Compressor-based dehumidifiers extract moisture by cooling air below its dew point, and in a cold room (typically below around 15-18°C depending on the model) that cooling process can drop the coil temperature low enough to freeze the condensation forming on it, rather than letting it drip away as liquid.

What to check first

• Check the room temperature — if it’s a genuinely cold space (an unheated garage, a cold conservatory), a compressor dehumidifier may simply not be well suited to that environment; a desiccant-type model performs better in cold conditions.
• Switch the unit off and let any ice fully melt and drain before running it again — running it repeatedly while iced up can strain the compressor.
• Check the air filter is clean and airflow around the unit isn’t restricted (too close to a wall or furniture) — poor airflow can worsen icing even at reasonable room temperatures.
• Check if your model has an automatic defrost function and whether it’s enabled — many mid-range and higher models include this specifically to prevent icing.

When to call an engineer

If the room is a normal indoor temperature, airflow is unobstructed, and icing still happens repeatedly (especially if your model has automatic defrost and it doesn’t seem to be triggering), the defrost sensor or refrigerant system may have a fault — worth a professional check.