Defrosting

During defrosting, an air-source heat pump removes frost and ice from its outdoor heat exchanger. This uses a little energy and is just part of winter operation.

An air-to-water heat pump gets its heat from the outdoor air. In doing so, it significantly cools down the air at the evaporator, the finned heat exchanger in the outdoor unit. Moisture from the air condenses on the fins. If the temperature at the evaporator is below 0 °C, this water freezes into frost and ice.

Why this is important

Ice clogs the fins. The air cannot pass through as easily and the refrigerant absorbs less heat. Therefore, the appliance must defrost the ice regularly. This requires energy, which reduces the heat pump's performance factor. Which defrosting method is used depends on the appliance.

What this means for you

• Plumes of steam or dripping water on the outdoor unit on cold, damp days are normal and not a defect.
• The meltwater must be able to drain away. Plan a gravel or shingle bed under the appliance.
• Choose a slightly elevated location that will not sink into the snow in winter.
• If fault messages regarding defrosting accumulate, have this checked by your installer.

This does not affect geothermal and groundwater heat pumps because their heat source does not freeze. If you want to compare heat sources, read Air or geothermal energy. The efficiency over the whole year, including defrosting, is shown by the seasonal performance factor (JAZ).

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