In winter, an icy heat pump can cause uncertainty — but what is really behind it? Is this normal or is it already an indication of a technical problem? In this article, you will learn why icing occurs, when action is needed and how to reliably protect your system from ice.

‍

Is icing normal or a problem?

Slight icing is only normal for air-water heat pumps and is part of regular operation. It becomes problematic when the icing persists permanently, becomes very thick or impairs the heating output. In such cases, the automatic defrost system may be faulty or there may be a technical problem — such as a faulty sensor, lack of refrigerant or a dirty evaporator. A specialist company should then check the system.

Why does a heat pump freeze?

air source heat pumps Icing because moisture condenses and freezes on the evaporator when heat is generated from outside air. This happens particularly frequently at temperatures between 0 and 5 degrees Celsius and high humidity.

The air-water heat pump extracts heat from the outside air via the evaporator. As a result, the evaporator cools down significantly — below the dew point of the ambient air. The moisture contained therein settles and freezes. This ice formation is normal in itself, but can become a problem if it persists permanently or becomes too thick.

How does the automatic defrost function?

With automatic defrosting, the heat pump checks the degree of icing at regular intervals and starts a defrost program if necessary, usually via so-called hot gas defrosting.

The refrigeration cycle is reversed for a short time: Instead of the outside air, the evaporator itself is now heated by directing hot refrigerant to it. As a result, the ice on the evaporator thaws and the condensed water is drained off via a drainage device.

The automatic defrosting system is controlled by sensors that monitor temperatures and operating times. If a critical layer of ice is detected, the heat pump automatically starts the defrosting process — often depending on cut-off times or operating conditions. Modern systems thus effectively prevent loss of performance due to icing.

What effects does icing have on the heat pump?

Severe icing impairs the efficiency of the heat pump and can cause damage in the long term.

The formation of ice blocks the evaporator so that heat can no longer be extracted from the outside air. The heat pump then has to work more frequently and longer, which increases electricity consumption and worsens the annual performance factor. If the icing persists permanently, the refrigerant circuit can be disrupted. Components such as fans, sensors or automatic defrosting systems can also be damaged.

In the worst case scenario, the heat pump will fail completely — and the heating will stop.

What to do if the heat pump constantly freezes

If the heat pump constantly freezes, there is a fault or an unfavorable operating situation. In this case, you should have the system professionally inspected before permanent damage occurs.

Common causes include faulty sensors, impaired airflow, lack of refrigerant or an incorrectly adjusted automatic defrost system. Even an unsuitable location can lead to constant icing.

In the next section, you can read what measures you can take yourself to prevent icing.

‍

Avoiding icing: tips & tricks

With proper planning and regular maintenance, you can significantly reduce the risk of icing. The following tips will help ensure that your air-water heat pump functions consistently:

• Suitable location: Place the outdoor unit elevated, sheltered from the wind and at a sufficient distance from walls or plants.
• Free airflow: Make sure there is nothing obstructing airflow — neither leaves, snow, nor structural obstacles.
• Keep evaporators clean: Remove dirt and debris from the heat exchanger regularly.
• Discharge condensate: Check the meltwater runoff and prevent waterlogging or ice formation under the system.
• Regular maintenance: Have sensors, refrigerant level and controller checked annually by a specialist company.
• No self-made buildings: Avoid covers or roofs without consulting the installer — these can interfere with airflow.

autarc: Your partner for efficient planning of heat pumps — find out more now!

Rely on quality and expertise when planning and installing heat pump systems. With our Heat pump check receive comprehensive support so that you can implement your projects efficiently and sustainably. Contact us today and benefit from our expert knowledge!

‍