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A short change in sound, a stopped fan, visible steam or water below the unit can be normal during and after defrost. The heating system is designed to manage these short interruptions.
Report persistent heavy ice, repeated faults, a fan striking ice, blocked drainage or loss of room temperature. Do not chip the coil or pour boiling water over it.
Frost risk depends on outdoor temperature and moisture, not cold alone
View sourceThe unit controls normal defrost cycles
View sourceDrainage should not create ice hazards around the unit
View sourceNot sure whether the defrost behaviour is normal?
Share the property, current heating and the question holding up your decision. FLO will explain what to check next without pushing you into a survey.
Why frost forms
The outdoor coil can operate below the surrounding air temperature while extracting heat. Moisture in the air may condense and freeze on it.
A thin layer is expected in suitable weather. Too much ice restricts airflow and reduces heat transfer, so the controller initiates defrost.
What normal defrost can look like
The fan may pause, the sound may change and vapour can rise as frost melts. Water then drains from the base.
The home should generally ride through the short interruption using the system and building’s stored heat. The frequency varies with weather, load and model.
Keep airflow and drainage clear
Remove leaves or loose debris only where this is safe and allowed by the user instructions. Do not cover or box in the unit.
Check that meltwater has a safe route and is not freezing across a path. Report damaged drainage or ice building into the fan area.
Know when to call
Photograph the ice and controller, note outdoor conditions and record any error code. Persistent loss of heat or hot water needs prompt support.
Refrigerant, electrical panels and internal sensors are engineer work. Repeated resets without diagnosis can erase useful fault information.
What to read next
Related answers and services
Questions people also ask
Is steam from the unit a fault?+
Often it is water vapour during defrost, but smoke, burning smells or electrical concerns require isolation and urgent advice.
How often should defrost happen?+
There is no fixed normal interval; weather, load and equipment determine it.
Can I remove ice myself?+
Do not chip the coil or use hot water. Keep safe external drainage clear and contact support if ice persists.
Evidence used for this answer
Figures are explained in context and links go to the independent source. Prices, tariffs, scheme rules and standards can change, so check the source again before making a financial or technical decision.
- MCS domestic heat-pump guideConsumer guidance covering design, installation, controls, handover and maintenance.
- MCS heat-pump design standardTechnical requirements for heat loss, equipment selection, domestic hot water and system design.
- Energy Saving Trust: the most efficient way to run a heat pumpGuidance on weather compensation, longer run periods, setbacks, radiators, hot water and smart energy use.