A frozen or iced-up Aira heat pump means frost on the outdoor unit is not clearing as it should, and Aira does not publish numbered error codes for it. Instead, you may notice heavy ice on the outdoor unit, a red indicator light on the indoor unit or an alert in the Aira Home Energy app.
Most Aira owners have aftercare from Aira, so contact Aira Customer Care first, especially while you are under warranty. If you are out of warranty, want a second opinion or the ice keeps coming back, book a heat pump repair with our independent F-Gas certified engineers. For other Aira lights and alerts, see our guide to Aira heat pump error codes and fault lights.
Please read first: this guide is here to help you understand what your Aira heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their guidance and alerts and fault lights can differ between models and software versions, so always check the official Aira support pages for changes before acting on anything here. Do not attempt anything that could be dangerous, and avoid any work that could void your warranty. If in doubt, call a qualified heat pump engineer.
What do the lights and alerts tell you on a frozen Aira heat pump?
They tell you something needs attention, but Aira does not publish a freeze-specific code or light. Aira's notifications support page lists a pulsating red light in the centre and one on the left of the indoor unit, and we have not been able to confirm the published meaning of either, so we will not guess.
From general engineering knowledge, a red pattern usually signals an active alert. Open the Aira Home Energy app, screenshot any message with the time, and pass it to Aira Customer Care. Aira also says the system monitors itself and reports to its own team, so they may already know about the problem when you call.
The most reliable sign of a freezing problem is what you can see: thick ice on the outdoor unit that does not clear, combined with heating or hot water dropping off.
Is ice on a heat pump normal?
Yes, a light frost on the outdoor unit is normal in cold, damp weather, and the heat pump clears it by running a defrost. You may hear the unit change sound and see water dripping underneath while it does. Our guide to the heat pump defrost cycle explains what happens.
It is not normal for ice to stay after a defrost, keep thickening through the day or encase the fan. That points to a fault worth reporting, and our article on a heat pump frozen outside unit shows the difference.
Why does an Aira heat pump freeze up in cold weather?
Aira's own freezing advice names four causes: restricted airflow, low refrigerant, dirty coils and faulty components such as the defrost control. Its maintenance advice also points to checking system pressure when heating stops.
The following are general engineering knowledge rather than Aira's own wording:
- Low flow from sludge in radiators or pipework, which weakens the defrost.
- A blocked strainer or filter on the heating circuit.
- Air locks that stop water circulating.
- Low system pressure, often from a small leak; see heat pump losing pressure.
- A failed defrost sensor or valve, so a defrost does not start or finish.
- A frozen or blocked condensate drain, so melt water refreezes at the base of the unit.
- Snow or leaves blocking airflow, or a unit sitting too low to the ground.
- Low refrigerant, which only an F-Gas engineer can diagnose.
What can you safely check yourself?
You can make a few simple checks from outside the unit, and Aira itself advises clearing debris before calling Customer Care.
- Keep the power on. Frost protection needs power, so do not switch the heat pump off at the isolator.
- Clear around the outdoor unit. From outside, brush away loose snow, leaves and debris around and under the unit by hand.
- Check the condensate drain path. Make sure melt water can drain away. If the outlet is frozen, thaw it only with lukewarm water, never boiling.
- Check pressure and valves. Read the pressure gauge and check radiator valves are open.
- Use holiday settings, not the off switch. If you are away, use any away or holiday setting your system offers rather than switching off; see our guide to heat pump holiday settings.
- Do not reset. Aira does not publish a reset procedure, so report the problem to Aira rather than power-cycling the unit.
What not to do
- Never chip, scrape or pick at ice on the coil or fins.
- Never use boiling water, a heat gun or a hairdryer on the coil.
- Never remove panels or touch wiring inside either unit.
- Never touch the refrigerant circuit, which is legally restricted to F-Gas certified engineers.
When should you call Aira or an engineer?
Call Aira Customer Care if ice persists after you have cleared debris, which is Aira's own advice. Call straight away if:
- Ice stays after a defrost, keeps thickening or covers the fan.
- A red light or app alert appears and does not clear.
- Heating or hot water drops off during the cold spell.
- Pressure keeps falling after a top-up.
Aira names low refrigerant and faulty defrost parts among the causes, and refrigerant work is legally restricted to F-Gas certified engineers. If you are out of warranty or Aira's visit has not fixed it, our independent engineers can take a look. If the whole system has stopped, see our guide to common air source heat pump problems.
How can you stop it happening again?
Keeping airflow clear and the water side healthy prevents most repeat icing. Aira's winter advice focuses on airflow and pressure; the rest of this list is general engineering knowledge:
- Keep up annual servicing. It catches pressure, airflow and defrost issues early; our heat pump annual service checklist shows what should be covered.
- Keep filters clean. A clean magnetic filter or strainer keeps flow up.
- Deal with dirty system water. A heat pump powerflush can clear sludge that slows defrost.
- Protect the water circuit. Where fitted, the correct antifreeze or inhibitor, or freeze-protection valves, help guard outdoor pipework.
- Insulate exposed pipework running to the outdoor unit.
- Raise the unit and keep drainage clear so snow and melt water cannot build up underneath.
- Leave space around the unit and keep plants and stored items away from it.
For more cold-weather advice, read our heat pump winter tips and guide to heat pumps in cold weather.
Other Aira alerts you might see in a cold snap
Aira has no numbered codes, so these are the lights, alerts and symptoms that tend to show up alongside icing.
| Light, alert or symptom | What it tells you | More detail |
|---|---|---|
| Pulsating red light, centre or left side | Listed by Aira; meaning not confirmed by us, so check the app | Aira error codes and fault lights |
| Error shown in the app | Wording varies; record it for Aira | Aira error codes and fault lights |
| No heating | Check settings, power and pressure | Aira error codes and fault lights |
| Out of hot water | Check the schedule and boost in the app | Aira error codes and fault lights |
| Noise from the outdoor unit | Check for ice or debris near the fan | Aira error codes and fault lights |
Need help with a frozen Aira heat pump?
Yes: once Aira aftercare has been your first call, we can help as independent F-Gas certified engineers for Aira heat pumps across the UK. That is most useful when you are out of warranty or want a second opinion on ice that keeps coming back.
We diagnose airflow, flow, pressure, defrost and refrigerant faults, and every repair carries our 12-month guarantee. With no heating in a cold snap, our emergency heat pump repair team aims for same-day visits where possible; otherwise book a heat pump repair. Regular heat pump servicing and our cover plans help prevent repeat icing. See the heat pumps we work on, call 0333 041 5130 or contact us online.
Frequently asked questions
Why is steam coming off my Aira outdoor unit?
A short burst of vapour during or just after a defrost is normal on heat pumps generally, as melted frost warms and evaporates. It should stop within seconds or minutes. Constant steam with no ice clearing is worth reporting to Aira.
Should I cover my Aira outdoor unit in winter?
No, not with a full cover or tarpaulin. The unit needs free airflow to work, and a cover can make icing worse. Ask Aira or your installer before fitting any canopy or shelter.
Does icing mean my heat pump is too small?
Not necessarily. Every air source heat pump frosts up in cold, damp weather, and a correctly sized unit simply defrosts more often. Ice that never clears points to a fault rather than sizing.
Does a frozen heat pump cost more to run?
It can. Ice on the coil cuts how much heat the unit can draw from the air, and extra defrosts use energy. Getting persistent icing fixed helps both comfort and running costs.
Could my pipes freeze if the heat pump stops?
They could if the system is switched off for a long spell in very cold weather, which is why we suggest keeping the power on. Insulated outdoor pipework and any freeze protection fitted at installation reduce the risk. If the heat pump has stopped completely during a freeze, call Aira or an engineer quickly.
