A frozen or iced-up Octopus Cosy 6 means ice on the outdoor unit is not clearing between defrosts, and Octopus does not publish numbered error codes for it. What you may see instead is continuous ice on the unit, rooms not warming up or, if the heat pump reports a fault, a flashing red light on the Cosy Hub.
Most Cosy owners have aftercare through Octopus or their installer, so check that first; Octopus lists 0808 196 6842 for heat pump aftercare. If you are out of warranty, want a second opinion or the ice keeps returning, book a heat pump repair with our independent F-Gas certified engineers. For every other Cosy light, see our guide to Octopus Cosy heat pump error codes and fault lights.
Please read first: this guide is here to help you understand what your Octopus Energy Cosy heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their manuals and alerts and fault lights can differ between models and software versions, so always check the official Octopus Cosy user manual 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 Cosy lights tell you when it freezes?
The Cosy Hub only has one heat pump fault signal, a flashing red light, and there is no further code behind it to decode. If ice has led to a fault, that is the light you will see, and Octopus's instruction is to contact its aftercare team.
Other Hub and Pod lights relate to the controls rather than freezing. A solid yellow Hub means lost WiFi, a solid red Hub means no primary Pod found, and Pod lights cover connection, battery and boost. So the clearest sign of a freezing problem is what you see outside: ice that keeps building, or ice in warm weather.
Is ice on a heat pump normal?
Yes, Octopus says ice on the back of the Cosy unit is often just a normal defrost. Extra noise in cold weather is also described as normal, and a puddle outside the unit is usually condensate from defrosting. Our guide to the heat pump defrost cycle explains what is going on.
Octopus is clear about the warning signs: continuous ice build-up, or ice in warm weather, can mean poor airflow or low refrigerant. Our article on a heat pump frozen outside unit helps you tell the two apart.
Why does a Cosy heat pump freeze up in cold weather?
Octopus names two causes for continuous ice: poor airflow and low refrigerant. Its guidance also lists water not draining and system pressure as checks, which both matter in a freeze.
The following are general engineering knowledge rather than Octopus'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; Octopus notes that gurgling can mean air in the circuit.
- 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 under the unit.
- Snow, leaves or debris blocking airflow, or a unit sitting too low to the ground.
- Low refrigerant, which only an F-Gas engineer can test and fix.
What can you safely check yourself?
You can make a few simple checks from outside the unit, and Octopus says to clear any visible debris you can safely reach.
- 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 water can drain away. If the outlet is frozen, thaw it only with lukewarm water, never boiling.
- Check pressure and valves. Read the system pressure gauge and check radiator valves and TRVs are open.
- Use holiday settings, not the off switch. If you are away, use any away or holiday setting your controls offer rather than switching off; see our guide to heat pump holiday settings.
- Do not reset. Octopus does not publish a reset procedure, and a flashing red Hub should go to aftercare rather than be power-cycled.
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. If refrigerant is leaking, keep well away and call the Octopus helpline immediately, as it can cause burns and frostbite.
When should you call Octopus or an engineer?
Call Octopus aftercare or your installer as soon as ice builds continuously or appears in warm weather, which is Octopus's own advice. Call straight away if:
- The Cosy Hub is flashing red.
- Water is not draining, or you find a leak.
- Rooms stay cold after you have checked Pod placement, setpoints, TRVs and Hush Mode.
- The casing or evaporator, the finned coil at the back, is damaged.
Low refrigerant is one of the two causes Octopus names, and refrigerant work is legally restricted to F-Gas certified engineers. If you are out of warranty or aftercare has not fixed it, our independent engineers can help. If the heat pump has stopped altogether, see our guide to an air source heat pump not working.
How can you stop it happening again?
Clear airflow and healthy system water prevent most repeat icing. Octopus's guidance covers airflow, drainage and pressure; the rest of this list is general engineering knowledge:
- Book an annual service. It catches airflow, pressure and defrost problems early; see our heat pump annual service checklist.
- Keep filters clean. A clean magnetic filter or strainer keeps flow up.
- Clear sludge. A heat pump powerflush can restore flow in a dirty system.
- Protect the water circuit. Where fitted, the correct antifreeze or inhibitor, or freeze-protection valves, help guard outdoor pipework.
- Insulate exposed pipes running to the outdoor unit.
- Raise the unit and keep drainage clear so snow and melt water cannot build up underneath.
- Keep space around the unit free of plants, bins and stored items.
For more seasonal advice, see our heat pump winter tips and guide to heat pumps in cold weather.
Other Cosy lights and symptoms you might see in a cold snap
The Cosy has no numbered codes, so these are the lights and symptoms from Octopus's guidance that tend to appear in cold weather.
| Light or symptom | What it tells you | More detail |
|---|---|---|
| Hub flashing red | Heat pump fault; contact Octopus aftercare | Cosy error codes and fault lights |
| Continuous ice, or ice in warm weather | Poor airflow or low refrigerant | Cosy error codes and fault lights |
| Extra noise in cold weather | Described by Octopus as normal | Cosy error codes and fault lights |
| Not heating enough | Check Pod placement, setpoints, TRVs, pressure and Hush Mode | Cosy error codes and fault lights |
| Water not draining | Contact the installer rather than repairing it | Cosy error codes and fault lights |
| Hub solid yellow after a power cut | Lost WiFi; should reconnect once the router is back | Cosy error codes and fault lights |
Need help with a frozen Cosy heat pump?
Yes: once you have checked with Octopus or your installer, we can help as independent F-Gas certified engineers for Cosy heat pumps across the UK. That is most useful once your cover has ended, or when ice keeps returning and you want a second opinion.
We diagnose airflow, flow, pressure, defrost and refrigerant faults, and every repair comes with 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
Can Hush Mode leave rooms cold in a freeze?
It can. Octopus says Hush Mode limits the heat pump's output to 60 percent, which may not keep up on the coldest days. If rooms are cool during a cold snap, check whether Hush Mode is on before assuming a fault.
What should I tell Octopus aftercare when I call?
Tell them the Hub light pattern, when the ice started and whether it clears between defrosts. A photo of the outdoor unit helps, as does noting any noise or water not draining. That information speeds up diagnosis whoever attends.
Should I cover my Cosy outdoor unit in winter?
No, not with a full cover or tarpaulin. The unit needs free airflow, and poor airflow is one of the causes of icing Octopus names. Ask Octopus or your installer before fitting any shelter.
Why is steam coming off the outdoor unit?
A short cloud of vapour during or just after a defrost is normal on heat pumps generally. It should clear within seconds or minutes. Steam with ice that never clears is worth reporting.
Does a frozen heat pump cost more to run?
It can. Ice on the coil reduces how much heat the unit can draw from the air, and extra defrosts use energy. Fixing persistent icing helps both comfort and running costs.
