Octopus Energy does not publish a list of numbered error codes for its Cosy 6 heat pump. Faults show instead as coloured lights on the Cosy Hub and the Cosy Pods (the small room sensors), along with symptoms such as no heat, ice build-up or unusual noise. A flashing red light on the Hub is the one that means the heat pump itself has a fault.
This guide explains what each light means, what you can safely check and when to get help. For codes on other makes, see our heat pump error codes 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 problem keeps returning, we are independent F-Gas certified engineers and can book a Cosy heat pump repair. Never open either unit yourself, as both contain mains electricity and pressurised refrigerant.
Is it safe to fix an Octopus Cosy heat pump fault yourself?
You can safely handle the Hub and Pod checks and a few simple outside checks, but nothing inside the units. Changing Pod batteries, checking your router, reading the pressure gauge and looking for a tripped breaker are all fine.
Octopus is clear that leaks should not be repaired by owners, and a refrigerant leak means staying well away and calling the helpline straight away, as refrigerant can cause burns and frostbite. Refrigerant work is also legally restricted to F-Gas certified engineers.
Unqualified repairs can affect your Octopus or installer warranty, so stop at the checks below.
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.
If your Octopus Cosy heat pump is not showing a code, or you want to rule out the basics first, our guide to heat pump problems and how to fix them walks through the general checks and matches common faults to error codes across every major brand.
Which Cosy faults can you check yourself?
Most Cosy lights relate to the controls rather than the heat pump, so many can be fixed in minutes. These are the ones with a realistic homeowner check.
| Light or symptom | What it means | Safe homeowner check | Stop and call if |
|---|---|---|---|
| Hub solid yellow | Hub has lost its WiFi connection | Check your router is on and working; the Hub should reconnect itself | It stays yellow with working WiFi |
| Hub solid red | No primary Pod found | Check the app for which Pod dropped out, check its 2 x AAA batteries and move it within 5 m of the Hub | It will not reconnect |
| Pod solid red for 15 seconds | Pod has lost its Hub connection | Move the Pod within 5 m of the Hub | It keeps dropping out |
| Pod flashing red every 30 seconds | Low battery | Fit two new AAA 1.5V alkaline batteries, not rechargeables | The light continues with new batteries |
| Heat pump not working or off | Power, settings or a fault | Check both units are on, the app is connected and no breaker has tripped | Everything checks out and it still will not run |
| Not heating enough | Settings, placement or a system issue | Check Pod position, setpoints, open windows, radiator TRVs, system pressure and Hush Mode | Settings are fine and rooms stay cold |
| Ice on the outdoor unit | Often a normal defrost | Watch whether it clears on its own | Ice builds continuously or appears in warm weather |
| Puddle outside the unit | Usually normal condensate | Clear any visible debris you can reach safely | You find a leak, or water is not draining |
What are the most common Octopus Cosy fault lights and symptoms?
The signs Cosy owners report most are a flashing red Hub, Pod connection lights, rooms not getting warm enough and ice or noise from the outdoor unit. Where we add underlying causes Octopus does not mention, we label them as general engineering knowledge.
Flashing red on the Cosy Hub
This is the Hub's heat pump fault signal, and there is no further code on the Hub to decode. Octopus tells owners to contact its aftercare team. If you are out of warranty or want an independent view, we can diagnose it.
Solid red or yellow on the Cosy Hub
Solid red means the Hub cannot find its primary Pod, and solid yellow means it has lost WiFi. Neither is a heat pump fault. Fix the batteries, Pod distance or router and both should clear on their own; our guide to heat pump smart controls covers app and sensor issues more widely.
Pod lights
A Pod showing solid red for 15 seconds has lost the Hub, and one flashing red every 30 seconds needs new batteries. Solid green for 15 seconds (boost on) and fading orange for 3 seconds (boost cancelled) are not faults at all.
Heat pump not working or switched off
Octopus says to check both units are on, the app is connected and no circuit breaker has tripped, then contact the installer. Our heat pump not working guide goes through the wider checks.
Not heating enough
Octopus lists Pod location and design temperature, open windows or doors, setpoints, radiator TRVs, system pressure and Hush Mode, which limits output to 60 percent. Underlying causes can include air in the system, low pressure or blocked flow, and from general engineering knowledge sludge or scale often sit behind those. See heat pump not heating for more.
Ice build-up
Ice on the back of the unit is often a normal defrost. Continuous ice, or ice in warm weather, can mean poor airflow or low refrigerant, so contact Octopus or the installer. Our article on a heat pump frozen outside unit shows the difference.
Noise
Extra noise in cold weather or during hot water cycles is normal, according to Octopus. Loud gurgling, grinding or squealing needs the installer, and gurgling can mean air in the circuit. More in our heat pump making noise guide.
Water leak or water not draining
A puddle outside is usually normal condensate. If you find a leak or cannot see why water is not draining, contact the installer rather than repairing it; our heat pump leaking water guide explains the signs.
Refrigerant leak or damaged casing
If refrigerant is leaking, keep well away, do not try to stop it and call the helpline immediately. Damage to the casing or the evaporator (the finned coil at the back) should also be reported to aftercare as soon as possible.
Which light or symptom might you see in common situations?
Octopus only ties one light to a heat pump fault, so this table pairs each situation with the lights and symptoms its guidance does cover.
| Scenario | Cosy lights or symptoms you may see | First check |
|---|---|---|
| Cold snap, iced outdoor unit | Ice build-up; extra noise; Hub flashing red if the heat pump faults | Is the ice clearing between defrosts? Tips in our heat pumps in cold weather guide |
| Losing pressure or low pressure | Not heating enough; gurgling from air in the circuit | Read the system pressure gauge |
| Radiators lukewarm | Not heating enough | Hush Mode, setpoints and radiator TRVs |
| No hot water | No specific light in Octopus's guidance; Hub flashing red if the heat pump has faulted | Check the app and the Hub light |
| After a power cut | Hub solid yellow until WiFi returns; Pod solid red; heat pump not working | Router back on, breakers not tripped |
| Unit noisy or fan not spinning | Noise; ice build-up | Is it a cold day or a hot water cycle? |
| After a service | Hub flashing red if a fault remains; not heating enough | Ask the engineer whether pressure was restored |
How do you reset an Octopus Cosy heat pump?
Octopus does not publish a reset procedure for the Cosy 6 heat pump in its user manual or help pages, so we will not suggest one. The Hub and Pods are designed to reconnect on their own once WiFi, batteries or distance are sorted.
A flashing red Hub is a heat pump fault, and Octopus's instruction is to contact aftercare rather than reset it. Switching the system off and on repeatedly will not fix the cause and can delay a proper diagnosis.
Octopus Cosy fault light and symptom list
There is no official Cosy error code list, so this table covers every light and symptom in Octopus's published guidance, with who should deal with it.
| Light or symptom | Meaning | Who should fix |
|---|---|---|
| Hub flashing red | Heat pump fault | Octopus aftercare, then engineer |
| Hub solid red | No primary Pod found | Homeowner check |
| Hub solid yellow | Lost WiFi connection | Homeowner check |
| Pod solid red, 15 seconds | Lost Hub connection | Homeowner check |
| Pod flashing red every 30 seconds | Low battery | Homeowner check |
| Pod solid green, 15 seconds | Boost enabled (not a fault) | No action |
| Pod fading orange, 3 seconds | Boost cancelled (not a fault) | No action |
| Heat pump not working or off | Power, settings or fault | Homeowner check, then engineer |
| Not heating enough | Settings, Hush Mode, pressure or flow | Homeowner check, then engineer |
| Loud gurgling, grinding or squealing | Air in the circuit or a mechanical fault | Engineer |
| Leak, or water not draining | Pipework or drain problem | Engineer |
| Continuous ice, or ice in warm weather | Poor airflow or low refrigerant | F-Gas engineer |
| Refrigerant leak | Escaping refrigerant | Octopus helpline immediately, then F-Gas engineer |
| Damaged casing or evaporator | Physical damage | Octopus aftercare, then engineer |
Where can you find the official Octopus Cosy manual?
Octopus publishes the Cosy User Manual as a PDF, linked from its Cosy heat pump help page; section 7 covers the Hub and Pod lights and troubleshooting.
Need help with an Octopus Cosy heat pump fault?
Yes: once you have checked with Octopus or your installer, we can help as independent engineers for Cosy heat pumps across the UK. That is most useful once your cover has ended, or when a fault keeps returning and you want a second opinion.
Our engineers are F-Gas certified, so they can diagnose and repair refrigerant faults as well as pressure, flow, airflow and electrical problems. We offer same-day visits where we can, and every repair comes with our 12-month guarantee. With no heating at all, use our emergency heat pump repair service; otherwise book a heat pump repair.
An annual heat pump service catches many of the pressure, airflow and icing issues above before they cause a breakdown, and our cover plans are worth a look for ongoing support. See the heat pumps we work on, call 0333 041 5130 or contact us online.
Frequently asked questions
Does the Octopus app show Cosy error codes?
Octopus does not publish numbered codes, and its guidance points owners to the Hub and Pod lights instead. The app does help with control faults, for example by showing which primary Pod has disconnected. For anything beyond that, aftercare is the route.
When can I reach Octopus heat pump aftercare?
Octopus lists its aftercare line, 0808 196 6842, as open 8am to 8pm Monday to Saturday and 10am to 6pm on Sunday. A refrigerant leak should be reported straight away. Have the Hub light pattern and any symptoms noted before you call.
Will using an independent engineer affect my Cosy warranty?
It can while you are still covered, so speak to Octopus or your installer first. Once cover has ended, or if they agree, an independent F-Gas engineer can carry out the work. Keep records of every visit.
Does a flashing red Hub mean the compressor has failed?
No, not necessarily. It tells you the heat pump has reported a fault, and on most systems the cause is often simpler, such as airflow, pressure or a sensor. A proper diagnosis will show whether the compressor is involved.
How often should a Cosy heat pump be serviced?
Once a year is standard good practice for heat pumps, and it may be a warranty condition, so check your paperwork. A service checks pressure, airflow and the outdoor coil, which helps prevent many of the problems above. Our heat pump annual service checklist shows what should be covered.
