On an Ideal Logic Air heat pump, an iced-up outdoor unit often shows as fault 370 with sub-code F15 (airflow fault) or F17 (fan fault). Some frost is normal, but ice that stays put alongside one of these codes needs attention.
If the code comes back after one reset, book an engineer rather than resetting again. We carry out Ideal heat pump repairs across the UK. For every other fault, see our full guide to Ideal heat pump error codes.
Please read first: this guide is here to help you understand what your Ideal heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their manuals and codes can differ between models and software versions, so always check the official Ideal 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 370 F15 and F17 mean on an Ideal heat pump?
Fault 370 means the outdoor unit has a problem, and the F sub-code says what it is: F15 is an airflow fault and F17 is a fan fault. Ideal's fault list for the Logic Air names both, and its user guide advises clearing leaves and snow from the unit.
The controller shows the fault as a number with a bell icon at the top of the screen. To see the F sub-code, go to the control box on the cylinder and turn the wheel to the bar graph symbol to open the Info screen. Write the full code down before you do anything else.
Is ice on a heat pump normal?
Yes, some frost is normal. Ideal's user guide says frost, steam or extra water from the unit is normal during an automatic defrost, which lasts a few minutes.
The guide also says defrosts happen more often around 2.5°C and less often below 0°C, so a busy defrost pattern on a raw, damp day is expected. It becomes a fault when ice stays on the coil for hours or builds up around the fan, which is when F15 or F17 tends to appear. Our guides to the heat pump defrost cycle and a heat pump frozen outside unit explain the difference.
Why do F15 and F17 appear in cold weather?
They appear when something stops air moving freely through the outdoor unit, and in winter that is usually ice, snow or leaves. Ideal's user guide points to leaves and snow blocking the unit; the other causes below are general engineering knowledge, not from Ideal's manual.
- Ice on the coil or fan when defrost struggles. Ice that builds between defrosts chokes the airflow and can lock the fan.
- Failed defrost sensor or valve. A faulty defrost thermistor (370 F9 on the Logic Air) can cause poor or mistimed defrosting.
- Low water flow. Sludge, a blocked filter or strainer, or an air lock leaves less warm water available to melt ice during defrost. Ideal's guide links blocked filters and air in the pipework to 370 F27.
- Low system pressure. Ideal's guide says pressure should be 1 to 1.5 bar. Pressure that keeps falling is covered in heat pump losing pressure.
- Frozen or blocked condensate drain. Meltwater that cannot run away refreezes around the base and lower coil.
- Unit sitting too low. A unit without raised feet can sit in its own meltwater or drifting snow.
- Failed fan motor. A motor can fail on its own, without any ice.
- Low refrigerant. A leak makes the coil run colder and ice faster, and can show as 370 F20 (outdoor low pressure).
If the heat pump stops working altogether, our guide to air source heat pump not working covers the wider checks.
What can you safely check yourself?
You can make a few outside checks without tools, as long as you never open the unit. Work through these in order:
- Keep the power on. Defrost and frost protection need power, so do not leave the heat pump switched off at the isolator in freezing weather.
- Clear around the unit. From outside the casing, clear leaves and snow from the front, back, top and underneath by hand or with a soft brush. Ideal's guide says to clean the unit with a weak soap solution, never high-pressure water.
- Check the condensate drain. Make sure meltwater can run away from the base. If the drain path is iced, thaw it with lukewarm water only, never boiling.
- Check the pressure gauge and valves. Ideal's guide says the gauge should read 1 to 1.5 bar, topped up through the filling loop if it is below 1 bar. Check the isolation valves are open too.
- Check your settings. If you are going away, use a holiday or frost setting rather than switching off. Our guide to heat pump holiday settings explains how.
- Reset once. Ideal's general reset is to switch off the rotary isolator near the outdoor unit, wait 1 minute, switch it back on and give the system a few minutes to boot.
What not to do
- Never chip, scrape or prise ice off the coil or fan.
- Never use boiling water, a heat gun or a hairdryer on the coil.
- Never remove panels or touch wiring, boards or sensors.
- Never touch the refrigerant circuit. That work is restricted by law to F-Gas certified engineers.
When should you call an engineer?
Call an engineer if F15 or F17 comes back after one reset, or straight away if the fan is iced in or will not turn. Other clear triggers are:
- Ice still covering the coil several hours after you cleared around the unit.
- 370 F20 (outdoor low pressure) or F14 (pressure sensor), which point at the refrigerant side and need an F-Gas certified engineer.
- 370 F27 that stays after topping up to 1 to 1.5 bar, or pressure that keeps dropping.
- A fan that scrapes, knocks or hums without turning.
- No heating or hot water in freezing weather, especially with vulnerable people at home.
Refrigerant leaks can only be found, repaired and recharged legally by an F-Gas certified engineer. Topping up refrigerant is never a homeowner job.
How can you stop it happening again?
Regular servicing and a well-placed, well-drained unit prevent most repeat icing. These points are general engineering advice rather than Ideal instructions, apart from keeping the unit clear, which Ideal's guide also covers:
- Book an annual service. An engineer checks the defrost sensors, fan, coil, pressure and flow before winter. Our annual service checklist shows what is included.
- Keep the water side clean. Clean the magnetic filter regularly. Systems full of sludge may need a heat pump powerflush.
- Check frost protection. Make sure inhibitor, antifreeze or freeze-protection valves are in place where your installer fitted them.
- Insulate outdoor pipes. Good lagging on the flow and return pipes cuts heat loss in a frost.
- Lift and drain the unit. Raised feet or a stand, with a clear path for meltwater, stop ice forming around the base.
- Keep it clear. Keep the unit away from drifting snow, roof run-off and plants, and clear leaves through autumn.
For more cold-weather habits, read our heat pump winter tips and our guide to running a heat pump in cold weather.
Other Ideal codes you might see in a cold snap
A freezing spell can bring up other Logic Air faults alongside, or instead of, F15 and F17. Each code links to its entry in our Ideal error code guide.
| Code | Ideal meaning | Why it can show in cold weather |
|---|---|---|
| 370 F9 | Defrost thermistor | Failed sensor or loose plug |
| 370 F20 | Outdoor low pressure | Iced coil or refrigerant loss |
| 370 F19 | Compressor temperature fault | Overheating with blocked airflow |
| 370 F27 | No water flow | Low pressure, blocked filter or air in the pipework |
| 370 F24 | Circulation pump error | Failed pump or air lock |
| 10 | Outside sensor fault | Failed sensor or damaged cable |
Need help with a frozen Ideal heat pump?
We repair Ideal Logic Air heat pumps across the UK. Our F-Gas certified engineers deal with iced coils, airflow and fan faults, defrost problems and refrigerant leaks, and we are MCS accredited. If your home is cold, our emergency heat pump repair team offers same-day visits where possible.
We read the full code, find the cause and carry out the heat pump repair it needs, backed by a 12-month guarantee. To avoid a repeat next winter, book annual heat pump servicing or spread the cost with one of our cover plans.
Call 0333 041 5130 or contact us online.
Frequently asked questions
Can I cover my Ideal outdoor unit in winter?
No, do not wrap or cover the unit, because it needs free airflow to heat and to defrost, and a cover can bring on F15. If snow or roof run-off is a problem, ask an engineer about a canopy that keeps the clearances in your manual.
Will a frozen outdoor unit damage my heat pump?
A light frost does no harm. Running for long periods with a solid block of ice strains the fan and compressor, which is why the Logic Air flags F15 and F17. Acting early usually keeps the repair small.
Why is the fan running but the unit still icing up?
A turning fan does not mean air is getting through, because ice or leaves on the coil can still block it. Defrost or flow problems can also let ice build even with the fan working, so an engineer should check if it keeps happening.
Does the code clear itself once the ice has gone?
It may, but do not rely on it. If the fault is still showing once the unit is clear, do Ideal's isolator reset once and call an engineer if it returns.
Does freeze damage count under my warranty?
That depends on your warranty terms and whether the unit has been serviced as required. Keep your service records and installation paperwork, and check the terms before anyone works on the unit.
