Boiler
F2
The F2 error code on an Ideal boiler indicates a flame failure — the boiler has tried to ignite but cannot detect a stable flame, leaving you without heating or hot water. It can range from a minor, fixable issue to a fault requiring a Gas Safe registered engineer.
What does this error mean?
Your Ideal boiler uses a flame detection sensor (known as an ionisation probe) to confirm a flame is present after ignition. When the boiler fires up but the sensor doesn’t detect a flame within a set time, it locks out and displays F2 as a safety measure. This prevents unburned gas from accumulating — so the lockout itself is working exactly as intended.
Est. repair cost
£150–£300 for igniter or flame sensor replacement; £300–£500 for gas valve replacement. New boiler: £1,800–£2,800 installed.
🔍 Likely causes
🛠️ Step-by-step fix
Check your gas supply first: confirm other gas appliances (cooker, hob) are working. If they aren’t, contact your gas supplier — there may be a supply issue or your prepayment meter may need topping up.
Check for a frozen condensate pipe: in cold weather, locate the plastic waste pipe that runs outside your home. If frozen, thaw it carefully with warm (not boiling) water and a hot water bottle. Ideal’s manual includes a reset procedure for this specific fault.
Reset the boiler: once any obvious cause is resolved, press and hold the reset button (usually marked with a flame symbol) for 3–5 seconds. Allow the boiler a full ignition cycle before concluding it has failed.
Reset up to three times: if the F2 clears then returns, attempt a reset no more than three times total. Repeated failed ignitions can allow unburned gas to build up — stop after three attempts.
Do not attempt any further DIY: do not open the boiler casing, touch the igniter, clean the flame sensor, or inspect the gas valve yourself. These tasks legally require a Gas Safe registered engineer in the UK.
📞 When to call a professional
If the F2 error persists after a reset and there is no frozen condensate pipe or gas supply issue, stop and call a Gas Safe registered engineer — do not keep resetting. Tell them: ‘My Ideal boiler is showing an F2 flame failure lockout; it attempts ignition but won’t establish a flame.’ This helps them arrive prepared with the likely parts (igniter, ionisation probe, or gas valve).
⚖️ Repair or replace?
A typical F2 repair — replacing an igniter or flame sensor — costs £150–£300 including labour, with a gas valve replacement reaching £300–£500. If your Ideal boiler is over 10–12 years old and repairs exceed £400, replacing it with a new A-rated combi boiler (typically £1,800–£2,800 installed) is usually the more cost-effective long-term choice. For a boiler under 8 years old still within warranty, contact Ideal directly before paying for any repair.