What the F2 code means on an Ideal boiler
F2 is a flame loss fault. The boiler lit successfully, but part way through heating or hot water it could no longer detect a flame and shut down. This is different from L2, where the boiler never manages to light in the first place.
Once the flame is lit, a sensor keeps checking that it is still burning. If the flame disappears, the gas valve closes straight away so unburnt gas cannot escape. On most Logic models the boiler may then try to relight. If it keeps losing the flame, it shows F2 and waits for you to press reset. You may notice the hot water running cold part way through a shower, or radiators cooling down even though the heating is on.
Common causes of an Ideal F2 fault
Because the boiler did light, the gas supply was at least partly working. The fault usually comes from something that changes while the boiler runs.
Gas supply interruption
A prepayment meter running out of credit mid-use is a classic cause. Low gas pressure can also do it, particularly when several gas appliances are running at once. A gas hob, gas fire and boiler all firing together may draw more than an undersized supply pipe can deliver.
Frozen or blocked condensate pipe
As the boiler runs, it produces condensate. If the pipe is partly frozen or blocked, water builds up in the boiler while it is running and the flame can be lost. In winter this often happens a few minutes after start-up, sometimes with gurgling noises.
Worn or dirty flame sensing electrode
If the electrode is coated or slightly out of position, it may only pick up a weak signal. The boiler lights, then decides it has lost the flame and shuts down.
Flue problems
The flue carries waste gases out and brings fresh air in. A blocked, damaged or badly sealed flue affects combustion and can cause the flame to fail. This needs checking by a professional.
Gas valve or PCB fault
Less commonly, the gas valve or control board develops an intermittent fault that cuts the gas while the boiler is running.
| Cause | Typical sign | Who fixes it |
|---|---|---|
| Prepayment credit ran out | Meter shows no credit, hob will not light | You |
| Low gas pressure | F2 when other gas appliances are on | Gas Safe engineer or gas network |
| Frozen condensate pipe | Freezing weather, gurgling sounds | You, with warm water |
| Electrode | Boiler lights then cuts out repeatedly | Gas Safe engineer |
| Flue fault | Damaged or obstructed flue outside | Gas Safe engineer |
Safe checks you can do yourself
- Check the gas supply. Try your gas hob. On a prepayment meter, check your credit and emergency credit. Make sure the lever on the gas meter is in line with the pipe.
- Check the gas isolation valve under the boiler. The handle should be in line with the pipe. If it is partly turned, the supply to the boiler may be restricted. If you are unsure why it has been moved, ask an engineer.
- Note what else was running. If F2 only happens when the hob or a gas fire is on, tell your engineer. It suggests a gas pressure issue rather than a boiler fault.
- Check the condensate pipe in cold weather. Thaw any frozen section with warm (not boiling) water or a hot water bottle. Our frozen condensate pipe guide shows where to look.
- Press reset. Follow the reset method in your manual. On many models you hold the button for a few seconds.
- Stop after two or three attempts. If F2 returns, leave the boiler off and call a Gas Safe registered engineer.
If you smell gas, do not reset the boiler or use electrical switches. Open doors and windows and call the National Gas Emergency Service on 0800 111 999. Never try to inspect or clear the flue yourself, and never remove the boiler casing.
When to call a Gas Safe engineer
If the gas supply is fine, the condensate pipe is clear and F2 keeps returning, you need an engineer. Repeated flame loss can come from the electrode, gas valve, flue or control board, and all of these are inside the boiler or part of its gas and flue system. Only a Gas Safe registered engineer should work on them.
An engineer will usually check the working gas pressure at the boiler while other appliances run, inspect and clean or replace the electrode, check the flue for damage or blockage, and look at the condensate trap. If the gas pressure at your meter is too low, they may refer you to your gas network to check the meter regulator.
Typical repair costs in the UK
These are typical ranges for parts and labour. Your price depends on the model, the region and whether the engineer has the part with them.
| Repair | Typical cost |
|---|---|
| Engineer call-out and diagnosis | Typically £80 to £150 |
| Replacement electrode | Typically £100 to £180 |
| Replacement gas valve | Typically £250 to £450 |
| Replacement PCB | Typically £300 to £550 |
| Thawing a frozen condensate pipe yourself | Free |
If your boiler is under warranty, check with Ideal before booking an independent engineer, as the repair may be covered.
How to stop F2 coming back
- Service the boiler every year. A service includes checking the electrode, flue and condensate trap, which covers most of the internal causes of F2. Our guide to boiler service costs explains what is included.
- Protect the condensate pipe. Lagging the outside section helps prevent winter freezing.
- Keep prepayment credit topped up. Running out while the boiler is firing is an easy cause to avoid.
- Keep the area around the flue terminal clear. Do not let plants, sheds or stored items grow or build up near it, and report any visible damage to an engineer.