What the LC code means
Most Ideal lockout codes, such as L2 or L6, are cleared by pressing reset. That is fine once or twice, but repeatedly resetting a boiler with a real fault can be unsafe. For example, pressing reset over and over on a boiler that keeps failing to light means the burner keeps trying to ignite gas without a proper flame.
To prevent that, Ideal boilers count restarts. On the Logic Combi2 and Logic Max ranges, Ideal's manuals list LC as five restarts within 15 minutes, with the instruction to turn the power off and on. Once the limit is reached, the reset button stops working and the boiler shows LC instead.
LC is not a fault in itself. It is a sign that the boiler has been locking out repeatedly with another code, and that code is the one that needs fixing.
Common causes of LC
A repeating ignition lockout
The most common story is an L2 ignition lockout that keeps coming back. Someone presses reset, the boiler tries to light and fails, and after a few cycles LC appears. The underlying cause is often the gas supply, a prepayment meter out of credit or a frozen condensate pipe.
Repeated flame loss or false flame
An F2 flame loss fault or an L6 false flame lockout that keeps recurring can also lead to LC if the boiler is reset each time.
Overheat or circulation lockouts
An L1 lockout caused by poor circulation can repeat quickly if the pump or system has a problem, pushing the restart count up.
Power interruptions
Less often, repeated power cuts or a loose supply connection can make the boiler restart several times in a short spell.
| Underlying cause | Typical sign | Who fixes it |
|---|---|---|
| Gas supply or prepayment credit | Hob will not light either | You, by restoring the supply |
| Frozen condensate pipe | Freezing weather, gurgling from the boiler | You, by thawing the pipe |
| Ignition or flame sensing fault | L2, F2 or L6 before LC appeared | Gas Safe engineer |
| Circulation or pump problem | L1 before LC appeared | Gas Safe engineer |
| Power supply problem | Lights flickering or tripping | Electrician or Gas Safe engineer |
Safe checks you can do yourself
- Try to remember which code the boiler showed before LC. If you are not sure, the engineer can often read the fault history from the boiler.
- Check your other gas appliances. If the hob will not light, the problem is the gas supply rather than the boiler.
- If you have a prepayment meter, check the credit and top up if needed.
- Check the gas isolation valve under the boiler. The handle should be in line with the pipe, which means it is open.
- In freezing weather, check the condensate pipe outside for ice and thaw it with warm (not boiling) water. Our frozen condensate pipe guide explains how.
- Turn the boiler off at the fused spur, wait a minute and turn it back on. This clears LC on the models that use it.
- If the original code comes back, reset it no more than once or twice more. After that, leave the boiler off and call an engineer.
If you smell gas, do not reset the boiler or turn it off and on. Turn off the gas at the meter if it is safe to do so, open doors and windows, leave the property and call the National Gas Emergency Service on 0800 111 999.
When to call a Gas Safe engineer
If you have restored the gas supply or thawed the condensate pipe and the boiler now runs normally, you may not need anyone. But if the original lockout keeps returning after a power restart, stop resetting and call a Gas Safe registered engineer. Seeing LC means the boiler has already had several failed attempts, and more resets are very unlikely to help.
When you book, give the engineer the code that appeared before LC if you know it. That tells them far more than LC on its own. It also helps to say how many times the boiler was reset, whether your other gas appliances were working and whether the weather was freezing at the time. With that information they can usually narrow the problem down to the gas supply, the ignition and flame sensing parts, or the water circulation side of the boiler before they arrive.
Call sooner if LC appears again within a day or two of clearing it. A boiler that keeps hitting the restart limit has a fault that is not going away, and running it on repeated resets only adds wear to parts such as the electrode and fan.
Typical repair costs in the UK
Clearing LC itself costs nothing. What you pay depends entirely on the underlying fault. These typical ranges include parts and labour.
| Job | Typical UK cost |
|---|---|
| Engineer call-out and diagnosis | Typically £80 to £150 |
| Ignition or flame sensing electrode replacement | Typically £100 to £180 |
| Rerouting or insulating the condensate pipe | Typically £100 to £250 |
| Replacement pump, fitted | Typically £250 to £450 |
| Gas valve replacement | Typically £250 to £450 |
How to stop LC coming back
The simplest rule is to stop after two or three resets and find out why the boiler keeps locking out. Keep prepayment credit topped up in winter, and ask an engineer about insulating an exposed condensate pipe. A yearly service catches worn electrodes and circulation problems early. Our boiler service cost guide explains what it covers. It is also worth reading up on the original code, so you know which checks are safe to make yourself next time.