Boiler Ignition Lockout: What It Means and the Code for Your Boiler

A boiler ignition lockout means the boiler tried to light, did not detect a flame within a few seconds, and shut itself down as a safety measure. It stays off until someone resets it. Every manufacturer shows it with its own code: EA or 227 on a Worcester Bosch, F28 on a Vaillant, L2 on an Ideal, E133 on a Baxi, and F1, F4 or F28 on a Glow-worm, depending on the model. You can check the gas supply and the condensate pipe and reset the boiler once. If it locks out again, the cause is inside the boiler and needs a Gas Safe registered engineer.

What an Ignition Lockout Actually Is

An ignition lockout is a safety shutdown, not a breakdown in itself. The boiler has stopped because it could not prove that a flame was burning when it should have been.

Each time a modern boiler fires, it runs through the same sequence. The fan starts, the spark electrode begins sparking, the gas valve opens and a flame sensor checks for a flame. If no flame is detected within a set time, the boiler closes the gas valve and tries again. After a set number of failed attempts, it locks out and shows a code. Unlike some faults, it will not restart on its own when conditions improve. It needs a manual reset.

Ignition Lockout Codes by Brand

The code on the display tells you whether you are looking at an ignition lockout, so start by matching it to your boiler's make. The brand is printed on the front panel.

• Worcester Bosch: EA, often shown together with Worcester fault code 227, means the boiler tried to light but no flame was detected.
• Vaillant: F28 means the boiler failed to light at start-up. F29 means it lit, the flame went out during operation, and it could not relight.
• Ideal: L2 is an ignition lockout. F2 is a flame loss code in the same family.
• Baxi, Potterton and Main: E133 means ignition failure or an interrupted gas supply. E128 means the flame has been lost repeatedly.
• Glow-worm: older models use F1 and F4 for ignition and flame detection faults, while newer ones use F28 and F29 in the same way as Vaillant.

Vokera has used several control systems, so the same ignition fault can show a different code from one model to the next. Our guide to Vokera boiler problems and fault codes covers those models.

Other manufacturers use their own codes, so check the manual if yours is not listed. Our boiler fault codes reference has a page for each of the codes above with more detail.

Failed to Light or Lost the Flame?

Some codes mean the boiler never lit, and others mean it lit and then lost the flame. The difference is useful because it points an engineer towards different parts.

A boiler that never lights often has a problem with the spark, the gas supply reaching the burner, or the gas valve not opening. A boiler that lights and then drops out is more often struggling to keep proving the flame, which points to a dirty or worn flame sensor, low gas pressure under load, or a problem with the air and flue side. If you can, watch or listen when the boiler tries to fire. Hearing it click and whoosh briefly before it stops is a sign that it is lighting and then losing the flame.

What You Can Safely Check Before Calling

A few checks will either solve the problem or rule out the simple causes. None of them involves opening the boiler.

• Is gas reaching the house? Try the hob or another gas appliance.
• Prepayment meter. Check it has credit and has not cut off the supply.
• Gas isolation valve. The lever on the gas pipe under the boiler should be in line with the pipe. If it has been knocked across, the boiler gets no gas.
• Condensate pipe. In freezing weather, check the plastic pipe running outside. A frozen or blocked condensate pipe is one of the most common causes of winter lockouts. Gently warming a frozen section with a warm, damp cloth, never boiling water, and then resetting the boiler often clears it.
• Recent work. If the gas meter or supply pipe has just been worked on, mention it to the engineer, as it can affect how the boiler lights.

If you smell gas, do not reset the boiler. Turn the gas off at the meter, avoid electrical switches, open the windows and call the National Gas Emergency Service on 0800 111 999.

Why You Should Only Reset Once

Reset the boiler once after your checks. If it locks out again, stop there.

The lockout exists because the boiler could not confirm that gas was burning safely. Pressing reset over and over asks it to repeat the same failed sequence and does nothing to fix a worn electrode or a faulty gas valve. Some boilers also limit how many resets they will accept in a short period. Our article on what it means when a boiler won't reset explains why a code that keeps returning is the boiler telling you the fault is still there.

What an Engineer Will Look For

If the checks above do not clear it, the fault is almost always in the ignition or combustion parts of the boiler. These are the causes a Gas Safe registered engineer will test for:

• Ignition electrode: worn, cracked or out of position, so the spark is weak or misses the burner.
• Flame sensor: coated in deposits, so it cannot detect a flame that is actually there.
• Gas valve: not opening fully, or not opening at all.
• Gas pressure: too low at the boiler, even if the hob seems fine.
• Condensate and flue: a blockage that backs up inside the boiler or upsets the air supply.
• Control board: less often, the board itself is not driving the ignition sequence correctly.

All of these involve the gas and combustion side of the boiler, which by law must only be worked on by a Gas Safe registered engineer. For a closer look at each cause, see our guide to why a boiler won't ignite.

Getting an Ignition Lockout Fixed

Tell the engineer the make, the model and the exact code, and whether the boiler tries to light before it stops. That is usually enough to narrow the fault to the spark, the flame sensor or the gas supply before arriving.

Ignition faults often start as occasional lockouts and get more frequent, usually on the coldest days when the boiler is working hardest. Getting it looked at after the second or third lockout is easier than waiting for it to fail completely. We diagnose ignition faults on all the main brands across London. You can book a diagnostic visit online.