Boiler
E11
The E11 error code on a Glow-worm boiler indicates a flame detection fault — the boiler is either failing to ignite or losing its flame shortly after firing up. This is a lockout fault, meaning your boiler has shut itself down as a safety measure and won’t restart without intervention.
What does this error mean?
When your Glow-worm boiler displays E11, the control board has detected that the burner flame either failed to establish during ignition or cut out unexpectedly during operation. The boiler’s flame sensor (ionisation probe) sends a signal confirming a stable flame is present — if that signal is absent or too weak, the boiler locks out to prevent unburned gas from accumulating. This is a built-in safety feature, not a fault you should attempt to bypass.
Est. repair cost
£150–£350 for a Gas Safe engineer repair (parts and labour); new boiler replacement £1,800–£2,800 installed
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Reset the boiler: Press and hold the reset button (usually marked with a flame or ‘R’ symbol) for 3–5 seconds. The boiler will attempt to re-ignite. If it fires up successfully and stays on, monitor it over the next 24 hours.
Step 2 — Check your gas supply: Turn on a gas hob burner. If you have no gas there either, the issue is with your supply — contact your gas supplier or National Gas Emergency Service (0800 111 999) immediately.
Step 3 — Check the gas isolation valve on the boiler pipework: It should be fully open, with the handle running parallel to the pipe. If it’s been knocked to a partially closed position, open it fully and retry the reset.
Step 4 — Check your neighbours: If nearby homes with the same supplier also have no gas, there may be a local supply interruption — no boiler repair needed, just wait for restoration.
Step 5 — Do NOT attempt any further DIY: If the boiler locks out again after resetting, stop here. The fault is internal — involving gas valves, electrodes, the ionisation probe, or the PCB — and must only be diagnosed and repaired by a Gas Safe registered engineer.
Step 6 — Call a Gas Safe engineer: Quote the E11 fault code when booking. Tell them the boiler model (found on the front panel or inside the casing door), how long the fault has been occurring, and whether it’s a new or recurring issue.
📞 When to call a professional
If the boiler locks out again within a short time of resetting, or fails to ignite at all, you must call a Gas Safe registered engineer — do not attempt to open the boiler casing or interfere with gas components yourself, as this is illegal without Gas Safe registration and extremely dangerous. Tell the engineer you have an E11 lockout fault, your boiler model and age, and whether you’ve noticed any unusual smells, sounds, or pilot light behaviour before the fault appeared.
⚖️ Repair or replace?
A Gas Safe engineer call-out and repair for an E11 fault typically costs £150–£350 depending on the faulty component — an ignition electrode or ionisation probe is at the cheaper end, while a gas valve or PCB replacement sits at the higher end. If your Glow-worm boiler is over 10–12 years old, weigh the repair cost against a new boiler: a replacement A-rated combi boiler installed typically costs £1,800–£2,800 in the UK. For boilers under 8 years old in otherwise good condition, repair is almost always the right call.