Boiler
F11
The F11 error code on an Alpha boiler indicates a flame failure — the boiler is attempting to ignite but cannot establish or maintain a stable flame. This fault will lock out your boiler and leave you without heating or hot water, so it needs addressing promptly.
What does this error mean?
When your Alpha boiler displays F11, the control board has detected that no flame was confirmed during the ignition sequence, or an existing flame cut out unexpectedly. The boiler performs several ignition attempts, and if none succeed, it locks out as a safety precaution to prevent unburned gas from accumulating. This is a protective shutdown — the boiler is working as intended, but something upstream is preventing reliable combustion.
Est. repair cost
£80–£200 for callout + labour; parts (flame sensor, electrodes) £20–£60; gas valve or PCB replacement £250–£400 all-in
🔍 Likely causes
🛠️ Step-by-step fix
Perform a boiler reset: press and hold the reset button (usually marked with a flame symbol) for 3–5 seconds, then wait 2–3 minutes to see if the boiler fires up successfully. This clears a one-off lockout.
Check your gas supply: confirm other gas appliances in your home (hob, gas fire) are working normally. If they are not, contact your gas supplier immediately — do not attempt any boiler work.
Check the gas isolation valve on the pipe leading to the boiler: it should be fully open (handle inline with the pipe). If it is partially closed, open it fully and attempt a reset.
In freezing weather, check the white plastic condensate pipe that exits the boiler (usually runs to an outside drain or internal waste). If frozen solid, thaw it gently with warm (not boiling) water and attempt a reset — see your Alpha manual for the exact pipe location.
If the boiler locks out again after one or two resets, stop resetting it. Repeated failed ignition attempts are a sign of a component fault — this is where DIY ends. Call a Gas Safe registered engineer.
Do NOT attempt to access the gas valve, ignition electrodes, or flame sensor yourself. Working on internal gas boiler components without Gas Safe registration is illegal and dangerous.
📞 When to call a professional
If the boiler locks out again after a reset, or if your gas supply is confirmed normal but the F11 persists, call a Gas Safe registered engineer immediately. Tell them your boiler model (e.g. Alpha E-Tec, Evoke, or CD range), that you have an F11 flame failure lockout, and how many times it has locked out — this helps them diagnose faster. Do not keep resetting the boiler repeatedly, as this can flood the heat exchanger with unburned gas.
⚖️ Repair or replace?
A Gas Safe engineer callout to diagnose and fix an F11 fault typically costs £80–£200 depending on the part required — a flame sensor or electrode replacement sits at the lower end, while a gas valve or PCB replacement pushes toward £250–£400 including parts and labour. If your Alpha boiler is over 10 years old and this is not its first significant fault, replacing it with a new A-rated combi boiler (typically £1,500–£2,500 fully installed) is likely better value than continuing to repair aging components. For boilers under 8 years old in otherwise good condition, repair is almost always the right call.