Boiler
F14
The F14 error code on a Viessmann boiler indicates a fault with the burner control unit or ignition circuit — it’s a relatively serious fault that will typically lock out your boiler and prevent it from firing. Don’t ignore it: a lockout means no heating or hot water until the underlying issue is resolved.
What does this error mean?
The F14 code signals that the boiler’s control board has detected a problem with the burner management or ignition sequence — the process that lights the gas and confirms a stable flame. In plain terms, the boiler attempted to ignite, failed to establish or detect a proper flame, and has shut itself down as a safety measure. This is a gas-side fault, which means all diagnosis and repair beyond a basic reset must be carried out by a Gas Safe registered engineer.
Est. repair cost
£150–£350 for most repairs; up to £400–£500 if PCB or burner control unit replacement is needed
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Check your gas supply: Before anything else, confirm other gas appliances (hob, gas fire) are working normally. If they’re not, contact your gas supplier — this is a supply issue, not a boiler fault.
Step 2 — Check the boiler display: Note the exact fault code shown. Some Viessmann models display F14 alongside a secondary code that pinpoints the fault more precisely — photograph the display before resetting.
Step 3 — Perform a manual reset: Press and hold the reset button (usually marked with a flame/reset icon) for 3–5 seconds as described in your boiler’s manual. Allow the boiler to attempt a full restart cycle.
Step 4 — Wait and observe: If the boiler lights and runs for 10–15 minutes without the F14 returning, monitor it over the next 24 hours. A one-off lockout can occasionally result from a temporary gas pressure dip.
Step 5 — If F14 returns after reset, stop here: Do not attempt to open the boiler casing, adjust gas components, or repeat the reset more than twice. Repeated lockouts indicate a persistent fault requiring professional diagnosis.
Step 6 — Call a Gas Safe registered engineer: This is a gas-side fault — further investigation involves gas components and ignition systems that are legally restricted to qualified engineers in the UK.
📞 When to call a professional
Call a Gas Safe registered engineer if the F14 error returns after one or two resets, or if the boiler fails to light at all. Tell the engineer the exact error code (F14), your boiler model (found on the data plate inside the front panel), and roughly how many times the lockout has occurred. Do not attempt to inspect or adjust the burner, electrodes, or gas valve yourself — this is illegal without Gas Safe registration and dangerous.
⚖️ Repair or replace?
A Gas Safe engineer callout to diagnose and repair an F14 fault typically costs £150–£350 depending on the cause — replacing an ignition electrode or flame sensor sits at the lower end, while a PCB or burner control unit replacement can reach £300–£500 including parts and labour. If your Viessmann boiler is over 12–15 years old and facing a PCB or BCU replacement, the cost may approach 40–60% of a new boiler’s price (£2,000–£3,500 installed for a modern Viessmann Vitodens); in that case, replacement is the smarter long-term investment. Boilers under 10 years old in otherwise good condition are well worth repairing.