Boiler
F17
The F17 error code on a Ferroli boiler indicates a fault with the boiler’s ignition or flame detection — specifically, the boiler is failing to detect a stable flame after attempting to light. This fault will lock the boiler out and stop heating and hot water, so it needs attention promptly.
What does this error mean?
When your Ferroli boiler displays F17, it means the burner either failed to ignite or the flame sensor (ionisation probe) could not confirm a flame was present during the ignition sequence. The boiler’s control board runs a safety lockout to prevent unburned gas from accumulating. This is a protective measure, not a random glitch — something in the ignition or gas supply chain needs investigating.
Est. repair cost
£80–£180 for a Gas Safe engineer callout and repair (parts such as ionisation probe ~£20–£50, ignition electrode ~£15–£40, gas valve £80–£150)
🔍 Likely causes
🛠️ Step-by-step fix
Check your gas supply first: make sure other gas appliances (hob, gas fire) are working. If nothing gas-powered works, contact your gas supplier — there may be an outage or your meter may need attention.
Check the boiler’s gas isolation valve (the small lever on the gas pipe leading into the boiler) is fully open — it should be inline with the pipe, not across it.
Perform a boiler reset: locate the reset button on your Ferroli boiler (usually a flame symbol or labelled ‘Reset’), hold it for 3–5 seconds, and allow the boiler to attempt ignition again. Wait 10 minutes and check if the fault clears.
If the fault returns after one or two resets, do not keep resetting repeatedly — this is a safety lockout for a reason. Stop here and call a Gas Safe registered engineer.
Do not attempt to inspect, clean, or replace the ignition electrodes, ionisation probe, gas valve, or PCB yourself. These tasks require Gas Safe registration and are illegal for unqualified individuals to carry out on a gas appliance in the UK.
📞 When to call a professional
Call a Gas Safe registered engineer if the F17 fault returns after a single reset, or if you have no other explanation for it (e.g. a known gas outage). Tell the engineer: ‘My Ferroli boiler is showing an F17 lockout fault — it’s failing to detect a flame after ignition.’ This helps them arrive with the right parts, most likely an ionisation probe, ignition electrode, or gas valve.
⚖️ Repair or replace?
A Gas Safe engineer callout to diagnose and fix an F17 fault typically costs £80–£180 depending on the part required and your region. If your Ferroli boiler is under 8 years old, repair is almost always the right call. If it’s over 12 years old and this isn’t the first fault, replacing with a new A-rated combi boiler (typically £1,800–£2,800 installed) is worth serious consideration — older Ferroli models can become expensive to maintain.