Ferroli F10 Fault Code: Causes, Fixes & Repair Costs
What does the Ferroli F10 fault code mean?
The F10 code on a Ferroli boiler indicates a fault with the central heating flow temperature sensor (also referred to as the delivery or supply sensor). This NTC thermistor monitors the temperature of water leaving the heat exchanger on its way around your heating circuit. When the boiler's control board detects that the sensor's signal is outside acceptable parameters — whether due to an open circuit, a short circuit, or physical sensor damage — it throws F10 and shuts the boiler down entirely. Unlike the related F11 code (which affects the domestic hot water sensor and allows heating to continue), F10 causes a full stop: neither heating nor hot water will work until the fault is resolved. Because F10 is an 'F' category code on Ferroli boilers, it is classified as a blocking fault that may clear on its own if the underlying condition resolves, but in practice a persistent F10 almost always requires a physical repair.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Faulty or degraded NTC flow temperature sensor Common
The NTC thermistor itself has failed internally — its resistance values no longer correspond correctly to the actual water temperature. This is the single most common cause of F10. Sensors degrade over time through repeated heating and cooling cycles, and older Ferroli units are particularly susceptible. An engineer can confirm this quickly with a resistance (ohmmeter) test.
- Loose, corroded, or damaged sensor wiring Common
The wiring connecting the flow sensor to the PCB can work loose at the connector, corrode at the terminals, or develop a chafe point causing an intermittent open or short circuit. This gives the control board an implausible or absent signal and triggers F10. The fault may appear and disappear as the boiler heats and cools, making wiring faults particularly frustrating to live with.
- Short circuit in the sensor circuit Sometimes
A dead short in the sensor wiring — often caused by pinched cables, water ingress near the sensor, or previous poor repair work — sends a near-zero resistance reading to the PCB. The board interprets this as an impossibly high temperature and locks the boiler out with F10.
- PCB (control board) failure Rare
If the sensor and all associated wiring test as healthy, the fault can lie with the PCB input that reads the sensor signal. PCB failures are relatively uncommon as the root cause of F10 but become more likely on boilers over eight to ten years old or those that have suffered a power surge.
How to fix it
- Reset the boiler once DIY safe
Locate the reset button on your Ferroli boiler — it is usually marked with an 'R' or a flame symbol. Press and hold it for around five to ten seconds until the boiler attempts to restart. A single reset is a reasonable first step; if the F10 code clears and the boiler runs normally, monitor it closely over the next hour or so. Do not reset more than two or three times in total: repeated resets when a sensor fault is present put unnecessary strain on the heat exchanger and fan and will not address the underlying problem.
- Check for any obvious external factors DIY safe
While not a fix in itself, it is worth confirming your gas supply is on (check other gas appliances in the home), that the boiler has not tripped its own isolation switch, and that your system pressure is between 1 and 1.5 bar on the pressure gauge. A very low pressure can occasionally trigger secondary faults. If pressure is below 1 bar, top up via the filling loop. None of these checks will fix a sensor fault, but they rule out simpler issues before you pay for an engineer visit.
- If the fault persists, arrange a Gas Safe registered engineer visit Gas Safe engineer
A persistent or returning F10 requires professional diagnosis. The engineer will use an ohmmeter to test the NTC sensor's resistance at a known water temperature, inspect all wiring connectors and cable runs between the sensor and the PCB, and confirm whether the sensor, wiring, or PCB is at fault. Do not attempt to open the boiler casing, disconnect wiring, or handle any internal components yourself — this is both a safety risk and likely to invalidate any remaining warranty.
- Sensor or wiring replacement by the engineer Gas Safe engineer
If the sensor is confirmed defective, the engineer will drain down the relevant section of the boiler, remove the old NTC thermistor, fit a like-for-like replacement, and retest. If wiring is the culprit, connectors will be cleaned or replaced and the loom re-routed away from any heat source or chafe point. After the repair the boiler will be fired up and the flow temperature readings verified against the sensor output to confirm the fix.
- PCB inspection or replacement if sensor and wiring are healthy Gas Safe engineer
Should the sensor and wiring both test as serviceable, the engineer will investigate the PCB. A faulty input channel on the control board will need the board to be replaced — a more involved and costlier repair. The engineer will advise whether this is economical given the age and condition of your Ferroli boiler.
Parts you may need
- Ferroli NTC flow temperature sensor (thermistor) · from £25
- Sensor wiring loom / connector harness · from £20
- Ferroli PCB (control board) · from £120
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £100–£280, depending on the underlying cause.
Frequently asked questions
Will my Ferroli boiler produce hot water or heating while F10 is showing?
No. Unlike the F11 code — which affects the domestic hot water sensor and typically allows the boiler to keep running in heating mode — an F10 fault causes a complete shutdown. You will lose both central heating and hot water until the flow temperature sensor fault is resolved.
Can I just keep resetting the boiler to get heat while I wait for an engineer?
You should avoid this. One or two resets to confirm the fault is persistent is fine, but repeatedly forcing the boiler to fire up when the flow sensor is not working correctly means the control board cannot properly regulate the heat exchanger temperature. This risks overheating, which can cause expensive damage to the heat exchanger — a repair that can cost £400 to £700 or more on top of the original sensor problem.
How much does it cost to fix an F10 fault on a Ferroli boiler in the UK?
For most homeowners, the repair is a straightforward NTC sensor replacement and costs roughly £100 to £180 including parts and labour. If the wiring loom needs attention as well, expect £150 to £250. A PCB replacement — needed only when the sensor and wiring are both healthy — typically adds up to £280 or so including fitting. Always get a fixed-price quote before work begins. If your Ferroli is over ten years old and facing a PCB repair, it is worth getting a replacement boiler quote for comparison.
What is the difference between Ferroli F10 and F11?
Both codes relate to temperature sensor faults, but they affect different sensors. F10 is a fault on the central heating flow (delivery) sensor — the one monitoring water temperature as it leaves the heat exchanger into the heating circuit — and it stops the boiler completely. F11 is a fault on the domestic hot water (DHW) sensor, and Ferroli boilers will generally continue to operate in heating mode when F11 is present, even though hot water is unavailable. If your display shows F11 and you still have radiator heat but no hot water, that points to F11 rather than F10.
Is Ferroli F10 a lockout or a blocking fault?
F10 is what Ferroli classifies as a blocking fault (denoted by the 'F' prefix). This means, in theory, the boiler could resume normal operation automatically if the condition causing the fault clears — for example, if a connector had briefly lost contact. In practice, however, if F10 keeps returning after a reset, there is a genuine hardware problem with the sensor or wiring that will not go away on its own and needs a Gas Safe engineer to diagnose and repair.