F47 Boiler Fault Code: What It Means on Every Brand

The F47 fault code appears on 2 brands — Ferroli and Johnson & Starley — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Lockout — engineer likely 2 brands use this code Meaning differs by brand

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What F47 means	Severity	DIY?
FFerroli	The F47 code on a Ferroli boiler points to one of two underlying problems depending on which model range you own. Full guide →	Lockout — engineer likely	No
JSJohnson & Starley	F47 on a Johnson & Starley unit means the water pressure sensor is not connected — the control board can see no signal at all from the sensor that reports sealed-system pressure on the… Full guide →	Engineer may be needed	No

F47 brand by brand

Ferroli F47

The F47 code on a Ferroli boiler points to one of two underlying problems depending on which model range you own. On most Ferroli boilers it signals a water pressure sensor fault — the component that monitors system water pressure has either failed, developed a wiring fault, or is reading incorrectly due to abnormal system pressure. On certain other Ferroli models (including some Modena and i-Series variants), F47 falls within a group of codes that indicate a PCB parameter error, meaning the control board has a configuration or software setting that is out of range. Because F47 is an 'F' type blocking fault, the boiler locks out to protect itself but may clear automatically once the underlying condition is resolved — unlike 'A' codes, which always require a manual reset. Check your specific model's manual to confirm which interpretation applies to your boiler.

Causes, fixes & costs for Ferroli F47 → · All Ferroli codes

Johnson & Starley F47

F47 on a Johnson & Starley unit means the water pressure sensor is not connected — the control board can see no signal at all from the sensor that reports sealed-system pressure on the water-carrying models. This differs from F37/F40 (pressure genuinely low or high): here the board has lost the sensor itself. Without a pressure reading the controller cannot protect the water side against running dry or over-pressurised, so it shuts that side down. The causes are exactly what the name suggests: an unplugged or corroded connector, a broken lead between sensor and board, a failed sensor presenting as open-circuit, or — rarely — the board input.

Causes, fixes & costs for Johnson & Starley F47 → · All Johnson & Starley codes

Frequently asked questions

Is the F47 fault code the same on every boiler?

No. F47 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a F47 fault myself?

Not usually. On every brand listed, F47 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a F47 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.