Ferroli F 30 B Fault codes & diagnostics

19 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 30 kW Discontinued

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
11 High 8 Low
Just want the most common Ferroli F 30 B faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 19 documented codes

Tap any card for details

LED / flash-pattern codes
4 (Flashing Light)

Your boiler is currently in standby mode and is simply waiting for a signal from your thermostat or hot water tap to start heating.

Low DIY-safe

What to check first

  1. Turn up your room thermostat to request heat
  2. Check your programmer or timer is set to ON
  3. Verify that the hot water tap is turned fully on if requesting hot water
Full explanation for 4 (Flashing Light)
5 (Flashing Light)

Your boiler has stopped working because the water pressure inside your heating system has dropped too low.

High DIY-safe £0-£80

What to check first

  1. Locate the filling loop (a flexible metal hose) underneath the boiler.
  2. Open the small valve or tap on the filling loop to allow water to enter the system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (usually 1.0 to 1.5 bar).
  4. Close the valve tightly and check that the fault light has cleared.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure gauge

Related codes

Full explanation for 5 (Flashing Light)
LED5 Flashing

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £80-120

What to check first

  1. Locate the external filling loop, which is a silver braided flexible hose connected between two pipes under your boiler.
  2. Open the small black or metal valve(s) on the loop to allow water to enter the system while watching the pressure gauge on the front of the boiler.
  3. When the needle reaches 1.5 bar on the gauge, close the valve(s) tightly to stop the flow of water.

Parts commonly replaced

  • Filling loop
  • Pressure gauge
  • Pressure relief valve

Related codes

Full explanation for LED5 Flashing
Digital codes
F1

Your boiler has detected that it cannot start the flame needed to heat your water or home.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition transformer
  • Printed circuit board

Related codes

Full explanation for F1
F2

Your boiler has stopped because it cannot maintain a stable flame, meaning your heating and hot water have turned off for safety.

High Engineer only £120-250

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • PCB

Related codes

Full explanation for F2
F3

Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage or dangerous overheating.

High Engineer only £120-250

Parts commonly replaced

  • High limit thermostat
  • Central heating pump
  • Primary heat exchanger
  • System filter

Related codes

Full explanation for F3
F5

Your boiler is struggling to clear exhaust gases safely, so it has stopped working to prevent any potential buildup of fumes.

High Engineer only £120-250

Parts commonly replaced

  • Air pressure switch
  • Venturi tube
  • Flue fan

Related codes

Full explanation for F5
F7

Your boiler is struggling to detect the temperature of the water used for your taps and shower because a sensor has stopped communicating correctly.

High Engineer only £120-200

Parts commonly replaced

  • DHW NTC sensor
  • Wiring harness

Related codes

Full explanation for F7
F10

Your boiler has lost the ability to measure the temperature of the water inside your heating system, so it has shut down as a precaution.

High Engineer only £120-200

Parts commonly replaced

  • Central heating NTC sensor
  • Wiring harness

Related codes

Full explanation for F10
F37

Your boiler has stopped working because the water pressure inside the system is currently too low to operate safely.

High DIY-safe £80-£150

What to check first

  1. Locate the external filling loop, which is usually a flexible silver hose connected to two valves beneath the boiler.
  2. Open the valves slowly to allow cold mains water to enter the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Fully close the valves and ensure they are tight to prevent over-pressurisation.

Parts commonly replaced

  • Pressure relief valve
  • Pressure sensor
  • Expansion vessel
Full explanation for F37
LED2

Your boiler has detected a serious problem and has safely shut itself down to prevent damage or safety hazards.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Flame detection sensor
  • Printed Circuit Board
Full explanation for LED2
Red lockout light

Your boiler has detected an issue and stopped working as a safety precaution, likely because the fuel supply is interrupted or the internal pipe for water drainage is blocked.

High Engineer only £100-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap
Full explanation for Red lockout light