Common problems guide

The most common Ferroli F24b problems

The faults most likely to send a Ferroli F24b into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
4 documented codes
4 most common
3 DIY-safe checks
1 engineer needed

The 4 most common faults

01
LED 5 (Flashing light) High DIY-safe

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

What to try first

Locate the external filling loop, which is a silver braided flexible hose connected to two valves under the boiler.Open both taps on the filling loop slowly to let water into the system until the pressure gauge on the front reads between 1 and 1.5 bar.Close both taps tightly and check for leaks, then reset the boiler.

Est. cost
£80-120
Parts
Filling loop, Pressure relief valve, Pressure sensor
Full guide for LED 5 (Flashing light)
02
5 (Flashing Light) High DIY-safe

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

What to try first

Locate the filling loop, which is usually a silver braided hose with one or two valves underneath your boiler.Open the valve(s) slowly and watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically between 1.0 and 1.5 bar).Close the valve(s) firmly and ensure the boiler resets itself or switch it off and back on at the power source.

Est. cost
£60-120
Parts
Filling loop, Pressure relief valve, Pressure sensor
Full guide for 5 (Flashing Light)
03
Boiler lock out High Engineer

Your boiler has stopped working for safety reasons and needs a manual reset or a check of your gas and water drainage systems.

Est. cost
£120-250
Parts
Ignition electrode, Condensate trap, Gas valve
Full guide for Boiler lock out
04
Low water pressure Medium DIY-safe

Your boiler has stopped working because the amount of water inside your heating system has dropped below the required level.

What to try first

Locate the filling loop, which is usually a flexible silver hose connected to two valves beneath the boiler.Open the valves slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1 bar and 1.5 bar.Close both valves tightly and ensure there is no dripping from the connection points.

Est. cost
£0-£100
Parts
Filling loop, Pressure relief valve, Pressure gauge
Full guide for Low water pressure
Parts most often replaced

on the Ferroli F24b

Filling loopPressure relief valvePressure sensorIgnition electrodeCondensate trapGas valve

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Ferroli shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 4-code list for the Ferroli F24b

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →