Boiler indicates flow switch or flow sensor error, burner will not start

Safety first: Turn off power and allow the system to cool before opening any valves or filters.

• Check system pressure: Ensure pressure is within the normal range (around 1.0–1.5 bar). Top up if necessary.
• Bleed air: Bleed radiators and any automatic air vents to remove trapped air that can prevent flow.
• Clean system filter: If a magnetic or Y-strainer filter is installed near the boiler, isolate it, place a tray underneath, and carefully remove the cap to clean out sludge. Re-seal and check for leaks.
• Check pump operation: Confirm the Nibe circulation pump is running when there is a heat demand. If not, it may require replacement.
• Technician service: A professional can test and replace the Nibe flow switch or flow sensor if it is sticking or electrically faulty.