Boiler makes loud banging or knocking noises when starting or stopping

Safety first: No immediate danger in most cases, but loud bangs can indicate stress on components. Do not ignore persistent noise.

• Bleed radiators: Remove trapped air from all radiators and high points in the system.
• Check pump speed: If the Nibe pump has adjustable speeds, ensure it is set according to the installation manual for your system size.
• Inspect pipe clips: Secure any loose heating pipes with appropriate clips to reduce water hammer.
• Water treatment: In hard water areas, ask a technician to check for kettling and, if necessary, chemically clean or replace the Nibe primary heat exchanger and add inhibitor.