Furnace makes loud banging or knocking noises when starting or stopping

Safety first: Allow system to cool before touching pipework.

Steps:

• Bleed air: Bleed radiators and high points to remove trapped air that can cause banging.
• Adjust pump speed: If the Intergas pump has multiple speeds, try reducing the speed to minimize hydraulic shock.
• Secure pipework: Check accessible pipes for loose clips or contact with building structure. Add or tighten clips to reduce movement.

If noises persist, a heating engineer may need to review system design and expansion arrangements.