Furnace makes loud banging or knocking noises when starting or stopping (kettling)

Safety first: Isolate power and allow the system to cool before touching pipework.

• 1. Check system pressure and flow: Ensure correct pressure and that all isolation valves are open. Verify pump is running at appropriate speed.
• 2. Bleed air: Remove air from radiators and boiler air vent to improve circulation.
• 3. System cleaning: Consider a chemical flush of the heating system using a suitable cleaner, followed by inhibitor. This should be done by a heating professional.
• 4. Descale heat exchanger: On heavily scaled systems, the primary heat exchanger may need to be removed and descaled or replaced with an original Junkers exchanger.