Navien furnace makes loud banging or knocking noises in the piping when the burner fires or shuts off

Safety: Use caution around hot pipes. Turn off power before adjusting pump settings.

• Secure piping: Inspect accessible hydronic piping and add or tighten pipe clamps and supports to prevent movement when the system heats and cools.
• Bleed air: Air in the system can cause banging. Use air vents and bleeders to purge air from high points and radiators.
• Adjust pump speed: If the system circulator has multiple speeds or is variable-speed, reduce the speed slightly to lower water velocity and reduce noise.
• Check expansion tank: Verify that the hydronic expansion tank is properly charged (typically 12 psi cold) and not waterlogged. Replace if the tank is full of water or the air charge is lost.