Navien furnace is very noisy during operation, with rumbling or roaring sounds from the burner area

Safety: Turn off power and gas. Combustion adjustments must be done by a licensed gas technician.

• Inspect burner mounting: Remove the burner access cover and verify that the burner assembly is securely fastened and properly seated against the heat exchanger.
• Clean burner: Use a soft brush and vacuum to remove dust and debris from the burner surface. Do not enlarge or damage burner ports.
• Check venting: Ensure intake and exhaust are not partially blocked, which can affect combustion air supply.
• Professional combustion tuning: Have a Navien-trained technician measure combustion with an analyzer and adjust gas valve settings and air-fuel ratio as required. They should also verify inlet gas pressure and manifold pressure.