Water heater vibrates excessively or rattles when the burner is running.

Safety: Isolate power and gas. Allow the appliance to cool.

• Check mounting: Ensure the appliance is securely fixed to the wall and that all mounting screws are tight.
• Inspect internal components: Tighten screws on the burner, fan, and combustion chamber panels.
• Check flue: Verify that flue sections are properly supported and clipped, with no loose joints.
• Test operation: Run the heater and observe for remaining vibration. If internal components are damaged or misaligned, have a Vaillant engineer assess and replace as needed.