Boiler is excessively noisy (rumbling, whistling, or vibrating) during operation

Safety first: Turn off power before tightening any hardware. Avoid contact with hot surfaces.

• Tighten mounting screws: Check the boiler casing, pump brackets, and vent supports for loose screws or brackets. Tighten as needed.
• Inspect inducer fan: Ensure the inducer is securely mounted and not contacting the housing.
• Check vent supports: Long vent runs should be properly supported to prevent resonance and vibration.
• Professional evaluation: Persistent rumbling or whistling may indicate combustion issues or scale and should be evaluated by a technician.