Boiler makes loud banging or knocking noises when firing or shortly after

Safety first: Turn off power and allow the boiler to cool before touching piping.

• Check system pressure: Verify pressure is within the recommended range. Low pressure can cause localized boiling.
• Bleed air: Use automatic air vents and manual bleed valves to remove air from the boiler and near-boiler piping.
• Verify pump operation: Ensure the primary pump is running and sized correctly. A failed or undersized pump can cause kettling.
• Descale heat exchanger (professional): If the system uses hard water or has not been treated, a professional should chemically descale the Lochinvar heat exchanger using approved procedures.

Professional help: Persistent kettling can damage the heat exchanger; have a technician address it promptly.