Furnace makes loud banging or booming noise at startup.

Safety First: Turn off gas and power. Delayed ignition can be dangerous; do not ignore booming noises.

• Visual burner inspection: Remove burner access panel and inspect burners for rust, debris, or misalignment. Do not modify burner geometry.
• Clean burners: If you are experienced, remove burners and clean with a wire brush and compressed air. Ensure all ports are clear and reinstall in the original order.
• Check ignitor position: Verify the hot surface ignitor is properly positioned in the gas stream per Thermo Pride specifications (usually just ahead of the first burner).
• Call a professional: A technician should verify gas pressure and combustion to prevent further delayed ignition events.