Furnace Startup Noise & Duct Assessment Equipment: Furnace Installed ~6 Months Ago Service Performed: • Assessed complaint of loud banging/snapping noise on furnace start-up • Checked static pressure and blower speed – both set correctly for the unit • Observed that the noise originates from the ductwork above the furnace, not from ignition, gas, or components within the furnace itself • Tested ignition sequence and gas safety controls – no safety concerns found • Installed piece of strap to support return vent; this has likely reduced or stopped the noise during pressure fluctuations Cause of Noise: • Furnace blower creates rapid pressure variations at start-up • This can cause flexible or thin sheet metal duct sections to “snap” as pressure equalizes • This is a duct dynamics issue, not a furnace safety issue with gas or ignition Recommendations: • Replace air filter regularly – at least every two months, as a cleaner filter helps maintain stable airflow and reduces