De Dietrich 7665247 NRG118 – D21.4 fan

This is a De Dietrich fan, listed under catalogue article 375.145.058 and manufacturer code 7665247. The part is identified as NRG118 - D21.4 and belongs to the Fans and Flue Gas Exhausters category. Parts of this type supply combustion air and, in room-sealed appliances, also drive the flue gases out. In modulating premix boilers, the fan speed sets the firing rate; the burner control varies the speed and the gas valve follows accordingly. When selecting a replacement, a heating engineer must verify air flow and pressure requirements, the outlet orientation, impeller diameter, voltage, and control mode – mains, PWM, or 0-10 V signal. The flange pattern must match the existing mounting to ensure a proper seal. Typical failures on such fans include worn bearings, imbalance from deposits on the impeller, a failed capacitor, or speed feedback errors that the boiler may report as an airflow fault. Always confirm that the replacement part matches the original’s electrical and mechanical specifications before fitting.