ACV 537D3045 fan RG175-2000-3633-010205 P120 MK2

This is an ACV fan, catalogue number 375.145.062, manufacturer code 537D3045, listed under the fans and flue gas exhausters category. Such fans supply combustion air and, in room-sealed appliances, also expel the flue gases. In modulating premix boilers, the fan speed directly sets the firing rate: the burner control varies the fan speed, and the gas valve follows that airflow. The fan must be matched to the air pressure switch, which confirms that the required airflow is present before ignition is allowed. During the pre‑purge phase, the burner control starts the fan to clear the combustion chamber; only after the pressure switch reports correct airflow does the ignition sequence continue. When selecting a replacement fan of this type, the critical parameters are the required air flow and pressure at the burner’s operating point, the direction and orientation of the outlet, the impeller diameter, the voltage and control mode (mains, PWM, or 0‑10 V), and the flange pattern that matches the burner or boiler. Typical failure modes include worn bearings, imbalance from deposits on the impeller, a failed run capacitor, and speed feedback errors that the boiler detects as an airflow fault. When replacing, ensure the new fan’s flange and outlet orientation match the original to avoid air‑side mismatches; also confirm that the control mode is compatible with the existing burner control board.