Patent ID: 7431568

Claim:
A method for adjusting flow through a draft inducer to a pre-determined flow rate, the draft inducer having a voltage powered motor, wherein the draft inducer is coupled to a source to be ventilated and also coupled to an exhaust pipe of unknown length, the method comprising: providing a voltage to the motor; measuring the revolutions per time period of the motor; comparing the measured revolutions per time period with a revolutions per time period value associated with the voltage in a look-up table, wherein the look-up table contains a plurality of voltage values, each having an associated revolutions per time period value to achieve the predetermined flow rate; and if the measured revolutions per time period do not substantially match the associated revolutions per time period value in the look-up table, iteratively adjusting the voltage provided to the motor to another voltage value in the look-up table until the measured revolutions per time period substantially match the revolutions per time period value associated with the voltage provided.