A motor controller for a burner system includes an inverter that supplies current to a motor that rotates a draft inducer fan. A processor is coupled to the inverter and receives a signal from a system controller, and in response instructs the inverter to supply a first current, during a first period, to the motor to rotate the fan to produce a first mass flow through the burner system, the first mass flow having a first mass flow rate greater than a threshold to actuate a vacuum switch. The processor then instructs the inverter to supply a second current, during a second period starting at an expiration of the first period, to the motor to rotate the fan to produce a second mass flow through the burner system, the second mass flow having a target mass flow rate for normal operation of the burner.