System and method for burner ignition using sensorless constant mass flow draft inducers

A method of operating a motor for a draft inducer in a burner system, the motor coupled to a draft inducer fan configured to move air though an airflow path of the burner system, said method comprising:

• receiving, by a motor controller configured to supply current to the motor, a draft inducer control signal from a system controller;
• determine, by the motor controller, a first mass flow rate based on a target mass flow rate to be generated by the draft inducer, wherein the first mass flow rate is greater than the target mass flow rate;
• calculating, by the motor controller, a starting speed based on the first mass flow rate using a mass flow curve;
• supplying, in response to the draft inducer control signal, a first current, during a first period, to the motor to rotate the draft inducer fan at the calculated starting speed to produce a first mass flow through the burner system, the first mass flow having the first mass flow rate;
• and
• supplying a second current, during a second period starting at an expiration of the first period, to the motor to rotate the draft inducer fan to produce a second mass flow through the burner system, the second airflow having a target mass flow rate for normal operation of the burner.

A burner system comprising:

• a burner;
• a heat exchanger;
• a collection manifold;
• a motor coupled to and configured to turn a draft inducer fan configured to draw an airflow through an airflow path from said collection manifold and across said burner and through said heat exchanger;
• a vacuum switch configured to actuate when a mass flow rate through the airflow path is sufficient to produce a vacuum above a vacuum threshold, thereby enabling operation of said burner;
• and
• a motor controller coupled to said motor and configured to:
• receive a draft inducer control signal from a system controller;
• determine a first mass flow rate based on a target mass flow rate to be generated by the draft inducer, wherein the first mass flow rate is greater than the target mass flow rate;
• and
• calculate a starting speed based on the first mass flow rate using a mass flow curve;
• operate said motor, during a first period, to rotate said draft inducer fan at the calculated starting speed to produce a first mass flow through the airflow path, the first mass flow having the first mass flow rate;
• and
• operate said motor, during a second period starting at an expiration of the first period, to rotate said draft inducer fan to produce a second mass flow through the airflow path, the second mass flow having the target mass flow rate for normal operation of the burner.