Draft Inducer for Low Power Multistage Furnaces Utilizing an Electronically Commutated Motor System and an Associated Method of Use

A furnace assembly comprising a non-condensing furnace with a draft inducer, the draft inducer comprising a permanent magnet electrically commutated motor and a draft inducer blower fan, the motor comprising a stator, a rotor, a motor cooling fan, and a controller, the rotor being rotatable relative to the stator, the motor cooling fan being operatively coupled to the rotor such that rotation of the rotor causes rotation of the motor cooling fan, the motor cooling fan being configured and positioned to move air in a manner to cool at least some components of the motor, the draft inducer blower fan being operatively coupled to the rotor such that rotation of the rotor causes rotation of the draft inducer blower fan, the controller being configured to selectively operate the motor in first and second different rotational speed ranges of the rotor, the first rotational speed range constituting a first rotational speed and all rotational speeds within five percent of the first rotational speed, the second rotational speed range constituting a second rotational speed and all rotational speeds within five percent of the second rotational speed, the magnitude of the second rotational speed being less than about seventy percent of the magnitude of the first rotational speed, the controller being configured such that during normal operation of the furnace assembly, the motor is not operable at any rotational speeds between the first rotational speed range and the second rotational speed range except during transitionary periods in which the controller switches operation of the motor between the first rotational speed range and the second rotational speed range or the motor transitions between on and off states.

A method of operating a furnace assembly comprising:

• selectively operating a permanent magnet electrically commutated motor and a draft inducer blower fan for a draft inducer of a non-condensing furnace, the motor comprising a stator, a rotor, a motor cooling fan, and a controller, the rotor being rotatable relative to the stator and the motor cooling fan being operatively coupled to the rotor such that rotation of the rotor causes rotation of the motor cooling fan, the motor cooling fan being configured and positioned to move air in a manner to cool at least some components of the motor, the draft inducer blower fan being operatively coupled to the rotor such that rotation of the rotor causes rotation of the draft inducer blower fan, by utilizing the controller in first and second different torque ranges of the rotor, the first torque range constituting a first torque and all torques within five percent of the first torque, the second torque range constituting a second torque and all torques within five percent of the second torque, the magnitude of the second torque being less than about seventy percent of the magnitude of the first torque with the controller being configured such that during normal operation of the furnace assembly, wherein the motor is not operable at any torques between the first torque range and the second torque range except during transitionary periods in which the controller switches operation of the motor between the first torque range and the second torque range or the motor transitions between on and off states.