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Variable speed inducer motor control method

  • US 5,791,332 A
  • Filed: 02/16/1996
  • Issued: 08/11/1998
  • Est. Priority Date: 02/16/1996
  • Status: Expired due to Term
First Claim
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1. In an induced draft furnace having a heat exchanger, an ignition circuit, and an integrated control inducer motor having a fluctuating motor speed, an improved method of controlling the air combustion level in said furnace, said method comprising the steps of:

  • establishing a lookup table including (a) a combustion operating lookup plot wherein motor speed is correlated with torque values required to achieve desired combustion operation motor speeds at various flow restrictions and (b) a threshold combustion operating plot correlating current motor speed with minimum torque required for ignition;

    determining whether a call for heat has been made; and

    upon determining that a call for heat has been made,controlling said motor by increasing the speed of said inducer motor until said motor exceeds a speed suitable for a combustion operating state and activating said ignition circuit when the current motor tongue exceeds said minimum torque from said lookup table,reading motor speed values from said motor, andmaintaining a constant flow of air through said furnace by controlling the torque applied to said integrated control inducer motor in accordance with torque values from said lookup table correlated with said motor speed.

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