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Control of staged heating and cooling apparatus by a four-wire thermostat

  • US 5,022,460 A
  • Filed: 02/09/1990
  • Issued: 06/11/1991
  • Est. Priority Date: 02/09/1990
  • Status: Expired due to Term
First Claim
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1. In a system for controlling heating and cooling apparatus wherein the heating and cooling apparatus include a circulator fan and wherein at least one of the heating and cooling apparatus is two-stage,a control module in said heating and cooling apparatus;

  • a thermostat;

    fan control means in said thermostat for selectively effecting a demand or no demand for continuous operation of said circulator fan; and

    means for directly connecting said thermostat to said control module consisting of four wires,a first one of said wires being effective to provide a common power connection between said thermostat and said control module,a second one of said wires being effective to provide an enabling signal to said control module to control first-stage operation of said heating apparatus,a third one of said wires being effective to provide an enabling signal to said control module to control first-stage operation of said cooling apparatus,a fourth one of said wires being effective to provide, in response to said fan control means, an enabling signal to said control module to control operation of said circulator fan, and also to provide an enabling signal to said control module to control second-stage operation of said two-stage apparatus.

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