Importance

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Abstract

A control circuit for a forced-air heating system comprises a silicon diode that is positionable in thermally-conductive relationship with the interior space of a furnace plenum. A current source supplies current to the silicon diode, and the potential drop across the silicon diode is sensed. The operating speed of the blower is controlled in response to the voltage drop across the silicon diode in a manner such that when the temperature in the plenum is below a first level, the blower is not driven; when the temperature reaches the first level, the blower is driven at a first speed; and when the temperature reaches a second level, which is higher than the first level, the blower is driven at a second speed, which is higher than the first speed.

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First Claim