Furnace combustion gas sensing and control systems and methods

An HVAC system comprising:

• a furnace including:
• a burner positioned within a furnace housing and configured to generate heat through fuel combustion;
• a flue vent conduit positioned within the furnace housing;
• and
• a flue gas sampling circuit positioned to receive a sample of a flue gas from the flue vent conduit, the flue gas sampling circuit including a gas sensor to analyze the sample of the flue gas and a heat exchanger positioned upstream of the gas sensor to condition the sample of the flue gas as it flows to the gas sensor.

A method comprising:

• using an inducer blower to induce flow of combustion gas through a heat exchanger within a furnace such that the combustion gas flows into an inlet side of the inducer blower and is expelled through an outlet side of the inducer blower into an exhaust conduit;
• using the inducer blower to also induce flow of a portion of the combustion gas out from the exhaust conduit into a sampling circuit having a carbon monoxide sensor;
• and
• analyzing the portion of the combustion gas using the carbon monoxide sensor.