Method and apparatus for regulating flue draft

In a heating device including a combustion zone adapted to combust fuel, a flue to duct the combustion products from the combustion zone, and a draft hood having an inlet from the surrounding atmosphere positioned between the combustion zone and the terminus of the flue;

• the improvement comprising:
• means positioned at the draft hood in a location adjacent to but spaced from the flue to sense air flow from the surrounding atmosphere through the draft hood;
• valve means positioned in the flue downstream of the draft hood;
• means to drive the valve means to restrict and open flow through the flue;
• and
• control means responsive to the air flow means through the draft hood to activate the valve means drive means and position the valve means in a position to establish and maintain a predetermined substantially fixed flow of air through the draft hood to the flue as measured by the air flow sensing means.

A method of operating a heating device including a combustion zone, a flue to collect combustion products from the combustion zone and a vent to the air surrounding the heating device defined between the combustion zone and the end of the flue downstream of the combustion zone, the method comprising;

• measuring the flow of air through the vent into the flue during combustion by means of a flow rate sensor positioned at the vent;
• positioning valve means damper located in the flue downstream of the vent to restrict flow through the flue to a flow rate which provides a predetermined rate of flow of air through the vent and flue as a result of the flow rate measured;
• and
• maintaining the flow of air through the vent into the flue at the predetermined level by repositioning the valve means in response to a change in the measured flow rate at the vent, whereby loss of heated air surrounding the heating device through the vent is minimized and combustion products are retarded in their flow from the heating device to improve efficiency of the heating device.

A method of efficiently operating a heating device comprising;

• initiating combustion in a combustion zone,
• substantially fully opening a flue damper positioned in a flue receiving the combustion products from the combustion zone;
• measuring the flow rate of the air surrounding the heating device through a vent draft hood positioned between the combustion zone and flue damper and communicating between the surrounding air and combustion products by means of a flow rate sensor positioned at the vent draft hood;
• moving the flue damper to a more restrictive position until the measured rate of flow of air through the draft hood is at a predetermined level;
• opening the flue damper to a less restrictive position when the measured rate of flow of air through the draft hood falls below the predetermined level to restore the predetermined flow rate of air;
• terminating combustion in the combustion zone;
• and
• fully closing the flue damper after exhausting the combustion products from the combustion zone and flue.