Draft control arrangement for combustion apparatus

摘要

A draft control arrangement having bimetallic damper elements mounted in a draft hood and adapted to change shape in response to temperature change to open and close the flow passage for vent gases from a combustion apparatus. The damper elements are positioned in the hood relatively close to the source of hot flue gases to provide faster opening and less tendency for vent gas spillage. When open the damper elements cooperate with stationary walls of the draft hood so that the resulting streamlined passage prevents minimum flow resistance. In certain embodiments the damper elements are arranged to undergo a spreading action during opening movement to achieve a disproportionately large passage for the vent gases during the initial phase of opening. In another embodiment a damper unit is mounted separate from the draft hood and provides the same operating results as the other embodiments.