Damper with override control

Claim 1

A control circuit and damper combination for controlling the flow of fluid through a building conduit, said combination comprising: a damper including a frame mounted barrier normally in a position blocking fluid flow through the damper and movable to an open position permitting fluid flow through the damper; electrically operated means coupled with the barrier and adapted to be coupled with a source of power for moving the barrier to said open position; first internal thermal responsive switch means in relatively close proximity to the damper, said first switch means being operably coupled with said electrically operated means to permit the latter to remain energized to hold the barrier in said open position when the ambient temperature at said first switch means is below a first predetermined level and to deenergize said electrically operated means to permit the barrier to move to said flow blocking position when the ambient temperature at said first switch means is elevated to or above said first predetermined level; overriding control circuitry operably coupled with said electrically operated means and adapted to be coupled with said power source to permit optional energizing of said electrically operated means to open the barrier irrespective of operation of said first switch means to deenergize said electrically operated means; and second thermal responsive switch means in relatively close proximity to the damper, said second switch means being operably coupled with said overriding control circuitry to permit the operation of the control circuitry when the ambient temperature at said second switch means is below a second predetermined level higher than said first predetermined level, and to prevent the operation of said overriding control circuitry when the ambient temperature is at or above said second predetermined level.