Safety device for abnormal draught detection for gas fired boiler with natural draught flue

摘要

The boiler comprising a damper mounted above the heating body, so as to form an additional ambient air inlet between the heating body and the damper, via which the boiler is connected to the smoke pipe, the safety device comprises a temperature detector positioned outside the boiler and facing said additional ambient air inlet, the detector thus being swept, when the boiler operates, by the ambient air which is sucked in through the damper into the smoke pipe in order to be mixed with the discharged combustion gases, this detector being designed to cut, by any suitable means such as a deformable element connected to an electric contact, the gas supply to the burner of the boiler, when the temperature detected exceeds a predetermined limit THETA 1 corresponding to an abnormal draught and to reestablish this supply only at the end of a predetermined time t when the temperature in the environment of the detector has fallen to a value THETA 2 corresponding to normal operation of the boiler and the combustion gases which may have escaped into the ambient environment have had the time to be reabsorbed into the smoke pipe in order to be discharged.