| 摘要 |
A device for detecting the diversion of gas furnace or gas hot water heater exhaust into a dwelling due to chimney backdrafting detects a sustained rise in the temperature of the gases passing through the draft-diverter orifice. A significant rise in temperature indicates that the above condition has occurred. This temperature rise is recorded only after the condition has persisted for a sufficiently long period of time, thereby avoiding the recording of temporary backdrafting conditions which are not required to be recorded. The device consists of a high temperature resistant plastic strip or other material with similar conductivity and specific heat qualities with a temperature sensitive color-change material mounted on the surface of the plastic strip at one end of the strip. This strip is attached to the furnace or gas hot water heater in a preferred location with the color-change material facing away from the normal flow of backdrafting exhaust gases. Heat from the backdrafting flow causes the color-change material to change color once the heat in the gas flow has penetrated through the underlying plastic strip. An aerodynamic stagnation zone on the front face of the plastic strip during a backdraft condition prevents the color-change material from changing color prematurely.
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