Alternate intake apparatus

A normally closed alternate intake apparatus that opens to provide combustible air from inside a heated space for 90% Annual Fuel Utilization Efficiency (AFUE) gas or oil burning furnaces or water heaters when outside combustible air conduit is blocked by snow or ice where said outside combustible air conduit enters said gas or oil burning device in a horizontal or a vertical attitude comprised of:

• a cylindrical tubular base with an inside diameter, an outside diameter, a bottom face, a top face, a front side, a left side, an inside wall, an outside wall, an axis and a length;
• pivot retaining means on said right and left sides of said inside wall of said cylindrical tubular base at each end of a chord that is approximately ⅙ of said inside diameter radially outward from said cylindrical tubular base axis;
• an upper rear stop that has a front surface that extends radially inward from said inside wall, and angled towards the bottom face radially above and axially closer to said bottom face than said pivot retaining means;
• a lower front stop surface that has a rear surface that extends radially inward and angled towards the top face from said inside wall radially below and axially further away from said bottom face than said pivot retaining means wherein the said upper stop is longer than the said lower stop;
• a pivot plate with a top, a bottom, a right side, a left side, a front side, a back side, a top section and a bottom section with pivot pins on said right and left sides that fit into said pivot retaining means on said inside wall of said cylindrical tubular base and are located at points approximately ⅔ the distance between said top and bottom from said bottom, where said pivot pins have a diameter and a length and where said top section is thinner than said bottom section and the ratio of masses between said top section and said bottom section is selected as to provide sufficient pressure by said pivot plate top upward against said upper front stop and said pivot plate bottom downward against said lower rear stop as to keep said pivot plate closed during normal operation, when said alternate intake apparatus is mounted either over the depending end of a plastic T fitting spliced into a horizontal section of said outside air inlet conduit with said top face oriented upward, the depending end of a downward angled T fitting spliced into a vertical section of said outside air inlet conduit with said top face oriented upward or the depending end of a downward facing elbow fitting attached to the horizontal section of a T fitting spliced into a vertical section of said outside air inlet conduit with said top face oriented upward;
• where
• said pivot plate's exterior dimensions clear said inside diameter of said cylindrical tubular base and said pivot retaining means, but are larger than the inside diameters of said upper rear stop and said lower front stop;
• said pivot plates said front side has the word UP and an arrow pointing upward at said top;
• said bottom section of said pivot plate beneath said pivot retaining means is thicker than the section above said pivot retaining means a sufficient amount as to provide a downward force of sufficient magnitude as to hold said alternate air intake apparatus closed during normal operation but small enough as to allow the decreased head pressure in said outside air conduit to pivot said pivot plate away from said upper and lower stops allowing a flow of internal ambient air into said burning chambers and allowing said 90% AFUE gas or oil burning furnaces or water heaters to continue operation even after input air line is blocked with snow or ice.