Gas water heater with increased thermal efficiency and safety

Abstract

A gas water heater having increased thermal efficiency comprises a water tank having a sealed combustion chamber thereunder. An atmospheric burner is located in the combustion chamber. A flue pipe extends from the sealed combustion chamber and through the water tank for heat exchange of hot atmospheric gas therein with water in the water tank. A heat exchanger is in communication with the combustion gases exiting the water tank to extract residual heat from the combustion gas in the flue pipe for mixture with ambient air to produce pre-heated combustion air. An air convection or draft inducing device directs the hot combustion air from the heat exchanger through a sealed conduit to direct the pre-heated combustion air to the combustion chamber.

1 . A gas water heater having increased thermal efficiency comprising a water tank having a sealed combustion chamber thereunder, an atmospheric burner in said sealed combustion chamber, a flue pipe extending from said sealed combustion chamber and through said water tank for heat exchange of hot combustion gas therein with water in said water tank, a heat exchanger in communication with said combustion gases exiting said water tank to extract residual heat from said combustion gas for mixture with ambient air to produce pre-heated combustion air, draft inducing means to pull said hot combustion gases from said combustion chamber through said flue pipe, and conduit means to direct said pre-heated combustion air to said combustion chamber. 
     
     
         2 . A gas water heater as claimed in claim I, wherein said conduit means is a sealed conduit, and air displacement means to displace said pre-heated combustion air into a top end of said sealed conduit and therethrough; said sealed conduit communicating, at a lower end thereof, with a combustion air inlet port of said sealed combustion chamber. 
     
     
         3 . A gas water heater as claimed in  claim 2 , wherein said displacement means is a fan. 
     
     
         4 . A gas water heater as claimed in  claim 1 , wherein said flue pipe is provided h baffles therein to slow said hot flue gases therein for heating said flue pipe in heat exchange with water in said water tank. 
     
     
         5 . A gas water heater as claimed in claim wherein said heat exchanger is an air-to-air heat exchanger. 
     
     
         6 . A gas water heater as claimed in  claim 1 , wherein there is further provided condensate evacuation means to evacuate condensate from said heat exchanger. 
     
     
         7 . A gas water heater as claimed in  claim 1 , wherein said flue pipe above said heat exchanger is a plastic vent pipe adequate to exhaust cooled combustion gases from an outlet of said heat exchanger. 
     
     
         8 . A gas water heater as claimed in  claim 1 , wherein said draft inducing means creates a combustion air flow path from a top end of said gas water heater. where combustion air is extracted and pre-heated, to be sealingly directed to said sealed combustion chamber and exhausted to atmosphere after heat extraction therefrom, said gas water heater having a gas detector exteriorly mounted at a lower end thereof to detect explosive gases to provide for an explosion proof gas water heater. 
     
     
         9 . A gas water heater as claimed in  claim 2 , wherein said conduit means is a combustion air conduit sealingly secured to an outer casing of said hot water heater, said water tank being a glass lined steel tank, thermal insulation between said steel tank and said outer casing, said heat exchanger being secured in a heat exchanger housing secured above a top end of said outer casing, said heat exchanger housing having air inlet means, and a fan in said heat exchanger housing constituting said air displacement means to draw in ambient air into said heat exchanger and direct it in a top end of said combustion air conduit where it is connected to said combustion chamber for admixture with combustible fuel fed to said atmospheric burner. 
     
     
         10 . A gas water heater as claimed in  claim 2 , wherein said top end of said sealed conduit is surrounded by a protective housing secured above said gas water heater water tank. 
     
     
       A gas water heater as claimed in  claim 10 , wherein said protective housing is a housing surrounding said heat exchanger.