Water heater having a down fired combustion assembly

A water heater configured to operate with a non-positive vent static pressure and with a vent gas temperature that avoids or reduces excessive condensate production in an exhaust vent connected to receive combustion gases from the water heater, the water heater comprising:

• a water storage tank;
• a first pass flue tube extending from a top of the water storage tank to a bottom of the water storage tank;
• a down-fired burner assembly positioned to direct combustion gases into the first pass flue tube;
• at least one second pass flue tube extending from the bottom of the water storage tank to the top of the water storage tank;
• an expansion chamber positioned below the bottom of the water storage tank, the expansion chamber being coupled to receive the combustion gases from the first pass flue tube and to deliver the combustion gases to the at least one second pass flue tube;
• a combustion gas outlet positioned at or above the top of the water storage tank, the combustion gas outlet being coupled to receive the combustion gases from the at least one second pass flue tube and to deliver the combustion gases toward the vent with the non-positive vent static pressure;
• and
• a draft hood coupled to receive combustion gases directly from the at least one second pass flue tube and to deliver combustion gases to the exhaust vent.

A method of producing a water heater configured to operate with a non-positive vent static pressure and with a vent gas temperature that avoids or reduces excessive condensate production in an exhaust vent connected to receive combustion gases from the water heater, the method comprising:

• extending a first pass flue tube from a top of a water storage tank to a bottom of the water storage tank;
• positioning a down-fired burner assembly to direct combustion gases into the first pass flue tube;
• extending at least one second pass flue tube from the bottom of the water storage tank to a top of the water storage tank;
• extending a bottom end of the first pass flue tube and a bottom end of the at least one second pass flue tube into an interior of the expansion chamber thereby defining a heat-retaining region of the expansion chamber to further promote the heat transfer between the combustion gases in the expansion chamber and water in the water storage tank through the bottom surface of the water storage tank;
• positioning an expansion chamber below the bottom of the water storage tank, the expansion chamber being coupled to receive the combustion gases from the first pass flue tube and to deliver the combustion gases to the at least one second pass flue tube, wherein an outer perimeter region of the expansion chamber corresponds to an outer perimeter of the water storage tank, thereby configuring the heat retaining region to delay combustion gasses therein;
• the expansion chamber being sized to enable heat transfer from the combustion gases to water in the water storage tank and venting of the combustion gases with the non-positive vent static pressure, while maintaining at least eighty-two percent efficiency of the water heater;
• and
• positioning a combustion gas outlet above the top of the water storage tank, the combustion gas outlet being coupled to receive the combustion gases from the at least one second pass flue tube and to deliver the combustion gases toward the vent with the non-positive vent static pressure.