High-efficiency condensing water heater

Abstract

Aspects of the invention relate to water heaters including a water storage tank having a top wall, a bottom wall, and a side wall extending between the top wall and the bottom wall; a combustion chamber extending below the bottom wall of the water storage tank and a heat exchanger configured to receive combustion gases and to transfer heat to water in the water storage tank. The heat exchanger includes a first pass flue extending through the water storage tank and a plurality of second pass flues coupled to receive combustion gases from the first pass flue. The second pass flues extending through the water storage tank and having a straight top portion, a curved bottom portion, and a longitudinal axis residing in a plane. The curved bottom portion of the second pass flues exits the water storage tank through at least one aperture defined in the side wall of the water storage tank.

What is claimed: 
     
         1 . A water heater comprising:
 a water storage tank configured to store water to be heated, the water storage tank having a top wall, a bottom wall, and a side wall extending between the top wall and the bottom wall;   a combustion chamber extending below the bottom wall of the water storage tank; and   a heat exchanger configured to receive combustion gases from the combustion chamber and to transfer heat to water stored in the water storage tank, the heat exchanger including   a first pass flue coupled to receive combustion gases from the combustion chamber, the first pass flue extending through the water storage tank from the bottom wall of the water storage tank to the top wall of the water storage tank, and   a plurality of second pass flues coupled to receive combustion gases from the first pass flue, the second pass flues extending through the water storage tank from the top wall of the water storage tank toward the bottom wall of the water storage tank, wherein each of the second pass flues has a straight top portion and a curved bottom portion, and wherein the curved bottom portion of each of the second pass flues exits the water storage tank through at least one aperture defined in the side wall of the water storage tank;   wherein each of the second pass flues is contained within a first half of the water storage tank, the first half of the water storage tank extending in a direction along a length of the first pass flue.   
     
     
         2 . The water heater of  claim 1 , wherein the side wall has a curved portion in which the at least one aperture is defined, each of the second pass flues exits the water storage tank through the at least one aperture defined in the curved portion of the side wall. 
     
     
         3 . The water heater of  claim 1 , each of the second pass flues having a first end and a second end, wherein the longitudinal axis of each of the second pass flues at the first end forms an angle with the longitudinal axis at the second end that is between 90° and 130°. 
     
     
         4 . The water heater of  claim 3 , wherein a distance between the curved portions of the second pass flues is smaller than a distance between the second ends of the second pass tubes. 
     
     
         5 . The water heater of  claim 1 , further comprising an exhaust conduit positioned to receive combustion gas from each of the second pass flues, the exhaust conduit being positioned proximal to the first half of the water storage tank.