Hot water energy conservation

Abstract

The concepts relate to reducing energy loss associated with hot water systems. One example can monitor hot water use in a system. Upon completion of the hot water use, the example can recover some of the hot water from hot water lines into a water heater that heated the hot water. The method can also deliver the recovered hot water to the water heater in a manner that affects operation of a heating element of the water heater.

1 . A system, comprising:
 a water heater having a tank and a cold water inlet to the tank and a hot water outlet from the tank that are positioned relative to an upper region of the tank, a heating element positioned proximate to a lower region of the tank, a recovery pump positioned on the cold water inlet and fluidly coupled to a cold water dip tube extending from the cold water inlet proximate to the lower region of the tank, a circulation pump positioned on the hot water outlet and fluidly coupled to a hot water dip tube extending from the hot water outlet proximate to the lower region of the tank, and, a controller configured to sense hot water being drawn from the tank and to control the recovery pump and the circulation pump responsively after the hot water is drawn from the tank to recover at least some of the hot water and to deliver the recovered hot water to the lower region of the tank via the hot water dip tube.   
     
     
         2 . The system of  claim 1 , wherein the recovery pump is configured to draw water through the cold water dip tube and force the water out of the tank. 
     
     
         3 . The system of  claim 1 , wherein the circulation pump is configured to draw water from the hot water outlet and force the water down the hot water dip tube. 
     
     
         4 . The system of  claim 1 , further comprising a recovery apparatus associated with the cold water inlet and the cold water dip tube. 
     
     
         5 . The system of  claim 4 , wherein the recovery apparatus is external to the tank or wherein the recovery apparatus is positioned in the tank and wherein the cold water dip tube comprises a cold water dip tube that is positioned within a large cold water dip tube that couples the recovery apparatus to the cold water inlet. 
     
     
         6 . The system of  claim 1 , further comprising a thermostat that is controllably coupled to the heating element and is positioned proximate to the heating element and wherein the hot water dip tube ends below the heating element. 
     
     
         7 . The system of  claim 1 , wherein the heating element comprises a gas burner that is positioned below the tank or wherein the heating element comprises an electrical heating element that is positioned in the lower region of the tank. 
     
     
         8 . The system of  claim 1 , further comprising a cold water line fluidly coupled to the cold water inlet and a hot water line coupled to the hot water outlet and a fixture fluidly coupled to an opposite end of the hot water line and the cold water line and further comprising a selective hot water isolation device positioned between the hot water line and the cold water line proximate to the fixture. 
     
     
         9 . The system of  claim 8 , further comprising a controller communicatively coupled to the circulation pump, the recovery pump, and the selective hot water isolation device and configured to activate the circulation pump, the recovery pump, and the selective hot water isolation device to recover hot water from the hot water line to the lower region of the tank via the hot water dip tube. 
     
     
         10 . The system of  claim 9 , wherein the controller is configured to measure heat energy in the water heater and in the hot water line and to control the heating element based upon both the heat energy in the water heater and the heat energy in the hot water line. 
     
     
         11 . A water heater comprising:
 a tank extending between upper and lower regions and a cold water inlet at the upper region of the tank and a hot water outlet at the upper region of the tank;   a heating element positioned proximate the lower region of the tank;   a cold water dip tube extending from the cold water inlet to the lower region of the tank;   a hot water dip tube extending from the hot water outlet to the lower region of the tank;   a check valve at the hot water outlet that is configured to allow water to travel out of the upper region of the tank through the hot water outlet but that allows water flow from the hot water outlet through the hot water dip tube into the lower region of the tank and prevents water flow from the hot water outlet into the upper region of the tank.   
     
     
         12 . The water heater of  claim 11 , wherein the heating element comprises a gas burner that is positioned below the tank or wherein the heating element comprises an electrical heating element that is positioned in the lower region of the tank. 
     
     
         13 . The water heater of  claim 11 , wherein the cold water dip tube comprises a small cold water dip tube and a large cold water dip tube. 
     
     
         14 . The water heater of  claim 13 , wherein the small cold water dip tube is positioned within the large cold water dip tube or outside the large cold water dip tube. 
     
     
         15 . The water heater of  claim 14 , further comprising a recovery assembly fluidly coupled to both the hot water dip tube and the cold water dip tube and wherein the recovery assembly is configured to store mechanical energy when water flows through the large cold water dip tube in a first direction and wherein the recovery assembly is configured to release that mechanical energy after water flow stops in the first direction to force water to move in the opposite direction through the small cold water dip tube. 
     
     
         16 . A water heater comprising:
 a tank extending between upper and lower regions and a cold water inlet at the upper region of the tank and a hot water outlet at the upper region of the tank;   a hot water dip tube fluidly coupled to the hot water outlet and terminating at the lower region of the tank; and,   a check valve positioned on the hot water outlet that allows water to exit through the hot water outlet from the upper region of the tank and through the hot water dip tube but blocks water from entering the upper region of the water heater through the hot water outlet and allows water to enter the water heater through the hot water dip tube to the lower region.