System and method of hot water recirculation using a bi-directional cold-water supply line

Abstract

A recirculation pump system provides the ability to recirculate water from a water heater outlet, back into a water heater inlet through a cold-water supply line. The recirculation pump system pumps heated water, which may have cooled to a sub-optimal temperature, into a water heater. The recirculation pump system provides the ability to use a plumbing network that does not contain a dedicated recirculation line. The recirculation pump system uses a water pump to circulate water, a temperature sensor to control system activation based on water temperature, and a check valve to control the direction of fluid flow. This recirculation pump system provides a minimally invasive way to install a recirculation system into a plumbing network that otherwise would not be able to accommodate recirculation functions, and service modern plumbing fixtures efficiently.

What is claimed is: 
     
         1 . A recirculation pump system comprising:
 an inlet adapted to be fluidically connected to a hot-water supply line;   an outlet adapted to be fluidically connected to a cold-water supply line;   a temperature sensor configured to sense a temperature at the inlet;   a water pump configured to pump water from the inlet to the outlet upon the temperature sensor detecting a lower threshold temperature; and   a check valve configured to prevent water flow from the outlet to the inlet.   
     
     
         2 . The recirculation pump system of  claim 1  wherein the water pump is further configured to stop pumping water from the inlet to the outlet upon the temperature sensor detecting an upper threshold temperature. 
     
     
         3 . The recirculation pump system of  claim 1 , wherein the upper threshold temperature is adjustable and may be set at 120 degrees Fahrenheit. 
     
     
         4 . The recirculation pump system of  claim 1 , wherein the lower threshold temperature is adjustable and may be set at 110 degrees Fahrenheit. 
     
     
         5 . The recirculation pump system of  claim 1 , wherein the check valve is configured to be positioned between the water pump and the outlet. 
     
     
         6 . A water recirculation system comprising:
 a heat engine, having a cold-water inlet and a hot-water outlet, a hot-water supply line adapted to be fluidically connected to the hot-water outlet;   an inlet adapted to be fluidically connected to the hot-water supply line;   an outlet adapted to be fluidically connected to a cold-water supply line;   the cold-water supply line adapted to be fluidically connected to the cold-water inlet;   a temperature sensor configured to sense a temperature in the hot-water supply line;   a water pump configured to pump water from the hot-water supply line to the cold-water supply line upon the temperature sensor detecting a lower threshold temperature; and   a check valve configured to prevent water flow from the cold-water supply line to the water pump.   
     
     
         7 . The water recirculation system of  claim 6 , wherein the water pump is further configured to stop pumping water in from the inlet to the outlet upon the temperature sensor detecting an upper threshold temperature. 
     
     
         8 . The water recirculation system of  claim 6 , wherein the upper threshold temperature is adjustable and may be set at 120 degrees Fahrenheit. 
     
     
         9 . The water recirculation system of  claim 6 , wherein the lower threshold temperature is adjustable and may be set at 110 degrees Fahrenheit. 
     
     
         10 . The water recirculation system of  claim 6 , wherein the water pump is configured to circulate water from the hot-water supply line through the cold-water supply line to the cold-water inlet of the heat engine. 
     
     
         11 . The water recirculation system of  claim 6 , wherein at least one or more plumbing fixtures are fluidically connected to the hot-water supply line and the cold-water supply line. 
     
     
         12 . The water recirculation system of  claim 6 , wherein the water pump is coupled across the hot-water supply line, and the cold-water supply line at a furthest plumbing fixture from the hot-water outlet. 
     
     
         13 . The water recirculation system of  claim 11 , wherein one or more plumbing fixtures are fluidically connected between the furthest plumbing fixture and the heat engine. 
     
     
         14 . The water recirculation system of  claim 10 , wherein one or more of the plumbing fixtures are configured to operate on a cycle that draws an amount of water from the hot-water supply line that is less than an amount of water in the hot-water supply line between the hot-water outlet and the one or more of the plumbing fixtures. 
     
     
         15 . The water recirculation system of  claim 6 , wherein the heat engine is a tankless water heater. 
     
     
         16 . A method of recirculating hot water comprising:
 activating a water pump in a water recirculation system;   circulating, by the water pump, water from a hot-water supply line through a cold-water supply line to a cold-water inlet of a heat engine inlet;   circulating, by the water pump, water from a hot-water outlet of the heat engine to the hot-water supply line;   measuring a temperature of the water in the hot-water supply line;   deactivating the water pump when the water reaches an upper threshold temperature.   
     
     
         17 . The method of recirculating hot water of  claim 16 , further comprising:
 reactivating the water pump when the water in the hot-water supply line falls below a lower threshold temperature.   
     
     
         18 . The method of recirculating hot water of  claim 16 , wherein the upper threshold temperature is adjustable and may be set at 120 degrees Fahrenheit. 
     
     
         19 . The method of recirculating hot water of  claim 17 , wherein the lower threshold temperature is adjustable and may be set at 110 degrees Fahrenheit. 
     
     
         20 . The method of recirculating hot water of  claim 16 , wherein the heat engine is a tankless water heater.