Multi-tank water heater systems

Abstract

A water heater system including two or more water storage tanks plumbed in series, parallel or a combination thereof and methods of controlling said water heater systems. The water heater systems may include one or more mixing valves and one or more temperature sensors for providing water at a desired temperature.

What is claimed is: 
     
         1 . A water heater system for providing heated water for use by occupants of a building, comprising:
 a first water storage tank having a first water inlet and a first water outlet;   a second water storage tank having a second water inlet and a second water outlet;   a water line fluidly connecting the first water outlet to the second water inlet for transporting water from the first water storage tank to the second water storage tank;   a mixing valve having a first inlet fluidly coupled to the second water outlet downstream of the second water storage tank, the mixing valve being controllable via a communications interface;   a cold water supply line in fluid communication with a second inlet of the mixing valve;   a mixed water outlet fluidly coupled to an outlet of the mixing valve; and   a controller for controlling the mixing valve via the communications interface.   
     
     
         2 . The water heater system of  claim 1 , further comprising a temperature sensor positioned in the mixed water outlet and in communication with the controller. 
     
     
         3 . The water heater system of  claim 2 , wherein the controller adjusts a ratio of cold water entering the mixing valve from the cold water supply line to heated water entering the mixing valve from the second water outlet to achieve a desired temperature at the mixed water outlet. 
     
     
         4 . The water heater system of  claim 3 , wherein the controller adjusts the ratio of cold water entering the mixing valve from the cold water supply line to heated water entering the mixing valve from the second water outlet based on feedback received from the temperature sensor. 
     
     
         5 . The water heater system of  claim 1 , wherein the first water storage tank has a setpoint lower than a setpoint of the second water storage tank, and the setpoint of the second water storage tank is greater than a desired outlet water temperature of the water heater system. 
     
     
         6 . The water heater system of  claim 1 , further comprising a temperature sensor positioned in the cold water supply line and in communication with the controller. 
     
     
         7 . A water heater system, the system comprising:
 a first water storage tank having a first water inlet and a first water outlet;   a second water storage tank having a second water inlet and a second water outlet;   a cold water supply line in fluid communication with the first water inlet of the first water storage tank and the second water inlet of the second water storage tank;   a hot water supply line in fluid communication with the first water outlet and the second water outlet, wherein water from the first water storage tank is mixed with water from the second water storage tank in the hot water supply line;   a mixing valve having a first inlet fluidly coupled to the hot water supply line and a second inlet coupled to the cold water supply line;   a mixed water outlet fluidly coupled to an outlet of the mixing valve.   
     
     
         8 . The water heater system of  claim 7 , further comprising a controller for controlling the mixing valve via a communications interface. 
     
     
         9 . The water heater system of  claim 8 , further comprising a temperature sensor positioned in the mixed water outlet and in electrical communication with the controller, wherein the controller adjusts a ratio of cold water entering the mixing valve from the cold water supply line to water entering the mixing valve from the hot water supply line to achieve a desired temperature at the mixed water outlet. 
     
     
         10 . The water heater system of  claim 7 , wherein the first water storage tank has a setpoint approximately equal to a setpoint of the second water storage tank, and the setpoints of the first and second water storage tanks are greater than a desired outlet water temperature of the water heater system. 
     
     
         11 . The water heater system of  claim 9 , further comprising one or more additional temperature sensors positioned in the hot water supply line and in communication with the controller. 
     
     
         12 . The water heater system of  claim 9 , further comprising a temperature sensor positioned in the cold water supply line and in communication with the controller. 
     
     
         13 . A water heater system, the system comprising:
 a first water storage tank having a first water inlet and a first water outlet;   a second water storage tank having a second water inlet and a second water outlet;   a cold water supply line in fluid communication with the first water inlet of the first water storage tank and the second water inlet of the second water storage tank;   a first hot water supply line in fluid communication with the first water outlet of the first water storage tank;   a first mixing valve having a first inlet fluidly coupled to the first hot water supply line and a second inlet coupled to the cold water supply line, the first mixing valve being controllable via a first communications interface;   a first mixed water outlet fluidly coupled to an outlet of the first mixing valve;   a second hot water supply line in fluid communication with the second water outlet of the second water storage tank;   a second mixing valve having a first inlet fluidly coupled to the second hot water supply line and a second inlet coupled to the first mixed water outlet of the first mixing valve, the second mixing valve being controllable via a second communications interface;   a second mixed water outlet fluidly coupled to an outlet of the second mixing valve; and   a controller for controlling the first mixing valve via the first communications interface and the second mixing valve via the second communications interface.   
     
     
         14 . The water heater system of  claim 13 , further comprising a first temperature sensor positioned in the second mixed water outlet and in electrical communication with the controller, wherein the controller adjusts a ratio of water entering the second mixing valve from the first mixed water outlet to water entering the second mixing valve from the second hot water supply line to achieve a desired temperature at the second mixed water outlet. 
     
     
         15 . The water heater system of  claim 14 , further comprising a second temperature sensor positioned in the first mixed water outlet and in electrical communication with the controller, wherein the controller adjusts a ratio of water entering the first mixing valve from the cold water supply line to water entering the first mixing valve from the first hot water supply line to achieve a desired temperature at the first mixed water outlet. 
     
     
         16 . The water heater system of  claim 14 , further comprising one or more additional temperature sensors positioned in the first or second hot water supply lines and in communication with the controller. 
     
     
         17 . The water heater system of  claim 14 , further comprising a third temperature sensor positioned in the cold water supply line and in communication with the controller. 
     
     
         18 . A water heater system, the system comprising:
 a first water storage tank having a first water inlet and a first water outlet;   a second water storage tank having a second water inlet and a second water outlet;   a cold water supply line in fluid communication with the first water inlet of the first water storage tank and the second water inlet of the second water storage tank;   a first hot water supply line in fluid communication with the first water outlet of the first water storage tank;   a first mixing valve having a first inlet fluidly coupled to the first hot water supply line and a second inlet coupled to the cold water supply line, the first mixing valve being controllable via a first communications interface;   a first mixed water outlet fluidly coupled to an outlet of the first mixing valve;   a second hot water supply line in fluid communication with the second water outlet of the second water storage tank;   a second mixing valve having a first inlet fluidly coupled to the second hot water supply line and a second inlet coupled to the cold water supply line, the second mixing valve being controllable via a second communications interface;   a second mixed water outlet fluidly coupled to an outlet of the second mixing valve;   a third mixing valve having a first inlet fluidly coupled to the first mixed water output of the first mixing valve and a second inlet coupled to the second mixed water output of the second mixing valve, the third mixing valve being controllable via a third communications interface;   a third mixed water outlet fluidly coupled to an outlet of the third mixing valve;   a controller for controlling the first mixing valve via the first communications interface, the second mixing valve via the second communications interface and the third mixing valve via the third communications interface.   
     
     
         19 . The water heater system of  claim 18 , further comprising a first temperature sensor positioned in the third mixed water outlet and in electrical communication with the controller, wherein the controller adjusts a ratio of water entering the third mixing valve from the first mixed water outlet to water entering the third mixing valve from the second mixed water outlet to achieve a desired temperature at the third mixed water outlet. 
     
     
         20 . The water heater system of  claim 19 , further comprising:
 a second temperature sensor positioned in the first mixed water outlet and in electrical communication with the controller, wherein the controller adjusts a ratio of water entering the first mixing valve from the cold water supply line to water entering the first mixing valve from the first hot water supply line to achieve a desired temperature at the first mixed water outlet; and   a third temperature sensor positioned in the second mixed water outlet and in electrical communication with the controller, wherein the controller adjusts a ratio of water entering the second mixing valve from the cold water supply line to water entering the second mixing valve from the second hot water supply line to achieve a desired temperature at the second mixed water outlet.   
     
     
         21 . The water heater system of  claim 20 , further comprising one or more additional temperature sensors positioned in the first or second hot water supply lines and in communication with the controller. 
     
     
         22 . The water heater system of  claim 20 , further comprising a fourth temperature sensor positioned in the cold water supply line and in communication with the controller. 
     
     
         23 . The water heater system of  claim 18 , wherein the water heater system includes three or more water storage tanks and four or more mixing valves. 
     
     
         24 . A water heater system for providing heated water for use by occupants of a building, comprising:
 a cold water inlet line;   a hot water outlet line;   a first water heater having a first water inlet and a first water outlet;   a second water heater having a second water inlet and a second water outlet;   configurable plumbing coupled to the cold water inlet line, the hot water outlet line, the first water inlet, the first water outlet, the second water inlet and the second water outlet, wherein the configurable plumbing includes one or more controllable valves that, when in a first state, plumb the first water heater and the second water heater in a series configuration between the cold water inlet line and the hot water outlet line, and when in a second state, plumb the first water heater and the second water heater in a parallel configuration between the cold water inlet line and the hot water outlet line; and   a controller for selectively switching the one or more controllable valves between the first state and the second state.   
     
     
         25 . The water heater system of  claim 24 , wherein the controller switches the one or more controllable valves between the first state and the second state depending on the current or expected load on the water heater system. 
     
     
         26 . The water heater system of  claim 24 , wherein the controller switches the one or more controllable valves between the first state and the second state depending on a time of day. 
     
     
         27 . The water heater system of  claim 24 , further comprising one or more additional temperature sensors positioned in the first or second hot water supply lines and in communication with the controller. 
     
     
         28 . The water heater system of  claim 24 , further comprising a temperature sensor positioned in the cold water supply line and in communication with the controller. 
     
     
         29 . A method for controlling of a water heater system having two or more water storage tanks, the method comprising:
 monitoring a first change in temperature of water in a first water storage tank;   monitoring a second change in temperature of water in a second water storage tank;   determining if the first change in temperature is different from the second change in temperature by at least a threshold amount;   controlling a setpoint temperature of the first water storage tank and a setpoint temperature of the second water storage tank in accordance with a first control algorithm if the first change in temperature is different from the second change in temperature by at least the threshold amount; and   controlling the setpoint temperature of the first water storage tank and the setpoint temperature of the second water storage tank in accordance with a second control algorithm that is different from the first control algorithm if the first change in temperature is not different from the second change in temperature by at least the threshold amount.   
     
     
         30 . The method of  claim 29 , wherein the first control algorithm is configured to adjust the setpoint temperature of the first water storage tank and the setpoint temperature of the second water storage tank to be substantially the same temperature setpoint. 
     
     
         31 . The method of  claim 30 , wherein the second control algorithm is configured to adjust the setpoint temperature of the first water storage tank to be less than the setpoint temperature of the second water storage tank. 
     
     
         32 . A water heater system, the system comprising:
 a water storage tank having a cold water inlet and a hot water outlet;   a cold water supply line in fluid communication with the cold water inlet;   a mixing valve having a first inlet fluidly coupled to the hot water outlet and a second inlet coupled to the cold water supply line, the mixing valving having an electrical control input;   a mixed water outlet fluidly coupled to an outlet of the mixing valve;   a temperature sensor; and   a controller in electrical communication with the temperature sensor for controlling the mixing valve via the electrical control input at the mixing valve.   
     
     
         33 . The water heater system of  claim 32 , wherein the temperature sensor includes a first temperature sensor positioned in the mixed water outlet, wherein the controller adjusts a ratio of cold water entering the mixing valve from the cold water supply line to water entering the mixing valve from the hot water outlet to achieve a desired temperature at the mixed water outlet. 
     
     
         34 . The water heater system of  claim 33 , further comprising a second temperature sensor positioned in the hot water outlet and in communication with the controller. 
     
     
         35 . The water heater system of  claim 34 , further comprising a third temperature sensor positioned in the cold water supply line and in communication with the controller.