Modular water heating and tank system management

Abstract

A water heating system includes a storage tank, at least one heating unit, and a control system. The storage tank includes a recirculation supply port, a return port arranged above the recirculation supply port, and a tank temperature sensor arranged between the recirculation supply port and the return port in a vertical direction. The at least one heating unit includes a water inlet port fluidly coupled to the recirculation supply port and a water outlet port fluidly coupled to the return port. The control system is configured to receive a signal from the tank temperature sensor indicative of a temperature of water in the storage tank, determine a need for heating based on the signal, activate the at least one heating unit to draw water from the storage tank, heat the water, return the heated water to the storage tank, and reduce a rate at which the water is heated.

What is claimed is: 
     
         1 . A water heating system comprising:
 a storage tank having a recirculation supply port, a return port arranged above the recirculation supply port in a vertical direction, and a tank temperature sensor arranged between the recirculation supply port and the return port in the vertical direction;   at least one heating unit having a water inlet port and a water outlet port, the water inlet port being fluidly coupled to the recirculation supply port and the water outlet port being fluidly coupled to the return port; and   a control system communicatively coupled to the tank temperature sensor and the at least one heating unit, the control system configured to:
 receive a signal from the tank temperature sensor indicative of a temperature of water in the storage tank at a location of the tank temperature sensor, 
 determine, based on the signal received from the tank temperature sensor, a need for heating, 
 activate, in response to determining the need for heating, the at least one heating unit to draw water from the storage tank by way of the recirculation supply port, heat said water, and return said heated water to the storage tank by way of the return port, and 
 reduce a rate at which said water is heated in response to determining that a first criterion and a second criterion have been met. 
   
     
     
         2 . The water heating system of  claim 1 , wherein reducing the rate at which said water is heated comprises stopping operation of the at least one heating unit. 
     
     
         3 . The water heating system of  claim 1 , wherein the at least one heating unit is a heat pump heating unit. 
     
     
         4 . The water heating system of  claim 1 , wherein the control system is configured to determine that the need for heating is caused by one of a draw demand and a standby loss. 
     
     
         5 . The water heating system of  claim 1 , wherein the at least one heating unit includes an inlet water temperature sensor arranged to measure a temperature of water entering the water inlet port and an outlet water temperature sensor arranged to measure a temperature of water exiting the water outlet port, the inlet water temperature sensor and the outlet water temperature sensor being communicatively coupled to the control system, and wherein the control system is configured to determine that the first criterion and the second criterion have been met based on signals received from the inlet water temperature sensor and the outlet water temperature sensor. 
     
     
         6 . The water heating system of  claim 5 , wherein the control system is configured to determine that one of the first and second criterion have been met by comparing the temperature of water exiting the water outlet port to a predetermined temperature limit. 
     
     
         7 . The water heating system of  claim 6 , wherein the control system is configured to determine that the other of the first and second criterion has been met by comparing the temperature of water entering the water inlet port to a predetermined temperature limit. 
     
     
         8 . The water heating system of  claim 1 , wherein the at least one heating unit is one of a plurality of such heating units connected fluidly in parallel with one another to the recirculation supply port and the water outlet port, and wherein the control system is configured to determine which one of the plurality of heating units to activate in response to determining the need for heating. 
     
     
         9 . The water heating system of  claim 8 , wherein, after activating one of the plurality of heating units in response to determining the need for heating, the control system is further configured to:
 receive temperature signals from the tank temperature sensor over a period of time;   determine, based on said temperature signals, that an increased rate of heating is desired; and   increase the rate of heating by the plurality of heating units in response to determining that the increased rate of heating is desired.   
     
     
         10 . The water heating system of  claim 9 , wherein the control system is configured to increase the rate of heating by activating another one of the plurality of heating units to draw water from the storage tank by way of the recirculation supply port, heat said water, and return said heated water to the storage tank by way of the return port. 
     
     
         11 . The water heating system of  claim 9 , wherein the control system is configured to determine that an increased rate of heating is desired at least in part by determining that a temperature change of water at the location of the tank temperature sensor over the period of time is below a threshold. 
     
     
         12 . A method for controlling a water heating system comprising:
 receiving a signal from a tank temperature sensor indicative of a temperature of a fluid in a storage tank at a location of the tank temperature sensor;   determining, based on the signal received from the tank temperature sensor, a need for heating;   activating, in response to determining the need for heating, at least one heating unit to draw fluid from the storage tank; and   reducing a rate at which the water is heated in response to determining that a first criterion and a second criterion have been met.   
     
     
         13 . The method of  claim 12 , wherein reducing the rate at which the water is heated includes stopping operation of the at least one heating unit. 
     
     
         14 . The method of  claim 12 , further comprising:
 determining that the need for heating is caused by one of a draw demand and a standby loss.   
     
     
         15 . The method of  claim 12 , further comprising:
 determining that the first criterion and the second have been met based on signals received from an inlet water temperature sensor of the at least one heating unit and an outlet water temperature sensor of the at least one heating unit.   
     
     
         16 . The method of  claim 15 , wherein determining that one of the first and second criterion has been met includes comparing a temperature of water exiting a water outlet port of the at least one heating unit to a predetermined temperature limit. 
     
     
         17 . The method of  claim 16 , wherein determining that the other of the first and second criterion has been met includes comparing a temperature of water entering a water inlet port of the at least one heating unit to a predetermined temperature limit. 
     
     
         18 . The method of  claim 12 , wherein:
 the at least one heating unit includes a plurality of heating units fluidly connected in parallel; and   activating the at least one heating unit to draw water from the storage tank includes determining which one of the plurality of heating units to activate.   
     
     
         19 . The method of  claim 18 , further comprising:
 after activating one of the plurality of heating units:
 receiving temperature signals from the tank temperature sensor over a period of time, 
 determining, based on the received temperature signals, that an increased rate of heating is desired, and 
 increasing the rate of heating by the plurality of heating units in response to determining that the increased rate of heating is desired. 
   
     
     
         20 . The method of  claim 19 , further comprising:
 increasing the rate of heating by activating another one of the plurality of heating units to draw water from the storage tank and return heated water to the storage tank; and   determining that an increased rate of heating is desired at least in part by determining that a temperature change of fluid at the location of the tank temperature over the period of time is below a threshold.   
     
     
         21 . An apparatus for controlling a water heating system comprising:
 an electronic controller operatively coupled to a tank temperature sensor, the electronic controller configured to:
 receive a signal from the tank temperature sensor, the tank temperature sensor positioned at a vertical location in a tank, 
 determine, based on the signal, whether a fluid temperature at the vertical location transitions from a first temperature region to a second temperature region, wherein a temperature of the first region is greater than a temperature of the second temperature region, the first temperature region is separated from the second temperature region by a thermocline, and the electronic controller is configured to determine that the fluid temperature at the vertical location transitioned from the first temperature region to the second temperature region by detecting the thermocline passing over the tank temperature sensor; and 
 in response to determining that the fluid temperature at the vertical location transitioned from the first temperature region to the second temperature region, command one or more heater units to begin a draw demand response. 
   
     
     
         22 . The apparatus of  claim 21 , wherein the vertical location is located between a recirculation supply port of the tank and a return port of the tank. 
     
     
         23 . The apparatus of  claim 21 , wherein the electronic controller is configured to command the one or more heater units to begin the draw demand response by:
 activating a first heater unit;   determining whether a heating rate of the first heater unit is sufficient to meet a draw demand; and   in response to determining that the heating rate of the first heater unit is not sufficient to meet the draw demand, activating a second heater unit.   
     
     
         24 . The apparatus of  claim 21 , wherein the electronic controller is configured to:
 receive a second signal from an inlet temperature sensor arranged to measure a temperature of fluid entering an inlet of one of the one or more heater units;   receive a third signal from an outlet temperature sensor arranged to measure a temperature of fluid exiting an outlet of the one or more heater units; and   deactivate the one or more heater units based on the first signal and the second signal meeting one or more conditions.   
     
     
         25 . The apparatus of  claim 24 , wherein the electronic controller is configured to deactivate the one or more heater units based on the first signal and the second signal meeting one or more conditions by comparing the temperature of fluid entering the inlet of the one or more heater units to a first temperature threshold. 
     
     
         26 . The apparatus of  claim 25 , wherein the electronic controller is configured to deactivate the one or more heater units based on the first signal and the second signal meeting one or more conditions by comparing the temperature of fluid exiting the outlet of the one or more heater units to a second temperature threshold. 
     
     
         27 . The apparatus of  claim 21 , wherein:
 the one or more heater units includes a plurality of heater units; and   the electronic controller is configured to:
 monitor each heater unit of the plurality of heater units for a fault condition, 
 in response to detecting a fault condition at a first heater unit of the plurality of heater units, deactivate the first heater unit and activate a second heater unit of the plurality of heater units. 
   
     
     
         28 . The apparatus of  claim 21 , wherein the electronic controller is configured to:
 receive a fourth signal from a supply temperature sensor arranged to measure a temperature of fluid exiting the tank through a hot water supply port; and   compare the temperature of fluid exiting the tank to a temperature limit.   
     
     
         29 . The apparatus of  claim 28 , wherein the electronic controller is configured to:
 in response to determining that the temperature of fluid exiting the tank is below the temperature limit, increase a heating rate of the one or more heater units.   
     
     
         30 . The apparatus of  claim 29 , wherein the electronic controller is configured to increase the heating rate of the one or more heater units by activating an additional heater unit. 
     
     
         31 . A method for controlling a water heating system comprising:
 receiving a signal from a tank temperature sensor, the tank temperature sensor positioned at a vertical location in a tank;   determining, based on the signal, whether a fluid temperature at the vertical location transitions from a first temperature region to a second temperature region, wherein a temperature of the first region is greater than a temperature of the second temperature region, the first temperature region is separated from the second temperature region by a thermocline, and determining that the fluid temperature at the vertical location transitioned from the first temperature region to the second temperature region includes detecting the thermocline passing over the tank temperature sensor; and   in response to determining that the fluid temperature at the vertical location transitioned from the first temperature region to the second temperature region, commanding one or more heater units to begin a draw demand response.   
     
     
         32 . The method of  claim 31 , wherein the vertical location is located between a recirculation supply port of the tank and a return port of the tank. 
     
     
         33 . The method of  claim 31 , wherein commanding the one or more heater units to begin the draw demand response includes:
 activating a first heater unit;   determining whether a heating rate of the first heater unit is sufficient to meet a draw demand; and   in response to determining that the heating rate of the first heater unit is not sufficient to meet the draw demand, activating a second heater unit.   
     
     
         34 . The method of  claim 31 , further comprising:
 receiving a second signal from an inlet temperature senor arranged to measure a temperature of water entering an inlet of one of the one or more heater units;   receiving a third signal from an outlet temperature sensor arranged to measure a temperature of water exiting an outlet of the one or more heater units; and   deactivating the one or more heater units based on the first signal and the second signal meeting one or more conditions.   
     
     
         35 . The method of  claim 34 , wherein deactivating the one or more heater units based on the first signal and the second signal meeting one or more conditions includes comparing the temperature of water entering the inlet of the one or more heater units to a first temperature threshold. 
     
     
         36 . The method of  claim 35 , wherein deactivating the one or more heater units based on the first signal and the second signal meeting one or more conditions includes comparing the temperature of water exiting the outlet of the one or more heater units to a second temperature threshold. 
     
     
         37 . The method of  claim 31 , wherein:
 the one or more heater units includes a plurality of heater units; and   the method includes:
 monitoring each heater unit of the plurality of heater units for a fault condition; and 
 in response to detecting the fault condition at a first heater unit of the plurality of heater units, deactivating the first heater unit and activating a second heater unit of the plurality of heater units. 
   
     
     
         38 . The method of  claim 31 , further comprising:
 receiving a fourth signal from a supply temperature sensor arranged to measure a temperature of water exiting the tank through a hot water supply port; and   comparing the temperature of water exiting the tank to a temperature limit.   
     
     
         39 . The method of  claim 38 , further comprising:
 in response to determining that the temperature of water exiting the tank is below the temperature limit, increasing a heating rate of the one or more heater units.   
     
     
         40 . The method of  claim 39 , wherein increasing the heating rate of the one or more heaters includes activating an additional heater unit.