Patent Publication Number: US-2020278132-A1

Title: Tankless electric water heater

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 14/973,223 filed Dec. 17, 2015, which is based on and claims priority to U.S. Provisional Patent Application No. 62/093,181, filed on Dec. 17, 2014, the entire contents of each are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Water heating is a thermodynamic process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. 
     Water can be heated in vessels known as water heaters, tanks, kettles, cauldrons, pots, or coppers. A metal vessel that heats a batch of water does not produce a continual supply of heated water at a preset temperature. The water temperature varies based on the consumption rate, becoming cooler over time and as flow increases, and the vessel is depleted. 
     SUMMARY 
     The present disclosure is directed to a tankless electric water heater system. The tankless electric water heater has a heating chamber with an inlet at a first end and an outlet at a second end, a heating element connected to the heating chamber, a first temperature sensor disposed near the first end of the heating chamber, a second temperature sensor disposed near the second end of the heating chamber, a flow sensor configured to detect a flow of water and disposed near the heating chamber, and a controller connected to the first and second temperature sensors, the flow sensor, and the heating element. The controller is configured to have a set point temperature, to detect temperature and flow data from the first and second temperature sensors, and the flow sensor, and to provide as output a power setting to the heating element. 
     The foregoing general description of the illustrative implementations and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure, and are not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1A  is an overview diagram of a first liquid heating system, according to one example; 
         FIG. 1B  is an overview diagram of a second liquid heating system, according to one example; 
         FIG. 1C  is an overview diagram of a third liquid heating system, according to one example; 
         FIG. 2A  is a first perspective view of a tankless electric water heater, according to one example; 
         FIG. 2B  is a first perspective view of the tankless electric water heater without a cover, according to one example; 
         FIG. 2C  is a second perspective view of the tankless electric water heater, according to one example; 
         FIG. 2D  is the second perspective view of the tankless electric water heater system without a cover, according to one example; 
         FIG. 2E  is an exploded second perspective view of the tankless electric water heater system, according to one example; 
         FIG. 2F  is a third view of the tankless electric water heater system, according to one example; 
         FIG. 2G  is a fourth view of the tankless electric water heater system without a cover, according to one example; 
         FIG. 2H  is a fifth side view of the tankless electric water heater system without a cover, according to one example; 
         FIG. 3A  is an overview diagram of a tankless electric water heater, according to one example; 
         FIG. 3B  is an overview diagram of a tankless electric water heater, according to one example; 
         FIG. 3C  is an overview diagram of a tankless electric water heater, according to one example; 
         FIG. 4A  is an overview diagram of an electrical system of the tankless electric water heater, according to one example; 
         FIG. 4B  is an overview diagram of an electrical system of the tankless electric water heater connected to an electrically controlled liquid storage device, according to one example; 
         FIG. 4C  is an overview diagram of a gas-fired liquid heating system, according to one example; 
         FIG. 5  is a process diagram for the tankless electric water heater system when connected to a liquid storage device, according to one example; 
         FIG. 6A  is a flow chart depicting a first water heating process of a controller, according to one example; 
         FIG. 6B  is a flow chart depicting a second water heating process of the controller, according to one example; and 
         FIG. 7  is a block diagram illustrating the controller, according to one example. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words “a”, “an” and the like generally carry a meaning of “one or more”, unless stated otherwise. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views. 
       FIG. 1A  is an overview diagram of a first liquid heating system  300 , according to one example. The liquid heating system  300  includes a tankless electric water heater  100  connected to a liquid storage device  200  by a first inlet pipe  204 . The liquid storage device  200  is further connected to a second inlet pipe  202  that supplies water to the liquid storage device  200 . The first inlet pipe  204  transports water from the liquid storage device  200  to the tankless electric water heater  100 . The tankless electric water heater  100  is also connected to an outlet pipe  206  that transports water out of the tankless electric water heater  100  to another system or end user. 
     In one example, the liquid storage device  200  may be connected to a heat source  212  that provides heat to the liquid storage device  200  to heat water inside the liquid storage device  200 . For example, the heat source  212  may derive energy from electricity, natural gas, or geothermal sources. 
     Further, various embodiments of the tankless electric water heater  100  can also be used in conjunction with pool and spa heating, aquariums, hydroponics, radiant, solar, recirculation, industrial processes, and other applications. While the embodiments described herein are connected at the outlet of a liquid storage device  200 , other embodiments of the tankless electric water heater  100  may also be connected at the inlet of, on, at, near, or in a liquid storage device  200  to heat and maintain fluid temperature ranges. 
     An advantageous feature of the tankless electric water heater  100  is the ability to immediately increase the effective volume of heated water available from the liquid storage device  200  equipped with the heat source  212  by heating at the tankless electric water heater  100  a flow of water as it flows out of the liquid storage device  200  rather than continuously heating only a quantity of water in a finite volume, such as that in the liquid storage device  200 . 
     Another advantageous feature of the tankless electric water heater  100  is reduced energy consumption since heat energy is not needed to maintain an elevated water temperature prior to use, as is needed when heated water is stored in the liquid storage device  200  and not used immediately. Energy is wasted to maintain heated water on standby while the water gradually cools and dissipates the heat energy to the atmosphere. The volume of heated water that can be stored has limited utility when the supply of heated water needed during a period of high water consumption, for example in a case where multiple people shower or bath using the same hot water supply in a liquid storage device  200 , exceeds an available volume. 
     Another advantage of the tankless electric water heater  100  is the ability to store water in a liquid storage device  200  at lower temperature, and only heating water as it flows out as needed. Maintaining a largely stagnant tank of water at an elevated temperature may introduce additional risk of growth of certain bacteria that can cause illness and disease in humans, such as  Legionella . The bacteria is known to reside within a variety of soil and aquatic systems and has an ideal temperature growth range from about 90 degrees F. to about 108 degrees F., though its growth range begins at about 77 degrees F. Storing water at a cooler temperature and then heating the water as it leaves the liquid storage device  200  can reduce certain health risks. 
       FIG. 1B  is an overview diagram of a second liquid heating system  300   b , according to one example. The liquid heating system  300   b  includes a tankless electric water heater  100   b  connected to the liquid storage device  200  by the first inlet pipe  204 . The liquid storage device  200  is further connected to the second inlet pipe  202  that supplies water to the liquid storage device  200 . The first inlet pipe  204  transports water from the liquid storage device  200  to the tankless electric water heater  100   b , and the outlet pipe  206  transports water out of the tankless electric water heater  100   b.    
     Further, the tankless electric water heater  100   b  is connected to a recirculation pump  208  and a recirculation pipe  210  at a point before a heating element  128  (further illustrated in at least  FIGS. 2E and 3B ) of the tankless electric water heater  100   b . The recirculation pump  208  recirculates water from the tankless electric water heater  100   b  through the recirculation pipe  210  and the second inlet pipe  202 , back toward the liquid storage device  200 . An inlet proportioning valve  214  may be connected to the second inlet pipe  202  at a point upstream of the recirculation pipe  210 , and a controller of the tankless electric water heater  100   b  may electrically control operation of the recirculation pump  208 , and the opening and closing of the inlet proportioning valve  214  to recirculate water from the liquid storage device  200  back to the liquid storage device  200  to reduce the effect of stratification. The inlet proportioning valve  214  provides for mixing of heated and unheated water flowing into the liquid storage device  200 , allowing for recirculation of only heated water, or inflow of only unheated water. In one example, the liquid storage device  200  may be connected to the heat source  212  that provides energy to the liquid storage device  200  to heat water inside the liquid storage device  200 . 
     Hot water capacity in the liquid storage device  200 , for example a tank, may be limited by stratification, a phenomenon that experimental results have shown can significantly reduce useful hot water capacity of the liquid storage device  200 , further reducing energy efficiency. 
     A liquid storage device  200  without external flow is subject to an ambient temperature, and a thermal stratification of water is formed in the course of a cooling process. Cold water accumulates at the bottom while hot water ascends to the top of the liquid storage device  200 . This phenomenon occurs even if all the water inside the liquid storage device  200  is initially at a uniform temperature. 
     This is because prior to releasing heat to the ambient surroundings, the liquid storage device  200  cools a thin, vertical layer of water along the inside nearest the external atmosphere. Part of this heat is then transferred by diffusion towards the center of the liquid storage device  200 . The water of the thin vertical layer becomes denser than its surrounding and then slips towards the bottom of the liquid storage device  200 , creating stratification. This can effectively reduce usable heated water in the liquid storage device  200 . 
     An advantageous feature of this example of the tankless electric water heater  100   b  is reduced energy loss in the liquid storage device  200  from stratification. Recirculation of heated water from the tankless electric water heater  100  via the recirculation pump  208  results in a more even water temperature distribution inside the liquid storage device  200 . 
     The tankless electric water heater  100   b  further allows the use of a smaller liquid storage device  200  to produce an equivalent amount of hot water as a larger liquid storage device  200 , reducing the total amount of heat energy that is lost to the atmosphere to maintain hot water temperature. 
     In another example, the recirculation pump  208  is connected to the first inlet pipe  204  entirely upstream of the tankless electric water heater  100   b , and the recirculation pipe  210  connects the outlet of the recirculation pump  208  to the second inlet pipe  202 . 
       FIG. 1C  is an overview diagram of a third liquid heating system  300   c , according to one example. The liquid heating system  300   c  includes a tankless electric water heater  100   c  connected to the liquid storage device  200  by the first inlet pipe  204 . The liquid storage device  200  is further connected to the second inlet pipe  202  that supplies water to the liquid storage device  200 . The first inlet pipe  204  transports water from the liquid storage device  200  to the tankless electric water heater  100   c , and an outlet pipe  206  transports water out of the tankless electric water heater  100   c.    
     Further, the tankless electric water heater  100   c  is connected to the recirculation pump  208  and the recirculation pipe  210  at a point after a heating element  128  (further described by  FIG. 3C ). The recirculation pump  208  recirculates water from the tankless electric water heater  100   c  through the recirculation pipe  210  and the second inlet pipe  202 , back toward the liquid storage device  200 . The inlet proportioning valve  214  may be connected to the second inlet pipe  202  at a point before the recirculation pipe  210 , and the controller of the tankless electric water heater  100  may electrically control operation of the recirculation pump  208 , and the opening and closing of the inlet proportioning valve  214  similar to that described with respect to  FIG. 1B . 
     In one example, the recirculation pump  208  is connected to the outlet pipe  206  entirely downstream of the tankless electric water heater  100   c , and the recirculation pipe  210  connects the outlet of the recirculation pump  208  to the second inlet pipe  202 . 
     In one example, the liquid storage device  200  may be connected to the heat source  212  that provides energy to the liquid storage device  200  to heat water inside the liquid storage device  200 . When the recirculation pump  208  and the recirculation pipe  210  exit before the tankless electric water heater  100   b  (as in one example of  FIG. 1B ) only the recirculation pump  208  and heat source  212  provide power to de-stratification. The effect on the tankless electric water heater  100   b  is less wear and tear, especially if recirculated water enters the recirculation pump  208  prior to an inlet fitting  124 , or inlet port, or inlet, or prior to passing through the internal flow sensor  114 . The effect on the liquid storage device  200  is more demand on the heat source  212  in order to elevate the temperature of the entire volume of water in the liquid storage device  200 . The effect with respect to performance, with performance defined as the time it takes to destratify the tank to a uniform temperature, is somewhat slower than what it would take if the recirculation pump  208  and the recirculation pipe  210  are disposed downstream of the tankless electric water heater  100   c , where recirculated water is heated by the heating element  128 , as in one example of  FIG. 1C . This performance gap would exist because of the power output difference in kilowatts (kW) between the heat source  212  and the tankless electric water heater  100   c . The heat source  212  is limited to outputting 4.5 kW to heat the water at any particular moment. The tankless electric water heater  100   c  is able to output 7.2 kW of power in to heat the water at any particular moment in time. The reason for the power disparity is due to requirements of the National Electric Code (NEC). The heat source  212  is classified as a continuous use device, therefore the electrical circuit must be oversized by 125 percent. The tankless electric water heater  100   c  is classified as an intermittent duty device, so the electrical circuit can be sized to 100 percent of the load. 
     An advantageous feature of the tankless electric water heaters  100   a - 100   c  described by  FIG. 1A  through  FIG. 1C , respectively, is that the tankless electric water heaters  100   a - 100   c  may be retrofit to existing infrastructure, electrical wiring, breaker system, plumbing, and an existing liquid storage device  200 , rather than requiring more expensive and complicated replacement with a more powerful and/or higher capacity liquid heating device which requires a new and larger electrical circuit. An example of a more powerful heating device which requires a larger electrical circuit would be a dedicated whole home tankless water heater. An example of a higher capacity liquid heating device is a larger volume liquid storage tank, which may not physically fit where the previous device was. For example, this may be accomplished by removing a segment of one or more pipes, such as a portion connected to the liquid storage device  200  herein referred to as a first inlet pipe  204  and a portion connected to the end user referred to as an outlet pipe  206 . Next the first inlet pipe  204  can be connected to an inlet fitting  124  of the tankless electric water heater  100  and the outlet pipe  206  can be connected to an outlet fitting  126  of the tankless electric water heater  100 . The inlet fitting  124  and the outlet fitting  126  may be molded and fit to a variety of standard and non-standard pipe sizes. A plurality of tankless electric water heaters can be connected in parallel to the inlet pipe  204  and outlet pipe  206  or connected serially to each other to provide additional heating options for increased flow. 
     Further, electrical supply lines  401  may be rerouted from the heat source  212  of the liquid storage device  200  and connected to the tankless electric water heater  100  as illustrated in  FIG. 4B . The heat source  212  is thereafter electrically connected to and controlled by the tankless electric water heater  100  as described further herein based on flow, temperature, inputs and historical data. Another benefit is that the combination of the tankless electric water heater  100  and the liquid storage device  200  provides a longer duration of equivalent hot water than would be available from just the liquid storage device  200 . The addition of the tankless electric water heater  100  to a liquid storage device  200  increases the effective volume of available hot water. 
     Another advantageous feature of the tankless electric water heaters  100   a - 100   c  described by  FIG. 1A  through  FIG. 1C , respectively, is that the tankless electric water heaters  100   a - 100   c  may be combined with a fluid storage water heater as a complete assembly from the factory. This would provide all of the benefits of a stand-alone solution previously described. This would be particularly appealing for new construction or when a full replacement of the existing water heating infrastructure is needed as it will provide more hot water capacity in a smaller footprint without requiring a larger electrical supply circuit or plumbing changes from other commonly available storage water heating solutions on the market today. 
       FIG. 2A  is a first perspective view of the tankless electric water heater  100 , according to one example. The tankless electric water heater  100  includes a cover panel  101  enclosing the internal components of the tankless electric water heater  100 , an outlet fitting  126 , or outlet port, or outlet, connected on a first side of the tankless electric water heater  100  to a second mounting tab  119 , a controller  120  connected to a second side of the tankless electric water heater  100 , and a control knob  140  connected to the controller  120 . The control knob  140  is provided for a user to provide input to the controller  120 , for example scrolling through various user menus and temperature set points. 
       FIG. 2B  is a first perspective view of the tankless electric water heater  100  without the cover panel  101 , according to one example. The tankless electric water heater  100  includes an inlet fitting  124  connected to a mounting plate  102 . An inlet temperature sensor  104 , a high speed switch  112 , and a flow sensor  114  are connected to the inlet fitting  124 . The inlet fitting  124  is further connected to a first conduit  123 . A second conduit  131  is connected to the first conduit  123 , a third conduit  129  and a fourth conduit  133  (labeled but not visible in this view) which connect the conduit  131  to a heating chamber  110 . A tab  125  also connects the first conduit  123  to the heating chamber  110 . 
     A heating element  128  (not shown) is connected to an electrical connection  127 , with the heating element  128  portion disposed within the heating chamber  110 . The electrical connection  127  is connected to the high speed switch  112 , and the high speed switch is controlled by a controller  120  to modulate power to the heating element  128  (further described by  FIG. 4A  and  FIG. 4B ). A control knob  140  connected to the controller  120  provides one way of operating the controller  120 . 
     A first mounting pin  135 , a second mounting pin  136 , a third mounting pin  137 , and a fourth mounting pin  138  (not visible in this view) are connected to the mounting plate  102  and secure the controller  120  to the mounting plate  102 . 
     An outlet temperature sensor  106  is connected to the heating chamber  110 , and a proportioning valve  116  connected to the outlet temperature sensor  106  controls the flow of liquid exiting the tankless electric water heater  100  via the outlet fitting  126 . In one example (not shown), the outlet temperature sensor  106  is located upstream of the heating chamber  110  and the proportioning valve  116 . In another example, the outlet temperature sensor  106  is located downstream of the heating chamber  110  but upstream of the proportioning valve  116  and outlet fitting  126 . A downstream direction is from the inlet fitting  124  to the outlet fitting  126 . 
     A temperature safety switch  118  is connected to the outside of the heating chamber  110  by a switch mount  134 . The controller  120  and a terminal block  122  are further connected to the mounting plate  102 . 
     Water flows into the inlet fitting  124 , from for example the first inlet pipe  204 , at which point the inlet temperature sensor  104  detects a water temperature and the flow sensor  114  detects a flow rate. The water then enters the first conduit  123  and then the second conduit  131 . Based on a temperature setting of the tankless electric water heater  100 , the controller  120  activates the heating element  128  in the heating chamber  110  at a power setting based on the detected temperature by the inlet temperature sensor  104  to increase the temperature of the water. The tab  125 , which provides structural support for the heating chamber  110  and the first conduit  123 , may also, in some examples, transfer heat through conduction from the heating chamber  110  to the first conduit  123 , the second conduit  131 , the third conduit  129 , and the fourth conduit  133 , thereby pre-heating the water that flows into the first conduit  123  and the second conduit  131  before the water enters the heating chamber  110  by way of the third conduit  129  and the fourth conduit  133 . 
     Further, the third conduit  129 , the fourth conduit  133 , and the second conduit  131  form a loop with the heating chamber  110 , allowing for balanced water flow into the heating chamber  110 . In one example, the heating chamber  110  and the heating element  128  may be of a type described by U.S. patent application Ser. No. 13/835,346, the entire contents of which are hereby incorporated by reference herein. Alternatively, the heating element can be any other heating element as would be understood by one of ordinary skill in the art. 
     Once the water has flowed through the heating chamber  110 , the water then flows past the outlet temperature sensor  106  to the outlet proportioning valve  116 . In one example, the outlet proportioning valve  116  is a solenoid valve, an electro-proportional valve, or an electrohydraulic servo valve that can be activated by the controller  120  to seal a portion or all of the liquid flow exiting the tankless electric water heater  100 . If the outlet proportioning valve  116  is not fully closed, water flows through the outlet proportioning valve  116 , and through the outlet fitting  126  to supply another device or end user. The outlet temperature sensor  106  detects a temperature of water exiting the heating chamber  110 . The controller  120  detects temperatures at the inlet temperature sensor  104 , the outlet temperature sensor  106 , and the water flow rate at the flow sensor  114 , and controls the operation of the outlet proportioning valve  116  and the heating element  128  as a function of at least one of the inlet temperature sensor  104  measurement, the outlet temperature sensor measurement  106  and the water flow rate to ensure that water is heated to an appropriate temperature and can continue to be heated at the temperature based on the flow rate. The amount of power (in kilowatts) needed to raise the temperature of an amount of water, defined as a flow rate (Gallons Per Minute), by a specific temperature difference (ΔT, in Fahrenheit), may be determined by an equation: Power (kW)=[Flow Rate (GPM)×ΔT (° F.)]/6.83 
     In one example, the controller  120  uses the equation above to determine how much power to provide to the heating element  128  based on the difference between a set point temperature  130  and the temperature detected at the outlet temperature sensor  106  (where the set point temperature  130  is greater than a reading of outlet temperature sensor  106 ), and the detected flow rate of the flow sensor  114 . 
     In another example, the controller  120  uses the equation above to determine an amount the outlet proportioning valve  116  can be open to maintain a flow rate exiting the tankless electric water heater  100  based on a temperature difference between what is detected by the outlet temperature sensor  106  and the inlet temperature sensor  104 , and an amount of power supplied to the heating element  128 . 
     If electrical load or heat buildup exceeds the design limit, the temperature safety switch  118  may be triggered by the controller  120  to limit or shut down electrical power to the heating element  128 , reducing the risk of damage or equipment failure and thereby helping to ensure safe operation. 
     The terminal block  122  provides electrical power connections between electrical supply lines  220  and the tankless electric water heater  100  ( FIG. 3A ), including a switching mechanism  108 , the heating element  128 , the controller  120 , the high speed switch  112 , and the temperature safety switch  118 , as well as to electrical supply lines  401  to supply power to a heat source  212  of the liquid storage device  200 . Further, the terminal block  122  is connected to the controller  120 , allowing the controller  120  to detect and control the operation of the tankless electric water heater  100 . 
     In one example, if the controller  120  detects a temperature below a threshold at the inlet temperature sensor  104  and/or the outlet temperature sensor  106 , the controller  120  may turn on or increase power to the heating element  128  or the heat source  212 , if applicable, to increase water temperature to a minimum temperature at the outlet temperature sensor  106 . 
     In another example, if the controller  120  detects a temperature below a set point temperature  130  at the outlet temperature sensor  106 , the controller  120  may close the outlet proportioning valve  116 . 
     In another example, if the controller  120  detects a temperature above a set point temperature  130  at the outlet temperature sensor  106 , the controller  120  may close the outlet proportioning valve  116 . 
     In another example, if the controller  120  detects the temperature exceeds a threshold at the outlet temperature sensor  106 , the controller  120  can close the outlet proportioning valve  116  to prevent water from flowing out at an excessive and potentially dangerous temperature. Further, the controller  120  may also reduce or turn off power to the heating element  128  of the tankless electric water heater and/or the heat source  212  of the liquid storage device  200  to allow any water remaining within the tankless electric water heater  100  and the liquid storage device  200  to cool. 
     Although only one heating chamber  110  is illustrated in  FIG. 2B , in other implementations, multiple heating chambers  110  could be provided and linked serially or in parallel via additional conduits thereby providing additional heating capacity for larger flows of liquid. Further, power may be distributed to the heating chambers  110  by load shedding if total power demand of the heating chambers  110  exceeds available power supply. Multiple liquid storage devices  200  and multiple heat sources  212  could be provided and linked serially or in parallel. Power may then also be distributed to the heat sources  212  via the controller  120  by load shedding if total power demand of the heat sources and heating chambers  110  exceeds available power supply. 
     In one example, at least one of the set of the first conduit  123 , the second conduit  131 , the tab  125 , the third conduit  129 , the fourth conduit  133 , and the heating chamber  110  are formed from metals or engineered polymers. 
     In another example (not shown), the outlet temperature sensor  106  is disposed downstream of both the heating chamber  110  and the outlet proportioning valve  116 . 
     In another example, the outlet temperature sensor  106  is disposed downstream of the heating chamber  110  and upstream of the outlet proportioning valve  116 , while a second outlet temperature sensor (not shown) is located downstream of the outlet proportioning valve  116 , allowing measurement of temperature differences that may occur as a result of the position or actuation of the outlet proportioning valve  116 . 
       FIG. 2C  is a second perspective view of the tankless electric water heater  100 , according to one example. The tankless electric water heater  100  includes the cover panel  101  enclosing the internal components of the tankless electric water heater  100 , the inlet fitting  124  and a first mounting tab  117  connected on a third side of the tankless electric water heater  100 , and the controller  120  and the control knob  140  for controlling inputs of the tankless electric water heater  100  connected to the second side of the tankless electric water heater  100 . 
       FIG. 2D  is a second perspective view of a tankless electric water heater  100  without the cover  101 , according to one example. The tankless electric water heater  100  is identical to that described by  FIG. 2B , but shown from the second perspective view, where the terminal block  122  is fully visible. Further, the first mounting tab  117 , a third mounting tab  121 , the second mounting pin  136 , and the fourth mounting pin  138  are also visible in this view, and connected to the mounting plate  102 . The third mounting tab  121  provides support for a power cable (not shown) for the tankless electric water heater  100  to supply the heat source  212  of the liquid storage device  200 . The third mounting tab  121  is further connected to the mounting plate  102 . 
       FIG. 2E  is an exploded second perspective view of the tankless electric water heater  100 , according to one example. The tankless electric water heater  100  is shown without the cover panel  101 . The tankless electric water heater  100  includes the identical components as those shown in  FIGS. 2A through 2D  and like designations are therefore repeated. 
     Further, the first mounting pin  135 , the second mounting pin  136 , the third mounting pin  137 , and the fourth mounting pin  138  are connected to the mounting plate  102  and support the controller  120 . 
       FIG. 2F  is a third view of the tankless electric water heater  100 , according to one example. The tankless electric water heater  100  includes the mounting plate  102 , the inlet fitting  124 , and the outlet fitting  126 . 
       FIG. 2G  is a fourth view of the tankless electric water heater  100  without the cover panel  101 , according to one example. The tankless electric water heater  100  includes similar features as those previously illustrated and therefore like designations are repeated. 
       FIG. 2H  is a fifth view of the tankless electric water heater  100  without the cover  101 , according to one example. From the fifth view, the tankless electric water heater  100  having the mounting plate  102 , the second mounting tab  119 , the outlet fitting  126 , the heating chamber  110 , the heating element  128 , the outlet proportioning valve  116 , the outlet temperature sensor  106 , the controller  120 , the temperature safety switch  118 , the first mounting pin  135 , and the third mounting pin  137  are illustrated and are all connected in the same way as described by  FIG. 2A  through  FIG. 2G . 
       FIG. 3A  is an overview diagram of the tankless electric water heater  100 , according to one example. The tankless electric water heater  100  includes the inlet temperature sensor  104  connected to the flow sensor  114 , the heating element  128  disposed within the heating chamber  110  and connected to the flow sensor  114 , the outlet proportioning valve  116  connected to the heating element  128 , and the outlet temperature sensor  106  connected to the outlet proportioning valve  116 . Further, the tankless electric water heater  100  is connected to the first inlet pipe  204  and connected to the outlet pipe  206 . 
     Water comes into the tankless electric water heater  100  via the first inlet pipe  204 , and then flows by the inlet temperature sensor  104  toward the flow sensor  114 . The inlet temperature sensor  104  measures the temperature of water as it enters the tankless electric water heater  100  before water is further heated within the tankless electric water heater  100  and transmits the measurement to the controller  120 . The flow sensor  114  measures the rate at which water is flowing into the tankless electric water heater  100  and transmits the measurement to the controller  120 . The liquid then flows into the heating chamber  110  and past the heating element  128 . If the heating element  128  is provided with electrical power by the controller  120  based on the measurements, the heating element  128  heats the water to a temperature controlled by the controller  120 . Once the water is past the heating element  128 , the water flows past the outlet temperature sensor  106  toward the outlet proportioning valve  116 . If the outlet proportioning valve  116  is open, water flows through the outlet proportioning valve  116  and out of the tankless electric water heater  100  through the outlet pipe  206 . Otherwise, if the outlet proportioning valve  116  is not open, water does not flow through the outlet proportioning valve  116  and water does not flow out of the tankless electric water heater  100 . 
       FIG. 3B  is an overview diagram of the tankless electric water heater  100   b , according to one example. The tankless electric water heater  100   b , similar to that of  FIG. 3A , further includes the recirculation pump  208  and the recirculation pipe  210 . Identical elements from  FIG. 3A  have the same designations repeated. 
     In one example, the recirculation pump  208  is connected to the tankless electric water heater  100   b  at a point after the inlet temperature sensor  104  and before a heating element  128 . The recirculation pump  208  is further connected to the recirculation pipe  210 , and recirculates water, which may be at an elevated temperature, depending on an operation of the heating element  128 , from the tankless electric water heater  100   b  through the recirculation pipe  210  and back toward the liquid storage device  200  as illustrated and described with respect to  FIG. 1B . In one example, water is only recirculated to the liquid storage device  200  to reduce stratification and is not heated further by the tankless electric water heater  100   b.    
       FIG. 3C  is an overview diagram of the tankless electric water heater  100   c , according to one example. The tankless electric water heater  100   c , similar to that of  FIG. 3B , further includes the recirculation pump  208  and the recirculation pipe  210 . Identical elements from  FIG. 3B  have the same designations repeated. 
     In one example, the recirculation pump  208  is connected to the tankless electric water heater  100   c  at a point downstream of the heating element  128 . The recirculation pump  208  is further connected to the recirculation pipe  210 , and recirculates water, which may be at an elevated temperature, depending on an operation of the heating element  128 , from the tankless electric water heater  100   c  through the recirculation pipe  210  and back toward the liquid storage device  200  as illustrated and described by  FIG. 1C . In addition to reducing stratification, water recirculated to the liquid storage device  200  may also be heated by the tankless electric water heater  100   c , further elevating the temperature of the water in the liquid storage device  200 . 
       FIG. 4A  is an overview diagram of an electrical system of the tankless electric water heater  100  (or  100   b / 100   c ), according to one example. The tankless electric water heater  100  includes the controller  120  connected to electrical supply lines  220 . The electrical supply lines  220  are also connected to a switching mechanism  108 , the temperature safety switch  118 , a high speed switch  112 , and the heating element  128 . The electrical supply lines  220  are further connected to a power source  132  such as a home electrical circuit. The controller  120  controls the amount of power provided to the heating element  128  by modulating the electrical power directed through the high speed switch  112 . The controller  120  further controls electrical power to the high speed switch  112  by controlling the switching mechanism  108  and by maintaining a temperature level or power level below the maximum threshold of the temperature safety switch  118 . Water is heated by the heating element  128  as it passes through the heating chamber  110  (shown, for example, in  FIG. 2B ). Electrical power may also be used by the controller  120  to communicate with, operate, and control various sensors, valves, pumps, wired or wireless communication devices, data storage devices, and battery backup systems as described herein. 
     In one example, further described by  FIG. 3A , the controller  120  detects an amount of water flowing into the tankless electric water heater  100  using measurements from the flow sensor  114 , detects a water temperature coming into the tankless electric water heater  100  using measurements from the inlet temperature sensor  104 , controls an amount of water leaving the tankless electric water heater  100  using the outlet proportioning valve  116 , detects a water temperature exiting the heating element  128  using measurements from the outlet temperature sensor  106 , and compares this to a set point temperature  130 . The controller  120  controls the amount of electrical power directed to the heating element  128  to heat the water to meet the set point temperature  130  and controls the outlet proportioning valve  116  based on the temperature of the water measured by the outlet temperature sensor  106 . For example, the controller  120  can control the outlet proportioning valve  116  to close off the water flow path from the heating chamber  110  to the outlet fitting  126  until the temperature measured by the outlet temperature sensor reaches the set point temperature  130 . At this point, the controller  120  can then open the outlet proportioning valve  116  to an amount such that, based on measurements from the inlet temperature sensor  104  and flow sensor  112 , the water can continue to be heated by the heating element  128  at the set point temperature  130  continuously as the water passes through the tankless electric water heater  100 . 
     Further, in a case where the tankless electric water heater  100  is connected to a recirculation pipe  210 , a recirculation pump  208  and an inlet proportioning valve  214  (as described by  FIG. 1B ), the controller  120  may detect or control operation of the inlet proportioning valve  214  and the recirculation pump  208 . 
       FIG. 4B  is an overview diagram of an electrical system of a tankless electric water heater  100   d  connected to an electrically controlled liquid storage device  200 , according to one example. Here, a switching mechanism  108   d  of  FIG. 4B  includes additional connections via electrical supply lines  401  to the heat source  212  for the liquid storage device  200  that allows the controller  120  to control and specify an amount of electrical power supplied to the heat source  212 . 
     In one example, the liquid storage device  200  is an electric water heater and the heat source  212  electrically heats water in the liquid storage device  200 . The controller  120 , through operation of the switching mechanism  108   d , may divert some or all of the electrical power from the heat source  212  to the heating element  128  to provide greater heating capability in the tankless electric water heater  100   d , such as in a case where heated water is needed immediately. 
     In another example, the controller  120  may operate the switching mechanism  108   d  to divert some or all of the available electrical power to the heat source  212  to provide greater heating capability to the liquid storage device  200 , such as in a case where the controller  120  anticipates a need for a quantity of heated water based on historical usage, through one or more learning algorithms, or a predetermined water heating schedule or time interval. 
     In another example, the controller  120  may operate the switching mechanism  108   d  to shut down electrical power to the tankless electric water heater  100   d  and the liquid storage device  200 . Further, electrical power may be reapplied if the controller  120  detects the possibility water in the system is approaching a low temperature or freezing temperature to prevent system damage or failure. This mode of operation is useful for conserving energy during an extended period without use, for example in an overnight or vacation mode. 
     In another example, the controller  120  may, whether operating on primary or backup power, alert a user of a system error, leak, or failure through a display  920  on the tankless electric water heater  100  and/or through communication with remote devices and networks using wired or wireless methods such as described by a communication process S 80  described by  FIG. 5 . 
     In another example, the high speed switch  112  is a triac, and the controller  120  modulates power applied to the heating element  128 , in order to achieve an outlet water temperature approximately matching the set point temperature  130 . The controller  120  may modulate power to the heating element  128  based on various parameters such as flow, inlet/outlet temperature, and information/data collected from other interfacing apparatuses. The control algorithm may be based on the parameters listed above in conjunction with maximum power settings of the heating element  128  and the set point temperature  130 . The control algorithm may be based on a PID-type (proportional-integral-derivative) control loop feedback mechanism, using pulse width modulation at a calculated frequency, to increase or decrease power supplied to the heating element  128  to control outlet water temperature. 
     An advantageous feature of the tankless electric water heater  100   d , is when it is installed in conjunction with an electric heat source  212  of a liquid storage device  200 , the electrical circuit to both devices may be shared. The controller  120  of the tankless electric water heater  100  is always supplied power and will control when to switch between supplying power to the electric heat source  212  of the liquid storage device  200  or the heating element  128  of the tankless electric water heater  100 , but generally not to both the heat source  212  and the heating element  128  at any one particular time. This mitigates the cost of installing a separate electrical circuit which other tankless electric water heaters need when used as a booster. 
       FIG. 4C  is an overview diagram of a gas-fired liquid heating system  300   g , according to one example. The system  300   g  is similar to that shown in  FIG. 1A  with the addition of a fuel source  450  connected to a gas-fired tankless water heater  100   g  and a gas-fired heat source  212   g  by a fuel supply line  500 . An advantageous feature of the gas-fired tankless water heater  100   g  is when the gas-fired tankless water heater  100   g  is installed in conjunction with the gas-fired heat source  212   g  of a liquid storage device  200 , the fuel supply line  500  to both the gas-fired heat source  212   g  and the gas-fired tankless water heater  100   g  may be shared. The controller  120   g  (not shown as it is disposed inside the gas-fired tankless water heater  100   g ) of the gas-fired tankless water heater  100   g  is generally always supplied electrical power, and will control when to switch between supplying fuel to the gas-fired heat source  212   g  and the gas-fired tankless water heater  100   g . If the fuel supply infrastructure can support the fuel demand, both the gas-fired tankless water heater  100   g  and the gas-fired heat source  212   g  can fire simultaneously to provide maximum hot water capacity. 
       FIG. 5  is a process diagram for the tankless electric water heater  100  when connected to the liquid storage device  200 , according to one example. The process diagram includes a sequence of primary processes of a water heating system operation method  800  for the tankless electric water heater  100  connected to the liquid storage device  200 . The diagram encompasses various operations of the system examples and embodiments described by  FIG. 3A  through  FIG. 2H . The water heating system operation method  800  includes, in this example, an initiating process S 10 , an operating process S 30 , a recording process S 70 , and a communicating process S 80 . 
     S 10  represents a process of initiating use of a controller  120  of the tankless electric water heater  100 , which may include, without limitation, steps related to setting a set point temperature  130 , a date and time, a mode of operation, and a type of system (such as if there is a liquid storage device  200 , electrically heated or otherwise) and a size of the liquid storage device  200 . The steps may be automatic or performed by a user manually via control knob  140  or remotely from an external device such as a mobile device. 
     In one example, the controller  120  operates with preprogrammed default settings for the set point temperature  130 , the date and time, the mode of operation, and the type and the size of the liquid storage device  200  the tankless electric water heater  100  is connected to. 
     In another example, the user sets or adjusts the set point temperature  130 , the date and time, the mode of operation, and the type and the size of the liquid storage device  200  the tankless electric water heater  100  is connected to. 
     S 30  represents a process of the controller  120  operating the tankless electric water heater  100 . This can include steps, where applicable and without limitation, related to powering a heating element  128  of the tankless electric water heater  100  and/or the heat source  212  of a liquid storage device  200 , detecting or deriving system status such as temperatures at the inlet temperature sensor  104 , the outlet temperature sensor  106  or other source, a flow rate from the flow sensor  114 , electrical power usage, a date and a time, and a set point temperature  130 , routing a flow of water by operating the outlet proportioning valve  116 , or controlling the inlet proportioning valve  214  to change the path and source of water leading to the liquid storage device  200 , and pumping the recirculation pump  208  to recirculate water from before or after the heating element  128  to the liquid storage device  200 . 
     Operating the tankless electric water heater  100  to distribute electrical power between the tankless electric water heater  100  and the liquid storage device  200 , if applicable, to heat water in the most efficient way is a sub-process of S 30 , as is detecting and deriving system status and other sensor readings, and then adjusting system operation. 
     In one example, the tankless electric water heater  100  is connected to the liquid storage device  200  and an electrically powered heat source  212 . The controller  120  may operate according to the process diagrams described by  FIG. 6A  and  FIG. 6B , where electrical power may be provided to the heating element  128  of the tankless electric water heater  100  and/or the heat source  212  of the liquid storage device  200  to heat water, or in a combination of ways as described with respect to  FIG. 4B . 
     In another example, the tankless electric water heater  100  is connected to the liquid storage device  200  heated by a heat source  212 , such as a gas heater that is controlled by a separate liquid storage device controller  198 . In this example, the controller  120  controls the tankless electric water heater  100  and can be connected to the device controller  198  to operate the heat source  212  of the liquid storage device  200 . 
     In another example, the tankless electric water heater  100  is connected to an unheated liquid storage device  200 , or a liquid storage device  200  heated by a separately controlled heat source  212  such as gas heat, fire, or hot springs, and the controller  120  controls only the tankless electric water heater  100  independently of any controls that may be connected to the liquid storage device  200 . 
     In another example, the controller  120  detects the flow rate of the flow sensor  114  over a period of time and modulates electrical power provided to the heating element  128  to maintain the temperature of the water passing the outlet temperature sensor  106  to be about the same as the set point temperature  130 . 
     In another example, the controller  120  detects the day or date and time and automatically adjusts power to the tankless electric water heater  100  and the heat source  212  of the liquid storage device  200  to increase or decrease the availability of hot water depending on preprogrammed hot water needs at various times. This is useful for conserving power during days and hours where the demand for hot water is low or nonexistent, and for preparing to supply larger quantities of hot water during periods of high demand. The controller  120  may also apply one or more algorithms, for instance a statistical model, to estimate maximum and minimum demand for hot water from the system by day and time, and adjust electrical power use accordingly. In all examples, the controller  120  may generate or use a plurality of set point temperatures  130  to establish upper and lower temperature limits for operations at different times and conditions. 
     In another example, the controller  120  detects a power outage and switches to operate from a backup power source  132  to continue to maintain the ability to monitor and control some functions of the tankless electric water heater  100 , including communication, as described below by primary process S 80 , to inform external devices or networks of a power outage. Further, if the backup power source  132  possesses sufficient capacity, the tankless electric water heater  100  may be able to continue to operate the heating element  128  and the heat source  212  normally on backup power. 
     In another example, the controller  120  receives input from the primary process S 80  in the form of additional data or direct commands. Such input may be received from devices external to the controller  120 , such as other controllers  120  located in the same or nearby structure. Further, external devices may include devices such as smart phones, smart watches, tablets or computers connected to the controller  120  via wired, wireless, or cellular networks. 
     In another example, the controller  120  maintains water in a liquid storage device  200  at a temperature at or above ambient but relatively low temperature (below about 77 degrees F., for example) so as to help reduce the risk of  Legionella  developing within the liquid storage device  200 . Electrical power is then applied to the heating element  128  to further heat water only as needed. 
     The following examples relate to recirculation of water through the liquid storage device  200  to reduce the extent of stratification. 
     In one example, the recirculation pump  208  recirculates water from before or after the heating element  128  of the tankless electric water heater  100  to the liquid storage device  200  to increase the effectiveness of the liquid storage device  200  by reducing stratification. In one case, water is recirculated from a point before the heating element  128  of the tankless electric water heater  100  to the liquid storage device  200 . In another case, water is recirculated from a point after the heating element  128  of the tankless electric water heater  100  to the liquid storage device  200 , and may be at a higher temperature than that of the water entering the heating element  128 . In either case, the inlet proportioning valve  214  may be open or closed. In a case where the inlet proportioning valve  214  is fully closed, only recirculated water enters the liquid storage device  200  from the recirculation pipe  210 . In a case where the inlet proportioning valve  214  is partly open, water entering the liquid storage device  200  includes a mixture of recirculated water from the recirculation pipe  210  and non-recirculated water from the second inlet pipe  202 . 
     In another example, the controller  120  controls the outlet proportioning valve  116  to be partly or fully open and the recirculation pump  208  is in operation. In this example, the water flowing out of the liquid storage device  200  through the first inlet pipe  204  is divided between the outlet pipe  206  and the recirculation pipe  210 . 
     Further, additional information may be determined through derivation using available data to aid with operating the tankless electric water heater  100 . For example, energy consumption of the heating element  128  can be determined approximately by the controller  120  through a calculation based on the temperatures detected by the inlet temperature sensor  104  and the outlet temperature sensor  106 , and the flow rate of water detected by the flow sensor  114 . 
     S 70  represents a process of recording specification and historical usage data related to uses of a tankless electric water heater  100 , which may include, where applicable and without limitation, size of the liquid storage device  200 , power consumption of the tankless electric water heater  100  and the heat source  212 , a flow rate as detected by the flow sensor  114  and volume of water consumed, inlet and outlet temperatures as measured by the inlet temperature sensor  104  and the outlet temperature sensor  106 , respectively, a set point temperature  130 , room or ambient temperature, and duration of use, including the day or date and time period of use. 
     S 80  represents a process of the controller  120  communicating a status of use or recorded data (see S 70 ) of a tankless electric water heater  100  to external networks or devices and receiving information external to the tankless electric water heater  100 , which may include, where applicable and without limitation, steps related to those of S 30 . 
     These steps may include using information external to the controller  120  to better optimize usage of the tankless electric water heater  100 . This information can be received wirelessly by the controller  120  through a home network as would be understood by one of ordinary skill in the art. Factors may include times when area-wide demand (for a neighborhood or a city, for example) or pricing of electrical power is at a peak or trough, comparing usage patterns of the tankless electric water heater  100  with those of other tankless electric water heater  100  for efficiency or diagnostic purposes, and adjusting operation of the tankless electric water heater  100  so as to better balance resource usage across a power grid or a water supply more readily. Such information may include aggregate data of other devices, such as neighboring tankless electric water heaters  100 , visible to the power grid or water utility but not to the controller  120  of the particular tankless electric water heater  100 . 
     In one example, a remote network may reduce or disable power to or turn off the tankless electric water heater  100  for a period of time in order to conserve power for the power grid. 
     In another example, a remote network may query the controller  120  for diagnostic purposes such as determining if electrical power is available to the tankless electric water heater  100 , or diagnosing the condition of the controller  120  and tankless electric water heater  100 . 
     In another example, the remote network may set or change particular settings of the tankless electric water heater  100 , such as those related to the set point temperature  130 , operation of the switching mechanism  108 , the high speed switch  112 , the outlet proportioning valve  116 , the heating element  128 , the backup power source  132 , the recirculation pump  208 , the liquid storage device controller  198 , and the inlet proportioning valve  214 . 
       FIG. 6A  is a flow chart depicting a first water heating process  850  of the controller  120 , according to one example. At step S 31 , the controller  120  reading measurements from the flow sensor  114  of the flow rate of water coming into the inlet fitting  124  to determine whether water is flowing into the tankless electric water heater  100 . If the controller  120  determines that water is not flowing into the tankless electric water heater  100 , the controller  120  controls the heating element  128  to deactivate if the heating element  128  isn&#39;t already deactivated at step S 34 . If the controller  120  does detect the flow of water at step S 31 , the controller  120  reads measurements from the outlet temperature sensor  106  to determine if water exiting the heating chamber is below the set point temperature  130  at step S 32 . If the controller  120  determines that water is not below the set point temperature  130  at step S 32 , the controller deactivates at step S 34  the heating element  128  if the heating element isn&#39;t already deactivated. If the tankless electric water heater  100  is connected to another heat source  212 , the controller  120  can also control this heat source  212  to be deactivated at step S 35 . At this point, the process  850  then returns to step S 31 . If, however, the controller  120  determines that the temperature is below the set point temperature  130  at step S 32 , the controller  128  provides power to the heating element  128  at step S 33 , and optionally to the heat source  212 , if applicable, at step S 35 . At this point, the process  850  then repeats by returning to step S 31 . 
       FIG. 6B  is a flow chart depicting a second water heating process  860  of the controller  120 , according to one example. At step S 31 , the controller  120  reading measurements from the flow sensor  114  of the flow rate of water coming into the inlet fitting  124  to determine whether water is flowing into the tankless electric water heater  100 . If the controller  120  determines that water is not flowing into the tankless electric water heater  100 , the controller  120  controls the heating element  128  to deactivate if the heating element  128  isn&#39;t already deactivated at step S 34 . If the controller  120  does detect the flow of water at step S 31 , the controller  120  reads measurements from the outlet temperature sensor  106  to determine if water exiting the heating chamber is below the set point temperature  130  at step S 32 . If the controller  120  determines that water is not below the set point temperature  130  at step S 32 , the controller deactivates at step S 34  the heating element  128  if the heating element isn&#39;t already deactivated. If the tankless electric water heater  100  is connected to another heat source  212 , the controller  120  can also control this heat source  212  to be deactivated at step S 35 . At this point, the process  860  then returns to step S 31 . If, however, the controller  120  determines that the temperature is below the set point temperature  130  at step S 32 , the controller  128  provides power to the heating element  128  at step S 33 , and optionally deactivates the heat source  212 , if applicable, at step S 36 . At this point, the process  860  then repeats by returning to step S 31 . 
       FIG. 7  is a block diagram illustrating the controller  120  for implementing the functionality of the tankless electric water heater  100  described herein, according to one example. The skilled artisan will appreciate that the features described herein may be adapted to be implemented on a variety of devices (e.g., a laptop, a tablet, a server, an e-reader, navigation device, etc.). The controller  120  includes a Central Processing Unit (CPU)  910  and a wireless communication processor  902  connected to an antenna  901 . 
     The CPU  910  may include one or more CPUs  910 , and may control each element in the controller  120  to perform functions related to communication control and other kinds of signal processing. The CPU  910  may perform these functions by executing instructions stored in a memory  950 . Alternatively or in addition to the local storage of the memory  950 , the functions may be executed using instructions stored on an external device accessed on a network or on a non-transitory computer readable medium. 
     The memory  950  includes but is not limited to Read Only Memory (ROM), Random Access Memory (RAM), or a memory array including a combination of volatile and non-volatile memory units. The memory  950  may be utilized as working memory by the CPU  910  while executing the processes and algorithms of the present disclosure. Additionally, the memory  950  may be used for long-term data storage. The memory  950  may be configured to store information and lists of commands. 
     The controller  120  includes a control line CL and data line DL as internal communication bus lines. Control data to/from the CPU  910  may be transmitted through the control line CL. The data line DL may be used for transmission of data. 
     The antenna  901  transmits/receives electromagnetic wave signals between base stations for performing radio-based communication, such as the various forms of cellular telephone communication. The wireless communication processor  902  controls the communication performed between the controller  120  and other external devices via the antenna  901 . For example, the wireless communication processor  902  may control communication between base stations for cellular phone communication. 
     The controller  120  may also include the display  920 , a touch panel  930 , an operation key  940 , and a short-distance communication processor  907  connected to an antenna  906 . The display  920  may be a Liquid Crystal Display (LCD), an organic electroluminescence display panel, or another display screen technology. In addition to displaying still and moving image data, the display  920  may display operational inputs, such as numbers or icons which may be used for control of the controller  120 . The display  920  may additionally display a GUI for a user to control aspects of the controller  120  and/or other devices. Further, the display  920  may display characters and images received by the controller  120  and/or stored in the memory  950  or accessed from an external device on a network. For example, the controller  120  may access a network such as the Internet and display text and/or images transmitted from a Web server. 
     The touch panel  930  may include a physical touch panel display screen and a touch panel driver. The touch panel  930  may include one or more touch sensors for detecting an input operation on an operation surface of the touch panel display screen. The touch panel  930  also detects a touch shape and a touch area. Used herein, the phrase “touch operation” refers to an input operation performed by touching an operation surface of the touch panel display with an instruction object, such as a finger, thumb, or stylus-type instrument. In the case where a stylus or the like is used in a touch operation, the stylus may include a conductive material at least at the tip of the stylus such that the sensors included in the touch panel  930  may detect when the stylus approaches/contacts the operation surface of the touch panel display (similar to the case in which a finger is used for the touch operation). 
     In certain aspects of the present disclosure, the touch panel  930  may be disposed adjacent to the display  920  (e.g., laminated) or may be formed integrally with the display  920 . For simplicity, the present disclosure assumes the touch panel  930  is formed integrally with the display  920  and therefore, examples discussed herein may describe touch operations being performed on the surface of the display  920  rather than the touch panel  930 . However, the skilled artisan will appreciate that this is not limiting. 
     For simplicity, the present disclosure assumes the touch panel  930  is a capacitance-type touch panel technology. However, it should be appreciated that aspects of the present disclosure may easily be applied to other touch panel types (e.g., resistance-type touch panels) with alternate structures. In certain aspects of the present disclosure, the touch panel  930  may include transparent electrode touch sensors arranged in the X-Y direction on the surface of transparent sensor glass. 
     The operation key  940  may include one or more buttons or similar external control elements, which may generate an operation signal based on a detected input by the user. In addition to outputs from the touch panel  930 , these operation signals may be supplied to the CPU  910  for performing related processing and control. In certain aspects of the present disclosure, the processing and/or functions associated with external buttons and the like may be performed by the CPU  910  in response to an input operation on the touch panel  930  display screen rather than the external button, key, etc. In this way, external buttons on the controller  120  may be eliminated in lieu of performing inputs via touch operations, thereby improving water-tightness. 
     The antenna  906  may transmit/receive electromagnetic wave signals to/from other external apparatuses, and the short-distance wireless communication processor  907  may control the wireless communication performed between the other external apparatuses. Bluetooth, IEEE 802.11, and near-field communication (NFC) are non-limiting examples of wireless communication protocols that may be used for inter-device communication via the short-distance wireless communication processor  907 . 
     The controller  120  may include a motion sensor  908 . The motion sensor  908  may detect features of motion (i.e., one or more movements) of the controller  120 . For example, the motion sensor  908  may include an accelerometer to detect acceleration, a gyroscope to detect angular velocity, a geomagnetic sensor to detect direction, a geo-location sensor to detect location, etc., or a combination thereof to detect motion of the controller  120 . In certain embodiments, the motion sensor  908  may generate a detection signal that includes data representing the detected motion. For example, the motion sensor  908  may determine a number of distinct movements in a motion (e.g., from start of the series of movements to the stop, within a predetermined time interval, etc.), a number of physical shocks on the controller  120  (e.g., a jarring, hitting, etc., of the electronic device), a speed and/or acceleration of the motion (instantaneous and/or temporal), or other motion features. The detected motion features may be included in the generated detection signal. The detection signal may be transmitted, e.g., to the CPU  910 , whereby further processing may be performed based on data included in the detection signal. The motion sensor  908  can work in conjunction with a Global Positioning System (GPS) section  960 . The GPS section  960  detects the present position of the controller  120 . The information of the present position detected by the GPS section  960  is transmitted to the CPU  910 . An antenna  961  is connected to the GPS section  960  for receiving and transmitting signals to and from a GPS satellite. 
     Thus, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. As will be understood by those skilled in the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting of the scope of the invention, as well as other claims. The disclosure, including any readily discernable variants of the teachings herein, define, in part, the scope of the foregoing claim terminology such that no inventive subject matter is dedicated to the public. 
     The above disclosure also encompasses the embodiments listed below. 
     (1) A fluid heating device including: an inlet, an outlet, a heating chamber disposed between the inlet port and the outlet port, a heating element disposed inside the heating chamber, a flow sensor configured to detect a flow of liquid downstream of the inlet, a first temperature sensor configured to detect a first temperature of the fluid between the heating chamber and the outlet, and a controller configured to regulate a power supply to the heating element as a function of the first temperature. 
     (2) The fluid heating device of (1), further including a conduit connecting the inlet to the heating chamber, wherein a flow path exists from the inlet to the heating chamber via the first conduit and out of the fluid heating device via the outlet. 
     (3) The fluid heating device of (1) or (2), further including a valve upstream of the outlet and downstream of the first temperature sensor, wherein the controller controls the valve as a function of at least one of the first temperature and flow rate. 
     (4) The fluid heating device of any one of (1) to (3), wherein the controller is configured to close the valve to prohibit flow of the liquid until the first temperature is at a predetermined value. 
     (5) The fluid heating device of any one of (1) to (4), wherein the heating chamber includes a first, second and third heating chamber conduit, the first and second heating chamber conduits are configured to provide an inlet to the heating chamber and are connected via the third heating chamber conduit, and the third heating chamber conduit is connected to the first conduit and configured to receive fluid from the inlet. 
     (6) The fluid heating device of any one of (1) to (5), wherein the heating chamber further includes a fourth heating chamber conduit configured to provide a flow path to the outlet for fluid within heating chamber. 
     (7) The fluid heating device of any one of (1) to (6), wherein a flow path exists from the inlet to the outlet via the first, second, third and fourth heating chamber conduits. 
     (8) The fluid heating device of any one of (1) to (7), further including a second temperature sensor configured to detect a second temperature of fluid downstream of the inlet port. 
     (9) The fluid heating device of any one of (1) to (8), wherein the controller is further configured to regulate the power supply to the heating element as a function the second temperature. 
     (10) The fluid heating device of any one of (1) to (9), wherein the second temperature sensor is disposed between the inlet and the flow sensor. 
     (11) The fluid heating device of any one of (1) to (10), wherein the flow sensor is disposed between the conduit and the second temperature sensor. 
     (12) The fluid heating device of any one of (1) to (11), further including a valve upstream of the outlet and downstream of the first temperature sensor, wherein the controller controls the valve as a function of the first temperature, and the second temperature. 
     (13) The fluid heating device of any one of (1) to (12), further including a housing to house the heating chamber, the first temperature sensor and the flow sensor. 
     (14) The fluid heating device of any one of (1) to (13), further including a display screen to display settings of the fluid heating device, and an input to adjust the settings of the fluid heating device. 
     (15) The fluid heating device of any one of (1) to (14), wherein the controller is configured to regulate a power supply to the heating element as a function of the flow. 
     (16) A system including a liquid storage device, an inlet pipe connected to an outlet of the liquid storage device, and a fluid heating device having an inlet connected to the inlet pipe, an outlet, a heating chamber disposed between the inlet and the outlet, a heating element disposed inside the heating chamber, a flow sensor configured to detect a flow of liquid downstream of the inlet, a conduit connecting the inlet and the heating chamber, a first temperature sensor configured to detect a first temperature of the fluid between the heating chamber and the outlet, a controller configured to regulate a supply of power to the heating element as a function the first temperature. 
     (17) The system according to claim  16 , wherein the liquid storage device includes a first power supply, and a liquid storage device heating element, and the fluid heating device further includes a second power supply, and a switch connected to the first power supply and the second power supply, wherein the controller is configured to control the switch to switch between providing a supply of power to the liquid storage device heating element via the first power supply or providing a supply of power to the heating element via the second power supply. 
     (18) The system according to (16) or (17), further including a second inlet pipe connected to the liquid storage device, a recirculation pipe connected to the fluid heating device and the second inlet pipe, and a recirculation pump, wherein the controller is configured to control the recirculation pump to recirculate fluid from the fluid heating device to the liquid storage device via the recirculation pipe. 
     (19) The system according to any one of (16) to (18), wherein the recirculation pipe is connected to the fluid heating device upstream of the heating element. 
     (20) The system according to any one of (16) to (19), wherein the recirculation pipe is connected to the fluid heating device downstream of the heating element. 
     (21) The system according to any one of (16) to (20), further including an inlet proportioning valve connected to the second inlet pipe, wherein controller is configured to control the inlet proportioning valve to control fluid temperature and flow.