WATER HEATERS WITH MULTIPLE HEATING ELEMENTS

Abstract

A water heating unit includes at least one electrical heating element, a relay configured to allow electrical current to flow through the at least one electrical heating element when the relay is in a closed state and to prevent electrical current from flowing through the at least one electrical heating element when the relay is in an open state, and a controller in communication with the relay to switch the relay between the closed state and the open state. The controller is configured to perform at least one of: maintaining the relay in the open state upon receiving a signal indicating that another water heating unit of the plurality of water heating units is in a heating mode and, upon placing the relay in the closed state, transmitting a signal in order to prevent another water heating unit from entering into a heating mode.

Claims

1. A water heating unit for a water heating system having a plurality of water heating units connected to a single electrical circuit, comprising: at least one electrical heating element; a relay configured to allow electrical current to flow through the at least one electrical heating element when the relay is in a closed state and to prevent electrical current from flowing through the at least one electrical heating element when the relay is in an open state; and a controller in communication with the relay to switch the relay between the closed state and the open state, wherein the controller is configured to perform at least one of: maintaining the relay in the open state upon receiving a signal indicating that another water heating unit of the plurality of water heating units is in a heating mode; and upon placing the relay in the closed state, transmitting a signal in order to prevent another water heating unit of the plurality of water heating units from entering into a heating mode.

2. The water heating unit of claim 1, further comprising a current sensing device, wherein said signal indicating that another water heating unit of the plurality of water heating units is in a heating mode is received by the controller from the current sensing device.

3. The water heating unit of claim 2, further comprising a plurality of wiring terminals, the plurality of wiring terminals comprising: a first wiring terminal by which the water heating unit is configured to connect to a first electrical phase of the electrical circuit; a second wiring terminal by which the water heating unit is configured to connect to a second electrical phase of the electrical circuit; and a third wiring terminal by which the water heating unit is configured to be electrically connected to the another water heating unit of the plurality of water heating units, wherein the third wiring terminal and one of the first and second wiring terminals are electrically connected and wherein the current sensing device is arranged to detect a flow of current between the third wiring terminal and the one of the first and second wiring terminals.

4. The water heating unit of claim 1, further comprising a current interrupt device, wherein said signal to prevent another water heating unit of the plurality of water heating from entering into a heating mode is transmitted by the controller to the current interrupt device.

5. The water heating unit of claim 4, further comprising a plurality of wiring terminals, the plurality of wiring terminals comprising: a first wiring terminal by which the water heating unit is configured to connect to a first electrical phase of the electrical circuit; a second wiring terminal by which the water heating unit is configured to connect to a second electrical phase of the electrical circuit; and a third wiring terminal by which the water heating unit is configured to be electrically connected to the another water heating unit of the plurality of water heating units, wherein the third wiring terminal and one of the first and second wiring terminals are electrically connected to the current interrupt device such that current is prevented from flowing between the third wiring terminal and the one of the first and second wiring terminals when said signal is transmitted by the controller to the current interrupt device.

6. The water heating unit of claim 1, wherein the controller is in wired or wireless communication with a controller of another water heating unit of the plurality of water heating units in order to receive said signal indicating that another water heating unit of the plurality of water heating units is in a heating mode or to transmit said signal to prevent another water heating unit of the plurality of water heating units from entering into a heating mode.

7. A water heating unit for a water heating system having a plurality of water heating units connected to a single electrical circuit, comprising: at least one electrical heating element; a relay configured to allow electrical current to flow through the at least one electrical heating element when the relay is in a closed state and to prevent electrical current from flowing through the at least one electrical heating element when the relay is in an open state; and a plurality of wiring terminals comprising: a first wiring terminal by which the water heating unit is configured to connect to a first electrical phase of the electrical circuit; a second wiring terminal by which the water heating unit is configured to connect to a second electrical phase of the electrical circuit; and a third wiring terminal by which the water heating unit is configured to be electrically connected to another water heating unit of the plurality of water heating units.

8. The water heating unit of claim 7, wherein current from the electrical circuit is directed to flow between the third wiring terminal and one of the first and the second wiring terminals without flowing through the at least one electrical heating element when said another water heating unit is operating in a heating mode.

9. The water heating unit of claim 8, further comprising a current sensor arranged to detect the flow of current between the third wiring terminal and the one of the first and the second wiring terminals.

10. The water heating unit of claim 8, further comprising a switch arranged between the third wiring terminal and the one of the first and the second wiring terminal such that current is only able to flow between the third wiring terminal and the one of the first and the second wiring terminal when the switch is in a closed state.

11. The water heating unit of claim 10, wherein the switch and the relay are a single component, wherein the switch is in the closed state when the relay is in the open state and wherein the switch is not in the closed state when the relay is in the closed state.

12. A water heating system comprising: a first water heating unit connected to an electrical circuit to receive electrical power therefrom, the first water heating unit comprising at least one electric heating element; and a second water heating unit connected to the electrical circuit to receive electrical power therefrom, the second water heating unit comprising at least one electric heating element; wherein a flow of electric current through the at least one electric heating element of the second water heating unit is prevented when the at least one electric heating element of the first water heating unit is in an operational state.

13. The water heating system of claim 12, further comprising wiring extending between the first and second water heating units to provide electrical power from the electrical circuit to one of the first and second water heating units.

14. The water heating system of claim 12, wherein the first and second water heating units are fluidly connected in series such that water is directed from the second water heating unit to the first water heating unit.

15. The water heating system of claim 12, wherein the first water heating unit further comprises a first controller, wherein the second water heating unit further comprises a second controller, and wherein the first controller is in communication with the second controller to prevent the flow of electric current through the at least one electric heating element of the second water heating unit when the at least one electric heating element of the first water heating unit is in an operational state.

16. The water heating system of claim 12, wherein the second water heating unit further comprises a relay connected electrically in series with at least one electric heating element, the relay being configured to allow current flow through the at least one electric heating element when the relay is in a closed state and to prevent current flow through the at least one electric heating element when the relay is in an open state, wherein the relay is able to transition between the open state and the closed state independently from the at least one electric heating element of the first water heating unit being in an operational state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic illustration of an example water heating system, according to some embodiments.

[0021] FIG. 2 is a schematic diagram showing additional details of the junction boxes of FIG. 1, according to some embodiments.

[0022] FIG. 3 is a schematic diagram showing additional details of the water heating system of FIG. 1, according to some embodiments.

[0023] FIG. 4 is a schematic diagram showing additional details of the water heating system of FIG. 1, according to some embodiments.

[0024] FIG. 5 is a schematic diagram showing additional details of the junction boxes of FIG. 1, according to some embodiments.

[0025] FIG. 5A is a schematic diagram showing additional details of the junction boxes of FIG. 1, according to some embodiments.

[0026] FIGS. 6 and 7 are flowcharts illustrating an example process for controlling operation of the water heating system of FIG. 1, according to some embodiments.

[0027] FIG. 8 is a schematic diagram showing additional details of the water heating system of FIG. 1, according to some embodiments.

[0028] FIG. 9 is a schematic diagram showing additional details of the junction boxes of FIG. 1, according to some embodiments.

[0029] FIGS. 10 and 11 are flowcharts illustrating an example process for controlling operation of the water heating system of FIG. 1, according to some embodiments.

[0030] FIG. 12 is a schematic diagram showing additional details of the water heating system of FIG. 1, according to some embodiments.

[0031] FIG. 13 is a schematic diagram showing additional details of the junction boxes of FIG. 1, according to some embodiments.

[0032] In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

[0033] FIG. 1 is a schematic illustration of an example water heating system 100, according to some embodiments. As illustrated in FIG. 1, some examples of the water heating system 100 include one or more hot water heater units, such as water heater unit 102 (labeled WH1 in FIG. 1) and water heater unit 104 (labeled WH2 in FIG. 1). Although two water heater units 102 and 104 are shown in the example of FIG. 1, different implementations of the system 100 may include any number of water heater units, including a single water heater unit or more than two water heater units. In various implementations, the water heater units may be fluidly connected in series. For example, the water heater unit 102 may receive cold water from a cold water line 106, heat the cold water, and deliver the heated water to the water heater unit 104. The water heater unit 104 receives the heated water from the water heater unit 102, further heats the water, and delivers the further heated water to the end user via a hot water line 108. In various implementations, the system 100 includes an expansion tank (not shown), which may be installed on the cold water line 106 near the water heater unit 102 to absorb excess pressure in the cold water line 106 caused by the expansion of the water in the line as it heats up.

[0034] Each water heater unit may include a tank for holding water. For example, the water heater unit 102 may include a tank 110 and the water heater unit 104 may include a tank 112. In some examples, each tank includes an outer shell, an inner shell, and an insulation layer between the outer shell and the inner lining. The outer shell may include a material such as steel. The inner shell may include material such as steel, and may further include a corrosion-resistant lining including a material such as glass or a polymer coating, and be configured to contain a fluid such as water. The insulation material may include a material that minimizes and/or reduces heat transfer from the contents of the interior of the respective tank to an external ambient environment (such as, for example, fiberglass or a polyurethane foam). Each tank may include an inlet for receiving water to be heated. For example, the tank 110 may include an inlet 114, and the tank 112 may include an inlet 116. Each inlet may be positioned near the top of the respective tank and include a dip tube. The dip tube may terminate near the bottom of the respective tank so that water received via the inlet enters the interior of the respective tank near the bottom.

[0035] Each tank may also include an outlet for providing heated water from the respective tank. For example, the tank 110 may include an outlet 118, and the tank 112 may include an outlet 120. Each outlet may be positioned near the top of the respective tank. Thus, water to be heated enters each tank at a lower portion of the tank and is removed from the tank at an upper portion of the tank. Since the density of liquid water decreases as its temperature increases, heated water is more buoyant than the unheated water and naturally rises to the top of the tank. Positioning the outlet near the top of the tank thus may ensure that heated water is drawn from the tank while the dip tube may ensure that water to be heated enters the tank away from the heated water and does not mix with the heated water.

[0036] In the example of FIG. 1, the inlet 114 of the tank 110 is connected to the cold water line 106, the outlet 118 of the tank 110 is connected to the inlet 116 of the tank 112, and the outlet 120 of the tank 112 is connected to the hot water line 108. Each tank may include one or more heating elements, such as one or more electric resistance heating elements. For example, the tank 110 may include a heating element 124 positioned at a top portion (such as a top half) of the tank 110 and a heating element 126 positioned at a bottom portion (such as a bottom half) of the tank 110. Similarly, the tank 112 may include a heating element 128 positioned at a top portion of the tank 112 and a heating element 130 positioned at a bottom portion of the tank 112. Although FIG. 1 illustrates each tank including two heating elements, in other implementations of the system 100, each tank may include a single heating element or more than two heating elements.

[0037] In operation, cold water from the cold water line 106 may enter the tank 110 via the inlet 114, be heated within the tank 110 by the heating element 124 and/or the heating element 126, exit the tank 110 via the outlet 118, be transferred to the tank 112 via the water transfer line 122 and the inlet 116, be heated within the tank 112 by the heating element 128 and/or the heating element 130, and be provided to the hot water line 108 via the outlet 120.

[0038] In various implementations, each heating element may include a respective control unit that controls an operation of the heating element. For example, the water heater unit 102 may include a control unit 132 for controlling operation of the heating element 124 and a control unit 134 for controlling operation of the heating element 126. Similarly, the water heater unit 104 may include a control unit 136 for controlling operation of the heating element 128 and a control unit 138 for controlling operation of the heating element 130.

[0039] Each water heater unit may also include one or more temperature sensors positioned to sense a temperature of the tank or a temperature of water within the tank. In various implementations, a temperature sensor may be positioned near each heating element. In some examples, a temperature sensor may be positioned near or integrated with a control unit. For example, the tank 110 may include a temperature sensor 144 and a temperature sensor 146, and the tank 112 may include a temperature sensor 148 and a temperature sensor 150. Examples of suitable temperature sensors include thermistors, thermocouples, resistance temperature detectors, digital temperature strips, bimetallic strips, semiconductor temperature sensors, etc.

[0040] In some examples, each water heater unit also includes a junction box for providing electrical power to components of the water heater unit. In various implementations, one or more of the junction boxes may connect to an electrical circuit powering the system 100, and one or more of the junction boxes may connect to and power another junction box. The junction box for a water may be integrated within the outer shell of the water heater unit, or may be attached to the outer shell of the water heater unit, or may be a separate component from the water heater unit and be only electrically connected thereto.

[0041] In the example of FIG. 1, the junction box 140 of the water heater unit 102 is electrically connected to the heating elements 124 and 126, the control units 132 and 134, and the junction box 142. In the example of FIG. 1, the junction box 142 of the water heater unit 104 is electrically connected to the heating elements 128 and 130, the control units 136 and 138, the junction box 140, and the electrical circuit powering the system 100. Accordingly, the junction box 142 may receive electrical power from the electrical circuit powering the system 100 and provide electrical power to the heating elements 128 and 130, the control units 136 and 138, and the junction box 140. The junction box 140 may receive electrical power from the junction box 142 and provide electrical power to the heating elements 124 and 126 and the control units 132 and 134.

[0042] FIG. 2 is a schematic diagram 200 showing additional details of the junction box 140 and the junction box 142, according to some embodiments. In the example of FIG. 2, the junction box 142 includes a multipole terminal block 202 and the junction box 140 includes a multipole terminal block 204. The terminal block 202 may include three terminal block poles, such as terminal block pole 206, terminal block pole 208, and terminal block pole 210. The terminal block 204 may include three terminal block poles, such as terminal block pole 212, terminal block pole 214, and terminal block pole 216. In various implementations, the third terminal block pole 216 may be omitted from the terminal block 204. It should be understood by one of skill in the art that the terminal block poles depicted are only one nonlimiting example of wiring terminals, and that the same effect can be achieved by other types of wiring terminals. By way of example, a wiring nut could be used to replace each of terminal block poles 206, 208, 210, 212, 214, or 216 with similar effect.

[0043] In the example of FIG. 2, wiring from the electrical circuit powering the system 100 includes three wires: a wire 218 connected to a first phase of the electrical circuit powering the system 100 (labeled L1 in FIG. 2), a wire 220 connected to a second phase of the electrical circuit powering the system 100 (labeled L2 in FIG. 2), and a ground wire 222 (labeled GND in FIG. 2). The voltage between the wire 218 and the wire 220 may correspond to the line voltage of the electrical circuit powering the system 100 (such as, for example, about 240 volts).

[0044] The wire 218 may be connected to the terminal block pole 206, the wire 220 may be connected to the terminal block pole 208, and the ground wire 222 may be connected to a body (such as a metal body) of the junction box 142. Additional wiring may be used to connect the junction box 142 to the junction box 140. In the example of FIG. 2, wire 224 connects the terminal block pole 210 to the terminal block pole 212, wire 226 connects the terminal block pole 208 to the terminal block pole 214, and the ground wire 222 extends between the junction boxes 142 and 140. In various implementations, the ground wire 222 is connected to a body (such as a metal body) of the junction box 140.

[0045] The load sides of the terminal blocks 202 and 204 may include one or more connection points (such as nodes) for connecting to other components of the system 100. For example, the terminal block pole 206 includes a node 228 (labeled A in FIG. 2), the terminal block pole 208 includes a node 230 (labeled B in FIG. 2), and the terminal block pole 210 includes a node 232 (labeled E in FIG. 2). Similarly, the terminal block pole 212 includes a node 234 (labeled C in FIG. 2) and the terminal block pole 214 includes a node 236 (labeled D in FIG. 2). In various implementations, each node may be at the respective terminal block pole. In some examples, each node is connected to the respective terminal block pole by wiring.

[0046] In the example of FIG. 2, the node 228 is electrically connected to the wire 218 via the terminal block pole 206, the node 230 is electrically connected to the wire 220 via the terminal block pole 208, node 236 is electrically connected to the wire 220 via the terminal block pole 214 and the terminal block pole 208, and nodes 232 and 234 are electrically connected to each other via the terminal block poles 210 and 212.

[0047] FIG. 3 is a schematic diagram 300 showing additional details of the water heating system 100, according to some embodiments. In some examples, each of the control units 132-138 includes a switch or a current interrupt device, such as a relay having at least two poles and in some cases three poles (labeled 1, 2, and 3 in FIG. 3). For example, the control unit 136 includes a thermostat relay having poles 302, 304, and 306 (labeled 1, 2, and 3, respectively in FIG. 3), the control unit 138 includes a thermostat relay having poles 308, 310, and 312 (labeled 1, 2, and 3, respectively in FIG. 3), the control unit 132 includes a thermostat relay having poles 314, 316, and 318 (labeled 1, 2, and 3, respectively in FIG. 3), and the control unit 134 includes a thermostat relay having poles 320 and 322 (labeled 1 and 2, respectively in FIG. 3). In various implementations, the control unit 134 may include a pole similar to pole 3 of the control units 132, 136, and 138.

[0048] Each control unit may include or be connected to a temperature sensor (such as any of the previously described temperature sensors) that measures the tank or water temperature at each respective location. When the temperature reading of the temperature sensor is less than or equal to a threshold, the control unit will be in a first closed or connected position, with pole 1 electrically connected to pole 2. In the first position, the control unit completes an electrical circuit including a respective heating element. However, when the temperature reading of the temperature sensor is greater than the threshold, the control unit will be in a second open or disconnected position, with pole 1 electrically disconnected from pole 2 and connected to pole 3 (when applicable). In the second position, the respective heating element is disconnected from the electrical circuit, and the control unit may complete an electrical circuit to the next control unit. Each control unit may be able to transition between an open state (e.g., where the respective relay is disconnected) and a closed state (e.g., where the respective relay is connected) independently).

[0049] Thus, in examples where the control units are arranged in series, the first control unit may be electrically connected to the electrical circuit powering the system 100. The first control unit connects the first heating element (connected to the first control unit) to the electrical circuit in the first position and disconnects the first heating element and connects control units in the second position. A subsequent control unit will be connected to the electrical circuit only when each control unit ahead of the subsequent control unit (e.g., control unit positioned closer to the electrical circuit powering the system 100) is in the second position. Thus, a subsequent heating element connected to the subsequent control unit may only be powered on when each heating element ahead of the subsequent heating element in the series is electrically disconnected from the electrical circuit powering the system 100 (regardless of the open or closed state of the subsequent control unit). Accordingly, the order of heating elements in the series may form a priority order, with heating elements closer to the electrical circuit powering the system 100 having a higher priority than further heating elements.

[0050] In the example of FIG. 3, the pole 302 of the control unit 136 is connected to the node 228, the pole 304 of the control unit 136 is connected to the heating element 128, and the pole 306 of the control unit 136 is connected to pole 308 of the subsequent control unit 138. Thus, in the first state, poles 302 and 304 are connected, resulting in line voltage being applied to the heating element 128 (e.g., connecting the heating element 128 to power). In the second state, poles 302 and 304 are disconnected (e.g., disconnecting the heating element 128 from power) and poles 302 and 306 are connected (e.g., connecting the subsequent control unit 138 to power). Thus, when the temperature sensed at the temperature sensor 148 is less than or equal to the threshold, the heating element 128 is connected to power and subsequent control units (e.g., control units 138, 132, and 134) and their associated heating elements are disconnected from power. When the temperature sensed at the temperature sensor 148 is greater than the threshold, the heating element 128 is disconnected from power and the subsequent control units are connected to power.

[0051] In the example of FIG. 3, the pole 310 of the control unit 138 is connected to the heating element 130, and the pole 312 of the control unit 138 is connected to the pole 314 (for example, via nodes 232 and 234) of the subsequent control unit 132. Thus, in the first state, poles 308 and 310 are connected, connecting the heating element 130 to power when all control units ahead of the control unit 138 are in the second state. In the second state, poles 308 and 310 are disconnected (e.g., disconnecting the heating element 130 from power) and poles 308 and 312 are connected (e.g., connecting the subsequent control unit 132 to power when all control units ahead of the control unit 138 are in the second state). Thus, when the temperature sensed at the temperature sensor 150 is less than or equal to the threshold, subsequent control units (e.g., control units 132 and 134) and their associated heating elements are disconnected from power. When the temperature sensed at the temperature sensor 150 is less than or equal to the threshold and all control units ahead of the control unit 138 (e.g., control unit 136) are in the second state, the heating element 130 is connected to power. When the temperature sensed at the temperature sensor 150 is greater than the threshold, the heating element 130 is disconnected from power and the subsequent control units (e.g., control units 132 and 134) are connected to power.

[0052] In the example of FIG. 3, the pole 316 of the control unit 132 is connected to the heating element 124, and the pole 318 of the control unit 132 is connected to the pole 320 of the subsequent control unit 134. Thus, in the first state, poles 314 and 316 are connected, connecting the heating element 124 to power when all control units ahead of the control unit 132 are in the second state. In the second state, poles 314 and 316 are disconnected (e.g., disconnecting the heating element 124 from power) and poles 314 and 318 are connected (e.g., connecting the subsequent control unit 134 to power when all control units ahead of the control unit 132 are in the second state). Thus, when the temperature sensed at the temperature sensor 144 is less than or equal to the threshold, subsequent control units (e.g., control unit 134) and their associated heating elements are disconnected from power. When the temperature sensed at the temperature sensor 144 is less than or equal to the threshold and all control units ahead of the control unit 132 (e.g., control units 136 and 138) are in the second state, the heating element 124 is connected to power. When the temperature sensed at the temperature sensor 144 is greater than the threshold, the heating element 124 is disconnected from power and the subsequent control units (e.g., control unit 134) are connected to power.

[0053] In the example of FIG. 3, the pole 322 of the control unit 134 is connected to the heating element 126. Thus, in the first state, poles 320 and 322 are connected, connecting the heating element 126 to power when all control units ahead of the control unit 134 are in the second state. In the second state, poles 320 and 322 are disconnected (e.g., disconnecting the heating element 126 from power). Thus, when the temperature sensed at the temperature sensor 146 is less than or equal to the threshold and all control units ahead of the control unit 134 (e.g., control units 134, 136, and 138) are in the second state, the heating element 126 is connected to power. When the temperature sensed at the temperature sensor 146 is greater than the threshold, the heating element 126 is disconnected from power.

[0054] Accordingly, the control units 132-138 collectively operate the heating elements 124-130 according to a priority order, with each control unit powering on a respective heating element only when (i) any higher-priority heating elements are not powered on and (ii) the temperature sensed at the control unit is less than or equal to the threshold. In the example of FIG. 3, the priority order for the heating elements is (in order from the highest priority to the lowest priority) heating element 128, heating element 130, heating element 124, followed by heating element 126. Additionally, in various implementations, the control unit closest to the electrical circuit powering the system 100 (e.g., the highest priority control unit 136) may include an energy cut-off (ECO) switch (e.g., ECO switch 324) that opens the electrical circuit in case of the tank temperature exceeding a preset limit. Since the control unit 136 is the first control unit in the series, disconnecting the control unit 136 also disconnects subsequent control units, preventing any heating element in the system 100 from being powered on. In various implementations, the highest priority control unit of each tank (e.g., control units 136 and 132) may each include an ECO switch. For example, control unit 132 may include an ECO switch 326.

[0055] The control unit 134 can optionally be provided with a third pole (not shown) in similar fashion to the control units 132, 136, and 138. In such an alternative embodiment, that third pole and the terminal block pole 216 of terminal block 204 can be electrically connected to a common node. Such a configuration allows for the water heater units 102 and 104 to be identical and interchangeable, with the priority order determined by the line-side wiring of the associated junction boxes 140, 142 (e.g. at the time of installation). It should be further understood by one of skill in the art that additional water heater units could additionally be installed in a similar series arrangement.

[0056] FIG. 4 is a schematic diagram 400 showing additional details of the water heating system 100, according to some embodiments. In various implementations, the water heater units of the water heating system 100 are implemented with a microprocessor-based controller. The controller may include one or more electronic processors and non-transitory computer-readable storage media containing instructions executable by the one or more electronic processors to perform the various processes, methods, and techniques described in this specification. Each water heater unit (such as the water heater units 102 and 104) may include a controller, which may be operatively coupled and control the control units of the water heater unit. Thus, while FIG. 4 illustrates an example implementation of the water heater unit 102, various implementations of the water heater unit 104 are similarly implemented.

[0057] In the example of FIG. 4, the water heater unit 102 includes a controller 402. The controller 402 may be operatively coupled to and control the control unit 132 and the control unit 134. In various implementations, the control unit 132 and the control unit 134 include electronic relays that open and close in response to a low-voltage signal received from the controller 402. Thus, the controller 402 may place and/or maintain the electronic relays in the open or closed state using the low-voltage signal. However, unlike the thermostat relays illustrated in FIG. 3, poles 3 may be omitted from each electronic relay. The controller 402 may receive a temperature signal from each temperature sensor at the tank 110. For example, the controller 402 receives a temperature signal (T1) from the temperature sensor 144 and a temperature signal (T2) from the temperature sensor 146. The temperature signal (T1) may indicate a temperature of the tank 110 or water within the tank 110 near the heating element 124 or the control unit 132, and the temperature signal (T2) may indicate a temperature of the tank 110 or water within the tank 110 near the heating element 126 or the control unit 134.

[0058] In various implementations, components of the control unit 132 (such as the electronic relay and associated circuitry) and the temperature sensor 144 are integrated into a single printed circuit board, and components of the control unit 134 (such as the electronic relay and associated circuitry) and the temperature sensor 146 are integrated into a single printed circuit board. In some examples, the controller 402 may be connected to, and receive a signal from, a current sensor. For example, the controller 402 may be connected to the current sensor via a node 404 (labeled CS in FIG. 4). In some examples, the water heater unit 102 includes an ECO switch connected in series ahead of the controller 402, disconnecting the controller 402 from electrical power in response to the tank temperature exceeding the preset limit, which prevents heating elements 124 and 126 from being powered on.

[0059] FIG. 5 is a schematic diagram 500 showing additional details of the junction box 140 and the junction box 142, according to some embodiments. The example of FIG. 5 may be similar to the example of FIG. 2 except that the wiring from the electrical circuit powering the system 100 (e.g., the wire 218, wire 220, and ground wire 222) are connected to the junction box 140, and the junction box 142 is connected to the junction box 140. In the example of FIG. 5, each terminal block includes two terminal block poles. For instance, the terminal block 202 includes the terminal block pole 206 and the terminal block pole 208, while the terminal block 204 includes the terminal block pole 212 and the terminal block pole 214.

[0060] In the example of FIG. 5, the wire 218 may be connected to the terminal block pole 212, the wire 220 may be connected to the terminal block pole 214, and the ground wire 222 may be connected to the bodies of the junction boxes 140 and 142. Thus, node 234 may be connected to the wire 218 via the terminal block pole 212, and node 236 may be connected to the wire 220 via the terminal block pole 214. The terminal block pole 206 may be connected to the terminal block pole 212 via a wire 502, and the terminal block pole 208 may be connected to the terminal block pole 214 via a wire 504. Thus, the node 228 may be connected to the wire 218 via the terminal block pole 206, the terminal block pole 212, and the wire 502. Furthermore, node 230 may be connected to the wire 220 via the terminal block pole 208, the terminal block pole 214, and the wire 504. In various implementations, the current sensor 406 is positioned to detect or sense a current passing through the wire 502. Thus, the current sensor 406 may provide a sensor signal indicative of current being conducted along the wire 502. Current being conducted along the wire 502 may indicate that a downstream, lower-priority water heater unit (such as water heater unit 102) is in a heating mode (e.g., at least one of the heating elements are operating). In various implementations, the current sensor 406 is positioned within the junction box 140. The current sensor 406 may connect to other components of the system 100 (such as the controller 402) via the node 404.

[0061] FIG. 5A is a schematic diagram 501 showing additional details of the junction box 140 and the junction box 142, according to some embodiments. The example of FIG. 5A may be similar to the example of FIG. 5 except that the terminal block 204 includes three poles (e.g., terminal block pole 212, terminal block pole 214, and terminal block pole 216). The wire 218 may be connected to the terminal block pole 212, the wire 220 may be connected to the terminal block pole 214, and the ground wire 222 may be connected to the bodies of the junction boxes 140 and 142. Thus, node 234 may be connected to the wire 218 via the terminal block pole 212, and node 236 may be connected to the wire 220 via the terminal block pole 214. The terminal block pole 216 may be connected to the terminal block pole 212 via a wire 506 and connected to the terminal block pole 206 via the wire 502. The terminal block pole 208 may be connected to the terminal block pole 214 via the wire 504. Thus, node 228 may be connected to the wire 218 via the terminal block pole 206, the wire 502, the terminal block pole 216, the wire 506, and the terminal block pole 212. Furthermore, node 230 may be connected to the wire 220 via the terminal block pole 208, the wire 504, and the terminal block pole 214. The current sensor 406 may be positioned to sense a current through the wire 506 and provide a sensor signal indicative of current being conducted along the wire 506.

[0062] In some embodiments, the junction box 142 can additionally include a third terminal block pole and a current sensor that can be electrically wired to the terminal block pole 206 (such as, for example, a terminal block pole analogous to the terminal block pole 216 and a current sensor analogous to the current sensor 406 of the junction box 140). Such a design allows for the water heater units 102 and 104 and/or the junction boxes 140 and 142 to have a similar or identical construction, which allows them to be interchangeable, and further allows for additional water heater units to be connected to the water heating system 100 in a similar fashion.

[0063] FIGS. 6 and 7 are flowcharts illustrating an example process 600 for controlling operation of the water heating system 100, according to some embodiments. Although the example process 600 is described with reference to the controller 402 of the water heater unit 102, the example process 600 may be implemented at any controller of any water heater unit in the system 100, such as the analogous controller of the water heater unit 104. In the example process 600, the controller 402 monitors the current sensor signal from the current sensor 406 (block 602). Since the current sensor signal may indicate whether any heating elements at higher-priority water heater units are powered on, in implementations where the controller is at the highest-priority water heater unit (such as at the water heater unit 104), block 602 may be optionally omitted.

[0064] In the example process 600, the controller 402 monitors the temperature signal (T1) from the temperature sensor 144 associated with the higher-priority heating element 124 (at block 604). In the example process 600, the controller 402 monitors the temperature signal (T2) from the temperature sensor 146 associate with the lower-priority heating element 126 (at block 606). In the example process 600, the controller 402 determines whether the current sensor signal exceeds a threshold (at decision block 608). The current sensor signal exceeding the threshold may indicate that a higher-priority heating element at a higher-priority water heater unit (e.g., the heating element 128 or the heating element 130 of the water heater unit 104) is powered on, and that the heating elements controlled by the controller 402 should not be powered on. In some examples, the threshold is set to a level that allows for operation of the controllers of higher-priority water heater units (e.g., water heater unit 104) but not any heating elements. Thus, in various implementations where the controller is a the highest-priority water heater unit (such as the water heater unit 104), decision block 608 may be optionally omitted, and the process 600 proceeds directly from block 606 to decision block 610.

[0065] In response to determining that the current sensor signal is above the threshold (YES at decision block 608), the controller 402 does not allow the control units 132 and 134 to close their relays, preventing the heating elements 124 and 126 from powering on (at block 612), and the controller 402 continues monitoring the current sensor signal (at block 602), the temperature signal (T1) (at block 604), and the temperature signal (T2) (at block 606). In response to determining that the current sensor signal is not above the threshold (NO at decision block 608), the controller 402 determines whether the temperature signal (T1) is below a threshold (at decision block 610). Determining that the temperature signal (T1) is below the threshold may indicate that water in the tank 110 needs heating.

[0066] In response to determining that the temperature signal (T1) is below the threshold (YES at decision block 610), the controller 402 sends a signal to the lower-priority control unit 134 to open its relay, which ensures that the lower-priority heating element 126 is powered off (at block 614). In the example process 600, the controller 402 sends a signal to the higher-priority control unit 132 associated with the temperature signal (T1) to close its relay, which powers the higher-priority heating element 124 on (at block 616). The controller 402 continues monitoring the current sensor signal (at block 602), the temperature signal (T1) (at block 604), and the temperature signal (T2) (at block 606). In response to determining that the temperature signal (T1) is not below the threshold (NO at decision block 610), the controller 402 sends a signal to the control unit 132 to open its relay, which powers the heating element 124 off (at block 618).

[0067] In the example process 600, the controller 402 determines whether the temperature signal (T2) is below the threshold (at decision block 620). Determining that the temperature signal (T2) is below the threshold may indicate that water in the tank 110 needs heating. In response to determining that the temperature signal (T2) is not below the threshold (NO at decision block 620), the controller 402 sends a signal to the lower-priority control unit 134 associated with the temperature signal (T2) to open its relay, which powers the lower-priority heating element 126 off (at block 622). The controller 402 continues monitoring the current sensor signal (at block 602), the temperature signal (T1) (at block 604), and the temperature signal (T2) (at block 606).

[0068] In response to determining that the temperature signal (T2) is below the threshold (YES at decision block 620), the controller 402 determines whether all higher-priority relays are open (at decision block 624). All higher-priority relays (such as the relay of the control unit 132) being open may indicate that no higher-priority heating elements (such as heating element 124) are powered on. In response to determining that all higher-priority relays are not open (NO at decision block 624), the controller 402 sends a signal to the control unit 134 to open its relay, disconnecting the heating element 126 from power (at block 626). The controller 402 continues monitoring the current sensor signal (at block 602), the temperature signal (T1) (at block 604), and the temperature signal (T2) (at block 606).

[0069] In response to determining that all higher-priority relays are open (YES at decision block 624), the controller 402 sends a signal to the control unit 134 to close its relay, connecting the heating element 126 to power (at block 628). The controller 402 continues monitoring the current sensor signal (at block 602), the temperature signal (T1) (at block 604), and the temperature signal (T2) (at block 606). Thus, as in the example of FIGS. 4-6, the controller 402 and the analogous controller of the water heater unit 104 collectively operate the heating elements 124-130 according to a priority order, with each control unit powering on a respective heating element only when (i) any higher-priority heating elements are not powered on and (ii) the temperature sensed at the control unit is less than or equal to the threshold. In the example of FIGS. 4-6, the priority order for the heating elements is (in order from the highest priority to the lowest priority) heating element 128, heating element 130, heating element 124, followed by heating element 126.

[0070] FIG. 8 is a schematic diagram 800 showing additional details of the water heating system 100, according to some embodiments. In the example of FIG. 8, the water heater units of the water heating system 100 are implemented with microprocessor-based controllers, similar to the example of FIGS. 4-7. As in the example of FIGS. 4-7, the water heater unit 102 includes the controller 402 and the water heater unit 104 includes a controller 802. The example of FIG. 8 may be similar to the example of FIG. 4 except that the controller 402 is not connected to the current sensor 406 and that the controller 402 is connected to and receives power from a node 804 (labeled C in FIG. 8) and node 236. Additionally, the controller 802 may be connected to and receive power from nodes 228 and 230 and may be connected to and provide a signal to a node 806 (labeled R in FIG. 8).

[0071] FIG. 9 is a schematic diagram 900 showing additional details of the junction box 140 and the junction box 142, according to some embodiments. The example of FIG. 9 may be similar to the example of FIG. 2 except that in the example of FIG. 9, wires 224 and 226 are omitted and wire 902 connects the terminal block pole 206 to the terminal block pole 212, wire 904 connects the terminal block pole 210 to the terminal block pole 214, and wire 906 connects the terminal block pole 208 to the terminal block pole 216. Furthermore, in the example of FIG. 9, on the load side, the terminal block pole 210 does not include the node 232. Instead, the junction box 142 may include a switch or current interrupt device such as relay 908. In various implementations, the relay 908 is an electronic relay.

[0072] A first pole of the relay 908 may be connected to the load side of the terminal block pole 206 and a second pole of the relay 908 may be connected to the load side of the terminal block pole 210. The relay 908 may be connected to the node 806 and open or close (e.g., to disconnect or connect the load sides of the terminal block poles 206 and 210) based an electronic signal received from the node 806 (e.g., from the controller 802). When the relay 908 is in the open position, the circuit between nodes 234 and 236 is broken, and the heating elements 124 and 126 cannot receive electrical power. When the relay 908 is in the closed position, the circuit between nodes 234 and 236 is completed, and the heating elements 124 and 126 receive electrical power. In the example of FIG. 9, node 234 is at or connected to the load side of the terminal block pole 214 instead of the terminal block pole 212, and node 236 is at or connected to the load side of the terminal block pole 216 instead of the terminal block pole 214. Additionally, in the example of FIG. 9, node 804 is at or connected to the load side of the terminal block pole 212.

[0073] FIGS. 10 and 11 are flowcharts illustrating an example process 1000 for controlling operation of the water heating system 100, according to some embodiments. Although the example process 1000 is described with reference to the controller 802 of the water heater unit 104, the example process 1000 may be implemented at any controller of any water heater unit in the system 100, such as the controller 402 of the water heater unit 102.

[0074] In the example process 1000, the controller 802 monitors the temperature signal (T1) from the temperature sensor 148 associated with the higher-priority heating element 128 (at block 1002). In the example process 1000, the controller 802 monitors the temperature signal (T2) from the temperature sensor 150 associated with the lower-priority heating element 130 (at block 1004). In the example process 1000, the controller 802 determines whether the temperature signal (T1) is below a threshold (at decision block 1006). Determining that the temperature signal (T1) is below the threshold may indicate that water in the tank 112 near the temperature sensor 148 needs heating, while determining that the temperature signal (T1) is not below the threshold may indicate that water in the tank 112 near the temperature sensor 148 does not need heating. In response to determining that the temperature signal (T1) is below the threshold (YES at decision block 1006), the controller 802 sends a signal to the lower-priority control unit 138 to open its relay, which ensures that the lower-priority heating element 130 is powered off (at block 1008).

[0075] In the example process 1000, the controller 802 sends a signal to open the relay 908 at the junction box 142 associated with the water heater unit 104 (at block 1010). Opening the relay 908 may disconnect the heating elements of any downstream, lower-priority water heater units (such as the heating elements 124 and 126 of the water heater unit 102) from electrical power irrespective of whether the relays of the control units associated with the respective heating elements are closed, which may prevent an overcurrent condition when the heating elements 128 and/or 130 are powered on. In the example process 1000, the controller 802 sends a signal to the higher-priority control unit 136 associated with the temperature signal (T1) to close its relay (at block 1012), which powers the higher-priority heating element 128 on, and the controller 802 continues monitoring the temperature signal (T1) from the temperature sensor 148 (at block 1002).

[0076] In response to determining that the temperature signal (T1) is not below the threshold (NO at decision block 1006), the controller 802 sends a signal to the higher-priority control unit 136 to open its relay (at block 1014), which disconnects the higher-priority heating element 128 from electrical power. In the example process 1000, the controller 802 determines whether the temperature signal (T2) is below the threshold (at decision block 1016). Determining that the temperature signal (T2) is below the threshold may indicate that water in the tank 112 near the temperature sensor 150 needs heating, while determining that the temperature signal (T2) is not below the threshold may indicate that water in the tank 112 near the temperature sensor 150 does not need heating.

[0077] In response to determining that the temperature signal (T2) is below the threshold (YES at decision block 1016), the controller 802 sends a signal to open the relay 908 at the junction box 142 (at block 1018). In the example process 1000, the controller 802 sends a signal to the lower-priority control unit 138 associated with the temperature signal (T2) to close its relay (at block 1020), which powers the lower-priority heating element 130 on, and the controller 802 continues monitoring the temperature signal (T1) from the temperature sensor 148 (at block 1002). In response to determining that the temperature signal (T2) is not below the threshold (NO at decision block 1016), the controller 802 sends a signal to the lower-priority control unit 138 associated with the temperature signal (T2) to open its relay (at block 1022), which disconnects the lower-priority heating element 130 from electrical power. In the example process 1000, the controller 802 sends a signal to close the relay 908 at the junction box 142 (at block 1024), which may allow downstream heating elements to be connected to electrical power, and the controller 802 continues monitoring the temperature signal (T1) from the temperature sensor 148 (at block 1002).

[0078] When the process 1000 is implemented at a controller for a water heater unit that does not have any lower-priority water heater units (such as at the controller 402 of the water heater unit 102), the system 100 does not include any heating elements having a lower priority than those at the water heater unit. Accordingly, the respective junction box may not include a relay connecting it to lower-priority junction boxes and the controller does not need to be programmed to open the relay. Thus, in such embodiments, blocks 1010, 1018, and/or 1024 may optionally be removed.

[0079] When the example process 1000 is implemented at controllers of the water heating system 100 (such as controllers 802 and 402), the controllers collectively operate the heating elements 124-130 according to a priority order, with each control unit powering on a respective heating element only when (i) any higher-priority heating elements are not powered on and (ii) the temperature sensed at the control unit is less than or equal to the threshold. In the example of FIGS. 8-11, the priority order for the heating elements is (in order from the highest priority to the lowest priority) heating element 128, heating element 130, heating element 124, following by heating element 126.

[0080] FIG. 12 is a schematic diagram 1200 showing additional details of the water heating system 100, according to some embodiments. The example of FIG. 12 is similar to the example of FIG. 8 except that the nodes 804 and 806 are omitted. Accordingly, the controller 402 is connected to and powered by the nodes 234 and 236. Additionally, the controller 402 may be in communication with the controller 802. In various implementations, the controller 402 and the controller 802 are in communication via low-voltage wiring extending between the two controllers. In some examples, the controller 402 and the controller 802 may be in communication via one or more wired or wireless networks, such as an optical network, a local area network, and/or a global communication network, such as the Internet.

[0081] In various implementations, the one or more networks include a General Packet Radio Service (GPRS) network, a Time-Division Multiple Access (TDMA) network, a Code-Division Multiple Access (CDMA) network, a Global System of Mobile Communications (GSM) network, an Enhanced Data Rates for GSM Evolution (EDGE) network, a High-Speed Packet Access (HSPA) network, an Evolved High-Speed Packet Access (HSPA+) network, a Long Term Evolution (LTE) network, a Worldwide Interoperability for Microwave Access (WiMAX) network, a 5th-generation mobile network (5G), an Internet Protocol (IP) network, a Wireless Application Protocol (WAP) network, or an IEEE 802.11 standards network, as well as any suitable combination of the above networks.

[0082] FIG. 13 is a schematic diagram 1300 showing additional details of the junction box 140 and the junction box 142, according to some embodiments. The example of FIG. 13 is similar to the example of FIG. 2 except that the terminal block poles 210 and 216, node 232, and wires 224 and 226 are omitted. Instead, in the example of FIG. 13, the terminal block pole 208 is connected to the terminal block pole 212 via a wire 1302, and the terminal block pole 206 is connected to the terminal block pole 214 via a wire 1304. In the example of FIGS. 12 and 13, the controller 402 of the lower-priority water heater unit 102 can be configured to be in an off condition in which it will not power any heating element of the water heater unit 102. The controller 402 exits the off condition in response to receiving an enabling signal from the controller 802 of the higher-priority water heater unit 104. The controller 802 may send the enabling signal only when none of the heating elements of the higher-priority water heater unit 104 are powered on.

[0083] In various implementations, the controllers may send additional informationsuch as the temperature signals (T1) and (T2)to other controllers in the system 100. Accordingly, a single one of the controllers can be configured as a master controller and can operate all heating elements in the system 100. In some examples, the water heater units of the system 100 (such as the water heater units 102 and 104) can be physically identical in construction, and the controllers (such as controllers 402 and 802) can be configured during installation as either the higher-priority controller or the lower-priority controller. In various implementations, the system 100 may include a single junction box for all water heater units instead of separate junction boxes for each water heater unit.

[0084] The foregoing description is merely illustrative in nature and does not limit the scope of the disclosure or its applications. The broad teachings of the disclosure may be implemented in many different ways. While the disclosure includes some particular examples, other modifications will become apparent upon a study of the drawings, the text of this specification, and the following claims. In the written description and the claims, one or more processes within any given method may be executed in a different order-or processes may be executed concurrently or in combination with each other-without altering the principles of this disclosure. Similarly, instructions stored in a non-transitory computer-readable medium may be executed in a different order-or concurrently-without altering the principles of this disclosure. Unless otherwise indicated, the numbering or other labeling of instructions or method steps is done for convenient reference and does not necessarily indicate a fixed sequencing or ordering.

[0085] It should also be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized in various implementations. Aspects, features, and instances may include hardware, software, and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one instance, the electronic based aspects of the invention may be implemented in software (for example, stored on non-transitory computer-readable medium) executable by one or more processors. As a consequence, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the invention. For example, control units and controllers described in the specification can include one or more electronic processors, one or more memories including a non-transitory computer-readable medium, one or more input/output interfaces, and various connections (for example, a system bus) connecting the components.

[0086] Unless the context of their usage unambiguously indicates otherwise, the articles a, an, and the should not be interpreted to mean only one. Rather, these articles should be interpreted to mean at least one or one or more. Likewise, when the terms the or said are used to refer to a noun previously introduced by the indefinite article a or an, the terms the or said should similarly be interpreted to mean at least one or one or more unless the context of their usage unambiguously indicates otherwise.

[0087] It should also be understood that although certain drawings illustrate hardware and software located within particular devices, these depictions are for illustrative purposes only. In some embodiments, the illustrated components may be combined or divided into separate software, firmware, and/or hardware. For example, instead of being located within and performed by a single electronic processor, logic and processing may be distributed among multiple electronic processors. Regardless of how they are combined or divided, hardware and software components may be located on the same computing device or may be distributed among different computing devices connected by one or more networks or other suitable connections or links.

[0088] Thus, in the claims, if an apparatus or system is claimed, for example, as including an electronic processor or other element configured in a certain manner, for example, to make multiple determinations, the claim or claim element should be interpreted as meaning one or more electronic processors (or other element) where any one of the one or more electronic processors (or other element) is configured as claimed, for example, to make some or all of the multiple determinations collectively. To reiterate, those electronic processors and processing may be distributed.

[0089] Spatial and functional relationships between elements-such as modules-are described using terms such as (but not limited to) connected, engaged, interfaced, and/or coupled. Unless explicitly described as being direct, relationships between elements may be direct or include intervening elements. The phrase at least one of A, B, and C should be construed to indicate a logical relationship (A OR B OR C), where OR is a non-exclusive logical OR, and should not be construed to mean at least one of A, at least one of B, and at least one of C. The term set does not necessarily exclude the empty set. For example, the term set may have zero elements. The term subset does not necessarily require a proper subset. For example, a subset of set A may be coextensive with set A, or include elements of set A. Furthermore, the term subset does not necessarily exclude the empty set.

[0090] In the figures, the directions of arrows generally demonstrate the flow of informationsuch as data or instructions. The direction of an arrow does not imply that information is not being transmitted in the reverse direction. For example, when information is sent from a first element to a second element, the arrow may point from the first element to the second element. However, the second element may send requests for data to the first element, and/or acknowledgements of receipt of information to the first element. Furthermore, while the figures illustrate a number of components and/or steps, any one or more of the components and/or steps may be omitted or duplicated, as suitable for the application and setting.

[0091] Additionally, operations (such as processes, decisions, inputs, outputs, actions, messages, interactions, events, and/or any other operations) shown in the flowcharts and/or message sequence charts may be illustrated once each and in a particular order in the drawings. However, in various implementations, the operations may be reordered and/or repeated as may be suitable. In some examples, different operations may be performed in parallel, as may be appropriate.

[0092] The term computer-readable medium does not encompass transitory electrical or electromagnetic signals or electromagnetic signals propagating through a medium-such as on an electromagnetic carrier wave. The term computer-readable medium is considered tangible and non-transitory. The functional blocks, flowchart elements, and message sequence charts described above serve as software specifications that can be translated into computer programs by the routine work of a skilled technician or programmer.