REHEAT SCHEDULING FOR WATER HEATERS

Abstract

A method of controlling an electric tank-style water heater having at least an upper heating element and a lower heating element is provided. Operating electricity is denied to at least the lower heating element at an initial scheduled shutdown time according to an initial control protocol. Then, supply of the operating electricity to at least the lower heating element is resumed at an initial scheduled restart time according to the initial control protocol. Recovery activation time of the water heater following the resumption of the supply of the operating electricity is monitored. Responsive to a function of the recovery activation time of the water heater exceeding an upper threshold, the initial control protocol is adjusted to obtain a first adjusted control protocol to reduce the recovery activation time. An electric tank-style water heater and a control module therefor are also described.

Claims

1. A method of controlling an electric tank-style water heater having at least an upper heating element and a lower heating element, the method comprising: denying operating electricity to at least the lower heating element at an initial scheduled shutdown time according to an initial control protocol; resuming supply of the operating electricity to at least the lower heating element at an initial scheduled restart time according to the initial control protocol; monitoring a recovery activation time of the water heater following the resumption of the supply of the operating electricity; and responsive to a function of the recovery activation time of the water heater exceeding an upper threshold, adjusting the initial control protocol to obtain a first adjusted control protocol to reduce the recovery activation time.

2. The method of claim 1, wherein: the operating electricity is at least selectively permitted to reach at least the upper heating element; the method further comprising: monitoring a top-up activation time of the water heater between the initial scheduled shutdown time and the initial scheduled restart time; wherein the function of the recovery activation time of the water heater incorporates the top-up activation time of the water heater.

3. The method of claim 1, wherein adjusting the initial control protocol to obtain the first adjusted control protocol comprises at least one of: adjusting the initial scheduled shutdown time to become an adjusted scheduled shutdown time that is later than the initial scheduled shutdown time; adjusting the initial scheduled restart time to become an adjusted scheduled restart time that is earlier than the initial scheduled restart time; and allowing activation of at least one of the upper heating element and the lower heating element between the adjusted scheduled shutdown time and the adjusted scheduled restart time.

4. The method of claim 1, further comprising, responsive to the function of the recovery activation time of the water heater failing to exceed a lower threshold, adjusting the initial control protocol to obtain a second adjusted control protocol to increase the recovery activation time.

5. The method of claim 4, wherein adjusting the initial control protocol to obtain the second adjusted control protocol comprises at least one of: adjusting the initial scheduled shutdown time to become an adjusted scheduled shutdown time that is earlier than the initial shutdown time; and adjusting the initial scheduled restart time to become an adjusted scheduled restart time that is later than the initial scheduled restart time.

6. The method of claim 1, wherein monitoring the recovery activation time of the water heater following the resumption of the supply of the operating electricity occurs over multiple days.

7. The method of claim 1, wherein: the operating electricity is denied to both the upper heating element and the lower heating element at the initial scheduled shutdown time; and the supply of the operating electricity is resumed to both the upper heating element and the lower heating element at the initial scheduled restart time; the method further comprising: between the initial scheduled shutdown time and the initial scheduled restart time, monitoring for closure of an upper thermostat governing the upper heating element; and responsive to at least detecting closure of the upper thermostat, supplying the operating electricity to at least the upper heating element before the initial scheduled restart time.

8. The method of claim 1, wherein denying the operating electricity to at least the lower heating element at the initial scheduled shutdown time according to the initial control protocol comprises denying operating electricity only to the lower heating element.

9. An electric tank-style water heater, comprising: a tank, the tank having: a water inlet for receiving cooler water into the tank; and a water outlet for releasing heated water from the tank; a lower heating element protruding into the tank; a lower thermostat governing supply of electrical power to the lower heating element; an upper heating element protruding into the tank; an upper thermostat governing supply of electrical power to the upper heating element; an electrical junction, wherein: the electrical junction is in electrical communication with the upper heating element through the upper thermostat; the electrical junction is in electrical communication with the lower heating element through the lower thermostat; and wherein the water heater comprises a control module configured to: cause the water heater to: deny operating electricity to at least the lower heating element at an initial scheduled shutdown time according to an initial control protocol; and resume supply of the operating electricity to at least the lower heating element at an initial scheduled restart time according to the initial control protocol; and monitor a recovery activation time of the water heater following resumption of the supply of the operating electricity; and responsive to a function of the recovery activation time of the water heater exceeding an upper threshold, cause the water heater to operate according to a first adjusted control protocol adapted to reduce the recovery activation time.

10. The water heater of claim 8, wherein the control module is configured to: cause the water heater to at least selectively permit the operating electricity to reach at least the upper heating element; and monitor a top-up activation time of the water heater between the initial scheduled shutdown time and the initial scheduled restart time; wherein the function of the recovery activation time of the water heater incorporates the top-up activation time of the water heater.

11. The water heater of claim 9, wherein the first adjusted control protocol comprises at least one of: an adjusted scheduled shutdown time that is later than the initial scheduled shutdown time; an adjusted scheduled restart time that is earlier than the initial scheduled restart time; and allowing activation of at least one of the upper heating element and the lower heating element between the adjusted scheduled shutdown time and the adjusted scheduled restart time.

12. The water heater of claim 9, wherein the control module is further configured to, responsive to the function of the recovery activation time of the water heater failing to exceed a lower threshold, cause the water heater to operate according to a second adjusted control protocol to increase the recovery activation time.

13. The water heater of claim 12, wherein the second adjusted control protocol comprises at least one of: an adjusted scheduled shutdown time that is earlier than the initial shutdown time; and an adjusted scheduled restart time that is later than the initial scheduled restart time.

14. The water heater of claim 9, wherein the control module is configured to monitor the recovery activation time of the water heater following the resumption of the supply of the operating electricity over multiple days.

15. The water heater of claim 9, wherein: the control module causes the water heater to: deny the operating electricity to both the upper heating element and the lower heating element at the initial scheduled shutdown time; and resume the supply of the operating electricity to both the upper heating element and the lower heating element at the initial scheduled restart time; and the control module is configured to: between the initial scheduled shutdown time and the initial scheduled restart time, monitor for closure of an upper thermostat governing the upper heating element; and responsive to at least detecting closure of the upper thermostat, cause the water heater to supply the operating electricity to at least the upper heating element before the initial scheduled restart time.

16. The water heater of claim 9, wherein the control module causes the water heater to deny the operating electricity only to the lower heating element.

17. A control module adapted to be coupled to an electric tank-style water heater having at least an upper heating element and a lower heating element, wherein: the control module is configured to cause the water heater to: deny operating electricity to at least the lower heating element at an initial scheduled shutdown time according to an initial control protocol; and resume supply of the operating electricity to at least the lower heating element at an initial scheduled restart time according to the initial control protocol; and the control module is configured to monitor a recovery activation time of the water heater following resumption of the supply of the operating electricity; and the control module is configured to, responsive to a function of the recovery activation time of the water heater exceeding an upper threshold, further cause the water heater to operate according to a first adjusted control protocol adapted to reduce the recovery activation time.

18. The control module of claim 17, wherein the control module is configured to: cause the water heater to at least selectively permit the operating electricity to reach at least the upper heating element; and monitor a top-up activation time of the water heater between the initial scheduled shutdown time and the initial scheduled restart time; and wherein the function of the recovery activation time of the water heater incorporates the top-up activation time of the water heater.

19. The control module of claim 17, wherein the first adjusted control protocol comprises at least one of: an adjusted scheduled shutdown time that is later than the initial scheduled shutdown time; an adjusted scheduled restart time that is earlier than the initial scheduled restart time; and allowing activation of at least one of the upper heating element and the lower heating element between the adjusted scheduled shutdown time and the adjusted scheduled restart time.

20. The control module of claim 17, wherein the control module is further configured to, responsive to the function of the recovery activation time of the water heater failing to exceed the lower threshold, cause the water heater to operate according to a second adjusted control protocol to increase the recovery activation time.

21. The control module of claim 20, wherein the second adjusted control protocol comprises at least one of: an adjusted scheduled shutdown time that is earlier than the initial shutdown time; and an adjusted scheduled restart time that is later than the initial scheduled restart time.

22. The control module of claim 17, wherein the control module is configured to monitor the recovery activation time of the water heater following the resumption of the supply of the operating electricity over multiple days.

23. The control module of claim 17, wherein the control module is configured to: cause the water heater to: deny the operating electricity to both the upper heating element and the lower heating element at the initial scheduled shutdown time; and resume the supply of the operating electricity to both the upper heating element and the lower heating element at the initial scheduled restart time; between the initial scheduled shutdown time and the initial scheduled restart time, monitor for closure of an upper thermostat governing the upper heating element; and responsive to at least detecting closure of the upper thermostat, cause the water heater to supply the operating electricity to at least the upper heating element before the initial scheduled restart time.

24. The control module of claim 17, wherein the control module is configured to cause the water heater to deny the operating electricity only to the lower heating element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other features will become more apparent from the following description in which reference is made to the appended drawings wherein:

[0019] FIG. 1 is a block diagram showing a first illustrative tank-style electric water heater with a controller according to an aspect of the present disclosure;

[0020] FIG. 1A shows an illustrative tank-style electric water heater according to an aspect of the present disclosure having a first interrupt switch disposed in a lower aperture thereof;

[0021] FIG. 1B shows an illustrative tank-style electric water heater according to an aspect of the present disclosure having a first interrupt switch disposed in an upper aperture thereof;

[0022] FIG. 1C shows an illustrative tank-style electric water heater according to an aspect of the present disclosure having a first interrupt switch disposed in a lower aperture thereof and having a second interrupt switch disposed in an upper aperture thereof;

[0023] FIG. 2A shows a wiring schematic for a first embodiment of a tank-style electric water heater according to an aspect of the present disclosure;

[0024] FIG. 2B shows a wiring schematic for a second embodiment of a tank-style electric water heater according to an aspect of the present disclosure;

[0025] FIG. 2C shows a wiring schematic for a third embodiment of a tank-style electric water heater according to an aspect of the present disclosure;

[0026] FIG. 2D shows a wiring schematic for a fourth embodiment of a tank-style electric water heater according to an aspect of the present disclosure;

[0027] FIG. 2E shows a wiring schematic for a fifth embodiment of a tank-style electric water heater according to an aspect of the present disclosure;

[0028] FIG. 2F shows a wiring schematic for a sixth embodiment of a tank-style electric water heater according to an aspect of the present disclosure;

[0029] FIG. 3 is a block diagram showing components of an illustrative embodiment of a first interrupt switch according to an aspect of the present disclosure;

[0030] FIG. 4 is a flow chart showing an illustrative method for retrofitting an electric tank-style water heater;

[0031] FIG. 5 is a flow chart showing an illustrative method for implementing aspects of the method shown in FIG. 4;

[0032] FIG. 6 is a block diagram showing a second illustrative tank-style electric water heater with a controller according to an aspect of the present disclosure; and

[0033] FIG. 7 is a flow chart showing a method of controlling an electric tank-style water heater having at least an upper heating element and a lower heating element, according to an aspect of the present disclosure.

DETAILED DESCRIPTION

[0034] Reference is now made to FIG. 1, which shows an illustrative tank-style electric water heater 100. The water heater 100 comprises a tank 101 and includes a lower heating element 102 protruding into the tank 101, a lower thermostat 104, an upper heating element 106 protruding into the tank 101, an upper thermostat 108, and an electrical junction 110. For clarity, the terms lower and upper refer to the physical position of the heating elements and thermostats when the water heater 100 is upright, and not to temperature values. The electrical junction 110 is coupled in electrical communication with an electrical power supply 112, for example 220V AC, via a relay circuit 128. Electrical power to the lower heating element 102 and the upper heating element 106 from the junction 110 is governed by the respective thermostats 104, 108. Thus, the electrical junction 110 is in electrical communication with the upper heating element 106 through the upper thermostat 108 and the electrical junction 110 is in electrical communication with the lower heating element 102 through the lower thermostat 104. A high limit control switch (see FIGS. 2A through 2F) is also provided to prevent overheating. The lower thermostat 104 and the upper thermostat 108 are typically robust thermo-mechanical thermostats, such as adjustable mechanical snap-disk thermostats that physically change the position of an electrical switch when a set temperature is reached, although any suitable temperature-driven temperature limit switches may be used and are included within the meaning of the term thermostat as used herein. Other components of the water heater 100 are known to those of skill in the art and are omitted for simplicity of illustration.

[0035] The water heater 100 has a water inlet 114 for receiving cooler water into the tank 101, for example from a municipal water supply, a water outlet 116 for releasing heated water from the tank 101, and may include a mixing valve 118 for mixing the cooler water with the heated water to achieve a more comfortable temperature.

[0036] As can be seen, cooler water entering the water inlet 114 is deposited near the bottom of the tank 101, while the water outlet 116 draws heated water from near the top of the tank 101. For most electrical tank-style water heaters, almost all reheating is done by the lower heating element 102 and the upper heating element 106 is activated only during a period of high usage where the temperature in the upper portion of the tank 101 degrades below the setpoint of the upper thermostat 108. Within the control circuitry of the water heater 100, the upper thermostat 108 has priority: if both thermostats are closed, only the upper heating element 106 is activated; the lower heating element 102 is activated only if the lower thermostat 104 is closed and the upper thermostat 108 is open. More particularly, the upper thermostat 108 also functions as a switch in a relay circuit to the lower heating element 102 and the lower thermostat 104. When the upper thermostat 108 is closed to permit current to reach the upper heating element 106, the upper thermostat 108 will simultaneously obstruct current from reaching the lower heating element 102 and the lower thermostat 104. Conversely, when the upper thermostat 108 is open, it will obstruct current from reaching the upper heating element 106 and permit current to reach the lower heating element 102 and the lower thermostat 104. Thus, if the upper thermostat 108 closes because the surrounding water temperature falls below its setpoint, the upper heating element 106 is activated and remains activated (energized) until the setpoint temperature is reached, with the lower heating element 102 remaining deactivated even if the lower thermostat 108 is also closed, because the relay circuit is open. Once the setpoint temperature is reached for the water in the upper portion of the tank 101 and the upper thermostat 108 opens, this activates the relay circuit and heating continues with the lower heating element 102 so long as the lower thermostat 104 is closed. Note that where the thermostat 104, 108 are thermomechanical thermostat devices, hysteresis effects will mean that the temperature will need to drop several degrees below the setpoint to trigger reheating.

[0037] The water heater 100 operates according to a control protocol. The control protocol will provide a scheduled shutdown time for the water heater 100, and a scheduled restart time for the water heater 100, with the scheduled restart time being later than the scheduled shutdown time and may be used to achieve load shifting. Operating electricity is denied to at least the lower heating element 102 at the scheduled shutdown time according to the control protocol, and supply of the operating electricity to at least the lower heating element 102 is resumed at the scheduled restart time according to the control protocol. The term operating electricity, as used herein, refers to electricity of sufficient voltage and sufficient duration to appreciably raise the temperature of water contained within the tank 101.

[0038] The control protocol may be based on one or more factors, including household considerations and/or utility considerations. Household considerations may include the size of the tank 101, the heating capacity of the upper heating element 106 and the lower heating element 102 (which may vary depending on tank size and manufacturer), historic factors such as the day of the week and/or hot water use over the past X days, current day consumption (kWh may be used as a proxy) the time of year (which affects incoming water temperature and consumption), and household preferences (e.g. comfort, cost and CO.sub.2 reduction). Utility considerations may include rate plan, CO.sub.2 content of generated power, overall load vs. peak capacity, and local distribution bottlenecks.

[0039] In some embodiments, an initial control protocol may be based entirely on one or more household considerations. In other embodiments, an initial control protocol may be based entirely on one or more utility considerations. In yet other embodiments, both household considerations and utility considerations may affect the initial control protocol. The initial control protocol may be set manually, or may be automatically generated based on one or more of the aforementioned factors.

[0040] For example, an initial control protocol may set the initial scheduled shutdown time for 7:00 a.m. and set the initial scheduled restart time for 11:00 a.m. This is merely an illustrative, non-limiting example. A control protocol may provide for more than one scheduled shutdown time and scheduled restart time within a 24-hour period.

[0041] Even with sophisticated multifactorial calculations, however, there remains a risk that the initial control protocol will be suboptimal and may result in the water in the tank 101 becoming too cool between the initial scheduled shutdown time and the initial scheduled restart time. The recovery activation time of the water heater 100 following resumption of the supply of the operating electricity at the initial scheduled restart time is monitored, and adjustments can be made to the initial control protocol to obtain an adjusted control protocol based on the monitoring. The recovery activation time is, at a minimum, the amount of time that the lower heating element 102 is activated following resumption of the supply of the operating electricity at the initial scheduled restart time before being deactivated by the lower thermostat 104. Preferably, for improved accuracy the recovery activation time reflects the amount of time that each of the upper heating element 106 and the lower heating element 102 is activated following resumption of the supply of the operating electricity at the initial scheduled restart time before being deactivated by the respective thermostats 108, 104. This may be a cumulative total time for both the upper heating element 106 and the lower heating element 102, or may be an individual time for each of the upper heating element 106 and the lower heating element 102.

[0042] In an embodiment in which operating electricity is at least selectively permitted to continue to reach at least the upper heating element 106, the top-up activation time of the water heater between the initial scheduled shutdown time and the initial scheduled restart time is also preferably monitored. In most cases, only the upper heating element 106 will be activated between the initial scheduled shutdown time and the initial scheduled restart time, although it is also contemplated that in some instances, the lower heating element 102 may also be activated between the initial scheduled shutdown time and the initial scheduled restart time. The top-up activation time is, at a minimum, the amount of time that the upper heating element 106 is activated between the initial scheduled shutdown time and the initial scheduled restart time. Preferably, for improved accuracy the top-up activation time is reflects the total amount of time that each of the upper heating element 106 and the lower heating element 102 is activated between the initial scheduled shutdown time and the initial scheduled restart time. Again, this may be a cumulative total time for both the upper heating element 106 and the lower heating element 102, or an individual time for each of the upper heating element 106 and the lower heating element 102.

[0043] The length of the recovery activation time is related to the volume and temperature of unheated water that has entered the tank 101 from the bottom between the initial scheduled shutdown time and the initial scheduled restart time, and can provide an indication of whether the initial control protocol may be jeopardizing the supply of hot water. Thus, the initial control protocol can be adjusted based on a function of the recovery activation time to obtain an adjusted control protocol. The function of the recovery activation time may be merely the recovery time itself (e.g. f(Y)=1Y), or the function of the recovery activation time may be a more sophisticated function. Preferably, in an embodiment in which the controller 134 causes the water heater 100 to at least selectively permit operating electricity to continue to reach at least the upper heating element 106 between the initial scheduled shutdown time and the initial scheduled restart time, the function of the recovery activation time of the water heater 100 incorporates the top-up activation time of the water heater 100. In a simple embodiment, a function of the recovery activation time that incorporates the top-up activation time may be the sum of the recovery activation time and the top-up activation time. More sophisticated approaches may also be used.

[0044] For example, the recovery activation time may be used to calculate the energy consumption following resumption of the supply of the operating electricity at the initial scheduled restart time (e.g. kWh) based on the characteristics of the heating element(s). Thus, the function of the recovery activation time may be a calculation of the energy consumed by the water heater 100 after the initial scheduled restart time. In an embodiment in which the controller 134 causes the water heater to at least selectively permit operating electricity to continue to reach at least the upper heating element 106 between the initial scheduled shutdown time and the initial scheduled restart time, the top-up activation time of the water heater 100 may be used to calculate the energy consumption of the water heater 100 between the initial scheduled shutdown time and the initial scheduled restart time. In such an embodiment, the function of the recovery activation time may be a calculation of the total energy consumed by the water heater 100 to top up between the initial scheduled shutdown time and the initial scheduled restart time and to recover after the initial scheduled restart time.

[0045] If the function of the recovery activation time (which may incorporate the top-up activation time) of the water heater 100 exceeds an upper threshold, the water heater 100 will operate according to a first adjusted control protocol. The upper threshold may be a variable threshold, or there may be a plurality of upper thresholds. For example, testing against the upper threshold may comprise comparing the function of the recovery activation time to a lookup table, and implementing the first adjusted control protocol according to the lookup table. Alternatively, the first adjusted control protocol may be calculated from the function of the recovery activation time. These are merely non-limiting illustrative examples. The first adjusted control protocol is adapted to reduce the recovery activation time on the next iteration of the control protocol. For example, the first adjusted control protocol may comprise an adjusted scheduled shutdown time that is later than the initial scheduled shutdown time and/or an adjusted scheduled restart time that is earlier than the initial restart time. If the initial control protocol set the initial scheduled shutdown time for 7:00 a.m. and set the initial scheduled restart time for 11:00 a.m. and the function of the recovery activation time of the water heater 100 exceeds the upper threshold, the initial scheduled shutdown time might be moved to 7:30 a.m., or the initial scheduled restart time might be moved to 10:30, or both. The foregoing is merely an example, and not limiting. The first adjusted control protocol may comprise allowing activation of at least one of the upper heating element and the lower heating element between the adjusted scheduled shutdown time and the adjusted scheduled restart time.

[0046] As noted above, the length of the recovery activation time can provide an indication of whether the initial control protocol may be jeopardizing the supply of hot water, which may indicate that the initial control protocol can actually be made more aggressive without adversely affecting the availability of hot water. Optionally, if the function of the recovery activation time of the water heater 100 fails to exceed a lower threshold, the water heater 100 can be made to operate according to a second adjusted control protocol to increase the recovery activation time. For example, the second adjusted control protocol may comprise an adjusted scheduled shutdown time that is earlier than the initial shutdown time, an adjusted scheduled restart time that is later than the initial scheduled restart time, or both. If the initial control protocol set the initial scheduled shutdown time for 7:00 a.m. and set the initial scheduled restart time for 11:00 a.m. and the function of the recovery activation time of the water heater 100 fails to exceed the upper threshold, the initial scheduled shutdown time might be moved to 6:30 a.m., or the initial scheduled restart time might be moved to 11:30, or both. Again, this is merely a non-limiting example.

[0047] The initial control protocol may be adjusted after monitoring the recovery activation time (and optionally top-up recovery time) of the water heater 100 following the resumption of the supply of the operating electricity over a single day, or over multiple days, which may be sequential or non-sequential. For example, there may be different control protocols for weekdays and for weekends and the initial control protocol for weekdays may be adjusted after monitoring a series of sequential weekdays and to adjust the initial control protocol for weekends after monitoring one or two weekend days. Alternatively, there may be a different control protocol for each day of the week. For example, Monday may have a different control protocol than Tuesday. The foregoing are merely illustrative, non-limiting examples.

[0048] The initial control protocol may be provided by a power scheduler 138, as described further below. Adjustment of the control protocol to obtain an adjusted control protocol can be carried out by any one or more of the control module 133, the controller 134 and the power scheduler 138, alone or in combination, depending on the desired configuration.

[0049] The fact that the upper thermostat 108 has priority over the lower thermostat 104 means that the upper heating element 106 has priority over the lover heating element 102. This feature can be utilized to provide additional or alternate control over reheating. Accordingly, in some preferred embodiments as shown in FIG. 1, the water heater will deny the operating electricity only to the lower heating element 102 at the scheduled shutdown time while permitting the operating electricity to reach the upper heating element 106 after the scheduled shutdown time. As noted above, in such an embodiment, the function of the recovery activation time may optionally take account of whether and for how long the upper heating element 106 was activated (top-up recovery time) between the scheduled shutdown time and the scheduled restart time.

[0050] In the illustrated embodiment shown in FIG. 1, the water heater will deny the operating electricity only to the lower heating element 102 by way of a first interrupt switch 130. The first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102. The first interrupt switch 130 may comprise, for example, an electrical relay. The first interrupt switch 130 is selectively switchable by wireless signal between an open configuration 130a and a closed configuration 130b (shown with dashed line). When the first interrupt switch is in the open configuration 130a, electrical current between the electrical junction 110 and the lower heating element 102 is obstructed by the first interrupt switch 130, even when the upper thermostat 108 is open and the lower thermostat 104 is closed. When the first interrupt switch is in the closed configuration 130b (shown with dashed line) electrical current between the electrical junction 110 and the lower heating element 102 is unobstructed by the first interrupt switch 130 when the upper thermostat 108 is open and the lower thermostat 104 is closed.

[0051] Importantly, in the embodiment shown in FIG. 1, the first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 at an electrical position for which, at least when the upper thermostat 104 is closed, electrical communication between the electrical junction 110 and the upper heating element 106 is agnostic to whether the first interrupt switch 130 is in the closed configuration 130b or the open configuration 130a. In other words, the first interrupt switch 130 is electrically positioned so that it does not prevent the upper heating element 106 from activating when the upper thermostat 108 is closed, regardless of whether the first interrupt switch 130 is in the closed configuration 130b or the open configuration 130a. Thus, the first interrupt switch 130 is not interposed between the electrical junction 110 and the upper heating element 106; indeed, in one preferred embodiment no interrupt switch is interposed between the electrical junction 110 and the upper heating element 106. In one preferred embodiment, electrical communication between the electrical junction 110 and the upper heating element 106 is governed only by the upper thermostat 108. In other embodiments described further below, a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 and a second, separate interrupt switch is interposed between the electrical junction 110 and the upper heating element 106. In still further embodiments, also described below in the context of FIG. 6, the first interrupt switch 130 is interposed between the relay circuit 128 and the electrical junction 110.

[0052] In the illustrated embodiment, the first interrupt switch 130 is electrically coupled via control circuitry 131 to a wireless unit 132. The first interrupt switch 130, control circuitry 131 and wireless unit 132 collectively form a control module 133, which is responsive to a wireless signal received by the wireless unit 132 to selectively switch the first interrupt switch 130. The first interrupt switch 130, control circuitry 131 and wireless unit 132 may be housed within a common body, or may be at various physical locations while electrically coupled to one another. The wireless unit 132 may be, for example, a Bluetooth wireless unit, a LoRaWAN wireless unit, a Wi-Fi wireless unit, or an infrared wireless unit. The controller 134 is configured to selectively send one or more wireless signals 136 to the wireless unit 132 to control the first interrupt switch 130.

[0053] Various wireless signal arrangements are contemplated. In one illustrative implementation, there may be a single type of wireless signal 136 that toggles the first interrupt switch 130; each time the wireless signal 136 is received, the first interrupt switch 130 changes its configuration. In another illustrative implementation, the wireless signal 136 is coded according to the desired configuration. Thus, if the first interrupt switch 130 is in the open configuration 130a and the wireless unit 132 receives a wireless signal coded for open, or if the first interrupt switch 130 is in the closed configuration 130b and the wireless unit 132 receives a wireless signal 136 coded for closed, no action would be taken since the first interrupt switch 130 is already in the desired configuration. However, if the first interrupt switch 130 is in the open configuration 130a and the wireless unit 132 receives a wireless signal 136 coded for closed, the first interrupt switch 130 would move to the closed configuration. Similarly, if the first interrupt switch 130 is in the closed configuration 130b and the wireless unit 132 receives a wireless signal 136 coded for open, the first interrupt switch 130 would move to the open configuration. Other wireless signal arrangements are also contemplated. Moreover, in other embodiments, the controller may have a wired connection to the first interrupt switch 130, or the controller and the first interrupt switch may be integrated into a single device or set of devices connected by wire, with or without a wireless unit for communicating with other wireless devices. For example, the controller may be preprogrammed and/or directly programmable without additional external communication, or may be wirelessly interactive with an application on a smartphone or tablet. The controller (whether alone or as part of a larger device) may be connected by wire to the current sensor(s) where present. Some functions of the controller may be performed by the control module 133.

[0054] The controller 134 may comprise a general-purpose computer, or special purpose hardware. The controller 134 may be a network-capable hardware device that is communicatively coupled to a power scheduler 138 via a network 140 such as the Internet. The power scheduler 138 may be a power utility or a third-party power scheduler, which may in turn cooperate with the power utility. The power scheduler 138 can thus send signals to the controller 134, which can in turn send wireless signals 136 to the wireless unit 132 to control the first interrupt switch 130 to control the timing of activation of the lower heating element 102 and limit such activation according to the control protocol. For example, the control protocol may limit activation to off-peak periods (or other scheduled periods, for example periods in which the electricity is generated by techniques that result in lower carbon emissions, such as daylight periods where solar generation is available). Since almost all reheating is done by the lower heating element 102, limiting activation of the lower heating element 102 to off-peak (or other scheduled) periods can have a material impact on demand, especially when applied across a multitude of water heaters.

[0055] In a preferred embodiment, the wireless unit 132 can not only receive wireless signals 136 from the controller 134, but also send wireless signals 136 to the controller 134. In such embodiments, the control module 133 may be configured to obtain data about usage of the upper heating element 106 and the lower heating element 102, which can be sent to the wireless unit 132 to be communicated back to the controller 134, and from the controller 134 to the power scheduler 138. For example, in one embodiment the control module 133 can monitor how long the lower thermostat 104 is closed, and how long the first interrupt switch 130 is in the open configuration 130a, to determine how long the lower heating element 102 is energized (e.g. to determine the recovery activation time). The control module 133 may include a step-down transformer to provide a low voltage power supply to the control module 133 from the high voltage supplied to the water heater 100 from the junction 110. The control module 133 preferably includes a battery (which may be rechargeable) to provide a power supply when no current is flowing through the first interrupt switch 130; the control module may also be connectable to an electrical outlet. Preferably, the control module 133 is electrically coupled to the upper heating element 106 to determine how long the upper heating element 106 is energized so that this information can be communicated by the wireless unit 132 to the controller 134. Circuitry can also be coupled to the control module 133 (e.g. associated with the first interrupt switch 130) to determine how long the lower heating element 102 is energized. Such circuitry is within the capability of one of ordinary skill in the art, now informed by the present disclosure, and therefore is not described further.

[0056] Moreover, the arrangement described above in the context of FIG. 1 is unlikely to materially adversely affect the availability of hot water on demand. Because the upper thermostat 108 has priority within the control circuitry of the water heater 100, and the first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102, the configuration (open or closed) of the first interrupt switch 130 will not affect operation of the upper heating element 106. Indeed, as noted above, the upper heating element 106 is agnostic to whether the first interrupt switch 130 is in the closed configuration 130b or the open configuration 130a and preferably the electrical junction 110 and the upper heating element 106 is governed only by the upper thermostat 108. Thus, during a period of high usage where the upper thermostat 108 closes because the surrounding water temperature falls below its setpoint, the upper heating element 106 is activated and remains activated (energized) until the setpoint temperature is reached, regardless of whether the first interrupt switch 130 is in the open configuration 130a or the closed configuration 130b. Accordingly, water in the upper portion of the tank 101 can be reheated to meet demand even where activation of the lower heating element 102 has been obstructed by switching the first interrupt switch 130 to the open configuration 130a.

[0057] After a certain amount of hot water has been consumed, the upper heating element 106 alone may not be able to maintain the desired water temperature without the assistance of the lower heating element 102. Where the control module 133 is configured to determine how long the upper heating element 106 is energized, the control module 133 may be further configured to refuse an instruction from the controller 134 to open the first interrupt switch 130 if doing would result in excessive degradation of the water temperature, or to close the first interrupt switch 130 even after the scheduled shutdown time. Alternately, such calculations may be made by the controller 134, which may decline to send such instructions to the wireless unit 132 in such circumstances. Thus, when necessary to maintain a satisfactory water temperature, the lower heating element 102 may be activated even if the power scheduler 138 sends signals to the controller 134 to prevent activation.

[0058] The control protocol, that is, the time periods during which (at least) the lower heating element 102 is prevented from being energized, may be determined in a number of ways. For example, the time periods may be generally fixed (subject to manual adjustment) based on known peak and off-peak periods, or may be generated dynamically based on actual power consumption across the utility's network. Moreover, although FIG. 1 shows the controller 134 and the power scheduler 138 as separate devices that communicate over the network 140, in other embodiments the controller and the power scheduler may be integrated into a single device. For example, the combined device could be programmable by a homeowner to specify the times during which the lower heating element 102 is prevented from being energized, without any external network connection, or may be preprogrammed with appropriate time periods by a power utility.

[0059] In some embodiments, a water heater can be manufactured by an original equipment manufacturer (OEM) to have the components and configuration described above. In other embodiments, an existing tank-style electric water heater can be retrofit to achieve the same functionality, as will be described in the context of FIGS. 1A through 1C. For simplicity of illustration, only some of the high voltage wiring common to all of the embodiments in FIGS. 1A, 1B and 1C is shown; illustrative electrical schematics are provided in FIGS. 2A through 2F and described below. The water inlet 114 and water outlet 116 are also omitted from FIGS. 1A to 1C for simplicity of illustration.

[0060] Reference is now made to FIG. 1A. Typically, a tank-style electric water heater 100 will include an inner tank 142 that holds the water to be heated, with an outer housing 144 surrounding the inner tank 142 and thermal insulation 146 disposed between the inner tank 142 and the outer housing 144. The outer housing 144 will usually have an upper aperture 148 providing access to the upper thermostat 108, upper heating element 106, and associated wiring. The upper aperture 148 is normally covered by a removable upper panel 150 that forms part of the outer housing 144. Similarly, the outer housing 144 will also usually have a lower aperture 152 providing access to the lower thermostat 104, lower heating element 102, and associated wiring, with the lower aperture 152 being normally covered by a removable lower panel 154 that also forms part of the outer housing 144. The panels 150, 154 provide access for technicians, and there is typically enough space inside the lower aperture 152 to accommodate the first interrupt switch 130, which may be coupled by wired connection 156 to the wireless unit 132, which may be disposed on the outer housing 144. The control circuitry may be included in the same housing as the wireless unit 132.

[0061] FIG. 1B shows an arrangement similar to that shown in FIG. 1A, except that the first interrupt switch 130 is disposed inside the upper aperture 148 rather than the lower aperture 152, although still electrically interposed between the electrical junction 110 (FIG. 1) and the lower heating element 102 (not the upper heating element 106).

[0062] Having the first interrupt switch 130 and the wireless unit 132 be physically separate components is a preferred embodiment because it reduces the size of the first interrupt switch 130 so that it can more easily fit inside the upper aperture 148 or the lower aperture 152, although the present disclosure is not so limited. In other embodiments, the entire control module may be placed inside the outer housing. Moreover, an OEM water heater may be constructed according to the present disclosure. In an OEM configures, the controller and/or control circuitry may have a wired connection to, or be integrated with, the control module and may be connected by wire to current sensor(s) where present. In an OEM configuration, some or all of the components may be disposed inside the outer housing 144.

[0063] Preferably, the first interrupt switch 130 is the only interrupt switch (the term interrupt switch, as used herein, excluding conventional water heater hardware such as thermostats and the high limit control switch described below). However, other embodiments are also contemplated.

[0064] FIG. 1C shows an alternate arrangement which is similar to that shown in FIG. 1A, but which, in addition to the first interrupt switch 130 disposed inside the lower aperture 152, also includes a second interrupt switch 160 disposed inside the upper aperture 148. The second interrupt switch 160 is of similar construction to the first interrupt switch 130, but is interposed between the electrical junction 110 (FIG. 1) and the upper heating element 106. The second interrupt switch 160 is selectively switchable by wireless signal between a second interrupt switch open configuration and a second interrupt switch closed configuration. When the second interrupt switch 160 is in the second interrupt switch open configuration, electrical current between the electrical junction 110 and the upper heating element 106 is obstructed by the second interrupt switch 160 when the upper thermostat 108 is closed. When the second interrupt switch 160 is in the second interrupt switch closed configuration, the electrical current between the electrical junction 110 and the upper heating element 106 is unobstructed by the second interrupt switch 160 when the upper thermostat 108 is closed.

[0065] The first interrupt switch 130 and the second interrupt switch 160 may be connected to a common wireless unit 162 by respective wired connections 156, 164 as shown in FIG. 1C, or to respective separate wireless units. The arrangement shown in FIG. 1C provides additional functionality, so that both the upper heating element 106 and the lower heating element 102 may be selectively prevented from being energized (e.g. in response to one or more wireless signals). Of note, in the arrangement shown in FIG. 1C, the first interrupt switch 130 will still be interposed between the electrical junction 110 and the lower heating element 102 at an electrical position for which, at least when the upper thermostat 108 is closed, electrical communication between the electrical junction 110 and the upper heating element 106 is agnostic to whether the first interrupt switch 130 is in the closed configuration 130b or the open configuration 130a.

[0066] The arrangement shown in FIG. 1C may be used for embodiments in which the water heater 100 will deny the operating electricity to both the upper heating element 106 and the lower heating element 102 at the scheduled shutdown time, and resume the supply of operating electricity to both the upper heating element 106 and the lower heating element 102 at the initial scheduled restart time. Alternatively, the arrangement shown in FIG. 1C may be used for embodiments in which the water heater 100 will selectively permit operating electricity to reach at least the upper heating element 106 under certain conditions (e.g. at a specified start time for a specified period between the initial scheduled shutdown time and the initial scheduled restart time if the upper thermostat 108 is closed). Such an arrangement may be part of the control protocol, for example, or may be ad hoc.

[0067] In such embodiments, the second interrupt switch 160 may include circuitry that can monitor for closure of the upper thermostat 108 between the initial scheduled shutdown time and the initial scheduled restart time. For example, the second interrupt switch 160 may include circuitry for periodically applying testing electricity to the upper thermostat 108. The term testing electricity, as used herein, is distinguished from operating electricity and refers to electricity used to test whether the upper thermostat 108 is closed without materially heating the water in the tank 101. For example, the testing electricity may comprise a comparatively lower voltage (e.g. via a step-down transformer) resulting in a comparatively lower current applied across the upper thermostat 108, or, less preferably, a normal heating voltage may be applied across the upper thermostat 108 for a short period of time. If the upper thermostat 108 is closed, this indicate that the water in the upper portion of the tank 101 has cooled too much. Accordingly, the control module 133 may, responsive to detecting closure of the upper thermostat 108, cause the water heater 100 to supply operating electricity to at least the upper heating element 106 before the initial scheduled restart time. An arrangement similar to that described in FIG. 1C can also be provided as an OEM hot water heater with the various components integrated therein.

[0068] In each of the embodiments shown in FIGS. 1A, 1B and 1C, the first interrupt switch 130 and all of the high voltage wiring 168 is disposed inside of the outer housing 144 of the water heater 100 and the first interrupt switch 130 is coupled to the wireless unit 132 only by low voltage wiring in the form of the wired connections 156, 164. As used herein, the term low voltage means 12 volts or less and the term high voltage means 100 volts or more. As noted above, FIGS. 1A, 1B and 1C show only some of the high voltage wiring 168 common to all the embodiments; illustrative electrical schematics are provided in FIGS. 2A through 2F and described below.

[0069] Reference is now made to FIG. 2A, which shows an illustrative wiring schematic 200A for a first embodiment of a tank-style electric water heater in which a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102. The first interrupt switch 130 is shown as a generic block because a range of different switch types may be used. In the embodiment shown in FIG. 2A, the first interrupt switch 130 is interposed between the electrical junction 110 and the lower thermostat 104, and more particularly between the upper thermostat 108 and the lower thermostat 104.

[0070] From the grounded junction box 110, the wires run to a high limit control switch 170 where each wire encounters a respective cut-off switch 170A, 170B. The high limit control switch 170 is configured so that the cut-off switches 170A, 170B will trip to open if the water reaches an unsafe temperature (e.g. 180 degrees Fahrenheit/82 degrees Celsius), interrupting the electrical supply to both the upper and lower elements 106, 102 and the upper and lower thermostats 108, 104. The high limit control switch 170 can be manually reset after being tripped, for example by pushing a reset button. The discussion which follows assumes that the cut-off switches 170A, 170B are closed and that power is supplied from the junction box 110.

[0071] On the left side of the wiring schematic 200A, wiring 172 connects to the common terminal 174 of the upper thermostat 108 which, in the illustrated embodiment, comprises an upper circuit relay switch 108A and a lower circuit relay switch 108B. As used herein with reference to the upper thermostat 108, the term closed refers to the configuration in which the upper circuit relay switch 108A is closed and the lower circuit relay switch 108B is open. Conversely, as used herein with reference to the upper thermostat 108, the term open refers to the configuration in which the upper circuit relay switch 108A is open and the lower circuit relay switch 108B is closed. Thus, if the upper circuit relay switch 108A is closed the lower circuit relay switch 108B will be open, and vice versa.

[0072] The relay terminal 176A of the upper circuit relay switch 108A connects to one terminal 106A of the upper heating element 106, the other terminal 106B of which connects back to the cut-off switch 170B in the high limit control switch 170. When the temperature in the water monitored by the upper thermostat 108 reaches the desired setpoint, the upper circuit relay switch 108A opens and the lower circuit relay switch 108B closes. Because the upper circuit relay switch 108A connects to the upper heating element 106, the upper heating element 106 has priority over the lower heating element 102 - as long as the water monitored by the upper thermostat 108 is below the desired setpoint, the upper heating element 106 will be energized, regardless of the state of the lower thermostat 104.

[0073] The relay terminal 176B of the lower circuit relay switch 108B (the lower circuit relay switch terminal 176B of the upper thermostat 108) connects to the first interrupt switch 130, which in turn connects to the lower thermostat 104, which, in the illustrated embodiment, comprises a lower element temperature limit switch 104A. As used herein with reference to the lower thermostat 108, the term closed refers to the configuration in which the lower element temperature limit switch 104A is closed, and the term open refers to the configuration in which the lower element temperature limit switch 104A is open. The lower circuit relay switch terminal 176B of the upper thermostat 108 (the relay terminal 176B of the lower circuit relay switch 108B) connects (through the first interrupt switch 130) to an upper thermostat side terminal 178A of the lower element temperature limit switch 104A, the other terminal (element side terminal 178B) of which in turn connects to one terminal 102A on the lower heating element 102. The other terminal 102B on the lower heating element 102 (return terminal 102B) connects back to the cut-off switch 170B in the high limit control switch 170. The other terminal 102B on the lower heating element 102 also optionally connects (as shown in dashed line) selectively in parallel to the first interrupt switch 130 to provide a complete circuit (e.g. for a step-down transformer therein to provide a low voltage power supply to the control module 133 when the first interrupt switch 130 is open; if the control module includes a rechargeable battery this connection may be omitted). Similarly to the upper thermostat 108, when the temperature in the water monitored by the lower thermostat 104 reaches the desired setpoint, the lower element temperature limit switch 104A opens, preventing current from reaching the lower heating element 102.

[0074] If the first interrupt switch 130 were omitted, as in a conventional tank-style electric water heater, then whenever the temperature in the water monitored by the upper thermostat 108 reached the desired setpoint, closure of the lower circuit relay switch 108B in the upper thermostat 108 would allow current to reach the lower thermostat 104. If the temperature of the water monitored by the lower thermostat 104 is below the setpoint, the current will flow through the lower element temperature limit switch 104A and the lower heating element 102 will be energized.

[0075] With the first interrupt switch 130 in place, however, even where the lower circuit relay switch 108B in the upper thermostat 108 is closed, current can only flow through the lower thermostat 104, and hence through the lower heating element 102, if both the lower element temperature limit switch 104A in the lower thermostat 104 and the first interrupt switch 130 are also closed. Thus, opening the first interrupt switch 130 will prevent the lower heating element 102 from being energized even if both the lower circuit relay switch 108B in the upper thermostat 108 and the lower element temperature limit switch 104A in the lower thermostat 104 are closed.

[0076] Importantly, interposition of the first interrupt switch 130 between the lower circuit relay switch 108B in the upper thermostat 108 and the lower heating element 102 does not affect electrical communication between the electrical junction 110 and the upper heating element 106. When the upper thermostat 108 is closed, the flow of current from the electrical junction 110 through the upper heating element 106 and back to the electrical junction 110 completely bypasses the first interrupt switch 130. Thus, in the embodiment shown in FIG. 2A, electrical communication between the electrical junction 110 and the upper heating element 106 is governed only by the upper thermostat 108 so long as the high limit control switch 170 is closed, i.e. so long as both cut-off switches 170A, 170B therein are closed. Thus, the arrangement shown in FIG. 2A is one in which denying the operating electricity to at least the lower heating element 102 at the initial scheduled shutdown time according to the initial control protocol comprises denying operating electricity only to the lower heating element 102; the upper heating element 106 is not affected.

[0077] The electrical arrangement shown in FIG. 2A can be applied in the context of either the physical arrangement shown in FIG. 1A, or the physical arrangement shown in FIG. 1B, depending upon where the first interrupt switch 130 is physically interposed in the wiring.

[0078] Reference is now made to FIG. 2B, which shows a wiring schematic 200B for a second embodiment of a tank-style electric water heater in which a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102, more particularly between the lower thermostat 104 and the lower heating element 102. Again, the first interrupt switch 130 is shown as a generic block to illustrate that a range of different switch types may be used. In the embodiment shown in FIG. 2B, the lower circuit relay switch terminal 176B connects directly to the upper thermostat side terminal 178A of the lower temperature limit switch 104A as in a conventional tank-style electric water heater. The first interrupt switch 130 is interposed between the element side terminal 178B of the lower element temperature limit switch 104A in the lower thermostat 104 and one terminal 102A of the lower heating element 102. The other terminal 102B (return terminal 102B) on the lower heating element 102 connects back to the cut-off switch 170B in the high limit control switch 170. The return terminal 102B also optionally (as shown in dashed lines) selectively connects in parallel to the first interrupt switch 130 (e.g. to provide a complete circuit for a step-down transformer therein to provide a low voltage power supply to the control module 133 when the first interrupt switch 130 is open where no battery is provided). Current can only flow through the (closed) lower circuit relay switch 108B in the upper thermostat 108 and through the lower heating element 102 if both the lower element temperature limit switch 104A in the lower thermostat 104 and the first interrupt switch 130 are closed. Accordingly, opening the first interrupt switch 130 will prevent the lower heating element 102 from being energized even if the lower circuit relay switch 108B in the upper thermostat 108 and the lower element temperature limit switch 104A in the lower thermostat 104 are both closed.

[0079] Of important note, interposition of the first interrupt switch 130 between the lower heating element 102 and the lower element temperature limit switch 104A in the lower thermostat 104 does not affect electrical communication between the electrical junction 110 and the upper heating element 106. When the upper thermostat 108 is closed, the flow of current from the electrical junction 110 through the upper heating element 106 and back to the electrical junction 110 completely bypasses the first interrupt switch 130. Thus, as with the embodiment shown in FIG. 2A, in the embodiment shown in FIG. 2B, electrical communication between the electrical junction 110 and the upper heating element 106 is governed only by the upper thermostat 108 so long as the high limit control switch 170 is closed.

[0080] The electrical arrangement shown in FIG. 2B is typically applied in the context of the physical arrangement shown in FIG. 1B, because the wiring in which the first interrupt switch 130 is to be physically interposed is usually exclusively located in the lower aperture 152.

[0081] It is also contemplated that the first interrupt switch 130 may be interposed between the lower heating element 102 and the high limit control switch 170, i.e. between the return terminal 102B of the lower heating element 102, which is not connected to the lower thermostat 104, and the cut-off switch 170B in the high limit control switch 170. This arrangement is less preferred, however.

[0082] Reference is now made to FIG. 2C, which shows a wiring schematic 200C for a third embodiment of a tank-style electric water heater in which a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 and a second interrupt switch 160 is interposed between the electrical junction 110 and the upper heating element 106. In the embodiment shown in FIG. 2C, the electrical interposition of the first interrupt switch 130 is the same as that shown in FIG. 2A and the second interrupt switch 160 is interposed between the upper thermostat 108, in particular the upper circuit relay switch 108A thereof, and the upper heating element 106. More particularly, the second interrupt switch 160 is interposed between the relay terminal 176A of the upper circuit relay switch 108A and one terminal 106A of the upper heating element 106. The other terminal 106B of the upper heating element 106 is in electrical communication with the second interrupt switch 160 for circuit completion. When the second interrupt switch 160 is in the second interrupt switch open configuration, current cannot flow through the upper heating element 102, regardless of whether the upper thermostat 108 is open or closed, because the second interrupt switch 160 obstructs current from flowing between the upper heating element 102 and the upper circuit relay switch 108A of the upper thermostat 108. When the second interrupt switch 160 is in the second interrupt switch closed configuration, electrical communication between the electrical junction 110 and the upper heating element 102 is governed by the upper thermostat 108. In the embodiment shown in FIG. 2C, the second interrupt switch 160 also has a selective parallel connection 180 (shown in dashed lines) back to the common terminal 174 of the upper thermostat 108. When the second interrupt switch 160 is in the second interrupt switch open configuration, the selective parallel connection 180 can be used to apply testing electricity across the upper thermostat 108. Alternatively, a current sensor may be used to detect closure of the upper thermostat 108, for example as part of the hardware of the second interrupt switch 160.

[0083] Reference is now made to FIG. 2D, which shows a wiring schematic 200D for a fourth embodiment of a tank-style electric water heater in which a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 and a second interrupt switch 160 is interposed between the electrical junction 110 and the upper heating element 106. In the embodiment shown in FIG. 2D, the electrical interposition of the first interrupt switch 130 is the same as that shown in FIG. 2A and the second interrupt switch 160 is interposed between the upper heating element 106 and the high limit control switch 170, in particular the cut-off switch 170B thereof. When the second interrupt switch 160 is in the second interrupt switch open configuration, current cannot flow through the upper heating element 102, regardless of whether the upper thermostat 108 is open or closed, because the second interrupt switch 160 obstructs current from flowing between the upper heating element 102 and the cut-off switch 170A of the high limit control switch 170. When the second interrupt switch 160 is in the second interrupt switch closed configuration, electrical communication between the electrical junction 110 and the upper heating element 102 is governed by the upper thermostat 108. Although not shown in FIG. 2D, the second interrupt switch 160 may also have connections to apply testing electricity across the upper thermostat 108 when the second interrupt switch 160 is in the second interrupt switch open configuration.

[0084] FIG. 2E shows a wiring schematic 200E for a fifth embodiment of a tank-style electric water heater in which a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 and a second interrupt switch 160 is interposed between the electrical junction 110 and the upper heating element 106. In the embodiment shown in FIG. 2E, the electrical interposition of the first interrupt switch 130 is the same as that shown in FIG. 2B and the electrical interposition of the second interrupt switch 160 is the same as that in FIG. 2C, between the upper thermostat 108, in particularly the upper circuit relay switch 108A thereof, and the upper heating element 106. As in FIG. 2C, in the embodiment shown in FIG. 2E, the second interrupt switch 160 also has a selective parallel connection 180 (shown in dashed lines) back to the common terminal 174 of the upper thermostat 108. When the second interrupt switch 160 is in the second interrupt switch open configuration, the selective parallel connection 180 can be used to apply testing electricity across the upper thermostat 108. Alternatively, a current sensor may be used to detect closure of the upper thermostat 108, for example as part of the hardware of the second interrupt switch 160.

[0085] FIG. 2F shows a wiring schematic 200F for a sixth embodiment of a tank-style electric water heater in which a first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 and a second interrupt switch 160 is interposed between the electrical junction 110 and the upper heating element 106. In the embodiment shown in FIG. 2F, the electrical interposition of the first interrupt switch 130 is the same as that shown in FIG. 2B and the electrical interposition of the second interrupt switch 160 is the same as that in FIG. 2D, between the upper heating element 106 and the high limit control switch 170, in particular the cut-off switch 170B thereof. Although not shown in FIG. 2F, the second interrupt switch 160 may also have connections to apply testing electricity across the upper thermostat 108.

[0086] The embodiments shown in FIGS. 2C, 2D, 2E and 2F may be applied in the context of the physical arrangement shown in FIG. 1C, or for the embodiments shown in FIGS. 2C and 2D, both the first interrupt switch 130 and the second interrupt switch 160 may be disposed within the upper aperture 148 if there is sufficient space.

[0087] In each of the embodiments shown in FIGS. 2A, 2B, 2C, 2D, 2E and 2F, the first interrupt switch 130 is interposed between the electrical junction 110 and the lower heating element 102 at an electrical position for which, at least when the upper thermostat 108 is closed, electrical communication between the electrical junction 110 and the upper heating element 106 is agnostic to whether the first interrupt switch is in the first interrupt switch open configuration 130a or the first interrupt switch closed configuration 130b. For the embodiments shown in FIGS. 2A and 2B, electrical communication between the electrical junction 110 and the upper heating element 106 is governed only by the upper thermostat 108 at all times so long as the high limit control switch 170 is closed, i.e. so long as both of the cut-off switches 170A, 170B are closed.

[0088] For the embodiments shown in FIGS. 2C, 2D, 2E and 2F, when the upper thermostat 108 is closed, electrical communication between the electrical junction 110 and the upper heating element 106 is governed only by the second interrupt switch 160 so long as the high limit control switch 170 is closed.

[0089] The housings for the first interrupt switch 130 and/or the second interrupt switch 160 may include circuitry for monitoring the recovery activation time, or other monitoring electronics may be used.

[0090] Reference is now made to FIG. 3, which is a block diagram showing components of an illustrative embodiment of a first interrupt switch 130. The illustrative first interrupt switch includes an incoming power terminal 302, an outgoing power terminal 304, and a circuit completion terminal 306. A relay 308 and a current sensor 310 are interposed between the incoming power terminal 302 and the outgoing power terminal 304, and the connection between the incoming power terminal 302 and the outgoing power terminal 304 is coupled to the step-down transformer 316, which is also coupled to the circuit completion terminal 306. In the embodiments shown in FIGS. 2A, 2C and 2D, a first high voltage wire will be connected between the lower circuit relay switch terminal 176B of the lower circuit relay switch 108B of the upper thermostat 108 and the incoming power terminal 302, and a second high voltage wire will be connected between the outgoing power terminal 304 and the upper thermostat side terminal 178A of the lower element temperature limit switch 104A in the lower thermostat 104. In the embodiments shown in FIGS. 2B, 2E and 2F, a first high voltage wire will be connected between the element side terminal 178B of the lower element temperature limit switch 104A in the lower thermostat 104 and the incoming power terminal 302 and a second high voltage wire will be connected between the outgoing power terminal 304 and one terminal 102A on the lower heating element 102. In either case, a third high voltage wire will be connected to the circuit completion terminal 306 and placed in electrical communication with the return terminal 102B of the lower heating element 102. The return terminal 102B is the terminal of the lower heating element 102 that is not connected to the element side terminal 178B of the lower element temperature limit switch 104A in the lower thermostat 104. When the relay 308 is closed, if the lower circuit relay switch 108B in the upper thermostat 108 and the lower element temperature limit switch 104A in the lower thermostat 104 are both also closed, current flows through the relay 308 and through the lower heating element, and also through one coil of the transformer 316. The other coil of the transformer 316 provides low voltage electrical power to the control module 133, which sends control signals 312 to the relay 308 and receives data signals 314 from the current sensor 310, all through the wired connection 156. In a preferred embodiment the wired connection 156 comprises four individual wires.

[0091] The second interrupt switch 160, where present, may be similar to the first interrupt switch 130 shown in FIG. 4, optionally with additional components and terminals for applying testing electricity to the upper thermostat 108.

[0092] As noted above, while new electric tank-style water heaters can be manufactured as OEM products according to the configurations described above, an existing electric tank-style water heater lacking any interrupt switch can be retrofit to include a first interrupt switch 130 or both a first interrupt switch 130 and a second interrupt switch 160.

[0093] Before referring to FIGS. 4 and 5, it is to be noted that the relay circuit should be disconnected from the electrical junction, or the power supply should be disconnected from the relay circuit, before undertaking the methods described in those steps. All suitable safety precautions for dealing with high voltage appliances should be employed.

[0094] Reference is now made to FIG. 4, which is a flow chart showing an illustrative method 400 for retrofitting an electric tank-style water heater similar to the water heater 100 described above but which lacks an interrupt switch. As such, like reference numerals will be used. At step 402, a first interrupt switch, such as the first interrupt switch 130 described above, is interposed between the electrical junction 110 and the lower heating element 102. At optional step 404, the first interrupt switch is connected to a wireless unit (e.g. the first interrupt switch 130 may be connected via control circuitry 131 to the wireless unit 132, or to the common wireless unit 162). Optional step 404 may be omitted if the first interrupt switch and the wireless unit are integrated into a single housing. After step 402 and optional step 404, the first interrupt switch is selectively switchable (e.g. by wireless signal) between a first interrupt switch open configuration in which an electrical current between the electrical junction 110 and the lower heating element 102 is obstructed by the first interrupt switch when the upper thermostat 108 is open and the lower thermostat 104 is closed, and a first interrupt switch closed configuration in which the electrical current between the electrical junction 110 and the lower heating element 102 is unobstructed by the first interrupt switch when the upper thermostat 108 is open and the lower thermostat 104 is closed. Moreover, at least when the upper thermostat 108 is closed, electrical communication between the electrical junction 110 and the upper heating element 106 is agnostic to whether the first interrupt switch is in the first interrupt switch closed configuration or the first interrupt switch open configuration. In particularly preferred embodiments of the method 400, step 402 is carried out so that the first interrupt switch is interposed between the electrical junction 110 and the lower heating element 102 at an electrical position for which electrical communication between the electrical junction 110 and the upper heating element 106 is governed only by the upper thermostat 108 so long as the high limit control switch 170 is closed, i.e. both of the cut-off switches 170A, 170B are closed. For example, the first interrupt switch 130 may be interposed between the electrical junction 110 and the lower thermostat 104, such as between the upper thermostat 108 and the lower thermostat 104 as described above, or the first interrupt switch 130 may be interposed between the lower thermostat 104 and the lower heating element 102 as described above.

[0095] If the configuration shown in FIG. 2A or 2B is desired, the method 400 may end after optional step 404 or after step 402 if the first interrupt switch and the wireless unit are integrated into a single unit. However, if a configuration of the type shown in any one of FIGS. 2C, 2D, 2E, or 2F is desired, the method 400 may proceed to optional step 406.

[0096] At optional step 406, a second interrupt switch, such as the second interrupt switch 160 described above, is interposed between the electrical junction 110 and the upper heating element 106. At optional step 408, the second interrupt switch is connected to a wireless unit (e.g. the second interrupt switch 160 may be connected to the common wireless unit 162, or to a separate wireless unit) if it does not have integral wireless functionality. After step 406, and optional step 408 when present, the second interrupt switch is selectively switchable (e.g. by wireless signal) between a second interrupt switch open configuration in which an electrical current between the electrical junction 110 and the upper heating element 106 is obstructed by the second interrupt switch when the upper thermostat 108 is closed, and a second interrupt switch closed configuration in which the electrical current between the electrical junction 110 and the upper heating element 106 is unobstructed by the second interrupt switch when the upper thermostat 108 is closed. At optional step 410, a testing electricity connection for the second interrupt switch may be connected to the upper thermostat 108 (e.g. selective parallel connection 180 back to the common terminal 174 of the upper thermostat 108). After step 406, and steps 408 and 410 when present, the method 400 ends.

[0097] Reference is now made to FIG. 5, which shows a non-limiting illustrative method 500 for implementing steps 402 and optional step 404 of the method 400 using the first interrupt switch 130 as shown in detail in FIG. 3. At step 502, first high voltage wiring extending between the lower circuit relay switch terminal 176B of the upper thermostat 108 and the upper thermostat side terminal 178A of the lower temperature limit switch 104A of the lower thermostat 104 is disconnected. At step 504, second high voltage wiring is connected between the lower circuit relay switch terminal 176B of the upper thermostat 108 and the incoming power terminal 302 of the first interrupt switch 130, and at step 506, third high voltage wiring is connected between the outgoing power terminal 304 of the first interrupt switch 130 and the upper thermostat side terminal 178A of the lower temperature limit switch 104A. Steps 504 and 506 may be performed in reverse order, and the first high voltage wiring may be reused, for example as the second high voltage wiring. At optional step 508, fourth high voltage wiring is connected to place the circuit completion terminal 306 of the first interrupt switch 130 in electrical communication with the return terminal 102B of the lower heating element 102. Optional step 508 may be carried out, for example, where the first interrupt switch 130 does not have an internal battery.

[0098] Thus, in the illustrated embodiment, step 402 of the method 400 shown in FIG. 4 comprises steps 502, 504, 506 and optional step 508 of the method 500 shown in FIG. 5.

[0099] The method 500 shown in FIG. 5 then proceeds to step 510. At step 510, low voltage wiring is connected between the first interrupt switch 130 and a wireless unit (e.g. by connecting to the control circuitry 131 coupled to the wireless unit 132), after which the first interrupt switch 130 is switchable responsive to a wireless signal received by the wireless unit. Thus, step 510 in the method 500 corresponds to step 404 of the method 400 shown in FIG. 4. The wireless unit may be, for example, any one of a Bluetooth wireless unit, a LoRaWAN wireless unit, a Wi-Fi wireless unit, and an infrared wireless unit. At step 512, the wireless unit is positioned outside of the outer housing 144 of the water heater 100. For example, the wireless unit may be affixed to the outer surface of the outer housing 144 of the water heater 100, as shown in FIGS. 1A and 1B.

[0100] At step 514, the first interrupt switch 130 and all of the high voltage wiring, that is, the second high voltage wiring (which may be the first high voltage wiring re-used), the third high voltage wiring and the fourth high voltage wiring, are placed inside one of the apertures of the outer housing 144 of the water heater 100. For the configuration shown in FIG. 1A, this will be the lower aperture 152, and for the configuration shown in FIG. 1B, this will be the upper aperture 148. Step 514 may be carried out in discrete stages; for example, the first interrupt switch 130 may be placed into the aperture before step 502, between step 502 and step 504, or between step 504 and step 506, between step 508 and step 510 or between step 510 and 512. Similarly, the second high voltage wiring, third high voltage wiring, and fourth high voltage wiring may be placed into the aperture as it is installed, rather than in a single step. Other variations are also contemplated.

[0101] At step 516, a panel is secured over the aperture so that the first interrupt switch 130 and all of the high voltage wiring are disposed inside of the outer housing 144 of the water heater 100, behind the panel. For the configuration shown in FIG. 1A, the lower panel 154 is secured over the lower aperture 152 and for the configuration shown in FIG. 1B, the upper panel 150 is secured over the upper aperture 148.

[0102] In a variation of the method 500, the low voltage wiring may be connected to the first interrupt switch 130 before the first interrupt switch 130 is secured behind the panel, and the low voltage wiring connected to the wireless unit after the first interrupt switch 130 is secured behind the panel.

[0103] The method 500 can be adapted to achieve the configuration shown in FIG. 1C; such adaptation is within the capability of one of ordinary skill in the art, now informed by the present disclosure.

[0104] Reference is now made to FIG. 6. FIG. 6 shows a second illustrative tank-style electric water heater 600 which is similar to the first illustrative water heater 100 shown in FIG. 1, with like reference numeral denoting like features but with the prefix 6 rather than 1. The water heater 600 shown in FIG. 6 differs from the water heater 100 shown in FIG. 1 in that for the water heater 600 shown in FIG. 6, the first interrupt switch 630 is electrically interposed between the relay circuit 628 and the electrical junction 610. Therefore, the controller 634 cooperates with the control module 633 to cause the water heater 600 to deny the operating electricity to both the upper heating element 606 and the lower heating element 602 at the scheduled shutdown time, and to resume the supply of operating electricity to both the upper heating element 606 and the lower heating element 602 at the scheduled restart time. Although not shown in FIG. 6, the water heater 600 includes circuitry (e.g. current sensors) enabling the control module 633 to monitor the top-up activation time and the recovery activation time of the water heater 600, so that adjustments can be made to the initial control protocol to obtain an adjusted control protocol based on the monitoring.

[0105] In addition to enabling the determination of the recovery activation time and the top-up activation time, the use of current sensors enables embodiments in which the controller 634 cooperates with the control module 633 to cause the water heater 600 to selectively permit operating electricity to reach at least the upper heating element 606 under certain conditions (e.g. at a specified start time for a specified period between the initial scheduled shutdown time and the initial scheduled restart time if the upper thermostat 608 is closed). Preferably, the control module 633 is also coupled to circuitry to apply testing electricity across the upper thermostat 608 and, if the upper thermostat 608 is determined to be closed after the scheduled shutdown time and before the scheduled restart time, the control module 633 (optionally in cooperation with the controller 634) may close the first interrupt switch 630 to cause the water heater 600 to supply operating electricity to the upper heating element 606 (and the lower heating element 602) before the scheduled restart time. For example, the control module 633 may include a step-down transformer to allow a low voltage pulse of testing electricity into the electrical junction 610, and may be coupled to a current sensor to detect the (low voltage) current. In one embodiment, a current sensor may be configured to detect whether current reaches the upper heating element 606, which means that the upper thermostat 608 is closed. In another embodiment, a current sensor may be configured to detect whether current reaches the lower heating element 602, which means that the upper thermostat 606 is open. In a further embodiment, both types of current sensor may be used (e.g. to enable verification and/or fault detection). A current sensor configured to detect whether current reaches the upper heating element 606 may be placed in any of the electrical positions shown for the second interrupt switch 160 in FIG. 2C, 2D or 2F. A current sensor configured to detect whether current reaches the lower heating element 602 may be placed in in any of the electrical positions shown for the first interrupt switch 130 in FIGS. 2A to 2F. In a currently preferred embodiment, a current sensor configured to detect whether current reaches the lower heating element 602 is used, and may be physically positioned as shown for the first interrupt switch 130 in FIG. 1A.

[0106] In the illustrated embodiment, the first interrupt switch 630 is electrically coupled to control circuitry 631 and a wireless unit 632, which together form the control module 633, which is responsive to a wireless signal received from the controller 634 to control the first interrupt switch 630. The wireless signal arrangements may be any of those described above in the context of FIG. 1. The first interrupt switch 630, control circuitry 631 and wireless unit 632 may be housed within a common body, or may be at various physical locations while electrically coupled to one another. The controller 634 may be a network-capable hardware device that is communicatively coupled to the power scheduler 638 (e.g. a power utility or a third-party power scheduler) via a network 640 such as the Internet. The power scheduler 638 can thus send signals to the controller 634, which can in turn communicate with the control module 633 to control the first interrupt switch 630 according to a control protocol. Adjustment of the control protocol to obtain an adjusted control protocol can be carried out by any one or more of the control module 633, the controller 634 and the power scheduler 638, alone or in combination, depending on the desired configuration.

[0107] Preferably, the wireless unit 632 can send and receive wireless signals 636 to and from the controller 634. The control module 633 may be configured to obtain data about usage of the upper heating element 606 and the lower heating element 602 and send this data to the wireless unit 632 to send back to the controller 634, and the data can be sent from the controller 634 to the power scheduler 638, as described above in the context of FIG. 1. The control module 630 may include a step-down transformer to provide a low voltage power supply to the control module 633 from the high voltage supplied to the water heater 600 from the junction 610. The control module 633 is preferably coupled to a rechargeable battery to provide a power supply when no current is flowing through the first interrupt switch 630; the control may also be connectable to an electrical outlet. An OEM implementation of the water heater 600 is also contemplated.

[0108] Reference is now made to FIG. 7, which shows an illustrative method 700 for controlling an electric tank-style water heater having at least an upper heating element and a lower heating element, such as the water heater 100 shown in FIG. 1 or the water heater 600 shown in FIG. 6.

[0109] At step 702, operating electricity is denied to at least the lower heating element at an initial scheduled shutdown time according to an initial control protocol. In some embodiments the operating electricity may be denied only to the lower heating element at the initial scheduled shutdown time; in other embodiments the operating electricity is denied to both the upper heating element and the lower heating element at the initial scheduled shutdown time.

[0110] Optional steps 704 to 706 may be included where the operating electricity is denied to both the upper heating element and the lower heating element at the initial scheduled shutdown time. At optional step 704, which occurs between the initial scheduled shutdown time and the initial scheduled restart time, the method 700 monitors for closure of the upper thermostat governing the upper heating element. If closure of the upper thermostat is detected between the initial scheduled shutdown time and the initial scheduled restart time (yes at step 704), the method 700 proceeds to optional step 706. At optional step 706, responsive to detecting closure of the upper thermostat at step 704, the method 700 supplies the operating electricity to at least the upper heating element before the initial scheduled restart time. The method 700 then proceeds to optional step 708, if present, or else to step 710. If closure of the upper thermostat is not detected between the initial scheduled shutdown time and the initial scheduled restart time at step 704 (no at step 704), the method 700 proceeds from step 704 directly to step 710. Thus, optional steps 704 and 706 represent an implementation of the method 700 in which the operating electricity is at least selectively permitted to reach at least the upper heating element. If optional steps 704 and 706 are not present, the method 700 proceeds directly from step 702 to step 710.

[0111] If optional steps 704 and 706 are present, further optional step 708 may be implemented after implementing step 706. At optional step 708, the method 700 monitors a top-up activation time of the water heater between the initial scheduled shutdown time and the initial scheduled restart time.

[0112] At step 710, the method 700 resumes supply of the operating electricity to at least the lower heating element at the initial scheduled restart time according to the initial control protocol. If the operating electricity was denied to both the upper heating element and the lower heating element at the initial scheduled shutdown time at step 702, then at step 710 the supply of the operating electricity is resumed to both the upper heating element and the lower heating element at the initial scheduled restart time. If the operating electricity was denied only to the lower heating element at the initial scheduled shutdown time at step 702, then at step 710 the supply of the operating electricity is resumed to the lower heating element at the initial scheduled restart time. After step 710, the method 700 proceeds to step 712.

[0113] At step 712, the method 700 monitors the recovery activation time of the water heater following the resumption of the supply of the operating electricity at the initial scheduled restart time. At step 714, the method 700 tests whether a function of the recovery activation time of the water heater exceeds an upper threshold. Where optional step 708 is present, the function of the recovery activation time tested at step 714 may incorporate the top-up activation time from optional step 708.

[0114] If the upper threshold is exceeded at step 714 (yes at step 714), the method 700 proceeds to step 716. At step 716, responsive to the function of the recovery activation time of the water heater exceeding the upper threshold, the method 700 adjusts the initial control protocol to obtain a first adjusted control protocol to reduce the recovery activation time on the next iteration of the (adjusted) control protocol. For example, at step 716 the method 700 may adjust the initial scheduled shutdown time to become an adjusted scheduled shutdown time that is later than the initial scheduled shutdown time and/or adjust the initial control protocol to allow activation of at least one of the upper heating element and the lower heating element between the adjusted scheduled shutdown time and the adjusted scheduled restart time. Or, at step 716 the method 700 may adjust the parameters governing when operating electricity is allowed to reach the upper heating element. These are merely illustrative, non-limiting examples.

[0115] If the upper threshold is not exceeded at step 714 (no at step 714), the method 700 may proceed to optional step 718. At optional step 718, the method 700 tests whether the function of the recovery activation time of the water heater fails to exceed a lower threshold. If the function of the recovery activation time of the water heater fails to exceed the lower threshold (yes at optional step 718), the method 700 proceeds to optional step 720. At optional step 720, responsive to the function of the recovery activation time of the water heater failing to exceed the lower threshold, the method 700 adjusts the initial control protocol to obtain a second adjusted control protocol to increase the recovery activation time on the next iteration of the (adjusted) control protocol. For example, at optional step 720 the method 700 may adjust the initial scheduled shutdown time to become an adjusted scheduled shutdown time that is earlier than the initial shutdown time and/or adjust the initial scheduled restart time to become an adjusted scheduled restart time that is later than the initial scheduled restart time.

[0116] As noted above, monitoring the recovery activation time (and optionally top-up recovery time) of the water heater following the resumption of the supply of the operating electricity may occur over a single day, or over multiple days, which need not be consecutive days.

[0117] As can be seen from the above description, the electric tank-style water heater technology described herein represents significantly more than merely using categories to organize, store and transmit information and organizing information through mathematical correlations. The present disclosure describes an improvement to the technology of electric tank-style water heaters, as it provides the advantage of load-shifting while mitigating the impact of the load shifting on availability of hot water. This may facilitate wider adoption of load-shifting. Moreover, the technology is applied by using a particular machine, namely an electric tank-style water heater technology. As such, the technology is confined to electric tank-style water heaters. The technology manifests a discernable physical effect or change by controlling the timing and the amount of heat that is transferred into the water in the tank.

[0118] Certain currently preferred embodiments have been described by way of example. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims.