Scale Alarm System and Method

Abstract

A method for generating a scale service alert for a water heater includes calculating an initial bypass mixing percentage of water flowing through a bypass line, associating the calculated initial bypass mixing percentage of water with a detected position of a mixing valve to obtain a baseline feedback measurement, periodically comparing current measurements of the bypass mixing percentage of water and/or a current position of the mixing valve to the baseline feedback measurement, detecting blockages and triggering the scale service alert when the current position of the mixing valve changes by a pre-determined amount from the associated baseline position of the mixing valve to achieve the same bypass mixing percentage of water or when the current measurements of the bypass mixing percentage of water deviates from the initial bypass mixing percentage of water by a pre-determined factor.

Claims

1. A method for generating a scale service alert in a water heater appliance having a mixing valve configured to mix two sources of water at different temperatures to achieve a mix temperature, a heat source, and a controller, the method comprising: measuring a first temperature of the water received from a cold water inlet, a second temperature of the water delivered from a hot water outlet from the heat source, and a third temperature of the water delivered from a mixing outlet of a mixing region; calculating an initial bypass mixing percentage of water flowing through a bypass line based on the first temperature of the water, the second temperature of the water, and the third temperature of the water; detecting a baseline position of the mixing valve; associating the calculated initial bypass mixing percentage of water with the detected position of the mixing valve to obtain a baseline feedback measurement of the calculated initial bypass mixing percentage of water and the associated baseline position of the mixing valve; periodically comparing current measurements of at least one of the bypass mixing percentage of water or a current position of the mixing valve to the baseline feedback measurement; detecting blockages in at least one of the two sources of water when the current position of the mixing valve changes by a pre-determined amount from the associated baseline position of the mixing valve to achieve the same bypass mixing percentage of water or when the current measurements of the bypass mixing percentage of water deviates from the initial bypass mixing percentage of water by a pre-determined factor; and when the current position of the mixing valve position changes by the pre-determined amount to achieve the same bypass mixing percentage of water or when the current measurements of the bypass mixing percentage of water deviates from the initial bypass mixing percentage of water by the pre-determined factor, triggering the scale service alert, thereby alerting the user to service the water heater appliance.

2. The method of claim 1, wherein the measuring the first temperature, the second temperature, and the third temperature; the calculating the initial bypass mixing percentage of water flowing through the heat; the detecting the position of the mixing valve when the water heating appliance was new; and the associating the calculated initial bypass mixing percentage of water with the detected position of the mixing valve are performed after an initial installation of the water heater appliance and after a first call for heat.

3. The method of claim 1, wherein the periodically comparing the current measurements of the bypass mixing percentage of water or the current position of the mixing valve to the baseline feedback measurement; the detecting blockages; the detecting the baseline position of the mixing valve; and the triggering the scale service alert are performed during a service of the water heater appliance and after one or more calls for heat.

4. The method of claim 1, wherein the current measurements of the bypass mixing percentage of water comprise periodically calculating a current bypass mixing percentage of water flowing through the bypass line based on the first temperature of the water, the second temperature of the water, and the third temperature of the water.

5. The method of claim 1, wherein the periodically comparing the current measurements of the bypass mixing percentage of water or the current position of the mixing valve to the baseline feedback measurement comprises: comparing the current measurements of the bypass mixing percentage of water to the calculated initial bypass mixing percentage of water, and comparing the current position of the mixing valve to the baseline position of the mixing valve associated with the calculated initial bypass mixing percentage of water.

6. The method of claim 1, further comprising storing the baseline feedback measurement in a non-volatile memory of the controller.

7. The method of claim 1, further comprising: drawing heated water from the water heater appliance for a predetermined time period at a first flowrate; detecting a mixing percentage of the two sources of water, including at least one of a mixing valve position, a total flowrate, and a percentage of water flowing through the heat source at the first flowrate; detecting operation of the water heater appliance at a second flowrate and at least one of the mixing valve position, the total flowrate, or the percentage of water flowing through the heat source at the second flowrate; comparing the mixing valve position at the first flowrate to the mixing valve position at the second flowrate, or the percentage of water flowing through the heat source at the first flowrate to the percentage of water flowing through the heat source at the second flowrate; and detecting blockages in at least one of the two sources of water when the mixing valve position at the first flowrate and the mixing valve position at the second flowrate differ by a pre-determined amount, or when the percentage of water flowing through the heat source at the first flowrate and the percentage of water flowing through the heat source at the second flowrate differ by a pre-determined factor.

8. The method of claim 1, wherein the service alert comprises at least one of an error message, a flashing light, a sound, or a push-up message or a notification to a computer, a cloud server, or a mobile device over a communication network.

9. The method of claim 8, wherein the service alert is transmitted via a wired connection, a wireless communications protocol, or a non-wireless communications protocol.

10. The method of claim 9, wherein the wireless communications protocol comprises at least one of a Bluetooth communications protocol, Near Field Communications protocol, a WiFi communications protocol, ZigBee, Z-Wave, long range (LoRa), or LoRaWAN communications protocol.

11. The method of claim 1, wherein the initial bypass mixing percentage of water flowing through the bypass line and the current measurements of the bypass mixing percentage of water are calculated as a ratio of a difference between the third temperature of the water and the second temperature of the water to the difference between the first temperature of the water and the second temperature of the water.

12. The method of claim 1, wherein the initial bypass mixing percentage of water flowing through the bypass line and the current measurements of the bypass mixing percentage of water are calculated with a formula %.sub.cold=(T.sub.mixT.sub.hx)/(T.sub.hx+T.sub.cold), wherein %.sub.cold is the initial bypass mixing percentage of water flowing through the bypass line or the current measurements of the bypass mixing percentage of water, T.sub.cold is the first temperature of the water, T.sub.hx is the second temperature of the water, and T.sub.mix is the third temperature of the water.

13. The method of claim 1, further comprising counting steps of a stepper motor or using position feedback from a position sensor to determine the position of the mixing valve in response to temperature feedback based on the first temperature of the water, the second temperature of the water, and the third temperature of the water.

14. The method of claim 1, wherein the scale service alert indicates blockages in at least one of the two sources of water from scale buildup that require service or maintenance of the water heater appliance.

15. A water heater appliance configured to generate a scale service alert, the water heater appliance comprising: a heat source configured to receive water to be heated; a mixing valve configured to receive water from two sources of water and to mix the water from the two sources of water; at least one temperature sensor configured to sense a temperature of the water upstream of, downstream of, or within the heat source; and a controller configured to: calculate a mixing percentage from the two sources of water associated with a mixing valve position to obtain a baseline feedback measurement; compare feedback measurements to the baseline feedback measurement; detect blockages in at least one of the two sources of water when the mixing valve position requires a change of a pre-determined amount to achieve the same mixing percentage from the two sources of water; and when the mixing valve position requires the change of the pre-determined amount to achieve the same mixing percentage from the two sources of water, trigger the scale service alert, thereby alerting the user to service the water heater appliance.

16. The water heater appliance of claim 15, the water heater appliance being a tankless water heater, a storage water heater, a boiler, or a heat pump water heater.

17. The water heater appliance of claim 15, wherein the mixing valve comprises a stepper motor configured to count steps or to use position feedback from a position sensor to determine the mixing valve position in response to temperature feedback based on a first temperature of the water at a cold water inlet, a second temperature of the water at a hot water outlet from the heat source, and a third temperature of the water at a mixing outlet of the mixing valve.

18. The water heater appliance of claim 15, wherein the mixing percentage from the two sources of water comprises a bypass mixing percentage of water flowing through the bypass line based on the temperature of the water upstream of, downstream of, or within the heat source.

19. The water heater appliance of claim 15, wherein the scale service alert comprises at least one of an error message, a flashing light, a sound, or a push-up message or a notification to a computer, a cloud server, or a mobile device over a communication network.

20. A method for generating a scale service alert in a water heater appliance having a mixing region configured to deliver mixed water by mixing heated water received from a heat source and bypass water that bypasses the heat source, the method comprising: calculating a baseline bypass percentage of bypass water entering the mixing region based on baseline temperatures of the bypass water, the heated water, and the mixed water; detecting a baseline position of a mixing valve in the mixing region associated with the baseline bypass percentage of bypass water to obtain a baseline feedback measurement including the baseline bypass percentage of bypass water and the baseline position of the mixing valve; comparing the baseline feedback measurement to at least one of a subsequent bypass percentage of bypass water or a subsequent position of the mixing valve; and when the subsequent bypass percentage of bypass water deviates from the baseline bypass percentage of bypass water by a pre-determined factor, or when the subsequent position of the mixing valve deviates from the baseline position of the mixing valve by a pre-determined factor, triggering the scale service alert, thereby alerting the user to service the water heater appliance.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0008] The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings are the following figures:

[0009] FIG. 1 depicts schematically an exemplary embodiment of a water heating appliance, such as a tankless water heater, including a system for detecting scale according to an aspect of the invention, including a detail of a mixing region of the water heating appliance.

[0010] FIG. 2 depicts schematically an exemplary embodiment of a water heating appliance, such as a tankless water heater, including recirculation pump and a system for detecting scale according to an aspect of the invention, including a detail of a mixing region of the water heating appliance.

[0011] FIG. 3A illustrates an embodiment of a mixing valve that includes a stepper motor that can be used according to an aspect of the invention.

[0012] FIG. 3B illustrates the mixing valve of FIG. 3A that includes a stepper motor that can be used according to an aspect of the invention and schematic illustrations of flow.

[0013] FIG. 4 illustrates schematically an embodiment of a water heating appliance according to an aspect of the invention.

[0014] FIG. 5 is a flowchart illustrating an overall exemplary method for detecting scale in a water heating appliance and for generating a scale service alert, according to an exemplary embodiment of the invention.

[0015] FIG. 6 is a flowchart illustrating the details of an exemplary method for detecting scale in a water heating appliance and for generating a scale service alert, according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Aspects of the disclosed subject matter relate to a method for detecting scale from water in a water heating appliance, such as a water heater, a boiler, or the like, and generating a service alert. Fouling service alarms can be based on water usage and/or time. Fouling service alarms can also be based additionally or alternatively on indicia or direct evidence of fouling. Such fouling service alarms based on indicia or direct evidence of fouling can help reduce or avoid performing service when not needed or can help reduce or avoid calls for service after an issue has become serious or perhaps past the point at which service would fix the issue.

[0017] The disclosed methods may provide improvements in service life and efficiency of downstream system components or devices and response time to temperature demand. Such improvements may be created, for example, by control of water flow velocity from a heat exchanger and through a reservoir, or improvements in the resources associated with operating and/or repairing downstream devices in a water heating system due to scale build up.

[0018] The subject matter disclosed herein is described primarily with respect to water heaters and water heating systems. However, it will be understood that the scope of this disclosure is not so limited. The subject matter of this disclosure is applicable to a water heating or distribution system including any type or variety of heat exchanger, including any heat exchanger designed to exchange heat between fluids (liquid or gas), particularly fluids with a potential for fouling, including but not limited to fluid containing calcium, iron, manganese, or other elements associated with fouling. In particular, this disclosure is not limited to devices for heating water (i.e. H.sub.2O). As used herein, the terms water heating appliance, water heating system, and water heating are intended to encompass any system, device, or method adapted to generate and/or maintain a source of heated fluid.

[0019] According to some embodiments of the invention, an improved method or system for detection of a blockage or reduction of the water flow from scale or fouling (e.g., caused by contaminant buildup) in a water heater is provided as well as a method or system for generating a service alert for service or maintenance of the water heater.

[0020] In some embodiments of the invention, this may be accomplished by using feedback of a mixing valve position to detect blockages and trigger a service alert. For example, when a new water heater is installed and receives its first sustained call for heat, the method uses temperature feedback (e.g., inlet temperature, outlet temperature) to calculate a mixing percentage from two sources of water (one hot or heated, and one cold), including total flowrate and the bypass percentage of water flowing through the bypass line of the water heater. This feedback information is then associated with the position of a mixing valve (e.g., using a stepper motor and/or a controller for counting steps or using position feedback) to obtain a baseline feedback measurement. The baseline feedback measurement is stored in a memory of a controller of the water heater. Over time, as the water heater operates, the same feedback measurements are periodically compared to the baseline feedback measurements stored in the memory, in order to detect blockages in the hot source path and the cold source path. For example, when the position of the mixing valve needs to change by a calculated or a pre-determined amount to achieve the same mix temperature or when the bypass percentage of water flowing through the bypass line deviates from the previously logged value by a pre-determined amount, the appliance triggers a service alert, thereby alerting the user to clean the heat exchanger or service the water heating appliance (e.g., due to fouling). For example, such service can include taking steps to reduce blockage caused by scale by flushing the system, descaling the water heater tank with a descaler or with a cleaning mixture of vinegar and water, replacing one or more components, or otherwise returning the appliance to nominal operation.

[0021] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

[0022] The invention is best understood from the following detailed description when read in connection with the accompanying drawing figures, which shows exemplary embodiments of the invention selected for illustrative purposes. The invention will be illustrated with reference to the figures. Such figures are intended to be illustrative rather than limiting and are included herewith to facilitate the explanation of the present invention.

[0023] Generally, one aspect of the invention provides, according to an exemplary embodiment, a method for generating a scale service alert in a water heater appliance having a mixing valve configured to mix cold water and heated water (e.g., two sources of water at different temperatures) to achieve a mix temperature. The method according to this exemplary embodiment includes steps such as: [0024] (1) measuring a cold water temperature (e.g., a first temperature of the water at a cold water inlet), a heated water temperature (e.g., a second temperature of the water at a hot water outlet from a heat exchanger), and the mix temperature (e.g., a third temperature of the water at a mixing location downstream from the heat exchanger outlet); [0025] (2) calculating an initial heated water percentage associated with the cold water temperature, the heated water temperature, and the mix temperature (e.g., a bypass mixing percentage of water flowing through the bypass line based on the first temperature of the water, the second temperature of the water, and the third temperature of the water); [0026] (3) associating the calculated initial heated water percentage (e.g., the calculated initial bypass mixing percentage of water) with a baseline position of the mixing valve (e.g., a detected position of the mixing valve when the water heating appliance was new) to obtain a baseline heated water percentage at a baseline position of the mixing valve (e.g., a feedback measurement of the calculated initial bypass mixing percentage of water and the associated baseline position of the mixing valve); [0027] (4) periodically comparing current heated water percentages to the baseline heated water percentage or comparing positions of the mixing valve to the baseline position of the mixing valve (e.g., comparing current measurements of the bypass mixing percentage of water or a current position of the mixing valve to the baseline feedback measurement); [0028] (5) detecting deviations of current heated water percentages from the baseline heated water percentage or deviations of positions of the mixing valve from the baseline position of the mixing valve to achieve the baseline heated water percentage (e.g., detecting blockages in at least one of the two sources of water when the current position of the mixing valve changes by a pre-determined amount from the associated baseline position of the mixing valve to achieve the same bypass mixing percentage of water or when the current measurements of the bypass mixing percentage of water deviates from the initial bypass mixing percentage of water by a pre-determined factor); and [0029] (6) when the current heated water percentages deviates from the baseline heated water percentage by a pre-determined factor, or when the position of the mixing valve deviates from the baseline position of the mixing valve by a pre-determined amount to achieve the baseline heated water percentage (e.g., when the current position of the mixing valve position changes by the pre-determined amount to achieve the same bypass mixing percentage of water or when the current measurements of the bypass mixing percentage of water deviates from the initial bypass mixing percentage of water by the pre-determined factor), triggering the scale service alert, thereby alerting the user to service the water heater appliance.

[0030] In some embodiments of the invention, another aspect of the invention provides, according to an exemplary embodiment, a method for generating a scale service alert in a water heater appliance having a mixing region configured to deliver mixed water by mixing heated water received from a heat source and bypass water that bypasses the heat source. The method according to this exemplary embodiment includes steps such as: [0031] (1) calculating a baseline bypass percentage of bypass water (e.g., cold water from a cold water inlet) entering the mixing region based on baseline temperatures of the bypass water, the heated water (e.g., the water at a hot water outlet of the heat source), and the mixed water (e.g., the water at a mixing location downstream from the heat source outlet); [0032] (2) detecting a baseline position of a mixing valve (e.g., a detected position of the mixing valve when the water heating appliance was new) in the mixing region associated with the baseline bypass percentage of bypass water (e.g., the calculated baseline bypass percentage of bypass water) to obtain a baseline feedback measurement including the baseline bypass percentage of bypass water and the baseline position of the mixing valve (e.g., a feedback measurement of the calculated baseline bypass percentage of bypass water and the associated baseline position of the mixing valve); [0033] (3) comparing the baseline feedback measurement to at least one of a subsequent bypass percentage of bypass water or a subsequent position of the mixing valve (e.g., comparing current measurements of the bypass percentage of bypass water or a current position of the mixing valve to the baseline feedback measurement); and [0034] (4) when the subsequent bypass percentage of bypass water deviates from the baseline bypass percentage of bypass water by a pre-determined factor, or when the subsequent position of the mixing valve deviates from the baseline position of the mixing valve by a pre-determined factor (e.g., when the current position of the mixing valve position changes by the pre-determined factor to achieve the same baseline bypass percentage of bypass water or when the current measurement of the bypass percentage of bypass water deviates from the baseline bypass percentage of bypass water by the pre-determined factor), triggering the scale service alert, thereby alerting the user to service the water heater appliance.

[0035] Referring now to the embodiments as illustrated in the drawings, FIG. 1 is a schematic block diagram that illustrates an example of a water heating appliance 100 that detects scale collected from water in the water heating appliance 100. The water heating appliance 100 is optionally a tankless water heater, but may be any form of appliance configured to heat water, including without limitation a storage water heater, a boiler, a heat pump water heater, or any other system used to heat water that uses a mixing valve or otherwise adjusts the flow from one or more sources of water to mix or otherwise deliver a desired water flow or condition.

[0036] The water heating appliance 100 includes conduits (generally indicated schematically by lines with arrows in FIG. 1) through which the water flows along a water pathway 101 through the water heater or heating appliance 100. A heat source, such as a heat exchanger 102, for example, is positioned to transfer heat to the water in the conduits. The heat exchanger 102 can include, for example, a coiled conduit configured to contain the water to be heated. The coiled conduit may include a plurality of rotations extending between an inlet for the water to be heated and an outlet for heated water.

[0037] Turning back to FIG. 1, cold water flows through a cold water inlet 104 through the interior of the water heater 100 and into the heat exchanger 102. Hot or heated water flows through an outlet 106 of the heat exchanger 102 into a mixing region 100 such as a mixing block. A bypass conduit 108 diverts a portion of the cold water from the cold water supply inlet 104 into the mixing region 110 that is configured to selectively mix the cold water from the cold water supply inlet 104 with the hot water from the outlet 106 of the heat exchanger 102. The mixed water from the mixing region 110 is delivered from a mix outlet of the mixing region 110 into the hot water supply line 112.

[0038] A mixing valve 114 is arranged in fluid communication with the cold water inlet 104 via the bypass conduit 108 and the mixing region 110. The mixing valve 114 can be a thermostatically controlled valve configured to control the flow of cold water from the cold water inlet 104 through the bypass conduit 108 and into the mixing region 110 as a function of a temperature setting. The mixing valve 114 can be housed within the mixing region 110 or upstream of the mixing region 110.

[0039] The mixing valve 114 further includes a stepper motor 302 (FIGS. 3A and 3B) coupled via a shaft 304 to a head 316 of the mixing valve 114. The stepper motor 302 is configured to (e.g., based on signals from a controller) rotate in a series of small angular steps, rotate the shaft 304, and translate rotational motion of the motor 302 into interlinear motion of the head 316 of the mixing valve 114. For example, the stepper motor 302 can include an insert with an O-ring 318 that can be configured to maintain water pressure. The shaft 304 can also include an O-ring seal and a thread 320, for example. During rotation of stepper motor 302, rotation of the stepper motor 302 is translated into interlinear motion of the head 316 of the mixing valve 114. When the stepper motor 302 rotates, the head 316 of the mixing valve 114 moves (as shown by the double arrows 309 in FIGS. 3A and 3B) in an interlinear motion back and forth toward an open position and a closed position within a mixing chamber 306 of the mixing valve 114.

[0040] Each rotational step of the stepper motor 302 corresponds to a position of the head 316 of the mixing valve 114 within the mixing chamber 306 of the mixing valve 114. During operation of the water heater appliance 100, a portion of the cold or relatively cold water that flows from the cold water inlet 104 (FIG. 1) is diverted by the bypass conduit 108 to the mixing valve 114 and enters an inlet 312 of the mixing valve 114 and flows, as shown with arrows C in FIG. 3B, through an outlet 314 of the mixing valve 114 toward the mixing region or mixing block 110, which selectively mixes the cold water from the cold water supply inlet 104 with hot or relatively hot water from the outlet 106 of the heat exchanger 102.

[0041] During the life of the water heater appliance 100, scale buildup impacts the position of the head 316 of the mixing valve 114, among other components of the water heater appliance 100. For example, when the water heater appliance 100 is new or newly serviced or cleaned, the position of the head 316 of the mixing valve 114 required to achieve a water temperature of the mixed water desired by the customer can correspond to a position, such as determined by a number of steps, of the stepper motor 302. As illustrated with position 308 of the head 316 of the mixing valve 114 in FIGS. 3A and 3B, for example, substantial space is available within the mixing chamber 306 of the mixing valve 114 for cold water flowing from the bypass conduit 108 to flow toward the mixing region 110. In one example, the number of steps can be 1500, simply for purposes of illustration.

[0042] The position of a used and a potentially scaled water heater appliance 100 required to achieve the desired water temperature of the mixed water can correspond to a different position of the stepper motor 302. For illustration, that position may be about 2,200 steps of the stepper motor 302, for example. As illustrated with position 310 of the head 316 of the mixing valve 114 in FIGS. 3A and 3B, for example, due to fouling or scale buildup, less space is available within the mixing chamber 306 of the mixing valve 114 for cold water flowing from the bypass conduit 108 to flow toward the mixing region 110, and the mixing valve 114 is almost closed. A fully closed mixing valve 114 can correspond to about 2,700 steps of the stepper motor 302 in one example. In other words, the percentage of water flowing through the bypass conduit 108 and the mixing valve 114 can be expressed as a function of fouling or scale buildup, as manifested by the changing position of the head 316 of the mixing valve 114 illustrated in FIGS. 3A and 3B that corresponds to a rotational step of the stepper motor 302 (e.g., 500, 700, 1100, 1500 steps, etc.). If fouling is present and the position of the head 316 of the mixing valve 114 changes, there is an increase in pressure drop of the percentage of water flowing through the bypass conduit 108 and the mixing valve 114.

[0043] Turning back to FIG. 1, the water heater 100 includes one or more temperature sensors (e.g., Negative Temperature Coefficient (NTC) sensors) indicated as items 116, 118, 120 configured to detect the temperature of the water as water flows through the water pathway 101 within the water heater 100. In an exemplary embodiment, sensing the temperature of the water includes sensing, with a sensor 116, a cold water temperature measured at the cold water inlet 104; sensing, with a sensor 118, a hot water temperature measured at the hot water outlet 106 of the heat exchanger 102; and sensing, with a sensor 120, the temperature of the water measured at the mixing outlet of the mixing region 110.

[0044] The water heater 100 further includes a flow sensor 122 positioned to directly or indirectly sense the flow of the water along a water pathway 101 through the water heater 100, and configured to provide signals for the water flow rate.

[0045] FIG. 2 is a schematic block diagram that illustrates another example of a water heating appliance 100 that detects scale collected from water in the water heating appliance 100. The components of the water heating appliance 100 depicted in FIG. 2 are the same as the ones depicted in FIG. 1, except for an optional internal recirculation pump 202 that may be activated to increase the supply of hot water from the heat exchanger 102.

[0046] Turning now to FIG. 4, the water heater 100 includes a heat source 102 (e.g., an electric or fuel-fired heat exchanger), a controller 402, and a temperature sensor 404 (e.g., a thermistor or a thermostat (e.g., bimetallic or thermocouple-based thermostat)) that monitors the temperature of the water in the water heater 100.

[0047] In general, the controller 402 illustrated in FIG. 4 can include devices such as a microprocessor, memory devices, analog input/output (I/O), digital I/O, power regulation, etc. (not shown), which serve to perform various operations. For example, such operations may include operations related to collecting and/or recording temperatures from temperature sensors 116, 118, 120, 404, and acting upon those temperatures to control the operation of the water heater 100. The controller 402 is operatively coupled to the temperature sensors 116, 118, 120, 404; the heat exchanger 102; the mixing valve 114; and the flowrate sensor 122.

[0048] The memory of the controller 402 generally stores the programming for the controller 402. Specifically, the memory stores instructions that, when executed by the controller 402, cause the controller 402 to provide functionality related to detecting scale in the water heater 100, generating a scale service alert, temperature detection programming, temperature indicator programming, etc. To facilitate these programs, the memory also stores baseline measurements, such as the bypass mixing percentage % cold of water flowing through the bypass conduit 108, which is calculated when the water heater 100 is new (e.g., no fouling or scale is present) and the associated position of the mixing valve 114 when the baseline bypass mixing percentage % cold of water is calculated, temperature records comprising the time, the temperature of the water along the water pathway 101 within the water heater 100, and the position of the mixing valve 114. For example, the memory stores various values, including but not limited to a setpoint temperature of the water of the water heater 100, temperature thresholds, predetermined amounts of change of the position of the mixing valve 114 and the bypass mixing percentage % cold of water, etc.

[0049] The memory of the controller 402 can be a non-transitory computer-readable medium or a non-volatile data medium, such as a hard disk, a flash memory, an optical disk, solid-state memory, e.g., flash memory, or other storage media known in the art, for example. The data medium may be any entity or device capable of storing instructions. For example, a non-transitory computer-readable medium may include, for example, random access memory (RAM), read-only memory (ROM), compact disc read-only memory (CD-ROM), digital versatile discs (DVDs), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), non-volatile random-access memory (NVRAM), volatile memory, non-volatile memory, hard drives, flash drives, disks, caches, registers, an optical data storage medium, a physical medium with patterns, or networked versions thereof. A non-transitory computer-readable medium may include multiple structures and may be located at a local location or at a remote location.

[0050] The memory of the controller 402 may include a flash memory (non-volatile or persistent storage), a read-only memory (ROM), and a random access memory (RAM) (volatile storage). The RAM serves as short term storage for instructions and data being handled by the controller 402, e.g., as a working data processing memory. The flash memory typically provides longer term storage.

[0051] Of course, other storage devices or configurations may be added to or substituted for those in the example. Such other storage devices may be implemented using any type of storage medium having computer or processor readable instructions or programming stored therein and may include, for example, any or all of the tangible memory of the computers, processors or the like, or associated modules.

[0052] Hence, a machine-readable medium or a computer-readable medium may take many forms of tangible storage medium. Non-volatile storage media include, for example, optical or magnetic disks, such as any of the storage devices in any computer(s) or the like, such as may be used to implement the client device, media gateway, transcoder, etc. shown in the drawings. Volatile storage media include dynamic memory, such as main memory of such a computer platform. Tangible transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise a bus within a computer system. Carrier-wave transmission media may take the form of electric or electromagnetic signals, or acoustic or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media therefore include for example: a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD or DVD-ROM, any other optical medium, punch cards paper tape, any other physical storage medium with patterns of holes, a RAM, a PROM and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave transporting data or instructions, cables or links transporting such a carrier wave, or any other medium from which a computer may read programming code and/or data. Many of these forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution.

[0053] FIG. 5 illustrates an overall method 500 for detecting scale in a water heater and generating a scale service alert according to an exemplary embodiment of the invention. The method 500 includes several steps. The steps of the method 500 can be completed in any order, depending on particular applications or needs.

[0054] As shown at step 502, a new water heater 100 is installed.

[0055] As shown at step 504, thermostat 404 detects a call for heat, for example, when a temperature and/or a flow and/or a pressure sensed by the temperature and/or flow and/or pressure sensor is below or above a setpoint as appropriate (e.g., set by the user with a setpoint temperature knob for setting a desired setpoint temperature of the water) or prescribed temperature or flow or pressure. A call for heat may relate to the gas valve, which can have a temperature sensor (e.g., thermistor, RTD, thermocouple, etc.) that is in a shank/thermal well of the gas valve that is monitoring the water temperatures and/or a rate of change in temperature of the water. As the electro/mechanical controller(s) senses, calculates and/or gas valve sees either a temperature or a rate of change of water temperature over time, or water temperatures below a certain temperature, it can charge a solenoid to open the flow path for gas to travel through a feed and/or pilot ultimately lighting a burner in the case of a fuel-fired heat exchanger (alternatively, and electric heat exchanger can be actuated). When the electro/mechanical controller(s) starts the process of lighting a burner based on information or a signal from a temperature sensor (or electro/mechanical controller logic/device) it can be considered a call for heat.

[0056] As shown at step 506, in response to a call for heat, the water heater 100 starts heating cold water that flows through the cold water inlet 104 (FIG. 1) through the interior of the water heater 100 into the heat exchanger 102 and mixing the hot water that flows through an outlet 106 of the heat exchanger 102 into the mixing region 110. A portion of the cold water is diverted from the cold water supply inlet 104 by the bypass conduit 108 into the mixing region 110, as described above.

[0057] At step 508, after the water heater 100 reaches a steady state (e.g., flow is no longer changing and temperatures have stabilized), the controller 402 calculates an initial bypass mixing percentage %.sub.cold of water flowing through the bypass line (e.g., conduit 108) and detects the baseline position of the mixing valve 114 (e.g., when the water heating appliance was new) by counting the steps of the stepper motor 302 or by using position feedback from a position sensor (e.g., measuring directly using a resolver or another rotary electrical transformer that measures degrees of rotation, an encoder, or a positional dependent transistor based on position changes resistance through an electronic trace) configured to determine the baseline position of the mixing valve 114, for example. The controller 402 logs (e.g., saves) the initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 and the baseline position of the mixing valve 114 in the non-volatile memory of the controller 402. Because the initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 is calculated when the water heater 100 is new (e.g., no fouling or scale is present), the calculated initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 and the associated baseline position of the mixing valve 114 when bypass mixing percentage %.sub.cold is calculated are saved in the non-volatile memory of the controller 402 as a baseline feedback measurement.

[0058] For purposes of illustration, the percentage of hot or heated water (e.g., % hot or % hx) is the ratio of the water flowing through the heat source (e.g., heat exchanger 102). The sum of the percentage of hot water (e.g., % hot or % hx) and the bypass mixing percentage %.sub.cold of water flowing through the bypass line (e.g., conduit 108) is 100%, which equals the total flow through the appliance.

[0059] At step 510, the water heater 100 continues to operate and ages.

[0060] During the life of the water heater 100, the controller 402 continues to periodically monitor, at step 512, the bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 and the current position of the mixing valve 114 (e.g., by counting the steps of the stepper motor 302 or by using position feedback from a position sensor configured to determine the position of the mixing valve 114, for example).

[0061] At step 514, the controller 402 periodically and/or continuously and/or intermittently compares the current calculated bypass mixing percentage %.sub.cold of water, and/or the current position of the mixing valve 114, to the baseline feedback measurement stored in the memory of the controller 402. Step 514 determines if there is a blockage significant enough to initiate a service call. The deviation or difference between the bypass mixing percentage %.sub.cold of water and/or the current position of the mixing valve 114, and the baseline feedback measurement is therefore a criteria for determining whether or not service is necessary. If the determination in step 514 is Yes (e.g., the difference is larger than the predetermined amount or deviation or difference) the blockage criteria is met.

[0062] At step 514, the controller 402 determines whether the current calculated bypass mixing percentage %.sub.cold of water deviates from the initial bypass mixing percentage %.sub.cold of water by a pre-determined factor or whether the current position of the mixing valve 114 deviates by a pre-determined amount from the baseline feedback measurement (e.g., the baseline position of the mixing valve 114 that achieved the same bypass mixing percentage of water) stored in the memory of the controller 402.

[0063] If the current calculated bypass mixing percentage %.sub.cold of water does not deviate from the initial bypass mixing percentage %.sub.cold of water by a pre-determined factor and/or if the current position of the mixing valve 114 does not deviate by a pre-determined amount from the baseline feedback measurement (e.g., the baseline position of the mixing valve 114 that used to achieve the same bypass mixing percentage of water) stored in the memory of the controller 402 (path No after step 514), then the controller 402 continues to periodically monitor the current bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 and the current position of the mixing valve 114 and to compare these values to the baseline feedback measurement stored in the memory of the controller 402 (e.g., repeats steps 512 through 514).

[0064] If the current calculated bypass mixing percentage %.sub.cold of water deviates from the initial bypass mixing percentage %.sub.cold of water by a pre-determined factor and/or the current position of the mixing valve 114 deviates by a pre-determined amount from the baseline feedback measurement (e.g., the baseline position of the mixing valve 114 that used to achieve the same bypass mixing percentage of water) stored in the memory of the controller 402 (path Yes after step 514), in step 516, the controller 402 determines that a blockage from scale or fouling (e.g., caused by contaminant buildup) exists in at least one of the two sources of water of the water heater 100 or along the water pathway 101 within the water heater 100.

[0065] In step 518, the controller 402 generates a service alert for scale service or maintenance of the water heater 100 notifying installers or end users that the appliance needs to be cleaned.

[0066] The service alert can be, for example, an error message, a flashing light, a sound, or a push-up message or a notification to a computer, a cloud server, or a mobile device over a communication network, via a mobile device application, or a combination of thereof, for example.

[0067] The service alert can be transmitted to a computer, a cloud server, or at least one mobile device over a communications network medium, such as a wired connection, a wireless connection, or a non-wireless connection with a protocol appropriate to the communication network medium, for example. The wired connection can be Ethernet, RS485, RS232 or USB, for example. The communications protocol can include Bluetooth, Near Field Communications (NFC), WiFi, WPAN (such as ZigBee or Z-Wave), or a Radio Frequency (RF) communications protocol and/or WLAN (WiFi/802.11) protocol, long range (LoRa) or LoRaWAN protocols, RFID, Cellular, etc., for example. The connection can alternatively or additionally include an infrared or visible light communication protocol, for example.

[0068] In general, if blockage from scale buildup is detected, numerous solutions could be implemented. In one example, an alert can be output to the user or a maintenance technician. In another example, operation of the water heater 100 can be modified to compensate for the blockage, including but not limited to turning OFF of heating elements, the heat exchanger, or other heat source. For example, if blockage is detected, the power supplied to the heating elements may be terminated or reduced.

[0069] FIG. 6 illustrates a detailed method 600 for detecting scale in a water heater and generating a scale service alert according to an exemplary embodiment of the invention. The method 600 includes several steps. The steps of the method 600 can be completed in any order, depending on particular applications or needs.

[0070] As shown at step 602, thermostat 404 detects a call for heat, for example, when a temperature and/or a flow and/or a pressure sensed by the temperature and/or flow and/or pressure sensor is below or above a setpoint as appropriate (e.g., set by the user with a setpoint temperature knob for setting a desired setpoint temperature of the water) or prescribed temperature or flow or pressure. A call for heat may relate to the gas valve, which can have a temperature sensor (e.g., thermistor, RTD, thermocouple, etc.) that is in a shank/thermal well of the gas valve that is monitoring the water temperatures and the rate of change in temperature of the water. As the electro/mechanical controller(s) senses, calculates and/or gas valve sees either a temperature or a rate of change of water temperature over time, or water temperatures below a certain temperature, it can charge a solenoid to open the flow path for gas to travel through a feed and/or pilot ultimately lighting the burner. When the electro/mechanical controller(s) starts the process of lighting a burner based on information or a signal from a temperature sensor (or electro/mechanical controller logic/device) it can be considered a call for heat. Alternatively, in an embodiment of a heat pump water heater or a boiler, a call for heat may be received from an aquastat and/or a temperature sensor.

[0071] Step 602 is performed after the initial installation of the water heater 100, when the water heater 100 is new and detects a first call for heat. In embodiments in which the water heater 100 is a heat pump water heater, a boiler, or a storage tank water heater, any measurements related to the call for heat can be pre-loaded values from the manufacturer of the water heater 100.

[0072] As shown at step 604, in response to the call for heat, the water heater 100 starts heating cold water that flows through the cold water inlet 104 (FIG. 1) through the interior of the water heater 100 into the heat exchanger 102 and mixing the hot water that flows through an outlet 106 of the heat exchanger 102 into the mixing region 110. A portion of the cold water is diverted from the cold water supply inlet 104 by the bypass conduit 108 into the mixing region 110, as described above.

[0073] At step 606, after the water heater 100 reaches a steady state (e.g., flow is no longer changing and temperatures have stabilized), the controller 402 receives measurements from temperature sensors 116, 118, 120 (FIG. 1) of a first temperature T.sub.cold of the water measured at the cold water inlet 104, a second temperature T.sub.hx of the water measured at the hot water outlet 106 of the heat exchanger 102, and a third temperature T.sub.mix of the water measured at the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively.

[0074] At step 608, the controller 402 calculates an initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 based on the first temperature T.sub.cold, the second temperature T.sub.hx, and the third temperature T.sub.mix. The initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 can be calculated as the ratio of the difference between the third temperature T.sub.mix and the second temperature T.sub.hx to the difference between the first temperature T.sub.mix and the second temperature T.sub.hx. Specifically, the initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 can be calculated using the formula:

[00001]${\%}_{\mathrm{cold}}=\left(T_{\mathrm{mix}}-T_{\mathrm{hx}}\right)/\left(-T_{\mathrm{hx}}+T_{\mathrm{cold}}\right)$

[0075] This formula can be derived, for example, via substitution from the energy balance (e.g., energy in and energy out) of the mass or volume of water entering and leaving the water heater 100.

[00002]$\mathrm{Energy}\mathrm{in}={\stackrel{.}{V}}_{\mathrm{hx}}*{}_{\mathrm{hx}}*C_{p,\mathrm{hx}}*\left(460+T_{\mathrm{hx}}\right)+{\stackrel{.}{V}}_{\mathrm{cold}}*{}_{\mathrm{cold}}*C_{p,\mathrm{cold}}*\left(460+T_{\mathrm{cold}}\right)$$\mathrm{Energy}\mathrm{out}={\stackrel{.}{V}}_{\mathrm{mix}}*{}_{\mathrm{mix}}*C_{p,\mathrm{mix}}*\left(460+T_{\mathrm{mix}}\right),$ [0076] where: [0077] T.sub.n is the temperature at a position n (e.g., the first temperature T.sub.cold of the water measured at the cold water inlet 104, the second temperature T.sub.hx of the water measured at the hot water outlet 106 of the heat exchanger 102, and the third temperature T.sub.mix of the water measured at the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively); [0078] {dot over (V)}.sub.in is the volume flowrate at a position n (e.g., the first volume flowrate {dot over (V)}.sub.cold of the water measured at the cold water inlet 104, the second volume flowrate {dot over (V)}.sub.nx of the water measured at the hot water outlet 106 of the heat exchanger 102, and the third volume flowrate {dot over (V)}.sub.mix of the water measured at the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively); [0079] {dot over (V)}.sub.in is the flowrate measured upstream of the cold water split (e.g., upstream from bypass conduit 108) to the heat exchanger 102 and the mixing region 110, [0080] .sub.cold, .sub.hx, .sub.mix are the densities measured at the cold water inlet 104, the hot water outlet 106 of the heat exchanger 102, and the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively; and [0081] C.sub.p,cold, C.sub.p,hx, and C.sub.p,mix are the heat capacities measured at the cold water inlet 104, the hot water outlet 106 of the heat exchanger 102, and the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively.

[0082] The mass/volume balance can be calculated with the formula:

[00003]${\stackrel{.}{V}}_{\mathrm{mix}}={\stackrel{.}{V}}_{\mathrm{Hx}}+{\stackrel{.}{V}}_{\mathrm{cold}}\mathrm{or}1={\%}_{\mathrm{hx}}+{\%}_{\mathrm{cold}}$

[0083] The initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 can be calculated using a substitution, for example, using the following equations:

[00004]$\left(1-{\%}_{\mathrm{cold}}\right)*\left(460+T_{\mathrm{hx}}\right)+{\%}_{\mathrm{cold}}*\left(460+T_{\mathrm{cold}}\right)=\left(460+T_{\mathrm{mix}}\right)$$+T_{\mathrm{hx}}--{\%}_{\mathrm{cold}}*T_{\mathrm{hx}}++T_{\mathrm{cold}}*{\%}_{\mathrm{cold}}=+T_{\mathrm{mix}}$$T_{\mathrm{hx}}-{\%}_{\mathrm{cold}}*T_{\mathrm{hx}}+T_{\mathrm{cold}}*{\%}_{\mathrm{cold}}=T_{\mathrm{mix}}$${\%}_{\mathrm{cold}}\left(-T_{\mathrm{hx}}+T_{\mathrm{cold}}\right)=\left(T_{\mathrm{mix}}-T_{\mathrm{hx}}\right)$${\%}_{\mathrm{cold}}=\left(T_{\mathrm{mix}}-T_{\mathrm{hx}}\right)/\left(-T_{\mathrm{hx}}+T_{\mathrm{cold}}\right)$

[0084] The last formula can calculate the initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108.

[0085] Because the density and the heat capacity do not change substantially enough at temperatures between 70 F. and 140 F. to have a significant impact on the calculations, these values can be ignored for the mass balance ratio calculation. Because heat capacity has little impact in the range of operating temperatures, the heat capacity can be factored from the equation. Also, because mass is conserved in the incoming and outflowing regions, the mass can be factored out leaving only the ratios of the mass flow % cold and % hx.

[0086] Turning back to FIG. 6, at step 610, the controller 402 detects the baseline position of the mixing valve 114 (e.g., when the water heating appliance was new) by counting the steps of the stepper motor 302 or by using position feedback from a position sensor configured to determine the baseline position of the mixing valve 114, for example.

[0087] At step 612, the controller 402 associates the calculated initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 with the detected baseline position of the mixing valve 114 to obtain a baseline feedback measurement of the calculated initial bypass mixing percentage %.sub.cold of water and the associated baseline position of the mixing valve 114. Because the initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 is calculated when the water heater 100 is new (e.g., no fouling or scale is present), the calculated initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 and the associated baseline position of the mixing valve 114 when bypass mixing percentage %.sub.cold is calculated are saved in the non-volatile memory of the controller 402 as a baseline feedback measurement.

[0088] During the life of the water heater 100, the controller 402 continues to periodically monitor, for example, from signal measurements from the temperature sensors 116, 118, 120, current measurements of the first temperature T.sub.cold of the water measured at the cold water inlet 104, the second temperature T.sub.hx of the water measured at the hot water outlet 106 of the heat exchanger 102, and the third temperature T.sub.mix of the water measured at the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively.

[0089] Turning back to FIG. 6, at step 614, the controller 402 calculates the current bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 based on the current measurements of the monitored first temperature T.sub.cold, the second temperature T.sub.hx, and the third temperature T.sub.mix. The current bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 can be calculated using the formulas described above with reference to the calculations of the initial bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108. For each current bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108, the controller 402 also obtains information about the current position of the mixing valve 114 (e.g., by counting the steps of the stepper motor 302 or by using position feedback from a position sensor configured to determine the position of the mixing valve 114, for example).

[0090] At step 616, the controller 402 periodically compares the current calculated bypass mixing percentage %.sub.cold of water or the current position of the mixing valve 114 to the baseline feedback measurement stored in the memory of the controller 402.

[0091] At step 618, the controller 402 determines whether the current calculated bypass mixing percentage %.sub.cold of water deviates from the initial bypass mixing percentage %.sub.cold of water by a pre-determined factor or whether the current position of the mixing valve 114 deviates by a pre-determined amount from the baseline feedback measurement (e.g., the baseline position of the mixing valve 114 that used to achieve the same bypass mixing percentage of water) stored in the memory of the controller 402.

[0092] If the current calculated bypass mixing percentage %.sub.cold of water does not deviate from the initial bypass mixing percentage %.sub.cold of water by a pre-determined factor and/or if the current position of the mixing valve 114 does not deviate by a pre-determined amount from the baseline feedback measurement (e.g., the baseline position of the mixing valve 114 that used to achieve the same bypass mixing percentage of water) stored in the memory of the controller 402 (path No after step 618), then the controller 402 continues to periodically monitor the first temperature T.sub.cold of the water measured at the cold water inlet 104, the second temperature T.sub.hx of the water measured at the hot water outlet 106 of the heat exchanger 102, and the third temperature T.sub.mix of the water measured at the mixing outlet of the mixing region 110 or at the mixing outlet of the mixing valve 114, respectively, to calculate the current bypass mixing percentage %.sub.cold of water flowing through the bypass conduit 108 based on the monitored first temperature T.sub.cold, the second temperature T.sub.hx, and the third temperature T.sub.mix, monitor the current position of the mixing valve 114, and to periodically compare the current calculated bypass mixing percentage %.sub.cold of water and the current position of the mixing valve 114 to the baseline feedback measurement stored in the memory of the controller 402 (e.g., repeats steps 614 through 618).

[0093] If the current calculated bypass mixing percentage % cold of water deviates from the initial bypass mixing percentage % cold of water by a pre-determined factor and/or the current position of the mixing valve 114 deviates by a pre-determined amount from the baseline feedback measurement (e.g., the baseline position of the mixing valve 114 that used to achieve the same bypass mixing percentage of water) stored in the memory of the controller 402 (path Yes after step 618), or if the same position of the mixing valve 114 is detected, but a different mix ratio is found, in step 620, the controller 402 determines that a blockage from scale or fouling (e.g., caused by contaminant buildup) exists in at least one of the two sources of water of the water heater 100 or along the water pathway 101 within the water heater 100.

[0094] In step 622, the controller 402 generates a service alert for scale service or maintenance of the water heater 100 notifying installers or end users that the appliance needs to be cleaned.

[0095] The service alert can be, for example, one of more of an error message, a flashing light, a sound, or a push-up message or a notification to a computer, a cloud server, or a mobile device over a communication network, via a mobile device application, for example.

[0096] The service alert can be transmitted to a computer, a cloud server, or at least one mobile device over a communications network medium, such as a wired connection, a wireless connection, or a non-wireless connection with a protocol appropriate to the communication network medium, for example. The wired connection can be Ethernet, RS485, RS232 or USB, for example. The communications protocol can include Bluetooth, Near Field Communications, WiFi, WPAN (such as ZigBee or Z-Wave), or a Radio Frequency (RF) communications protocol and/or WLAN (WiFi/802.11) protocol, long range (LoRa) or LoRaWAN protocols, RFID, Cellular, etc., for example. The connection can include an infrared or visible light communication protocol, for example.

[0097] In general, if blockage from scale buildup is detected, numerous solutions could be implemented. In one example, an alert can be output to the user or a maintenance technician. In another example, operation of the water heater 100 can be modified to compensate for the blockage, including but not limited to turning OFF of or reducing the power of the heating elements, the heat exchanger, or other heat source. For example, if blockage is detected, the power supplied to the heating elements may be terminated. The method for detection of a blockage of the water flow from scale or fouling (e.g., caused by contaminant buildup) in a water heater described herein uses feedback related to the position of a mixing valve to detect blockages and trigger a service alert. When a new water heater is initially installed and receives its first sustained call for heat, the method uses temperature feedback (e.g., inlet temperature, outlet temperature) to calculate a mixing percentage from two sources of water (one hot and one cold), including total flowrate and the bypass percentage of water flowing through the bypass line of the water heater, and associates this feedback with the position of a mixing valve (e.g., using a stepper motor controller for counting steps or using position feedback) to obtain a baseline feedback measurement for the water heater. The baseline feedback measurement is stored in the memory of the controller of the water heater. Over time, as the water heater operates, the same feedback measurements are periodically compared to the stored in the memory baseline feedback measurements, in order to detect blockages in the hot source path and the cold source path. More specifically, when the position of the mixing valve needs to change by a pre-determined amount to achieve the same mix temperature or when the bypass percentage of water flowing through the bypass line deviates from the previously logged value by a pre-determined amount, the appliance triggers a service alert, thereby alerting the user to clean the heat exchanger or service the valve (e.g., due to fouling). Feedback related to the change in the position of the mixing valve over time as the water heater appliance ages provides a direct evidence of fouling and triggers a scale service alert when scale service is necessary, allowing the user or service personnel to timely clean the heat exchanger or service the valve, thereby increasing the service life of the appliance, ensuring optimal operation of the water heater, and ensuring efficient and improved serviceability.

[0098] In addition to the embodiments of the method described above, the scale alarm logic or method can include the following steps: [0099] (1) Appliance is installed; [0100] (2) Appliance receives its first sustained call for heat; [0101] (3) Appliance reaches steady state; [0102] (4) Appliance notes stepper position, inlet temperature, and outlet temperature; [0103] (5) ECU calculates bypass percent; [0104] (6) ECU logs bypass percent and stepper position, into non-volatile memory; [0105] (7) Appliance repeats steps 2-5 each time a sustained draw occurs until either stepper position deviates from the previously logged value by a pre-determined factor or bypass percent deviates from the previously logged value by a pre-determined factor; and [0106] (8) Appliance triggers a notification.

[0107] In another embodiment, the method can include the following steps: [0108] (1) Appliance is installed; [0109] (2) Draw occurs for >5 minutes at one flowrate (e.g., shower); [0110] (3) Control logs stepper position, total flowrate, and percentage (e.g., ratio) of the water flowing through the heat source (e.g., heat exchanger) % hx; [0111] (4) Repeat the logging of stepper position, total flowrate and percentage (e.g., ratio) of the water flowing through the heat source (e.g., heat exchanger) % hx for other total flowrates; [0112] (5) Appliance ages; [0113] (6) Appliance notices a large deviation (pre-determined) on stepper position vs percentage (e.g., ratio) of the water flowing through the heat source (e.g., heat exchanger) % hx; [0114] (7) Appliance triggers a scale service alarm.

[0115] While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.