Water heater system diagnostics

Abstract

A water heater system includes a tank storing water and a heat pump configured to heat the water. The heat pump includes a compressor that compresses a refrigerant of the heat pump, a condenser downstream of the compressor, and an expansion device downstream of the condenser that controls a pressure of the refrigerant. Sensors communicate indications of temperature. Control circuitry is configured to determine at least one operating temperature of the heat pump, determine a position command based on the at least one operating temperature, communicate the position command to the expansion device to move the expansion device, determine SST based on a first indication, determine a saturated condensing temperature SCT based on a second indication, determine a position estimate of the expansion device based on the SST and the SCT, compare the position command to the position estimate, and determine a condition based on the comparison.

Description

FIELD OF THE DISCLOSURE

[0001] The present disclosure generally relates to water heater system diagnostics and, more particularly, to control systems and methods for detecting conditions of a heat pump of a water heater system.SUMMARY OF THE DISCLOSURE

[0002] According to a first aspect of the present disclosure, a water heater system includes a tank storing water and a heat pump configured to heat the water. The heat pump includes a compressor that compresses a refrigerant of the heat pump, a condenser downstream of the compressor, and an expansion device downstream of the condenser that controls a pressure of the refrigerant. The water heater system includes a first sensor communicating a first indication of a temperature upstream of the compressor, a second sensor communicating a second indication of a temperature of the refrigerant upstream of the condenser and downstream of the compressor, and control circuitry configured to determine at least one operating temperature of the heat pump, determine a position command based on the at least one operating temperature, communicate the position command to the expansion device to adjust the expansion device, determine a saturated suction temperature (SST) based on the first indication, determine a saturated condensing temperature (SCT) based on the second indication, determine a position estimate of the expansion device based on the SST and the SCT, compare the position command to the position estimate; and determine a condition of the heat pump based on the comparison.

[0003] Embodiments of the first aspect of the present disclosure can include any one or any combination of the following features:

[0004] the determining the position estimate includes determining an inlet pressure to the expansion device based on at least one of the first indication and the second indication;

[0005] the determining the position estimate includes calculating the inlet pressure to the expansion device using a stored isentropic efficiency of the compressor, determining a pressure change across the expansion device based on the inlet pressure, calculating a flow coefficient of the expansion device based on the pressure difference, and correlating the flow coefficient with a position of the expansion device;

[0006] the comparing includes determining a difference between the position command and the position estimate;

[0007] the control circuitry is configured to receive electrical parameter data, determine a first estimate of power draw to the compressor based on the electrical parameter data, determine a second estimate of electrical power draw to the compressor based on the SST and the SCT, and compare the first estimate to the second estimate; and

[0008] the control circuitry is configured to control the water heater system based on the comparison of the first and second estimates.

[0009] According to a second aspect of the present disclosure, a heat pump water heater system includes a condenser, a compressor upstream of the condenser that compresses a refrigerant, a first sensor communicating a first indication of a temperature upstream of the compressor, a second sensor communicating a second indication of a temperature of the refrigerant upstream of the condenser and downstream of the compressor, an expansion device downstream of the condenser that controls a pressure of the refrigerant. Control circuitry configured to store a flow coefficient of the expansion device, determine, based on performance data of the compressor and the first and second indications, a coefficient estimate of the expansion device, compare the flow coefficient to the coefficient estimate, and determine a condition of a heat pump based on the comparison.

[0010] Embodiments of the second aspect of the present disclosure can include any one or any combination of the following features:

[0011] the expansion device includes an electronic expansion valve;

[0012] the electronic expansion valve is controlled via a positioning motor;

[0013] the control circuitry is configured to determine at least one operating temperature of the heat pump, and determine the position command based on the at least one operating temperature;

[0014] the control circuitry is configured to communicate the position command to the expansion device to adjust the expansion device;

[0015] the coefficient estimate corresponds to a size of an opening of the expansion device;

[0016] the control circuitry is configured to determine a saturated condensing temperature (SCT) based on the first indication and the second indication, wherein the SCT is determined without the use of a temperature sensor at the condenser;

[0017] the control circuitry is configured to calculate an inlet pressure to the expansion device using the SCT and a stored efficiency of the compressor;

[0018] the determining the coefficient estimate includes determining an inlet pressure to the expansion device based on at least one of the first indication and the second indication;

[0019] determining the coefficient estimate includes determining a pressure change across the expansion device based on the inlet pressure;

[0020] the comparing includes determining a difference between the flow coefficient and the coefficient estimate;

[0021] the control circuitry is configured to compare the difference to a threshold difference, wherein the condition is an aberrant condition determined when the difference exceeds the threshold difference; and

[0022] the control circuitry is configured to receive electrical parameter data, determine a first estimate of power draw to the compressor based on the electrical parameter data, determine a second estimate of electrical power draw to the compressor based on the SST and the SCT, compare the first estimate to the second estimate, and control the heat pump water heater based on the comparison of the first and second estimates.

[0023] According to a third aspect of the present disclosure, a method of operating a water heater system that includes a heat pump, the method includes compressing a refrigerant via a compressor, exchanging heat from a condenser of the heat pump to a tank of the water heater system, determining a position command for an expansion device based on at least one operating temperature of the heat pump to control a pressure of the refrigerant, controlling the expansion device based on the position command, determining a saturated suction temperature (SST) of the refrigerant using a temperature upstream of the compressor, determining a saturated condensing temperature (SCT) of the refrigerant using a temperature downstream of the compressor and upstream of the condenser, determining a position estimate of the expansion device based on the SST and the SCT, comparing the position command to the position estimate, and determining a condition of the heat pump based on the comparison.

[0024] These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the drawings:

[0026] FIG. 1 is a functional diagram of a water heater system;

[0027] FIG. 2 is a functional block diagram of power distribution of a water heater system;

[0028] FIG. 3 is a functional block diagram of a portion of control circuitry that performs position estimation of an expansion device and diagnostics thereof;

[0029] FIG. 4 is a pressure-enthalpy plot demonstrating temperature and pressure estimation for a heat pump water heater;

[0030] FIG. 5 is a flow diagram of a method for operating a water heater system;

[0031] FIG. 6 is a flow diagram of an estimation step of the method of FIG. 5; and

[0032] FIG. 7 is a flow diagram of a method for operating a heat pump water heater.

[0033] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles described herein.DETAILED DESCRIPTION

[0034] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0035] As used herein, the term “coupled” (in all of its forms: couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and / or any additional intermediate members. Such joining may include members being integrally formed as a single unitary body with one another (i.e., integrally coupled) or may refer to joining of two components. Such joining may be permanent in nature or may be removable or releasable in nature, unless otherwise stated.

[0036] As used herein, the terms “the,”“a,” or “an,” mean “at least one,” and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to “a component” includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0037] Referring generally to FIGS. 1-7, reference numeral 10 generally designates a water heater system. The water heater system 10 includes control circuitry 12 that controls heating systems to heat a tank 14 of the water heater system 10. For example, the water heater system 10 can include a water heater that utilizes electrical and / or refrigerant-based heating. A heat pump 16 and / or one or more resistance heating elements 18a, 18b can be provided for warming water in the tank 14 of the water heater. The control circuitry 12 can utilize sensors 20-24 and / or power detection circuitry to estimate pressures or temperatures via a heat-pump control module 26. Using one or more of these estimates, the water heater system 10 can determine a condition of the water heater system 10, such as when the estimates and other parameters of the water heater system 10 disagree, via a diagnostic module 28. The control circuitry 12 can control one or more components of the heat pump 16 based on the estimates to warm water in one or both of an upper portion 30 of the tank 14 and a lower portion 32 of the tank 14. For example, the control circuitry 12 can control at least one of a compressor 36, a condenser 38 that transfers heat to the tank 14, an expansion device 40, an evaporator 42, and a fan 44 that is controlled to draw air over the evaporator 42 to draw heat from the air to the heat pump 16. In general, the water heater system 10 can employ enhanced diagnostics for aberrant condition detection using electrical- and temperature-based detection techniques.

[0038] With continued reference to FIGS. 1-7, a water heater system 10 includes a tank 14 storing water and a heat pump 16 configured to heat the water. The heat pump 16 includes a compressor 36 that compresses a refrigerant of the heat pump 16, a condenser 38 downstream of the compressor 36, and an expansion device 40 downstream of the condenser 38 that controls a pressure of the refrigerant. The water heater system 10 includes a first sensor 20 communicating a first indication of a temperature upstream of the compressor 36, a second sensor 22 communicating a second indication of a temperature of the refrigerant upstream of the condenser 38 and downstream of the compressor 36, and control circuitry 12. The control circuitry 12 is configured to determine at least one operating temperature of the heat pump 16, determine a position command PCMD based on the at least one operating temperature, and communicate the position command PCMD to the expansion device 40 to move the expansion device 40, determine a saturated suction temperature (SST) based on the first indication, determine a saturated condensing temperature (SCT) based on the second indication, determine a position estimate PEST of the expansion device 40 based on the SST and the SCT, compare the position command PCMD to the position estimate PEST, and determine a condition of the heat pump 16 based on the comparison.

[0039] The water heater system 10 can be referred to as a heat pump water heater system when the water heater system 10 includes the heat pump 16. The water heater system 10 can alternatively be referred to as a water heater. The water heater system 10 can be configured for a commercial or residential facility. In general, the control algorithms employed herein and performed by the water heater system 10 can provide for enhanced diagnostic measures and control of the heat pump 16 using temperature- and / or electrical-based feedback. For example, the components of the heat pump 16 and / or the resistance heating elements 18a, 18b can receive power from a common circuit on which electrical current can be sensed, and the control circuitry 12 can calculate a power draw of individual components of the heat pump 16 and / or the resistance heating elements 18a, 18b using various diagnostic methods. In this way, a single current sensor can be used to determine current to the compressor 36 or other components by allocating an amount of current to various devices based on sensed electrical parameters. In some examples, the current sensor only tracks current to the heat pump 16 (e.g., the compressor 36 and / or other components of the heat pump 16). Multiple current sensors may be used and / or current feedback from the components can be determined based on the components that are powered (e.g., a compressor 36 with speed control). The system voltage can also be used by the control circuitry 12 to calculate the power draw for each component.

[0040] In general, the sensed electrical parameters can be used by the control circuitry 12 to determine an expected load, mass flow rate, or other parameters of the heat pump 16 and compare those expectations with other estimates related to heat exchange rate, coefficient of performance (COP), superheat, or other qualities of the heat pump 16 to determine aberrant conditions. Temperature-based estimates can also be used by the control circuitry 12 to provide other estimates of the same. These estimates can be compared to one another by the control circuitry 12 and / or to known values to determine an aberrant condition. In other examples, the particular diagnostic mode selected by the control circuitry 12 can be determined based on readings from one or more of the detection devices (e.g., ambient temperature, current draw). The water heater system 10 may therefore provide for multiple tests for determining which diagnostic should be used for checking aberrant conditions and for determining aberrant conditions.

[0041] Referring now to FIG. 1, one or more resistance heating elements 18a, 18b can include a first resistance heating element 18a adjacent an upper portion 30 of the tank 14 and a second heating element 18b adjacent a lower portion 32 of the tank 14. Each resistance heating element 18a, 18b is configured to heat water in the tank 14 and is mounted thereto. In the present example, the resistance heating elements 18a, 18b extend into the tank 14, though it is contemplated that the resistance heating elements 18a, 18b may operably couple to an outer surface 34 of the tank 14 to indirectly heat water in the tank 14 by heating a wall of the tank 14. The resistance heating elements 18a, 18b can be electrical elements that generate heat when an electrical current passes through the element 18a, 18b due to the resistive components of the resistance heating elements 18a, 18b. For example, the resistance heating elements 18a, 18b can be composed of metallic alloys, ceramic materials, or ceramic metals that are configured to generate heat in response to electrical current.

[0042] The heat pump 16 includes a compressor 36, a first heat exchanger 38, an expansion device 40 downstream of the first heat exchanger 38, and a second heat exchanger 42 downstream of the expansion device 40. The heat pump 16 can be configured to circulate refrigerant to heat the tank 14 and the water therein. For example, in operation, refrigerant is cycled through a closed-loop system to transfer heat. The cycle begins at the expansion device 40 (e.g., expansion valve). The expansion device 40 can be an electrically-controlled expansion device, such as a moveable expansion valve, or may be a non-adjustable device that reduces a pressure of the refrigerant. For example, the expansion device 40 can be a portion of a conduit that defines a fixed-size orifice through which the refrigerant passes and reduces in pressure. At the expansion device 40, high-pressure liquid refrigerant is throttled to a low-pressure, low-temperature state. This cooler refrigerant then enters the second heat exchanger 42 (the evaporator), where it absorbs heat from the surrounding environment via air drawn over the evaporator 42 by a fan 44. As the refrigerant absorbs this heat, it evaporates into a low-pressure vapor. The vaporized refrigerant is then drawn into the compressor 36, which increases its pressure and temperature. The high-pressure, high-temperature vapor exits the compressor 36 and flows into the condenser 38, where it releases the absorbed heat to the tank 14. As the refrigerant releases heat, it condenses back into a high-pressure liquid. This liquid then flows back to the expansion device 40, completing the cycle and allowing the process to repeat. By continuously cycling refrigerant through these components, the heat pump 16 effectively moves heat from one location (air) to another (the tank 14).

[0043] The control circuitry 12 is configured to control components of the heat pump 16 based on temperatures of the refrigerant and / or air as measured via sensors 20-24 positioned at various points of the heat pump 16, including in ambient air. For example, a first sensor 20 can be operably coupled to an entry of the evaporator 42, and a second sensor 22 operably coupled to an exit of the evaporator 42. A third sensor 24 can be operably coupled to an outlet of the compressor 36. For example, the third sensor 24 can be coupled to the heat pump 16 upstream of the condenser 38. In some examples, the third sensor 24 can be positioned at a narrow portion or a discharge portion of the compressor 36 and upstream of a wide portion of tubing that interposes the narrow portion and the condenser 38, as shown in FIG. 1. A fourth sensor 26 can be provided for measuring the temperature of air ambient to the water heater system 10, such that the control circuitry 12 can read an ambient temperature and control the water heater system 10 based on the ambient temperature.

[0044] The sensors 20-26 can be temperature sensors. In some examples, one or more of the sensors 20-26 are flow sensors, pressure sensors, or any other sensor that can communicate signals that allow the control circuitry 12 to determine temperatures at the locations of the sensors 20-26. For example, the control circuitry 12 can determine an evaporator inlet temperature TEin based on signals or indications communicated by the first sensor 20. The control circuitry 12 can determine an evaporator outlet temperature TEout based on signals or indications communicated by the second sensor 22. The control circuitry 12 can determine a compressor outlet temperature TCout based on signals or indications communicated by the third sensor 24. The control circuitry 12 can determine an ambient temperature based on signals or indications communicated by the fourth sensor 26.

[0045] For example, the control circuitry 12 can control the compressor 36 by controlling a first motor 48 that drives the compressor 36. The compressor 36 can be a constant-speed compressor. In some examples, the compressor 36 receives only an on command or not an on command (e.g., no speed input). In other examples, the compressor 36 can be controlled to a target rotational speed or power among a range of power commands. The fan 44 can also be controlled via a second motor 50 that drives the fan 44. The expansion device 40 can include an actuator 52, such as a third motor, which can be controlled via the control circuitry 12. By controlling these devices, the control circuitry 12 can execute a heat-pump control algorithm in which water in the tank 14 is heated via the heat pump 16 (e.g., heat transferred from the condenser 38 to the tank 14).

[0046] The mixing device 54 is provided for mixing water from a supply conduit 56 from a water utility (“cold water”) and heated or warmed water from the tank 14 via an output conduit 58. Accordingly, a target temperature for the tank 14 can exceed the setpoint temperature, such that a temperature of a mixture of the supply water and warmed water reaches the setpoint temperature. The mixed water can be output via a mixed water conduit 60. The temperature of the tank 14 and / or the water therein can be determined using tank temperature sensors 62a, 62b that measure temperatures adjacent the upper portion 30 and the lower portion 32, respectively. Based on the tank temperature, the control circuitry 12 can activate / deactivate the heat pump 16 and / or the resistance heating element 18a, 18b to provide the warmed water at the target temperature.

[0047] A user interface 64 can be provided in communication with the control circuitry 12 to allow user / technical personnel control of the water heater system 10 and for displaying information related to the water heater system 10. For example, the user interface 64 can include a display 66 that can indicate different diagnostic conditions, fault conditions, or operating conditions of the water heater system 10. The display 66 may be provided with the water heater system 10 or may be a display remote from the water heater system 10. By way of example, the user interface 64 can include an interface of a mobile device executing a software application that allows the water heater system 10 and the mobile device to communicate with one another. In this way, the control circuitry 12 can communicatively couple with the user interface 64 via wired or wireless (e.g., Wi-Fi, Bluetooth, etc.) communication.

[0048] The control circuitry 12 includes a controller 68 having a processor 70 and a memory 72. The memory 72 can store instructions that, when executed by the processor 70, cause the controller 68 to perform tasks related to diagnostics or control of the heat pump 16. The processor 70 may include any computing unit capable of executing instructions, such as a central processing unit (CPU), microcontroller unit (MCU), digital signal processor (DSP), application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA). The processor 70 may be a single-core or multi-core unit and can be implemented as part of a system-on-chip (SoC) or as a standalone component.

[0049] The memory 72 can include any type of storage medium capable of storing data or instructions for execution by the processor 70. This includes volatile memory, such as random-access memory (RAM), and non-volatile memory, such as read-only memory (ROM), flash memory, electrically erasable programmable read-only memory (EEPROM), or magnetic or optical storage. The memory 72 may store executable program code, configuration data, sensor readings, or any other type of information necessary for the controller 68 to perform operations related to diagnostics or control of the heat pump 16. The memory 72 and processor 70 may be integrated into a single package or exist as separate components interconnected by a bus or other communication means.

[0050] The controller 68 may be implemented as a discrete hardware device or as part of a larger system, such as a computer, embedded device, or Internet of Things (IoT) node. It may also include auxiliary components, such as communication interfaces, power management units, and analog-to-digital converters (ADCs) to interact with external devices or sensors. The processor 70 may execute firmware, software, or both, enabling the controller 68 to perform specific functions, such as processing input signals, executing control algorithms, or managing system resources for diagnostics or control of the heat pump 16.

[0051] Referring now to FIG. 2, the water heater system 10 can be supplied power via a utility, such as an electrical system for a residence or commercial setting. The electrical system can provide electricity at a standard voltage and frequency. For example, the supplied power (power in) can be 120 volts at alternating current (VAC) at a frequency of 60 Hertz (e.g., 120 VAC 60 Hz), 208 VAC 60Hz, 240 VAC 60 Hz (split phase), 230 VAC 50Hz, or any other AC supplied power (e.g., any AC voltage and frequency). In the present examples, the water heater system 10 is configured to two-phase operation at 240 VAC 180 degrees out of phase. However, it is contemplated that the water heater system 10 can be configured for a first supplied power (120 VAC), a second supplied power (240 VAC), or a third supplied power (230 VAC 50 Hz).

[0052] Referring still to FIG. 2, voltage detection circuitry 74 and current detection circuitry 76 are provided for detecting system voltage of the water heater system 10 and current to the heating system, respectively. In series with the current detection circuitry 76 are loads 78 of the heating system. The loads 78 can include components of the heat pump 16 and / or the elements 18a, 18b. A total current to the resistance heating elements 18a, 18b, and components of the heat pump 16 can be monitored separately from current to other devices of the water heater system 10. By way of example, the control circuitry 12 is not on a circuit leg common to the current detection circuitry 76 and the heating system. While demonstrated as “electrically upstream” of the heating system, it is contemplated that the current detection circuitry 76 may be located elsewhere in other examples. For instance, the current detection circuitry 76 could be located “electrically downstream” of the heating system provided the current detection circuitry 76 is on a leg common to the heating system. The current detection circuitry 76 can thus detect current drawn by the heating system. In some examples, the current detection circuitry 76 detects current only to the heating system.

[0053] With continued reference to FIG. 2, switching circuitry 80 electrically interposes power from the supplied power and the heating system, with which the switching circuitry 80 is in series. The switching circuitry 80 can be configured to interrupt high voltage signals (e.g., line voltage), neutral, or both. The control circuitry 12 is in communication with the current detection circuitry 76, the voltage detection circuitry 74, and the switching circuitry 80. For example, the current detection circuitry 76 and the voltage detection circuitry 74 may electrically couple with the control circuitry 12 via a conductor, such as a tracing of a circuit board and / or wiring, such that electrical signals may be exchanged with the control circuitry 12. In some examples, the current detection circuitry 76 and the voltage detection circuitry 74 can provide output signals on one or more conductors that electrically couple with pins of a microcontroller of the control circuitry 12. By way of example, the output signals, which are input signals to the control circuitry 12, can be a voltage and / or current that is representative of an electrical parameter. For example, the voltage detection circuitry 74 can output signals representative of the system voltage (e.g., frequency and / or magnitude), and the current detection circuitry 76 can output a signal representative of the current drawn by the heating system.

[0054] The control circuitry 12 can control the switching circuitry 80 in response to or based on the current drawn and / or the system voltage. For example, the control circuitry 12 can determine an overcurrent condition, an undercurrent condition, an overvoltage condition, an undervoltage condition, or any other electrical condition based on the signals from the current detection circuitry 76 and the voltage detection circuitry 74, and output one or more signals to control the switching circuitry 80 to open or close electrical connection between the supplied power and one or more of the loads 78. While demonstrated as a common block of switching circuitry 80 for a common block of loads 78, it is contemplated that individual portions of the switching circuitry 80 may electrically interpose supplied power and individual loads 78, such that the control circuitry 12 can selectively control the switching circuitry 80 to control power to specific loads 78 based on the current drawn and / or system voltage.

[0055] As demonstrated in FIG. 2, the “global” context of the current detection circuitry 76 (e.g., detecting current to multiple loads 78 of the heating system) combined with advanced processing techniques employed by the control circuitry 12 can allow the hardware and software to, in effect, “sense” current drawn by the individual components of the heating system. Thus, while only a “total” current drawn by the heating system as a whole may be monitored directly, as opposed to current to each load 78 being monitored directly, the advanced processing techniques and methods employed herein can allow the control circuitry 12 to determine multiple states for multiple loads 78 of the heating system on an individual basis. For example, the control circuitry 12 can logically isolate portions of the signals from one or both of the current detection circuitry 76 and the voltage detection circuitry 74 to determine parameters and / or faults or other conditions of individual loads 78 (e.g., components of the heat pump 16, one or more of the resistance heating elements 18a, 18b).

[0056] Referring now to FIGS. 3-7, details regarding heat pump 16 diagnostics are demonstrated. In general, the control circuitry 12 can determine operating conditions of the heat pump 16 using performance data about the compressor 36 and temperature and / or power input. For example, the control circuitry 12 can estimate positions, flow rates, flow coefficients, or the like by estimating pressures and / or temperatures that are not directly measured based on other measurements. With particular reference to FIG. 3, the control circuitry 12 is functionally demonstrated as including a diagnostic module 28 and a heat-pump control module 26. The control circuitry 12 can include other modules not shown, such as an electric heating control module, a mixing valve control module, etc. The heat-pump control module 26 can be executed by the control circuitry 12 to perform tasks related to control of the heat pump 16 to control superheat, COP, pressure, temperature, and overall operating parameters of the heat pump 16. While shown in reference to the expansion device 40, the heat-pump control module 26 can also control the compressor 36 and the fan 44 based on inputs from the sensors 20-26.

[0057] By way of example, signals from the first-third sensors 20-24 are processed by the control circuitry 12 in the heat-pump control module 26 to provide a first of the position estimates PEST(s) of the expansion device 40. The voltage and current detection circuitry 74, 76 also communicate signals indicative of system voltage and current drawn by the heating systems, respectively. In some examples, the signals from the current detection circuitry 76 are filtered by a current allocation module (not shown) that provides a value indicative of an amount of current drawn by the heat pump 16 or individual components thereof. Using the system voltage and current drawn, the heat-pump control module 26 can generate a second of the position estimates PEST(s). As will be described further herein, the power (e.g., the system voltage and / or the current drawn) can be used by the heat-pump control module 26 to determine parameters other than a position estimate PEST. For example, the heat-pump control module 26 can use the power to directly compare to estimated power based on at least one temperature value. Thus, in addition to providing diagnostics related to the operation of the component of the heat pump 16, the control circuitry 12 can compare the “measured power” to power as a measure of actual work done by the compressor 36, as estimated using temperature values. Based on this comparison, the control circuitry 12 can determine whether a given diagnostic method is accurate under certain conditions, as will be described further herein.

[0058] With continued reference to FIG. 3, the heat-pump control module 26 can output the command position PCMD to control the expansion device 40 via the actuator 52. The command position PCMD can also be processed by the diagnostic module 28 for comparison to one or more of the position estimates PEST(s). For example, the diagnostic module 28 can calculate a difference of the command position PCMD and one or more of the position estimates PEST(s) to determine a difference. If the difference is greater than a threshold difference, the diagnostic module 28 can output an indication (e.g., an output signal) of an aberrant condition. For example, an “expected” position of the expansion device 40, based on the previous command position PCMD(s), can be different from the position estimate(s) PEST(s), thereby indicating that the expansion device 40 may not be controlled accurately. If the command position PCMD and the position estimate(s) PEST(s) are too different (e.g., the difference exceeds the threshold difference), the control circuitry 12 can control the heat pump 16 to interrupt operation. If the difference is below the threshold difference, the control circuitry 12 can continue to operate. In some examples, operation can be interrupted when the difference is positive (e.g., the expansion device 40 is more “open” than estimated based on the command position PCMD). In some examples, operation can be interrupted when the difference is negative (e.g., the expansion device 40 is more “closed” than estimated based on the command position PCMD). Thus, the comparison can include various qualitative or quantitative comparisons for controlling the heat pump 16.

[0059] The output signal can be processed within the control circuitry 12 or outside of the control circuitry 12 to control various components of the water heater system 10. For example, the compressor 36 and the fan 44 can be deactivated based on the output signal. In another example, the water heater system 10 is controlled to an electric heating mode using the resistance heating element(s) 18a, 18b based on the output signal. It is further contemplated that the control circuitry 12 can communicate an indication to the user interface 64 and / or the display 66 to present to a user details regarding the aberrant condition. In some examples, the control circuitry 12 can determine a “lock-up” condition of the expansion device 40. For example, an aberrant condition of the expansion device 40 detected by the control circuitry 12 can include the expansion device being stuck closed, stuck open, or moving out of sync with control. The condition can be presented to the user indicating that heat pump operation is unavailable.

[0060] Referring now to FIG. 4, a pressure-enthalpy (PE) map for a target refrigerant demonstrates an exemplary saturated condensing temperature estimation process performed by the control circuitry 12 using pre-defined relationships (e.g., performance data) with power and / or temperature. The first-third sensors 20-24 are provided to allow detection of an inlet temperature of the evaporator 42, an outlet temperature of the evaporator 42, and an outlet temperature of the compressor 36, respectively. For example, the SST can be determined based on at least one of the evaporator inlet temperature TEin and the evaporator outlet temperature TEout. In one example, the evaporator inlet temperature TEin is used to determine the SST. The evaporator inlet temperature TEin and SST are on the same first isotherm I1. The SST can have a similar corresponding pressure to an evaporator outlet temperature TEout (e.g., located approximately on the same isobar). In some examples, a function of SST and evaporator outlet temperature TEout can be pre-defined or pre-programmed (e.g., via a look-up table, a function, or another data structure). The evaporator outlet temperature TEout can be determined by the control circuitry 12 based on a signal from sensor 22. The SCT can be determined based on the efficiency of the compressor 36 and the ideal isentropic compression of the heat pump 16. For example, the control circuitry 12 can determine a function of constant entropy based on the evaporator outlet temperature TEout lying on the given line of constant entropy.

[0061] With continued reference to FIG. 4, the control circuitry 12 can determine a series of pressure and enthalpy coordinates for the isotherm corresponding to the temperature TCout and determines a series of pressure and enthalpy coordinates for the isotherm corresponding to the isentropic line defined by TEout. The control circuitry 12 can determine an intersection Z at the compressor outlet temperature TCout and the line of constant entropy. The intersection Z represents the pressure and enthalpy values corresponding to an ideal system. The compressor 36 can have an isentropic efficiency of less than 100%, such that intersection Z does not represent actual pressure and enthalpy of the system. The control circuitry 12 can determine datapoints X, Y corresponding to the isentropic efficiency, with datapoint X corresponding to isentropic enthalpy h2sand datapoint Y corresponding to an estimated enthalpy h2r at the outlet of the compressor 36. The isentropic efficiency can be a proportion of 1) the isentropic enthalpy h2sless a first enthalpy h1of the system at the outlet of the evaporator 42; and 2) the estimated enthalpy h2r less the first enthalpy h1of the system. Following determination of point Y, the control circuitry 12 determines SCT using pre-defined relationships between the estimated enthalpy h2r and SCT (e.g., an isobar or another functional relationship). A second isotherm I2 is determined on which the SCT resides. Thus, the control circuitry 12, via the heat-pump control module 26, can estimate SCT without a temperature sensor at the condenser 38 itself. In some examples, the condenser 38 is provided without any sensor communicating an indication of condensing temperature or condensing pressure. In some examples, the only temperature sensors for the heat pump 16 may include the first-fourth sensors 20-26.

[0062] The SCT and the SST can allow the control circuitry 12 to determine mass flow of the compressor 36, and condensing pressure. The control circuitry 12 can process the compressor outlet temperature TCout, the mass flow, and the condensing pressure in one or more functions to determine fluid properties, such as viscosity, density, and velocity, as well as an inlet pressure to the expansion device 40.

[0063] Using the SCT and the SST, the control circuitry 12 estimates various operating conditions of the heat pump 16, such as a flow rate of refrigerant, pressures, a power draw of the compressor 36, etc. By way of example, the heat-pump control module 26 can estimate the power draw based on the SCT and SST and compare the estimated power to the calculated power draw according to electrical detection (e.g., the current and voltage detection circuitry 74, 76). The heat-pump control module 26 can also estimate the pressure at the inlet of the expansion device 40. For example, along the second isotherm I2, the pressure can be constant. However, while demonstrated as having a linear and constant relationship between points X, Y, and SCT, it is contemplated that a pre-defined relationship between points X, Y and SCT can be non-linear. The pressure at the SCT can be different than the pressure at either or both of points X and Y. The relationship between pressures at points X, Y and SCT can be programmed in the control circuitry 12.

[0064] The control circuitry 12 can calculate a change in pressure across the expansion device 40 by comparing the pressure of a first isotherm I1 to the pressure of the refrigerant on the second isotherm I2. Additionally, or alternatively, the control circuitry 12 can compare the temperature of the first isotherm I1to the temperature of the second isotherm I2 to determine a change in temperature across the expansion device 40. Using the calculated change in pressure and / or the change in temperature, the control circuitry 12 can estimate a flow coefficient and therefore a position of the expansion of the expansion device 40. Because the expansion device 40 controls the pressure, or level of pressure reduction, based on a degree of opening before the refrigerant enters the evaporator 42, the pressure change and / or temperature change is indicative of the positionof the expansion device 40. The position of the expansion device 40 can be a size (e.g., diameter, length, width, area) of an orifice defined by the expansion device 40, which can be adjustable or fixed. By way of example, the expansion device 40 can include an electronic expansion valve that controls a size of an opening through which the refrigerant moves. As described with respect to FIG. 3, the diagnostic module 28 can compare the command position PCMD to the position estimate PEST to determine an aberrant condition. The position estimate PEST can be the position estimate PEST as calculated above. In some examples, the position estimate PEST is derived based at least in part on measured electrical power, as will be described with respect to the following figures.

[0065] Referring now to FIG. 5, a method 500 for operating a water heater includes storing a command position PCMD for the expansion device 40 at 502, estimating a position of the expansion device 40 using performance data of the compressor 36 at 504, comparing the estimate to the stored position at 506, and determining a condition of the expansion device 40 based on the comparison at 508. For example, the control circuitry 12 can determine the position estimate PEST as previously described or provide a different position estimate PEST. The command position PCMD can be a command position PCMD previously communicated to the actuator 52. In some examples, the control circuitry 12 can compare the position estimate PEST to an expected size of a fixed-size orifice in examples in which the expansion device 40 is non-adjustable (e.g., non-motorized). By way of example, the command position PCMD can include increments or absolute position command values communicated via a pulse-width modulated (PWM) signal or any other signal that includes a target position. For example, the command position PCMD can be an actual value representative of a position in a range of motion of the actuator 52 or be an increment or decrement from an existing position. In the example in which the command position PCMD is an increment, decrement, or adjustment, the diagnostic module 28 can store a variable representative of an “expected” position of the valve that is adjusted based on the adjustment. Thus, the command position PCMD can be a signal indicative of a + / - number of steps.

[0066] The actuator 52 can be a motor, such as a positioning motor, which adjusts incrementally in response to a command. For example, the motor can be a stepper motor or a servo motor. The temperature and / or electrical power measurements of the water heater system 10 can generally allow the motor to omit a feedback mechanism, such as an encoder or other feedback provided via servo control. By tracking the command position PCMD and comparing it to the position estimate(s) PEST(s), the control circuitry 12 can provide feedback for diagnostic detection.

[0067] In some examples, the method 500 can alternatively compare an expected flow coefficient to an estimated flow coefficient (or coefficient estimate). In such examples, rather than correlating the flow coefficient and the coefficient estimate to position data, the comparison is carried out between the coefficient data. Based on this comparison, the heat pump 16 can be controlled in a similar way to position-based control. By way of example, the coefficient-based comparison method can be utilized for use with systems having non-adjustable expansion devices. When the expansion device 40 is a fixed-size orifice device (e.g., a capillary tube), the method 500 can thus be applied by detecting a difference between the coefficient estimate (estimated based on the measured temperatures and / or electrical parameters as described herein) to a stored flow coefficient that corresponds to the qualities of the fixed-size orifice device. For example, the stored flow coefficient can be pre-programmed based on the qualities of the non-adjustable valve (e.g., a non-motorized valve). Such comparisons can alternatively be applied to variable-size orifice devices, such as an expansion device 40 incorporating an electronic expansion valve. In this way, the algorithms of the present disclosure can be applied to expansion devices 40 having fixed- or variable-size orifices.

[0068] Referring now to FIG. 6, step 504 of method 500 can provide for various position estimate(s) PEST(s). In a first estimation method 600a, the electrical power to the compressor 36 is measured at 602a. For example, the current drawn and the system voltage can be detected by the detection circuitry 74, 76 and received by control circuitry 12. In a second estimation method 600b, the evaporator outlet temperature TEout and the compressor outlet temperature TCout are measured as previously described at 602b. Each estimation method 600a, 600b utilizes the evaporator inlet temperature TEin at 604, calculates the SST at 606, and calculates the condensing pressure and the SCT using performance data of the compressor 36 at 608 / 610. For example, the performance data can include electrical currents mapped to power draw and mass flow rates, thereby being mapped to the SCT. In the second estimation method 600b, the control circuity 12 can estimate the condensing pressure and the SCT using the technique previously described with respect to the isentropic compression (e.g., the example of FIG. 3). At step 610, the condensing pressure is determined.

[0069] Using the condensing pressure, a pressure at the inlet of the expansion device 40 is determined at 612. At 614, the pressure change across the expansion device 40 is estimated based on the inlet pressure. Determining the pressure change across the expansion device 40 can be performed based further on fluid properties into and out of the expansion device 40. For example, the control circuitry 12 can determine mass flow and / or other fluid properties at the inlet of the expansion device 40 based on SCT and SST. Using mass flow, condensing pressure, and the compressor outlet temperature TCout, the control circuitry 12 can estimate starting density, viscosity, and / or other qualities of the refrigerant. The control circuitry 12 can estimate an approximate location in the condenser 38 where condensation begins. With regard to the outlet pressure of the expansion device 40, the control circuitry 12 can utilize the evaporator inlet temperature TEin to determine the outlet pressure of the expansion device 40 (e.g., the pressure along the second isotherm I2). At 616, the flow coefficient through the expansion device 40 is calculated based on a pressure difference across the expansion device 40. The flow coefficient can be determined based further on the qualities of the fluid at an inlet of the expansion device 40 and at an outlet of the expansion device 40 (e.g., viscosity, density, pressure, temperature). For example, the control circuitry 12 can utilize a look-up table or other database to determine the flow coefficient associated with a given pressure change. At step 618, the flow coefficient is correlated with the position estimate PEST. For example, the control circuitry 12 can interact with a data structure, such as a look-up table, to determine the position estimate PEST.

[0070] The second estimation method 600b can also include estimating power as a function of SST and SCT (as calculated using step 602b) at 602c. For example, an expected compressor 36 power to achieve the temperatures read by the sensors 20-24 can be calculated using the efficiency or other performance metrics of the compressor 36. At 604d, the second estimation method 600b can perform various controls of the water heater system 10, such as continuing to steps 506 and 508. In other examples, the power estimate is compared to the measured power (e.g., as calculated at step 602a). If the control circuitry 12 determines a discrepancy between the two power levels, the diagnostic module 28 can determine an aberrant condition. Similar to the position error of the expansion device 40, the discrepancy can be compared to a threshold, as small errors between the estimates can be expected and differentiated from large aberrancies by the control circuitry 12. In some examples, the control circuitry 12 selects between the first estimation method 600a and the second estimation method 600b depending on other factors. In some examples when the discrepancy exceeds the threshold discrepancy tolerance, the diagnostic method is withheld. For example, the control circuitry 12 can selectively execute the diagnostic algorithm based on expected accuracy.

[0071] In some examples, a power estimate using electrical detection (e.g., the current and voltage detection circuitry 74, 76) can be compared to a power estimate that uses temperatures. For example, the method 500 can include determining an estimate of SCT (electrical-based SCT estimate) based on electrical power of the compressor 36, and comparing the compressor outlet temperature TCout, to the electrical-based SCT estimate. If the electrical-based SCT estimate is not less than the compressor outlet temperature TCout by at least a threshold value (e.g., 10°F, 5°F, 2°F), the control circuitry 12 can determine an aberrant condition and / or interrupt operation of the heat pump 16.

[0072] Referring now to FIG. 7, a method 700 of operating a water heater system 10 that includes a heat pump 16 includes compressing a refrigerant via a compressor 36 at 702, exchanging heat from a condenser 38 of the heat pump 16 to a tank 14 of the water heater system 10 at 704, determining a position command PCMD for an expansion device 40 based on at least one operating temperature of the heat pump 16 to control a pressure of the refrigerant at 706, controlling the expansion device 40 based on the position command PCMD at 708, determining a saturated suction temperature (SST) of the refrigerant using a temperature upstream of the compressor 36 at 710, determining a saturated condensing temperature (SCT) of the refrigerant using a temperature downstream of the compressor 36 and upstream of the condenser 38 at 712, determining a position estimate PEST of the expansion device 40 based on the SST and the SCT at 714, comparing the position command PCMD to the position estimate PEST at 716, and determining a condition of the heat pump 16 based on the comparison at 718. By way of example, the components / circuitry described herein can be used to perform the method 700.

[0073] In general, the systems and methods described herein can perform enhanced diagnostics for operating a water heater system 10. For example, enhanced control and fault detection can be provided without a temperature sensor on at least one of the heat exchangers 38, 42. The feedback that may be provided via a robust diagnostic algorithm and heat-pump control algorithm can allow for the omission of feedback devices, such as encoders, for the expansion device 40. The feedback can also provide robust aberrancy detection when in use with non-adjustable expansion devices.

Examples

Embodiment Construction

[0034]As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0035]As used herein, the term “coupled” (in all of its forms: couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and / or any additional intermediate members. Such joining may include members being integrally formed as a single unitary body with one another (i.e., integrally coupled) or may refer to...

FIELD OF THE DISCLOSURE

[0001] The present disclosure generally relates to water heater system diagnostics and, more particularly, to control systems and methods for detecting conditions of a heat pump of a water heater system.SUMMARY OF THE DISCLOSURE

[0002] According to a first aspect of the present disclosure, a water heater system includes a tank storing water and a heat pump configured to heat the water. The heat pump includes a compressor that compresses a refrigerant of the heat pump, a condenser downstream of the compressor, and an expansion device downstream of the condenser that controls a pressure of the refrigerant. The water heater system includes a first sensor communicating a first indication of a temperature upstream of the compressor, a second sensor communicating a second indication of a temperature of the refrigerant upstream of the condenser and downstream of the compressor, and control circuitry configured to determine at least one operating temperature of the heat pump, determine a position command based on the at least one operating temperature, communicate the position command to the expansion device to adjust the expansion device, determine a saturated suction temperature (SST) based on the first indication, determine a saturated condensing temperature (SCT) based on the second indication, determine a position estimate of the expansion device based on the SST and the SCT, compare the position command to the position estimate; and determine a condition of the heat pump based on the comparison.

[0003] Embodiments of the first aspect of the present disclosure can include any one or any combination of the following features:

[0004] the determining the position estimate includes determining an inlet pressure to the expansion device based on at least one of the first indication and the second indication;

[0005] the determining the position estimate includes calculating the inlet pressure to the expansion device using a stored isentropic efficiency of the compressor, determining a pressure change across the expansion device based on the inlet pressure, calculating a flow coefficient of the expansion device based on the pressure difference, and correlating the flow coefficient with a position of the expansion device;

[0006] the comparing includes determining a difference between the position command and the position estimate;

[0007] the control circuitry is configured to receive electrical parameter data, determine a first estimate of power draw to the compressor based on the electrical parameter data, determine a second estimate of electrical power draw to the compressor based on the SST and the SCT, and compare the first estimate to the second estimate; and

[0008] the control circuitry is configured to control the water heater system based on the comparison of the first and second estimates.

[0009] According to a second aspect of the present disclosure, a heat pump water heater system includes a condenser, a compressor upstream of the condenser that compresses a refrigerant, a first sensor communicating a first indication of a temperature upstream of the compressor, a second sensor communicating a second indication of a temperature of the refrigerant upstream of the condenser and downstream of the compressor, an expansion device downstream of the condenser that controls a pressure of the refrigerant. Control circuitry configured to store a flow coefficient of the expansion device, determine, based on performance data of the compressor and the first and second indications, a coefficient estimate of the expansion device, compare the flow coefficient to the coefficient estimate, and determine a condition of a heat pump based on the comparison.

[0010] Embodiments of the second aspect of the present disclosure can include any one or any combination of the following features:

[0011] the expansion device includes an electronic expansion valve;

[0012] the electronic expansion valve is controlled via a positioning motor;

[0013] the control circuitry is configured to determine at least one operating temperature of the heat pump, and determine the position command based on the at least one operating temperature;

[0014] the control circuitry is configured to communicate the position command to the expansion device to adjust the expansion device;

[0015] the coefficient estimate corresponds to a size of an opening of the expansion device;

[0016] the control circuitry is configured to determine a saturated condensing temperature (SCT) based on the first indication and the second indication, wherein the SCT is determined without the use of a temperature sensor at the condenser;

[0017] the control circuitry is configured to calculate an inlet pressure to the expansion device using the SCT and a stored efficiency of the compressor;

[0018] the determining the coefficient estimate includes determining an inlet pressure to the expansion device based on at least one of the first indication and the second indication;

[0019] determining the coefficient estimate includes determining a pressure change across the expansion device based on the inlet pressure;

[0020] the comparing includes determining a difference between the flow coefficient and the coefficient estimate;

[0021] the control circuitry is configured to compare the difference to a threshold difference, wherein the condition is an aberrant condition determined when the difference exceeds the threshold difference; and

[0022] the control circuitry is configured to receive electrical parameter data, determine a first estimate of power draw to the compressor based on the electrical parameter data, determine a second estimate of electrical power draw to the compressor based on the SST and the SCT, compare the first estimate to the second estimate, and control the heat pump water heater based on the comparison of the first and second estimates.

[0023] According to a third aspect of the present disclosure, a method of operating a water heater system that includes a heat pump, the method includes compressing a refrigerant via a compressor, exchanging heat from a condenser of the heat pump to a tank of the water heater system, determining a position command for an expansion device based on at least one operating temperature of the heat pump to control a pressure of the refrigerant, controlling the expansion device based on the position command, determining a saturated suction temperature (SST) of the refrigerant using a temperature upstream of the compressor, determining a saturated condensing temperature (SCT) of the refrigerant using a temperature downstream of the compressor and upstream of the condenser, determining a position estimate of the expansion device based on the SST and the SCT, comparing the position command to the position estimate, and determining a condition of the heat pump based on the comparison.

[0024] These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the drawings:

[0026] FIG. 1 is a functional diagram of a water heater system;

[0027] FIG. 2 is a functional block diagram of power distribution of a water heater system;

[0028] FIG. 3 is a functional block diagram of a portion of control circuitry that performs position estimation of an expansion device and diagnostics thereof;

[0029] FIG. 4 is a pressure-enthalpy plot demonstrating temperature and pressure estimation for a heat pump water heater;

[0030] FIG. 5 is a flow diagram of a method for operating a water heater system;

[0031] FIG. 6 is a flow diagram of an estimation step of the method of FIG. 5; and

[0032] FIG. 7 is a flow diagram of a method for operating a heat pump water heater.

[0033] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles described herein.DETAILED DESCRIPTION

[0034] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0035] As used herein, the term “coupled” (in all of its forms: couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and / or any additional intermediate members. Such joining may include members being integrally formed as a single unitary body with one another (i.e., integrally coupled) or may refer to joining of two components. Such joining may be permanent in nature or may be removable or releasable in nature, unless otherwise stated.

[0036] As used herein, the terms “the,”“a,” or “an,” mean “at least one,” and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to “a component” includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0037] Referring generally to FIGS. 1-7, reference numeral 10 generally designates a water heater system. The water heater system 10 includes control circuitry 12 that controls heating systems to heat a tank 14 of the water heater system 10. For example, the water heater system 10 can include a water heater that utilizes electrical and / or refrigerant-based heating. A heat pump 16 and / or one or more resistance heating elements 18a, 18b can be provided for warming water in the tank 14 of the water heater. The control circuitry 12 can utilize sensors 20-24 and / or power detection circuitry to estimate pressures or temperatures via a heat-pump control module 26. Using one or more of these estimates, the water heater system 10 can determine a condition of the water heater system 10, such as when the estimates and other parameters of the water heater system 10 disagree, via a diagnostic module 28. The control circuitry 12 can control one or more components of the heat pump 16 based on the estimates to warm water in one or both of an upper portion 30 of the tank 14 and a lower portion 32 of the tank 14. For example, the control circuitry 12 can control at least one of a compressor 36, a condenser 38 that transfers heat to the tank 14, an expansion device 40, an evaporator 42, and a fan 44 that is controlled to draw air over the evaporator 42 to draw heat from the air to the heat pump 16. In general, the water heater system 10 can employ enhanced diagnostics for aberrant condition detection using electrical- and temperature-based detection techniques.

[0038] With continued reference to FIGS. 1-7, a water heater system 10 includes a tank 14 storing water and a heat pump 16 configured to heat the water. The heat pump 16 includes a compressor 36 that compresses a refrigerant of the heat pump 16, a condenser 38 downstream of the compressor 36, and an expansion device 40 downstream of the condenser 38 that controls a pressure of the refrigerant. The water heater system 10 includes a first sensor 20 communicating a first indication of a temperature upstream of the compressor 36, a second sensor 22 communicating a second indication of a temperature of the refrigerant upstream of the condenser 38 and downstream of the compressor 36, and control circuitry 12. The control circuitry 12 is configured to determine at least one operating temperature of the heat pump 16, determine a position command PCMD based on the at least one operating temperature, and communicate the position command PCMD to the expansion device 40 to move the expansion device 40, determine a saturated suction temperature (SST) based on the first indication, determine a saturated condensing temperature (SCT) based on the second indication, determine a position estimate PEST of the expansion device 40 based on the SST and the SCT, compare the position command PCMD to the position estimate PEST, and determine a condition of the heat pump 16 based on the comparison.

[0039] The water heater system 10 can be referred to as a heat pump water heater system when the water heater system 10 includes the heat pump 16. The water heater system 10 can alternatively be referred to as a water heater. The water heater system 10 can be configured for a commercial or residential facility. In general, the control algorithms employed herein and performed by the water heater system 10 can provide for enhanced diagnostic measures and control of the heat pump 16 using temperature- and / or electrical-based feedback. For example, the components of the heat pump 16 and / or the resistance heating elements 18a, 18b can receive power from a common circuit on which electrical current can be sensed, and the control circuitry 12 can calculate a power draw of individual components of the heat pump 16 and / or the resistance heating elements 18a, 18b using various diagnostic methods. In this way, a single current sensor can be used to determine current to the compressor 36 or other components by allocating an amount of current to various devices based on sensed electrical parameters. In some examples, the current sensor only tracks current to the heat pump 16 (e.g., the compressor 36 and / or other components of the heat pump 16). Multiple current sensors may be used and / or current feedback from the components can be determined based on the components that are powered (e.g., a compressor 36 with speed control). The system voltage can also be used by the control circuitry 12 to calculate the power draw for each component.

[0040] In general, the sensed electrical parameters can be used by the control circuitry 12 to determine an expected load, mass flow rate, or other parameters of the heat pump 16 and compare those expectations with other estimates related to heat exchange rate, coefficient of performance (COP), superheat, or other qualities of the heat pump 16 to determine aberrant conditions. Temperature-based estimates can also be used by the control circuitry 12 to provide other estimates of the same. These estimates can be compared to one another by the control circuitry 12 and / or to known values to determine an aberrant condition. In other examples, the particular diagnostic mode selected by the control circuitry 12 can be determined based on readings from one or more of the detection devices (e.g., ambient temperature, current draw). The water heater system 10 may therefore provide for multiple tests for determining which diagnostic should be used for checking aberrant conditions and for determining aberrant conditions.

[0041] Referring now to FIG. 1, one or more resistance heating elements 18a, 18b can include a first resistance heating element 18a adjacent an upper portion 30 of the tank 14 and a second heating element 18b adjacent a lower portion 32 of the tank 14. Each resistance heating element 18a, 18b is configured to heat water in the tank 14 and is mounted thereto. In the present example, the resistance heating elements 18a, 18b extend into the tank 14, though it is contemplated that the resistance heating elements 18a, 18b may operably couple to an outer surface 34 of the tank 14 to indirectly heat water in the tank 14 by heating a wall of the tank 14. The resistance heating elements 18a, 18b can be electrical elements that generate heat when an electrical current passes through the element 18a, 18b due to the resistive components of the resistance heating elements 18a, 18b. For example, the resistance heating elements 18a, 18b can be composed of metallic alloys, ceramic materials, or ceramic metals that are configured to generate heat in response to electrical current.

[0042] The heat pump 16 includes a compressor 36, a first heat exchanger 38, an expansion device 40 downstream of the first heat exchanger 38, and a second heat exchanger 42 downstream of the expansion device 40. The heat pump 16 can be configured to circulate refrigerant to heat the tank 14 and the water therein. For example, in operation, refrigerant is cycled through a closed-loop system to transfer heat. The cycle begins at the expansion device 40 (e.g., expansion valve). The expansion device 40 can be an electrically-controlled expansion device, such as a moveable expansion valve, or may be a non-adjustable device that reduces a pressure of the refrigerant. For example, the expansion device 40 can be a portion of a conduit that defines a fixed-size orifice through which the refrigerant passes and reduces in pressure. At the expansion device 40, high-pressure liquid refrigerant is throttled to a low-pressure, low-temperature state. This cooler refrigerant then enters the second heat exchanger 42 (the evaporator), where it absorbs heat from the surrounding environment via air drawn over the evaporator 42 by a fan 44. As the refrigerant absorbs this heat, it evaporates into a low-pressure vapor. The vaporized refrigerant is then drawn into the compressor 36, which increases its pressure and temperature. The high-pressure, high-temperature vapor exits the compressor 36 and flows into the condenser 38, where it releases the absorbed heat to the tank 14. As the refrigerant releases heat, it condenses back into a high-pressure liquid. This liquid then flows back to the expansion device 40, completing the cycle and allowing the process to repeat. By continuously cycling refrigerant through these components, the heat pump 16 effectively moves heat from one location (air) to another (the tank 14).

[0043] The control circuitry 12 is configured to control components of the heat pump 16 based on temperatures of the refrigerant and / or air as measured via sensors 20-24 positioned at various points of the heat pump 16, including in ambient air. For example, a first sensor 20 can be operably coupled to an entry of the evaporator 42, and a second sensor 22 operably coupled to an exit of the evaporator 42. A third sensor 24 can be operably coupled to an outlet of the compressor 36. For example, the third sensor 24 can be coupled to the heat pump 16 upstream of the condenser 38. In some examples, the third sensor 24 can be positioned at a narrow portion or a discharge portion of the compressor 36 and upstream of a wide portion of tubing that interposes the narrow portion and the condenser 38, as shown in FIG. 1. A fourth sensor 26 can be provided for measuring the temperature of air ambient to the water heater system 10, such that the control circuitry 12 can read an ambient temperature and control the water heater system 10 based on the ambient temperature.

[0044] The sensors 20-26 can be temperature sensors. In some examples, one or more of the sensors 20-26 are flow sensors, pressure sensors, or any other sensor that can communicate signals that allow the control circuitry 12 to determine temperatures at the locations of the sensors 20-26. For example, the control circuitry 12 can determine an evaporator inlet temperature TEin based on signals or indications communicated by the first sensor 20. The control circuitry 12 can determine an evaporator outlet temperature TEout based on signals or indications communicated by the second sensor 22. The control circuitry 12 can determine a compressor outlet temperature TCout based on signals or indications communicated by the third sensor 24. The control circuitry 12 can determine an ambient temperature based on signals or indications communicated by the fourth sensor 26.

[0045] For example, the control circuitry 12 can control the compressor 36 by controlling a first motor 48 that drives the compressor 36. The compressor 36 can be a constant-speed compressor. In some examples, the compressor 36 receives only an on command or not an on command (e.g., no speed input). In other examples, the compressor 36 can be controlled to a target rotational speed or power among a range of power commands. The fan 44 can also be controlled via a second motor 50 that drives the fan 44. The expansion device 40 can include an actuator 52, such as a third motor, which can be controlled via the control circuitry 12. By controlling these devices, the control circuitry 12 can execute a heat-pump control algorithm in which water in the tank 14 is heated via the heat pump 16 (e.g., heat transferred from the condenser 38 to the tank 14).

[0046] The mixing device 54 is provided for mixing water from a supply conduit 56 from a water utility (“cold water”) and heated or warmed water from the tank 14 via an output conduit 58. Accordingly, a target temperature for the tank 14 can exceed the setpoint temperature, such that a temperature of a mixture of the supply water and warmed water reaches the setpoint temperature. The mixed water can be output via a mixed water conduit 60. The temperature of the tank 14 and / or the water therein can be determined using tank temperature sensors 62a, 62b that measure temperatures adjacent the upper portion 30 and the lower portion 32, respectively. Based on the tank temperature, the control circuitry 12 can activate / deactivate the heat pump 16 and / or the resistance heating element 18a, 18b to provide the warmed water at the target temperature.

[0047] A user interface 64 can be provided in communication with the control circuitry 12 to allow user / technical personnel control of the water heater system 10 and for displaying information related to the water heater system 10. For example, the user interface 64 can include a display 66 that can indicate different diagnostic conditions, fault conditions, or operating conditions of the water heater system 10. The display 66 may be provided with the water heater system 10 or may be a display remote from the water heater system 10. By way of example, the user interface 64 can include an interface of a mobile device executing a software application that allows the water heater system 10 and the mobile device to communicate with one another. In this way, the control circuitry 12 can communicatively couple with the user interface 64 via wired or wireless (e.g., Wi-Fi, Bluetooth, etc.) communication.

[0048] The control circuitry 12 includes a controller 68 having a processor 70 and a memory 72. The memory 72 can store instructions that, when executed by the processor 70, cause the controller 68 to perform tasks related to diagnostics or control of the heat pump 16. The processor 70 may include any computing unit capable of executing instructions, such as a central processing unit (CPU), microcontroller unit (MCU), digital signal processor (DSP), application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA). The processor 70 may be a single-core or multi-core unit and can be implemented as part of a system-on-chip (SoC) or as a standalone component.

[0049] The memory 72 can include any type of storage medium capable of storing data or instructions for execution by the processor 70. This includes volatile memory, such as random-access memory (RAM), and non-volatile memory, such as read-only memory (ROM), flash memory, electrically erasable programmable read-only memory (EEPROM), or magnetic or optical storage. The memory 72 may store executable program code, configuration data, sensor readings, or any other type of information necessary for the controller 68 to perform operations related to diagnostics or control of the heat pump 16. The memory 72 and processor 70 may be integrated into a single package or exist as separate components interconnected by a bus or other communication means.

[0050] The controller 68 may be implemented as a discrete hardware device or as part of a larger system, such as a computer, embedded device, or Internet of Things (IoT) node. It may also include auxiliary components, such as communication interfaces, power management units, and analog-to-digital converters (ADCs) to interact with external devices or sensors. The processor 70 may execute firmware, software, or both, enabling the controller 68 to perform specific functions, such as processing input signals, executing control algorithms, or managing system resources for diagnostics or control of the heat pump 16.

[0051] Referring now to FIG. 2, the water heater system 10 can be supplied power via a utility, such as an electrical system for a residence or commercial setting. The electrical system can provide electricity at a standard voltage and frequency. For example, the supplied power (power in) can be 120 volts at alternating current (VAC) at a frequency of 60 Hertz (e.g., 120 VAC 60 Hz), 208 VAC 60Hz, 240 VAC 60 Hz (split phase), 230 VAC 50Hz, or any other AC supplied power (e.g., any AC voltage and frequency). In the present examples, the water heater system 10 is configured to two-phase operation at 240 VAC 180 degrees out of phase. However, it is contemplated that the water heater system 10 can be configured for a first supplied power (120 VAC), a second supplied power (240 VAC), or a third supplied power (230 VAC 50 Hz).

[0052] Referring still to FIG. 2, voltage detection circuitry 74 and current detection circuitry 76 are provided for detecting system voltage of the water heater system 10 and current to the heating system, respectively. In series with the current detection circuitry 76 are loads 78 of the heating system. The loads 78 can include components of the heat pump 16 and / or the elements 18a, 18b. A total current to the resistance heating elements 18a, 18b, and components of the heat pump 16 can be monitored separately from current to other devices of the water heater system 10. By way of example, the control circuitry 12 is not on a circuit leg common to the current detection circuitry 76 and the heating system. While demonstrated as “electrically upstream” of the heating system, it is contemplated that the current detection circuitry 76 may be located elsewhere in other examples. For instance, the current detection circuitry 76 could be located “electrically downstream” of the heating system provided the current detection circuitry 76 is on a leg common to the heating system. The current detection circuitry 76 can thus detect current drawn by the heating system. In some examples, the current detection circuitry 76 detects current only to the heating system.

[0053] With continued reference to FIG. 2, switching circuitry 80 electrically interposes power from the supplied power and the heating system, with which the switching circuitry 80 is in series. The switching circuitry 80 can be configured to interrupt high voltage signals (e.g., line voltage), neutral, or both. The control circuitry 12 is in communication with the current detection circuitry 76, the voltage detection circuitry 74, and the switching circuitry 80. For example, the current detection circuitry 76 and the voltage detection circuitry 74 may electrically couple with the control circuitry 12 via a conductor, such as a tracing of a circuit board and / or wiring, such that electrical signals may be exchanged with the control circuitry 12. In some examples, the current detection circuitry 76 and the voltage detection circuitry 74 can provide output signals on one or more conductors that electrically couple with pins of a microcontroller of the control circuitry 12. By way of example, the output signals, which are input signals to the control circuitry 12, can be a voltage and / or current that is representative of an electrical parameter. For example, the voltage detection circuitry 74 can output signals representative of the system voltage (e.g., frequency and / or magnitude), and the current detection circuitry 76 can output a signal representative of the current drawn by the heating system.

[0054] The control circuitry 12 can control the switching circuitry 80 in response to or based on the current drawn and / or the system voltage. For example, the control circuitry 12 can determine an overcurrent condition, an undercurrent condition, an overvoltage condition, an undervoltage condition, or any other electrical condition based on the signals from the current detection circuitry 76 and the voltage detection circuitry 74, and output one or more signals to control the switching circuitry 80 to open or close electrical connection between the supplied power and one or more of the loads 78. While demonstrated as a common block of switching circuitry 80 for a common block of loads 78, it is contemplated that individual portions of the switching circuitry 80 may electrically interpose supplied power and individual loads 78, such that the control circuitry 12 can selectively control the switching circuitry 80 to control power to specific loads 78 based on the current drawn and / or system voltage.

[0055] As demonstrated in FIG. 2, the “global” context of the current detection circuitry 76 (e.g., detecting current to multiple loads 78 of the heating system) combined with advanced processing techniques employed by the control circuitry 12 can allow the hardware and software to, in effect, “sense” current drawn by the individual components of the heating system. Thus, while only a “total” current drawn by the heating system as a whole may be monitored directly, as opposed to current to each load 78 being monitored directly, the advanced processing techniques and methods employed herein can allow the control circuitry 12 to determine multiple states for multiple loads 78 of the heating system on an individual basis. For example, the control circuitry 12 can logically isolate portions of the signals from one or both of the current detection circuitry 76 and the voltage detection circuitry 74 to determine parameters and / or faults or other conditions of individual loads 78 (e.g., components of the heat pump 16, one or more of the resistance heating elements 18a, 18b).

[0056] Referring now to FIGS. 3-7, details regarding heat pump 16 diagnostics are demonstrated. In general, the control circuitry 12 can determine operating conditions of the heat pump 16 using performance data about the compressor 36 and temperature and / or power input. For example, the control circuitry 12 can estimate positions, flow rates, flow coefficients, or the like by estimating pressures and / or temperatures that are not directly measured based on other measurements. With particular reference to FIG. 3, the control circuitry 12 is functionally demonstrated as including a diagnostic module 28 and a heat-pump control module 26. The control circuitry 12 can include other modules not shown, such as an electric heating control module, a mixing valve control module, etc. The heat-pump control module 26 can be executed by the control circuitry 12 to perform tasks related to control of the heat pump 16 to control superheat, COP, pressure, temperature, and overall operating parameters of the heat pump 16. While shown in reference to the expansion device 40, the heat-pump control module 26 can also control the compressor 36 and the fan 44 based on inputs from the sensors 20-26.

[0057] By way of example, signals from the first-third sensors 20-24 are processed by the control circuitry 12 in the heat-pump control module 26 to provide a first of the position estimates PEST(s) of the expansion device 40. The voltage and current detection circuitry 74, 76 also communicate signals indicative of system voltage and current drawn by the heating systems, respectively. In some examples, the signals from the current detection circuitry 76 are filtered by a current allocation module (not shown) that provides a value indicative of an amount of current drawn by the heat pump 16 or individual components thereof. Using the system voltage and current drawn, the heat-pump control module 26 can generate a second of the position estimates PEST(s). As will be described further herein, the power (e.g., the system voltage and / or the current drawn) can be used by the heat-pump control module 26 to determine parameters other than a position estimate PEST. For example, the heat-pump control module 26 can use the power to directly compare to estimated power based on at least one temperature value. Thus, in addition to providing diagnostics related to the operation of the component of the heat pump 16, the control circuitry 12 can compare the “measured power” to power as a measure of actual work done by the compressor 36, as estimated using temperature values. Based on this comparison, the control circuitry 12 can determine whether a given diagnostic method is accurate under certain conditions, as will be described further herein.

[0058] With continued reference to FIG. 3, the heat-pump control module 26 can output the command position PCMD to control the expansion device 40 via the actuator 52. The command position PCMD can also be processed by the diagnostic module 28 for comparison to one or more of the position estimates PEST(s). For example, the diagnostic module 28 can calculate a difference of the command position PCMD and one or more of the position estimates PEST(s) to determine a difference. If the difference is greater than a threshold difference, the diagnostic module 28 can output an indication (e.g., an output signal) of an aberrant condition. For example, an “expected” position of the expansion device 40, based on the previous command position PCMD(s), can be different from the position estimate(s) PEST(s), thereby indicating that the expansion device 40 may not be controlled accurately. If the command position PCMD and the position estimate(s) PEST(s) are too different (e.g., the difference exceeds the threshold difference), the control circuitry 12 can control the heat pump 16 to interrupt operation. If the difference is below the threshold difference, the control circuitry 12 can continue to operate. In some examples, operation can be interrupted when the difference is positive (e.g., the expansion device 40 is more “open” than estimated based on the command position PCMD). In some examples, operation can be interrupted when the difference is negative (e.g., the expansion device 40 is more “closed” than estimated based on the command position PCMD). Thus, the comparison can include various qualitative or quantitative comparisons for controlling the heat pump 16.

[0059] The output signal can be processed within the control circuitry 12 or outside of the control circuitry 12 to control various components of the water heater system 10. For example, the compressor 36 and the fan 44 can be deactivated based on the output signal. In another example, the water heater system 10 is controlled to an electric heating mode using the resistance heating element(s) 18a, 18b based on the output signal. It is further contemplated that the control circuitry 12 can communicate an indication to the user interface 64 and / or the display 66 to present to a user details regarding the aberrant condition. In some examples, the control circuitry 12 can determine a “lock-up” condition of the expansion device 40. For example, an aberrant condition of the expansion device 40 detected by the control circuitry 12 can include the expansion device being stuck closed, stuck open, or moving out of sync with control. The condition can be presented to the user indicating that heat pump operation is unavailable.

[0060] Referring now to FIG. 4, a pressure-enthalpy (PE) map for a target refrigerant demonstrates an exemplary saturated condensing temperature estimation process performed by the control circuitry 12 using pre-defined relationships (e.g., performance data) with power and / or temperature. The first-third sensors 20-24 are provided to allow detection of an inlet temperature of the evaporator 42, an outlet temperature of the evaporator 42, and an outlet temperature of the compressor 36, respectively. For example, the SST can be determined based on at least one of the evaporator inlet temperature TEin and the evaporator outlet temperature TEout. In one example, the evaporator inlet temperature TEin is used to determine the SST. The evaporator inlet temperature TEin and SST are on the same first isotherm I1. The SST can have a similar corresponding pressure to an evaporator outlet temperature TEout (e.g., located approximately on the same isobar). In some examples, a function of SST and evaporator outlet temperature TEout can be pre-defined or pre-programmed (e.g., via a look-up table, a function, or another data structure). The evaporator outlet temperature TEout can be determined by the control circuitry 12 based on a signal from sensor 22. The SCT can be determined based on the efficiency of the compressor 36 and the ideal isentropic compression of the heat pump 16. For example, the control circuitry 12 can determine a function of constant entropy based on the evaporator outlet temperature TEout lying on the given line of constant entropy.

[0061] With continued reference to FIG. 4, the control circuitry 12 can determine a series of pressure and enthalpy coordinates for the isotherm corresponding to the temperature TCout and determines a series of pressure and enthalpy coordinates for the isotherm corresponding to the isentropic line defined by TEout. The control circuitry 12 can determine an intersection Z at the compressor outlet temperature TCout and the line of constant entropy. The intersection Z represents the pressure and enthalpy values corresponding to an ideal system. The compressor 36 can have an isentropic efficiency of less than 100%, such that intersection Z does not represent actual pressure and enthalpy of the system. The control circuitry 12 can determine datapoints X, Y corresponding to the isentropic efficiency, with datapoint X corresponding to isentropic enthalpy h2sand datapoint Y corresponding to an estimated enthalpy h2r at the outlet of the compressor 36. The isentropic efficiency can be a proportion of 1) the isentropic enthalpy h2sless a first enthalpy h1of the system at the outlet of the evaporator 42; and 2) the estimated enthalpy h2r less the first enthalpy h1of the system. Following determination of point Y, the control circuitry 12 determines SCT using pre-defined relationships between the estimated enthalpy h2r and SCT (e.g., an isobar or another functional relationship). A second isotherm I2 is determined on which the SCT resides. Thus, the control circuitry 12, via the heat-pump control module 26, can estimate SCT without a temperature sensor at the condenser 38 itself. In some examples, the condenser 38 is provided without any sensor communicating an indication of condensing temperature or condensing pressure. In some examples, the only temperature sensors for the heat pump 16 may include the first-fourth sensors 20-26.

[0062] The SCT and the SST can allow the control circuitry 12 to determine mass flow of the compressor 36, and condensing pressure. The control circuitry 12 can process the compressor outlet temperature TCout, the mass flow, and the condensing pressure in one or more functions to determine fluid properties, such as viscosity, density, and velocity, as well as an inlet pressure to the expansion device 40.

[0063] Using the SCT and the SST, the control circuitry 12 estimates various operating conditions of the heat pump 16, such as a flow rate of refrigerant, pressures, a power draw of the compressor 36, etc. By way of example, the heat-pump control module 26 can estimate the power draw based on the SCT and SST and compare the estimated power to the calculated power draw according to electrical detection (e.g., the current and voltage detection circuitry 74, 76). The heat-pump control module 26 can also estimate the pressure at the inlet of the expansion device 40. For example, along the second isotherm I2, the pressure can be constant. However, while demonstrated as having a linear and constant relationship between points X, Y, and SCT, it is contemplated that a pre-defined relationship between points X, Y and SCT can be non-linear. The pressure at the SCT can be different than the pressure at either or both of points X and Y. The relationship between pressures at points X, Y and SCT can be programmed in the control circuitry 12.

[0064] The control circuitry 12 can calculate a change in pressure across the expansion device 40 by comparing the pressure of a first isotherm I1 to the pressure of the refrigerant on the second isotherm I2. Additionally, or alternatively, the control circuitry 12 can compare the temperature of the first isotherm I1to the temperature of the second isotherm I2 to determine a change in temperature across the expansion device 40. Using the calculated change in pressure and / or the change in temperature, the control circuitry 12 can estimate a flow coefficient and therefore a position of the expansion of the expansion device 40. Because the expansion device 40 controls the pressure, or level of pressure reduction, based on a degree of opening before the refrigerant enters the evaporator 42, the pressure change and / or temperature change is indicative of the positionof the expansion device 40. The position of the expansion device 40 can be a size (e.g., diameter, length, width, area) of an orifice defined by the expansion device 40, which can be adjustable or fixed. By way of example, the expansion device 40 can include an electronic expansion valve that controls a size of an opening through which the refrigerant moves. As described with respect to FIG. 3, the diagnostic module 28 can compare the command position PCMD to the position estimate PEST to determine an aberrant condition. The position estimate PEST can be the position estimate PEST as calculated above. In some examples, the position estimate PEST is derived based at least in part on measured electrical power, as will be described with respect to the following figures.

[0065] Referring now to FIG. 5, a method 500 for operating a water heater includes storing a command position PCMD for the expansion device 40 at 502, estimating a position of the expansion device 40 using performance data of the compressor 36 at 504, comparing the estimate to the stored position at 506, and determining a condition of the expansion device 40 based on the comparison at 508. For example, the control circuitry 12 can determine the position estimate PEST as previously described or provide a different position estimate PEST. The command position PCMD can be a command position PCMD previously communicated to the actuator 52. In some examples, the control circuitry 12 can compare the position estimate PEST to an expected size of a fixed-size orifice in examples in which the expansion device 40 is non-adjustable (e.g., non-motorized). By way of example, the command position PCMD can include increments or absolute position command values communicated via a pulse-width modulated (PWM) signal or any other signal that includes a target position. For example, the command position PCMD can be an actual value representative of a position in a range of motion of the actuator 52 or be an increment or decrement from an existing position. In the example in which the command position PCMD is an increment, decrement, or adjustment, the diagnostic module 28 can store a variable representative of an “expected” position of the valve that is adjusted based on the adjustment. Thus, the command position PCMD can be a signal indicative of a + / - number of steps.

[0066] The actuator 52 can be a motor, such as a positioning motor, which adjusts incrementally in response to a command. For example, the motor can be a stepper motor or a servo motor. The temperature and / or electrical power measurements of the water heater system 10 can generally allow the motor to omit a feedback mechanism, such as an encoder or other feedback provided via servo control. By tracking the command position PCMD and comparing it to the position estimate(s) PEST(s), the control circuitry 12 can provide feedback for diagnostic detection.

[0067] In some examples, the method 500 can alternatively compare an expected flow coefficient to an estimated flow coefficient (or coefficient estimate). In such examples, rather than correlating the flow coefficient and the coefficient estimate to position data, the comparison is carried out between the coefficient data. Based on this comparison, the heat pump 16 can be controlled in a similar way to position-based control. By way of example, the coefficient-based comparison method can be utilized for use with systems having non-adjustable expansion devices. When the expansion device 40 is a fixed-size orifice device (e.g., a capillary tube), the method 500 can thus be applied by detecting a difference between the coefficient estimate (estimated based on the measured temperatures and / or electrical parameters as described herein) to a stored flow coefficient that corresponds to the qualities of the fixed-size orifice device. For example, the stored flow coefficient can be pre-programmed based on the qualities of the non-adjustable valve (e.g., a non-motorized valve). Such comparisons can alternatively be applied to variable-size orifice devices, such as an expansion device 40 incorporating an electronic expansion valve. In this way, the algorithms of the present disclosure can be applied to expansion devices 40 having fixed- or variable-size orifices.

[0068] Referring now to FIG. 6, step 504 of method 500 can provide for various position estimate(s) PEST(s). In a first estimation method 600a, the electrical power to the compressor 36 is measured at 602a. For example, the current drawn and the system voltage can be detected by the detection circuitry 74, 76 and received by control circuitry 12. In a second estimation method 600b, the evaporator outlet temperature TEout and the compressor outlet temperature TCout are measured as previously described at 602b. Each estimation method 600a, 600b utilizes the evaporator inlet temperature TEin at 604, calculates the SST at 606, and calculates the condensing pressure and the SCT using performance data of the compressor 36 at 608 / 610. For example, the performance data can include electrical currents mapped to power draw and mass flow rates, thereby being mapped to the SCT. In the second estimation method 600b, the control circuity 12 can estimate the condensing pressure and the SCT using the technique previously described with respect to the isentropic compression (e.g., the example of FIG. 3). At step 610, the condensing pressure is determined.

[0069] Using the condensing pressure, a pressure at the inlet of the expansion device 40 is determined at 612. At 614, the pressure change across the expansion device 40 is estimated based on the inlet pressure. Determining the pressure change across the expansion device 40 can be performed based further on fluid properties into and out of the expansion device 40. For example, the control circuitry 12 can determine mass flow and / or other fluid properties at the inlet of the expansion device 40 based on SCT and SST. Using mass flow, condensing pressure, and the compressor outlet temperature TCout, the control circuitry 12 can estimate starting density, viscosity, and / or other qualities of the refrigerant. The control circuitry 12 can estimate an approximate location in the condenser 38 where condensation begins. With regard to the outlet pressure of the expansion device 40, the control circuitry 12 can utilize the evaporator inlet temperature TEin to determine the outlet pressure of the expansion device 40 (e.g., the pressure along the second isotherm I2). At 616, the flow coefficient through the expansion device 40 is calculated based on a pressure difference across the expansion device 40. The flow coefficient can be determined based further on the qualities of the fluid at an inlet of the expansion device 40 and at an outlet of the expansion device 40 (e.g., viscosity, density, pressure, temperature). For example, the control circuitry 12 can utilize a look-up table or other database to determine the flow coefficient associated with a given pressure change. At step 618, the flow coefficient is correlated with the position estimate PEST. For example, the control circuitry 12 can interact with a data structure, such as a look-up table, to determine the position estimate PEST.

[0070] The second estimation method 600b can also include estimating power as a function of SST and SCT (as calculated using step 602b) at 602c. For example, an expected compressor 36 power to achieve the temperatures read by the sensors 20-24 can be calculated using the efficiency or other performance metrics of the compressor 36. At 604d, the second estimation method 600b can perform various controls of the water heater system 10, such as continuing to steps 506 and 508. In other examples, the power estimate is compared to the measured power (e.g., as calculated at step 602a). If the control circuitry 12 determines a discrepancy between the two power levels, the diagnostic module 28 can determine an aberrant condition. Similar to the position error of the expansion device 40, the discrepancy can be compared to a threshold, as small errors between the estimates can be expected and differentiated from large aberrancies by the control circuitry 12. In some examples, the control circuitry 12 selects between the first estimation method 600a and the second estimation method 600b depending on other factors. In some examples when the discrepancy exceeds the threshold discrepancy tolerance, the diagnostic method is withheld. For example, the control circuitry 12 can selectively execute the diagnostic algorithm based on expected accuracy.

[0071] In some examples, a power estimate using electrical detection (e.g., the current and voltage detection circuitry 74, 76) can be compared to a power estimate that uses temperatures. For example, the method 500 can include determining an estimate of SCT (electrical-based SCT estimate) based on electrical power of the compressor 36, and comparing the compressor outlet temperature TCout, to the electrical-based SCT estimate. If the electrical-based SCT estimate is not less than the compressor outlet temperature TCout by at least a threshold value (e.g., 10°F, 5°F, 2°F), the control circuitry 12 can determine an aberrant condition and / or interrupt operation of the heat pump 16.

[0072] Referring now to FIG. 7, a method 700 of operating a water heater system 10 that includes a heat pump 16 includes compressing a refrigerant via a compressor 36 at 702, exchanging heat from a condenser 38 of the heat pump 16 to a tank 14 of the water heater system 10 at 704, determining a position command PCMD for an expansion device 40 based on at least one operating temperature of the heat pump 16 to control a pressure of the refrigerant at 706, controlling the expansion device 40 based on the position command PCMD at 708, determining a saturated suction temperature (SST) of the refrigerant using a temperature upstream of the compressor 36 at 710, determining a saturated condensing temperature (SCT) of the refrigerant using a temperature downstream of the compressor 36 and upstream of the condenser 38 at 712, determining a position estimate PEST of the expansion device 40 based on the SST and the SCT at 714, comparing the position command PCMD to the position estimate PEST at 716, and determining a condition of the heat pump 16 based on the comparison at 718. By way of example, the components / circuitry described herein can be used to perform the method 700.

[0073] In general, the systems and methods described herein can perform enhanced diagnostics for operating a water heater system 10. For example, enhanced control and fault detection can be provided without a temperature sensor on at least one of the heat exchangers 38, 42. The feedback that may be provided via a robust diagnostic algorithm and heat-pump control algorithm can allow for the omission of feedback devices, such as encoders, for the expansion device 40. The feedback can also provide robust aberrancy detection when in use with non-adjustable expansion devices.

Examples

Embodiment Construction

[0034]As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0035]As used herein, the term “coupled” (in all of its forms: couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and / or any additional intermediate members. Such joining may include members being integrally formed as a single unitary body with one another (i.e., integrally coupled) or may refer to...

Claims

1. A water heater system, comprising:a tank storing water;a heat pump configured to heat the water, the heat pump including a compressor that compresses a refrigerant of the heat pump, a condenser downstream of the compressor, and an expansion device downstream of the condenser that controls a pressure of the refrigerant;a first sensor communicating a first indication of a temperature upstream of the compressor;a second sensor communicating a second indication of a temperature of the refrigerant upstream of the condenser and downstream of the compressor; andcontrol circuitry configured to:determine at least one operating temperature of the heat pump;determine a position command based on the at least one operating temperature;communicate the position command to the expansion device to adjust the expansion device;determine a saturated suction temperature (SST) based on the first indication;determine a saturated condensing temperature (SCT) based on the second indication;determine a position estimate of the expansion device based on the SST and the SCT;compare the position command to the position estimate; anddetermine a condition of the heat pump based on the comparison.

2. The water heater system of claim 1, wherein the determining the position estimate includes determining an inlet pressure to the expansion device based on at least one of the first indication and the second indication.

3. The water heater system of claim 2, wherein the determining the position estimate includes:calculating the inlet pressure to the expansion device using a stored isentropic efficiency of the compressor;determining a pressure change across the expansion device based on the inlet pressure;calculating a flow coefficient of the expansion device based on the pressure difference; andcorrelating the flow coefficient with a position of the expansion device.

4. The water heater system of claim 1, wherein the comparing includes determining a difference between the position command and the position estimate.

5. The water heater system of claim 1, wherein the control circuitry is configured to:receive electrical parameter data;determine a first estimate of power draw to the compressor based on the electrical parameter data;determine a second estimate of electrical power draw to the compressor based on the SST and the SCT; andcompare the first estimate to the second estimate.

6. The water heater system of claim 5, wherein the control circuitry is configured to:control the water heater system based on the comparison of the first and second estimates.

7. A heat pump water heater, comprising:a condenser;a compressor upstream of the condenser that compresses a refrigerant;a first sensor communicating a first indication of a temperature upstream of the compressor;a second sensor communicating a second indication of a temperature of the refrigerant upstream of the condenser and downstream of the compressor;an expansion device downstream of the condenser that controls a pressure of the refrigerant; andcontrol circuitry configured to:store a flow coefficient of the expansion device;determine, based on performance data of the compressor and the first and second indications, a coefficient estimate of the expansion device;compare the flow coefficient to the coefficient estimate; anddetermine a condition of a heat pump based on the comparison.

8. The heat pump water heater of claim 7, wherein the expansion device includes an electronic expansion valve.

9. The heat pump water heater of claim 8, wherein the electronic expansion valve is controlled via a positioning motor.

10. The heat pump water heater of claim 7, wherein the control circuitry is configured to:determine at least one operating temperature of the heat pump; anddetermine the position command based on the at least one operating temperature.

11. The heat pump water heater of claim 10, wherein the control circuitry is configured to communicate the position command to the expansion device to adjust the expansion device.

12. The heat pump water heater of claim 7, wherein the coefficient estimate corresponds to a fixed size of an opening of the expansion device.

13. The heat pump water heater of claim 12, wherein the control circuitry is configured to:determine a saturated condensing temperature (SCT) based on the first indication and the second indication, wherein the SCT is determined without the use of a temperature sensor at the condenser.

14. The heat pump water heater of claim 13, wherein the control circuitry is configured to:calculate an inlet pressure to the expansion device using the SCT and a stored efficiency of the compressor.

15. The heat pump water heater of claim 13, wherein the determining the coefficient estimate includes determining an inlet pressure to the expansion device based on at least one of the first indication and the second indication.

16. The heat pump water heater of claim 15, wherein determining the coefficient estimate includes determining a pressure change across the expansion device based on the inlet pressure.

17. The heat pump water heater of claim 7, wherein the comparing includes determining a difference between the flow coefficient and the coefficient estimate.

18. The heat pump water heater of claim 17, wherein the control circuitry is configured to:compare the difference to a threshold difference, wherein the condition is an aberrant condition determined when the difference exceeds the threshold difference.

19. The heat pump water heater of claim 7, wherein the control circuitry is configured to:receive electrical parameter data;determine a first estimate of power draw to the compressor based on the electrical parameter data;determine a second estimate of electrical power draw to the compressor based on the SST and the SCT;compare the first estimate to the second estimate; andcontrol the heat pump water heater based on the comparison of the first and second estimates.

20. A method of operating a water heater system that includes a heat pump, the method comprising:compressing a refrigerant via a compressor;exchanging heat from a condenser of the heat pump to a tank of the water heater system;determining a position command for an expansion device based on at least one operating temperature of the heat pump to control a pressure of the refrigerant;controlling the expansion device based on the position command;determining a saturated suction temperature (SST) of the refrigerant using a temperature upstream of the compressor;determining a saturated condensing temperature (SCT) of the refrigerant using a temperature downstream of the compressor and upstream of the condenser;determining a position estimate of the expansion device based on the SST and the SCT;comparing the position command to the position estimate; anddetermining a condition of the heat pump based on the comparison.

Images