MIXTURE CONTROL FOR A WATER HEATER SYSTEM

A water heater system includes a tank storing warmed water, a supply conduit providing supply water, and control circuitry configured to determine a setpoint temperature, receive an input indicative of a sensed temperature of a mixture of the warmed water and the supply water, apply an inverse transfer function to the input to determine a conditioned temperature, assign a control temperature as one of the sensed temperature and the conditioned temperature, compare the setpoint temperature to the control temperature, and generate an output to adjust the mixture based on the selection.

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Description
FIELD OF THE DISCLOSURE

The present disclosure generally relates to a mixture control for water heater systems and, more particularly, to systems and methods for valve control based on filtered temperature feedback.

SUMMARY OF THE DISCLOSURE

According to a first aspect of the present disclosure, a water heater system includes a tank storing warmed water, a supply conduit providing supply water, and control circuitry configured to determine a setpoint temperature, receive an input indicative of a sensed temperature of a mixture of the warmed water and the supply water, apply an inverse transfer function to the input to determine a conditioned temperature, assign a control temperature as one of the sensed temperature and the conditioned temperature, compare the setpoint temperature to the control temperature, and generate an output to adjust the mixture based on the selection.

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

    • the control circuitry is configured to communicate the output to move a mixing device;
    • the comparison includes calculating a difference between the setpoint temperature and the control temperature;
    • the control circuitry is configured to determine a difference between the sensed temperature to the conditioned temperature; and assign the control temperature based on the difference;
    • the control circuitry is configured to select a proportional-integral-derivative (PID) control based on a magnitude of the difference;
    • the control circuitry is configured to adjust a position of at least one valve to cause the control temperature to reach the setpoint temperature, determine a stability period of the control temperature during which the position of the at least one valve is not adjusted, assign the position of the at least one valve during the stability period to a default position, determine an increase of the control temperature following the stability period while the position is not adjusted, and limit adjustment of the position by the default position during the increase;
    • a sensor configured to communicate the input; and
    • a body that houses the sensor and a motor that controls a proportion of the mixture.

According to a second aspect of the present disclosure, a water heater system includes a mixing valve configured to mix cold water with warmed water to achieve a setpoint temperature of a mixture of the cold water and the warmed water, a sensor that communicates a signal indicative of a sensed temperature of the mixture, and control circuitry that receives the signal, conditions the signal, determines a conditioned temperature based on the conditioning, assigns a control temperature as one of the sensed temperature and the conditioned temperature, and controls the mixing valve based on a first difference between the control temperature and the setpoint temperature.

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

    • the control circuitry calculates the control temperature based on a second difference between the sensed temperature and the control temperature and selects the control temperature based on the second difference;
    • the control circuitry selects a PID control among a plurality of PID controls based on the second difference;
    • the control circuitry is configured to adjust a position of the mixing valve to cause the control temperature to reach the setpoint temperature;
    • the control circuitry is configured to determine a stability period of the control temperature during which the position of the mixing valve is not adjusted, and assign the position of the mixing valve to a default position during the stability period;
    • the control circuitry is configured to determine an increase of the control temperature during the stability period temperature following the stability period while the position is not adjusted, and limit adjustment of the position by the default position during the increase;
    • the signal includes processing the signal in a transfer function;
    • the transfer function is an inverse transfer function; and
    • the signal follows a first-order lag relative to a temperature of the mixture.

According to a third aspect of the present disclosure, a method for controlling a mixing valve of a water heater system includes determining a setpoint temperature for a temperature of water exiting the mixing valve, processing a sensed temperature in an inverse transfer function to determine a conditioned temperature, selecting a control temperature as one of the sensed temperature and the conditioned temperature, and controlling the mixing valve based on the control temperature.

Embodiments of the third aspect of the present disclosure can include any one or any combination of the following features:

    • comparing the setpoint temperature to the control temperature, the comparison including calculating a difference between the setpoint temperature and the control temperature; and
    • adjusting a position of the mixing valve to cause the control temperature to reach the setpoint temperature, determining a stability period of the control temperature during which the position of the mixing valve is not adjusted, assigning the position of the mixing valve during the stability period to a default position, determining an increase of the control temperature following the stability period while the position is not adjusted, and limiting adjustment of the position by the default position during the increase.

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

In the drawings:

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

FIG. 2 is a functional block diagram of a mixing control algorithm;

FIG. 3 is a graph of temperature control using a for mixing device;

FIG. 4 is a flow diagram of a first method for controlling a mixing device of a water heater system; and

FIG. 5 is a flow diagram of a second method for controlling a mixing device of a water heater system.

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

DETAILED DESCRIPTION

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.

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.

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.

Referring generally to the figures, 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 therefore be provided for warming water in the tank 14 of the water heater. The water heater system 10 can also control one or more devices, such as a mixing device 20, that mixes supply water SW (cold water) and water warmed in the tank 14 (warmed water WW) to produce a mixture MW of the supply water SW and the warmed water WW. The devices can include one or more valves, such as a mixing valve or individual control valves dedicated to supply water SW control and warmed water WW, respectively. By providing the mixing device 20, the warmed water WW can be maintained at a temperature higher than a target temperature for delivery by the water heater system 10. In general, the water heater system 10 can provide for enhanced response time of the mixing device 20 for the water heater system 10 to provide a mixture temperature TMX at the setpoint temperature TS. The water heater system 10 can also provide for accurate prediction of the mixture temperature TMX by accounting for thermal lag.

Referring to FIGS. 1-5, the water heater system 10 includes a tank 14 storing warmed water WW, a supply conduit 22 providing supply water SW, and control circuitry 12 configured to determine a setpoint temperature TSP, receive an input indicative of a sensed temperature TS of a mixture MW of the warmed water WW and the supply water SW, apply an inverse transfer function to the input to determine a conditioned temperature TC, assign a control temperature TCO as one of the sensed temperature TS and the conditioned temperature TC, compare the setpoint temperature TSP to the control temperature TCO, select a proportional-integral-derivative (PID) control based on the comparison, and generate an output to adjust the mixture MW based on the selection.

In some examples, the mixture MW is controlled via at least one valve. For example, the at least one valve can include one or more valves coupled to one or both of the supply water SW and the warmed water WW. The control circuitry 12 can communicate one or more signals to the at least one valve to adjust a position of the at least one valve. The adjustment can cause a temperature of the mixture MW to be adjusted. The at least one valve can be a mixing device 20 that is local to the water heater (e.g., mounted above the tank 14 or proximate the tank) or may be remote (e.g., for a distributed system of a commercial facility). For example, a plurality of valves can be distributed in a facility controlling the hot water supply to individual regions of the facility. Thus, the at least one valve can include a plurality of valves controlled by the control circuitry 12 according to the algorithm described herein to provide accurate temperature estimation and control of one or more mixtures MW. In some examples, the tank 14 is omitted, such that the present mixture MW control can be performed with a tankless water heater system 10.

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 the 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 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.

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), where 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, 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).

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 heat pump temperature sensors 46 positioned at various points of the heat pump 16 including ambient air. 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). 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, that 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 to the tank 14).

The mixing device 20 is provided for mixing water from the supply conduit 22 from a water utility (“cold water”) and heated or warmed water WW from the tank 14 via an output conduit 58. Accordingly, a target temperature for the tank 14 can exceed the setpoint temperature TSP, such that a temperature of a mixture TMX of the water and warmed water WW reaches the setpoint temperature TSP. 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 62 that measure temperatures adjacent the upper portion 30. 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 WW at the target temperature.

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.

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 control of the at least one valve and/or the mixing device 20 and the water heater system 10. 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.

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 control of one or more valves and/or the water heater system 10. 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.

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 a water heater system 10. For example, the control circuitry 12 can process the input signal from a sensor 74 for monitoring the mixture MW in an ADC and correlate the signal (voltage or current) with a temperature.

With continued reference to FIG. 2, the mixing device 20 can be a mixing valve or another type of mixing device. The mixing device 20 can be operated via a fourth motor 76. For example, the mixing valve can be operated by the fourth motor 76 to adjust the proportions of the mixture MW of warmed water WW vs. supply water SW. By way of example, the fourth motor 76 can be a stepper motor that is responsive to electrical signals by the control circuitry 12 to move, or rotate, thereby adjusting the position of the mixing valve and adjusting the proportions of warmed water WW vs. supply water SW. The mixing device 20 can include a housing made of, for example, brass or another metal. For example, the housing can be considered a valve body of the mixing device 20. The housing can define a mixing chamber in which a piston or other feature moves in response to actuation of the mixing device 20. For example, in response to rotational movement of the fourth motor 76, a piston can translate or otherwise move in the mixing chamber to open or close a portion of the outlet conduit and the supply conduit 22. In this way, the control circuitry 12 can control the mixture temperature TMX.

A sensor 74 (e.g., a mixture temperature sensor) senses a mixture temperature TMX. For example, sensor 74 can include a thermal mass that produces an electrical signal indicative of a sensed temperature TS of the mixture MW. In the example shown in FIG. 2, the sensor 74 is disposed in the housing. The sensor 74 can be in contact with the mixture MW or with a wall or another part of piping to measure the mixture temperature TMX. In some examples, the sensor 74 is positioned downstream of the housing. The thermal mass can include a wax slug via which the variable electrical signal is produced. For example, the sensor 74 can include a thermal actuator that uses wax pellets that expand when heated which can, in-turn, move a piston or other mechanical element, the movement of which can be measured to provide a signal indicative of sensed temperature TS. The sensor 74 can additionally or alternatively include any component that provides a signal representative of the mixture temperature TMX or a change in the mixture temperature TMX.

Due to the physical qualities of the sensor 74, the signal produced (e.g., the sensed temperature TS) can lag an actual mixture temperature TMX. For example, small changes in the sensed temperature TS can be indicative of large change in the mixture temperature TMX due to thermal lag. Accordingly, and as will be described below, the signal can be conditioned to provide a more accurate instantaneous, or “current,” mixture temperature TMX in some modes of operation.

The location of the sensor 74 relative to the tank 14 and/or the mixing device 20 can influence the degree of thermal lag. For example, while a first-order lag may be applicable when the sensor 74 is adjacent the mixing chamber, the thermal lag may be modeled differently depending on the distance from the heated water. Accordingly, the thermal lag can be selected by the control circuitry 12 based on the location of the sensor 74, which can be set or entered by the user and stored in the control circuitry 12.

Referring now to FIG. 2, the control circuitry 12 includes a mixing control module 78 that communicates an output to the mixing device 20 (e.g., the fourth motor 76) to move the mixing device 20 to adjust the proportion of the mixture MW. The “hard” inputs to the mixing control module 78 are signals from the sensor 74 (the sensed temperature TS) and the setpoint temperature TSP. By way of example, the setpoint temperature TSP can be a value stored in the controller 68 that is representative of a setpoint temperature TSP for the mixture MW. Thus, the setpoint temperature TSP can be lower than the tank temperature, or the temperature of the warmed water WW.

In order to control the position of the mixing device 20 to achieve the setpoint temperature TSP, the mixing control module 78 can provide for error correction between a goal temperature (e.g., the setpoint temperature TSP) and an estimate of the mixture temperature TMX. The sensed temperature TS may or may be this temperature due to thermal lag of the sensor 74. For example, prior to calculating any error, the sensed temperature TS is filtered and/or conditioned in a conditioner 80. The conditioner 80 generates a new signal/adjusts the existing signal to provide a conditioned temperature TC. For example, the conditioner 80 can shift the signal in the frequency domain to approximate the mixture temperature TMX. In some examples, the conditioner 80 applies an inverse transfer function to the signal from the sensor 74 to produce the conditioned temperature TC.

At least one of the sensed temperature TS and the conditioned temperature TC can be employed for comparison to the setpoint temperature TSP. In some operational modes, the controller 68 compares the sensed temperature TS to the setpoint temperature TSP, and in other operational modes, the controller 68 compares the conditioned temperature TC to the setpoint temperature TSP. The temperature that is compared to the setpoint temperature TSP is the control temperature TCO. The control temperature TCO can be assigned as one of the sensed temperature TS or the conditioned temperature TC based on the relative values of the sensed temperature TS and the condition temperature in a comparator 81. By controlling the comparison mode of the control module 78, the control circuitry 12 can provide an enhanced response by the mixing device 20 to changes in the setpoint temperature TSP and/or the actual temperature of the mixture MW.

In some examples, the comparator 81 can calculate a difference between the sensed temperature TS and the conditioned temperature TC. Based on the difference, the comparator can assign the control temperature TCO as either the sensed temperature TS or the conditioned temperature TC. For example, the selection can be based on a magnitude of the difference. If the magnitude of the difference is greater than an upper threshold value (e.g., 2° F.), then the comparator 81 can assign the control temperature TCO to the conditioned temperature TC. If the magnitude of the difference is less than a lower threshold (e.g., 0.5° F.), the comparator 81 can assign the control temperature TCO to the sensed temperature TS. In some examples, these values can be dynamically adjusted by the control circuitry 12. In some examples, these thresholds are preprogrammed. The comparator 81 can further utilize the upper and lower thresholds for determining selection of a PID applied to the error between the control temperature TCO and the setpoint temperature TSP, as will be described below.

The control temperature TCO is compared to the setpoint temperature TSP at a differentiator 82. For example, the differentiator 82 can calculate a difference between the setpoint temperature TSP and the control temperature TCO. The difference is the “error” that is applicable to the mixing control module 78. By modifying, or conditioning, the hard input and selecting between a plurality of temperature values prior to determining error, a more accurate representation of the error can be utilized by the module 78.

With continued reference to FIG. 2, the difference of the setpoint temperature TSP and the control temperature TCO is fed into a PID control selector 86. Based on the comparison from the comparator 81, the mixing control module 78 can select a target PID control among a plurality of PID controls. Alternatively, the mixing control module 78, as executed by the control circuitry 12, can adjust the gains of a PID control loop based on the difference.

By way of example, the upper and lower thresholds set in the comparator 81 can further be used for determination of the target PID control. For example, when the difference between the sensed temperature TS and the conditioned temperature TC is greater than the upper threshold, a first PID having relatively high gains can be selected. When the difference is less than the lower threshold for at least a threshold duration (e.g., 60 seconds), the comparator 81 can control the selector 86 to select a second PID having relatively low gains. When the difference is less than the lower threshold for less than the threshold duration, the comparator 81 can control the selector 86 to select a third PID having gains between the gains of the first PID and the second PID. The gains can be one or more values, or constants, applied to one or more of the proportional term, the integral term, and the derivative term of the target PID.

In the present example, three distinct pre-configured PID controls are provided for selection. In other examples, any plurality of PID controls 82 are provided for selection. In general, each PID control can have relatively high proportional and integral coefficients and a relatively low derivative coefficient. The variance in the PID controls can largely control the response time for the mixing control module 78. For example, for a difference larger than a given threshold, the gains for the PID control selected can be higher than the gains for another of the PID controls. For a difference lower than the same threshold, the selected PID control can have lower than gains for the PID control associated with a greater difference. By providing dynamic selection of the PID control employed, the control circuitry 12 can provide a more effective response than operating from a single PID control with common coefficients.

The output of the PID control can result in a command or signal to the mixing device 20. This signal can be a command position or an increment/decrement of the position. In the present example, the output is a target position for the mixing device 20. The output can be a plurality of signals communicated over several conductors or a single conductor. The output can be any type of electrical signal(s) to effectual movement to the position. For example, a pulse-width modulated (PWM) signal can be communicated by the controller 68 to the fourth motor 76 to control the proportion of warmed water WW and supply water SW in the MW.

Referring now to FIG. 3, a graph demonstrating the setpoint temperature TSP, the sensed temperature TS, and the conditioned temperature TC plotted over time (in seconds). As shown, the sensed temperature TS generally follows a first-order lag (e.g., similar to an RLC electrical circuit) relative to the conditioned temperature TC. Based on experimental data, the conditioned temperature TC approximates the actual mixture temperature TMX.

As exemplarily applied for control of the mixing device 20, the control circuitry 12 can select a high-speed first PID control when the sensed temperature TS and the conditioned temperature TC are above the upper threshold. As the conditioned temperature TC changes to be near the sensed temperature TS (the difference lessens), a “mid-speed” PID control can be selected by the control circuitry 12 to control the motor 76 slower than the first PID control. As the difference has a low value for longer than the threshold duration, the control circuitry 12 can select a third PID control having low gains to slowly and stably control the fourth motor 76.

The difference can be a quantity (magnitude) and/or a quality (positive or negative). For example, if the difference is negative, the conditioned temperature TC is greater than the sensed temperature TS, and the difference can be positive in the opposite case. It is contemplated that the selector 86 can select a PID control based on the magnitude alone or based on a combination of the magnitude and the sign of the difference. For example, the comparator 81 can select a lower-speed response PID control whenever the difference is negative. In other examples, a higher-speed response PID control can be selected when the difference is negative.

Referring now to FIG. 4 a method M400 for controlling a at least one valve includes determining a setpoint temperature TSP for a temperature of water exiting the mixing valve at step M402. At step M404, the method M400 includes receiving an input indicative of a sensed temperature TS. For example, the controller 68 may receive a signal from the sensor 74. The method can then include processing a sensed temperature TS in an inverse transfer function to determine a conditioned temperature TC. For example, the method M400 can include applying an inverse transfer function to the sensed temperature TS to determine a conditioned temperature TC at step M406. Step M408 includes assigning a control temperature TCO as one of the sensed temperature TS and the conditioned temperature TC. At step M410, the setpoint temperature is compared to the control temperature TCO. For example, the controller 68 can calculate a difference or otherwise compare these values to produce a comparison output. At step M412, the method includes generating an output to adjust the mixing valve based on the selection.

It is contemplated that the selection of the PID control can be omitted in some examples. For example, the same PID control may be used for all differences in the sensed temperature TS and the conditioned temperature TC or the PID values can be selected using other methods. In general, the method M400 can provide for control of the mixing device 20 based on the conditioned temperature TC.

In some examples, the method includes setting values for a PID control based on a comparison between the sensed temperature TS and the conditioned temperature TC.

Referring now to FIG. 5, another method M500 for operating a mixing valve relates to maintaining a default position of the mixing device 20 when the mixture temperature TMX stabilizes. For example, after a water demand event, the temperature of the mixing device 20 (e.g., the housing and/or mixing chamber) can rise due to proximity of the sensor 74 to the warmed water WW supply (e.g., the tank 14). Because the tank 14 may store water at a higher temperature than the setpoint temperature TSP, the heat from the warmed water WW can influence the sensor 74 to report a high sensed temperature TS. Due to the high temperature, the control circuitry 12 would otherwise be configured to communicate an output to move the mixing valve to increase a proportion of supply water SW relative to the warmed water WW to drop the mixture temperature TMX. Method M500 can address this condition. For example, the control circuitry 12 can limit the position of the mixing valve from causing the mixing valve to move to an overly-cold position (e.g., too much supply water SW relative to warmed water WW).

The method M500 includes adjusting a position of the mixing valve to cause the temperature to reach the setpoint temperature TSP at step M502. For example, the control circuitry 12 can control the fourth motor 76 according to the method of M400. At step M504, a stability period of the control temperature TCO during which the position of the mixing valve is not adjusted is determined. For example, the control circuitry 12 can start a timer after the setpoint temperature TSP equals the control temperature TCO. If such equality is consistent for a duration of the timer, the control circuitry 12 can determine the stability condition/period.

The method M500 further includes assigning the position of the mixing valve during the stability period to a default position at step M506. By way of example, the given position of the fourth motor 76 during the stability period can be indicative of a minimum position for the fourth motor 76 when there is no demand for warmed water WW via the mixture MW, and the control circuitry 12 can assign this position to a lower limit. The default position can thus serve as a “minimum” position to prevent or otherwise limit the mixing valve from moving to a cold position due to the increase in the sensed temperature TS due to no flow and/or proximity of the sensor 74 to the tank 14.

At step M508, an increase in the control temperature TCO following the stability period while the position is not adjusted is determined. For example, the control circuitry 12 can read the conditioned temperature TC or the sensed temperature TS to determine the mixture MW temperature TMX. The method M510 includes limiting adjustment of the position by the default position during the increase. For example, the controller 68 can store the default position in memory 72 and withhold commands to the fourth motor 76 to produce a lower mixture temperature TMX.

It is contemplated that methods 400, 500 can be performed in cooperation with any number of valves not limited to the mixing device 20. For example, as previously described the algorithm can control remote valves or other valves that can result in a different temperature of the mixture MW.

In general, the system 10 and methods M400, M500 described herein can provide for more accurate modeling of the mixture temperature TMX and, therefore, provide for enhanced control of the mixing device 20.

Claims

1. A water heater system, comprising:

a tank storing warmed water;
a supply conduit providing supply water; and
control circuitry configured to: determine a setpoint temperature; receive an input indicative of a sensed temperature of a mixture of the warmed water and the supply water; apply an inverse transfer function to the input to determine a conditioned temperature; assign a control temperature as one of the sensed temperature and the conditioned temperature; compare the setpoint temperature to the control temperature; and generate an output to control the mixture based on the selection.

2. The water heater system of claim 1, wherein the control circuitry is configured to communicate the output to move a mixing device.

3. The water heater system of claim 1, wherein the comparison includes calculating a difference between the setpoint temperature and the control temperature.

4. The water heater system of claim 1, wherein the control circuitry is configured to:

determine a difference between the sensed temperature to the conditioned temperature; and
assign the control temperature based on the difference.

5. The water heater system of claim 4, wherein the control circuitry is configured to:

select a proportional-integral-derivative (PID) control based on a magnitude of the difference.

6. The water heater system of claim 1, wherein the control circuitry is configured to:

adjust a position of at least one valve to cause the control temperature to reach the setpoint temperature;
determine a stability period of the control temperature during which the position of the at least one valve is not adjusted;
assign the position of the at least one valve during the stability period to a default position;
determine an increase of the control temperature following the stability period while the position is not adjusted; and
limit adjustment of the position by the default position during the increase.

7. The water heater system of claim 1, further comprising:

a sensor configured to communicate the input.

8. The water heater system of claim 7, further comprising:

a body that houses the sensor and a motor that controls a proportion of the mixture.

9. A water heater system, comprising:

a mixing valve configured to mix cold water with warmed water to achieve a setpoint temperature of a mixture of the cold water and the warmed water;
a sensor that communicates a signal indicative of a sensed temperature of the mixture; and
control circuitry that receives the signal, conditions the signal, determines a conditioned temperature based on the conditioning, assigns a control temperature as one of the sensed temperature and the conditioned temperature, and controls the mixing valve based on a first difference between the control temperature and the setpoint temperature.

10. The water heater system of claim 9, wherein the control circuitry calculates the control temperature based on a second difference between the sensed temperature and the control temperature and selects the control temperature based on the second difference.

11. The water heater system of claim 10, wherein the control circuitry selects a PID control among a plurality of PID controls based on the second difference.

12. The water heater system of claim 9, wherein the control circuitry is configured to:

adjust a position of the mixing valve to cause the control temperature to reach the setpoint temperature.

13. The water heater system of claim 12, wherein the control circuitry is configured to:

determine a stability period of the control temperature during which the position of the mixing valve is not adjusted; and
assign the position of the mixing valve to a default position during the stability period.

14. The water heater system of claim 13, wherein the control circuitry is configured to:

determine an increase of the control temperature during the stability period following the stability period while the position is not adjusted; and
limit adjustment of the position by the default position during the increase.

15. The water heater system of claim 9, wherein conditioning the signal includes processing the signal in a transfer function.

16. The water heater system of claim 15, wherein the transfer function is an inverse transfer function.

17. The water heater system of claim 9, wherein the signal follows a first-order lag relative to a temperature of the mixture.

18. A method for controlling a mixing valve of a water heater system, comprising:

determining a setpoint temperature for a temperature of water exiting the mixing valve;
processing a sensed temperature in an inverse transfer function to determine a conditioned temperature;
selecting a control temperature as one of the sensed temperature and the conditioned temperature; and
controlling the mixing valve based on the control temperature.

19. The method of claim 18, comprising:

comparing the setpoint temperature to the control temperature, the comparison including calculating a difference between the setpoint temperature and the control temperature.

20. The method of claim 18, further comprising:

adjusting a position of the mixing valve to cause the control temperature to reach the setpoint temperature;
determining a stability period of the control temperature during which the position of the mixing valve is not adjusted;
assigning the position of the mixing valve during the stability period to a default position;
determining an increase of the control temperature following the stability period while the position is not adjusted; and
limiting adjustment of the position by the default position during the increase.
Patent History
Publication number: 20260258975
Type: Application
Filed: Mar 3, 2025
Publication Date: Sep 3, 2026
Applicant: BRADFORD WHITE CORPORATION (AMBLER, PA)
Inventors: John Adams (St. Louis, MO), Benjamin DeJager (Ada, MI)
Application Number: 19/068,532
Classifications
International Classification: F24H 15/175 (20220101); F24H 15/219 (20220101); F24H 15/315 (20220101); F24H 15/414 (20220101);