Air to Water Heat Pump System Having Optimized Operation

Various air-to-water heat pump systems have been developed. Known heat pump systems may be utilized to heat water for use in buildings. Such buildings may comprise commercial or residential buildings. Heat pump systems may include hot water storage tanks that store hot water produced by the heat pump for use when the demand for hot water exceeds the capacity of the heat pump. Known air-to-water heat pump systems may utilize a control scheme whereby the heat pump is turned on if a temperature of stored hot water in a tank is at or below a first temperature, and the heat pump may be turned off if the temperature of the stored hot water is at or above a second temperature. Known air-to-water heat pump systems may, alternatively, utilize a preprogrammed schedule whereby the heat pump is turned on and off at specific times.

An aspect of the present invention is a heat pump water system including an air-to-water heat pump unit including a compressor that compresses and heats refrigerant to heat water, and a heat exchanger that is configured to be exposed to ambient air from outside of a building whereby heat from the ambient air is transferred to refrigerant flowing through the heat exchanger. The system includes a hot water tank system that is configured to receive and store hot water from the heat pump unit. The system may include a plurality of temperature sensors that are configured to measure water temperatures in the hot water tank system. The at least six temperature sensors are configured such that a volume of water in the hot water tank system at a temperature above or below a sensed temperature can be determined based, on at least in part, on measured temperatures from the plurality of temperature sensors, whereby a volume of hot water in the hot water tank system above a predefined temperature can be determined. The system is configured to supply hot water from the hot water tank system and/or the heat pump unit to a hot water system of a building having periods of reduced demand for hot water and periods of increased demand for hot water, wherein the periods form demand patterns that are at least somewhat predictable. The system may be configured to produce hot water having a first temperature during periods of reduced demand for hot water, and prior to a predicted period of increased demand for hot water: 1) provide a load up cycle that includes reducing a temperature and/or a volume of hot water produced by the heat pump unit to initially increase a volume of water having a temperature that is less than the first temperature in the hot water tank system, followed by increasing a temperature and/or a volume of hot water produced by the heat pump to increase a volume of hot water in the hot water tank system having a temperature that is greater than the first temperature prior to the period of increased demand for hot water; and/or: 2) adjust a temperature and/or a volume of hot water produced by the heat pump unit and stored in the hot water tank system above a preselected temperature based, at least in part, on present and/or predicted ambient temperatures whereby a volume of hot water in the hot water tank system is adjusted to increase efficiency by increasing production and storage of hot water when the ambient temperature is sufficiently high to increase efficiency of the heat pump relative to the predicted efficiency during a period of increased demand.

The heat pump unit may utilize electrical power during operation, and the system may be configured to adjust a temperature and/or a volume of hot water produced by the heat pump unit and/or stored in the hot water tank system to account for changes in cost of electrical power whereby the heat pump unit provides increased production and storage of hot water during periods in which a cost of electrical power is reduced, and the system provides at least some hot water to a building that was produced utilizing electrical power having lower costs than the cost at the time the hot water is provided to the building.

The system may be configured to utilize predicted hot water demand, outdoor temperature, and the cost of electrical power to minimize an estimated cost of electrical power.

The system may be configured to be operably connected with a communication system to receive information concerning the cost of electrical power supplied to the system.

The hot water tank system may include at least two stratified tanks that are fluidly interconnected such that when the system is increasing a volume of hot water in the hot water tank system, hot water from the heat pump unit flows into a top of a first tank, water from a bottom of a first tank flows into a top of a second tank, and water from a bottom of the second tank is returned to the heat pump unit and heated, whereby the temperature of the water in each of the tanks is higher at a top of the tank, and lower at a bottom of the tank, and the water in the top of the first tank has a higher temperature than water in the top of the second tank.

The system may include a first water temperature sensor located at an upper portion of the first water tank, a second water temperature sensor located at a lower portion of the first water tank, a third water temperature sensor located at an upper portion of the second water tank, a fourth water temperature sensor located at a lower portion of the second water tank, a fifth water temperature sensor located at an upper portion of the third water tank, a sixth water temperature sensor located at a lower portion of the third water tank, and wherein the system is configured to determine a volume of hot water in the hot water tank system based, at least in part, on water temperatures measured by the first, second, third, fourth, fifth, and sixth water temperature sensors.

The system may be configured to cause the heat pump unit to produce water at a first temperature during a baseline mode of operation, and the system may be configured to cause the heat pump unit to produce water at a second temperature that is greater than the first temperature during a second mode of operation.

The system may be configured to utilize the second mode of operation if the cost of utilizing the second mode of operation is less than the cost of utilizing the first mode of operation.

The system may be configured to receive information concerning present and/or future electrical rates, and the system may be configured to utilize the information concerning the present and/or future electrical rates to determine if the cost of utilizing the second mode of operation is less than the cost of utilizing the first mode of operation.

The system may be configured to utilize the second mode of operation if a present ambient temperature is greater than a predicted ambient temperature.

The system may be configured to utilize the second mode of operation to increase a temperature of hot water stored in the hot water tank system to reduce a cost of operation even if an increase in the temperature of hot water stored in the hot water tank system is not necessary to meet a predicted increase in demand for hot water.

The system may be configured to provide a load up cycle based on user-identified demand patterns.

The system may be configured to identify demand patterns and to provide a load up cycle based on the demand patterns identified by the system.

The system may be configured to turn the heat pump unit ON and OFF based, at least in part, on temperatures from a pair of temperature sensors being below and above, respectively, LOW and HIGH temperatures, and the system may be configured to utilize a first pair of temperature sensors during a baseline operating mode whereby the system maintains a baseline volume of stored hot water at a baseline temperature. The system may be configured to initially utilize a second pair of sensors during a load up cycle whereby the volume of stored hot water at the baseline temperature is initially reduced during a load up cycle, and the system may be configured to utilize a third pair of sensors after the volume of stored hot water at the baseline temperature is reduced, whereby a volume of hot water at or above the baseline temperature is increased prior to a predicted period of increased demand.

At least one of the ON and OFF temperatures of the third pair of sensors may be greater than the baseline temperature, whereby at least some stored hot water has a temperature that is greater than the baseline temperature.

The system may be configured to cause the heat pump unit to produce hot water at a baseline output temperature in the baseline operating mode, and cause the heat pump unit to produce hot water at a load up output temperature that is greater than the baseline output temperature when the third pair of sensors is being utilized, whereby the system produces and stores at least some hot water having a temperature that is greater than the baseline temperature prior to a period of increased demand.

Another aspect of the present disclosure is a heat pump water heater system including an air-to-water heat pump unit that heats water utilizing a heat exchanger that is exposed to ambient air. The system includes a hot water tank system that is configured to receive and store hot water produced by the heat pump unit. The system is configured to supply hot water from the hot water tank system and/or the heat pump unit to a hot water system of a building having periods of reduced demand for hot water and periods of increased demand for hot water, wherein the periods of reduced and increased demand form patterns that are at least somewhat predictable. The system may be configured to: 1) utilize present and predicted ambient air temperatures to increase a volume and/or a temperature of water produced by the heat pump unit and/or stored in the hot water tank system when the ambient air temperature provides more efficient production of hot water, and/or 2) utilize present and/or predicted electrical power costs to increase production and storage of hot water when electrical power costs are less than future electrical power costs.

The system may be configured to utilize predicted periods of increased demand for hot water to provide a load up cycle prior to a period of increased demand. The load up cycle may include initially reducing a volume and/or a temperature of hot water produced by the heat pump unit and stored in the hot water tank system prior to a period of increased demand, followed by increasing a volume and/or a temperature of hot water produced by the heat pump unit and stored in the hot water tank system prior to a period of increased demand.

The system may be configured to store a baseline volume of hot water at a baseline water temperature during a baseline operating mode, wherein the baseline operating mode is utilized after a period of increased demand and before a load up cycle. The system may be configured to adjust the baseline volume of hot water based, at least in part, on ambient air temperature, whereby a first volume of hot water is stored in the hot water tank system when the heat exchanger is exposed to ambient air at a first temperature, and a second volume of hot water is stored in the hot water tank system when the heat exchanger is exposed to ambient air at a second temperature, and wherein the first volume of hot water is greater than the second volume of hot water, and the first temperature is less than the second temperature, whereby a baseline volume of hot water stored in the hot water tank system is increased during cold ambient conditions, and reduced during warm ambient conditions to thereby meet predicted demand.

Another aspect of the present disclosure is a method of controlling a heat pump water system having a heat pump unit that includes a heat exchanger that is exposed to ambient air, and a hot water tank system that is configured to receive and store hot water produced by the heat pump unit. The method includes controlling a volume and/or a temperature of hot water produced and/or stored by the system to reduce a cost of supplying hot water to a building having a variable demand for hot water. The control is based, at least in part, on one or more of: 1) predicted demand for hot water; 2) present and/or predicted ambient air temperature; and: 3) the cost of present and/or future electrical power used to operate the heat pump unit.

The heat pump unit may utilize electrical power during operation, and the system may be configured to adjust a volume of hot water in the hot water tank system to account for changes in a cost of electrical power whereby a volume and/or a temperature of stored hot water is increased during periods in which a cost of electrical power is reduced. The system may be configured to provide at least some hot water to a building that was produced utilizing electrical power having a lower cost than the cost at the time the hot water is provided to the building.

The system may be configured to utilize predicted hot water demand, present and/or predicted outdoor temperature, and the present and/or predicted cost of electrical power to minimize an estimated cost of electrical power.

The system may be configured to be operably connected with a communication system to receive information concerning the cost of electrical power supplied to the system and/or present and/or predicted ambient temperatures.

The system may include at least six water temperature sensors whereby temperatures of stratified water in the hot water tank system at six or more locations can be measured. The system may be configured to control the production of hot water based, at least in part, on one or more of the six measured water temperatures.

The hot water tank system may optionally include at least three hot water tanks, which may include diffusers that are fluidly interconnected such that when the system is increasing a volume of hot water in the hot water tank system, hot water from the heat pump unit flows into a top of a first tank, water from a bottom of the first tank flows into a top of a second tank, and water from a bottom of the second tank flows into a top of the third tank, and water from a bottom of the third tank is returned to the heat pump unit and heated, whereby the temperature of the water in each of the three tanks is stratified such that a water temperature is at least minimally higher at a top of each tank and lower at a bottom of each tank, and the water in the top of the first tank has a at least minimally higher temperature than water in the top of the second tank, and water in the top of the second tank has a temperature that is at least minimally higher than water in the top of the third tank. The third tank may optionally include a clocked horizontal diffuser having small water ports that project down to induce cold make-up water to flow downward towards the bottom of the third stratified tank.

The system may include a first water temperature sensor that is configured to measure a temperature of water in an upper portion of the first water tank, a second water temperature sensor that is configured to measure a temperature of water in a lower portion of the first water tank, a third water temperature sensor that is configured to measure a temperature of water in an upper portion of the second water tank, a fourth water temperature sensor that is configured to measure a temperature sensor of water in a lower portion of the second water tank, a fifth water temperature sensor that is configured to measure a temperature of water in an upper portion of the third water tank, and a sixth water temperature sensor that is configured to measure a temperature of water in a lower portion of the third water tank. The system may be configured to determine a volume of hot water in the hot water tank system based, at least in part, on water temperatures measured by the first, second, third, fourth, fifth, and sixth water temperature sensors.

These and other aspects, objects, and features of the present disclosure will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

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

The present application is related to U.S. patent application Ser. No. ______, entitled “MACHINE LEARNING OF HEAT PUMP SYSTEM WATER USAGE PATTERNS FOR OPTIMIZED HEAT PUMP PERFORMANCE,” (Atty. Docket No.: BRA014 P302), filed on even date herewith, the entire contents of which are incorporated herein by reference.

Reference will now be made in detail to the present preferred embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. In the drawings, the depicted structural elements are not to scale and certain components are enlarged relative to the other components for purposes of emphasis and understanding.

As required, detailed embodiments of the present disclosure are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to a detailed design; some schematics may be exaggerated or minimized to show function overview. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the concepts as oriented in. However, it is to be understood that the concepts may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

As used herein, the terms “or” and “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 or device is described as containing, including, or comprising components A, B, or C, the composition or device can contain (include) 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. If a composition or device is described as containing, including, or comprising components A and/or B and/or C, the composition or device can contain (include) 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.

In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “including” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes or comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” or “includes . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

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.

With reference to, a heat pump water heater systemmay include at least one air-to-water heat pump unitthat is configured to supply hot water to a water systemof a building or other such facility that requires hot water. Systemmay optionally include one or more additional heat pump unitsA that may be operably connected with the other components in substantially the same manner as heat pump unit. Unless explicitly stated otherwise, as used herein the term “heat pump unit” includes systems having a single heat pump unitand systems having two or more heat pump units. As discussed in more detail below, the heat pump systemmay also include a hot water tank system(also referred to herein as “tank farm”) that may be utilized to store hot water produced by the heat pump unitand supply hot water to the hot water distribution system(systemmay also be referred to herein as Distributed Hot Water (DHW) system). The components of system(e.g. heat pump unitand/or hot water tank system) may be operably connected to a controller. As discussed below, controllermay comprise a control system including numerous components (e.g. controllers) that are operably interconnected, and the present disclosure is not limited to the single blockof. Also, systemmay include two or more heat pump units, and the present disclosure is not limited to a system having a single heat pump unit.

With further reference to, heat pump unitmay include a compressor, a heat exchanger such as gas cooler/condenser, heat exchanger/evaporator, and an expansion valveto heat cold water flowing into inletA of heat pump unitwhereby hot water is discharged from outletB of heat pump unit. The gas cooler/condensermay comprise a gas cooler or it may comprise a condenser depending on the refrigerant used in heat pump unit. In a preferred embodiment, heat pumputilizes COrefrigerant, and componentcomprises a gas cooler (i.e. heat exchanger for cooling COflowing through heat exchanger). However, other refrigerants may also be utilized and heat exchangermay comprise a condenser. As used herein, the terms “cooler,” “gas cooler,” and “gas cooler/condenser” broadly refer to a heat exchanger that provides for heating of water and cooling of the refrigerant, which may or may not involve condensation of the refrigerant gas. It will be understood that the basic components and operation of heat pump unitmay be similar to known heat pump units utilized to heat water.

As discussed in more detail below, heat pumpconverts electrical energy into thermal energy (hot water) that is stored in hot water tank system. Although the hot water tanks are insulated, some heat is lost from the stored hot water resulting in inefficiency. In general, heat pumpmay need to be operated to generate hot water to replace hot water that has been drawn from tank systemto supply DHW system, and to replace water that has cooled during storage in hot water tank system(standby losses). Although hot water usage may vary, the stored hot water volume may typically be used within a 4 to 6 hour period. Also, the efficiency of heat pumpwill vary depending on ambient (outdoor) temperatures, and heat pumpis typically more efficient at higher ambient temperatures, and less efficient at lower ambient temperatures. Thus, if ambient temperatures vary over time, maximizing efficiency may involve operating heat pumpto generate hot water during warmer (more efficient) ambient conditions prior to a drop in ambient temperature, provided the standby losses do not exceed the efficiency gains resulting from generating hot water during favorable (warmer) ambient temperatures. The total cost of operating the system is a function of the amount and cost of electricity (or other power) at the time the electricity is used. Because the cost of electrical power may vary (e.g. it may increase at certain times of the day), minimizing the cost to operate the systemmay involve increasing production (i.e. a larger portion of the tank system is at high temperature, or increased the stored water temperature to create a larger thermal buffer) of hot water during periods of lower electrical cost whereby the hot water is stored until the hot water is used during a period of increased electrical power cost. However, because some heat is lost from the stored hot water, the amount and timing of hot water production during periods of low energy cost may be adjusted (controlled) so that the heat losses (and resulting increased cost from operating heat pump) due to storing hot water do not exceed the reduction in cost from operating heat pumpduring periods of reduced electrical power cost.

Also, as discussed below, the demand for hot water from systemmay vary over time. Heat pumpmay not be able to generate hot water at a sufficient rate to meet demand during periods of high demand (e.g. periods in which the DHW systemhas a large load/high usage of hot water), and the system is therefore configured to operate heat pumpto generate and store hot water during periods of lower demand whereby the hot water stored in tank systemis used during periods of high demand. As discussed below, the demand for hot water and timing of the high demand periods may be at least somewhat predictable. In general, systemmay be configured to ensure that sufficient hot water is stored in tank systemprior to periods of predicted high demand, while minimizing the cost (e.g. maximizing efficiency) necessary to meet the demand. In operation, the volume of hot water stored in tank systemmay typically be nearly depleted 3 to 5 times a day, an advanced load-up period will recharge the tank systemand reheats the water stored in tank system. As used herein, “hot water” generally refers to water having a temperature that is greater than a predefined temperature (e.g. 140° F., 160° F., 180° F., etc.) whereby the hot water is suitable for use by DHW system. Water supplied to DHW systemis typically at least 120° F.-125° F. Thus, “hot water” stored in tank systemis typically at least 120° F.-125° F. In general, producing and storing water at, for example, 160° F. or 180° F. provides increased thermal capacity relative to producing and storing water at a lower temperature (e.g. 140° F.). However, heat pumpis somewhat less efficient at higher water temperatures, and higher temperatures also result in increased standby losses. “Cold water” may generally refer to water having a temperature that is less than the predefined hot water temperature. For example, if DHW Systemrequired 120° F. water, water in tank systemthat is below 120° F. may be considered cold water.

As discussed below, if the temperature of the stored hot water is above 120° F., then hot water from tank systemis typically mixed with cold water whereby water at 120° F. is supplied to DHW system. Thus, the volume and/or temperature of hot water stored in the tank systemmay be increased to provide an increase in stored thermal energy as required to meet expected increases in demand. The timing and amount of thermal energy stored in tank systemmay also be adjusted to provide increased efficiency and/or reduced cost, even if increased storage of hot water (thermal energy) is not required to meet predicted increases in demand.

Referring again to, an exitof compressoris fluidly connected to a linewhereby, during operation, hot gas (refrigerant) flows through lineto gas cooler/condenserduring operation. Hot gas flows through gas linesand heat is transferred through a thermally conductive structureto water lineswhereby water flowing through water lineis heated. Heat pump unitmay include a water pumpand a valveto control flow of water through water linefrom cold water inletA. After the water is heated by heat exchanger, the water flows through lineto outletB. Heat pump unitmay include a valveto control flow of water through lineto outletB and the speed of pumpmay also be controlled.

During operation, hot refrigerant (e.g. CO) flows from heat exchangerthrough line, through a three-way defrost valve, and into a inletof a recuperator/super heater. As discussed in more detail below, three-way defrost valveand defrost valvemay be utilized to provide a defrost cycle. In use, hot refrigerant from lineflows into inletof recuperator, and cold gas (refrigerant) (e.g. COor other suitable substance) from evaporatorflows into inletof recuperator. The hot gas or liquid from heat exchangerflows through internal lineof recuperator, and cold gas (refrigerant) from evaporatorflows through internal linewhereby heat is transferred from lineto linethrough a thermally conductive structureto partially heat cold gas (refrigerant) from evaporatorbefore the gas (refrigerant) enters inletof compressor. Hot or warm refrigerant exiting outletof recuperatorflows through a lineto one or more inletsof evaporator. A valvemay be utilized to control the flow of refrigerant through line, and expansion valvecauses the pressure and temperature of the refrigerant in lineto drop in a manner that is generally known in the art.

Evaporatormay be positioned inside of a building or in an ambient (outdoor) spaceoutside of a building. One or more fansmay be actuated to promote flow of ambient airover linesof evaporator, resulting in cold gas (refrigerant) flowing through lineafter the gas exits the evaporator. If evaporatoris located inside of a building, airmay be routed from outside the building to evaporatorthrough ducts (not shown) whereby airis typically at an ambient temperature. A liquid separatormay be utilized to separate liquid(e.g. liquid refrigerant or oil) from the gas, and an oil recovery valveand oil linemay be utilized to recover the oil or other liquid. Flow of cold gas through linemay be controlled by a valve, and a valvemay be utilized to control flow of gas between lineand an expansion tank. The cold gas flows through lineto inletof compressor. The gas flowing through linemay be controlled by a valve. In general, if valveis closed, cold gas in lineis routed into recuperatorwhereby the gas is heated before flowing into the inletof compressor. During a defrost cycle defrost valvesandmay be actuated, and valvemay be closed such that hot gas exiting compressorflows through evaporator, bypassing heat exchangerand recuperator. It will be understood that defrost cycles are typically as short as possible to reduce energy loss caused by the defrost cycle. The compressor, pump, fansof evaporator, valves, and other components of heat pump unitmay be operably connected to controller.

In a typical application, the components of heat pumpmay be positioned inside a building, with ducting from the outdoors delivering ambient airto and from the evaporator. Also, it will be understood that the present disclosure is not limited to the specific heat pump shown in. In general, virtually any heat pump including a compressor, gas cooler/condenser, and evaporator may be utilized in a heat pump system() according to the present disclosure.

In general, the speed of compressormay be increased to increase a volume of water (e.g. GPM) produced by heat pumpat a selected temperature and/or to increase a temperature of hot water produced by heat pump. If necessary, the speed of compressormay also be increased to compensate for reduced ambient temperatures.

Referring again to, a hot water outletB of heat pump unitmay be fluidly connected to a water linewhereby hot water flows through a water lineto a junction. The hot water may flow from junctionthrough a water lineto the hot water tank system, and hot water may also flow from junctionthrough hot water lineto a “swing tank” which may comprise a conventional electric (or gas) water heater. Junctionmay comprise a valve that is operably connected to a controllerwhereby the water flow from lineto linesandcan be controlled during operation of the heat pump system. For example, as discussed in more detail below, the controllermay be configured to direct hot water from heat pump unitthrough lineto hot water tank systemif the demand for hot water from the water systemis presently low (but expected to increase), the controllermay be configured to cause hot water to flow from junctionthrough lineto inletof electric water heaterif demand for hot water from the water systemis high. The electric water heatermay be actuated to heat water if the water flowing through water lineis not sufficiently heated, whereby hot water from outletof electric water heaterflows through water lineto a mixing valve. It will be understood that electric water heater(“swing tank”) is optional, and it is not required according to other aspects of the present disclosure.

As discussed above, controllermay comprise a control system including one or more components that are operably interconnected, and it does not necessarily comprise a single control unit. For example, heat pump unitmay include a controllerA, water heatermay include a controllerB, back up heat sourcesand(discussed below) may include controllersC andD, respectively and the system may include a controllerE that controls tank system. Thus, the term “controller” is not limited to a specific configuration, but rather may comprise virtually any suitable arrangement of hardware and/or software that is capable of controlling the heat pump systemin the manner described herein.