US20190003760A1

US20190003760A1 - Method for defrosting a heat pump

Info

Publication number: US20190003760A1
Application number: US15/638,466
Authority: US
Inventors: Paul Goodjohn; Robert William Jewell
Original assignee: Haier US Appliance Solutions Inc
Current assignee: Haier US Appliance Solutions Inc
Priority date: 2017-06-30
Filing date: 2017-06-30
Publication date: 2019-01-03

Abstract

A method for defrosting a heat pump includes operating a fan at a particular speed. The fan is positioned to circulate air across the exterior coil of the heat pump. The method also includes measuring a power of the fan while the fan is operating at the particular speed and initiating a defrost of the exterior coil of the heat pump when the power of the fan is less than a threshold power.

Description

FIELD OF THE INVENTION

The present subject matter relates generally to heat pumps, such as heat pumps for packaged terminal air conditioner units, heat pump water heaters, or split heat pump systems.

BACKGROUND OF THE INVENTION

Air conditioner units are conventionally utilized to adjust the temperature within structures such as dwellings and office buildings. In particular, one-unit type room air conditioner units may be utilized to adjust the temperature in, for example, a single room or group of rooms of a structure. Generally, one-unit type air conditioner units include an indoor portion and an outdoor portion. The indoor portion is generally located indoors, and the outdoor portion is generally located outdoors. Accordingly, the air conditioner unit generally extends through a wall, window, etc. of the structure.
One problem frequently encountered with modern air conditioner units and other heat pump systems is accurately determining when to defrost the evaporator. For example, when the evaporator is active, frost can accumulate on the evaporator and thereby reduce efficiency of the evaporator. In particular, ice can build up and accumulate on the evaporator over time, and the ice can eventually block air flow through and around the evaporator. Defrost cycles are frequently started after a predetermined period of air conditioner unit operation. However, the predetermined period of time can be an inaccurate measure of frost buildup. Thus, the defrost cycle can be used too frequently or too infrequently depending upon ambient conditions. For example, in humid locations, more frequent defrosts may be needed while in drier locations less frequent defrosts may be needed.
Accordingly, a method for operating heat pump that assists with determining when ice and/or frost obstructs an evaporator would be useful.

BRIEF DESCRIPTION OF THE INVENTION

The present subject matter provides a method for defrosting a heat pump. The method includes operating a fan at a particular speed. The fan is positioned to circulate air across the exterior coil of the heat pump. The method also includes measuring a power of the fan while the fan is operating at the particular speed and initiating a defrost of the exterior coil of the heat pump when the power of the fan is less than a threshold power. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.
In a first exemplary embodiment, a method for defrosting a heat pump is provided. The method includes operating the heat pump in a heating mode to transfer heat from an exterior coil of the heat pump to an interior coil of the heat pump and operating a fan at a particular speed. The fan is positioned to circulate air across the exterior coil of the heat pump. The method also includes measuring a power of the fan while the fan is operating at the particular speed and initiating a defrost of the exterior coil of the heat pump when the power of the fan is less than a threshold power.
In a second exemplary embodiment, a method for defrosting a heat pump is provided. The method includes operating the heat pump in a heating mode such that the heat pump transfers heat from an exterior coil of the heat pump to an interior coil of the heat pump and delivering a particular voltage input to a fan while operating the heat pump in the heating mode. The fan is positioned to circulate air across the exterior coil of the heat pump. The method also includes measuring a power of the fan while the fan is operates with the particular voltage input and initiating a defrost of the exterior coil of the heat pump when the power of the fan is less than a threshold power.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides an exploded perspective view of a packaged terminal air conditioner unit according to an example embodiment of the present subject matter.

FIG. 2 provides a schematic view of certain components of the example packaged terminal air conditioner unit of FIG. 1.

FIG. 3 provides another schematic view of certain components of the example packaged terminal air conditioner unit of FIG. 1.

FIG. 4 illustrates a method for defrosting a heat pump according to an example embodiment of the present subject matter.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
FIG. 1 provides an exploded perspective view of a packaged terminal air conditioner unit 100 according to an exemplary embodiment of the present subject matter. Packaged terminal air conditioner unit 100 is operable to generate chilled and/or heated air in order to regulate the temperature of an associated room or building. As will be understood by those skilled in the art, packaged terminal air conditioner unit 100 may be utilized in installations where split heat pump systems are inconvenient or impractical. As discussed in greater detail below, a sealed system 120 of packaged terminal air conditioner unit 100 is disposed within a casing 110. Thus, packaged terminal air conditioner unit 100 may be a self-contained or autonomous system for heating and/or cooling air. Packaged terminal air conditioner unit 100 defines a vertical direction V, a lateral direction L and a transverse direction T that are mutually perpendicular and form an orthogonal direction system.
As used herein, the term “packaged terminal air conditioner unit” is used broadly. For example, packaged terminal air conditioner unit 100 may include a supplementary electric heater (not shown) for assisting with heating air within the associated room or building without operating the sealed system 120. However, as discussed in greater detail below, packaged terminal air conditioner unit 100 may also include a heat pump heating mode that utilizes sealed system 120, e.g., in combination with an electric resistance heater, to heat air within the associated room or building. Thus, it should be understood that “packaged terminal air conditioner unit” as used herein is intended to cover both units with heat pump heating modes.
As may be seen in FIG. 1, casing 110 extends between an interior side portion 112 and an exterior side portion 114. Interior side portion 112 of casing 110 and exterior side portion 114 of casing 110 are spaced apart from each other. Thus, interior side portion 112 of casing 110 may be positioned at or contiguous with an interior atmosphere, and exterior side portion 114 of casing 110 may be positioned at or contiguous with an exterior atmosphere. Sealed system 120 includes components for transferring heat between the exterior atmosphere and the interior atmosphere, as discussed in greater detail below.
Casing 110 defines a mechanical compartment 116. Sealed system 120 is disposed or positioned within mechanical compartment 116 of casing 110. A front panel 118 and a rear grill or screen 119 hinder or limit access to mechanical compartment 116 of casing 110. Front panel 118 is positioned at or adjacent interior side portion 112 of casing 110, and rear screen 119 is mounted to casing 110 at exterior side portion 114 of casing 110. Front panel 118 and rear screen 119 each define a plurality of holes that permit air to flow through front panel 118 and rear screen 119, with the holes sized for preventing foreign objects from passing through front panel 118 and rear screen 119 into mechanical compartment 116 of casing 110.
Packaged terminal air conditioner unit 100 also includes a drain pan or bottom tray 138 and an inner wall or bulkhead 140 positioned within mechanical compartment 116 of casing 110. Sealed system 120 is positioned on bottom tray 138. Thus, liquid runoff from sealed system 120 may flow into and collect within bottom tray 138. Bulkhead 140 may be mounted to bottom tray 138 and extend upwardly from bottom tray 138 to a top wall of casing 110. Bulkhead 140 limits or prevents air flow between interior side portion 112 of casing 110 and exterior side portion 114 of casing 110 within mechanical compartment 116 of casing 110. Thus, bulkhead 140 may divide mechanical compartment 116 of casing 110.
Packaged terminal air conditioner unit 100 further includes a controller 146 with user inputs, such as buttons, switches and/or dials. Controller 146 regulates operation of packaged terminal air conditioner unit 100. Thus, controller 146 is in operative communication with various components of packaged terminal air conditioner unit 100, such as components of sealed system 120 and/or a temperature sensor, such as a thermistor or thermocouple, for measuring the temperature of the interior atmosphere. In particular, controller 146 may selectively activate sealed system 120 in order to chill or heat air within sealed system 120, e.g., in response to temperature measurements from the temperature sensor.
Controller 146 includes memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of packaged terminal air conditioner unit 100. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 146 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.
FIG. 2 provides a schematic view of certain components of packaged terminal air conditioner unit 100, including sealed system 120. Sealed system 120 generally operates in a heat pump cycle. Sealed system 120 includes a compressor 122, an interior heat exchanger or coil 124 and an exterior heat exchanger or coil 126. As is generally understood, various conduits may be utilized to flow refrigerant between the components of sealed system 120. Thus, e.g., interior coil 124 and exterior coil 126 may be between and in fluid communication with each other and compressor 122.
As may be seen in FIG. 2, sealed system 120 may also include a reversing valve 132. Reversing valve 132 selectively directs compressed refrigerant from compressor 122 to either interior coil 124 or exterior coil 126. For example, in a cooling mode, reversing valve 132 is arranged or configured to direct compressed refrigerant from compressor 122 to exterior coil 126. Conversely, in a heating mode, reversing valve 132 is arranged or configured to direct compressed refrigerant from compressor 122 to interior coil 124. Thus, reversing valve 132 permits sealed system 120 to adjust between the heating mode and the cooling mode, as will be understood by those skilled in the art.
During operation of sealed system 120 in the cooling mode, refrigerant flows from interior coil 124 flows through compressor 122. For example, refrigerant may exit interior coil 124 as a fluid in the form of a superheated vapor. Upon exiting interior coil 124, the refrigerant may enter compressor 122. Compressor 122 is operable to compress the refrigerant. Accordingly, the pressure and temperature of the refrigerant may be increased in compressor 122 such that the refrigerant becomes a more superheated vapor.
Exterior coil 126 is disposed downstream of compressor 122 in the cooling mode and acts as a condenser. Thus, exterior coil 126 is operable to reject heat into the exterior atmosphere at exterior side portion 114 of casing 110 when sealed system 120 is operating in the cooling mode. For example, the superheated vapor from compressor 122 may enter exterior coil 126 via a first distribution conduit 134 that extends between and fluidly connects reversing valve 132 and exterior coil 126. Within exterior coil 126, the refrigerant from compressor 122 transfers energy to the exterior atmosphere and condenses into a saturated liquid and/or liquid vapor mixture. An exterior air handler or fan 148 is positioned adjacent exterior coil 126 may facilitate or urge a flow of air from the exterior atmosphere across exterior coil 126 in order to facilitate heat transfer.
Sealed system 120 also includes a capillary tube 128 disposed between interior coil 124 and exterior coil 126, e.g., such that capillary tube 128 extends between and fluidly couples interior coil 124 and exterior coil 126. Refrigerant, which may be in the form of high liquid quality/saturated liquid vapor mixture, may exit exterior coil 126 and travel through capillary tube 128 before flowing through interior coil 124. Capillary tube 128 may generally expand the refrigerant, lowering the pressure and temperature thereof. The refrigerant may then be flowed through interior coil 124.
Interior coil 124 is disposed downstream of capillary tube 128 in the cooling mode and acts as an evaporator. Thus, interior coil 124 is operable to heat refrigerant within interior coil 124 with energy from the interior atmosphere at interior side portion 112 of casing 110 when sealed system 120 is operating in the cooling mode. For example, the liquid or liquid vapor mixture refrigerant from capillary tube 128 may enter interior coil 124 via a second distribution conduit 136 that extends between and fluidly connects interior coil 124 and reversing valve 132. Within interior coil 124, the refrigerant from capillary tube 128 receives energy from the interior atmosphere and vaporizes into superheated vapor and/or high quality vapor mixture. An interior air handler or fan 150 is positioned adjacent interior coil 124 may facilitate or urge a flow of air from the interior atmosphere across interior coil 124 in order to facilitate heat transfer.
During operation of sealed system 120 in the heating mode, reversing valve 132 reverses the direction of refrigerant flow through sealed system 120. Thus, in the heating mode, interior coil 124 is disposed downstream of compressor 122 and acts as a condenser, e.g., such that interior coil 124 is operable to reject heat into the interior atmosphere at interior side portion 112 of casing 110. In addition, exterior coil 126 is disposed downstream of capillary tube 128 in the heating mode and acts as an evaporator, e.g., such that exterior coil 126 is operable to heat refrigerant within exterior coil 126 with energy from the exterior atmosphere at exterior side portion 114 of casing 110.
It should be understood that sealed system 120 described above is provided by way of example only. In alternative exemplary embodiments, sealed system 120 may include any suitable components for heating and/or cooling air with a refrigerant. Similarly, sealed system 120 may have any suitable arrangement or configuration of components for heating and/or cooling air with a refrigerant in alternative exemplary embodiments.
FIG. 3 provides another schematic view of certain components of the packaged terminal air conditioner unit 100. As may be seen in FIG. 3, packaged terminal air conditioner unit 100 includes an exterior coil temperature sensor 160 and an exterior coil heating element 170. Exterior coil temperature sensor 160 is positioned at or adjacent exterior coil 126 and is configured for measuring a temperature of exterior coil 126 and/or refrigerant within exterior coil 126. Thus, exterior coil temperature sensor 160 may output a signal, such as a voltage, to controller 146 that is proportional to and/or indicative of the temperature of exterior coil 126. Exterior coil temperature sensor 160 may be any suitable type of temperature sensor, such as a thermistor, a thermocouple, etc.
Exterior coil heating element 170 is positioned at or adjacent exterior coil 126 and is configured for heating exterior coil 126 and/or ice on exterior coil 126, e.g., during defrosting of exterior coil 126. Thus, controller 146 may be configured to selectively activate and deactivate exterior coil heating element 170, e.g., during a defrost cycle to melt ice and frost on exterior coil 126 to improve air flow through exterior coil 126 for heat exchange with ambient air about exterior coil 126. Exterior coil heating element 170 may be any suitable type of heating element, such as an electric resistance heating element.
As may be seen in FIG. 3, exterior air handler 148 includes an inverter 152 and a motor 154. Exterior air handler 148 is in operative communication with controller 146. Thus, controller 146 may selectively activate and deactivate exterior air handler 148. In addition, controller 146 may operate exterior air handler 148 at various speeds by supplying exterior air handler 148 with particular voltages. In such a manner, controller 146 may supply a particular input voltage to exterior air handler 148, and exterior air handler 148 may operate at a particular speed with the particular input voltage. In particular, the inverter 152 may power motor 154 to operate exterior air handler 148 at the particular speed when inverter 152 receives the particular input voltage from controller 146.
As shown in FIG. 3, exterior air handler 148 also includes a sensor 156. Sensor 156 is configured for measuring or outputting a rotational frequency of exterior air handler 148. Sensor 156 may be a Hall effect sensor, an optical sensor, etc. Thus, sensor 156 may output a signal, such as a square-wave signal, to controller 146 that is indicative of the rotational frequency of exterior air handler 148, e.g., an impeller shaft of exterior air handler 148, in hertz. The rotational frequency of exterior air handler 148 is proportional to the angular speed of exterior air handler 148. Thus, the angular speed of exterior air handler 148 may be calculated from the rotational frequency of exterior air handler 148, e.g., by calculating a product of the rotational frequency of exterior air handler 148 and 2π and calculate a quotient of such product and 60.
In alternative embodiments, the angular speed and/or rotational frequency of exterior air handler 148 may be determined without sensor 156. For example, controller 146 may measure the back-emf of motor 154 and determine the angular speed of exterior air handler 148 based upon the back-emf of motor 154. In particular, controller 146 may calculate the quotient of the back-emf of motor 154 and a motor back-emf constant. Thus, exterior air handler 148 need not include sensor 156 in such example embodiments, and controller 146 may determine the angular speed and/or rotational frequency of exterior air handler 148 without sensor 156.
The angular speed and/or rotational frequency of exterior air handler 148 from sensor 156 may be utilized by controller 146 to regulate the speed of exterior air handler 148. For example, as exterior coil 126 frosts over and the resistance to air flow through exterior coil 126 increases, the speed of exterior air handler 148 may increase due to the reduced torque applied by air flow on exterior air handler 148, and sensor 156 may detect such speed increase. To maintain the particular speed, controller 146 may decrease the input voltage to exterior air handler 148.
As noted above, controller 146 may operate exterior air handler 148 at various speeds by supplying exterior air handler 148 with particular input voltages. Controller 146 may also calculate the power of exterior air handler 148, e.g., by calculating the product of the input voltage, the current to exterior air handler 148 and the efficiency of motor 154 (and a power factor for AC applications). Thus, controller 146 may determine the power of exterior air handler 148 during operation of exterior air handler 148.
FIG. 4 illustrates a method 400 for defrosting a heat pump according to an example embodiment of the present subject matter. Method 400 may be used in or with any suitable heat pump 400. For example, method 400 may be used with packaged terminal air conditioner unit 100, e.g., to regulate defrosting of exterior coil 126. Thus, method 400 is described in greater detail below in the context of packaged terminal air conditioner unit 100. However, it will be understood that method 400 may be used in or with heat pump water heater appliances, split heat pump systems, etc., in alternative example embodiments.
At 410, method 400 includes operating sealed system 120 in the heating mode. Thus, sealed system 120 transfers heat from exterior coil 126 to interior coil 124 at 410. When sealed system 120 operates in the heating mode, ice and frost may form on exterior coil 126, e.g., due to condensation and/or deposition of water onto exterior coil 126 from ambient atmosphere about exterior coil 126.
At 420, controller 146 operates exterior air handler 148 at a particular speed. Thus, as discussed above, controller 146 may provide a particular input voltage to exterior air handler 148 at 420. In response to the particular input voltage, exterior air handler 148 may operate at the particular speed. The particular speed may be constant. Thus, exterior air handler 148 may receive feedback from sensor 156 to maintain exterior air handler 148 at the particular speed at 420, e.g., as the restriction to airflow through exterior coil 126 changes due to frost accumulation on exterior coil 126 during operation of sealed system 120 in the heating mode.
At 430, controller 146 calculates the, e.g., output, power of exterior air handler 148 while exterior air handler 148 is operating at the particular speed. The power of exterior air handler 148 changes over time during operation of sealed system 120 in the heating mode due to frost accumulation on exterior coil 126. By tracking the power of exterior air handler 148, method 400 may determine when defrosting of exterior coil 126 is needed. In particular, at 440, controller 146 initiates a defrost of exterior coil 126 when the power of exterior air handler 148 is less than a threshold power. Conversely, controller 146 may continue operating the sealed system in the heating mode when the power of exterior air handler 148 is not less than the threshold power. The defrost of exterior coil 126 may include one or more of activating exterior coil heating element 170 or deactivating sealed system 120 for a period of time, e.g., sufficient for the frost on exterior coil 126 to melt. During the defrost of exterior coil 126, the frost on exterior coil 126 melts such that an efficiency of improves after the defrost.
The threshold power may correspond to the power of exterior air handler 148 when airflow across exterior coil 126 with exterior air handler 148 is blocked by frost or ice on exterior coil 126. In particular, the threshold power may be about ten percent less than the power of exterior air handler 148 when airflow across exterior coil 126 with exterior air handler 148 is not blocked by frost or ice on exterior coil 126. The threshold power may be determined empirically and saved within a table in the memory of controller 146. For example, the threshold power may be a function of the temperature of exterior coil 126, e.g., measured with exterior coil temperature sensor 160. Controller 146 may look up the threshold power in the table after receiving the temperature measurement from exterior coil temperature sensor 160. As another example, the threshold power may correspond to a long term average of the power of exterior air handler 148 measured while sealed system 120 is operating in the heating mode. Thus, e.g., when the current power of exterior air handler 148 deviates from the long term average of the power of exterior air handler 148, such as by ten percent, controller 146 may initiate the defrost of exterior coil 126.
Utilizing method 400, controller 146 may accurately determine when to defrost exterior coil 126. In particular, defrost of exterior coil 126 may be provided only as needed. Method 400 may help account for humidity values of ambient air around exterior coil 126 without requiring a humidity sensor to measure the humidity value. In addition, if the power of exterior air handler 148 does not change after the defrost, method 400 may include alerting a user to clean exterior coil 126. Thus, controller 146 may activate an alert or message a user of packaged terminal air conditioner unit 100 to service exterior coil 126 if the power of exterior air handler 148 does not change after the defrost because airflow through exterior coil 126 may be blocked by material other than ice, e.g., dirt, leaves, etc.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

What is claimed is:

1. A method for defrosting a heat pump, comprising:

operating the heat pump in a heating mode to transfer heat from an exterior coil of the heat pump to an interior coil of the heat pump;

operating a fan at a particular speed, the fan positioned to circulate air across the exterior coil of the heat pump;

measuring a power of the fan while the fan is operating at the particular speed; and

initiating a defrost of the exterior coil of the heat pump when the power of the fan is less than a threshold power.

2. The method of claim 1, wherein the threshold power corresponds to the power of the fan when airflow across the exterior coil of the heat pump with the fan is blocked by frost or ice on the exterior coil.

3. The method of claim 1, wherein the threshold power is about ten percent less than the power of the fan when airflow across the exterior coil of the heat pump with the fan is not blocked by frost or ice on the exterior coil.

4. The method of claim 1, further comprising measuring a temperature of the exterior coil of the heat pump, the threshold power being a function of the temperature of the exterior coil.

5. The method of claim 4, further comprising looking up the threshold power within a table in a controller of the heat pump based upon the temperature of the exterior coil.

6. The method of claim 1, wherein initiating the defrost of the exterior coil of the heat pump comprises one or more of activating a heating element on the exterior coil or deactivating the heat pump for a period of time.

7. The method of claim 1, wherein operating the fan at a particular speed comprises delivering a particular voltage input to the fan, an inverter of the fan driving a motor of the fan to provide a particular torque at the particular voltage input.

8. The method of claim 7, wherein measuring the power of the fan comprises receiving a signal from a sensor of the fan, a frequency of the signal directly proportional to a speed of the fan at the particular voltage input.

9. The method of claim 1, wherein the heat pump does not include a humidity sensor at the exterior coil of the heat pump.

10. The method of claim 1, wherein the heat pump is positioned within a heat pump water heater appliance or a packaged terminal air conditioner.

11. A method for defrosting a heat pump, comprising:

operating the heat pump in a heating mode such that the heat pump transfers heat from an exterior coil of the heat pump to an interior coil of the heat pump;

delivering a particular voltage input to a fan while operating the heat pump in the heating mode, the fan positioned to circulate air across the exterior coil of the heat pump;

measuring a power of the fan while the fan is operates with the particular voltage input; and

12. The method of claim 11, wherein the threshold power corresponds to the power of the fan when airflow across the exterior coil of the heat pump with the fan is blocked by frost or ice on the exterior coil.

13. The method of claim 11, wherein the threshold power is about ten percent less than the power of the fan when airflow across the exterior coil of the heat pump with the fan is not blocked by frost or ice on the exterior coil.

14. The method of claim 11, further comprising measuring a temperature of the exterior coil of the heat pump, the threshold power being a function of the temperature of the exterior coil.

15. The method of claim 14, further comprising looking up the threshold power within a table in a controller of the heat pump based upon the temperature of the exterior coil.

16. The method of claim 11, wherein initiating the defrost of the exterior coil of the heat pump comprises one or more of activating a heating element on the exterior coil or deactivating the heat pump for a period of time.

17. The method of claim 11, wherein an inverter of the fan drives a motor of the fan to provide a particular torque at the particular voltage input.

18. The method of claim 17, wherein measuring the power of the fan comprises receiving a signal from a sensor of the fan, a frequency of the signal directly proportional to a speed of the fan at the particular voltage input.

19. The method of claim 11, wherein the heat pump does not include a humidity sensor at the exterior coil of the heat pump.

20. The method of claim 11, wherein the heat pump is positioned within a heat pump water heater appliance or a packaged terminal air conditioner.