Patent Publication Number: US-2023138109-A1

Title: Occupancy based method of operating a heat pump air conditioner unit

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to air conditioner units, and more particularly to methods of operating heat pump air conditioner units. 
     BACKGROUND OF THE INVENTION 
     Air conditioner or conditioning units are conventionally utilized to adjust the temperature indoors, e.g., within structures such as dwellings and office buildings. Such units commonly include a closed refrigeration loop to heat or cool the indoor air. Typically, the indoor air is recirculated while being heated or cooled. A variety of sizes and configurations are available for such air conditioner units. For example, some units may have one portion installed within the indoors that is connected to another portion located outdoors, e.g., by tubing or conduit carrying refrigerant. These types of units are typically used for conditioning the air in larger spaces. 
     Another type of air conditioner unit, commonly referred to as single-package vertical units (SPVU) or package terminal air conditioners (PTAC), may be utilized to adjust the temperature in, for example, a single room or group of rooms of a structure. These units typically operate like split heat pump systems, except that the indoor and outdoor portions are defined by a bulkhead and all system components are housed within a single package that installed in a wall sleeve positioned within an opening of an exterior wall of a building. When a conventional PTAC is operating in a cooling or heating mode, a compressor circulates refrigerant within a sealed system, while indoor and outdoor fans urges flows of air across indoor and outdoor heat exchangers respectively. 
     Certain conventional air conditioner units include a sealed system that is operated as a heat pump for providing a flow of air into the room at a higher temperature than the room temperature. In this regard, a compressor circulates refrigerant through an indoor heat exchanger, an outdoor heat exchanger, and an expansion device such that the refrigerant extracts heat from the outside air and transfers the heat indoors. In general, heat pumps operate in a very efficient operating mode where the temperature difference between the supplied air and the room temperature is relatively small. This may be desirable for improved operating efficiency while also maintaining the target room temperatures. However, the air exhaust stream that is discharged into the room during heat pump operation may be relatively tepid or cool to a room occupant. For example, under certain conditions, as the outside ambient temperatures drop, the temperature of the exhaust stream during heat pump operation may also drop, e.g., resulting in air exhaust stream temperatures below 80° Fahrenheit, which may be perceived as cool to the occupant. 
     Accordingly, improved air conditioner units and methods of operation would be useful. More specifically, a heat pump air conditioner unit that regulates the use of the heat pump system for improved occupant comfort without unduly sacrificing the efficiency of the unit would be particularly beneficial. 
     BRIEF DESCRIPTION OF THE INVENTION 
     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 one exemplary embodiment, an air conditioner unit for heating a room is provided. The air conditioner unit includes a refrigeration loop including an outdoor heat exchanger, an indoor heat exchanger, and an expansion device, a compressor operably coupled to the refrigeration loop and being configured to urge a flow of refrigerant through the refrigeration loop, an indoor fan for urging a flow of indoor air through the indoor heat exchanger, and an outdoor fan for urging a flow of outdoor air through the outdoor heat exchanger. A controller is operably coupled to the compressor and is configured to operate the air conditioner unit in a standard mode of operation to heat the room, determine that an occupant is present in the room, and operate the air conditioner unit in an occupant mode of operation in response to determining that the occupant is present in the room, the occupant mode of operation comprising adjusting at least one operating parameter of the air conditioner unit to increase a discharge temperature of the flow of indoor air. 
     In another exemplary embodiment, a method of operating an air conditioner unit is provided. The air conditioning unit includes a refrigeration loop, a compressor, an indoor fan, and an outdoor fan. The method includes operating the air conditioner unit in a standard mode of operation to heat a room, determining that an occupant is present in the room, and operating the air conditioner unit in an occupant mode of operation in response to determining that the occupant is present in the room, the occupant mode of operation comprising adjusting at least one operating parameter of the air conditioner unit to increase a discharge temperature of a flow of indoor air. 
     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 a perspective view of an air conditioner unit, with part of an indoor portion exploded from a remainder of the air conditioner unit for illustrative purposes, in accordance with one exemplary embodiment of the present disclosure. 
         FIG.  2    is another perspective view of components of the indoor portion of the exemplary air conditioner unit of  FIG.  1   . 
         FIG.  3    is a schematic view of a refrigeration loop in accordance with one embodiment of the present disclosure. 
         FIG.  4    is a rear perspective view of an outdoor portion of the exemplary air conditioner unit of  FIG.  1   , illustrating a vent aperture in a bulkhead in accordance with one embodiment of the present disclosure. 
         FIG.  5    is a front perspective view of the exemplary bulkhead of  FIG.  4    with a vent door illustrated in the open position in accordance with one embodiment of the present disclosure. 
         FIG.  6    is a rear perspective view of the exemplary air conditioner unit and bulkhead of  FIG.  4    including a fan assembly for providing make-up air in accordance with one embodiment of the present disclosure. 
         FIG.  7    is a side cross sectional view of the exemplary air conditioner unit of  FIG.  1   . 
         FIG.  8    illustrates a method for operating an air conditioner unit in accordance with one embodiment of the present disclosure. 
         FIG.  9    is a plot of various operating parameters of an air conditioner unit changing over time as an occupant is sensed and then leaves the room according to an exemplary embodiment of the present subject matter. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     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. 
     Referring now to  FIGS.  1  and  2   , an air conditioner unit  10  is provided. The air conditioner unit  10  is a one-unit type air conditioner, also conventionally referred to as a room air conditioner or a packaged terminal air conditioner (PTAC). The unit  10  includes an indoor portion  12  and an outdoor portion  14 , and generally defines a vertical direction V, a lateral direction L, and a transverse direction T. Each direction V, L, T is perpendicular to each other, such that an orthogonal coordinate system is generally defined. 
     A housing  20  of the unit  10  may contain various other components of the unit  10 . Housing  20  may include, for example, a rear grill  22  and a room front  24  which may be spaced apart along the transverse direction T by a wall sleeve  26 . The rear grill  22  may be part of the outdoor portion  14 , and the room front  24  may be part of the indoor portion  12 . Components of the outdoor portion  14 , such as an outdoor heat exchanger  30 , an outdoor fan  32 , and a compressor  34  may be housed within the wall sleeve  26 . A fan shroud  36  may additionally enclose outdoor fan  32 , as shown. 
     Indoor portion  12  may include, for example, an indoor heat exchanger  40 , a blower fan or indoor fan  42 , and a heating unit  44 . These components may, for example, be housed behind the room front  24 . Additionally, a bulkhead  46  may generally support and/or house various other components or portions thereof of the indoor portion  12 , such as indoor fan  42  and the heating unit  44 . Bulkhead  46  may generally separate and define the indoor portion  12  and outdoor portion  14 . 
     Outdoor and indoor heat exchangers  30 ,  40  may be components of a sealed system or refrigeration loop  48 , which is shown schematically in  FIG.  3   . Refrigeration loop  48  may, for example, further include compressor  34  and an expansion device  50 . As illustrated, compressor  34  and expansion device  50  may be in fluid communication with outdoor heat exchanger  30  and indoor heat exchanger  40  to flow refrigerant therethrough as is generally understood. More particularly, refrigeration loop  48  may include various lines for flowing refrigerant between the various components of refrigeration loop  48 , thus providing the fluid communication there between. Refrigerant may thus flow through such lines from indoor heat exchanger  40  to compressor  34 , from compressor  34  to outdoor heat exchanger  30 , from outdoor heat exchanger  30  to expansion device  50 , and from expansion device  50  to indoor heat exchanger  40 . The refrigerant may generally undergo phase changes associated with a refrigeration cycle as it flows to and through these various components, as is generally understood. Suitable refrigerants for use in refrigeration loop  48  may include pentafluoroethane, difluoromethane, or a mixture such as R 410   a , although it should be understood that the present disclosure is not limited to such examples and rather that any suitable refrigerant may be utilized. 
     As is understood in the art, refrigeration loop  48  may be alternately operated as a refrigeration assembly (and thus perform a refrigeration cycle) or a heat pump (and thus perform a heat pump cycle). As shown in  FIG.  3   , when refrigeration loop  48  is operating in a cooling mode and thus performing a refrigeration cycle, the indoor heat exchanger  40  acts as an evaporator and the outdoor heat exchanger  30  acts as a condenser. Alternatively, when the assembly is operating in a heating mode and thus performs a heat pump cycle, the indoor heat exchanger  40  acts as a condenser and the outdoor heat exchanger  30  acts as an evaporator. The outdoor and indoor heat exchangers  30 ,  40  may each include coils through which a refrigerant may flow for heat exchange purposes, as is generally understood. 
     According to an example embodiment, compressor  34  may be a variable speed compressor. In this regard, compressor  34  may be operated at various speeds depending on the current air conditioning needs of the room and the demand from refrigeration loop  48 . For example, according to an exemplary embodiment, compressor  34  may be configured to operate at any speed between a minimum speed, e.g., 1500 revolutions per minute (RPM), to a maximum rated speed, e.g., 3500 RPM. Notably, use of variable speed compressor  34  enables efficient operation of refrigeration loop  48  (and thus air conditioner unit  10 ), minimizes unnecessary noise when compressor  34  does not need to operate at full speed, and ensures a comfortable environment within the room. 
     Specifically, according to an exemplary embodiment, compressor  34  may be an inverter compressor. In this regard, compressor  34  may include a power inverter, power electronic devices, rectifiers, or other control electronics suitable for converting an alternating current (AC) power input into a direct current (DC) power supply for the compressor. The inverter electronics may regulate the DC power output to any suitable DC voltage that corresponds to a specific operating speed of compressor. In this manner compressor  34  may be regulated to any suitable operating speed, e.g., from 0% to 100% of the full rated power and/or speed of the compressor. This may facilitate precise compressor operation at the desired operating power and speed, thus meeting system needs while maximizing efficiency and minimizing unnecessary system cycling, energy usage, and noise. 
     In exemplary embodiments as illustrated, expansion device  50  may be disposed in the outdoor portion  14  between the indoor heat exchanger  40  and the outdoor heat exchanger  30 . According to the exemplary embodiment, expansion device  50  may be an electronic expansion valve that enables controlled expansion of refrigerant, as is known in the art. More specifically, electronic expansion device  50  may be configured to precisely control the expansion of the refrigerant to maintain, for example, a desired temperature differential of the refrigerant across the indoor heat exchanger  40 . In other words, electronic expansion device  50  throttles the flow of refrigerant based on the reaction of the temperature differential across indoor heat exchanger  40  or the amount of superheat temperature differential, thereby ensuring that the refrigerant is in the gaseous state entering compressor  34 . In this regard, for example, the electronic expansion valve may generally be configured for controlling a differential temperature between an inlet and an outlet of the indoor heat exchanger  40 . According to alternative embodiments, expansion device  50  may be a capillary tube or another suitable expansion device configured for use in a thermodynamic cycle. 
     According to the illustrated exemplary embodiment, outdoor fan  32  is an axial fan and indoor fan  42  is a centrifugal fan. However, it should be appreciated that according to alternative embodiments, outdoor fan  32  and indoor fan  42  may be any suitable fan type. In addition, according to an exemplary embodiment, outdoor fan  32  and indoor fan  42  are variable speed fans, e.g., similar to variable speed compressor  34 . For example, outdoor fan  32  and indoor fan  42  may rotate at different rotational speeds, thereby generating different air flow rates. It may be desirable to operate fans  32 ,  42  at less than their maximum rated speed to ensure safe and proper operation of refrigeration loop  48  at less than its maximum rated speed, e.g., to reduce noise when full speed operation is not needed. In addition, according to alternative embodiments, fans  32 ,  42  may be operated to urge make-up air into the room. 
     According to the illustrated embodiment, indoor fan  42  may operate as an evaporator fan in refrigeration loop  48  to encourage the flow of air through indoor heat exchanger  40 . Accordingly, indoor fan  42  may be positioned downstream of indoor heat exchanger  40  along the flow direction of indoor air and downstream of heating unit  44 . Alternatively, indoor fan  42  may be positioned upstream of indoor heat exchanger  40  along the flow direction of indoor air and may operate to push air through indoor heat exchanger  40 . 
     Heating unit  44  in exemplary embodiments includes one or more heater banks  60 . Each heater bank  60  may be operated as desired to produce heat. In some embodiments as shown, three heater banks  60  may be utilized. Alternatively, however, any suitable number of heater banks  60  may be utilized. Each heater bank  60  may further include at least one heater coil or coil pass  62 , such as in exemplary embodiments two heater coils or coil passes  62 . Alternatively, other suitable heating elements may be utilized. 
     The operation of air conditioner unit  10  including compressor  34  (and thus refrigeration loop  48  generally) indoor fan  42 , outdoor fan  32 , heating unit  44 , expansion device  50 , and other components of refrigeration loop  48  may be controlled by a processing device such as a controller  64 . Controller  64  may be in communication (via for example a suitable wired or wireless connection) to such components of the air conditioner unit  10 . Controller  64  may include a 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 unit  10 . The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. 
     Unit  10  may additionally include a control panel  66  and one or more user inputs  68 , which may be included in control panel  66 . The user inputs  68  may be in communication with the controller  64 . A user of the unit  10  may interact with the user inputs  68  to operate the unit  10 , and user commands may be transmitted between the user inputs  68  and controller  64  to facilitate operation of the unit  10  based on such user commands. A display  70  may additionally be provided in the control panel  66  and may be in communication with the controller  64 . Display  70  may, for example be a touchscreen or other text-readable display screen, or alternatively may simply be a light that can be activated and deactivated as required to provide an indication of, for example, an event or setting for the unit  10 . 
     Referring briefly to  FIG.  4   , a vent aperture  80  may be defined in bulkhead  46  for providing fluid communication between indoor portion  12  and outdoor portion  14 . Vent aperture  80  may be utilized in an installed air conditioner unit  10  to allow outdoor air to flow into the room through the indoor portion  12 . In this regard, in some cases it may be desirable to allow outside air (i.e., “make-up air”) to flow into the room in order, e.g., to meet government regulations, to compensate for negative pressure created within the room, etc. In this manner, according to an exemplary embodiment, make-up air may be provided into the room through vent aperture  80  when desired. 
     As shown in  FIG.  5   , a vent door  82  may be pivotally mounted to the bulkhead  46  proximate to vent aperture  80  to open and close vent aperture  80 . More specifically, as illustrated, vent door  82  is pivotally mounted to the indoor facing surface of indoor portion  12 . Vent door  82  may be configured to pivot between a first, closed position where vent door  82  prevents air from flowing between outdoor portion  14  and indoor portion  12 , and a second, open position where vent door  82  is in an open position (as shown in  FIG.  5   ) and allows make-up air to flow into the room. According to the illustrated embodiment vent door  82  may be pivoted between the open and closed position by an electric motor  84  controlled by controller  64 , or by any other suitable method. 
     In some cases, it may be desirable to treat or condition make-up air flowing through vent aperture  80  prior to blowing it into the room. For example, outdoor air which has a relatively high humidity level may require treating before passing into the room. In addition, if the outdoor air is cool, it may be desirable to heat the air before blowing it into the room. Therefore, according to an exemplary embodiment of the present subject matter, unit  10  may further include an auxiliary sealed system that is positioned over vent aperture  80  for conditioning make-up air. The auxiliary sealed system may be a miniature sealed system that acts similar to refrigeration loop  48 , but conditions only the air flowing through vent aperture  80 . According to alternative embodiments, such as that described herein, make-up air may be urged through vent aperture  80  without the assistance of an auxiliary sealed system. Instead, make-up air is urged through vent aperture  80  may be conditioned at least in part by refrigeration loop  48 , e.g., by passing through indoor heat exchanger  40 . Additionally, the make-up air may be conditioned immediately upon entrance through vent aperture  80  or sequentially after combining with the air stream induced through indoor heat exchanger  40 . 
     Referring now to  FIG.  6   , a fan assembly  100  will be described according to an exemplary embodiment of the present subject matter. According to the illustrated embodiment, fan assembly  100  is generally configured for urging the flow of makeup air through vent aperture  80  and into a conditioned room without the assistance of an auxiliary sealed system. However, it should be appreciated that fan assembly  100  could be used in conjunction with a make-up air module including an auxiliary sealed system for conditioning the flow of make-up air. As illustrated, fan assembly  100  includes an auxiliary fan  102  for urging a flow of make-up air through a fan duct  104  and into indoor portion  12  through vent aperture  80 . 
     According to the illustrated embodiment, auxiliary fan  102  is an axial fan positioned at an inlet of fan duct  104 , e.g., upstream from vent aperture  80 . However, it should be appreciated that any other suitable number, type, and configuration of fan or blower could be used to urge a flow of makeup air according to alternative embodiments. In addition, auxiliary fan  102  may be positioned in any other suitable location within air conditioner unit  10  and auxiliary fan  102  may be positioned at any other suitable location within or in fluid communication with fan duct  104 . The embodiments described herein are only exemplary and are not intended to limit the scope present subject matter. 
     Referring now to  FIG.  7   , operation of unit  10  will be described according to an exemplary embodiment. More specifically, the operation of components within indoor portion  12  will be described during a cooling operation or cooling cycle of unit  10 . To simplify discussion, the operation of auxiliary fan  102  for providing make-up air through vent aperture  80  will be omitted, e.g., as if vent door  82  were closed. Although a cooling cycle will be described, it should be further appreciated that indoor heat exchanger  40  and/or heating unit  44  be used to heat indoor air according to alternative embodiments. Moreover, although operation of unit  10  is described below for the exemplary packaged terminal air conditioner unit, it should be further appreciated that aspects the present subject matter may be used in any other suitable air conditioner unit, such as a heat pump or split unit system. 
     As illustrated, room front  24  of unit  10  generally defines an intake vent  110  and a discharge vent  112  for use in circulating a flow of air (indicated by arrows  114 ) throughout a room. In this regard, indoor fan  42  is generally configured for drawing in air  114  through intake vent  110  and urging the flow of air through indoor heat exchanger  40  before discharging the air  114  out of discharge vent  112 . According to the illustrated embodiment, intake vent  110  is positioned proximate a bottom of unit  10  and discharge vent  112  is positioned proximate a top of unit  10 . However, it should be appreciated that according to alternative embodiments, intake vent  110  and discharge vent  112  may have any other suitable size, shape, position, or configuration. 
     During a cooling cycle, refrigeration loop  48  is generally configured for urging cold refrigerant through indoor heat exchanger  40  in order to lower the temperature of the flow of air  114  before discharging it back into the room. Specifically, during a cooling operation, controller  64  may be provided with a target temperature, e.g., as set by a user for the desired room temperature. In general, components of refrigeration loop  48 , outdoor fan  32 , indoor fan  42 , and other components of unit  10  operate to continuously cool the flow of air. 
     In order to facilitate operation of refrigeration loop  48  and other components of unit  10 , unit  10  may include a variety of sensors for detecting conditions internal and external to the unit  10 . These conditions can be fed to controller  64  which may make decisions regarding operation of unit  10  to rectify undesirable conditions or to otherwise condition the flow of air  114  into the room. For example, as best illustrated in  FIG.  7   , unit  10  may include an indoor temperature sensor  120  which is positioned and configured for measuring the indoor temperature within the room. In addition, unit  10  may include an indoor humidity sensor  122  which is positioned and configured for measuring the indoor humidity within the room. In this manner, unit  10  may be used to regulate the flow of air  114  into the room until the measured indoor temperature reaches the desired target temperature and/or humidity level. 
     As used herein, “temperature sensor” or the equivalent is intended to refer to any suitable type of temperature measuring system or device positioned at any suitable location for measuring the desired temperature. Thus, for example, temperature sensor  120  may each be any suitable type of temperature sensor, such as a thermistor, a thermocouple, a resistance temperature detector, a semiconductor-based integrated circuit temperature sensor, etc. In addition, temperature sensor  120  may be positioned at any suitable location and may output a signal, such as a voltage, to a controller that is proportional to and/or indicative of the temperature being measured. Although exemplary positioning of temperature sensors is described herein, it should be appreciated that unit  10  may include any other suitable number, type, and position of temperature, humidity, and/or other sensors according to alternative embodiments. 
     As used herein, the terms “humidity sensor” or the equivalent may be intended to refer to any suitable type of humidity measuring system or device positioned at any suitable location for measuring the desired humidity. Thus, for example, humidity sensor  122  may refer to any suitable type of humidity sensor, such as capacitive digital sensors, resistive sensors, and thermal conductivity humidity sensors. In addition, humidity sensor  122  may be positioned at any suitable location and may output a signal, such as a voltage, to a controller that is proportional to and/or indicative of the humidity being measured. Although exemplary positioning of humidity sensors is described herein, it should be appreciated that unit  10  may include any other suitable number, type, and position of humidity sensors according to alternative embodiments. 
     Now that the construction of air conditioner unit  10  and the configuration of controller  64  according to exemplary embodiments have been presented, an exemplary method  200  of operating a packaged terminal air conditioner unit will be described. Although the discussion below refers to the exemplary method  200  of operating air conditioner unit  10 , one skilled in the art will appreciate that the exemplary method  200  is applicable to the operation of a variety of other air conditioning appliances. In exemplary embodiments, the various method steps as disclosed herein may be performed by controller  64  or a separate, dedicated controller. 
     Referring now to  FIG.  8   , method  200  includes, at step  210 , operating an air conditioner unit in a standard mode of operation to heat a room. In this regard, for example, the air conditioner unit may be a single-package vertical unit (SPVU), a package terminal air conditioner (PTAC), or any other suitable air conditioner unit. As described briefly above, such air conditioner units commonly discharge heated air into a room to raise the room temperature to a target temperature. In general, the “standard mode of operation” is generally intended to refer to the normal operating mode when an occupant is not present within the room. In this regard, the standard mode of operation may generally be a high-efficiency mode of operation where the heat pump operates to regulate the room temperature toward the target temperature but in a particularly energy-efficient manner. 
     As also explained above, this temperature regulation is commonly achieved by discharging indoor air at a temperature only slightly above the current room temperature, e.g., at discharge temperature below 80° Fahrenheit. However, the flow of indoor air being discharged at these relatively low temperatures may be perceived as cool to the occupant. Accordingly, aspects of the present subject matter are directed to manipulating the operation of an air conditioner unit in response to occupant presence for improved occupant comfort without unduly sacrificing energy efficiency. 
     In general, the standard mode of operation may be triggered by any suitable source, in any suitable manner, and may correspond with any suitable sealed system demand, as described below according to exemplary embodiments. In this regard, for example, a standard mode of operation may be initiated by a thermostat based at least in part on a difference between a measured temperature (e.g., as measured by indoor temperature sensor  120 ) and a temperature setpoint of the air-conditioned room. In this regard, if the measured temperature differs from the temperature set point by more than a predetermined amount, unit  10  may initiate a standard operating cycle to urge the measured temperature toward the temperature setpoint. According to exemplary embodiments, the operating cycle may also be directly initiated by a user of unit  10 , e.g., via manipulation of control panel  66 . Once triggered, the standard mode of operation may include selectively operating compressor  34 , outdoor fan  32 , indoor fan  42 , expansion device  50 , etc. to facilitate heat pump operation and the heating or cooling of indoor air  114 . 
     Step  220  may generally include determining that an occupant is present in the room. In this regard, conditioner unit  10  may include an occupancy sensor  130  for determining room occupancy. In this regard, occupancy sensor  130  may be a motion sensor, an optical sensor, an acoustic sensor, or any other suitable device for detecting motion or activity within the room. In addition, step  220  of determining that an occupant is present in the room may include the use of any other suitable method for determining room occupancy. For example, air conditioner unit  10  may be operably coupled with a door sensor or the room access panel on the door such that occupancy may be determined based on the opening and/or closing of the room door. Other suitable means for detecting room occupancy are possible and within the scope the present subject matter. 
     Step  230  may include operating the air conditioner unit in an occupant mode of operation in response to determining that the occupant is present in the room. In this regard, air conditioner unit  10  may transition from the standard operating mode (e.g., the high-efficiency mode of operation) to the occupant mode of operation (e.g., the relatively lower efficiency and higher temperature mode of operation) upon detecting a room occupant. As explained above, this transition in operating mode may result in the discharge of indoor air at a temperature more suitable and desirable for direct occupant exposure. 
     In general, the “occupant mode of operation” is generally intended to refer to the operation of air conditioner unit while one or more occupants are present within the room being conditioned. In general, the occupant mode of operation may differ from the standard mode of operation in that at least one operating parameter of the air conditioner unit is varied to increase the discharge temperature of the flow of indoor air (e.g., flow of air  114 ). 
     In general, the operating parameter that is adjusted may be any suitable operating parameter of air conditioner unit  10  that is adjustable by controller  64  and that may affect the discharge temperature of indoor air. Exemplary operating parameter adjustments are described below. However, it should be appreciated that according to exemplary embodiments, one or all of these exemplary operating parameters may be adjusted simultaneously to achieve an increase in the discharge temperature of the flow of indoor air relative to that discharged in the standard mode of operation. In addition, it should be appreciated that additional operating parameter adjustments are possible and within the scope of the present subject matter. 
       FIG.  9    illustrates a sequence of operating parameter adjustments that may be performed according to exemplary embodiments. For example, the operating parameter that is adjusted in the occupant mode of operation may be the indoor fan speed of indoor fan  42 . In this regard, air flowing at a higher velocity may generally cause the air to feel cooler to the occupant, e.g., due to the increased rate of heat lost through convection and evaporation. By contrast, lower velocity air may feel warmer. 
     Accordingly, the indoor fan speed may be decreased in the occupant mode of operation relative to the standard mode of operation in order to increase the perceived temperature of the flow of indoor air. By contrast, according to alternative exemplary embodiments, air conditioner unit  10  may have and indoor fan speed that is fixed by a user of the appliance, e.g., via a setting on control panel  66  (e.g., such as a high fan speed, medium fan speed, or low fan speed setting). According to exemplary embodiments, the occupant mode of operation may include this preset indoor fan speed and may manipulate other operating parameters in order to increase the discharge temperature of the flow of indoor air. 
     Referring still to  FIG.  9   , according to an exemplary embodiment, the operating parameter that is adjusted in the occupant mode of operation may be the outdoor fan speed of outdoor fan  32 . In this regard, increasing the outdoor fan speed may generally act to increase the saturated condensing pressure and/or temperature. In turn, this would pull more heat into the refrigerant passing through the outdoor heat exchanger. This additional thermal energy may then be extracted from the indoor heat exchanger, thereby raising the discharge temperature of the flow of indoor air. According to exemplary embodiments, the outdoor fan speed in the occupant mode of operation may be a maximum fan speed or a fan speed at 70%, 80%, 90%, or greater of the rated fan speed. 
     According to an exemplary embodiment, the operating parameter that is adjusted in the occupant mode of operation may be the compressor speed of the variable speed compressor  34 . In this regard, increasing the speed of compressor  34  generally increases the heating capacity of refrigeration loop  48 . Notably, this increase in heating capacity would lead to a faster heating cycle (e.g., the measured room temperature approaches the target room temperature more quickly), and the discharge temperature of the flow of indoor air would feel more comfortable to the room occupant. According to exemplary embodiments, the compressor speed in the occupant mode of operation may be between about 1500 and 4000 revolutions per minute, between about 2000 and 3500 revolutions per minute, between about 2500 and 3000 revolutions per minute, or any other suitable compressor speed that is elevated relative to the standard mode of operation. 
     As also shown in  FIG.  9   , the operating parameter that may be adjusted is a position of the electronic expansion valve  50 . In this regard, when an occupant is sensed, the electronic expansion valve  50  may open slightly from its prior position to permit more refrigerant to flow therethrough. More refrigerant mass flow enables more cooling capacity on the evaporator side and more heating capacity on the condenser side. Operation of the compressor at a higher speed and opening the electronic expansion valve both enable more mass flow and thus greater heating capacity. Thus, manipulating both the compressor and expansion valve in concert to raise the mass flow and heating capacity is desirable, as the heating capacity may drop if only other adjustments are made. The increased heating capacity can be used during occupancy to raise indoor exhaust temperatures. 
     For example, the indoor fan and the outdoor fan may be used to affect the evaporative and condensing temperatures and pressures which can help with meeting the outlet temperature but may not satisfy the room temperature requirements. Moving the compressor to a higher speed and moving the EEV to the increase flow point ensures that there is superheat at the exit of the evaporator and the inlet into the compressor. The indoor and outdoor fan may then be adjusted to balance the two air flows to match the desired outlet temperature for occupancy comfort. 
     According to exemplary embodiments, all of the above-described operating parameter adjustments may happen together to keep air conditioner unit  10  running at a similar heating capacity for both vacancy and occupancy. In this regard, the middle segment of  FIG.  9   , which illustrated the adjustment when an occupant is present, these operating parameter adjustments allow the air conditioner unit  10  to increase the discharge temperature of the flow of indoor air  114  without causing the overall heating capacity to decrease. 
     In general, the operating parameter adjustments described above are intended to increase the discharge temperature of the flow of indoor air. In this regard, for example, the discharge temperature of the flow of indoor air in the standard mode of operation may be between about 70° F. and 90° F., between about 75° F. and 85° F., or less than about 80° F. By contrast, the discharge temperature of the flow of indoor air and the occupant mode of operation may be between about 90° F. and 110° F., between about 95° F. in 105° F., or greater than 100° F. Accordingly, the perceived temperature of the flow of discharge air may be significantly higher in the occupant mode of operation relative to the standard mode of operation. 
     For example, a temperature difference may be defined between the discharge temperature of the flow of indoor air and a target indoor temperature. During operation in a standard mode of operation, the air conditioner unit  10  may discharge the flow of indoor air at a temperature difference of less than 15° F., less than 10° F., less than 5° F., or less. By contrast, during the occupant mode of operation, the temperature difference between the flow of indoor air and the target indoor temperature may be between about 15° F. and 40° F., between about 20° F. and 30° F., or about 25° F. 
     Notably, when an occupant leaves the room or occupancy is no longer detected, it may be desirable to transition back to the more high-efficiency standard mode of operation. Accordingly, step  240  may include determining that the occupant is not present in the room and step  250  may include operating air conditioner unit in the standard mode of operation to heat the room while the occupant is absent. In this manner, overall energy efficiency of air conditioner unit  10  may be maintained while improving consumer satisfaction with the supply of air generated by air conditioner unit  10 . 
     It should be appreciated that according to exemplary embodiments, both the standard mode of operation and the occupant mode of operation may include implementation of closed-loop feedback control algorithms such as a proportional control algorithm, a proportional-integral control algorithm (e.g., a PI controller), or a proportional-integral-derivative control algorithm (e.g., a PID controller). In general, the closed-loop feedback control algorithm may operate refrigeration loop  48  and fans  32 ,  42  to minimize a difference between the measured indoor temperature and a setpoint temperature. In this regard, implementation of the closed-loop feedback control algorithm may include obtaining an indoor temperature (e.g., using indoor temperature sensor  120 ), determining an error value between the indoor temperature and a setpoint temperature, and passing or inputting error value into the closed-loop feedback control algorithm as a control input that minimizes the error. Details regarding the operation of the closed-loop feedback control algorithm are generally well known in the art and further detailed discussion will be omitted here for brevity. It should be appreciated that the algorithm weightings may be adjusted depending on the mode of operation. 
       FIG.  8    depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that the steps of any of the methods discussed herein can be adapted, rearranged, expanded, omitted, or modified in various ways without deviating from the scope of the present disclosure. Moreover, although aspects of method  200  are explained using unit  10  as an example, it should be appreciated that this method may be applied to operate any suitable air conditioner unit. 
     Aspects of the present subject matter are generally directed to improved methods of operating a heat pump air conditioner unit. Specifically, the operation of the heat pump system is generally set such that the exhaust stream of air into the room is typically pushed above 100° Fahrenheit when occupancy is sensed. To achieve this temperature, various operating parameter adjustments may be implemented, such as at least one of decreasing airflow through the indoor fan, increasing the outdoor fan speed, increasing the compressor speed, 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.