Patent Publication Number: US-2019170404-A1

Title: Multi-capacity compressor with variable speed drive and method of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is continuation-in-part application of U.S. patent application Ser. No. 15/334,101, filed Oct. 25, 2016, entitled “MULTI-STAGE COMPRESSOR WITH VARIABLE SPEED DRIVE AND METHOD OF USE”, the entire contents and disclosure of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     The field of the disclosure relates generally to multi-capacity compressors, and more specifically to a multi-capacity compressor with a variable speed drive. 
     Known multi-capacity compressors provide two or more levels of compression, e.g., a two-capacity compressor provides a high and low compression level. Many known heating ventilation and cooling (HVAC) systems, such as, for example, an air conditioner or a heat pump, utilize multi-capacity compressors to provide two levels of cooling capacity. One level, i.e., the high-capacity setting, provides cooling for hot, high-demand days. Another level, i.e., the low-capacity setting, provides cooling, for example, for milder days or other low-cooling demand periods of time. A typical installation utilizes the low-capacity setting 80% of the time, resulting in improved efficiency in operating the HVAC system. In such systems, the two-capacity compressor operates for longer periods of time, produces less noise, and produces more even temperatures. Accordingly, multi-capacity HVAC systems provide greater comfort and operate with greater efficiency. 
     A typical two-capacity HVAC system operates at 100% capacity on the high-capacity setting and at about 66% capacity on the low-capacity setting. Such systems demonstrate an improved, i.e., higher, seasonal energy efficiency ratio (SEER) when operating at lower capacity. Efficiency improvements are gained in part by more efficient operation of the compressor, and also through operation of the indoor and outdoor fans at lower speeds. Typically, the system is more efficient at lower compressor capacity. Efficiency improvements are typically limited in this regard, in that the two-capacity compressor cannot operate at a low enough capacity to match the cooling load or achieve the efficiencies of fully variable speed systems. 
     BRIEF DESCRIPTION 
     In one aspect, a heating ventilation and air conditioning (HVAC) system is provided. The HVAC system includes a multi-capacity compressor configured to operate selectively at a high-capacity setting, a medium-capacity setting, and a low-capacity setting to provide a compressor output. The HVAC system also includes a variable-voltage variable-frequency drive coupled to the multi-capacity compressor and configured to operate the multi-capacity compressor at a variable speed, and a processor coupled to the multi-capacity compressor and the variable-voltage variable-frequency drive. The processor is configured to select one of the high-capacity setting, the medium-capacity setting, or the low capacity setting at which the multi-capacity compressor should operate based on a load determined for the multi-capacity compressor. The processor is also configured to employ the variable-voltage variable-frequency drive to operate the multi-capacity compressor at the variable speed to match the compressor output to the load, and bypass the variable-voltage variable-frequency drive when operating the multi-capacity compressor at the high-capacity setting for a compressor heating output based on a heating load. 
     In another aspect, a control system for a multi-capacity compressor is provided. The control system includes an alternating current (AC) line voltage source configured to operate the multi-capacity compressor, a variable-voltage variable-frequency drive coupled to the AC line voltage source and configured to operate the multi-capacity compressor at a variable speed, and a processor coupled to the AC line voltage source and the variable-voltage variable-frequency drive. The processor is configured to selectively couple the AC line voltage source and the variable-voltage variable-frequency drive to the multi-capacity compressor to operate the multi-capacity compressor. The processor is also configured to transmit a capacity control signal to the multi-capacity compressor, the control signal instructive to operate the multi-capacity compressor in one of a high-capacity setting, a medium-capacity setting, or a low-capacity setting, while the multi-capacity compressor is being powered by the selectively coupled one of the AC line voltage source or the variable-voltage variable-frequency drive. 
     In yet another aspect, a control system for a multi-capacity compressor configured to operate in at least two capacity settings is provided. The control system includes an alternating current (AC) line voltage source configured to operate the multi-capacity compressor, a variable-voltage variable-frequency drive coupled to the AC line voltage source and configured to operate the multi-capacity compressor at a variable speed, and a processor coupled to the AC line voltage source and the variable-voltage variable-frequency drive. The processor is configured to selectively couple the AC line voltage source and the variable-voltage variable-frequency drive to the multi-capacity compressor to operate the multi-capacity compressor. The processor is also configured to transmit a capacity control signal to the multi-capacity compressor, the control signal configured to select one of the at least two capacity settings at which the multi-capacity compressor is to operate while the multi-capacity compressor is being powered by the selectively coupled one of the AC line voltage source or the variable-voltage variable-frequency drive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary HVAC system; 
         FIG. 2  is a schematic diagram of one embodiment of a control system for use in the HVAC system shown in  FIG. 1 ; 
         FIG. 3  is a flow diagram of an exemplary method of operating a multi-capacity compressor, such as the multi-capacity compressor shown in  FIG. 1 ; and 
         FIG. 4  is a flow diagram of another exemplary method of operating a multi-capacity compressor, such as the multi-capacity compressor shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “example implementation” or “one implementation” of the present disclosure are not intended to be interpreted as excluding the existence of additional implementations that also incorporate the recited features. 
     Single-capacity and multi-capacity, such as, for example, and without limitation, two-capacity HVAC systems generally cannot vary the speed of the compressor. Although two-capacity compressors can operate at a lower capacity, e.g., 66%, the lower capacity is typically not as low as is achieved in variable speed compressors. Consequently, such systems cannot match the cooling load during mild conditions, resulting in shortened operating periods, frequent cycling, and greater temperature variations. Variable speed HVAC systems are typically more complex due to the necessary electronics to match the drive speed to the cooling load, but do provide more efficient and more comfortable cooling over a wider range of cooling loads. Cooling loads, in certain embodiments, may be measured or estimated. 
     Embodiments of the present disclosure, it is realized herein, provide a combination of a multi-stage compressor (referred to herein as a “multi-capacity” compressor) and a variable speed drive that provide an even greater range of efficient operation and further improve SEER, in some cases, for example, in excess of 5 SEER. More specifically, embodiments of the HVAC systems described herein may utilize a multi-capacity compressor in combination with a variable-voltage variable-frequency drive. It is further realized herein that such an HVAC system may be operated in various configurations, including at high-capacity with the variable-voltage variable-frequency drive, at low-capacity with the variable-voltage variable-frequency drive, at high-capacity with alternating current (AC) line voltage, and at low-capacity with AC line voltage. More specifically, as realized herein, in certain embodiments, operation of the multi-capacity compressor at high-capacity with AC line voltage provides a high-capacity setting, operation at low-capacity with AC line voltage provides a medium-capacity setting, and operation at low-capacity with the variable-voltage variable-frequency drive provides a range of low-capacity settings varying in speed. It is further realized herein that, by foregoing operation at high-capacity with the variable-voltage variable-frequency drive, a lower-rated variable-voltage variable-frequency drive may be utilized. It is further realized herein that bypassing the variable-voltage variable-frequency drive for the high-capacity setting and the medium-capacity setting further improves efficiency by eliminating operating losses of the variable-voltage variable-frequency drive. 
     In some embodiments, the HVAC system may be operated in various other configurations, including at a medium-capacity with the variable-voltage variable-frequency drive and at medium-capacity with AC line voltage, wherein the medium-capacity represents a capacity level between the high-capacity and low-capacity. It is further realized that one or more capacity levels of the compressor may be associated with a heating operation of the HVAC system. In one particular embodiment, the high-capacity levels is associated with a heating operation of the HVAC system—that is, when the compressor operates under the high-capacity setting, the HVAC system is operating as a heat pump to heat an interior space. 
     As used herein, a “capacity” of the multi-capacity compressor refers to a cooling (or heating) capacity, and is variable (e.g., between high-capacity, medium-capacity, and low-capacity) by varying an internal volume of the multi-capacity compressor. For example, an actuator may be operated to vary the volume from a full internal volume, at which the multi-capacity compressor is operated at high-capacity, to a reduced internal volume, at which the multi-capacity compressor is operated at low-capacity or medium-capacity. Additional actuators and/or variably operable actuators may provide additional variability of the internal volume to provide additional capacity levels at which the multi-capacity compressor may operate. Where “cooling capacity” and/or “cooling load” are referred to herein, it should be understood that such descriptions may be equally applicable to the “heating capacity” and/or “heating load” of the HVAC system. 
       FIG. 1  is a block diagram of an exemplary HVAC system  100 . HVAC system  100  includes a compressor  102  that compresses a refrigerant  104  to produce a pressure within HVAC system  100  and a resulting flow of refrigerant  104 . Compressor  102  is a two-capacity compressor having two distinct levels of capacity at which compressor  102  may operate. In alternative embodiments, compressor  102  may have 3 or more levels of capacity. The levels of capacity are referred to as a high-capacity setting and a low-capacity setting, which further refer to the cooling capacity available at the respective levels of capacity. Generally, compressor  102  consumes more energy, i.e., electrical power, and is less efficient when operating at the high-capacity setting versus the low-capacity setting. A typical installation of HVAC system  100  operates compressor  102  at the low-capacity setting about 80% of its operating time. 
     As described above, in other embodiments, compressor  102  is a three-capacity compressor having three distinct levels of capacity at which compressor  102  may operate. The levels of capacity are referred to as a high-capacity setting, a medium-capacity setting, and a low-capacity setting, which further refer to the cooling or heating capacity available at the respective levels of capacity (e.g., based on the internal volume of compressor  102  at the respective levels of capacity). 
     HVAC system  100  includes an outdoor heat exchanger  106 , an indoor heat exchanger  108 , and an expansion valve  110 . Compressor  102  generates the flow of refrigerant  104  through each of outdoor heat exchanger  106 , indoor heat exchanger  108 , and expansion valve  110  to cool an interior space  112 . Heat from interior space  112  is carried by refrigerant  104  and transferred to an exterior space  114 . Interior space  112  and exterior space  114  combine to define a cooling load for HVAC system  100  as a function of a temperature set point for interior space  112  and an ambient temperature of exterior space  114 . When operating as a heat pump, HVAC system  100  operates in reverse, carrying heat from exterior space  114  into interior space  112 . Accordingly, where reference is made herein to cooling interior space  112 , it should be understood that HVAC system  100  is also configured to heat interior space  112 , and such descriptions should be considered non-limiting. 
     During operation, as cool low-pressure refrigerant  104  moves through indoor heat exchanger  108 , a blower  116  generates an interior airflow  118  through indoor heat exchanger  108 . Interior airflow  118  carries warm air from interior space  112  through indoor heat exchanger  108 , thereby cooling interior airflow  118  and heating refrigerant  104 . Low-pressure refrigerant  104  flows from indoor heat exchanger  108  into compressor  102  and is compressed, raising the temperature and pressure of refrigerant  104  before it flows into outdoor heat exchanger  106 . HVAC system  100  includes a fan  120  that generates an exterior airflow  122  through outdoor heat exchanger  106 . As hot high-pressure refrigerant  104  moves through outdoor heat exchanger  106 , exterior airflow  122  carriers ambient air from exterior space  114  through outdoor heat exchanger  106 , thereby cooling refrigerant  104  and heating exterior airflow  122 . High-pressure refrigerant  104  flows from outdoor heat exchanger  106  into expansion valve  110 , where refrigerant  104  is decompressed and cooled before flowing back into indoor heat exchanger  108 . 
     HVAC system  100  also includes a variable speed drive  124  coupled to blower  116  and configured to turn blower  116  at a variable speed. The speed at which blower  116  turns determines the volume of air in interior airflow  118  that moves through indoor heat exchanger  108 . Moreover, the efficiency with which energy is transferred from the warm interior airflow  118  to the cool low-pressure refrigerant  104  flowing through indoor heat exchanger  108  is a function of the volume of air and the speed at which blower  116  turns. Further, the speed of blower  116  that is necessary to achieve efficient energy transfer may be reduced as the cooling load decreases. The speed of blower  116  may be further decreases when compressor  102  is operated at low-capacity. 
     HVAC system  100  includes a variable speed drive  126  coupled to fan  120  and configured to turn fan  120  at a variable speed. The speed at which fan  120  turns determines the volume of air in exterior airflow  122  that moves through outdoor heat exchanger  108 . Moreover, the efficiency with which energy is transferred from the warm high-pressure refrigerant  104  flowing through outdoor heat exchanger  106  to exterior airflow  122  is a function of the volume of air and the speed at which fan  120  turns. Further, the speed of fan  120  that is necessary to achieve efficient energy transfer may be reduced as the cooling load decreases. The speed of fan  120  may be further decreased when compressor  102  is operated at low-capacity. 
     HVAC system  100  includes a variable-voltage variable-frequency drive  128  coupled to compressor  102 . Variable-voltage variable-frequency drive  128  provides power to compressor  102  and regulates an output voltage and frequency to control the speed at which compressor  102  operates, thereby affecting the overall cooling capacity of compressor  102 . At lower speeds, compressor  102  operates at a lower cooling capacity. At higher speeds, compressor  102  operates at a higher cooling capacity. Compressor  102  may be combined with variable-voltage variable-frequency drive  128  in various manners, including operating at a variable speed at the high-capacity setting, and operating at a variable speed at the low-capacity setting. Further, compressor  102  may be operated at AC line voltage to achieve respective maximum cooling capacities at the high-capacity setting and the low-capacity setting. More specifically, when operating compressor  102  at AC line voltage, variable-voltage variable-frequency drive  128  is bypassed, thereby eliminating the operating losses introduced by variable-voltage variable-frequency drive  128 . 
     Compressor  102  may also be operated at a variable speed at a medium-capacity setting with either variable-voltage variable-frequency drive  128  or AC line voltage, thereby increasing the range of operation of HVAC system  100 . 
       FIG. 2  is a block diagram of an exemplary control system  200  for use with HVAC system  100  shown in  FIG. 1  and, more specifically, compressor  102 . Control system  200  includes an AC line voltage source  202  and variable-voltage variable-frequency drive  128  that are alternatively coupled to compressor  102  through a switching network  204  to operate compressor  102 . For example, AC line voltage source  202  is coupled to compressor  102  through a run capacitor  214  and directly by closing corresponding switches within switching network  204  and decoupling variable-voltage variable-frequency drive  128 . Similarly, AC line voltage source  202  is decoupled from compressor  102  by opening corresponding switches within switching network  204 , coupling variable-voltage variable-frequency drive  128  to compressor  102 , and bypassing run capacitor  214 . In alternative embodiments, AC line voltage source  202  and variable-voltage variable-frequency drive  128  may be alternatively coupled and decoupled from compressor  102  using any suitable switching device or network of switching devices, including, for example, and without limitation, electromechanical relays, field effect transistor (FET) devices, insulated-gate bipolar transistors (IGBTs), and other power electronics. AC line voltage source  202  provides an AC line voltage signal, such as, for example 60 Hertz 240 Volt. In alternative embodiments, AC line voltage source  202  may provide other frequencies and voltages according to the grid requirements for that particular implementation. For example, certain countries utilize 50 Hertz as a line frequency. Similarly, certain countries utilize 230 Volt as a line voltage. AC line voltage source  202  may include a terminal block or bus configured to provide line voltage. In certain embodiments, AC line voltage source  202  may include a main system relay configured to switch AC line voltage to compressor  102 , HVAC system  100 , or both, for example. 
     Control system  200  includes a processor  208 . Processor  208  is coupled to switching network  204 . Processor  208  controls switching network  204  to alternatively couple AC line voltage source  202  and variable-voltage variable-frequency drive  128  to compressor  102 . Processor  208  is further coupled to variable-voltage variable-frequency drive  128  to control the speed at which compressor  102  is operated when operated by variable-voltage variable-frequency drive  128 . Processor  208  transmits a speed control signal  210  to variable-voltage variable-frequency drive  128  to affect the speed at which compressor  102  is operated. Speed control signal  210  received by variable-voltage variable-frequency drive  128  is instructive to operate compressor  102  at a variable speed. Processor  208  is further coupled to compressor  102 . Processor  208  transmits a capacity control signal  212  to compressor  102 . Capacity control signal  212 , when received by compressor  102 , is instructive to operate compressor  102  at either a high-capacity setting or a low-capacity setting. In certain embodiments, processor  208  is integrated with variable-voltage variable-frequency drive  128 . 
     In some embodiments, processor  208  transmits capacity control signal  212  to instruct compressor  102  to operate in one of the high-capacity setting, a medium-capacity setting, and the low-capacity setting. That is, compressor  102  operates in only one of the capacity settings at any one time. Accordingly, in various embodiments, processor  208  transmits capacity controls signal  212  over one or more analog signal lines, or over a digital signal line. 
     In certain embodiments, processor  208  is configured to couple AC line voltage source  202  to compressor  102  and bypass variable-voltage variable-frequency drive  128 , thereby eliminating the operating losses introduced by variable-voltage variable-frequency drive  128 . 
       FIG. 3  is a flow diagram of an exemplary method  300  of operating compressor  102 , shown in  FIGS. 1 and 2 . Method  300  begins at a start step  310 . Processor  208  determines a cooling load for compressor  102  at a determination step  320 . The cooling load is determined as a function of a temperature set point for interior space  112  and an ambient temperature for exterior space  114 . 
     At a capacity selection step  330 , processor  208  selects a cooling capacity setting based on the determined cooling load. The cooling capacity setting is selected from among the high-capacity setting and the low-capacity setting for compressor  102 . Generally, processor  208  selects the high-capacity setting when the cooling load is large, and selects the low-capacity setting when the cooling load is smaller. 
     Processor  208  transmits a capacity control signal  212  to compressor  102  at a capacity control step  340 . Capacity control signal  212  is instructive to operate compressor  102  at the selected cooling capacity setting, i.e., the high-capacity setting or the low-capacity setting. 
     At a power source selection step  350 , processor  208  selects a power source to operate compressor  102  based on the determined cooling load. The power source is selected by processor  208  from among AC line voltage source  202  and variable-voltage variable-frequency drive  128 . Given the capacity selection at capacity selection step  330  and the determined cooling load, processor  208  selects either AC line voltage source  202  or variable-voltage variable-frequency drive  128  to match the cooling output of compressor  102  during operation  360  of compressor  102  with the determined cooling load. For example, when the cooling load is at its maximum, processor  208  selects  330  the high-capacity setting for compressor  102  and operates  360  compressor  102  with AC line voltage source  202  as the power source to produce the maximum cooling output. Likewise, when the cooling load is minimal, processor  208  selects  330  the low-capacity setting and operates  360  compressor  102  using variable-voltage variable-frequency drive  128  to achieve a low speed and low cooling output, thereby improving the efficiency of compressor  102 . Further, when the cooling load is at an intermediate level, in certain embodiments, processor  208  selects  330  the low-capacity setting and further selects  350  AC line voltage source  202  to operate  360  compressor  102  at the maximum cooling capacity for the low-capacity setting. Moreover, in such embodiments, variable-voltage variable-frequency drive  128  is bypassed to eliminate the operating losses introduced by variable-voltage variable-frequency drive  128  when operated at a variable speed. 
     In certain embodiments, compressor  102  is only operable with variable-voltage variable-frequency drive  128  when compressor  102  is operated at the low-capacity setting. Consequently, when processor  208  selects  330  the high-capacity setting, processor  208  further selects  350  AC line voltage source  202  to operate  360  compressor  102 . Method  300  terminates at an end step  370 . 
       FIG. 4  is a flow diagram of an exemplary method  400  of operating compressor  102 , shown in  FIGS. 1 and 2 . Method  400  begins at a start step  410 . Processor  208  determines one of a cooling load or a heating load (generally, a load) for compressor  102  at a determination step  420 . The cooling load or heating load for compressor  102  is determined as a function of a temperature set point for interior space  112  and an ambient temperature for exterior space  114 . 
     At a capacity selection step  430 , processor  208  selects a capacity setting based on the determined cooling or heating load. The capacity setting may be a cooling capacity setting or a heating capacity setting. The capacity setting is selected from among the high-capacity setting, the medium-capacity setting, and the low-capacity setting for compressor  102  such that a compressor output (e.g., a heating or cooling output from compressor  102 ) is matched to the determined load. Generally, processor  208  selects the high-capacity setting when the cooling load is large, and selects the medium-capacity or low-capacity setting when the cooling load is smaller. For example, processor  208  selects the high-capacity setting when the cooling load is above a first threshold, selects the medium-capacity setting when the cooling load is below the first threshold and above a second (lower) threshold, and selects the low capacity setting when the cooling load is below the second threshold. In some embodiments, when processor  208  determined a heating load for compressor  102 , of any magnitude, processor  208  selects the high-capacity setting. That is, in such embodiments, the high-capacity setting is reserved for heating operations of HVAC system  100 . 
     Processor  208  transmits a capacity control signal  212  to compressor  102  at a capacity control step  440 . Capacity control signal  212  is instructive to operate compressor  102  at the selected capacity setting, i.e., the high-capacity setting, the medium-capacity setting, or the low-capacity setting. 
     At a power source selection step  450 , processor  208  selects a power source to operate compressor  102  based on the determined cooling or heating load. The power source is selected by processor  208  from among AC line voltage source  202  and variable-voltage variable-frequency drive  128 . Given the capacity selection at capacity selection step  430  and the determined cooling or heating load, processor  208  selects either AC line voltage source  202  or variable-voltage variable-frequency drive  128  to match a necessary output of compressor  102  during operation  360  of compressor  102  with the determined cooling or heating load. For example, when a cooling load is at its maximum, processor  208  selects  430  the high-capacity setting for compressor  102  and operates  460  compressor  102  with AC line voltage source  202  as the power source to produce the maximum cooling output. Likewise, when the cooling load is minimal, processor  208  selects  430  the low-capacity setting and operates  460  compressor  102  using variable-voltage variable-frequency drive  128  to achieve a low speed and low cooling output, thereby improving the efficiency of compressor  102 . Further, when the cooling load is at an intermediate level, in certain embodiments, processor  208  selects  430  the medium-capacity setting or the low-capacity setting and further selects  450  AC line voltage source  202  to operate  460  compressor  102 . Moreover, in such embodiments, variable-voltage variable-frequency drive  128  is bypassed to eliminate the operating losses introduced by variable-voltage variable-frequency drive  128  when operated at a variable speed. Method  400  terminates at an end step  470 . 
     HVAC systems described herein provide a combination of a multi-capacity compressor and a variable speed drive that provide an even greater range of efficient operation and further improve SEER, in some cases, for example, in excess of 5 SEER. More specifically, embodiments of the HVAC systems described herein may utilize a multi-capacity compressor in combination with a variable-voltage variable-frequency drive. It is further realized herein that such an HVAC system may be operated in various configurations, including at high-capacity with the variable-voltage variable frequency drive, at low-capacity with the variable-voltage variable-frequency drive, at high-capacity with alternating current (AC) line voltage, and at low-capacity with AC line voltage. More specifically, as realized herein, in certain embodiments, operation of the multi-capacity compressor at high-capacity with AC line voltage provides a high-capacity setting, operation at low-capacity with AC line voltage provides a medium-capacity setting, and operation at low-capacity with the variable-voltage variable-frequency drive provides a range of low-capacity settings varying in speed. It is further realized herein that, by foregoing operation at high-capacity with the variable-voltage variable-frequency drive, a lower-rated variable-voltage variable-frequency drive may be utilized. It is further realized herein that bypassing the variable-voltage variable-frequency drive for the high-capacity setting and the medium-capacity setting further improves efficiency by eliminating forward operating losses of the variable-voltage variable-frequency drive. 
     It is further realized that such an HVAC system may be operated at medium-capacity with the variable-voltage variable frequency drive, and at medium-capacity with the AC line voltage. In certain embodiments, operation of the multi-capacity compressor at high-capacity is reserved for heating outputs based on heating loads, whereas operation of the multi-capacity compressor under lower-capacity settings (e.g., low-capacity or medium-capacity) is reserved for cooling outputs matched to measured cooling loads. 
     The methods and systems described herein may be implemented using computer programming or engineering techniques including computer software, firmware, hardware or any combination or subset thereof, wherein the technical effect may include at least one of: (a) combining a multi-capacity compressor with a variable speed drive, e.g., a variable-voltage variable-frequency drive; (b) reducing losses by bypassing the variable-voltage variable-frequency drive when operating at a line voltage, particularly at intermediate operating speeds; (c) operating the multi-capacity compressor at a low-capacity and at a variable speed; (d) operating a two-capacity compressor at less than 40% of full cooling capacity; (e) improving operating efficiency, e.g., SEER, of the multi-capacity compressor and the HVAC system; (f) reducing the necessary fan speeds for heat transfer from heat exchangers during low cooling loads; (g) improving efficiency of the HVAC system further by lowering fan speeds to operate in a more efficient range of speeds; (h) operating the multi-capacity compressor at a low-capacity for longer cycles; (i) improving efficiency and comfort due to more continuous low-capacity cooling; (j) improving compressor lubrication through use at higher rotational speed and lower capacity; (k) reducing cost and complexity over variable speed compressors; (l) operating the multi-capacity compressor at three or more capacity levels, including a high-capacity, medium-capacity, and low-capacity; and (m) operating the multi-capacity compressor at a high-capacity setting under a heating load. 
     Some embodiments involve the use of one or more electronic or computing devices. Such devices typically include a processor, processing device, or controller, such as a general purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a reduced instruction set computer (RISC) processor, an application specific integrated circuit (ASIC), a programmable logic circuit (PLC), a field programmable gate array (FPGA), a digital signal processing (DSP) device, and/or any other circuit or processing device capable of executing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a computer readable medium, including, without limitation, a storage device and/or a memory device. Such instructions, when executed by a processing device, cause the processing device to perform at least a portion of the methods described herein. The above examples are exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the terms processor, processing device, and controller. 
     In the embodiments described herein, memory may include, but is not limited to, a computer-readable medium, such as a random access memory (RAM), and a computer-readable non-volatile medium, such as flash memory. Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, additional input channels may be, but are not limited to, computer peripherals associated with an operator interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used that may include, for example, but not be limited to, a scanner. Furthermore, in the exemplary embodiment, additional output channels may include, but not be limited to, an operator interface monitor. 
     As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by a processor, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are examples only, and are thus not limiting as to the types of memory usable for storage of a computer program. 
     The systems and methods described herein are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. 
     This written description uses examples to provide details on the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure 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 have 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 language of the claims.