Patent Publication Number: US-2021164683-A1

Title: System and Method for Compressor Optimization and System Cycling

Description:
TECHNICAL FIELD 
     The present disclosure is directed to HVAC operations and in particular to compressor optimization and system cycling. 
     BACKGROUND OF THE INVENTION 
     HVAC systems sometimes take advantage of tools called economizers. Economizers function by supplying outside air to a space when doing so will save energy. For example, if there is a demand for cool air to a space, and the outside air is sufficiently cool, then the economizer will open a gate or air damper to direct outside air to a building/room/etc. Economizers save money and energy by using ambient air instead of depending on the outputs of an HVAC circuit. 
     BRIEF SUMMARY OF THE INVENTION 
     A possible embodiment under the present disclosure can comprise a method for operating an HVAC system comprising a heat exchanging coil, one or more compressors, and an HVAC controller, the method comprising: receiving, at the HVAC controller, a temperature request for a climate controlled space; determining a basis air temperature of the climate controlled space using a sensor in the climate controlled space; determining an ambient air temperature; determining that ambient air can be used to fulfill the temperature request without compressor operation; restricting operation of a compressor; supplying ambient air to the climate controlled space; determining a supply air temperature using a sensor in the supply airstream; determining a current temperature of the climate controlled space; and adjusting an operation of the HVAC system based on at least the determined supply air temperature, the determined current temperature of the climate controlled space, and the determined ambient temperature. 
     Another possible embodiment comprises a method of operating an HVAC system comprising a heat exchanging coil, one or more compressors, and an HVAC controller, the method comprising: determining a temperature of a climate controlled space; receiving a request to lower the determined temperature to a chosen temperature; determining an ambient temperature; determining that the determined ambient temperature is less than the determined temperature of the climate controlled space; restricting operation of a compressor within the HVAC system; allowing an ambient air to comprise a portion of the supply air of the HVAC system; determining a change in a temperature of the supply air, the climate controlled space, or the ambient temperature; and adjusting an operation of the HVAC system based on at least the determined change in the temperature of the supply air, the climate controlled space, or the ambient temperature. 
     Another possible embodiment under the present disclosure can comprise an HVAC system for providing conditioned air to a space, comprising: a cabinet comprising; an inlet for an ambient airstream; a supply airstream; a return airstream; and at least one heat exchanger; an ambient temperature sensor; a supply air temperature sensor; a space temperature sensor; a thermostat coupled to the cabinet, ambient temperature sensor, supply air temperature sensor, and the space temperature sensor and configured to receive a temperature request, wherein when the request is to heat the space when the determined ambient temperature is greater than the determined temperature of the space or to cool the space when the determined ambient temperature is less than the determined temperature of the space, the thermostat is configured to; restrict operation of a compressor within the HVAC system; allow an ambient air to comprise a supply air of the HVAC system; determine a change in a temperature of the supply air; determine a change in the temperature of the space; determine a change in the ambient temperature; and adjust an operation of the HVAC system based on at least the determined change in the temperature of the supply air, the determined change in the temperature of the space, and the determined change in the ambient temperature. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram of a possible system embodiment under the present disclosure. 
         FIG. 2  is a flow-chart diagram of a possible method embodiment under the present disclosure. 
         FIG. 3  is a flow-chart diagram of a possible method embodiment under the present disclosure. 
         FIG. 4  is a flow-chart diagram of a possible method embodiment under the present disclosure. 
         FIG. 5  is a flow-chart diagram of a possible method embodiment under the present disclosure. 
         FIG. 6  is a flow-chart diagram of a possible method embodiment under the present disclosure. 
         FIG. 7  is a flow-chart diagram of a possible method embodiment under the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     There are a couple of products on the market that are designed to interrupt the compressor signal from a thermostat to help optimize the energy of an HVAC system. These include economizers which are found in many commercial HVAC systems that are designed to fully break the compressor control signals and open an air damper to allow the intake of fresh air when the outside conditions are within acceptable range. The other products on the market have been designed for residential applications where they are inline with the compressor signal calls to disengage the compressor based on the supply air (or discharge air) temperature reaching a pre-defined point and then allowing the compressor to re-engage once the supply air has increased to another pre-defined temperature. The supply air monitoring point is typically mounted directly on the cooling coils of the HVAC equipment. This solution has no knowledge of the interior temperatures or no control over the individual stages of the HVAC system. 
     Another type of prior art is a process known as a supply air temperature reset which is found in larger building automation systems that have chillers as their primary cooling source. This solution adjusts the supply air temperature by controlling the cooling loop of either the chilled water or the compressors of a chiller. This process is programmed from a central controller in a BMS/BAS/EMS system that communicates directly with the chiller. In the prior art, one disadvantage is that thermostats and controllers are separate and there is no intelligence between them. Therefore, the interior temperatures have the potential not to be maintained as the prior art does not have the ability to disengage its process. Additionally, prior art systems for compressor cycling are designed for residential applications that only have a single stage cooling process. When these products are used in commercial applications they connect all stages of cooling together which forces the HVAC to have a higher cycle rate. This process also has the potential for increasing humidity. The conventional approach only works with cooling systems whereas the current disclosure has solutions which work with both cooling and heating processes. 
     One embodiment of a solution under the present disclosure is a solution utilizing thermostats and controllers that optimize the energy of an HVAC system using the supply air temperature, interior temperature and individual control of each HVAC stage. The system can use pre-defined set points and can also use built-in intelligence to determine the optimal minimal supply air temperature that the HVAC system can produce. While prior art systems required that air sensors be placed in the HVAC cabinet on a coil, solutions under the present disclosure can comprise air sensors mounted in various locations in and about the HVAC system. Sensors can be wired or wireless, or combinations of the two. The present disclosure can be implemented with conventional cooling systems as well as heat pumps for both cooling and heating cycles. Another advantage under the present disclosure is that some embodiments can have the intelligence to learn the optimal supply air temperature. A system under the present disclosure can therefore act as a free air cooling system simulating an economizer when the unit has a permanent fresh air intake. Embodiments can therefore act to modulate the supply air temperature to maintain proper interior temperatures, reduce compressor runtime, reduce system energy use, and reduce system peak demand while ensuring that the compressors are not short cycling. Solutions under the present disclosure can be enhanced by applying similar algorithms to additional cooling and heating stages in an HVAC system. 
     An embodiment of an HVAC system can be seen in  FIG. 1 . System  100  comprises a return airstream  120 , supply airstream  185 , and outside airstream  110 . Inlet  112  for outside air  110  comprises a gate that can be open and closed. Blower  105  directs outside air through the system  100 . Enthalpy wheel  180  (or other type of heat exchanger) spans both the outside air  110  and return air  120 /exhaust air  127 . Enthalpy wheel  180  may be optional or turned off in some embodiments. Return air  120  enters system  100  and can then split into exhaust airstream  127  and recycle airstream  126 . Gate  124  can open and close. When open, all or part of airstream  120  will be directed back into the system  100  (recycle airstream  126 ). When closed, all of return air  120  will become exhaust air  127 . Blower  105  assists in the movement of return air  120  and exhaust air  127 . Outlet  128  comprises a gate that can open and close. Outside air  110  (and in some situations recycle air  126 ) forms primary airstream  130  which passes through cooling coil  170 . Blower  105  helps in directing primary airstream  130  into supply airstream  185 . 
     System  100  can comprise controlling circuitry  150 . Controller  150  comprises a connection (wired or wireless) to a thermostat  152 , likely located elsewhere within a building. Thermostat  152  can comprise more or less control over HVAC system  100  than the controller  150 . Intelligence and processing power can also be distributed among thermostat  152 , controller  150 , or even other components of system  100 . Portions of the system can also be cloud based, wherein storage, processing, or other functions take place remotely, in the cloud. Thermostat  152  can comprise a temperature sensor (or a connection to a temperature sensor or sensor array, or other types of sensors) within a conditioned or heated space. Controller  150  also connects to compressor  160 . Compressor  160  can comprise connections to HVAC components such as coil  170 , heat exchangers, expansion devices, refrigerant lines, and more (most of these components are not shown in  FIG. 1  for the sake of clarity). Controller  150  can comprise connections to temperature, humidity, or other sensors  154 ,  156 ,  157 ,  158 ,  159 ,  199  and other components within the system  100  and the broader HVAC footprint at a given location. Connections between the various components described can be wired or wireless (such as cellular, Bluetooth, or WiFi). Furthermore, some components can be remote from the others. Thermostat  152 , sensors  154 ,  156 ,  157 ,  158 ,  159 ,  199  or other components, can be remote. Components described can also comprise arrays of the named component. For example, sensors  154 ,  156 ,  157 ,  158  can each comprise sensor arrays. Ambient sensor  154  can be web-based, or remote, or provided by a third party, in some embodiments. Remote sensor  199  can comprise a remote sensor located far from the physical footprint of system  100 . Remote system  199  can comprise a wired or wireless connection to thermostat  152 . 
     HVAC system  100  can comprise one or more sensors  154 ,  156 ,  157 ,  158 ,  159  and  199 , any of which can comprise connections to controller  150  or thermostat  152 . Temperature sensor  154  can detect ambient temperature. Sensor  156  can detect temperature within the HVAC system. Sensor  157  can detect return air temperature. Sensor  158  can detect temperature within the coil  170 . Sensor  159  can detect temperature within the supply airstream  185 . Prior art systems typically only comprised a single temperature sensor, usually an ambient temperature sensor or a sensor within the cooling coil. Embodiments under the present disclosure can comprise multiple temperature sensors—any or all of sensors  154 ,  156 ,  157 ,  158 ,  159 ,  199  or any combination thereof. A preferred embodiment comprises a temperature sensor  159  for the supply air  185 , an ambient sensor  154 , and/or room sensors  152 / 199 . 
     During certain cooling or heating situations, an HVAC system can be designed to supply outside air to the conditioned space instead of heating or cooling air during the HVAC cycle. Typically, these scenarios arise when there is a demand to cool a space, and the outside air is cooler than the space&#39;s current temperature. Another example is when there is a demand for heating and the outside air is hotter than the space. 
     A typical economizer in the prior art will only look at ambient temperature. One possible disadvantage of prior art systems can be increased humidity. Another prior art scenario involves only the use of the coil temperature. A typical downside of this process is that the compressor tends to cycle on and off frequently. Such cycling can result in pressure drops and spikes and can degrade equipment quickly. These prior art processes typically comprise a direct connection between the temperature sensor and the control of the outside air supply, such that there is a temperature switch. The system is automatic and does not take into account other factors, such as additional temperature readings from elsewhere in the system. 
     Embodiments under the present disclosure can use multiple temperature readings including ambient air (sensor  154 ), temperature within an HVAC cabinet or rooftop unit (sensor  156 ), coil (sensor  158 ), return air (sensor  157 ), supply air (sensor  159 ), and/or remote sensor  199 . Any combination of the foregoing, as well as other temperatures, can be used. Preferred embodiments will use at least the supply air temperature and at least one other temperature reading. Solutions under the present disclosure can store temperature readings for sensors  154 ,  156 ,  157 ,  158 ,  158 ,  199  (or readings from other sensors), along with records of compressor cycling, temperatures inside the conditioned space (such as at thermostat  152 ). In this manner the system can learn how the different input values yield various results. Most embodiments will comprise a temperature sensor  159  for the supply air. Because the system knows the supply air it can better understand how outside air temperature, coil temperature, or other factors contribute to the resulting supply air. Temperature measurements within the space tend to be better correlated with supply air temperature than, for example, coil temperature or ambient temperature. 
     Embodiments under the present disclosure can use the supply air temperature to determine when the HVAC compressor can be turned off to extract the maximum amount of energy from the coils. Once the supply air reaches saturation point, a stage one cooling signal can be released. The compressor can re-engage once the energy has been falling or compressor time-out has been reached, whichever one is longer. Functionality can be disabled when additional stages of cooling are needed. The functionality can also apply to heat-pump systems for heating. 
     Controller  150  and thermostat  152  can share controlling capabilities, or one or the other may control system  100 . When controller  150  or thermostat  152  receive a command for a certain level of cooling or heating, they can detect the supply air temperature at sensor  159  and within the space at thermostat  152  (or other temperatures such as any or multiple of temperatures at sensors  154 ,  156 ,  157 ,  158 ,  199 ). Over time, controller  150  and/or thermostat  152  can learn what inputs lead to a given output temperature. Controller  150  and/or thermostat  152  can react accordingly by performing various actions, including examples such as: open or close inlet  112 , turn on or off coil  170 , open or close gate  124 , open or close outlet  128 , turn on or off blowers  105 , turn on or off compressor  160  and more. 
     Some embodiments of system  100  can comprise a head end controller  198 , or other type of controller that interfaces with a pre-existing system  100 . For example, head end controller can comprise a connection to any one of controller  150 , thermostat  152 , or sensor  199 . Head end controller  198  can comprise circuitry operable to interface with any of elements  150 ,  152 ,  199  and thereby communicate and interact with system  100 . One example of a head end controller  198  is a JACE (Java Application Control Engine). A head end controller  198  may be useful in many situations, for example, a situation with a pre-existing HVAC system  100  that lacks certain features, such as those described in the present disclosure. A head end controller  198  can be installed and can be used to direct the activities of system  100 . 
     A possible embodiment under the present disclosure can comprise the following. Thermostat  152  receives a command for setting the temperature within a space to 70° F. If the outside air at sensor  154  is 90° F., then thermostat  152  will send a command directing components  160 ,  170  of the HVAC cycle to turn on, or increase load, or decrease load. If outside air is 65° F., then thermostat  152  will command compressor  160  to turn off, therefore ending heat transfer across coil  170 . Outside air  110  will enter the system and supply the bulk or all of the supply airstream  185 . This will cool the conditioned space until the temperature equals 70° F. In this scenario, for example, supply air may measure at 68° F., at sensor  159 . During this process, recycled air  126  may be used as well. Thermostat  152  can determine how much, if any, recycled air  126  to use, and may close and open gate  124  accordingly. Similarly, thermostat  152  can turn on and off enthalpy wheel  180 . Thermostat  152  can make these adjustments based on set standards within software or hardware, or it may use historical data about how temperatures of 70 F within a space relate to supply air temperature at sensor  159 , and ambient air temperature at sensor  154 . 
     In another situation, a command for heating may be received at thermostat  152 . For example, temperature in a space may be 65° F., and thermostat  152  may be set raise the temperature to 75° F. If the outside air, measured at sensor  154 , is 50° F., then thermostat  152  (or controller  150 ) will direct the system to begin a heating cycle. However, if outside air is 85° F., then the thermostat  152  (or controller  150 ) can direct the system to use outside air  110  to provide supply air  185 . Doing so may or may not include mixing with return air  120  and recycled air  126 . How much outside air  110 , how much recycled air  126 , how long for each air stream, and other factors, can be determined by temperature readings at thermostat  152 , temperature readings at sensor  159 , and/or other temperature readings. In addition, thermostat  152  and/or controller  150  can make adjustments based on saved values/settings in memory, or on the basis of historical data maintained by the thermostat  152  (or controller  150 , or a cloud-based server connected to thermostat  152 ), dealing with relations among the different sensors and system behavior. For example, thermostat  152  and/or controller  150  may save data on how outside air temperature affects supply air temperature depending on whether the compressor is running or not, whether return air is recycled, or other factors. Relationships among any of the sensors  152 ,  154 ,  156 ,  157 ,  158 ,  159  can be used. Any of the sensors  152 ,  154 ,  156 ,  157 ,  158 ,  159 ,  199  can also (or alternatively) comprise humidity, pressure, or other sensors, or any combination thereof. These values can be used as well to predict the effects of different actions. For example, high or low humidity readings within the conditioned space can cause the thermostat  152 /controller  150  to power on or off the coil  170 . 
     A preferred method embodiment  700  under the present disclosure can be seen in  FIG. 7 . At  710 , a temperature request is received. At  720 , a temperature is determined within a space. At  725 , it is determined that heating is required. At  730 , the compressor for the heat pump is turned on and heating elements may be turned on. At  735 , it is determined whether the sensor in the supply air has reached an predetermined level. If yes, then at  740  the compressor and/or heating elements are turned off and on to modulate supply temperature to satisfy the temperature request. If no, then at  745  the process continues with normal operations. If cooling is required instead of heating, then instead of proceeding from  720  to  725 , the process proceeds to  750 . At  755 , compressors are turned on. At  760 , it is determined if the sensor in the supply air has reached a predetermined level. If yes, then at  765  compressor(s) are turned off and on to modulate supply temperature to satisfy the temperature request. If no, then at  745  the process continues with normal operations. Turning the compressors off and on, as in method  700 , or in other methods under the present disclosure, can take a variety of forms. Generally, the hotter the ambient temperature, the longer the compressors will be left on, as this helps efficiency of the system. Typically, the compressors are turned off and on depending on the resulting temperatures recorded in the space or in the supply air, or depending on another temperature reading. The modulating of the compressor operation can resemble a frequency adjusted wave, such that if resulting temperatures allow (such as in the space or supply air) for it, the compressors will be turned off on the shortest time frame allowable. 
     Other possible method embodiments under the present disclosure can stand on their own, or may incorporate at least a portion of method  700  into their embodiments. 
       FIG. 2  displays a possible method embodiment  200  under the present disclosure. At  210 , a temperature request is received. At  220 , the temperature within the space to be heated or cooled is determined. At  230 , an ambient temperature is determined. At  240 , it is determined whether ambient air can be used to fulfill the temperature request without the compressor running. If the answer is yes, then at  250  the compressor is powered off or maintained in an ‘off’ state. Then at  260  ambient air is supplied to the space. If the answer is no, then at  270 , the compressor is powered on or maintained in an ‘on’ state. Then at  280 , the HVAC system is allowed to operate normally in response to the temperature request. Alternatively, steps  260  and  280  can be replaced by directing the process to step  710  of method  700  of  FIG. 7 , and proceeding with the steps of method  700 . 
       FIG. 3  displays another possible method embodiment  300  under the present disclosure. At  310 , a temperature request is received. At  320 , a temperature is determined in the interior of a space to be conditioned. At  330 , an ambient temperature is determined. At  340 , it is determined whether ambient air can be used to fulfill the temperature request without the compressor running. If not, then at  350  the HVAC system is allowed to operate normally. If so, then at  360  the operation of the compressor is restricted. At  370 , a determination is made of at least one of: a supply air temperature, a coil temperature, an HVAC cabinet temperature, and a return air temperature. At  380 , an adjustment is made to operation of at least one of an enthalpy wheel, a heat exchanger, a blower, or a gate based on the ambient temperature, interior temperature, and at least one of a supply air temperature, a coil temperature, an HVAC cabinet temperature, and a return air temperature. Optionally, method  300  may comprise going from step  370  to step  710  method  700  of  FIG. 7 , processing through method  700 , and then returning to step  380 . 
       FIG. 4  displays another possible embodiment of a process  400  under the present disclosure. At  410 , a temperature request is received for a space. At  415 , a basis temperature is determined for the space. At  420 , an ambient temperature is determined. At  425 , it is determined that ambient air can be used to fulfill the temperature request without compressor operation. At  430 , operation of at least one compressor in the HVAC system is restricted. At  435 , ambient air is supplied to the space. At  440 , a supply air temperature is determined. At  445 , a current space temperature is determined. At  450 , an operation of the HVAC system is adjusted based on at least the determined supply air temperature, the determined current temperature of the space, and the determined ambient temperature. At  455 , it is determined if the temperature request has been met. If not, then the process can return to step  435 . If so, then the process can operate normally at step  460 . From there the process can return to step  410  when another temperature request is received. Optionally, method  400  can comprise proceeding from step  445  to step  710  of method  700  of  FIG. 7 , processing through method  700 , and then returning to step  455 , then proceeding with method  400 . 
       FIG. 5  displays another possible embodiment of a method  500  under the present disclosure. At  505 , a refrigerant or thermal transfer source (such as chilled or hot water) is circulated in an HVAC system. At  510 , a temperature is determined in a conditioned space. At  515 , a request is received to change the temperature to a chosen temperature. At  520 , an ambient temperature is determined. At  525 , a determination is made that the request is to heat the space and the determined ambient temperature is greater than the determined temperature of the space or that the request is to cool the space and the determined ambient temperature is less than the determined temperature of the space. At  530 , operation of at least one compressor and/or cooling or heating process is restricted. At  535 , ambient air is used for at least a portion of the supply air of the HVAC system. At  540 , a change in temperature of the supply air is determined. At  545 , a change in temperature of the space is determined. At  550 , a change in ambient temperature is determined. These changes in temperature may be zero. At  555 , an operation of the HVAC system is adjusted based on at least the determined changes in temperature of the supply air, the space, and the ambient temperature. At  560 , it is determined if the temperature request has been met. If not, then the process can return to step  535 . If so, the process can return to step  505 . Optionally, process  500  can comprise going from step  550  to step  710  of method  700  of  FIG. 7 , proceeding through method  700 , and then returning to step  560 . 
       FIG. 6  displays another possible embodiment of a method  600  under the present disclosure for operating an HVAC system. At  610 , a temperature request is received. At  615 , the temperature in a space is determined. At  620 , ambient temperature is determined. In some method embodiments, such as shown partially in  FIG. 7 , the ambient temperature may not need to be determined. At  625 , a determinations is made whether the requested temperature is greater or less than the space temperature. If greater, then at  630 , it is determined if the ambient temperature is greater than the space temperature. If less, then at  640  it is determined if the ambient temperature is less than the space temperature. At either  630  or  640 , if the answer is no, then the process goes to step  635  and the HVAC system is operated under normal control procedures. At  630 ,  640 , if the answer is yes, then the process goes to step  645  and operation of at least one compressor in the HVAC system is restricted. At  650 , the supply air temperature is determined. At  655 , the current spaced temperature is determined. At  660 , at least one operation of the HVAC system is adjusted based on at least the supply air temperature, the current space temperature, and the ambient temperature. At  665 , it is determined if the temperature request has been met. If not, the process returns to step  650 . If yes, then the process returns to step  610 . Optionally, process  600  may go from step  655  to step  710  of method  700  of  FIG. 7 , proceed through method  700  and then return to step  665 . 
     The embodiments described can be combined in a variety of ways. Method embodiments can be joined together. Temperature requests can be by direct input from a user, or also from software or settings. Remote commands can also be received by wireless or wired communication or from users using cloud software or mobile apps. Elements of, for example,  FIG. 1  can be joined together via wired or wireless communication. Numerous systems of the type displayed in  FIG. 1  can be joined together, and a remote command center can be in communication with the system shown or with a group of systems. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.