FIELD OF THE INVENTION

[0001] This application relates to the field of air handling units for commercial buildings and, more particularly, to multi-stage air handling units for providing linear capacity output.

BACKGROUND

[0002] An air handling unit ("AHU") circulates and conditions air throughout a building in order to create a desired indoor environment. The AHU may include heating elements, cooling elements, fans, filters, mixing chambers, ducts, and controls. The cooling elements may include an evaporator, a condenser, a compressor, and an expansion valve. Air from rooms within the building is recirculated through the cooling coil and back to the rooms.

[0003] A rooftop unit ("RTU") is a particular type of AHU that is position outside of a building, such as a roof of the building. For the RTU, air from outside the building, as well as recirculated from the rooms, may pass through the cooling coil before continuing to the rooms of the building.1

[0004] Many conventional RTUs installed in the market may not meet current or future energy efficiency regulations. Also, many units selling currently on the market may require major changes in order to meet required energy standards. Cooling elements of a multi-stage rooftop unit, in particular, will be expensive to retrofit with compliant components in order to meet these new energy efficiency standards due to the replacement cost of higher efficiency compressors and related components.

SUMMARY

[0005] In accordance with one embodiment of the disclosure, there is provided a linear capacity output approach for retrofitting multi-stage air handling units to meet or exceed energy efficiency standards. The approach reduces redesign or retrofit costs substantially while increasing Integrated Energy Efficiency Ratio ("IEER") energy efficiency, hence meeting or exceeding the standards at minimum cost. [0006] One aspect is a multi-stage air handling unit for linear capacity output comprising condenser coils, expansion valves, evaporator coils, and compressors. The condenser coils being supported by the multi-stage air handling unit and to convert a refrigerant from a gas state to a liquid state to transfer heat to a first air medium. The expansion valves being coupled to the condenser coils and to decrease pressure in the refrigerant. The evaporator coils being coupled to the expansion valves and to convert the refrigerant from the liquid state to the gas state to transfer heat from a second air medium. The compressors being coupled to the evaporator coils and to increase pressure in the refrigerant and provide the linear capacity output. The compressors consist of one variable capacity compressor and at least one constant capacity compressor.

[0007] Another aspect is a system for analyzing a multi-stage air handling unit for linear capacity output comprising an input component, a processor, and an output component. The input component collects data associated with the multi-stage air handling unit having multiple compressors. The processor is coupled to the input component and identifies whether the compressors of the air handling unit include a scroll compressor based on the collected data. The processor also determines whether the compressors include a multi-stage compressor in response to identifying whether the compressors include the scroll compressor. The output component signals one or more remote devices to convert the air handling unit based on whether the compressors include the multi-stage compressor and operate multiple stages of the compressors as linear capacity output in response to converting the air handling unit.

[0008] Yet another aspect is a method for analyzing a multi-stage air handling unit for linear capacity output. Data associated with the multi-stage air handling unit having multiple compressors is collected. An identification is made regarding whether the compressors of the air handling unit include a scroll compressor based on the collected data. A determination is made regarding whether the compressors include a multi-stage compressor in response to identifying the scroll compressor. The air handling unit is converted based on whether the compressors include the multi-stage compressor. Multiple stages of the compressors are operated as linear capacity output in response to converting the air handling unit. [0009] The above-described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it would be desirable to provide one or more of these or other advantageous features, the teachings disclosed herein extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects.

[0011] FIG. l is a side planar view of a rooftop unit ("RTU") in an example implementation that is operable to employ techniques described herein.

[0012] FIG. 2 is a simplified, refrigeration circuit diagram of components of an air handling unit ("AHU"), such as the RTU of FIG. 1, in an example implementation.

[0013] FIG. 3 is a graphical view representing operation of the AHU of FIG. 2 in an example implementation relative to an operation of a conventional AHU.

[0014] FIG. 4 is a block diagram representing sample components of a variable frequency drive of FIG. 2 in an example implementation.

[0015] FIG. 5 is a flow diagram representing an operation of a control device of the AHU of FIG. 2 in an example implementation that is operable to employ techniques described herein.

DETAILED DESCRIPTION

[0016] Various technologies that pertain to systems and methods that facilitate linear capacity output of a multi-stage air handling unit will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0017] There is described systems and methods to retrofit multi-cooling stages into a linear capacity RTU with only one variable frequency drive or one variable speed/capacity compressor. In particular, the systems and methods utilize a 1+n topology (1 variable capacity compressor plus n constant capacity compressors) that couples with a digital rooftop unit controller and software to achieve linear capacity output in the whole range, thus improving the load efficiency to meet industry regulations. By retrofitting the AHU/RTU with only one variable frequency drive or one variable speed/capacity compressor, substantially all stages of the multi-stage unit run efficiently, thereby minimizing cost while providing efficient operation similar to, or exceeding, expensive units.

[0018] Referring to FIG. 1, there is shown an illustration of an environmental control system 100 in an example implementation that is operable to employ techniques described herein. An environmental control system 100 of a building manages heating, ventilation, and air conditioning (HVAC) components to control environmental conditions within the building. The system 100 may include an air handling unit, such as a rooftop unit 110, for allowing fresh air external to the building and/or return air internal to the building to circulate through the HVAC components and cool the environmental conditions of the building in an efficient manner. A logic controller 120 of the rooftop unit 110 operates in conjunction with other HVAC components to provide operational control for the system 100, such as configuring, commissioning, troubleshooting, and other control functions. The HVAC components of the rooftop unit 110 includes heating and/or cooling coils that modify, if necessary, the temperature of return air to generate supply air for the building. [0019] The logic controller 120 operates with other HVAC components to commission, troubleshoot, and otherwise operate the environmental control system 100. In particular, the rooftop unit 110 may include a variable frequency drive 130 to manage operation and efficiency of a variable capacity compressor 140, a mobile device 160 to support a mobile application and control the logic controller 120, and/or a cloud device 170 to provide additional functions to the logic controller, such as multi-site monitoring, fault detections & diagnostics, and alarm functions.

[0020] FIG. 2 represents an example control device 200, such as the logic controller 120, the mobile device 160, or the cloud device 170, of the environmental control system 100. The control device 200 may be any type of configuring, commissioning, troubleshooting, or other type of control device for operation of the various components of the environmental control system 100. The control device 200 includes a communication bus 202 for interconnecting the other device components directly or indirectly, one or more communication components 204 communicating other entities via a wired and/or wireless network, one or more processors 206, and one or more memory components 208.

[0021] The communication component 204 may utilize wireless technology for communication, such as, but are not limited to, cellular-based communications, Bluetooth (including BLE), ultrawide band (UWB), Wi-Fi (including Wi-Fi Direct), IEEE 802.15.4, Z-Wave, 6L0WPAN, Near-Field Communication, other types of electromagnetic radiation of a radio frequency wave, light-based communications (including infrared), acoustic communications, and any other type of peer-to-peer technology. The communication component 204 of the control device 200 may also utilize wired technology for communication, such as transmission of data over a physical conduit, e.g., an electrical cable or optical fiber cable.

[0022] The one or more processors 206 may execute code and process data received at other components of the control device 200, such as information received at the communication component 204 or stored at the memory component 208. The code associated with the environmental control system 100 and stored by the memory component 208 may include, but is not limited to, operating systems, applications, modules, drivers, and the like. An operating system includes executable code that controls basic functions of the control device 200, such as interactions among the various components of the control device, communication with external devices via the communication component 204, and storage and retrieval of code and data to and from the memory component 208.

[0023] Each application includes executable code to provide specific functionality for the processor 206 and/or remaining components of the control device 200. Examples of applications executable by the processor 206 include, but are not limited to, an identification module 210 for identifying an independent refrigeration circuit and a scroll compressor, and a determination module 212 for determining whether the compressors do not include a multi-stage compressor.

[0024] The processor 203 identifies an independent refrigeration circuit associated with the compressors of the air handling unit based on the collected data, determines whether one or more compressors includes a single-stage compressor in response to identifying the independent refrigeration circuit, and converts the single-stage compressor to a single multi-stage compressor in response to determining that the compressors do not include the multi-stage compressor. For some embodiments, the processor 203 identifies whether the compressor(s) include a scroll compressor based on the collected data. For some embodiments, the processor 203 determines that the compressors include one or more multi-stage compressors or determines that all compressors are single-stage compressors. The processor 203 may further setup a variable frequency drive based on a compressor voltage and a compressor horsepower in response to determining that the maximum capacity of the compressor(s) is taken into account.

[0025] Data is information that may be referenced and/or manipulated by an operating system or application for performing functions of the control device 200. Examples of data associated with control device operations and stored by the memory component 208 may include, but are not limited to, multi-stage air handling unit ("MAHU") data 214 having collected information associated with multi-stage air handling unit, and conversion data 216 utilized to converting a single-stage compressor/ driver to a single multi-stage compressor/driver.

[0026] The control device 200 may further include one or more input and/or output components 218 ("I/O interfaces"). A user interface 220 of the control device 200 may include portions of the input and/or output components 218 and be used to interact with a user of the control device. For example, the user interface 220 may include a combination of hardware and software to provide a user with a desired user experience.

[0027] The input and output components 218 may include other components 222-228 to facilitate operations of the system 100, such as HVAC sensors 222, HVAC controllers 224, communications with technicians 226, a variable frequency drive 228 for a variable capacity compressor, and the like. For example, the input component of the I/O interfaces 218 may collect data associated with the multi-stage air handling unit. The output component of the I/O interfaces 218 may operate each single-stage compressor for a predetermined capacity range and operate the single multi-stage compressor for at least a portion of each predetermined capacity range. The output component may also signal, via wired or wireless communication, to one or more remote devices to convert the air handling unit based on whether the compressors include the multi-state compressor. The output component may further operate multiple stages of the compressors as linear capacity output subsequent to, or in response to, converting the air handling unit.

[0028] The control device 200 may further include a power source 230, such as a power supply or a portable battery, for providing power to the other device components of the control device 200.

[0029] It is to be understood that FIG. 2 is provided for illustrative purposes only to represent examples of the internal components of the control device 200 and is not intended to be a complete diagram of the various components that may be utilized by the device. Therefore, the control device 200 may include various other components not shown in FIG. 2, may include a combination of two or more components, or a division of a particular component into two or more separate components, and still be within the scope of the present invention.

[0030] Referring to FIG. 3, there is shown a refrigeration circuit 300 of a multi-stage air handling unit ("AHU") that expels heat external to a facility by converting a chemical coolant, or refrigerant, between a gas state and a liquid state. For a packaged unit, such as a rooftop unit ("RTU"), the air handling unit is a single housing that supports substantially all of the components of the cooling subsystem. The multi-stage air handling unit includes condenser coils 310, expansion valves 320, evaporator coils 330, and compressors 340 operating together to transfer the refrigerant in a continuous loop of heat exchange and transfer. The refrigeration circuit 300 represents the multi-stage AHU/RTU after it has been retrofitted with a single multi-stage compressor (e.g., with variable frequency drive).

[0031] For some embodiments, the refrigeration circuit 300 of the multi-stage air handling unit for linear capacity output includes multiple condenser coils 310, multiple expansion valves 320, multiple evaporator coils 330, and multiple compressors 340. The refrigeration circuit 300 is supported by the multi-stage air handling unit. Although all components of the refrigeration circuit 300 may or may not be shown, the refrigeration circuit 300 generally couples the expansion valves 320 to the condenser coils 310, the evaporator coils 330 to the expansion valves, the compressors 340 to the evaporator coils, and the condenser coils to the compressors. The condenser coils 310 convert a refrigerant from a gas state to a liquid state to transfer heat to a first air medium, the expansion valves 320 decrease pressure in the refrigerant, the evaporator coils 330 convert the refrigerant from the liquid state to the gas state to transfer heat from a second air medium, and the compressors increase pressure in the refrigerant and provide the linear capacity output.

[0032] The refrigeration circuit 300 may include a single loop of components in which a first condenser coil 312 is coupled to a first expansion valve 322, which is coupled to a first evaporator coil 332, which is coupled to a first compressor 342, which is coupled back to the first condenser coil. The compressor consists of one variable capacity compressor that replaces a constant capacity compressor. The refrigeration circuit 300 may also include multiple loops. For example, the condenser coils 310 may include a first condenser coil 312 and a second condenser coil 314, the expansion valves 320 may include a first expansion valve 322 and a second expansion valve 324, and the evaporator coils 330 may include a first evaporator coil 332 and a second evaporator coil 334. The compressors 340 may include a first compressor 342 and a second compressor 344, in which the first compressor is a variable capacity compressor, and the second compressor is a constant capacity compressor. For other embodiments, other loops may be added to the circuit 300, such as a third condenser coil 316, a third expansion valve 326, a third evaporator coil 336, and a third compressor 346.

[0033] For the refrigeration circuit 300, each constant capacity compressor 344, 346 includes a single stage control device (not shown), and the one and only variable capacity compressor 342 includes a multi-stage control device 350. For example, the multi-stage control device 350 may be a variable frequency drive or motor drive of an electro-mechanical drive system to control speed and/or torque of the corresponding variable capacity compressor 342.

[0034] The refrigeration circuit 300 may further include a housing 360 to support the condenser coils 310, the expansion valves 320, the evaporator coils 330, and the compressors 340. For some embodiments, the housing 360 may include a compartment 362 for the compressors 340, and the variable capacity compressor 342 may be a replacement that substantially fits within an area of the compartment previously occupied by an original constant capacity compressor. For some embodiments, the housing 360 may include a compartment 362 for a multi-stage control device 350 to drive the variable capacity compressor 342, and the multi-stage control device is a replacement that substantially fits within an area of the compartment previously occupied by an original multi-stage control device.

[0035] Referring to FIG. 4, there is shown a graphical view 400 representing operation of the AHU in an example implementation relative to an operation of a conventional AHU. The y-axis 410 of the graphical view 400 represents compressor capacity in percent, and the x-axis 420 of the graphic view represents activation of compressors in which compressors may be activate and/or deactivated in sequence relative to each other. [0036] Conventional or legacy RTUs generally have two or three compressors having constant speed or constant capacity. For example, a system with three similar-capacity compressors may receive 33% total capacity with one compressor running, 67% total capacity with two compressors running, and 100% total capacity with three compressors running, as represented by conventional operation curve 430. Such a convectional system cannot provide 50% capacity, i.e., under powered when only Cl is active or overpowered when both Cl and C2 are active, leading to bad performance and energy waste/cost.

[0037] For the systems and methods described herein, by retrofitting a constant single-stage compressor with a multi-stage compressor, the compressor can directly accept a single multi-stage compressor, such as a variable frequency drive, and create a linear modulating curve, as represented by the present operation curve 440. The present operation curve 440 may or may not be linear but is substantially linear above a minimum capacity level 450. Accordingly, the system results in linear capacity modulating with only one variable capacity compressor in a multi-stages RTU. By utilizing a single variable capacity compressor instead of multiple ones, the system results in significant cost and energy savings, projected by some analyses to be about 20% compared to convention multi-stages RTUs. For some embodiments, a variable frequency drive may be retrofitted, i.e., added, where the compressors allow for variable frequency drives. For some embodiments, the AHU/RTU may be retrofitted with a variable speed compressor. For maintenance purposes, the rotation of compressors over time may be adjusted in accordance with a hybrid compressor mix of a multi-stage compressor and one or more single-stage (constant) compressors.

[0038] Referring to FIG. 5, there is shown a flow diagram illustrating a workflow 500 for retrofitting a multi-stage air handling unit, such as a rooftop unit, with a single compressor variable frequency drive for linear capacity output. For some embodiments, an operation of a control device of the AHU may execute in accordance with the workflow 500. The workflow 500 analyzes a multi-stage air handling unit for linear capacity output. The multi-stage AHU has multiple compressors, and data associated with the AHU is collected (502) by or at the control device. A scroll compressor is then identified (504) based on the collected data. If the compressors do not include a scroll compressor (504), then the compressor(s) and/or AHU are operated without converting any compressors or drivers.

[0039] Subsequent to identifying (504) the scroll compressor, the control device provides a signal to one or more remote devices to convert (506) the AHU. For some embodiments, the control device provides a signal to convert the single-stage scroll compressor to a single multi-stage scroll compressor. For some embodiments, all compressors of the AHU are single-stage compressors, whether determined by the control device or otherwise. In such case, a particular single-stage compressor, i.e., only one compressor, is converted (506) to a single multi-stage compressor in response to determining that all compressors are the single-stage compressors. For some embodiments, the conversion (506) of the single-stage compressor to the single multi-stage compressor includes setting-up a variable frequency drive based on a compressor voltage and a compressor horsepower. The remote device or devices include, but are not limited to, a mobile device associated with a technician or an automated equipment to perform the conversion without or with minimal human intervention.

[0040] The conversion (510) of the single-stage compressor to the multi-stage compressor may be accomplished manually by a technician or automatically by automated equipment. For example, the technician may receive a signal from the output component at a mobile device carried or otherwise associated with the technician. For another example, a robotic system on may be dispatched to the AHU/RTU to transport the multi-stage compressor, if necessary, and perform the function of disconnecting the single-stage compressor and connecting the multi-stage compressor. As yet another example, a multi-stage compressor may already exist at the AHU/RTU such that one or more valves or switches may be controlled to switch the relevant circuit from the single-stage compressor to the multi-stage compressor.

[0041] Subsequent to, or in response to, converting the AHU, the control device determines (508) whether the compressors include a multi-stage compressor and/or operate (510, 512, 516) multi-stages as linear capacity output. If the compressors include a multi-stage compressor (508), then the compressors and/or AHU operate (512) multi-stages as linear capacity output based on a second control strategy (Control Strategy 2 A). For some embodiments, none of the compressors of the AHU are replaced and other components of the AHU are updated, such as a compressor logic or drive, to implement the linear capacity output. For some embodiments, one or more compressors of the AHU may be replaced by the multi-stage compressor in order to implement or improve performance of linear capacity output.

[0042] In response to determining (508) that the compressors do not include a multistage compressor, then the compressors and/or AHU is operated (510) based on a first control strategy (Control Strategy 1) subsequent to, or in response to, converting (506) the AHU. Since the compressors do not include a multi-stage compressor, a single compressor retrofit is feasible, i.e., converting (506) a single-stage compressor to a multi-stage compressor. Accordingly, the compressor(s) and/or AHU may be operated (510) for linear capacity output after, or in response to, converting or retrofitting the compressor or driver. For some embodiments, each single-stage compressor is operated (510) for a predetermined capacity range and the single (sole) multi-stage compressor is operated for at least a portion, i.e., part or all, of each predetermined capacity range of the single-stage compressor or compressors.

[0043] For some embodiments, the workflow 500 of the multi-stage AHU may also comprise identifying (514) an independent refrigeration circuit associated with the compressors of the AHU. The circuit may be identified (514) based the collected data (502). Identifying (514) the inclusion of the independent refrigeration circuit may be performed after converting (506) the AHU and/or before detecting (508) whether the compressors include a multi-stage compressor. The inclusion of the independent refrigeration circuit may also be identified (514) in response to converting (506) the AHU. If the independent refrigeration circuit is not identified (514), then the compressor(s) and/or AHU operate (516) multi-stages as linear capacity output based on a third control strategy (Control Strategy 2B) where the refrigeration circuit is not independent. If the independent refrigeration circuit is identified (514), then the control device may proceed with operating multi-stages as linear capacity output (510, 512, 516) or determining (508) whether the compressors include a multi-stage compressor. [0044] Those skilled in the art will recognize that, for simplicity and clarity, the full structure and operation of all data processing systems suitable for use with the present disclosure are not being depicted or described herein. Also, none of the various features or processes described herein should be considered essential to any or all embodiments, except as described herein. Various features may be omitted or duplicated in various embodiments. Various processes described may be omitted, repeated, performed sequentially, concurrently, or in a different order. Various features and processes described herein can be combined in still other embodiments as may be described in the claims.

[0045] It is important to note that while the disclosure includes a description in the context of a fully functional system, those skilled in the art will appreciate that at least portions of the mechanism of the present disclosure are capable of being distributed in the form of instructions contained within a machine-usable, computer-usable, or computer-readable medium in any of a variety of forms, and that the present disclosure applies equally regardless of the particular type of instruction or signal bearing medium or storage medium utilized to actually carry out the distribution. Examples of machine usable/readable or computer usable/readable mediums include nonvolatile, hard-coded type mediums such as read only memories (ROMs) or erasable, electrically programmable read only memories (EEPROMs), and user- recordable type mediums such as floppy disks, hard disk drives and compact disk read only memories (CD-ROMs) or digital versatile disks (DVDs).

[0046] Although an example embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form.