Patent Grant
11982452
This disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems and methods of their use. In particular, this disclosure relates to a temperature difference sensor for HVAC systems.
Heating, ventilation, and air conditioning (HVAC) systems are used to regulate environmental conditions within an enclosed space. Typically, HVAC systems include both an evaporator coil and a condenser coil. A blower of the HVAC system pulls warm air from the enclosed space and pushes the air across the evaporator coil to cool the air. The air is cooled via heat transfer with refrigerant flowing through the evaporator coil and returned to the enclosed space as conditioned air. Meanwhile, the refrigerant flowing through the evaporator coil is heated and generally transitions to the vapor phase. After being pressurized by a compressor, the heated vapor-phase refrigerant from the evaporator coil flows to the condenser coil where it is cooled and returned to a liquid state before flowing back to the evaporator coil to repeat the cycle. The temperature of the refrigerant flowing through the evaporator coil and the condenser coil can have an impact on HVAC system performance.
As described above, the temperature of the refrigerant flowing through the evaporator coil and the condenser coil can impact HVAC system performance. More particularly, temperature differences between the refrigerant flowing in different portions, or regions of these coils, can be used as a metric of the performance of the HVAC system or can indicate that maintenance (e.g., charging of the system with refrigerant) is required. One such temperature difference is the “superheat,” or the temperature difference between the temperature of the superheated vapor refrigerant and the saturation temperature of the refrigerant flowing through an evaporator coil of the HVAC system. Another example is the “subcool,” or the temperature difference between the saturation temperature of the refrigerant and the temperature of the subcooled liquid refrigerant flowing through a condenser coil of the HVAC system.
Conventionally, a temperature difference (such as “superheat” and “subcool”) is measured using two temperature sensors positioned at appropriate locations in the HVAC system. A controller generally receives, via an appropriate input interface, a signal from each sensor, and processing circuitry of the controller calculates the temperature difference using the temperatures measured by each sensor. For example, a temperature sensor may be disposed in a portion of the coil that has saturated liquid flowing therethrough (e.g., near the input or center of the coil), while another temperature sensor is disposed near the outlet of the evaporator coil. A temperature signal from each sensor is received by a controller of the HVAC system, and the superheat value is determined from the difference of the temperatures measured from these two signals. A similar approach can be used to measure the temperature difference between saturated liquid refrigerant and subcooled refrigerant in the condenser coil of the HVAC system.
This disclosure encompasses the recognition of problems of conventional approaches to measuring temperature differences in HVAC systems, such as those described above. In particular, the present disclosure encompasses the recognition that it may be impractical or prohibitively expensive to employ the large number of conventional sensors required to measure superheat and subcool in HVAC systems, particularly as the size and complexity of the HVAC system increases. For instance, HVAC systems increasingly include multi-circuited evaporator coils and condenser coils, such that each circuit uses not only two sensors to measure the corresponding temperature difference (subcool or superheat) but also the requisite controller hardware for receiving and processing each of the signals from these sensors. For example, for conventional temperature difference measurements, at least two signal inputs and the requisite interface hardware and circuitry for communicating and processing these signals are required for each evaporator and condenser circuit. Thus, an HVAC system with an evaporator coil and condenser coil that each have four circuits would use sixteen temperature sensors and a controller capable of receiving and processing sixteen temperature signals. Controller hardware can become prohibitively expensive and complex to manufacture and program as the number of signal inputs increases.
This disclosure contemplates an unconventional dual-thermistor sensor with a single signal output that provides a technical solution to the technical problems of conventional systems, including those described above. The sensor can be disposed in an HVAC system for example to measure superheat, subcool, or any other relevant temperature difference related to performance of the HVAC system. A system of the present disclosure, in certain embodiments, includes a first thermistor positioned to sense a saturated liquid temperature of the refrigerant flowing in a first portion of a condenser coil, a second thermistor sensor positioned to sense a liquid temperature of refrigerant flowing in a second portion of the condenser coil. The second thermistor is coupled electronically in series with the first thermistor, and the signal output of the temperature difference sensor is coupled to a terminal of the first thermistor and a terminal of the second thermistor. The signal output facilitates transmission of a temperature difference signal from the sensor.
The systems of the present disclosure provide an improvement to the technology used to measure temperature differences in HVAC systems. For example, the temperature difference sensor facilitates the accurate measurement of a temperature difference based on the temperature difference signal from the sensor, rather than relying on two temperature signals, each from a separate temperature sensor. As such, temperature differences may be measured using fewer electronic signals than was previously possible. The temperature difference sensor may be integrated into a practical application to measure temperature differences in HVAC systems, for example, where the availability of signal input/out output and signal processing hardware for receiving and processing signals may be limited (e.g., due to cost and/or size constraints).
Certain embodiments may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein.
For a more complete understanding of the present disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
Embodiments of the present disclosure and its advantages are best understood by referring to
As used in the present disclosure, a “saturated liquid” refers to a fluid in the liquid state that is in thermodynamic equilibrium with the vapor state of the fluid for a given pressure. A “saturated liquid” is said to be at the saturation temperature for a given pressure. If the temperature of a saturated liquid is increased above the saturation temperature, the saturated liquid generally begins to vaporize. A “superheated vapor” refers to a fluid in the vapor state that is heated to a temperature that is greater than the saturation temperature of the fluid at a given pressure. A “subcooled liquid” refers to a fluid in the liquid state that is cooled below the saturation temperature of the fluid at a given pressure.
Temperature Difference Sensor
In contrast to the temperature difference sensor 100, a conventional temperature sensor employs only a single thermistor rather than the two (thermistors 102 and 104) shown in
As described in greater detail below, the temperature difference sensor 100 presents several technical advantages that improve the operation of HVAC systems. For example, subcool can be measured for each condenser coil using a single signal (rather than the two required for conventional temperature difference measurements), thereby decreasing the signal input requirements for the hardware controllers by a factor of two. This can reduce or eliminate the need for expensive input interfaces for controllers in HVAC systems with multi-circuited coils while also freeing up controller inputs and processing resources for other HVAC monitoring and optimization tasks. For instance, superheat and subcool signals received from the sensors can be used, individually or collectively, to detect loss of charge in the HVAC system. The superheat and/or subcool signals can also be used as a metric for optimizing the settings of variable speed components of the HVAC system such as a variable speed blower, variable speed compressor, and/or variable speed outdoor fan (e.g., of a condenser unit).
HVAC System
The HVAC system 200 comprises a condensing unit 202, a metering device 210, an evaporator coil 212, a controller 234, a thermostat 242, and a refrigerant conduit subsystem 246. The refrigerant conduit subsystem 246 is operable to move a refrigerant through a cooling cycle (i.e., in a cycle through the evaporator coil 212, the condensing unit 202, and the metering device 210). The refrigerant may be any acceptable refrigerant including, but not limited to, fluorocarbons (e.g. chlorofluorocarbons), ammonia, non-halogenated hydrocarbons (e.g. propane), hydroflurocarbons (e.g. R-410A), or any other suitable type of refrigerant.
In some embodiments, the condensing unit 202 comprises a compressor 204, a condenser coil 206, and a fan 208. The compressor 204 is coupled to the refrigerant conduit subsystem 246 that compresses the refrigerant. In some embodiments, a compressor 204 may be configured to operate at multiple speeds or as a variable speed compressor. For example, the compressor 204 may be configured to operate at multiple predetermined speeds. In some embodiments, the compressor 204 is in signal communication with a controller 234 using a wired or wireless connection. The controller 234 is configured to provide commands or signals to control the operation of the compressor 204. For example, the controller 234 is configured to send signals to turn on or off one or more compressors 204 and/or to control the speed of the compressor 204. Additional information about the controller 234 is described below with respect to
The condenser coil 206 is downstream of the compressor 204 and configured for transferring heat from the refrigerant flowing through the condenser coil 206. The fan 208 is configured to move air 248 across the condenser coil 206. For example, the fan 208 may be configured to blow outside air across the condenser coil 206 (i.e., across the outer surface of the condenser coil 206) to help cool the refrigerant flowing therethrough. The compressed, cooled refrigerant from the condenser coil 206 flows downstream to an expansion device 210, or metering device. The fan 208 may be communicatively coupled via wired or wireless communication to the controller 234 so that the controller 234 may be used to adjust the speed of the fan 208.
The condenser coil 206 includes a first temperature difference sensor 260. The first temperature difference sensor 260 includes a first thermistor 262 and a second thermistor 264. Each of these thermistors 262, 264 is disposed at a different location along the length of the condenser coil 206 such that a temperature difference of refrigerant is measured between refrigerant in the appropriate thermodynamic states within the condenser coil 206. The first thermistor 262 is positioned to sense a temperature of the saturated liquid refrigerant, while the second thermistor 264 is positioned to sense a temperature of the subcooled liquid refrigerant. The first temperature difference sensor 260 is in signal communication with a controller 234 using a wired or wireless connection.
The first thermistor 262 may be electronically coupled to a supply voltage (e.g., with a corresponding of Vs in
Referring again to
The second thermistor 254 is generally coupled electronically to a supply voltage (e.g., corresponding to voltage 106 in
Referring again to
A portion of the HVAC system 200 is configured to move airflow 214 across the evaporator coil 212 and out of the duct sub-system 218 as airflow 216. Return airflow 220, which may include air returning from the building, fresh air from outside, or some combination, is pulled into a return duct 222. A suction side of a blower 224 pulls the return airflow 220. The blower 224 discharges airflow 214 into a duct 226 from where the airflow 214 crosses the evaporator coil 212 or heating elements (not shown) to produce the conditioned airflow 216. The blower 224 is any mechanism for providing a flow of air through the HVAC system 200. For example, the blower 224 may be a constant-speed or variable-speed circulation blower or fan. Examples of a variable-speed blower 224 include, but are not limited to, belt-drive blowers controlled by inverters, direct-drive blowers with electronic commuted motors (ECM), or any other suitable types of blowers.
The blower 224 is in signal communication with the controller 234 using any suitable type of wired or wireless connection 228. The controller 234 is configured to provide commands or signals to the blower 224 to control its operation. For example, the controller 234 may be configured to send signals to the blower 224 to control the fan speed of the variable-speed blower 224. In some embodiments, the controller 234 may be configured to send other commands or signals to the blower 224 to control any other functionality of the blower 224. In some embodiments, the controller is configured to facilitate adjustment and/or optimization of the operation of the blower 224 based signals from one or both of the first temperature difference sensor 260 and second temperature difference sensor 250.
The HVAC system 200 comprises one or more sensors 240 in signal communication with the controller 234. The sensors 240 may comprise any suitable type of sensor for measuring air temperature as well as other properties of a conditioned space (e.g. a room or building). The sensors 240 may be positioned anywhere within the conditioned space and/or the HVAC system 200. For example, the HVAC system 200 may comprise a sensor 240 positioned and configured to measure an outdoor air temperature. As another example, the HVAC system 200 may comprise a sensor 240 positioned and configured to measure a supply or treated air temperature and/or a return air temperature. In other examples, the HVAC system 200 may comprise sensors 240 positioned and configured to measure any other suitable type of air temperature (e.g., the temperature of air at one or more locations within the conditioned space). In some embodiments, each of sensors 240 may correspond to a temperature sensing element (e.g., thermistor) of a temperature difference sensor such as the sensor 100 illustrated in
The thermostat 242 is generally located within the conditioned space (e.g. a room or building) and is in signal communication with the controller 234 using any suitable type of wired or wireless communications, as shown in
As described, in certain embodiments, connections between various components of the HVAC system 200 are wired. For example, conventional cable and contacts may be used to couple the controller 234 to the various components of the HVAC system 200, including the blower 224, the compressor 204, the fan 208, the first temperature difference sensor 250, the second temperature difference sensor 260, and sensors 240. In some embodiments, a wireless connection is employed to provide at least some of the connections between components of the HVAC system 200 such as, for example, a connection between controller 234 and the variable-speed circulation fan 208 or any environment sensors 240 of system 200. In some embodiments, a data bus couples various components of the HVAC system 200 together such that data is communicated therebetween. In a typical embodiment, the data bus may include, for example, any combination of hardware, software embedded in a computer readable medium, or encoded logic incorporated in hardware or otherwise stored (e.g., firmware) to couple components of HVAC system 200 to each other. As an example and not by way of limitation, the data bus may include an Accelerated Graphics Port (AGP) or other graphics bus, a Controller Area Network (CAN) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or any other suitable bus or a combination of two or more of these. In various embodiments, the data bus may include any number, type, or configuration of data buses, where appropriate. In certain embodiments, one or more data buses (which may each include an address bus and a data bus) may couple the controller 234 to other components of the HVAC system 200.
In an example operation of system 200, a subcool signal 266 from first temperature difference sensor 260 is used to monitor the performance of HVAC system 200. During operation of condenser coil 206 it may be beneficial to ensure that refrigerant output to the evaporator coil 212 is entirely in the liquid phase (i.e., that no vapor-phase refrigerant is allowed to enter the evaporator coil 212). The subcool value is measured via the subcool signal 266 received from the first temperature difference sensor 260 (e.g., using a lookup table generated during calibration of the sensor 260) to confirm (e.g., continuously during operation) that an appropriate subcool value is achieved that corresponds to a fully liquid phase refrigerant output from the condenser coil 206. This prevents possible damage to the metering device 210 caused by flow of a vapor phase fluid through the metering device 210. A desired subcool value for optimal condenser coil 206 performance is generally in a range from about 6 to about 10° F. When the subcool value is less than this range, and particularly when the subcool value approaches 0° F., the condenser coil 206 typically may not be performing as intended.
In another example operation of the system 200, a subcool signal 266 from first temperature difference sensor 260 is used to detect a loss of charge in the HVAC system 200 (e.g., to detect a loss or leak of refrigerant from the HVAC system 200). For example, as described in greater detail with respect to method 500 below, the subcool value may be determined by accessing a calibration file (e.g., see TABLE 1 below) for the first temperature difference sensor 250 and identifying a subcool value (e.g., in degrees Fahrenheit) that corresponds to the subcool signal 256 (see TABLE 2 below). The controller 234 then determines whether the measured subcool value is less than a threshold subcool value (e.g., of about 6° F. or less) corresponding to a likely loss of charge. If the measured subcool value is less than or equal to the threshold value, the controller 234 determines that a loss of charge has occurred. The controller 234 may transmit an alert signal 236 to the thermostat 242 indicating this loss of charge. The alert signal may also or alternatively be transmitted to a service center or a device of a service technician such appropriate corrective steps may be taken to repair the system 200.
In another example operation of the HVAC system 200, the subcool signal 266 can be monitored while the HVAC system 200 is charged (e.g., filled) with refrigerant to determine when charging is complete. For example, once a desired subcool value (e.g., of 8° F., or a subcool value in a desired range (e.g., of between about 6 to about 10° F.) has been reached, charging might be considered completed and stopped. Generally, as the charge of refrigerant in the HVAC system 200 is increased, the subcool value increases.
In yet another example operation of HVAC system 200, a superheat signal 256 from second temperature difference sensor 250 is used to monitor the performance of HVAC system 200. For example, the controller 234 may determine a superheat value using the superheat signal 256 received from the superheat sensor 250 and use the superheat value to detect a loss of charge. For example, as described in greater detail with respect to method 500 below, the superheat value may be determined by accessing a calibration file (e.g., a lookup table) for the corresponding temperature difference sensor 250 and identifying a superheat value (e.g., in degrees Fahrenheit) that corresponds to the superheat signal 256 (see TABLE 2 below). A preferred superheat value is in a range from about 8 to 12° F. When the superheat value exceeds a certain temperature threshold (e.g., of greater than about 10 to 20° F.), no additional benefit is provided by the evaporator coil 212 (i.e., no improvement to the performance of system 200 is achieved). To prevent this wasted superheating and the associated waste of energy, the controller 234 may transmit an alert signal 236 to the thermostat 242 when the superheat value exceeds an efficiency threshold (e.g., of about 10 to 20° F.).
If the superheat value exceeds a maximum threshold (e.g., of about 20 to 30° F.) or the subcool value is less than a minimum threshold (e.g., 2° F.), the HVAC system 200 likely requires immediate attention. In some embodiments, the controller 234 is operable to automatically shut down when the superheat value exceeds the maximum superheat threshold or the subcool value is less than the minimum threshold to prevent damage to the HVAC system 200 or unnecessary expenditure of energy when the system 200 is not functioning properly. In some embodiments, the superheat value may be used to diagnose other performance issues of the HVAC system 200. For example, the superheat value may be monitored over time for gradual loss of charge or leak detection. For example, a relatively slow drift in the superheat value over time may be indicative of a slow leak of refrigerant form the system 200. In some embodiments, subcool value is monitored as a first measure of loss of charge, and superheat is monitored as a secondary measure. This is because when loss of charge occurs, the subcool value generally first goes to 0° F. before the superheat value begins to increase.
In another example operation of the HVAC system 200, a subcool signal 266 from sensor 260 and/or a superheat signal 256 from sensor 250 is used to optimize performance of the overall HVAC system 200. For example, measured subcool values and/or superheat values may be used to adjust the speed of one or more of the compressor 204, the fan 208, and the blower 224 to improve system performance. For example, if the controller 234 determines that the subcool value is lower than a performance threshold (e.g., of about 6° F.), the controller 234 may cause the speed of the fan 208 to increase in order to provide more cooling to the refrigerant passing through the condenser coil 206. For example, the speed of the fan 208 may be increased by a predetermined amount (e.g., corresponding to a speed increase of about 10%) or an amount proportional to the difference between the measured subcool value and a target subcool value (e.g., of 6° F.). After the speed of the fan 208 is increased, the subcool value will continue to be monitored to determine if further adjustment in the speed of fan 208 is needed to reach the target subcool value. A similar approach may be used to adjust the speed of the blower 224 and/or the compressor 204 to obtain a target subcool value, based on the subcool signal 266. Similarly, if the controller 234 determines that the superheat value is greater than a performance threshold (e.g., of about 10° F.), the controller 234 may determine that further heating of the refrigerant in the evaporator coil is not required and cause the speed of the blower 208 to decrease to conserve energy. The speed of the blower 208 may be decreased by a predetermined amount (e.g., of about 10%) or an amount proportional to the difference between the measured superheat value and the performance threshold value. For example, the speed of the compressor 208 may be decreased gradually until the superheat value is equal to or less than the performance threshold.
It should be understood that the temperature difference sensors described in the present disclosure are not limited to measuring refrigerant temperature differences in the condenser coil 206 and evaporator coil 212. One or more additional or alternate temperature difference sensors may be employed to measure any relevant temperature difference in the HVAC system 200 such as the temperature difference between return airflow 220 and conditioned airflow 216, which can also be used to monitor and optimize the performance of the HVAC system 200.
Example Method of Operation
At step 502, the controller 234 of HVAC system 200 receives a signal from temperature difference sensor 250 and/or 260. For instance, a subcool signal 266 may be received from subcool sensor 260 disposed on the condenser coil 206 of the HVAC system 200, and a superheat signal 256 may be received from superheat sensor 250 disposed on the evaporator coil 212 of the HVAC system 200.
At step 504, the controller 234 determines one or more temperature differences based on the received signal(s) from step 502. Each temperature difference may be determined for example by accessing a calibration file (e.g., a lookup table) for the corresponding temperature difference sensor 250 or 260 and identifying a temperature difference (e.g., in degrees Fahrenheit) that corresponds to the received signal. An example of the information included in a calibration file (e.g., a lookup table) for measuring a subcool value is shown in TABLE 1. As shown in TABLE 1, the subcool value generally increases with an increase in the subcool signal 266. An example of the information included in a calibration file for measuring a superheat value is shown in TABLE 2. Like the calibration information of TABLE 1, the superheat value generally increases with an increase in the superheat value 256. As shown in TABLE 2, the calibration information for the superheat value may include a broader range of temperatures (e.g., from 0 to 50° F.) compared to that of the subcool value (e.g., from 0 to 10° F.), because the superheat value can generally vary more widely during operation of the HVAC system 200.
The controller 234 may further determine an error or uncertainty associated with the measured temperature difference. For example, the calibration file may include, for each signal value, an associated temperature difference value and a temperature uncertainty value. The uncertainty value may provide supplemental information related to the accuracy of the temperature difference measurement and used to determine whether or to what extent a given measurement should be trusted (e.g., with an uncertainty value that is less than or equal to a threshold value) or not trusted (e.g., with an uncertainty value that is greater than or equal to the threshold value).
At step 506, the controller 234 may transmit the measured temperature difference for storage in a remote memory or store the temperature difference in a local memory (e.g., in a temperature difference log). For example, the controller 234 may access a table comprising previously measured temperature differences in a temperature difference log and add an entry to the table for the measured temperature difference. The entry generally includes a timestamp corresponding to the time when the temperature difference was measured and may also include any supplemental information related to the HVAC system 200 (e.g., a speed of fan 208, a refrigerant flow rate, a speed of compressor 204, a speed of blower 224, etc.). The saved temperature differences may be used for instantaneous determination of properties of system 200 (e.g., for detecting a loss of charge) and for long-term trend analysis (e.g., detecting slow leaks of refrigerant or other performance issues with system 200). For example, a slow decay in a superheat value may correspond to a gradual loss or slow leakage of refrigerant from the HVAC system 200.
At step 508, the controller 234 compares the determined temperature difference to a threshold value and determines whether threshold criteria are satisfied (e.g., whether a measured superheat value is greater than a superheat threshold or a measured subcool value is less than a subcool threshold). For a superheat value, for instance, the controller 234 may determine whether the measured superheat value is greater than a threshold superheat value (e.g., of about 20° F.). As described above, a preferred superheat value is generally in a range from about 8 to 12° F. If the superheat value is less than the threshold value, the system 200 is likely charged correctly, so the controller 234 does not determine that a loss of charge has occurred. In this case, the controller 234 returns to start and receives the next temperature difference signal for analysis. However, if the measured superheat value is greater than or equal to the threshold value, the controller determines that a loss of charge has occurred. At step 510, the controller 234 then proceeds to transmit an alert signal 234 indicating a loss of charge. The alert signal 234 may be sent to a display on the thermostat 242 of the HVAC system 200, so that a user is alerted to the loss of charge. The alert signal 234 may also or alternatively be transmitted to service center or any other appropriate device (e.g., a device of a service technician or a user of the HVAC system 200) such that corrective steps may be initiated to repair the system 200.
For a subcool value, at step 508, the controller 234 may determine whether the measured subcool value is less than a threshold subcool value (e.g., of about 6° F. or less). As described above, a preferred subcool value is generally in a range from about 6 to 10° F. If the subcool value is greater than the threshold value, the system 200 is likely charged correctly, so a loss of charge is not detected by the controller 234. In this case, the controller 234 returns to start and receives the next temperature difference signal for analysis. However, if the measured sub cool value is less than or equal to the threshold value, the controller 234 determines that a loss of charge has occurred. The controller 234 then proceeds to transmit an alert signal 234 indicating a loss of charge, at step 510. The alert signal 234 may be sent to a display on the thermostat 242 of the HVAC system 200, so that a user is alerted to the loss of charge. The alert signal 234 may also or alternatively be transmitted to service center or any other appropriate device (e.g., device of a service technician or a user of the HVAC system) such that corrective steps may be initiated to repair the system 200.
Modifications, additions, or omissions may be made to method 500 depicted in
Controller
The processor 602 may be a programmable logic device, a microcontroller, a microprocessor, or any suitable combination of the preceding. The processor 602 is communicatively coupled to and in signal communication with the memory 604. The one or more processors 602 are configured to process data and may be implemented in hardware or software. For example, the processor 602 may be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. The processor 602 may include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor 602 registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory 604 and executes them by directing the coordinated operations of the ALU, registers, and other components. The processor 602 may include other hardware and software that operates to process information, control the HVAC system 200 of
The processor 602 is configured to implement various instructions. For example, the processor 602 may be configured to execute instructions to implement the functions described above with respect to method 500. For example, the processor 602 may be configured to receive a signal from a temperature difference sensor (e.g., a superheat signal 256 and/or a subcool signal 266), compare the signal to a corresponding threshold value, and, based on this comparison, determine whether a loss of charge has occurred for the HVAC system 200.
The memory 604 comprises one or more disks, tape drives, or solid-state drives, and may be used as an over-flow data storage device, to store programs when such programs are selected for execution, and to store instructions 608 and data 614 that are read during program execution. The memory 604 may be volatile or non-volatile and may comprise ROM, RAM, ternary content-addressable memory (TCAM), dynamic random-access memory (DRAM), and static random-access memory (SRAM). The memory 604 is operable to store thresholds 610, calibration files 612, temperature difference logs 616, and any other data 614 or instructions 608. The instructions 608 comprise any suitable set of instructions, logic, rules, or code operable to execute functions described herein. The data 614 includes any other information stored within the memory 604 for use by the controller 234.
The thresholds 610 generally include threshold values corresponding to a condition of interest (e.g., a loss of charge) in the HVAC system. For example, the thresholds 610 may include a superheat threshold and a subcool threshold. If a superheat value is determined to be greater than the superheat threshold, the processor 602 generally determines that a loss of charge has occurred. Likewise, if a subcool value is determined to be less than the subcool threshold, the processor 602 determines that a loss of charge has occurred.
The calibration files 612 generally include one or more databases of predetermined temperature difference values corresponding to measured temperature difference signals from the temperature difference sensors 250 and 260. This calibration information may be stored in any appropriate format such as in one or more tables. For example, the superheat sensor 250 may be calibrated for superheat measurement by measuring the temperature difference signal (e.g., in units of volts) at different temperature conditions (e.g., with the first and second thermistors exposed to different known temperatures). The calibration files 612 may also include predetermined error or accuracy information for these values. This supplemental information may allow the processor 602 to determine a confidence level for measured temperature differences.
The temperature difference logs 616 generally include one or more databases of information, stored in an appropriate format, for temperature differences measured over time. The temperature difference logs 616 may be analyzed by the processor 602 or exported for external review. Trends in the historical temperature difference measurements may, in certain embodiments, be helpful for diagnosing problems associated with the HVAC system 200. For example, a gradual loss of charge may be identified from a slow drift in a temperature difference value over an extended period of time (e.g., of days, weeks, or months).
The I/O interface 606 is configured to communicate data and signals with other devices. For example, the I/O interface 606 may be configured to communicate electrical signals with the temperature difference sensors 250 and 260, the compressor 204, the blower 224, and the fan 208. The I/O interface may receive, for example, superheat signals 256, subcool signals 266, other temperature difference signals, thermostat calls, temperature setpoints, blower control signals, environmental conditions, and an operating mode status for the HVAC system and send electrical signals to the blower, compressor, and fan to control operation thereof. The I/O interface 606 may use any suitable type of communication protocol to communicate with the components of the HVAC system. The I/O interface 606 may comprise ports or terminals for establishing signal communications between the controller and other devices. The I/O interface 606 may be configured to enable wire and/or wireless communications.
While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.
In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.
To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants note that they do not intend any of the appended claims to invoke 35 U.S.C. § 112(f) as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.
| Number | Name | Date | Kind |
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| 4527399 | Lord | Jul 1985 | A |
| 20050204756 | Dobmeier | Sep 2005 | A1 |
| 20060112702 | Martin | Jun 2006 | A1 |
| 20090126375 | Toyoshima | May 2009 | A1 |
| 20150261233 | Duan | Sep 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 541076 | Dec 1976 | SU |
| Entry |
|---|
| Lobov, Evaporating Automatic Charging, Dec. 30, 1976, SU541076A1, Whole Document (Year: 1976). |
| Number | Date | Country | |
|---|---|---|---|
| 20200393151 A1 | Dec 2020 | US |
