HVAC System with Leak Detection and Method of Use

The application is a continuation of U.S. patent application Ser. No. 18/532,471 filed Dec. 7, 2023, entitled “HVAC SYSTEM WITH LEAK DETECTION AND METHOD OF USE,” which is incorporated herein by reference.

This disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems. More particularly, this disclosure relates to an HVAC system with leak detection and method of use.

Heating, ventilation, and air conditioning (HVAC) systems are used to regulate environmental conditions within an enclosed space. Air is cooled via heat transfer with refrigerant flowing through the HVAC system and returned to the enclosed space as conditioned air.

Regulations in the HVAC industry are pushing manufacturers to transition away from traditional refrigerants towards low global warming potential (GWP) refrigerants, particularly mildly flammable (A2L) refrigerants. To accommodate for the changes, manufacturers may need to design HVAC systems to be optimized specific to the A2L refrigerants (e.g., R-32 and/or R-454B). Particularly, the HVAC systems may need a sensor to sense the mildly flammable A2L refrigerant in the event of a leak. The provided systems and methods are integrated into the practical application of using a combination of leak detection sensors and one or more loss of charge sensor to identify a location of a leak within the HVAC system. The provided systems and methods provide several practical applications and technical advantages. For example, the provided system and methods provide an improvement to the underlying technology via the leak detection sensors and the one or more loss of charge sensor which provides an alert that identifies the location of a leak in the HVAC system. Refrigerant leaks reduce the efficiency of the HVAC system and increase energy requirements to operate the system. Providing the user with an indication of a refrigerant leak and providing a technician with the location of the leak improves the underlying technology by mitigating refrigerant leaks within HVAC system and increasing the speed at which the leak can be addressed the technician.

In some embodiments, a heating, ventilation and air conditioning (HVAC) system is provided. The HVAC system comprises an outdoor unit that comprises a condenser configured to receive refrigerant. The HVAC system comprises an indoor unit that comprises an expansion valve configured to receive the refrigerant from the condenser, an evaporator configured to receive the refrigerant from the expansion valve, a blower configured to move airflow across the evaporator, and a first leak detection sense. The HVAC system comprises at least one loss of charge sensor configured to measure at least one loss of charge parameter of the refrigerant flowing through the HVAC system. The HVAC system comprises a control panel unit that comprises a compressor configured to receive the refrigerant from the evaporator, a second leak detection sensor, and a controller. The controller comprises a memory and a processor, where the memory is operable to store at least a first loss of charge threshold, a first predetermined wait time, and a gas concentration threshold. The processor is operatively coupled to the memory and configured to receive, from the at least one loss of charge sensor, at least a first loss of charge parameter. The processor is further configured to determine that refrigerant leak diagnostics should be performed for the HVAC system based on a comparison of at least the first loss of charge parameter to the at least one loss of charge threshold. The processor is configured to turn the compressor and the blower off for the first predetermined wait time in response to the comparison of the first loss of charge parameter to the at least one loss of charge threshold. The processor is further configured to receive, from the first leak detection sensor after the first predetermined wait time, a measurement that is indicative of a concentration of the refrigerant in the indoor unit, and receive, from the second leak detection sensor, a measurement that is indicative of a concentration of the refrigerant in the control panel unit. The processor is further configured to determine a leak location of the refrigerant, where (i) if the concentration of the refrigerant in the indoor unit and the control panel is less than the gas concentration threshold, the processor is configure to determine that the leak location of the refrigerant is in the outdoor unit of the HVAC system; (ii) if the concentration of the refrigerant in the indoor unit is greater than the gas concentration threshold, the processor is configured to determine that the leak location is in the indoor unit of the HVAC system; (iii) if the concentration of the refrigerant in the control panel unit is greater than the gas concentration threshold, the processor is configured to determine that the leak location is in the control panel unit of the HVAC system.

Certain embodiments of the present disclosure may include some, or none of these advantages. These advantages and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

Embodiments of the present disclosure and its advantages are best understood by referring toof the drawings, like numerals being used for like and corresponding parts of the various drawings.

Regulations in the HVAC industry are pushing manufacturers to transition away from traditional refrigerants towards low global warming potential (GWP) refrigerants, particularly mildly flammable (A2L) refrigerants. To accommodate for the changes, manufacturers may need to design HVAC systems to be optimized specific to the A2L refrigerants (e.g., R-32 and/or R-454B). Particularly, the HVAC systems may need a sensor to sense the mildly flammable A2L refrigerant in the event of a leak. The provided systems and methods are integrated into the practical application of using a combination of leak detection sensors and one or more loss of charge sensor to identify a location of a leak within the HVAC system.

show an example HVAC systemaccording to an embodiment of the present disclosure. The HVAC systemconditions air for delivery to a conditioned space (e.g., all or a portion of a room, a house, an office building, a warehouse, or the like). In some embodiments, the HVAC systemis a rooftop unit (RTU) that is positioned on the roof of a building, and the conditioned air is delivered into the interior of the building. In other embodiments, portion(s) of the HVAC systemmay be located within the building and portion(s) outside the building. The HVAC systemmay be configured as shown inor in any other suitable configuration. For example, the HVAC systemmay include additional components or may omit one or more components shown in.

In general, the HVAC systemincludes a working fluid conduit, a controller, a compressor, a condenser, a fan, an expansion valve, an evaporator, a blower, one or more loss of charge sensor-(e.g., a suction pressure sensor, a first condenser sensor, a second condenser sensor, a first evaporator sensor, a second evaporator sensor), a first leak detection sensor, and a second leak detection sensor. The HVAC systemincludes a control panel unitthat includes the controller, the compressor, the first loss of charge sensor (e.g., the suction pressure sensor), and the second leak detection sensor. The HVAC systemincludes an outdoor unitthat includes the condenser, the fan, a second loss of charge sensor (e.g., the first condenser sensor), and a third loss of charge sensor (e.g., the second condenser sensor). The HVAC systemincludes an indoor unitthat includes the expansion valve, the evaporator, the blower, a fourth loss of charge sensor (e.g., the first evaporator sensor), a fifth loss of charge sensor (e.g., the second evaporator sensor), and a first leak detection sensor.

As will be described in greater detail below, the controlleris generally configured to determine that refrigerant leak diagnosticsshould be performed. The refrigerant leak diagnosticsmay determine a leak locationfor the refrigerant leak. For example, the controllermay receive one or more loss of charge parametersfrom the one or more loss of charge sensors-. The controllermay determine that refrigerant leak diagnosticsshould be performed based on a comparison of one or more of the loss of charge parametersto one or more loss of charge thresholds(e.g., a suction pressureis less than a suction pressure threshold, a superheat valueis greater than a superheat threshold, and/or a subcooled valueis less than a subcooled value threshold). The controllermay turn off the compressorand the blowerfor a predetermined wait timein response to the comparison of the one or more loss of charge parametersto the one or more loss of charge thresholds. The controllermay receive a measurement that is indicative of a first concentrationof the refrigerant in the indoor unitfrom the first leak detection sensorafter the predetermined wait time. The controllermay also receive a measurement that is indicative of a second concentrationof the refrigerant in the control panel unitfrom the second leak detection sensor. The controllermay determine the leak locationof the refrigerant. For example, if the first concentrationof the refrigerant in the indoor unitand the second concentrationof the refrigerant in the control panel unitis less than a gas concentration threshold(e.g., less than 12% of a lower flammability limit of the refrigerant), then the controllermay determine that the leak locationis in the outdoor unit. If the first concentrationof the refrigerant in the indoor unitis greater than the gas concentration threshold, the controllermay determine that the leak locationis in the indoor unit. If the second concentrationof the refrigerant in the control panel unitis greater than the gas concentration threshold, the controllermay determine that the leak locationis in the control panel unitof the HVAC system.

In some embodiments, the working fluid conduitfacilitates the movement of a working fluid (e.g., one or more refrigerants) through a cooling cycle such that the working fluid flows as illustrated by the dashed arrows in. The working fluid may be any acceptable working fluid including, but not limited to, fluorocarbons (e.g., chlorofluorocarbons), ammonia, non-halogenated hydrocarbons (e.g., propane), or hydrofluorocarbons (e.g., R-410A). In some embodiments, the working fluid comprises a mildly flammable A2L refrigerant. As used herein, the term “mildly flammable A2L refrigerant” may be defined in one embodiment according to ASHRAE Standard 34. In one example, according to the ASHRAE Standard 34, the mildly flammable A2L refrigerant meets all four of the following conditions: (i) exhibits flame propagation when tested at 140° F. (60° C.) and 14.7 psia (101.3 kPa); (ii) has a lower flammability limit (LFL)>0.0062 lb/ft(0.10 kg/m); (iii) has a heat of combustion<8169 Btu/lb (19,000 KJ/kg); and (iv) has a maximum burning velocity of ≤3.9 in/s (10 cm/s) when tested at 73.4° F. (23° C.) and 14.7 psia (101.3 kPa) in dry air. Suitable examples of mildly flammable A2L refrigerants include, but are not limited to, R-32, R-454b, or combinations thereof.

In some embodiments, the working fluid conduitincludes a suction linethat places the evaporatorin fluid communication with the compressor, a discharge linethat places the compressorin fluid communication with the condenser, and a liquid linethat places the condenser in fluid communication with the evaporator. In some embodiments, the indoor unitincludes a first portionof the suction lineand the control panel unitincludes a second portionof the suction line. In some embodiments, the control panel unitincludes a first portionof the discharge lineand the outdoor unit includes a second portionof the discharge line. In some embodiments, the outdoor unitincludes a first portionof the liquid line, the control panel unitincludes a second portionof the liquid line, and the indoor unitincludes a third portionof the liquid line.

The compressoris coupled to the working fluid conduitand compresses (i.e., increases the pressure) of the working fluid. The compressoris in signal communication with the controllerusing wired and/or wireless connection. The controllerprovides commands and/or signals to control operation of the compressorand/or receive signals form the compressorcorresponding to a status of the compressor. The compressormay be a single-speed, variable-speed, or multiple stage compressor. A variable-speed compressor is generally configured to operate at different speeds to increase the pressure of the working fluid to keep the working fluid moving along the working fluid conduit. In the variable-speed compressor configuration, the speed of compressorcan be modified to adjust the cooling capacity of the HVAC system. Meanwhile, in the multi-stage compressor configuration, one or more compressors can be turned on or off to adjust the cooling capacity of the HVAC system.

The condenseris configured to facilitate movement of the working fluid through the working fluid conduit. The condenseris generally located downstream of the compressorand is configured to remove heat from the working fluid. The condenseris generally any heat exchanger configured to transfer heat between airflowflowing across the condenserand the refrigerant flowing through the condenser. The condensermay include one or more circuits of coils. The fanis configured to move airflowacross the condenser. For example, the fanmay be configured to blow outside air through the condenserto help cool the working fluid flowing therethrough. The fanmay be in communication with the controller(e.g., via wired and/or wireless communication) to receive control signals for turning the fanon and off and/or adjusting a speed of the fan. The compressed, cooled working fluid flows from the condensertoward the expansion valve.

The expansion valveis coupled to the working fluid conduitdownstream of the condenserand is configured to remove pressure from the working fluid. In this way, the working fluid is delivered to the evaporator. In general, the expansion valvemay be a valve such as an expansion valve or a flow control valve (e.g., a thermostatic expansion valve (TXV)) or any other suitable valve for removing pressure from the working fluid while, optionally, providing control of the rate of flow of the working fluid. The expansion valvemay be in communication with the controller(e.g., via wired and/or wireless communication) to receive control signals for opening and/or closing associated valves and/or to provide flow measurement signals corresponding to the rate of working fluid flow through the working fluid conduit.

The evaporatoris generally any heat exchanger configured to provide heat transfer between air flowing across the evaporator(i.e., airflowcontacting an outer surface of one or more coils of the evaporator) and working fluid passing through the interior of the evaporator. The evaporatormay include one or more circuits of coils. The evaporatoris fluidically connected to the compressor, such that working fluid generally flows from the evaporatorto the compressorwhen the HVAC systemis operating to provide cooling.

A portion of the HVAC systemis configured to move airflowprovided by the bloweracross the evaporatorand out of a duct systemas conditioned airflow. Return air, which may be air returning from the building, fresh air from outside, or some combination, is pulled into a return duct. A suction side of the blowerpulls the return air. The blowerdischarges the airflowinto a ductsuch that the airflowcrosses the evaporatorto produce conditioned airflow. The bloweris any mechanism for providing the airflowthrough the HVAC system. For example, the blowermay be a constant speed or variable speed circulation blower or fan. Examples of a variable speed blower include, but are not limited to, belt-drive blowers controlled by inverters, direct-drive blowers with electronic commuted motors (ECM), or any other suitable type of blower.

illustrates the HVAC systemoperating in a cooling mode. In some embodiments, the HVAC systemmay be operated as a heat pump in a heating mode. Generally, when the HVAC systemis operating in the heating mode, the flow of refrigerant is reversed, such that the condenseracts an evaporator and the evaporatoracts as a condenser to heat the flow of air passing therethrough. If the HVAC systemis configured to operate as a heat pump, the HVAC systemmay include a reversing valve to reverse the flow of working fluid through the HVAC systemduring operation in the heating mode and an outdoor expansion device for expanding the working fluid provided to the condenser, which acts an evaporator in the heating mode. During the heating mode, the HVAC systemmay include a heating element to provide supplemental and/or backup heating to the flow of air.

The HVAC systemincludes at least one loss of charge sensors-that are configured to measure one or more loss of charge parameterof the refrigerant flowing through the HVAC system. In some embodiments, the one or more loss of charge sensors-includes a suction pressure sensoroperable to measure one or more suction pressuresof the compressor. In some embodiments, the suction pressure sensoris positioned proximate to an inlet of the compressor. While the suction pressure sensoris illustrated near the inlet of the compressor, the suction pressure sensormay be located at any position in the suction line. The suction pressure sensoris configured to measure one or more suction pressuresof the refrigerant in the suction line. As will be detailed below, a loss of suction pressure of the refrigerant during operation may be indicative of a loss of charge of the refrigerant (i.e., a refrigerant leak in the HVAC system). For example, the controllermay store a suction pressure thresholdin a memory, and the controllermay determine that refrigerant leak diagnosticsshould be performed when the suction pressure sensormeasures a suction pressurethat is less than the suction pressure threshold. In one non-limiting example, the suction pressure thresholdis set to 100 psig. The suction pressure sensormay be in wired and/or wireless signal communication with controllerto provide signals corresponding to the one or more suction pressuresmeasured by the suction pressure sensor

Referring to, the one or more loss of charge sensors-may include a first condenser sensorand a second condenser sensor. The first condenser sensormay be configured to measure a saturated liquid temperatureof the working fluid flowing in the condenser, and configured to provide a corresponding saturated liquid temperature signal to the controller. As used herein, a “saturated liquid” may refer to a working 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. The first condenser sensormay be a temperature sensor such as a thermocouple or a thermistor. In some embodiments, the first condenser sensoris a pressure sensor (e.g., to measure a saturated liquid temperatureindirectly via a measure of saturation pressure).

Similarly, a second condenser sensormay be configured to measure one or more subcooled liquid temperaturesof the working fluid in and/or exiting the condenser, and configured to provide a corresponding subcooled liquid temperature signal to the controller. A “subcooled liquid” may refer to a fluid in the liquid state that is cooled below the saturation temperature of the fluid at a given pressure. The second condenser sensormay be a temperature sensor such as a thermocouple or a thermistor. Referring tomomentarily, the first condenser sensormay be located approximately at the center of the length of a circuit of the condenser. This location may correspond to a position where the working fluid flowing through the condenseris a saturated liquid. The second condenser sensormay be located on or near an exit of a subcooled circuit of the condenseron a portion of the liquid linejust after the outlet of the condenser. The first condenser sensorand the second condenser sensormay be attached on or within the condenserand/or the working fluid conduitusing any appropriate means (e.g., clamps, adhesives, or the like).

As will be detailed below, the controllermay determine a subcooled valuebased on a difference between a subcooled liquid temperaturemeasured by the second condenser sensorand a saturated liquid temperaturemeasured by the first condenser sensor. The subcooled valuemay be indicative of a loss of charge (i.e., a refrigerant leak) in the HVAC system. For example, a subcooled valuethat falls at or below a subcooled value thresholdmay be indicative of a loss of charge of the refrigerant in the HVAC system. The controllermay store the subcooled value thresholdin the memory, and the controllermay determine that refrigerant leak diagnosticsshould be performed when the subcooled valueis less than or equal to the subcooled value threshold. In one non-limiting example, the subcooled value thresholdis set to 4° F.

Referring to, the one or more loss of charge sensors-may include a first evaporator sensorand a second evaporator sensor. The first evaporator sensormay be configured to measure one or more saturated suction temperaturesof the working fluid following in the evaporator, and configured to provide a corresponding saturated suction temperature signal to the controller. The first evaporator sensormay be a temperature sensor such as a thermocouple or a thermistor. In some embodiments, the first evaporator sensormay be a pressure sensor (e.g., to measure a saturated suction temperature indirectly via a measure of saturation pressure). Similarly, a second evaporator sensormay be configured to measure one or more suction temperaturesof the working fluid in and/or exiting the evaporator, and configured to provide a corresponding suction temperature signal to the controller. The second evaporator sensormay be a temperature sensor such as a thermocouple or a thermistor. Referring tomomentarily, the first evaporator sensormay be located approximately on or near an end of a distributor line (e.g., a line from the outlet of the expansion valveto the inlet of the evaporator). This location may correspond to a position where the working fluid flowing through, or into, the evaporatoris a saturated vapor. The second evaporator sensormay be located on or near the outlet of the evaporator. For instance, the second evaporator sensormay be located in a portion of the evaporatorcontaining a superheated vapor working fluid or in a portion of the suction lineleading towards the compressor. A “superheated vapor” may refer 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. The first evaporator sensorand the second evaporator sensormay be attached on or within the evaporatoror working fluid conduitusing any appropriate means (clamps, adhesives, or the like).

As will be detailed below, the controllermay determine a superheat valuebased on a difference between the suction temperaturemeasured by the second evaporator sensorand the saturated suction temperaturemeasured by the first evaporator sensor. The superheat valuemay be indicative of a loss of charge in the HVAC system. For example, a superheat valuethat falls at or above a superheat value thresholdmay be indicative of a loss of charge of the refrigerant tin the HVAC system. The controllermay store the superheat value thresholdin the memory, and the controllermay determine that refrigerant leak diagnosticsshould be performed when the superheat valueis greater than or equal to the superheat value threshold. In one non-limiting example, the superheat value threshold is set to 25° F.

The HVAC systemincludes a first leak detection sensorin signal communication with the controller(e.g., via wired and/or wireless connection). The first leak detection sensoris positioned in the indoor unit. For example, the first leak detection sensormay be positioned adjacent to the duct system, the evaporator, the suction line, and/or the liquid line. Although a single sensor is depicted, it is to be appreciated that multiple sensors could be in the indoor unit. The first leak detection sensoris configured to generate a measurement that is indicative of a first concentrationof refrigerant that has leaked to the indoor unit, and configured to provide a corresponding measurement signal to the controller. The HVAC systemincludes a second leak detection sensorin signal communication with the controller(e.g., via wired and/or wireless connection). The second leak detection sensoris positioned in the control panel unit. For example, the second leak detection sensormay be positioned adjacent to the compressor, the controller, the suction line, or the discharge linein the control panel unit. Although a single sensor is depicted, it is to be appreciated that multiple sensors could be in the control panel unit. The second leak detection sensoris configured to generate a measurement that is indicative of a second concentrationof refrigerant that has leaked to the control panel unit, and configured to provide a corresponding measurement signal to the controller. As shown in, the HVAC systemmay include a housingthat comprises a first partitionthat separates the first leak detection sensorin the indoor unitfrom the second leak detection sensorin the control panel unit. The first partitionmay further separate the indoor unitfrom the outdoor unit. The housingmay further include a second partition that separates the control panel unitfrom the outdoor unit. Each of the first partitionand the second partitionmay include one or more openings to allow the working fluid conduitto pass therethrough and place the various components of the respective units in fluid communication, as described above.

In some embodiments, the first leak detection sensorand the second leak detection sensorare speed of sound sensors. The speed of sound sensor may include a transmitter configured to emit a sonic signal through the air to a receiver at a known distance. The speed of sound sensor measures a travel time of the sonic signal between the transmitter and the receiver as it travels through the air to determine a speed of sound (e.g., acoustic velocity) of the sonic signal in the air. The speed of sound sensor is configured to detect working fluid that leaks into the air because the working fluid leak will change the density of the air, which will in turn change the travel time of the sonic signal through the air. The speed of sound sensor can measure the change in the speed of sound through the air. The change of the speed of sound is indicative of the gas leak, and the controllermay compare the measured value to a calibration curve to generate a concentrationof the working fluid that has leaked into either the control panel unitor the indoor unit. The calibration curve can be constructed and stored in the controllerby measuring speed of sound values for known concentrations of refrigerants. In some embodiments, the speed of sound sensor takes a baseline measurement when no gas leak is present in the air and the controllerstores a reference speed of sound measurement for air. The change in the speed of sound measurement may be determined by the difference between the measured speed of sound value through the air and the baseline measurement, or difference between the measured speed of sound value and the reference speed of sound measurement.

In some embodiments, the first leak detection sensorand the second leak detection sensorare thermal conductivity sensors. The thermal conductivity sensors are configured to detect a change in thermal conductivity due to the working fluid leak relative to the thermal conductivity of air. Alternatively, the thermal conductivity sensor may detect the change in the thermal conductivity relative to a reference thermal conductivity of a known reference gas (e.g., nitrogen) in a sealed reference chamber. The thermal conductivity sensor may include an electrically heated filament in a detector body. When air enters the detector body the filament heats up and a resistance is measured. For example, the filament may be arranged in a Wheatstone bridge circuit so that the presence of the air in the detector body produces a measurable resistance. Air containing the working fluid leak will result in a change in the resistance measured. In some embodiments, the thermal conductivity sensor takes a baseline measurement when no gas leak is present in the air and the controllerstores a reference thermal conductivity measurement for air. The change in the thermal conductivity may be determined by the difference between the measured thermal conductivity value and the baseline measurement, or the difference between the measured thermal conductivity value and the reference thermal conductivity measurement. The thermal conductivity sensor can measure the change in the resistance, and the controllermay compare the measured value to a calibration curve to generate a concentrationof the working fluid leak. The calibration curve can be constructed and stored in the controllerby measuring thermal conductivity for known concentrations of refrigerants. The calibration curves can be constructed for a range of temperatures and pressures. As will be detailed below, the controllermay compare the first concentrationor the second concentrationto a gas concentration thresholdto determine if a working fluid has leaked into the indoor unitand/or the control panel unit. In one non-limiting example, the gas concentration thresholdis set to 12% of the lower flammability limit (LFL) of the refrigerant.

Referring to, the controlleris communicatively coupled (e.g., via wired and/or wireless connection) to components in the HVAC systemand configured to control their operation. In some embodiments, controllercan be one or more controllers associated with one or more components of the HVAC system. The controllerincludes a processor, memory, and an input/output (I/O) interface. The controllermay communicate with a display, which may be configured to display an alert or notificationthat contains a leak locationof the working fluid leak. In some embodiments, the displayis on a thermostat that is in communication with the HVAC system, or any other suitable displayin communication with the controller(e.g., a user's phone, computer, etc.).

The processorcomprises one or more processors operably coupled to the memory. The processoris any electronic circuitry including, but not limited to, state machines, one or more central processing unit (CPU) chips, logic units, cores (e.g., a multi-core processor), field-programmable gate array (FPGAs), application specific integrated circuits (ASICs), or digital signal processors (DSPs) that communicatively couples to memoryand controls the operation of HVAC system. The processormay be a programmable logic device, a microcontroller, a microprocessor, or any suitable combination of the preceding. The processoris communicatively coupled to and in signal communication with the memory. The one or more processors are configured to process data and may be implemented in hardware or software. For example, the processormay be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. The processormay include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memoryand executes them by directing the coordinated operations of the ALU, registers, and other components. The processormay include other hardware and software that operates to process information, control the HVAC system, and perform any of the functions described herein. The processoris not limited to a single processing device and may encompass multiple processing devices.

The memoryincludes 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 and data that are read during program execution. The memorymay 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 memoryis operable to store any suitable set of instructions, logic, rules, and/or code for executing the functions described in this disclosure. For example, the memorymay store loss of charge parameters(e.g., saturated liquid temperatures, saturated suction temperatures, suction temperatures, subcooled liquid temperatures, superheat values, subcooled values, and suction pressures), loss of charge thresholds(e.g., suction pressure threshold, superheat value threshold, subcooled value threshold), predetermined wait time, gas concentration thresholds, concentration(e.g., a first concentration, a second concentration), blower and fan instructions, valve instructions, compressor instructions, refrigerant leak diagnostics, leak location, and alert/notificationinstructions.

The I/O interfaceis configured to communicate data and signals with other devices. For example, the I/O interfacemay be configured to communicate electrical signals with the other components of the HVAC system. The I/O interfacemay comprise ports and/or terminals for establishing signal communications between the controllerand other devices. The I/O interfacemay be configured to enable wired and/or wireless communications. Connections between various components of the HVAC systemand between components of HVAC systemmay be wired or wireless. For example, conventional cable and contacts may be used to couple the various components of the HVAC system, including, the compressor, the expansion valve, the blower, the one or more loss of charge sensors-, the first leak detection sensor, the second leak detection sensor, and the display. In some embodiments, a data bus couples various components of the HVAC systemtogether such that data is communicated there between. 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 systemto 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 controllerto other components of the HVAC system.

illustrates an example operational flowof operating the HVAC systemof. The operational flowcan be logically described in three parts. The first part includes operations-, which generally includes compressing a refrigerant in a compressor, transferring heat between the refrigerant and an airflowin a condenser, reducing the pressure of the refrigerant in an expansion valve, transferring heat between the refrigerant and an airflowin an evaporator. The second part includes operations-, which generally include determining whether a first leak detection sensorin the indoor unitis triggered, and determining if the second leak detection sensorin the control panel unitis triggered. If the first leak detection sensoris triggered, the second part includes determining that the leak locationof the refrigerant is in the indoor unit, and if the second leak detection sensoris triggered, the second part includes determining that the leak locationof the refrigerant is in the control panel unit. If neither of the first leak detection sensornor the second leak detection sensorare triggered, then the operational flowproceeds to the third part. The third part generally includes operations-, which generally includes determining whether a loss of charge sensor-is triggered. If one of the loss of charge sensors-is triggered, the third part includes turning off the compressorand the blowerfor a predetermined wait time, determining whether the first leak detection sensorof the indoor unitis triggered after the predetermined wait time. If the first leak detection sensorof the indoor unitis triggered after the predetermined wait time, the third part includes determining that the leak locationof the refrigerant is in the indoor unit. If the first leak detection sensorof the indoor unitis not triggered after the predetermined wait time, the third part includes determining that the leak locationof the refrigerant is in the outdoor unit. The third part may further include generating an alert or notificationindicating the leak location, and optionally displaying the alert or notificationon the display.

At operation, the operational flowincludes compressing the refrigerant using the compressorin the control panel unitof the HVAC system. For example, the compressormay receive refrigerant from the evaporatorvia the suction line. The compressormay compress the refrigerant and transport the refrigerant to the condenservia the discharge line. At operation, the operational flowincludes transferring heat between the airflowflowing across the condenserand the refrigerant flowing through the condenserin the outdoor unit. The compressed, cooled refrigerant flows from the condenserin the outdoor unitto the expansion valvein the indoor unitvia the liquid line.

At operation, the operational flowincludes reducing the pressure of the refrigerant using the expansion valvein the indoor unit. The expansion valvemay be in communication with the controller(e.g., via wired and/or wireless communication) to receive control signals for opening and/or closing associated valves and/or to provide flow measurement signals corresponding to the rate of the refrigerant flowing through the liquid line. At operation, the operational flowincludes transferring heat between airflowflowing across the evaporatorand refrigerant flowing through the evaporatorin the indoor unitto produce a conditioned airflowthat is delivered to a target space.

At decision block, the operational flowincludes determining if the first leak detection sensoris triggered within the indoor unit. Decision blockmay include receiving a measurement that is indicative of a first concentrationof refrigerant that has leaked into the indoor unitusing the first leak detection sensor. As described in detail above, the first leak detection sensormay be a thermal conductivity sensor or a speed of sound sensor. The controllermay receive the change in thermal conductivity and/or speed of sound of the air in the indoor unitto determine a first concentrationof refrigerant in the indoor unit. Decision blockmay further include using the controllerto compare the first concentrationof the refrigerant in the indoor unitto a gas concentration threshold. In some embodiments, the gas concentration thresholdis 12% of a lower flammability limit (LFL) of the refrigerant in the indoor unit. If the first concentrationof the refrigerant in the indoor unitexceeds the gas concentration threshold, then the operational flowmay proceed to operation. At operation, the operational flowincludes determining that the leak locationof the refrigerant is in the indoor unit. If the first concentrationof the refrigerant in the indoor unitis less than the gas concentration threshold, then the operational flowproceeds to decision block.

At decision block, the operational flowincludes determining if the second leak detection sensoris triggered within the control panel unit. Decision blockmay include receiving a measurement that is indicative of a second concentrationof refrigerant that has leaked into the control panel unitusing the second leak detection sensor. As described in detail above, the second leak detection sensormay be a thermal conductivity sensor or a speed of sound sensor. The controllermay receive the change in thermal conductivity and/or speed of sound of the air in the control panel unitto determine a second concentrationof refrigerant in the control panel unit. Decision blockmay further include using the controllerto compare the second concentrationof the refrigerant in the control panel unitto the gas concentration threshold. If the second concentrationof the refrigerant in the control panel unitexceeds the gas concentration threshold, then the operational flowmay proceed to operation. At operation, the operational flowincludes determining that the leak locationof the refrigerant is in the control panel unit. If the second concentrationof the refrigerant in the control panel unitis less than the gas concentration threshold, then the operational flowproceeds to operation.

At operation, the operational flowincludes determining if the one or more loss of charge sensors-are triggered. Operationmay include having the controllerreceive at least a first loss of charge parameterfrom the one or more loss of charge sensors-. For example, the suction pressure sensormay be configured to measure a suction pressureof the compressor, the first condenser sensormay be configured to measure a saturated liquid temperatureof the refrigerant in the condenser, the second condenser sensormay be configured to measure a subcooled liquid temperatureof the refrigerant in and/or exiting the condenser, the first evaporator sensormay be configured to measure a saturated suction temperatureof the refrigerant flowing in the evaporator, and the second evaporator sensormay be configured to measure a suction temperature of the refrigerant in and/or exiting the evaporator. Operationmay further include determining that refrigerant leak diagnosticsshould be performed for the HVAC system based on a comparison of the first loss of charge parameterto a loss of charge threshold.

As detailed above, in one embodiment, the loss of charge thresholdmay include a suction pressure threshold. For example, operationmay include comparing the suction pressuremeasured by the suction pressure sensorto the suction pressure threshold. If the suction pressureis less than or equal to the suction pressure threshold(e.g., suction pressure is less than or equal to 100 psig), then the controllermay determine that a loss of charge is present in the HVAC systemand may proceed to perform refrigerant leak diagnosticsto identify a leak location.

Additionally or alternatively, the loss of charge thresholdmay include a subcooled value threshold. For example, operationmay include comparing a subcooled valueto a subcooled value threshold. The controllermay determine the subcooled valuebased on a difference between the subcooled liquid temperaturemeasured by the second condenser sensorand the saturated liquid temperaturemeasured by the first condenser sensor. If the subcooled valueis less than or equal to the subcooled value threshold(e.g., subcooled value is less than or equal to 4° F.), then the controllermay determine that a loss of charge is present in the HVAC systemand may proceed to perform refrigerant leak diagnosticsto identify the leak location.

Additionally or alternatively, the loss of charge thresholdmay include a superheat value threshold. For example, operationmay include comparing a superheat valueto a superheat value threshold. The controllermay determine the superheat valuebased on a difference between the suction temperaturemeasured by the second evaporator sensorand the saturated suction temperaturemeasured by the first evaporator sensor. If the superheat valueis greater than or equal to the superheat value threshold(e.g., superheat value is greater than or equal to 25° F.), then the controllermay determine that a loss of charge is present in the HVAC systemand may proceed to perform refrigerant leak diagnosticsto identify the leak location. If one of the loss of charge thresholdsis met, the operational flowproceeds to operation. If the one or more loss of charge thresholdsare not met, the operational flowmay return to operation.

At operation, the operational flowincludes turning off the compressorand the blowerfor a predetermined wait time. In some embodiments, the first concentrationof the refrigerant measured in the indoor unitat decision blockmay not be accurate during the operation of the HVAC system. This may be due to the fact that the blowermoves a substantial amount of airflowthrough the indoor unit, which may dilute the first concentrationof refrigerant that leaks into the indoor unit. Conversely, the second concentrationof the refrigerant measured in the control panel unitmay be more accurate during operation of the HVAC systemcompared to the indoor unitmeasurement because the control panel unitexperiences less airflow through the control panel unit(e.g., which may be due at least in part to the first partitionand the second partition). Turning off the HVAC systemby turning the blowerand the compressoroff allows for any refrigerant leak to accumulate to allow the first leak detection sensorto acquire a more accurate reading. In some embodiments, the predetermined wait timemay be from at least one minute to at least five minutes. However, any suitable predetermined wait timemay be utilized.

At decision block, the operational flowincludes determining if the first leak detection sensoris triggered within the indoor unitafter the predetermined wait time. Decision blockmay include receiving a measurement that is indicative of a third concentrationof refrigerant that has leaked into the indoor unitusing the first leak detection sensorafter the predetermined wait timehas elapsed. The controllermay receive a change in thermal conductivity and/or a speed of sound of the air in the indoor unitto determine the third concentrationof the refrigerant in the indoor unit. Decision blockmay further include using the controllerto compare the third concentrationof the refrigerant in the indoor unitto the gas concentration threshold. If the third concentrationof the refrigerant in the indoor unitexceeds the gas concentration threshold, then the operational flowmay proceed to operation. At operation, the operational flowincludes determining that the leak locationof the refrigerant is in the indoor unit. If the third concentrationof the refrigerant in the indoor unitis less than the gas concentration threshold, then operational flowproceeds to operation.

At operation, the operational flowincludes determining that the leak locationof the refrigerant is in the outdoor unit. In some embodiments, the controllermay determine that the leak locationis in the outdoor unitat least because decision blockand/or decision blockdetermined that the leak locationis not in the indoor unit, and decision blockdetermined that the leak locationis not in the control panel unit. The operational flowmay proceed to operation, which includes generating an alert or notificationthat indicates the leak location. Operationmay include displaying the alert or notificationon the display

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.