Patent Application
20250067487
The present disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems and methods of their use, and more specifically to a system and method for identifying a refrigerant leak in multiple refrigeration circuits with one or more compressors.
Heating, ventilation, and air conditioning (HVAC) systems are used to regulate environmental conditions within an enclosed space. Air is cooled or heated via heat transfer with refrigerant flowing through the system and returned to the enclosed space as conditioned air. During operation, refrigerant may leak from the working-fluid conduit subsystem or from one or more components.
The system described in the present application provides several practical applications and technical advantages that overcome the current technical problems described herein. The following disclosure is particularly integrated into a practical application of improving refrigeration techniques by identifying and isolating circuits with a refrigerant leak while providing cooling using the refrigeration circuits which do not have a leak.
In general, the disclosed system improves the refrigeration technique by leveraging subcool (SC) values, superheat (SH) values, and (optionally) saturated suction temperature (SST) values to detect loss of charge, and in response, to determine that a set of conditions with respect to the SC, SH, and (optionally) SST values is met, determine a compressor circuit that is associated with the loss of charge, isolate the compressor circuit from other components of the heating, ventilation, and air conditioning (HVAC) system, execute a mitigation plan, and upon receiving a cooling demand, provide cooling by one or more other compressor circuits that are not associated with loss of charge.
In HVAC systems, particularly in rooftop unit (RTU) A2L HVAC systems with multiple compressor circuits, when a refrigerant leak is detected, it is not known which compressor circuit is associated with the refrigerant leak since the leak detection sensor is in the space shared by all compressor circuits. As a result, when a refrigerant leak is detected, in one approach, the HVAC system is shut-down and stops cooling operations. However, this approach is not efficient. For example, switching off the cooling unit of the HVAC system leads to a temperature rise in a room where the HVAC system is deployed, and therefore, discomfort for the people in the room. In another example, not utilizing other compressor circuits that are not associated with a refrigerant leak reduces the utilization efficiency of those compressor circuits.
This disclosure contemplates an unconventional system and method configured to leverage subcool, superheat, and saturated suction temperature values associated with different compressor circuits to detect which compressor circuit is associated with the loss of charge and therefore the refrigerant leak. For example, if a refrigerant leak is detected, the disclosed system may perform the following operations for each compressor circuit. For example, for each compressor circuit, the disclosed system may determine whether a subcool value, is less than a subcool threshold, a superheat value is greater than a superheat threshold, and optionally, if a saturation suction temperature is less than an SST threshold. If these conditions are met, the system may detect which compressor circuit is associated with the loss of charge and therefore the refrigerant leak. The disclosed system may then isolate the compressor circuit that is associated with the loss of charge. The disclosed system may also execute a mitigation plan to run/operate the blower to reduce the refrigerant concentration due to the refrigerant leak. Upon receiving an air conditioning request, the disclosed system may provide air conditioning using one or more other compressor circuits that are not associated with the loss of charge. The leak detection process and isolating of the refrigeration circuit may not affect the air conditioning operations of the HVAC system. Thus, the HVAC system is able to provide seamless air conditioning before, during, and after the detection of the leak. In other words, the HVAC system takes the air conditioning operation load from the refrigeration circuit that is associated with the leak and puts on (e.g., distributes) the air conditioning operation load among circuit(s) that are not associated with the refrigerant leak.
Accordingly, the disclosed system provides a practical application of improving refrigeration techniques by detecting which compressor circuit is responsible for, associated with, and contributes to the loss of charge and refrigerant leak, isolating the identified refrigeration circuit, and using other refrigeration circuit(s) to provide air conditioning. The disclosed system further provides an additional practical application of load balancing among the compressors, where the air conditioning operation load is balanced among compressor(s) that are not associated with the refrigerant leak and taken from those compressors that are associated with the refrigerant leak. The disclosed system further provides an additional practical application of identifying a location where the refrigerant leak has occurred, and a component associated with the leak.
In certain embodiments, an HVAC system comprises a set of refrigeration circuits, each with one or more compressors, a condenser, a subcool sensor circuit, a superheat sensor circuit, a refrigerant detection sensor circuit that is common to all the refrigeration circuits, and a processor. The set of refrigeration circuits comprises a first refrigeration circuit and a second refrigeration circuit. The first refrigeration circuit consists of one or more compressors configured to receive a first flow of a first refrigerant from a first evaporator coil and to discharge the first flow of refrigerant at a first higher pressure. The second refrigeration circuit consists of one or more compressors configured to receive a second flow of a second refrigerant from a second evaporator coil and to discharge the second flow of the second refrigerant at a second higher pressure. The condenser is configured to receive the first refrigerant and cool the first refrigerant flowing through. The subcool sensor circuit is configured to provide a subcool signal that indicates to a subcool value associated with the condenser, wherein the subcool value corresponds to a temperature difference between a saturated refrigerant and a subcooled refrigerant associated with the condenser. The superheat sensor circuit is configured to provide a superheat signal that indicates a superheat value corresponding to a temperature difference between a superheated refrigerant and a saturated refrigerant state associated with the evaporator pressure. The refrigerant detection sensor circuit is configured to detect a concentration of the first refrigerant in a volume. One or more processors could be operably coupled to the refrigerant detection sensor, a part of the sensor, on a separate control board connected to the sensor, or reside in both, the sensor and a separate control board. The processors are further operably coupled to the subcool sensor, and the superheat sensor. The processor is configured to receive sensor data from the refrigerant detection sensor, wherein the sensor data indicates the detected concentration of the first refrigerant in the volume. The processor is further configured to compare the detected concentration of the first refrigerant with a threshold concentration. The processor is further configured to determine that the detected concentration of the first refrigerant exceeds the threshold concentration. In response to determining that the detected concentration of the first refrigerant exceeds the threshold concentration, the processor is further configured to receive the subcool signal from the subcool sensor. The processor is further configured to determine the subcool value based at least in part upon the subcool signal. The processor is further configured to receive the superheat signal from the superheat sensor. The processor is further configured to determine the superheat value based at least in part upon the superheat signal. The processor is further configured to determine that the subcool value is less than a threshold subcool value. The processor is further configured to determine that the superheat value is more than a threshold superheat value. In response to determining that the subcool value is less than the threshold subcool value and that the superheat value is more than the threshold superheat value, the processor is further configured to determine that the first refrigerant is leaking from the first compressor, isolate the first refrigeration circuit from other components of the HVAC system, execute a mitigation plan to reduce a leak of the first refrigerant from the first compressor, and allow the remaining refrigeration circuits to operate independently to serve the space conditioning demands as they arise.
Certain embodiments of this disclosure may include some, all, 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.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.
As described above, previous technologies fail to provide an efficient, secure, and reliable solution to facilitate a more effective refrigerant leak identification by leveraging superheat signal, subcool signal, and saturated suction temperature in a refrigeration system, for example, in Heating, Ventilation, and Air Conditioning (HVAC) systems. Embodiments of the present disclosure and its advantages may be understood by referring to
The example HVAC system 100 includes at least two compression circuits which can generally be operated independently. The first compression circuit includes a first working-fluid conduit subsystem 102a, at least one condensing unit 104a, an expansion valve 122a, and an evaporator 124a. The second compression circuit includes a second working-fluid conduit subsystem 102b, at least one condensing unit 104b, an expansion valve 122b, and an evaporator 124b. The HVAC system 100 also includes a thermostat 154 and a controller 160.
The HVAC system 100 is generally configured to determine refrigerant leakages, loss of charge (i.e., loss of refrigerant) by monitoring properties of the HVAC system, as described in greater detail below. For instance, subcool signals 120a,b and superheat signals 138a,b (described in greater detail below) may be used to detect refrigerant leaks and determine whether the HVAC system is overcharged or undercharged with working fluid. In an example operation of HVAC system 100, subcool signals 120a, b, respectively, from subcool sensor circuits 118a,b, are used to monitor the performance of HVAC system 200. During operation of condenser coil, it may be beneficial to ensure that refrigerant output to the evaporator coil 121a,b is entirely in the liquid phase (i.e., that no vapor-phase refrigerant is allowed to enter the evaporator coil 121a,b).
The subcool sensor circuit 118a,b may be configured to provide a subcool signal 120a,b that indicates to a subcool value associated with the condenser 108a,b, respectively. The subcool value may correspond to a temperature difference between a saturated refrigerant and a subcooled refrigerant associated with the condenser 108a,b. A combination of pressure and temperature sensors could be used, for e.g., a pressure sensor is used to measure the pressure in the condenser which is then used to determine the saturation liquid temperature which is then used to determine subcooling. The first subcool value associated with the first condenser 108a is measured via the subcool signal 120a received from the first subcool sensor circuit 118a. Similarly, the second subcool value associated with the second condenser 108b is measured via the subcool signal 120b received from the second subcool sensor circuit 118b. Each subcool value may be measured or determined using a calibration file 162 (e.g., a lookup table) generated during calibration of the respective sensor 118a,b 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 108a,b. This prevents possible damage to the expansion valve 122a, b caused by flow of a vapor phase fluid through the expansion valve 122a,b. A desired subcool value for optimal condenser coil 108a,b performance is generally more than a range from about 5 to about 10° F. When the subcool value is less than this range, for example, if the subcool value is between about 0 to 3° F., there may be a refrigerant leak at the condenser coil 108a,b which causes the condenser could 108a,b not be performing as intended.
In another example operation of the HVAC system 100, a subcool signal 120a,b is used to detect a loss of charge in the HVAC system 100 (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 system 200 and method 300 below, the subcool value may be determined by accessing a calibration file 162 (e.g., a lookup table) for the subcool sensor circuit 118a, b and identifying a subcool value (e.g., in degrees Fahrenheit) that corresponds to the subcool signal 120a, b, respectively. The controller 160 then determines whether the measured subcool value is less than a threshold subcool value (e.g., of about range between 0 to 3° F.) corresponding to a likely loss of charge. If the measured subcool value is less than or equal to the threshold range, the controller 160 determines that a loss of charge has occurred. The controller 160 may transmit an alert signal 158 to the thermostat 154 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 100.
In the same or another example operation of the HVAC system 100, accessing, fetching, and/or recording the subcool signal 120a,b may be in response to detecting a refrigerant leak associated with a compressor 106a,b. For example, when a refrigerant leak is detected with respect to the compressor 106a, the subcool value indicated by the subcool signal 120a may be less than the threshold subcool. Similarly, when a refrigerant leak is detected with respect to the compressor 106b, the subcool indicated by the subcool signal 120b may be less than the threshold subcool. The determined subcool values and signals 120a,b may be used to determine the loss of charge, and isolate a compressor 106a,b that is associated with the refrigerant leak from other components of the HVAC system 100. Generally, as the charge of refrigerant in the HVAC system 100 is increased, the subcool value increases.
In another example operation of HVAC system 100, superheat signals 138a,b, respectively, received from superheat sensors 136a, b are used to monitor the performance of HVAC system 200. The superheat sensor circuit 136a,b, may be configured to provide a superheat signal 138a,b that indicates a superheat value corresponding to a temperature difference between a superheated refrigerant and a saturated refrigerant associated with the evaporator. A combination of pressure and temperature sensors could be used, for e.g., a pressure sensor is used to measure the pressure in the condenser which is then used to determine the saturation vapor temperature which is then used to determine superheating. For example, the controller 160 may determine a superheat value using the superheat signal 138a,b received from the superheat sensor 136a,b and use the superheat value to detect a loss of charge. For example, as described in greater detail with respect to system 200 and method 300 below, the superheat value may be determined by accessing a calibration file 164 (e.g., a lookup table) for the corresponding superheat sensor circuit 136a,b and identifying a superheat value (e.g., in degrees Fahrenheit) that corresponds to the superheat signal 138a,b, respectively. A preferred superheat value may be more than a range from about 5 to about 10° F. When the superheat value exceeds a certain temperature threshold (e.g., of greater than about 25 to 30° F.), no additional benefit is provided by the evaporator coil 121a,b (i.e., no improvement to the performance of system 100 is achieved). This may be an indication of a refrigerant leak and loss of charge associated with the compressor circuit 106a,b. To prevent this wasted superheating and the associated waste of energy, the controller 160 may transmit an alert signal 158 to the thermostat 154 when the superheat value exceeds an efficiency threshold (e.g., of about 25 to 30° F.)
If the superheat value exceeds a maximum threshold (e.g., of about 25 to 30° F.) and the subcool value is less than a minimum threshold (e.g., of about 0 to 3° F.), this may be an indication of loss of charge, for example, as a result of refrigerant leak at and associated with a compressor circuit 106a,b. Thus, if these conditions are met, the HVAC system 200 likely requires immediate attention. In some embodiments, if these conditions of superheat value and subcool value are met, the controller is operable to automatically isolate the particular compressor circuit(s) 106a,b that is determined to be associated with the loss of charge and refrigerant leak. For example, the controller 160 may switch off the particular compressor circuit(s) 106a,b and optionally close shut-off valves outlet and/or inlet to the particular compressor circuit(s) 106a,b to prevent damage to the HVAC system 100 or unnecessary expenditure of energy when the system 100 is not functioning properly. The controller 160 may also execute a mitigation plan that includes switching on the blower 144 by sending a turn-on command signal to the blower 144. The controller 160 may continue to provide air conditioning using one or more other compressor(s) 106a, b that are not associated with the loss of charge and refrigerant leak.
In some embodiments, the superheat value may be used to diagnose other performance issues of the HVAC system 100. 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 100. 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 100, a subcool signal 118a,b from sensor 118a,b and/or a superheat signal 138a,b from sensor 136a,b is used to improve the performance of the overall HVAC system 100. For example, measured subcool values and/or superheat values may be used to reduce the loss of charge and faster detection of refrigerant leak. For example, when it is determined that the superheat value exceeds a maximum threshold (e.g., of about 25 to 30° F.) and the subcool value is less than a minimum threshold (e.g., of about 0 to 3° F.), an alert message may be sent to a user device of a technician, where the alert message may indicate that loss of charge is detected with respect to the compressor circuit(s) 106a,b and that the HVAC system 100 needs service. In another example, to conserve the charge and energy, the compressor circuit 106a,b that is determined to be associated with the loss of charge may be switched off. In another example, the controller 160 may adjust the speed of one or more of the fan 110a,b, and the blower 114 to improve system performance. For example, if the controller 160 determines that the first compressor circuit 106a is associated with the loss of charge, the controller 160 may switch off the compressor circuit 106a, use the compressor circuit 106b to provide space conditioning or air conditioning, and (optionally) cause the speed of the fan 110b to increase in order to provide more air conditioning to the refrigerant passing through the condenser coil 122b. For example, the speed of the fan 110b 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 predefined target subcool value (e.g., more than 5 F). After the speed of the fan 110b is increased, the subcool value will continue to be monitored to determine if further adjustment in the speed of fan 110b is needed to reach the target subcool value. A similar approach may be used to adjust the speed of the blower 144 and/or the compressor circuit 106b to obtain a target subcool value, based on the subcool signal 120b. Similarly, if the controller 160 determines that the superheat value is greater than a performance threshold (e.g., of about 25 to 30° F.), the controller 160 may determine that further heating of the refrigerant in the evaporator coil is not required and cause the speed of the blower 144 to decrease to conserve energy. The speed of the blower 144 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 106a 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 108a,b and evaporator coil 122a,b. One or more additional or alternate temperature difference sensors may be employed to measure any relevant temperature difference in the HVAC system 100 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.
Each of the working fluid conduit subsystems 102a, b facilitates the movement of a working fluid (e.g., a refrigerant) through an air conditioning cycle such that the working fluid flows as illustrated by the dashed arrows in
Each of the condensing units 104a,b includes at least one compressor 106a,b, a condenser 108a,b, and a fan 110a,b. In some embodiments, one or both of the condensing units 104a,b is an outdoor unit while other components of system 100 may be indoors. The compressor 106a,b is coupled to the corresponding working-fluid conduit subsystem 102a,b and compresses (i.e., increases the pressure of) the working fluid. The compressors 106a,b may be single-speed, variable-speed or multi-stage compressors. 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 subsystem 102a,b. In the variable-speed compressor configuration, the speed of compressor 106a,b can be modified to adjust the air conditioning capacity of the HVAC system 100. Meanwhile, in the multi-stage compressor configuration, one or more compressors can be turned on or off to adjust the air conditioning capacity of the HVAC system 100. The compressor 106 of condensing unit 104 may be a variable speed compressor, a multi-speed compressor, a multi-stage compressor, among other types. In some embodiments, the compressor 106 may be connected to another compressor 106 in a HVAC unit. In some embodiments, multiple compressors 106 may be tandem compressors, each separately compressing the refrigerant and delivering the refrigerant to a common discharge manifold. In some embodiments, one or more compressors 106 may serve a single refrigeration circuit. In some embodiments, one or more compressors 106 may serve multiple refrigeration circuits.
Each compressor 106a,b is configured to receive a flow of refrigerant from a respective evaporator coil 121a,b and to discharge the flow of refrigerant at a respective higher pressure. For example, the compressor 106a may be configured to receive a first flow of a first refrigerant from the evaporator coil 121a and discharge the first flow of the first refrigerant at a first higher pressure, and the compressor 106b may be configured to receive a second flow of a second refrigerant from the evaporator coil 121b and discharge the second flow of the second refrigerant at a second higher pressure.
Each compressor 106a,b is in signal communication with the controller 160 using wired or wireless connection. The controller 160 provides commands or signals to control operation of the compressor 106a,b and/or receives signals from the compressor 106 corresponding to a status of the compressor 106a,b. For example, when a compressor 106a,b is a variable-speed compressor, the controller 160 may provide signals to control the compressor speed. When a compressor 106a,b operates as a multi-stage compressor, the signals may correspond to an indication of which compressors to turn on and off to adjust the compressor 106a,b for a given heating capacity, or in general, air conditioning capacity. The controller 160 may operate the compressor 106 in different modes corresponding to load conditions (e.g., the amount of cooling or heating required by the HVAC system 100).
Each condenser 108a,b is configured to facilitate movement of the working fluid through the corresponding working-fluid conduit subsystem 102a,b. Each condenser 108a,b is further configured to receive the respective refrigerant and cool the refrigerant flowing therethrough. For example, the condenser 108a is configured to receive the first refrigerant and cool the first refrigerant flowing therethrough, and the condenser 108b is configured to receive the second refrigerant and cool the second refrigerant flowing therethrough. Each condenser 108a,b is generally located downstream of the compressor 106a,b from the corresponding compression circuit and is configured to remove heat from the working fluid. Each fan 110a,b is configured to move air 112a,b across the condenser 108a,b from the corresponding compression circuit. For example, a fan 110a,b may be configured to blow outside air through the condenser 108a,b to help cool the working fluid flowing therethrough. The compressed, cooled working fluid flows from the condenser 108a,b toward an expansion device 122a,b of the corresponding compression circuit.
Each condenser 108a,b includes a corresponding first sensor 114ab and a second sensor 118a,b. In the example of
The first sensor 114a,b may be located approximately at the center of the length of a circuit of the condenser 108a,b. This location may correspond to a position where working fluid flowing through the condenser 108a,b is a saturated liquid. Alternatively, a pressure sensor 114a,b could be located at the outlet of the condenser to determine the pressure which can then be used to estimate a saturated liquid temperature. The second sensor 118a,b may be located on or near an exit of a subcool circuit 118a,b of the condenser 108a,b or on a fluid line (i.e., on or in the working-fluid conduit subsystem 102a,b) just after the outlet of the condenser 108a,b. Sensors 114a,b and 118a,b may generally be attached on or within the condenser 108a,b and/or working-fluid conduit subsystem 102a,b using any appropriate means (e.g., clamps, adhesives, or the like).
Each expansion device 122a,b is coupled to the corresponding working-fluid conduit subsystem 102a,b downstream of the condenser 108a,b and is configured to remove pressure from the working fluid. In this way, the working fluid is delivered to the evaporator 124a,b of the compression circuit and receives heat from airflow 126 to produce a conditioned airflow 128 that is delivered by a duct subsystem 130 to the conditioned space. In general, an expansion device 122a,b may be a valve such as an expansion valve or a flow control valve (e.g., a thermostatic expansion valve) 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. An expansion device 122a,b may be in communication with the controller 160 (e.g., via wired and/or wireless communication) to receive control signals for opening and/or closing associated valves and/or provide flow measurement signals corresponding to the rate of working fluid flow through the working fluid subsystem 102a,b.
The evaporator 124a,b of each compression circuit is generally any heat exchanger configured to provide heat transfer between air flowing through the evaporator 124a,b (i.e., air contacting an outer surface of one or more coils of the evaporator 124a,b) and working fluid passing through the interior of the evaporator 124a,b. For example, the evaporator 124a,b may be or include one or more evaporator coils 122a,b, respectively. In some embodiments, evaporators 124a,b are combined in a single coil unit. Airflow 126 flows first through evaporator 124a before flowing through evaporator 124b and being output as conditioned airflow 128. A portion of airflow 126 flows through evaporator 124a while a separate portion of airflow 126 flows through evaporator 124b.
Each evaporator 124a,b is fluidically connected to the compressor 106a,b of the corresponding compression circuit, such that working fluid generally flows from the evaporator 124a,b to the corresponding condensing unit 104a,b. A portion of the HVAC system 100 is configured to move air 126 across the evaporators 124a,b and out of the duct sub-system 130 as conditioned airflow 128. Return air 140a,b, which may include outdoor air 140a, indoor air 140b returning from the building, or some combination, is pulled into a return duct 142. A device 141 may be positioned on or in the duct 142 and include one or more dampers for modulating the amount of outside air 140a pulled into the return duct 142. When the HVAC system 100 is a rooftop unit (RTU), device 141 may be referred to as an economizer. Duct 142 may include additional dampers (not illustrated for clarity and conciseness), which may be configured, for example, to adjust the amount of indoor air 140b pulled into the duct 142.
Each evaporator 124a,b includes a corresponding third sensor 132a,b, a fourth sensor 136a,b, and fifth sensor(s) 137. In the example of
As shown in this illustrative example, the third sensor 132a,b may be located approximately on or near an end of a distributor line (e.g., a line from the outlet of the expansion device 122a,b to the inlet of the evaporator 124a,b). This location may correspond to a position where working fluid flowing through, or into, the evaporator 124a,b is a saturated vapor. The fourth sensor 136a,b may be located on or near the outlet of the evaporator 124a,b. For instance, a fourth sensor 136a,b may be located in a portion of the evaporator 124a,b containing a super-heated vapor working fluid or on a portion of the working-fluid conduit subsystem 102a,b leading towards the suction side of the compressor 106a,b. Sensors 132a,b and 136a,b may generally be attached on or within the evaporator 124a,b and/or working-fluid conduit subsystem 102a,b using any appropriate means (e.g., clamps, adhesives, or the like). The sensor 137 may be located at any location within the HVAC system 100, for example, upstream a compressor circuit 106a,b, downstream a compressor circuit 106a,b. upstream a evaporator 124a,b, downstream a evaporator 124a,b, respectively, among other locations.
A suction side of a blower 144 pulls the return air 140a,b. The blower 144 discharges airflow 126 into a duct 146 such that airflow 126 crosses the evaporators 124a,b or heating elements (not shown) to produce conditioned airflow 128. The blower 144 is any mechanism for providing a flow of air through the HVAC system 100. For example, the blower 144 may 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. The blower 144 is in signal communication with the controller 160 using any suitable type of wired or wireless connection. The controller 160 is configured to provide commands and/or signals to the blower 144 to control its operation (e.g., to adjust the airflow to operate at a prescribed CFM/ton value during a validation mode). The blower 144 may be a motor-driven component. The blower 144 may be positioned in a duct system and configured to move airflow across an indoor coil and out of the duct system.
The HVAC system 100 includes one or more sensors 148, 150, 152 in signal communication with the controller 160. The sensors 148, 150, 152 may include any suitable type of sensor for measuring air temperature, relative humidity, and/or any other properties of the conditioned space (e.g. a room or building), the HVAC system 100, and/or the surrounding environment (e.g., outdoors). The sensors 148, 150, 152 may be positioned anywhere within the conditioned space, the HVAC system 100, and/or the surrounding environment. For example, as shown in the illustrative example of
The HVAC system 100 includes a thermostat 154, for example, located within the conditioned space (e.g. a room or building). The thermostat 154 is generally in signal communication with the controller 160 using any suitable type of wired or wireless connection. The thermostat 154 may be a single-stage thermostat, a multi-stage thermostat, or any suitable type of thermostat. The thermostat 154 is configured to allow a user to input a desired temperature or temperature setpoint 156 of the conditioned space for a designated space or zone such as a room in the conditioned space. The controller 160 may use information from the thermostat 154 such as the temperature setpoint 156 for controlling the compressors 106a,b and/or the blower 144. In some embodiments, the thermostat 154 includes a user interface for displaying information related to the operation and/or status of the HVAC system 100, such as one or more alert signals 158. For example, the user interface may display operational, diagnostic, and/or status messages and provide a visual interface that allows at least one of an installer, a user, a support entity, and a service provider to perform actions with respect to the HVAC system 100.
As described in greater detail below, the controller 160 is configured to perform any of the function described in this disclosure, as described both above and in greater detail below with respect to system 200 of
As described above, in certain embodiments, connections between various components of the HVAC system 100 are wired. For example, conventional cable and contacts may be used to couple the controller 160 to the various components of the HVAC system 100, including, the compressors 106a,b, sensors 114a,b, 118a,b, 132a,b, 136a,b, 137, the expansion valves 122a,b, the blower 144, sensor(s) 148, 150, 152, and thermostat(s) 154. In some embodiments, a wireless connection is employed to provide at least some of the connections between components of the HVAC system 100. In some embodiments, a data bus couples various components of the HVAC system 100 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 100 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 160 to other components of the HVAC system 100.
In an example operation of HVAC system 100, the HVAC system 100 starts up to provide air conditioning to an enclosed space based on temperature setpoint 156. For example, in response to the indoor temperature exceeding the temperature setpoint 156, the controller 160 may cause one or both of the compressors 106a,b and the blower 144 to turn on to startup the HVAC system 100. The HVAC system 100 is generally operated in a normal air conditioning mode (e.g., associated with a CFM/ton value in a range from about 400 to 450 CFM/ton). If a refrigerant leak detected based on the sensor data received from the refrigerant leak detection sensor 137, the controller 160 may evaluate the SC signals 120a,b, SH signals 138a,b, and optionally SST signals 134a,b to determine whether any indication of loss of charge is detected for each compressor 106a,b. In some embodiments, if it is determined that an SC value is less than a threshold SC and an SH value is more than a threshold SH (and optionally SST value is less than a threshold SST), the controller 160 may determine that the respective compressor 106a,b is associated with the loss of charge and the refrigerant leak. In response, the controller 160 may isolate the identified compressor 106a,b and optionally close the shut-off valves outlet and/or inlet to the identified compressor 106a,b. The controller 160 may execute a mitigation plan to turn on the blower 144 and provide air conditioning with one or more other compressors 106 that are not associated with the loss of charge.
In general, the system 200 improves the refrigeration technique by leveraging subcool (SC) values, superheat (SH) values, and (optionally) saturated suction temperature (SST) values to detect loss of charge, and in response, to determine that a set of conditions with respect to the SC, SH, and (optionally) SST values is met, determine a refrigeration circuit 206a,b that is associated with the loss of charge, isolate the refrigeration circuit 206a,b from other components of the HVAC system 100, execute a mitigation plan 262, and upon receiving an air conditioning demand, provide air conditioning by one or more other refrigeration circuits 206a,b that are not associated with loss of charge.
In HVAC systems, particularly in RTU A2L HVAC systems with multiple compressor circuits, when a refrigerant leak is detected, it is not known which compressor circuit is associated with the refrigerant leak since the leak detection sensor is in the space shared by all compressor circuits. As a result, when a refrigerant leak is detected, in one approach, the HVAC system is shut-down and stops air conditioning operations. However, this approach is not efficient. For example, switching off the cooling unit of the HVAC system leads to a temperature rise in a room where the HVAC system is deployed, and therefore, discomfort for the people in the room. In another example, not utilizing other compressor circuits that are not associated with a refrigerant leak reduces the utilization efficiency of those compressor circuits. The refrigerant may be flammable or at least mildly flammable, such as A2L, or toxic.
This disclosure contemplates an unconventional system and method configured to leverage subcool, superheat, and saturated suction temperature values associated with different refrigeration circuits 206a, b to detect which refrigeration circuit 206a,b is associated with the loss of charge and therefore the refrigerant leak. For example, if a refrigerant leak is detected, the system 200 may perform the following operations for each refrigeration circuit 206a,b. For example, for each refrigeration circuit 206a,b, the system 200 may determine whether a subcool value 250a,b, is less than a subcool threshold 252, a superheat value 254a,b is less than a superheat threshold 256, and optionally, if a saturation suction temperature 258a,b is less than an SST threshold 260. If these conditions are met, the system 200 may detect which refrigeration circuit 206a,b is associated with the loss of charge and therefore the refrigerant leak. The system 200 may then isolate the refrigeration circuit 206a,b which is associated with the loss of charge. The system 200 may also execute mitigation plan 262 to run/operate blower 144 to reduce the refrigerant concentration which is due to the refrigerant leak. Upon receiving a air conditioning request, the system 200 may provide air conditioning using one or more other refrigeration circuits 206a,b that are not associated with the loss of charge. The leak detection process and isolating the refrigeration circuit 206106 may not affect the air conditioning operations of the HVAC system 100. Thus, the HVAC system 100 is able to provide seamless air conditioning before, during, and after the detection of the leak. In other words, the HVAC system 100 takes the air conditioning operation load from the compressor 106 that is associated with the leak and puts on (e.g., balances, distributes) the air conditioning operation load onto compressor(s) 106 that are not associated with the refrigerant leak.
Accordingly, the disclosed system 200 provides a practical application of improving the refrigeration techniques by detecting which refrigeration circuit 206a,b is responsible for, associated with, and contributes to the loss of charge and refrigerant leak, isolating the identified refrigeration circuit 206a,b, and use other compressor circuit(s) 106a,b to provide air conditioning. The disclosed system 200 further provides an additional practical application of load balancing among the compressors 106a,b, where the air conditioning operation load is balanced among compressor(s) 106 that are not associated with refrigerant leak and taken from those compressors 106 that are associated with the refrigerant leak. The disclosed system 200 further provides an additional practical application of identifying a location where the refrigerant leak has occurred, and a component associated with the leak.
Sensor 137 may be a sensor circuitry that is configured to detect refrigerant concentration in a volume. For example, sensor 137 may include a circuit board comprising electronic devices and is configured to detect refrigerant particles in the air and monitor the presence of refrigerant particles (e.g., refrigerant gases) in the air. In some examples, each sensor 137 may be a gas sensor configured to detect refrigerant particles in the air. In some examples, sensor 137 may include a sensing element, such as transistors that when exposed to at least a threshold concentration 266 of refrigerant particles in the air (e.g., a number of refrigerant particles per unit space volume) may detect the presence of the refrigerant particles. Sensor 137 may detect the refrigerant leak from the refrigerant particles in the air when the detected concentration of refrigerant is more than the threshold concentration 266 of the refrigerant. For example, the threshold concentration 266 the refrigerant may be 10% of lower flammability limit (LFL), 12% of LFL, 15% of LFL, and the like. The sensor 137 may detect the refrigerant within its detection range. The detection range of the sensor 137 may be five inches, ten inches, twenty inches, and the like.
Certain properties of A2L refrigerants, such as flammability, may be related to how concentrated a given refrigerant is within a volume. To meet compliance standards, the system 200 may be configured to determine when an LFL of a refrigerant exceeds a threshold value within a specified period of time (e.g., within one minute, two minutes, etc.). The system 200 may further be configured to reduce the LFL of the refrigerant if there is a determination that the LFL exceeds the threshold value within a specified period of time.
In one example, the A2L refrigerant may be R454B. In this example, if it is determined that the A2L refrigerant concentration is at least 310 grams per one meter-cube, the LFL of the A2L refrigerant is 100%. Consequently, if a potential ignition source approaches the vicinity of the cubic meter containing the A2L refrigerant, it will give rise to combustion. Thus, it is desired to have the threshold concertation 266 at a much lower % LFL. In certain embodiments, one or more sensors 137 may be positioned at any location within the HVAC system 200. In certain embodiments, the one or more sensors 137 may detect refrigerant leak but because they are positioned in the space shared by multiple refrigeration circuits 206a,b, the data received from the sensors 137 may not indicate which refrigeration circuit 206a,b is associated with the leak.
The controller 240 may correspond to the controller 160 described in
The processor 242 includes one or more processors operably coupled to the memory 246 and I/O interface 244. The processor 242 is 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 memory 246 and controls the operation of refrigeration system 100. The processor 242 may be a programmable logic device, a microcontroller, a microprocessor, or any suitable combination of the preceding. The processor 242 is communicatively coupled to and in signal communication with the memory 246. The one or more processors are configured to process data and may be implemented in hardware or software. For example, the processor 242 may be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. The processor 242 may 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 memory 246 and executes them by directing the coordinated operations of the ALU, registers, and other components. The processor 242 may include other hardware and software that operates to process information, control the refrigeration system 100, and perform any of the functions described herein (e.g., with respect to
The I/O interface 244 is configured to communicate data and signals with other devices. For example, the I/O interface 244 may be configured to communicate electrical signals with components of the refrigeration system 100 including the sensors 118a,b, 132a,b, and 136a,b, among other components. The I/O interface 244 may be configured to communicate with other devices and systems. The I/O interface 244 may provide and/or receive, for example, compressor speed signals, compressor on/off signals, temperature signals, pressure signals, temperature setpoints, environmental conditions, and an operating mode status for the refrigeration system 100 and send electrical signals to the components of the refrigeration system 100 and send alert signal to administrators, technicians, or other users. The I/O interface 244 may include ports or terminals for establishing signal communications between the controller 240 and other devices. The I/O interface 244 may be configured to enable wired and/or wireless communications.
The memory 246 may be a non-transitory computer-readable medium and include 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 memory 246 may be volatile or non-volatile and may include ROM, RAM, ternary content-addressable memory (TCAM), dynamic random-access memory (DRAM), and static random-access memory (SRAM). The memory 246 is operable (e.g., or configured) to store information used by the controller 240 and/or any other logic and/or instructions for performing the function described in this disclosure. For example, the memory 246 may store instructions 248 for performing the functions of the controller 240 described in this disclosure. For example, when the instructions 248 are executed by the processor 242, the instructions 248 cause the processor 242 to perform one or more operations of the controller 240 described herein. The memory 246 may further store threshold concentration 266, subcool signals 150a,b, superheat signals 254a,b, saturation suction temperature 258a,b, sensor data 139, mitigation plan 262, subcool threshold 252, superheat threshold 256, SST threshold 260, switch-on command signal 270, configuration files 162, 164, and any other data/instruction. These components are described further below in conjunction with the operational flow of the system 200.
The operational flow of the system 200 may begin when the controller 240 detects a refrigerant leak. In operation, the controller 240 may receive sensor data 139 from the refrigerant detection sensor circuit 137. The sensor data 139 may include data that indicates refrigerant concentration per volume value detected by the refrigerant detection sensor circuit 137. The refrigerant detection sensor circuit 137 may be positioned at any location within the HVAC system 100, for example, upstream a refrigeration circuit 206a-c, downstream a refrigeration circuit 206a-c, upstream the evaporator 116 (see
The controller 240 may perform the following operations with respect to each refrigeration circuit 206a,b. In other words, the controller 240 may evaluate whether there is a refrigerant leak at each of the refrigeration circuits 206a-c. In this manner, the controller 240 may obtain information about the concentration of the refrigerant in volume. In certain embodiments, the refrigerant detection sensor circuit 137 may be configured to obtain information about the concentration of the refrigerant in volume from sensor data 139, compare the detected concentration of refrigerant with the threshold concentration 266, determine whether the detected concentration of refrigerant exceeds the threshold concentration 266, and communicate a signal indicating the result to the controller 240.
In the example below, the controller 240 evaluates whether there is a refrigerant leak detected by the sensor 137. The controller 240 may compare the detected concentration of refrigerant received from the refrigerant detection sensor circuit 137 with the threshold concentration 266. The controller 240 may determine whether the detected concentration of refrigerant exceeds the threshold concertation 266. If it is determined that the detected concentration of refrigerant exceeds the threshold concentration 266, the controller 240 may determine that a refrigerant leak is detected. The controller 240 may perform the leak detection operation on multiple occasions whenever sensor data 139 is received. For example, the sensor data 139 may be received from the refrigerant detection sensors 137 every minute, every thirty seconds, every ten seconds, and the like. The controller 240 may preform similar operations to evaluate whether there is a refrigerant leak at refrigeration circuit 206b. In response to determining that the there is a refrigerant leak, the controller 240 may fetch the subcool values (indicated by the subcool signals 250a,b), superheat values (indicated by the superheat signals 254a,b), and saturation suction temperature values (indicated by the saturation suction temperature signals 258a,b) for all refrigeration circuits 206a,b. For example, the controller 240 may receive the SH signal 138a from the superheat sensor 136a, SH signal 138b from the superheat sensor 136b, SC signal 120a from subcool sensor 118a, SC signal 120b from subcool sensor 118b, SST signal 134a from SST sensor 132a, and SST signal 134b from SST sensor 132b. In one example, the subcool sensor 118a,b may comprise one or both of one or more temperature sensor circuits and one or more pressure sensor circuits located in or on an outlet line of the condenser 108a,b, respectively. In another example, the superheat sensor 136a,b may comprise one or both of one or more temperature sensor circuits and one or more pressure sensor circuits located in or on an outlet line of the evaporator 124a,b, respectively. The controller 160 may determine and evaluate each of the SC values, SH values, and SST values based on the configuration files 162, 164, similar to that described in
Regarding the subcool value, the controller 240 may compare the first subcool value (associated with the SC signal 120a) with the subcool threshold 252. The subcool threshold 252 may be a range between 0 to 3° F. Regarding the superheat value, the controller 240 may compare the first superheat value (associated with the SH signal 138a) with the superheat threshold 256. The superheat threshold 256 may be a range between 25 to 30° F. In some embodiments, if the controller 240 determines that the first subcool values is less than the subcool threshold 252 and the first superheat value is more than the superheat threshold, the controller 240 may determine that the compressor 106a is associated with the loss of charge. In other words, if these conditions are met, the controller 240 may determine that refrigerant may be leaking from the refrigeration circuit 206a.
In some embodiments, optionally, the controller 240 may use the saturation suction temperature values as an additional factor in evaluating whether there is loss of charge. For example, if the controller 240 determines that the first saturation suction temperature value (associated with the first saturation suction temperature signal 258a) is less than the SST threshold 26 (e.g., of about 35 to 40° F.), in addition to determining that the first subcool values are less than the subcool threshold 252 and the first superheat value is more than the superheat threshold, the controller 240 may determine that the refrigeration circuit 206a is associated with the loss of charge.
In response, the controller 240 may isolate the refrigeration circuit 206a from other components of the HVAC system 100. In this operation, for example, the controller 240 may switch off the compressor(s) 106a included in the refrigeration circuit 206a by sending shut-off command signal 268 to the compressor(s) 106a. In another example, the controller 240 may switch off the refrigeration circuit 206a by sending shut-off command signal 268 to the refrigeration circuit 206a. In another example, the controller 240 may close the shut-off valves outlet and/or inlet to the compressor 106a included in the refrigeration circuit 206a. In another example, the controller 240 may close the shut-off valves in the liquid line near the indoor evaporator coil associated with the evaporator 124a. In another example, the controller 240 may close shut-off valves located upstream of the expansion device near the inlet of the evaporator coil associated with the evaporator 124a. In another example, the controller 240 may close the shut-off valves outlet and/or inlet to the refrigeration circuit 206a. The controller 240 may execute mitigation plan 262 to dilute the leak of the refrigerant associated with and/or from the refrigeration circuit 206a. The mitigation plan 262 may include turning on the blower 114 (e.g., by sending the switch-on command signal 270 to the blower 114). Additionally, the mitigation plan 262 may include switching off the compressor(s) 106a if it is/they are energized, for example, by sending the shut-off command signal 268 to the compressor(s) 106a.
If the controller 240 receives a request to provide air conditioning (e.g., from a user), the controller 240 may turn on the refrigeration circuit 206b, for example, by sending a switch-on command signal 272 to the refrigeration circuit 206b to provide air conditioning in response to an air conditioning demand. If the controller 240 was already providing air conditioning when the refrigerant leak is detected, the controller 240 may continue to provide air conditioning using the refrigeration circuit 206b without the refrigeration circuit 206a. In other words, the controller 240 may continue its operation (e.g., air conditioning and other operations) with non-leaking refrigeration circuits 206. In this manner, the controller 240 is configured to detect the location where the leak has occurred, a component associated with the leak, and address the leak.
In certain embodiments, a processor (e.g., similar to processor 242) may be integrated and embedded within the refrigerant detection sensor 137. In such embodiments, the refrigerant detection sensor 137 may be configured with the threshold concentration 266 and indicate information about whether the refrigerant concentration is more than the threshold concentration 266 in sensor data 139. For example, when a refrigerant concentration more than the threshold concentration 266 is detected by the sensor 137, the refrigerant detection sensor 137 may include a signal (e.g., a flag bit) indicating that an above-threshold concentration is detected to the controller 240 in the sensor data 139, respectively. Otherwise, if the refrigerant detection sensor 137 detects that the refrigerant concentration is less than the threshold concentration 266, the refrigerant detection sensor 137 may include a signal indicating that a less than the threshold concentration 266 of refrigerant is detected to the controller 240 in the sensor data 139, respectively. In response to receiving the sensor data 139 indicating that above the threshold concentration 266 of refrigerant is detected, the controller 240 may execute the mitigation plan 262 and other operations similar to that described above.
At operation 302, the controller 240 determines whether refrigerant leak is detected. For example, the controller 240 may receive sensor data 139 from the refrigerant detection sensor circuit 137 and determine whether the detected refrigerant concentration (indicated in the sensor data 139) is more than the threshold concentration 266. If it is determined that the refrigerant concentration is more than the threshold concentration 266, the controller 240 may determine that there is refrigerant leak within the HVAC system 100. If it is determined that a refrigerant leak is detected, method 300 proceeds to operation 304. Otherwise, method 300 may remain at operation 302 and the controller 240 may continue to monitor the sensor data 139. At operation 304, the controller 240 accesses the SST, SC, and SH values associated with the refrigeration circuits 206a,b. For example, the controller 240 may obtain and determine the SST, SC, and SH values from the SST signals 134a,b, SC signals 120a,b, and SH signals 138a,b, and configuration files 162, 164, respectively, similar to that described in
At operation 308, the controller 240 selects a refrigeration circuit 206a,b. The controller 240 may iteratively select a refrigeration circuit 206a,b until no refrigeration circuit is left for evaluation. For example, assume that the controller 240 selects the refrigeration circuit 206a.
At operation 310, the controller 240 determines whether the SC value (associated with the refrigeration circuit 206a) is less than the SC threshold 252. If it is determined that the SC value is less than the SC threshold 252, the method 300 may proceed to operation 312. Otherwise, the method 300 may return to operation 302. For example, the SC value associated with the SC signal 120a may be evaluated and compared with the SC threshold 252.
At operation 312, the controller 240 determines whether the SH value (associated with the refrigeration circuit 206a) is greater than the SH threshold 256. If it is determined that the SH value is greater than the SH threshold 256, the method 300 may proceed to operation 314. Otherwise, the method 300 may return to operation 302. For example, the SH value associated with the SH signal 138a may be evaluated and compared with the SH threshold 256.
At operation 314, the controller 240 isolates the refrigeration circuit 206a from other components of the HVAC system 100, similar to that described in
At operation 316, the controller 240 determines whether to select another refrigeration circuit 206. If at least one refrigeration circuit 206 is left for evaluation, the controller 240 determines to select another refrigeration circuit 206. If at least one refrigeration circuit 206 is left for evaluation, method 300 may return to operation 308. Otherwise, method 300 may proceed to operation 318.
At operation 318, the controller 240 continues the air conditioning operation with non-leaking refrigeration circuit(s) 206a,b or non-leaking compressor circuits 106a,b, similar to that described in
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 with 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.
