Systems and methods for air temperature control including a2l sensors

Abstract

The present invention provides a system for detecting an amount of A2L refrigerant in an air temperature controller using an A2L refrigerant, and a method of installing a configuration of A2L sensors in the air temperature controller using an A2L refrigerant. The system includes an A2L control board, a first A2L sensor, and a second A2L sensor. The first A2L sensor and the second A2L sensor are coupled in series and electrically coupled to the A2L control board. Each of the first A2L sensor and the second A2L sensor include sensing components configured to detect the amount of A2L refrigerant.

Description

<DP=1>²WO 2022 / 165377 ² PCT / US2022 / 014623² SYSTEMS AND METHODS FOR AIR TEMPERATURE CONTROL INCLUDING A2L²SENSORS²CROSS-REFERENCE TO RELATED APPLICATION²The present application claims benefit of U.S. Application No. 17 / 164,598, ²filed February²1, 2021, which is incorporated herein by reference in its entirety for all ²purposes.²TECHNICAL FIELD²The present invention relates to heating, ventilation, and air-conditioning ²(HVAC) systems,²and more particularly to HVAC systems using an American Society of Heating, ²Refrigeration, and²Air Conditioning Engineers (ASHRAE) Standard 34 classified "A2L" refrigerant.²BACKGROUND²Modern residential and industrial buildings use HVAC systems to keep indoor ²spaces ²climate controlled. In general, HVAC systems circulate air over low-²temperature or high-²temperature sources and distribute the cooled or heated air throughout the ²building to adjust the²indoor ambient air temperature. Modern HVAC systems have used the well-known ²physical ²principle that a fluid transitioning from gas to liquid releases heat, while a ²fluid transitioning from ²liquid to gas absorbs heat, in order to efficiently cool or heat the air ²before distribution. Typical ²HVAC systems circulate a fluid refrigerant through a closed loop of tubing, ²using compressors²and other devices to manipulate the refrigerant and cause it to cycle between ²its liquid and gas²phases. Generally, these phase transitions occur within the HVAC's evaporator ²and condensing ²coils, which are part of the closed loop and designed to transfer heat between ²the circulating ²refrigerant and flowing ambient air.²For a long time, HVAC systems used, and in some places continue to use, a ²chemical called²R-12 or a chemical called R-22 as the refrigerant in the system. While R-12 ²and R-22 are both²classified as "Al- refrigerants under ASHRAE Standard 34, which means they are ²non-flammable ²and have lower toxicity, they both posed great threats to the ozone and ²environment. R-22, while ²an improvement over R-12 in that it had a much lower ozone depletion potential ²(ODP) (0.05 for²1²CA 03206259 2023- 7- 24²<DP=2>²WO 2022 / 165377 ² PCT / US2022 / 014623²R-22 compared to 1.0 for R-12) and global warming potential (GWP) (1,760 for R-²22 compared²to 10,200 for R-12), still had adverse effects on the ozone and environment. ²Thus, in an attempt to ²solve the ozone depletion issue, the industry, with the help of regulations, ²began transitioning to ²the use of R-410A, which is another Al refrigerant but with an ODP of 0. ²However, R-410A has ²a GWP (2,088) that is even higher than that of R-22.²Thus, in an attempt to solve the global warming issue created by the use of ²the above²refrigerants, the industry has begun to move from the use of Al refrigerants ²to those classified as ²A2L refrigerants, which means that the refrigerants are still low toxicity but ²instead of being non-²flammable, they have very low flammability. Generally, these A2L refrigerants ²have much lower ²GWP than the Al refrigerants currently and previously used while still having ²an ODP of 0 like²R-410A. Some examples of viable A2L refrigerants include, but are not limited ²to, R-32 and R-²454b, both of which have an ODP of 0 and a GWP of 675 and 466, respectively. ²However, this ²now means that HVAC systems incorporating these A2L refrigerants need to ²employ safety ²measures to make sure that the refrigerants do not ignite in case there is a ²leak of A2L refrigerant. ²Some of these safety requirements for systems using A2L refrigerants include ²turning on a blower²in the HVAC system while shutting off all other components of the HVAC system ²within the²requisite time after detection of an A2L refrigerant leak as required by A2L ²safety standards. ²Present HVAC systems are not only unable to achieve these requirements within ²the required time, ²but they are unable to detect A2L leaks.²2²CA 03206259 2023- 7- 24²<DP=3>²WO 2022 / 165377 ² PCT / US2022 / 014623² SUMMARY²The present invention is directed to a system for detecting an amount of A2L ²refrigerant in ²an air temperature controller using an A2L refrigerant, and a method of ²installing a configuration ²of A2L sensors in the air temperature controller using the A2L refrigerant. ²The system includes²an A2L control board, a first A2L sensor, and a second A2L sensor. The first ²A2L sensor and²second A2L sensor are coupled in series and electrically coupled to the A2L ²control board. ²Further, each of the first A2L sensor and the second A2L sensor include ²sensing components ²configured to detect the amount of A2L refrigerant. In one or more embodiments ²described herein, ²each of the first A2L sensor and the second A2L sensor include a sensor relay ²electrically disposed²between a bus connector input and a bus connector output. Additionally, in one ²or more²embodiments described herein, each of the first A2L sensor and the second A2L ²sensor run an ²internal self-diagnostic test, and if the sensor passes the internal self-²diagnostic test, the sensor ²closes the sensor relay allowing power to pass through the sensor.²The method of installing the configuration of A2L sensors in an air ²temperature controller²using an A2L refrigerant includes disposing the A2L control board, the first ²A2L sensor, and the²second A2L sensor into the air temperature controller. Further, the first A2L ²sensor is electrically ²coupled to the A2L control board and the second A2L sensor is coupled to the ²A2L control board. ²Additionally, the first A2L sensor and the second A2L sensor are coupled in ²series to the A2L ²control board. In one or more embodiments described herein, each of the first ²A2L sensor and the²second A2L sensor run an internal self-diagnostic test, and if the sensor ²passes the internal self-²diagnostic test, the sensor closes its sensor relay allowing power to pass ²through the sensor. ²The HVAC systems as disclosed herein provide components and architecture that ²allow for ²detection of leaks of A2L refrigerant and for meeting the safety requirements ²within the required ²time. Additionally, within the HVAC systems, the components and architecture ²of the systems for²detecting the amount of A2L refrigerant as disclosed herein ensure that the ²system meets the safety²requirements by ensuring that all A2L sensors are operating properly while an ²HVAC system is²3²CA 03206259 2023- 7- 24²<DP=4>²WO 2022 / 165377 ² PCT / US2022 / 014623²running. Thus, a system for detecting the amount of A2L refrigerant may be ²installed such that²HVAC systems incorporating A2L refrigerants operate safely while reducing the ²negative ²environmental impact caused by present HVAC systems. The foregoing and other ²objects, ²features, and advantages of the invention will be apparent from the following ²more particular ²description of the invention, as illustrated in the accompanying drawings, ²wherein like reference² numbers represent like parts of the invention.²4²CA 03206259 2023- 7- 24²<DP=5>²WO 2022 / 165377 ² PCT / US2022 / 014623² BRIEF DESCRIPTION OF THE DRAWINGS²A more complete understanding of the present embodiments and advantages ²thereof may be ²acquired by referring to the following description taken in conjunction with ²the accompanying ²drawings. in which like reference numbers indicate like features, and wherein:²FIG. 1 shows a non-communicating HVAC system using an A2L refrigerant, ²according to²one or more embodiments;²FIG. 2 is a flow chart illustrating an embodiment of a method of operating a ²non-²communicating HVAC system using an A2L refrigerant, according to one or more ²embodiments;²FIG. 3 shows a communicating HVAC system using an A2L refrigerant, according ²to one ²or more embodiments;²FIG. 4 is a flow chart illustrating an embodiment of a method of operating a ²communicating²HVAC system using an A2L refrigerant, according to one or more embodiments;²FIG. 5 shows another non-communicating HVAC system using an A2L refrigerant,²according to a second embodiment;²FIG. 6 is a flow chart illustrating another embodiment of a method of ²operating a non-²communicating HVAC system using an A2L refrigerant, according to one or more ²embodiments;²FIG. 7 shows another communicating HVAC system using an A2L refrigerant, ²according to ²one or more embodiments;²FIG. 8 is a flow chart illustrating another embodiment of a method of ²operating a non-²communicating HVAC system using an A2L refrigerant, according to one or more ²embodiments;²FIG. 9 is an illustrative configuration of A2L sensors for use in an HVAC ²system using an²A2L refrigerant, according to one or more embodiments; and²FIG. 10 is a flow chart illustrating an embodiment of a method of installing ²and testing a ²configuration of A2L sensors for use in an illustrative configuration of A2L ²sensors for use in an²HVAC system using an A2L refrigerant, according to one or more embodiments.² 5²CA 03206259 2023- 7- 24²<DP=6>²WO 2022 / 165377 ² PCT / US2022 / 014623² DESCRIPTION²This disclosure generally relates to non-communicating and communicating HVAC ²systems ²designed to incorporate the use of an A2L refrigerant and meet the safety ²standards imposed on ²systems using A2L refrigerants.²FIG. 1 shows a non-communicating HVAC system using an A2L refrigerant, ²according to²one or more embodiments. In one or more embodiments, an HVAC system 100 may be ²used to²distribute cooled or heated air throughout a building 110 to adjust the ²ambient air temperature ²inside 111 of the building 110. The HVAC system may include an indoor unit ²120, an outdoor unit ²130, a thermostat 140, an A2L control board 150, and an A2L sensor 170. ²Generally, in one or ²more embodiments, the indoor unit 120 may be fluidly coupled to the outdoor ²unit 130 such that²an A2L refrigerant may flow between the indoor unit 120 and the outdoor unit ²130 to cool or heat²air within the indoor unit 120. Further, in one or more embodiments, both the ²indoor unit 120 and ²the outdoor unit 130 may be electrically coupled to the thermostat 140. The ²thermostat 140 may ²be configured to use on / off-type signals for communication and control of the ²indoor unit 120 and ²the outdoor unit 130. Furthermore, in one or more embodiments, the A2L control ²board 150 may²be directly electrically coupled to the indoor unit 120 and the A2L sensor ²170. The A2L control²board 150 may act as a passthrough for power to portions of the indoor unit ²120, the outdoor unit ²130, and the thermostat 140 and may be configured to block power from getting ²to certain parts of ²the indoor unit 120, the outdoor unit 130, and the thermostat 140 if there is ²an A2L refrigerant leak ²in the system. Additionally, an A2L sensor 170 may be physically disposed ²within the indoor unit²120 and electrically coupled to the A2L control board 150. The A2L sensor 170 ²may be configured²to send signals to the A2L control board 150 when an A2L refrigerant leak is ²detected.²In one or more embodiments, indoor unit 120 may be disposed on the inside 111 ²of the ²building 110. The indoor unit 120 may be configured to distribute cooled or ²heated air to rooms ²on the inside 111 of the building 110. The indoor unit 120 may be any type of ²HVAC system that²includes a blower 121 and a heat exchanger 127 having an indoor evaporator ²coil 124. Thus, in²6²CA 03206259 2023- 7- 24²<DP=7>²WO 2022 / 165377 ² PCT / US2022 / 014623²one or more embodiments, the indoor unit 120 may be either a furnace or an air ²handler, as both²types of system include, at least, a blower and an indoor evaporator coil. ²Additionally, the indoor ²evaporator coil 124 may be disposed adjacent to the blower 121, such that when ²the blower 121 ²blows air within the indoor unit 120, the air is blown through the evaporator ²coil 124.²Further, in one or more embodiments, the blower 121 may include a blower fan ²122 and a²blower motor 123. By way of example, in one or more embodiments, the blower ²motor 123 may²be constant torque motor, while in other embodiments, the blower motor 123 may ²be a permanent ²split capacitor (PSC) motor. The blower motor 123 may be mechanically coupled ²to the blower ²fan 122 such that when the blower motor 123 is turned on, the blower fan 122 ²is configured to spin ²and cause a movement of air out from the blower 121 and through the indoor ²evaporator coil 124.²The indoor evaporator coil 124 may be configured to receive the A2L ²refrigerant on the inside of²the coil while air from the blower 121 is blown across the outside of the ²coil, which allows for ²heat to exchange either from the A2L refrigerant to the air or vice versa. The ²A2L refrigerant, after ²cooling or heating the air, may be cycled back to the outdoor unit 130, where ²it will go through ²the reverse heat exchange process before returning to the indoor evaporator ²coil 124. Additionally,²indoor unit 120 is configured to distribute the air that is blown from the ²blower 121 and across the²indoor evaporator coil 124 to the rooms on the inside 1 1 1 of the building ²110 by way of the force ²of the blower 121.²The indoor unit 120 may also include a transformer 125 and an indoor control ²board 126. ²The transformer 125 may be directly electrically coupled to and configured to ²provide 24 volts²A / C power to the A2L control board 150. Further, the indoor control board 126 ²may be electrically²coupled to the A2L control board 150 such that the indoor control board 126 ²may receive 24 volts ²A / C power indirectly from the transformer 125. Additionally, the indoor ²control board 126 may ²be electrically coupled to, at least, the blower motor 123 and the thermostat ²140. In one or more ²embodiments, the transformer 125 may be configured to indirectly provide a 24 ²volt A / C power²to both the blower motor 123 and the thermostat 140 by way of indoor control ²board 126 and the²7²CA 03206259 2023- 7- 24²<DP=8>²WO 2022 / 165377 ² PCT / US2022 / 014623²A2L control board 150. In one or more embodiments, the blower motor has its ²own source of²power. So, while the 24 volt A / C power that the blower motor receives does not ²power on the ²blower motor 123, the 24 volt A / C signal is needed to turn the blower motor ²123 on. By way of ²example only, in one or more embodiments, the indoor control board 126 may be ²configured to ²provide power to the thermostat 140, the thermostat 140 may be configured to ²send a signal to the²indoor control board 126 to turn on the blower motor 123, and the indoor ²control board 126 may²be configured to provide power to the blower motor 123 to turn it on.²Further, the outdoor unit 130 may be disposed on an outside 112 of the ²building 110 and be ²configured to use the outdoor environment to reheat or cool down the A2L ²refrigerant after it has ²been run through the indoor evaporator coil 124. The outdoor unit 130 may ²include, but is not²limited to, either a heat pump or an air conditioner. Whether the outdoor unit ²130 is a heat pump²or an air conditioner, the outdoor unit 130 may include a compressor (not ²shown), an outdoor coil ²(not shown), and an outdoor control board 131. The outdoor unit 130 may be ²configured to receive ²power through the outdoor control board 131, which itself is configured to ²receive power from the ²transformer 125 by way of the thermostat 140, the indoor control board 126, ²and the A2L control²board 150. By way of example only, in one or more embodiments, the outdoor ²control board 131²may be configured to receive power and control signals from the thermostat ²140, such that outdoor ²control board 131 may start the condenser after receiving a signal from the ²thermostat 140 to do ²so.²Still referring to FIG. 1, in one or more embodiments. the A2L sensor 170 may ²be configured²to detect an A2L refrigerant leak and send a signal reporting as much. In one ²or more embodiments,²the A2L sensor 170 may be configured to detect an A2L refrigerant leak by one ²of a number of ²methods, including, at least, by detecting an amount or a concentration of A2L ²refrigerant in the ²air that exceeds a leak threshold. The A2L sensor 170 may be electrically ²coupled to and ²communicate with the A2L control board 150. In one or more embodiments, the ²A2L sensor 170²may be electrically coupled to the A2L control board 150 by way of a first ²sensor connector 157.²8²CA 03206259 2023- 7- 24²<DP=9>²WO 2022 / 165377 ² PCT / US2022 / 014623²The A2L sensor 170 may be configured to communicate to the A2L control board ²150 that the²A2L sensor 170 is connected to the system and working properly. Additionally, ²when the A2L ²sensor 170 detects an A2L refrigerant leak, it may communicate the A2L ²refrigerant leak to the ²A2L control board 150, which may be configured to receive the signal and ²perform the safety ²measures required by A2L safety standards. In one or more embodiments, the A2L ²sensor 170 and²the A2L control board 150 may be electrically coupled by way of an RS-485 bus; ²however, one of²ordinary skill in the art would understand that any type of electrical ²connection that allows the ²A2L sensor 170 to send a signal to the A2L control board 150 may be used.²While the A2L sensor 170 is depicted as being electrically and communicatively ²coupled to ²the A2L control board 150 by way of a wired connection, one of ordinary skill ²in the art would²understand that the A2L sensor 170 may just be communicatively coupled to the ²A2L control²board 150 wirelessly. In one or more embodiments, the A2L sensor 170 may be ²communicatively ²coupled to the A2L control board 150 by any wireless means, such as Wi-Fi or ²Bluctooth. ²Further, in one or more embodiments, the A2L sensor 170 may be disposed within ²the indoor ²unit 120 so that it may detect an A2L refrigerant leak that occurs within the ²indoor evaporator coil²124 of the HVAC system 100. As depicted, in one or more embodiments, the A2L ²sensor 170 may²be disposed directly against the indoor evaporator coil to minimize the time ²it takes for the A2L ²sensor 170 to detect an A2L refrigerant leak. Further, while the A2L sensor ²170 is depicted within ²the indoor unit 120, one or ordinary skill in the art would understand that ²the A2L sensor 170 may ²instead be disposed within the outdoor unit 130. Further, while a single ²sensor is depicted, one of²ordinary skill in the art would understand that multiple sensors may be ²incorporated into the HVAC²system to ensure that an A2L refrigerant leak is detected and the required ²safety measures are ²taken within the time required by A2L safety standards. For example, one of ²ordinary skill in the ²art would understand that the HVAC system may include two A2L sensors, with ²both A2L sensors ²disposed within the indoor unit, both A2L sensors disposed within the outdoor ²unit, or one A2L²sensor disposed within each of the indoor unit and the outdoor unit. Thus, one ²of ordinary skill in²9²CA 03206259 2023- 7- 24²<DP=10>²WO 2022 / 165377 ² PCT / US2022 / 014623²the art would understand that in one or more embodiments, a plurality of A2L ²sensors may be²disposed within the HVAC system with one or more A2L sensors disposed within ²the indoor unit ²and / or one or more A2L sensors disposed within the outdoor unit as may be ²determined necessary ²to ensure that an A2L refrigerant leak is detected and the required safety ²measures are taken within ²the time required by A2L safety standards.²Additionally, referring to FIG. 1, in one or more embodiments, the A2L control ²board 150²may be disposed inside of the indoor unit 120. However, one of ordinary skill ²in the art would ²understand that, in one or more embodiments, the A2L control board 150 may be ²disposed outside ²of the indoor unit 120 and either connected to the indoor unit 120 or adjacent ²to the indoor unit ²120. Further, in addition to being electrically coupled to the transformer ²125, the indoor control²board 126, and the A2L sensor 170, as discussed above, the A2L control board ²150 may be ²electrically coupled to the blower motor 123. In one or more embodiments, the ²A2L control board ²150 may be configured to signal the blower motor 123 to run either by way of a ²24 volt A / C line ²connected to an input lead 128 on the blower motor 123, if the blower motor ²123 is a constant ²torque motor, or by way of a line voltage provided to the input lead 128 of ²the blower motor 123,² if the blower motor 123 is a PSC motor.²In one or more embodiments, the A2L control board 150 may include a power ²supply 151, ²a power-in contact point 152, a first relay 153, a first power-out contact ²point 154, a second relay ²155, a second power-out contact point 156, a first sensor connector 157, a ²second sensor connector ²158, a buzzer 159. a light emitting diode (LED) 160, a dry contact relay 161, ²first and second²ventilator contact points 162a and 162b, and a fuse 163. The power supply 151 ²may be coupled to²circuitry on the A2L control board 150 such that the A2L control board may ²open and close, at ²least, the first relay 153, the second relay 154, and the dry contact relay ²161. Further, in one or ²more embodiments, the first relay 153 may be electrically disposed between the ²power-in contact ²point 152 and the first power-out contact point 154, such that when the first ²relay 153 is open,²power from the power-in contact point 152 does not reach the first power-out ²contact point 154.² CA 03206259 2023- 7- 24²<DP=11>²WO 2022 / 165377 ² PCT / US2022 / 014623²Furthermore, the fuse 163 may be electrically disposed between the power-in ²contact point 152²and the first relay 153. Similarly, in one or more embodiments, the second ²relay 155 may be ²electrically disposed between the power-in contact point 152 and the second ²power-out contact ²point 156, such that when the second relay 155 is open, power from the power-²in contact point ²152 does not reach the second power-out contact point 156. Additionally, the ²fuse 163 may be²electrically disposed between the power-in contact point 152 and the second ²relay 155. By way of²example, in one or more embodiments, when the first relay 153 is open, the ²second relay 155 is ²closed, and when the second relay 155 is open, the first relay 153 is closed. ²Further, in one or more ²embodiments, in the default state, the first relay 153 is open and the second ²relay 155 is closed.²In one or more embodiments, the transformer 125 may be electrically coupled to ²the power-²in contact point 152, the first power-out contact point 154 may be ²electrically coupled to the indoor²control board 126, and the second power-out contact point 156 may be ²electrically coupled to the ²blower motor 123. FIG. 1 displays a default state of the A2L control board ²150, where the 24 volt ²A / C power coming from the transformer 125 is routed to the blower motor 123, ²causing it to run. ²Further, in one or more embodiments, if the A2L control board 150 fails, the ²relays all revert to²their default state, and thus, if the A2L control board 150 fails, power will ²be directed to the blower²motor 123. Furthermore, in one or more embodiments, when the A2L control board ²150 is turned ²on, the second relay 154 immediately opens so that the blower motor 123 is not ²unnecessarily run. ²Additionally, after the A2L control board 150 is turned on, when the system is ²ready to run, the ²first relay 152 is closed, turning on the HVAC system 100.²Further, in one or more embodiments, the power supply 151 may be coupled to ²the first²sensor connector 157 and the second sensor connector 158, separately. Thus, in ²one or more ²embodiments, the A2L control board 150 may separately test one or more A2L ²sensors 170 before ²closing the first relay 153 and powering up the HVAC system 100. This allows ²for the A2L control ²board 150 to make sure that the sensors 170 are working properly and there are ²no A2L refrigerant²leaks before beginning the system. While two separate sensor connectors are ²depicted, one of²11²CA 03206259 2023- 7- 24²<DP=12>²WO 2022 / 165377 ² PCT / US2022 / 014623²ordinary skill in the art would understand that the A2L control board may ²instead include a sensor²signal-in contact and a sensor signal-out contact and the one or more sensors ²may be run in series ²instead of in parallel.²Thus, when the A2L control board 150 receives a signal from the A2L sensor 170 ²that there ²is an A2L refrigerant leak, the A2L control board 150 may be configured to ²carry out the required²safety measures required by A2L safety standards. More specifically, in one or ²more embodiments,²if a leak is detected, the A2L control board 150 may be configured to cut off ²power to the indoor ²control board 126 by opening the first relay 153, while directing power ²directly to the blower ²motor 123 by closing the second relay 155. Since the indoor unit 120, the ²thermostat 140, and the ²outdoor unit 130 receive power from the indoor control board 126, when the A2L ²sensor detects²an A2L refrigerant leak and the A2L control board 150 cuts power to the indoor ²control board 126,²the entire HVAC system 100, besides the blower motor 123, is configured to ²lose power and shut ²off. This allows the HVAC system 100 to meet the A2L safety requirements ²within the requisite ²time after detection of an A2L refrigerant leak.²Additionally, as discussed above, in one or more embodiments, the A2L control ²board 150²may include a buzzer 159, an LED 160, a dry contact relay 161, and first and ²second ventilator²contact points 162a and 162b. In one or more embodiments, the dry contact ²relay 161 may be ²electrically coupled to a ventilator (not shown), such that when the A2L ²control board 150 receives ²an A2L refrigerant leak signal from the A2L sensor 170, the dry contact relay ²161 will flip and ²turn on the ventilator. Furthermore, in one or more embodiments, when the A2L ²control board²receives an A2L refrigerant leak signal from the A2L sensor, the LED 160 and ²the buzzer 159 will²receive power. When receiving power, the LED 160 will display an error code ²and the buzzer 159 ²will make sound in order to give visual and auditory alarms that the HVAC ²system 100 is ²experiencing an A2L refrigerant leak.²Referring now to FIG. 2, a flow chart of an embodiment of a method 200 of ²installing and²operating a non-communicating HVAC system using an A2L refrigerant as ²described above with²12²CA 03206259 2023- 7- 24²<DP=13>²WO 2022 / 165377 ² PCT / US2022 / 014623²respect to FIG. 1, according to one or more embodiments, is illustrated. ²Beginning with an HVAC²system 100 in which the indoor unit 120 has been disposed on an inside 111 of ²a building 110, the ²outdoor unit 130 has been disposed on an outside 112 of the building 110, the ²indoor control board ²126 has been electrically coupled to the thermostat 140 and a blower motor 123 ²of the blower 121, ²and the outdoor control board 131 has been electrically coupled to the ²thermostat 140, the method²200 may include one or more of the following: (step 210) installing the A2L ²control board 150²and the A2L sensor 170 into the HVAC system 100, (step 220) testing the A2L ²sensor 170, (step ²230) beginning operation of the HVAC system 100, (step 240) checking for A2L ²refrigerant leaks, ²and (step 250) performing safety measures upon detecting an A2L refrigerant ²leak.²At step 210, an A2L control board 150 and an A2L sensor 170 may be installed ²into the²HVAC system 100. Installation ofthe A2L control board 150 and the A2L sensor ²170 may include,²at least, (step 211) physically coupling the A2L sensor 170 to the indoor ²evaporator coil 124 of ²the indoor unit 120, (step 212) electrically coupling the A2L sensor 170 to ²the A2L control board ²150, (step 213) electrically coupling the A2L control board 150 to the indoor ²control board 126, ²(step 214) electrically coupling the A2L control board 150 to the blower motor ²123, (step 215)²electrically coupling the A2L control board 150 to the transformer 125, and ²(step 216) turning on²the A2L control board 150 and opening the second relay 155.²In one or more embodiments, at step 211, the A2L sensor 170 may be disposed ²within the ²indoor unit 120 such that it is adjacent or connected to the indoor evaporator ²coil 124 such that the ²A2L sensor 170 is able to detect an A2L refrigerant leak if one occurs. ²Further, at step 212, the²A2L sensor 170 may be electrically coupled to the A2L control board 150 such ²that the A2L sensor²170 and the A2L control board 150 have two-way communication between them. By ²way of ²example, in one or more embodiments, an A2L sensor 170 may be electrically ²coupled to a first ²sensor connector 157 of the A2L control board 150 by way of an RS-485 bus. One ²of ordinary ²skill in the art would appreciate that in other embodiments, any other ²electric coupling that allows²13²CA 03206259 2023- 7- 24²<DP=14>²WO 2022 / 165377 ² PCT / US2022 / 014623²for two-way communication between the A2L sensor 170 and the A2L control board ²150 may be²used.²At step 213, the A2L control board 150 may be electrically coupled to the ²indoor control ²board 126. In one or more embodiments, a wire capable of carrying 24 volt A / C ²power may be ²electrically coupled on one end to a power-in terminal within the indoor ²control board 126 and on²the other end to a first power-out contact 154 of the A2L control board 150. ²Thus, once a²transformer 125 is electrically coupled to the A2L control board 150, ²providing a 24 volt A / C ²power to the A2L control board 150, and a first relay 153 is closed, the ²indoor control board 126 ²may receive the 24 volt A / C power.²At step 214, the A2L control board 150 may be electrically coupled to the ²blower motor 123.²In one or more embodiments, a wire capable of carrying 24 volt A / C power may ²be electrically²coupled on one end to an input lead 128 on the blower motor 123 and on the ²other end to a second ²power-out contact 156 of the A2L control board 150. Thus, once a transformer ²125 is electrically ²coupled to the A2L control board 150 providing a 24 volt A / C power to the A2L ²control board ²150, the blower motor 123 may receive the 24 volt A / C power whenever the ²second relay 155 is²closed. In one or more embodiments, the default for the second relay 155 may ²be that it is closed;²however, while the HVAC system is running and no A2L leak is detected, the ²second relay 155 is ²kept open. Further, in the event that an A2L refrigerant leak is detected, the ²second relay 155 is ²closed such that the blower motor 123 may receive the 24 volt A / C power even ²though the rest of ²the }-VAC system is shut down.²At step 215, the A2L control board 150 may be electrically coupled to the ²transformer 125.²In one or more embodiments, a wire capable of carrying 24 volt A / C power may ²be electrically ²coupled on one end to a power-out terminal within the transformer 125 and on ²the other end to a ²power-in contact 152 of the A2L control board 150. Thus, once the transformer ²125 is electrically ²coupled to the A2L control board 150, the A2L control board has a 24 volt A / C ²power that it may² distribute to either the indoor control board 126 or the blower motor 123.²14²CA 03206259 2023- 7- 24²<DP=15>²WO 2022 / 165377 ² PCT / US2022 / 014623²At step 216, the A2L control board 150 may be turned on and the second relay ²155 may be²opened. In one or more embodiments, when the A2L control board 150 is turned ²on, the relays are ²in the default state, which includes the second relay 155 being closed. Thus, ²in order to make sure ²power is not unnecessarily diverted to the blower motor 123, in one or more ²embodiments, when ²the A2L control board 150 powers up, the A2L control board 150 opens the ²second relay 155.²At step 220, the A2L sensor 170 may be tested to confirm that it is properly ²operational.²Once electrically coupled to the A2L control board 150, in one or more ²embodiments, the A2L ²sensor 170 may perform an internal diagnostic check to make sure that the ²sensor is operating ²properly and may detect an A2L refrigerant leak. If the diagnostic check is ²successful, the A2L ²sensor 170 may communicate the successful diagnostic check to the A2L control ²board 150, which²can begin operation of the HVAC system 100. If the A2L sensor 170 fails the ²diagnostic check,²the A2L sensor 170 will communicate the failed diagnostic check to the A2L ²control board 150, ²which will remain in the default configuration, keeping the HVAC system 100 ²from operating ²until the A2L sensor is repaired or replaced.²At step 230, the A2L control board 150 may begin operation of the HVAC system ²100. In²order to begin operation, in one or more embodiments, the A2L control board ²150 may close the²first relay 153 of the A2L control board 150. Closing the first relay 153 ²allows for the 24 volt A / C ²power that the A2L control board 150 receives from the transformer 125 to pass ²to the indoor ²control board 126 and power up the rest of the HVAC system 100.²At step 240, while the HVAC system is running, in one or more embodiments, the ²A2L²sensor 170 may check for A2L refrigerant leaks. The A2L sensor 170 may ²continuously check for²A2L refrigerant leaks while the FIVAC system 100 is running, such that if a ²check comes back ²negative for an A2L refrigerant leak, the A2L sensor 170 repeats step 240. ²However, if the AL2 ²sensor 170 detects an A2L leak, then the A2L sensor 170 communicates the A2L ²refrigerant leak ²to the A2L control board and the HVAC system continues to step 250.² CA 03206259 2023- 7- 24²<DP=16>²WO 2022 / 165377 ² PCT / US2022 / 014623²At step 250, the HVAC system 100, by way of the A2L control board 150, may ²perform²safety measures to eliminate the threat of the detected A2L refrigerant leak. ²Specifically, the ²HVAC system 100 may (step 252) open the first relay 153, (step 253) close the ²second relay 155, ²(step 254) close the dry contact relay 161, (step 256) power on the LED 160, ²and (step 258) power ²on the buzzer 159. At step 252, opening the first relay 153 prevents the 24 ²volt A / C power that the²A2L control board 150 receives from the transformer 125 from passing to the ²indoor control board²126. Removing the 24 volt A / C power from the indoor control board 126 in turn ²removes power ²from the entire HVAC system 100 since the blower motor 123, thermostat 140, ²and outdoor unit ²130 are all configured to receive 24 volt A / C power, either directly or ²indirectly, from the indoor ²control board 126. Additionally, at step 253, closing the second relay 155 ²causes the 24 volt A / C²power that the A2L control board 150 receives from the transformer 125 to pass ²to the blower²motor 123 directly. The 24 volt A / C power run directly to the blower motor 123 ²causes the blower ²motor 123 to run even though the indoor control board 126 and the thermostat ²140 have no power ²and are turned off. Further, while listed as separate steps, one of ordinary ²skill would appreciate ²that in one or more embodiments, either step 252 or step 253 may take place ²before the other, or²in other embodiments, step 252 and step 253 may occur simultaneously. ²Additionally, one of²ordinary skill in the art would appreciate that both steps 252 and 253 may be ²completed within the ²requisite time after detection of an A2L refrigerant leak as required by A2L ²safety standards. ²At step 254, in one or more embodiments, the A2L control board 150 may close ²the dry ²contact relay 161 that turns on a ventilator. In one or more embodiments, a ²ventilator may be²connected to the HVAC system 100 by way of first and second ventilator contact ²points 162a and²162b on the A2L control board 150. Thus, when the A2L sensor 170 detects a ²leak, the A2L control ²board 150 may close the dry contact relay 161, which allows power to run ²directly to the ventilator ²and turns on the ventilator. Further, at step 256, when the A2L control board ²150 receives the A2L ²refrigerant leak communication, the A2L control board 150 may provide power to ²the LED 160.²16²CA 03206259 2023- 7- 24²<DP=17>²WO 2022 / 165377 ² PCT / US2022 / 014623²Furthermore, at step 258, when the A2L control board 150 receives the A2L ²refrigerant leak²communication, the A2L control board 150 may provide power to the buzzer 159.²Thus, in one or more embodiments, in response to a communication from the A2L ²sensor ²170 that an A2L refrigerant leak has been detected, the A2L control board 150 ²may turn off the ²entirety of the HVAC system 100, except the blower motor 123, which is powered ²on, turn on a²ventilator if the HVAC system 100 has one, and turn on visual and auditory ²alarms that an A2L²refrigerant leak has been detected.²While the method 200 is described with respect to an HVAC system 100 including ²a single ²A2L sensor 170, one of ordinary skill in the art, would understand that any ²number of sensors may ²be used in the system and the method may include electrically coupling the ²further sensors to the²control board, testing the further sensors, and communicating with the further ²sensors as the further²sensors check for A2L refrigerant leaks.²FIG. 3 shows a communicating HVAC system using an A2L refrigerant, according ²to a one ²or more embodiments. In one or more embodiments, an I-IVAC system 300 may be ²used to ²distribute cooled or heated air throughout a building 310 to adjust the ²ambient air temperature²inside 311 of the building 310. The HVAC system may include an indoor unit ²320, an outdoor unit²330, a thermostat 340, an A2L control board 350, an A2L sensor 370, an outdoor ²relay 380, and a ²high pressure switch 390.²Generally, in one or more embodiments, the indoor unit 320 may be fluidly ²coupled to the ²outdoor unit 330 such that an A2L refrigerant may flow between the indoor unit ²320 and the²outdoor unit 330 to cool or heat air within the indoor unit 320. Further, in ²one or more²embodiments, both the indoor unit 320 and the outdoor unit 330 may be ²communicatively coupled ²to each other by way of an RS-485 system communication. The thermostat 340 may ²be either a ²non-communicating or communicating thermostat and may be electrically coupled ²to the indoor ²unit 320 either by a 24 volt A / C connection or an R-485 system communication. ²Furthermore, in²one or more embodiments, the A2L control board 350 may be directly ²electrically coupled to the²17²CA 03206259 2023- 7- 24²<DP=18>²WO 2022 / 165377 ² PCT / US2022 / 014623²indoor unit 320 and indirectly electrically coupled to the outdoor unit 330 by ²way of the outdoor²relay 380 and the high pressure switch 390. The A2L control board 350 may act ²as a passthrough ²for power to the indoor unit 320 and may be configured to block power from ²getting to certain ²parts of the indoor unit 320 if there is an A2L refrigerant leak in the ²system. Additionally, the A2L ²control board 350 may be configured to turn off the outdoor unit by way of ²electrical connections²between the A2L control board 350, the outdoor relay 380, the high pressure ²switch 390, and the²outdoor unit 320. Further, the A2L sensor 370 may be physically disposed ²within the indoor unit ²320 and electrically coupled to the A2L control board 350. The A2L sensor 370 ²may be configured ²to send signals to the A2L control board 350 when an A2L refrigerant leak is ²detected.²In one or more embodiments, indoor unit 320 may be disposed on the inside 311 ²of the²building 310. The indoor unit 320 may be configured to distribute cooled or ²heated air to rooms²on the inside 311 of the building 310. The indoor unit 320 may be any type of ²HVAC system that ²includes a blower 321 and a heat exchanger 327 having an indoor evaporator ²coil 324. Thus, in ²one or more embodiments, the indoor unit 320 may be either a furnace or an air ²handler, as both ²types of system include, at least, a blower and an indoor evaporator coil. ²Additionally, the indoor²evaporator coil 324 may be disposed adjacent to the blower 321, such that when ²the blower 321²blows air within the indoor unit 320, the air is blown through the evaporator ²coil 324.²Further, in one or more embodiments, the blower 321 may include a blower fan ²322 and a ²blower motor 323. By way of example, in one or more embodiments, the blower ²motor 323 may ²be constant torque motor, while in other embodiments, the blower motor 323 may ²be a permanent²split capacitor (PSC) motor. The blower motor 323 may be mechanically coupled ²to the blower²fan 322 such that when the blower motor 323 is turned on, the blower fan 322 ²is configured to spin ²and cause a movement of air out from the blower 321 and through the indoor ²evaporator coil 324. ²The indoor evaporator coil 324 may be configured to receive the A2L ²refrigerant on the inside of ²the coil while air from the blower 321 is blown across the outside of the ²coil, which allows for²heat to exchange either from the A2L refrigerant to the air or vice versa. The ²A2L refrigerant, after²18²CA 03206259 2023- 7- 24²<DP=19>²WO 2022 / 165377 ² PCT / US2022 / 014623²cooling or heating the air, may be cycled back to the outdoor unit 330, where ²it will go through²the reverse heat exchange process before returning to the indoor evaporator ²coil 324. Additionally, ²indoor unit 320 is configured to distribute the air that is blown from the ²blower 321 and across the ²indoor evaporator coil 324 to the rooms on the inside 311 of the building 310 ²by way of the force ²of the blower 321.²The indoor unit 320 may also include a transformer 325 and an indoor control ²board 326.²The transformer 325 may be directly electrically coupled to and configured to ²provide 24 volts ²A / C power to the A2L control board 350. Further, the indoor control board 326 ²may be electrically ²coupled to the A2L control board 350 such that the indoor control board 326 ²may receive 24 volts ²A / C power indirectly from the transformer 325. Additionally, the indoor ²control board 326 may²be electrically coupled to, at least, the blower motor 323 and the thermostat ²340. In one or more²embodiments, the transformer 325 may be configured to indirectly provide a 24 ²volt A / C power ²to the blower motor 323 by way of the, indoor control board 326 and the A2L ²control board 350. ²In one or more embodiments, the blower motor has its own source of power. So, ²while the 24 volt ²A / C power that the blower motor receives does not power on the blower motor ²323, the 24 volt²A / C signal is needed to turn the blower motor 323 on. Further, the indoor ²control board 326 may²be electrically coupled to the thermostat by either a 24 volt A / C power ²connection or by an R-485 ²system communication depending on whether the thermostat is a non-²communicating or ²communicating thermostat, respectively.²Further, the outdoor unit 330 may be disposed on an outside 312 of the ²building 310 and be²configured to use the outdoor environment to reheat or cool down the A2L ²refrigerant after it has²been run through the indoor evaporator coil 324. The outdoor unit 330 may ²include, but is not ²limited to, either a heat pump or an air conditioner. Whether the outdoor unit ²330 is a heat pump ²or an air conditioner, the outdoor unit 330 may include a compressor (not ²shown), an outdoor coil ²(not shown), and an outdoor control board 331. The outdoor unit 330 may be ²configured to²communicate with the indoor unit 320 through RS-485 system communication ²between the indoor²19²CA 03206259 2023- 7- 24²<DP=20>²WO 2022 / 165377 ² PCT / US2022 / 014623²control board 326 and the outdoor control board 331. Further, the outdoor ²control board 331 may²be electrically coupled to the A2L control board 350 as discussed below.²Still referring to FIG. 3, in one or more embodiments, the A2L sensor 370 may ²be configured ²to detect an A2L refrigerant leak and send a signal reporting as much. In one ²or more embodiments, ²the A2L sensor 370 may be configured to detect an A2L refrigerant leak by one ²of a number of²methods, including, at least, by detecting an amount or a concentration of A2L ²refrigerant in the²air that exceeds a leak threshold. The A2L sensor 370 may be electrically ²coupled to and ²communicate with the A2L control board 350. In one or more embodiments, the ²A2L sensor 370 ²may be electrically coupled to the A2L control board 350 by way of a first ²sensor connector 357. ²The A2L sensor 370 may be configured to communicate to the A2L control board ²350 that the²A2L sensor 370 is connected to the system and working properly. Additionally, ²when the A2L²sensor 370 detects an A2L refrigerant leak, it may communicate the A2L ²refrigerant leak to the ²A2L control board 350, which may be configured to receive the signal and ²perform the safety ²measures required by A2L safety standards. In one or more embodiments, the A2L ²sensor 370 and ²the A2L control board 350 may be electrically coupled by way of an RS-485 bus; ²however, one of²ordinary skill in the art would understand that any type of electrical ²connection that allows the²A2L sensor 370 to send a signal to the A2L control board 350 may be used.²While the A2L sensor 370 is depicted as being electrically and communicatively ²coupled to ²the A2L control board 350 by way of a wired connection, one of ordinary skill ²in the art would ²understand that the A2L sensor 370 may just be communicatively coupled to the ²A2L control²board 350 wirelessly. In one or more embodiments, the A2L sensor 370 may be ²communicatively²coupled to the A2L control board 350 by any wireless means, such as Wi-Fi or ²Bluetooth. ²Further, in one or more embodiments, the A2L sensor 370 may be disposed within ²the indoor ²unit 320 so that it may detect an A2L refrigerant leak that occurs within the ²indoor evaporator coil ²324 of the HVAC system 300. As depicted, in one or more embodiments, the A2L ²sensor 370 may²be disposed directly against the indoor evaporator coil to minimize the time ²it takes for the A2L² CA 03206259 2023- 7- 24²<DP=21>²WO 2022 / 165377 ² PCT / US2022 / 014623²sensor 370 to detect an A2L refrigerant leak. Further, while the A2L sensor ²370 is depicted within²the indoor unit 320, one or ordinary skill in the art would understand that ²the A2L sensor 370 may ²instead be disposed within the outdoor unit 330. Further, while a single ²sensor is depicted, one of ²ordinary skill in the art would understand that multiple sensors may be ²incorporated into the HVAC ²system to ensure that an A2L refrigerant leak is detected and the required ²safety measures are²taken within the time required by A2L safety standards. For example, one of ²ordinary skill in the²art would understand that the HVAC system may include two A2L sensors, with ²both A2L sensors ²disposed within the indoor unit, both A2L sensors disposed within the outdoor ²unit, or one A2L ²sensor disposed within each of the indoor unit and the outdoor unit. Thus, one ²of ordinary skill in ²the art would understand that in one or more embodiments, a plurality of A2L ²sensors may be²disposed within the HVAC system with one or more A2L sensors disposed within ²the indoor unit²and / or one or more A2L sensors disposed within the outdoor unit as may be ²determined necessary ²to ensure that an A2L refrigerant leak is detected and the required safety ²measures are taken within ²the time required by A2L safety standards.²Additionally, referring to FIG. 3, in one or more embodiments, the A2L control ²board 350²may be disposed inside of the indoor unit 320. However, one of ordinary skill ²in the art would²understand that, in one or more embodiments, the A2L control board 350 may be ²disposed outside ²of the indoor unit 320 and either connected to the indoor unit 320 or adjacent ²to the indoor unit ²320. Further, in addition to being electrically coupled to the transformer ²325, the indoor control ²board 326, and the A2L sensor 370, as discussed above, the A2L control board ²350 may be²electrically coupled to the outdoor control board 331 by way of the outdoor ²relay 380 and the high²pressure switch 390. In one or more embodiments, the outdoor relay 380 and the ²high pressure ²switch 390 may be electrically coupled in series between the A2L control board ²350 and the ²outdoor control board 331. In one or more embodiments, the outdoor relay 380 ²may be directly ²electrically coupled to the A2L control board 350 such that the outdoor relay ²380 is configured to²open upon receiving a 24 volt A / C power signal from the A2L control board 350. ²Further, in one²21²CA 03206259 2023- 7- 24²<DP=22>²WO 2022 / 165377 ² PCT / US2022 / 014623²or more embodiments, the high pressure switch 390 is electrically coupled to ²the outdoor control²board 331 such that when the high pressure switch 390 opens, the outdoor unit ²330 shuts down ²completely. Furthermore, in one or more embodiments, opening the outdoor relay ²380 causes the ²high pressure switch 390 to open, which causes the outdoor unit 330 to shut ²down completely.²In one or more embodiments, the A2L control board 350 may include a power ²supply 351,²a power-in contact point 352, a first relay 353, a first power-out contact ²point 354, a second relay²355, a second power-out contact point 356, a first sensor connector 357, a ²second sensor connector ²358, a buzzer 359, an LED 360, a dry contact relay 361, first and second ²ventilator contact points ²362a and 362b, and a fuse 363. The power supply 351 may be coupled to ²circuitry on the A2L ²control board 350 such that the A2L control board may open and close, at ²least, the first relay 353,²the second relay 354, and the dry contact relay 361. Further, in one or more ²embodiments, the first²relay 353 may be electrically disposed between the power-in contact point 352 ²and the first power-²out contact point 354, such that when the first relay 353 is open, power from ²the power-in contact ²point 352 does not reach the first power-out contact point 354. Furthermore, ²the fuse 363 may be ²electrically disposed between the power-in contact point 352 and the first ²relay 353. Similarly, in²one or more embodiments, the second relay 355 may be electrically disposed ²between the power-²in contact point 352 and the second power-out contact point 356, such that ²when the second relay ²355 is open, power from the power-in contact point 352 does not reach the ²second power-out ²contact point 356. Additionally, the fuse 363 may be electrically disposed ²between the power-in ²contact point 352 and the second relay 355. By way of example, in one or more ²embodiments,²when the first relay 353 is open, the second relay 355 is closed, and when the ²second relay 355 is²open, the first relay 353 is closed. Further, in one or more embodiments, in ²the default state, the ²first relay 353 is open and the second relay 355 is closed.²In one or more embodiments, the transformer 325 may be electrically coupled to ²the power-²in contact point 352, the first power-out contact point 354 may be ²electrically coupled to the indoor²control board 326, and the second power-out contact point 356 may be ²electrically coupled to²22²CA 03206259 2023- 7- 24²<DP=23>²WO 2022 / 165377 ² PCT / US2022 / 014623²outdoor relay 380. FIG. 3 displays a default state of the A2L control board ²350, where the 24 volt²A / C power coming from the transformer 325 is routed to the outdoor relay 380. ²Further, in one or ²more embodiments, if the A2L control board 350 fails, the relays all revert to ²their default state, ²and thus, if the A2L control board 350 fails, power will be directed to the ²outdoor relay 380, ²causing it to open, thus opening the high pressure switch 390 and shutting off ²the outdoor unit 330.²Furthermore, in one or more embodiments, when the A2L control board 150 is ²turned on, the²second relay 154 immediately opens so that power is not unnecessarily run to ²the outdoor relay ²380 before necessary. Additionally, after the A2L control board 350 is turned ²on, when the system ²is ready to run, the first relay 352 is closed, turning on the HVAC system ²300.²Further, in one or more embodiments, the power supply 351 may be coupled to ²the first²sensor connector 357 and the second sensor connector 358, separately. Thus, in ²one or more²embodiments, the A2L control board 350 may separately test one or more A2L ²sensors 370 before ²closing the first relay 353 and powering up the HVAC system 300. This allows ²for the A2L control ²board 350 to make sure that the sensors 370 are working properly and there are ²no A2L refrigerant ²leaks before beginning the system. While two separate sensor connectors are ²depicted, one of²ordinary skill in the art would understand that the A2L control board may ²instead include a sensor²signal-in contact and a sensor signal-out contact and the one or more sensors ²may be run in series ²instead of in parallel.²Thus, when the A2L control board 350 receives a signal from the A2L sensor 370 ²that there ²is an A2L refrigerant leak, the A2L control board 350 may be configured to ²carry out the required²safety measures required by A2L safety standards. More specifically, in one or ²more embodiments,²if a leak is detected, the A2L control board 350 may be configured to cut off ²power to the indoor ²control board 326 by opening the first relay 353, while directing power ²directly to the outdoor ²relay 380 by closing the second relay 355. Since the indoor unit 320 receives ²power from the ²indoor control board 326, when the A2L sensor detects an A2L refrigerant leak ²and the A2L²control board 350 cuts power to the indoor control board 326, the indoor unit ²320 is configured to²23²CA 03206259 2023- 7- 24²<DP=24>²WO 2022 / 165377 ² PCT / US2022 / 014623²lose power and shut off Further, in one or more embodiments, the blower motor ²323 may be²configured such that if the blower motor 323 loses signal from the indoor ²control board 326, the ²blower motor 323 turns on and stays on. Thus, when the A2L control board 350 ²removes power ²from the indoor control board 326 in response to a detected A2L refrigerant ²leak, the blower motor ²323 will lose a signal from the indoor control board 326 and turn on. Further, ²closing the second²relay 355 in response to an A2L refrigerant leak being detected causes power ²to be diverted directly²to the outdoor relay 380. Furthermore, in one or more embodiments, power being ²diverted directly ²to the outdoor relay 380 causes the outdoor relay 380 to open. Moreover, ²opening the outdoor ²relay 380 is configured to cause the high pressure switch 390 to open. ²Additionally, the outdoor ²unit 330 is configured to shut down completely if the high pressure switch 390 ²is opened. Thus,²opening the second relay 355 is configured to shut down the outdoor unit 330 ²completely. This²allows the HVAC system 300 to meet the A2L safety requirements within the ²requisite time after ²detection of an A2L refrigerant leak.²While FIG. 3 depicts one or more embodiments of the present invention that ²utilize an ²outdoor relay 380 and a high pressure switch 390 in order to shut off the ²outdoor unit in the event²of an A2L refrigerant leak, one of ordinary skill in the art would understand ²that any means of²turning off the compressor of the outdoor unit would work to properly meet the ²A2L safety ²requirements. By way of example, in one or more embodiments, the HVAC system ²may include ²an A2L control board that is electrically coupled to a contactor, where the ²contactor is configured ²to contact the outdoor control board such that the outdoor unit shuts off in ²the event of an A2L²refrigerant leak being detected. Further, in other embodiments, the A2L ²control board may be²communicatively coupled to the outdoor control board by way of an RS-485 ²system ²communication such that the A2L control board can tell the outdoor control ²board to shut down ²the outdoor unit in the event of an A2L leak being detected. Furthermore, in ²one or more ²embodiments, the A2L control board may be electrically coupled to a relay, ²where the relay is²disposed between the outdoor control board and the compressor of the outdoor ²unit such that when²24²CA 03206259 2023- 7- 24²<DP=25>²WO 2022 / 165377 ² PCT / US2022 / 014623²the relay is opened, power from the outdoor control board does not reach the ²compressor, and the²compressor shuts down.²Further, while in one or more embodiments a 24 volt A / C signal is used by the ²A2L control ²board to communicate with the outdoor relay to shut down the outdoor unit, one ²of ordinary skill ²in the art would understand that, in one or more embodiments, the A2L control ²board may send²digital signals to the outdoor relay. One of ordinary skill in the art would ²understand that digital²signals may also be used with a contactor or any other relay coupled to the ²outdoor control board ²to shut down the outdoor unit. Furthermore, in one or more embodiments, the ²A2L control board ²may be wirelessly, communicatively coupled to the outdoor control board such ²that wireless ²signals may be used to turn off the outdoor unit.²Additionally, as discussed above, in one or more embodiments, the A2L control ²board 350²may include a buzzer 359, an LED 360, a dry contact relay 361, and first and ²second ventilator ²contact points 362a and 362b. In one or more embodiments, the dry contact ²relay 361 may be ²electrically coupled to a ventilator (not shown), such that when the A2L ²control board 350 receives ²all A2L refrigerant leak signal from the A2L sensor 370, the dry contact relay ²361 will flip and²turn on the ventilator. Furthermore, in one or more embodiments, when the A2L ²control board²receives an A2L refrigerant leak signal from the A2L sensor, the LED 360 and ²the buzzer 359 will ²receive power. When receiving power, the LED 360 will display an error code ²and the buzzer 359 ²will make sound in order to give visual and auditory alarms that the EIVAC ²system 300 is ²experiencing an A2L refrigerant leak.²Referring now to FIG. 4, a flow chart of an embodiment of a method 400 of ²installing and²operating a communicating FIVAC system using an A2L refrigerant as described ²above with ²respect to FIG. 3, according to one or more embodiments, is illustrated. ²Beginning with an HVAC ²system 300 in which the indoor unit 320 has been disposed on an inside 311 of ²a building 310, the ²outdoor unit 330 has been disposed on an outside 312 of the building 310, the ²indoor control board²326 has been electrically coupled to the thermostat 340 and a blower motor 323 ²of the blower 321,² CA 03206259 2023- 7- 24²<DP=26>²WO 2022 / 165377 ² PCT / US2022 / 014623²and the outdoor control board 331 has been communicatively coupled to the ²indoor control board²326, the method 400 may include one or more of the following: (step 410) ²installing the A2L ²control board 350 and the A2L sensor 370 into the HVAC system 300, (step 420) ²testing the A2L ²sensor 370, (step 430) beginning operation of the HVAC system 300, (step 440) ²checking for A2L ²refrigerant leaks, and (step 450) performing safety measures upon detecting an ²A2L refrigerant²leak.²At step 410, an A2L control board 350 and an A2L sensor 370 may be installed ²into the ²HVAC system 300. Installation ofthe A2L control board 350 and the A2L sensor ²370 may include, ²at least, (step 411) physically coupling the A2L sensor 370 to the indoor ²evaporator coil 324 of ²the indoor unit 320, (step 412) electrically coupling the A2L sensor 370 to ²the A2L control board²350, (step 413) electrically coupling the A2L control board 350 to the indoor ²control board 326,²(step 414) electrically coupling the A2L control board 350 to outdoor control ²board 331. (step 415) ²electrically coupling the A2L control board 350 to the transformer 325, and ²(step 416) turning on ²the A2L control board 150 and opening the second relay 155.²hi one or more embodiments, at step 411, the A2L sensor 370 may be disposed ²within the²indoor unit 320 such that it is adjacent or connected to the indoor evaporator ²coil 324 such that the²A2L sensor 370 is able to detect an A2L refrigerant leak if one occurs. ²Further, at step 412, the ²A2L sensor 370 may be electrically coupled to the A2L control board 350 such ²that the A2L sensor ²370 and the A2L control board 350 have two-way communication between them. By ²way of ²example, in one or more embodiments, an A2L sensor 370 may be electrically ²coupled to a first²sensor connector 357 of the A2L control board 350 by way of an RS-485 bus. One ²of ordinary²skill in the art would appreciate that in other embodiments, any other ²electric coupling that allows ²for two-way communication between the A2L sensor 370 and the A2L control board ²350 may be ²used.²At step 413, the A2L control board 350 may be electrically coupled to the ²indoor control²board 326. In one or more embodiments, a wire capable of carrying 24 volt A / C ²power may be²26²CA 03206259 2023- 7- 24²<DP=27>²WO 2022 / 165377 ² PCT / US2022 / 014623²electrically coupled on one end to a power-in terminal within the indoor ²control board 326 and on²the other end to a first power-out contact 354 of the A2L control board 350. ²Thus, once a ²transformer 325 is electrically coupled to the A2L control board 350, ²providing a 24 volt A / C ²power to the A2L control board 350, and a first relay 353 is closed, the ²indoor control board 326 ²may receive the 24 volt A / C power.²At step 414, the A2L control board 350 may be electrically coupled to the ²outdoor control²board 331. in one or more embodiments, the high pressure switch 390 may be ²electrically coupled ²to the outdoor control board 331 such that when the high pressure switch 390 ²opens, the outdoor ²control board 331 shuts down. Further, the outdoor relay 380 may be ²electrically coupled to the ²high pressure switch 390 such that when the outdoor relay opens, the high ²pressure switch opens.²Furthermore, the outdoor relay 380 may be electrically coupled to a second ²power-out contact 356²of the A2L control board 350 by way of a wire capable of carrying 24 volt A / C ²power. Thus, once ²a transformer 325 is electrically coupled to the A2L control board 350, ²providing a 24 volt A / C ²power to the A2L control board 350, closing the second relay 355 causes the ²outdoor relay 380 to ²open, which causes the high pressure switch 390 to open, which causes the ²outdoor control board²331 to shut down the outdoor unit 330. In one or more embodiments, the default ²for the second²relay 355 may be that it is closed; however, while the HVAC system is running ²and no A2L leak ²is detected, the second relay 355 is kept open. Further, in the event that an ²A2L refrigerant leak is ²detected, the second relay 355 is closed which causes the outdoor unit 330 to ²shut down ²completely.²At step 415, the A2L control board 350 may be electrically coupled to the ²transformer 325.²In one or more embodiments, a wire capable of carrying 24 volt A / C power may ²be electrically ²coupled on one end to a power-out terminal within the transformer 325 and on ²the other end to a ²power-in contact 352 of the A2L control board 350. Thus, once the transformer ²325 is electrically ²coupled to the A2L control board 350, the A2L control board has a 24 volt A / C ²power that it may² distribute to either the indoor control board 326 or the outdoor relay 380.²27²CA 03206259 2023- 7- 24²<DP=28>²WO 2022 / 165377 ² PCT / US2022 / 014623²At step 416, the A2L control board 350 may be turned on and the second relay ²355 may be²opened. In one or more embodiments, when the A2L control board 350 is turned ²on, the relays are ²in the default state, which includes the second relay 355 being closed. Thus, ²in order to make sure ²power is not unnecessarily diverted to the blower motor 323, in one or more ²embodiments, when ²the A2L control board 350 powers up, the A2L control board 350 opens the ²second relay 355.²At step 420, the A2L sensor 370 may be tested to confirm that it is properly ²operational.²Once electrically coupled to the A2L control board 350, in one or more ²embodiments, the A2L ²sensor 370 may perform an internal diagnostic check to make sure that the ²sensor is operating ²properly and may detect an A2L refrigerant leak. If the diagnostic check is ²successful, the A2L ²sensor 370 may communicate the successful diagnostic check to the A2L control ²board 350, which²can begin operation of the HVAC system 300. If the A2L sensor 370 fails the ²diagnostic check,²the A2L sensor 370 will communicate the failed diagnostic check to the A2L ²control board 350, ²which will remain in the default configuration, keeping the HVAC system 300 ²from operating ²until the A2L sensor is repaired or replaced.²At step 430, the A2L control board 350 may begin operation of the HVAC system ²300. In²order to begin operation, in one or more embodiments, the A2L control board ²350 may close the²first relay 353 of the A2L control board 350. Closing the first relay 353 ²allows for the 24 volt A / C ²power that the A2L control board 350 receives from the transformer 325 to pass ²to the indoor ²control board 326 and power up the indoor unit 320.²At step 440, while the HVAC system is running, in one or more embodiments, the ²A2L²sensor 370 may check for A2L refrigerant leaks. The A2L sensor 370 may ²continuously check for²A2L refrigerant leaks while the FIVAC system 300 is running, such that if a ²check comes back ²negative for an A2L refrigerant leak, the A2L sensor 370 repeats step 440. ²However, if the AL2 ²sensor 370 detects an A2L leak, then the A2L sensor 370 communicates the A2L ²refrigerant leak ²to the A2L control board and the HVAC system continues to step 450.²28²CA 03206259 2023- 7- 24²<DP=29>²WO 2022 / 165377 ² PCT / US2022 / 014623²At step 450, the HVAC system 300, by way of the A2L control board 350, may ²perform²safety measures to eliminate the threat of the detected A2L refrigerant leak. ²Specifically, the ²HVAC system 300 may (step 452) open the first relay 353, (step 453) close the ²second relay 355, ²(step 454) close the dry contact relay 361, (step 456) power on the LED 360, ²and (step 458) power ²on the buzzer 359. At step 452, opening the first relay 353 prevents the 24 ²volt A / C power that the²A2L control board 350 receives from the transformer 325 from passing to the ²indoor control board²326, thus removing the 24 volt A / C power from the indoor unit 320. As ²discussed above, removing ²the power from the indoor unit 320 causes the blower motor 323 to lose its ²signal from the indoors ²control board 326 such, which causes the blower motor 323 to turn on and ²remain on. Additionally, ²at step 453, closing the second relay 355 causes the 24 volt A / C power that ²the A2L control board²350 receives from the transformer 325 to pass to the outdoor relay 380. As ²discussed above, the²24 volt A / C power run directly to the outdoor relay 380 causes the outdoor ²relay 380 to open, ²which causes the high pressure switch 390 to open, which causes the outdoor ²control board 331 to ²turn off completely. Further, while listed as separate steps, one of ordinary ²skill would appreciate ²that in one or more embodiments, either step 452 or step 453 may take place ²before the other, or²in other embodiments, step 452 and step 453 may occur simultaneously. ²Additionally, one of²ordinary skill in the art would appreciate that both steps 452 and 453 may be ²completed within the ²requisite time after detection of an A2L refrigerant leak as required by A2L ²safety standards. ²At step 454, in one or more embodiments, the A2L control board 350 may close ²the dry ²contact relay 361 that turns on a ventilator. In one or more embodiments, a ²ventilator may be²connected to the HVAC system 300 by way of first and second ventilator contact ²points 362a and²362b on the A2L control board 350. Thus, when the A2L sensor 370 detects a ²leak, the A2L control ²board 350 may close the dry contact relay 361, which allows power to run ²directly to the ventilator ²and turns on the ventilator. Further, at step 456, when the A2L control board ²350 receives the A2L ²refrigerant leak communication, the A2L control board 350 may provide power to ²the LED 360.²29²CA 03206259 2023- 7- 24²<DP=30>²WO 2022 / 165377 ² PCT / US2022 / 014623²Furthermore, at step 458, when the A2L control board 350 receives the A2L ²refrigerant leak²communication, the A2L control board 350 may provide power to the buzzer 359.²Thus, in one or more embodiments, in response to a communication from the A2L ²sensor ²370 that an A2L refrigerant leak has been detected, the A2L control board 350 ²may turn off the ²indoor unit 320 and the outdoor unit 330, except the blower motor 323, which ²is powered on by²the loss of signal from the indoor control board 326, turn on a ventilator if ²the HVAC system 300²has one, and turn on visual and auditory alarms that an A2L refrigerant leak ²has been detected. ²While the method 400 is described with respect to an HVAC system 300 including ²a single ²A2L sensor 370, one of ordinary skill in the art, would understand that any ²number of sensors may ²be used in the system and the method may include electrically coupling the ²further sensors to the²control board, testing the further sensors, and communicating with the further ²sensors as the further²sensors check for A2L refrigerant leaks.²FIG. 5 shows a non-communicating HVAC system using an A2L refrigerant, ²according to ²one or more embodiments. In one or more embodiments, an I-1VAC system 500 may ²be used to ²distribute cooled or heated air throughout a building 510 to adjust the ²ambient air temperature²inside 511 of the building 510. The HVAC system may include an indoor unit ²520, an outdoor unit²530, a thermostat 540, an A2L control board 550, and an A2L sensor 570. ²Generally, in one or ²more embodiments, the indoor unit 520 may be fluidly coupled to the outdoor ²unit 530 such that ²an A2L refrigerant may flow between the indoor unit 520 and the outdoor unit ²530 to cool or heat ²air within the indoor unit 520. Further, in one or more embodiments, the ²indoor unit 520 may be²indirectly electrically coupled to the thermostat 540, while the outdoor unit ²530 may be directly²electrically coupled to the thermostat 540. The thermostat 540 may be ²configured to use on / off-²type signals for communication and control of the indoor unit 520 and the ²outdoor unit 530. ²Furthermore, in one or more embodiments, the A2L control board 550 may be ²directly electrically ²coupled between the indoor unit 520 and the thermostat 540, such that any ²communication or²signals between the two must pass through the A2L control board 550. Thus, in ²one or more² CA 03206259 2023- 7- 24²<DP=31>²WO 2022 / 165377 ² PCT / US2022 / 014623²embodiments, he A2L control board 550 may act as a passthrough for power to ²portions of the²indoor unit 520, the outdoor unit 530, and the thermostat 540 and may be ²configured to block ²power from getting to certain parts of the indoor unit 520, the outdoor unit ²530, and the thermostat ²540 if there is an A2L refrigerant leak in the system. Additionally, an A2L ²sensor 570 may be ²physically disposed within the indoor unit 520 and electrically coupled to the ²A2L control board²550. The A2L sensor 570 may be configured to send signals to the A2L control ²board 550 when²an A2L refrigerant leak is detected.²In one or more embodiments, indoor unit 520 may be disposed on the inside 511 ²of the ²building 510. The indoor unit 520 may be configured to distribute cooled or ²heated air to rooms ²on the inside 511 of the building 510. The indoor unit 520 may be any type of ²HVAC system that²includes a blower 521 and a heat exchanger 527 having an indoor evaporator ²coil 524. Thus, in²one or more embodiments, the indoor unit 520 may be either a furnace or an air ²handler, as both ²types of system include, at least, a blower and an indoor evaporator coil. ²Additionally, the indoor ²evaporator coil 524 may be disposed adjacent to the blower 521, such that when ²the blower 521 ²blows air within the indoor unit 520, the air is blown through the evaporator ²coil 524.²Further, in one or more embodiments, the blower 521 may include a blower fan ²522 and a²blower motor 523. By way of example, in one or more embodiments, the blower ²motor 523 may ²be constant torque motor, while in other embodiments, the blower motor 523 may ²be a permanent ²split capacitor (PSC) motor. The blower motor 523 may be mechanically coupled ²to the blower ²fan 522 such that when the blower motor 523 is turned on, the blower fan 522 ²is configured to spin²and cause a movement of air out from the blower 521 and through the indoor ²evaporator coil 524.²The indoor evaporator coil 524 may be configured to receive the A2L ²refrigerant on the inside of ²the coil while air from the blower 521 is blown across the outside of the ²coil, which allows for ²heat to exchange either from the A2L refrigerant to the air or vice versa. The ²A2L refrigerant, after ²cooling or heating the air, may be cycled back to the outdoor unit 530, where ²it will go through²the reverse heat exchange process before returning to the indoor evaporator ²coil 524. Additionally,²31²CA 03206259 2023- 7- 24²<DP=32>²WO 2022 / 165377 ² PCT / US2022 / 014623²indoor unit 520 is configured to distribute the air that is blown from the ²blower 521 and across the²indoor evaporator coil 524 to the rooms on the inside 511 of the building 510 ²by way of the force ²of the blower 521.²The indoor unit 520 may also include a transformer 525 and an indoor control ²board 526. ²The transformer 525 may be directly electrically coupled to and configured to ²provide 24 volts ²A / C power to the indoor control board 526. Further, the indoor control board ²526 may be ²electrically coupled to, at least, the A2L control board 550 and the blower ²motor 523.²Further, the outdoor unit 530 may be disposed on an outside 512 of the ²building 510 and be ²configured to use the outdoor environment to reheat or cool down the A2L ²refrigerant after it has ²been run through the indoor evaporator coil 524. The outdoor unit 530 may ²include, but is not²limited to, either a heat pump or an air conditioner. Whether the outdoor unit ²530 is a heat pump²or an air conditioner, the outdoor unit 530 may include a compressor (not ²shown), an outdoor coil ²(not shown), and an outdoor control board 531. The outdoor unit 530 may be ²configured to receive ²power through the outdoor control board 531, which itself is configured to ²receive power from the ²transformer 525 by way of the thermostat 540, the indoor control board 526, ²and the A2L control²board 550. By way of example only, in one or more embodiments, the outdoor ²control board 531²may be configured to receive power and control signals from the thermostat ²540, such that outdoor ²control board 531 may start the condenser after receiving a signal from the ²thermostat 540 to do ²so.²Still referring to FIG. 5, in one or more embodiments. the A2L sensor 570 may ²be configured²to detect an A2L refrigerant leak and send a signal reporting as much. In one ²or more embodiments,²the A2L sensor 570 may be configured to detect an A2L refrigerant leak by one ²of a number of ²methods, including, at least, by detecting an amount or a concentration of A2L ²refrigerant in the ²air that exceeds a leak threshold. The A2L sensor 570 may be electrically ²coupled to and ²communicate with the A2L control board 550. In one or more embodiments, the ²A2L sensor 570²may be electrically coupled to the A2L control board 550 by way of a first ²sensor connector 560.²32²CA 03206259 2023- 7- 24²<DP=33>²WO 2022 / 165377 ² PCT / US2022 / 014623²The A2L sensor 570 may be configured to communicate to the A2L control board ²550 that the²A2L sensor 570 is connected to the system and working properly. Additionally, ²when the A2L ²sensor 570 detects an A2L refrigerant leak, it may communicate the A2L ²refrigerant leak to the ²A2L control board 550, which may be configured to receive the signal and ²perform the safety ²measures required by A2L safety standards. In one or more embodiments, the A2L ²sensor 570 and²the A2L control board 550 may be electrically coupled by way of an RS-485 bus; ²however, one of²ordinary skill in the art would understand that any type of electrical ²connection that allows the ²A2L sensor 570 to send a signal to the A2L control board 550 may be used.²While the A2L sensor 570 is depicted as being electrically and communicatively ²coupled to ²the A2L control board 550 by way of a wired connection, one of ordinary skill ²in the art would²understand that the A2L sensor 570 may just be communicatively coupled to the ²A2L control²board 550 wirelessly. In one or more embodiments, the A2L sensor 570 may be ²communicatively ²coupled to the A2L control board 550 by any wireless means, such as Wi-Fi or ²Bluctooth. ²Further, in one or more embodiments, the A2L sensor 570 may be disposed within ²the indoor ²unit 520 so that it may detect an A2L refrigerant leak that occurs within the ²indoor evaporator coil²524 of the HVAC system 500. As depicted, in one or more embodiments, the A2L ²sensor 570 may²be disposed directly against the indoor evaporator coil to minimize the time ²it takes for the A2L ²sensor 570 to detect an A2L refrigerant leak. Further, while the A2L sensor ²570 is depicted within ²the indoor unit 520, one or ordinary skill in the art would understand that ²the A2L sensor 570 may ²instead be disposed within the outdoor unit 530. Further, while a single ²sensor is depicted, one of²ordinary skill in the art would understand that multiple sensors may be ²incorporated into the HVAC²system to ensure that an A2L refrigerant leak is detected and the required ²safety measures are ²taken within the time required by A2L safety standards. For example, one of ²ordinary skill in the ²art would understand that the HVAC system may include two A2L sensors, with ²both A2L sensors ²disposed within the indoor unit, both A2L sensors disposed within the outdoor ²unit, or one A2L²sensor disposed within each of the indoor unit and the outdoor unit. Thus, one ²of ordinary skill in²33²CA 03206259 2023- 7- 24²<DP=34>²WO 2022 / 165377 ² PCT / US2022 / 014623²the art would understand that in one or more embodiments, a plurality of A2L ²sensors may be²disposed within the HVAC system with one or more A2L sensors disposed within ²the indoor unit ²and / or one or more A2L sensors disposed within the outdoor unit as may be ²determined necessary ²to ensure that an A2L refrigerant leak is detected and the required safety ²measures are taken within ²the time required by A2L safety standards.²Additionally, referring to FIG. 5, in one or more embodiments, the A2L control ²board 550²may be disposed inside of the indoor unit 520. However, one of ordinary skill ²in the art would ²understand that, in one or more embodiments, the A2L control board 550 may be ²disposed outside ²of the indoor unit 520 and either connected to the indoor unit 520 or adjacent ²to the indoor unit ²520. Further, as discussed above, the A2L control board 550 may be ²electrically coupled to the² indoor control board 526, the thermostat 540, and the A2L sensor 570.²In one or more embodiments, the A2L control board 550 may include a power ²supply (not ²shown), a first terminal block 551, a second terminal block 552, an R wire ²relay 553, an G wire ²relay 554, a W1 wire relay 555, a W2 wire relay 556, a Y1 wire relay 557, a Y2 ²wire relay 558, ²an alarm relay 559, a first sensor connector 560, a second sensor connector ²561, a buzzer 562, an²LED 563, a dry contact relay 564, and first and second ventilator contact ²points 565a and 565b.²The power supply may be coupled to circuitry on the A2L control board 550 such ²that the A2L ²control board may open and close, at least, the R wire relay 553, the G wire ²relay 554, the W1 wire ²relay 555, the W2 wire relay 556, the Y1 wire relay 557, the Y2 wire relay ²558, the alarm relay ²559, and the dry contact relay 564.²In one or more embodiments, the thermostat 540 may be electrically coupled to ²the first²terminal block 551, and the indoor control board 526 may be electrically ²coupled to the second ²terminal block 552. Further, in one or more embodiments, any signals received ²by the A2L control ²board 550 from the thermostat 540 may be passed unchanged, by the A2L control ²board 550, to ²the indoor control board 530 through the second terminal block 552.²34²CA 03206259 2023- 7- 24²<DP=35>²WO 2022 / 165377 ² PCT / US2022 / 014623²In one or more embodiments, the R wire relay 553 may be electrically disposed ²between the²power supply and the R wire connection of the first terminal block 551. Thus, ²when the R wire ²relay 553 is closed, 24 volt A / C power may be delivered from the A2L control ²board 550 to the ²thermostat 540 via the first terminal block 551, which powers the thermostat ²540 on. Further, when ²the R wire relay 553 is open, no power is able to reach the thermostat, and ²thus, the thermostat²and, indirectly, the outdoor unit 530 are turned off completely. Additionally, ²as depicted in FIG.²5, in one or more embodiments, the default state for the R wire relay 553 is ²to be open.²In one or more embodiments, the G wire relay 554 may be electrically disposed ²between the ²power supply and the G wire connection of the second terminal block 552. Thus, ²when the G wire ²relay 554 is closed, 24 volt A / C power may be delivered from the A2L control ²board 550 to the²indoor control board 526 via the first terminal block 551, which signals the ²indoor control board²526 to power the blower motor 523 on. Further, when the G wire relay 554 is ²open, no signal is ²sent along the G wire to the indoor control board 526, and thus, the blower ²motor 523 is powered ²off. Additionally, as depicted in FIG. 5, in one or more embodiments, the ²default state for the G ²wire relay 554 is to be closed.²In one or more embodiments, the W1 wire relay 555 may be electrically disposed ²between²the power supply and the WI wire connection of the second terminal block 552, ²and the W2 wire ²relay 556 may be electrically disposed between the power supply and the W2 ²wire connection of ²the second terminal block 552. Thus, when the W1 wire relay 555 and the W2 ²wire relay 556 are ²closed, 24 volt A / C power may be delivered from the A2L control board 550 to ²the indoor control²board 526 via the first terminal block 551, which signals the indoor control ²board 526 to run the²heating system's first and second stages, respectively. Further, when the W1 ²wire relay 555 and ²W2 wire relay 556 are open, no signal is sent along the W1 or W2 wires to the ²indoor control ²board 526, and thus, the heating system is powered off. Additionally, as ²depicted in FIG. 5, in one ²or more embodiments, the default states for the W1 wire relay 555 and the W2 ²wire relay 556 are² to be open.² CA 03206259 2023- 7- 24²<DP=36>²WO 2022 / 165377 ² PCT / US2022 / 014623²In one or more embodiments, the Y1 wire relay 557 may be electrically disposed ²between²the power supply and the Y1 wire connection of the second terminal block 552, ²and the Y2 wire ²relay 558 may be electrically disposed between the power supply and the Y2 ²wire connection of ²the second terminal block 552. Thus, when the Y1 wire relay 557 and the Y2 ²wire relay 558 are ²closed, 24 volt A / C power may be delivered from the A2L control board 550 to ²the indoor control²board 526 via the first terminal block 551, which signals the indoor control ²board 526 to run the²cooling system's first and second stages, respectively. Further, when the Y1 ²wire relay 557 and ²Y2 wire relay 558 are open, no signal is sent along the Y1 or Y2 wires to the ²indoor control board ²526, and thus, the cooling system is powered off. Additionally, as depicted in ²FIG. 5, in one or ²more embodiments, the default states for the Y1 wire relay 557 and the Y2 wire ²relay 558 are to²be closed.²Additionally. in one or more embodiments, the alarm relay 559 may be ²electrically disposed ²between the power supply and an alarm (not shown), which includes, in part, ²the buzzer 562 and ²the LED 563. Thus, when the alarm relay 559 is closed, 24 volt A / C power may ²be delivered to ²the alarm on the A2L control board 550, which powers at least the buzzer 562 ²and the LED 563²on. Further, when the alarm relay 559 is open, no power is delivered to the ²alarm on the A2L²control board and it remains powered off Additionally, as depicted in FIG. 5, ²in one or more ²embodiments, the default state for the alarm relay 559 is to be closed.²Lastly, in one or more embodiments, the dry contact relay 564 may be ²electrically disposed ²between the power supply and a ventilator (not shown) if the HVAC system 500 ²includes a²ventilator, which is electrically coupled to the A2L control board 550 by way ²of the first and²second ventilator contact points 565a and 565b. Thus, when the dry contact ²relay 564 is closed, 24 ²volt A / C power may be delivered to the ventilator, which powers the ventilator ²on. Further, when ²the dry contact relay 564 is open, no power is delivered to the ventilator and ²it remains powered ²off Additionally, as depicted in FIG. 5, in one or more embodiments, the ²default state for the dry²contact relay 564 is to be closed.²36²CA 03206259 2023- 7- 24²<DP=37>²WO 2022 / 165377 ² PCT / US2022 / 014623²Further, in one or more embodiments, once the system is turned on, the A2L ²control board²550 may be configured to open all relays except for the R wire relay 553, ²which may be configured ²to be closed so as to provide the 24 volt A / C power to the thermostat 540 and ²power the thermostat ²540 on. Furthermore, as discussed above, in one or more embodiments, the A2L ²control board 550 ²may be configured to act as a passthrough for any signals the thermostat sends ²during operation of²the system. By way of example only, if the I-1VAC system 500 is required to ²cool the inside of a²building, the thermostat may send signals along both the G and Yl wires to the ²A2L control board ²550. The A2L control board 550 may be configured to receive those signals and ²correspondingly ²close the G wire relay 554 and the Y1 wire relay 557 such that a 24 volt A / C ²signal may be passed ²to the indoor control board 526 along the G wire and the Y1 wire. Once ²received, the indoor control²board 526 may be configured to turn on the blower motor 523 and run the ²cooling system as is²called for by a signal on the G wire and Y1 wire.²Further, in one or more embodiments, the power supply may be coupled to the ²first sensor ²connector 560 and the second sensor connector 561, separately. Thus, in one or ²more ²embodiments, the A2L control board 550 may separately test one or more A2L ²sensors 570 before²closing the R wire relay 553 and powering up the thermostat 540 and the ²outdoor unit 530. This²allows for the A2L control board 550 to make sure that the sensors 570 are ²working properly and ²there are no A2L refrigerant leaks before beginning the system. While two ²separate sensor ²connectors are depicted, one of ordinary skill in the art would understand ²that the A2L control ²board may instead include a sensor signal-in contact and a sensor signal-out ²contact and the one² or more sensors may be run in series instead of in parallel.²Thus, when the A2L control board 550 receives a signal from the A2L sensor 570 ²that there ²is an A2L refrigerant leak, the A2L control board 550 may be configured to ²carry out the required ²safety measures required by A2L safety standards. More specifically, in one or ²more embodiments, ²if a leak is detected, the A2L control board 550 may be configured to cut off ²power to the²thermostat 540, and thus, to the outdoor unit 530, by opening the R wire relay ²553. Further, if a²37²CA 03206259 2023- 7- 24²<DP=38>²WO 2022 / 165377 ² PCT / US2022 / 014623²leak is detected, the A2L control board 550 may be configured to cut off power ²to all parts of the²indoor unit 520 except the blower motor 523 by opening at least the W1 wire ²relay 555 and the ²W2 wire relay 556 and closing at least the G wire relay 554. Opening the W1 ²wire relay 555 and ²the W2 wire relay 556 will ensure that all heating functions are shut off, ²while closing the G wire ²relay 554 will ensure that the blower motor 523 is turned on. In one or more ²embodiments, the Y1²wire relay 557 and the Y2 wire relay 558 may also be closed as cutting power ²to the outdoor unit²530 ensures that all cooling functionality is shut off, but the signal on the ²Y1 and Y2 wire cause ²the indoor control board 526 to turn up the speed on the blower motor 523 so ²it blows more air, ²faster. This allows the HVAC system 500 to meet the A2L safety requirements ²within the requisite ²time after detection of an A2L refrigerant leak.²Additionally, in one or more embodiments, if a leak is detected, the A2L ²control board 550²may close the alarm relay 559 and the dry contact relay 564. Closing the alarm ²relay 559 will cause ²the alarm on the A2L control panel 550 to be powered on, which will include, ²at least, turning on ²the buzzer 562 and the LED 563 to give auditory and visual alerts that a leak ²has been detected. ²Further, if the HVAC system 500 includes a ventilator, closing the dry contact ²relay 564 will cause²the ventilator to be powered on, which will aid in removing any concentrations ²of A2L refrigerant²leaked into the HVAC system 500.²Further, in one or more embodiments, if the A2L control board 550 fails, the ²relays all revert ²to their default state. As discussed above and as depicted in FIG. 5, in a ²default state, the G wire ²relay 554, the Y1 wire relay 557, the Y2 wire relay 558, the alarm relay 559, ²and the dry contact²relay 564 may be closed, while the R wire relay 553, the W1 wire relay 555, ²and the W2 wire relay²556 may be open. Thus, if the A2L control board 550 fails, power will be ²blocked from the ²thermostat 540, and thus, from the outdoor unit 530 and the only signals the ²indoor unit 520 will ²receive and act on will cause the blower motor 523 to be turned on as fast as ²it can go. Additionally, ²if the A2L control board 550 fails, the alarm will be turned on and the ²ventilator will be turned on.²38²CA 03206259 2023- 7- 24²<DP=39>²WO 2022 / 165377 ² PCT / US2022 / 014623²Referring now to FIG. 6, a flow chart of an embodiment of a method 600 of ²installing and²operating a non-communicating HVAC system using an A2L refrigerant as ²described above with ²respect to FIG. 5, according to one or more embodiments, is illustrated. ²Beginning with an HVAC ²system 500 in which the indoor unit 520 has been disposed on an inside 511 of ²a building 510, the ²outdoor unit 530 has been disposed on an outside 512 of the building 510, the ²indoor control board²526 has been electrically coupled to a blower motor 523 of the blower 521, and ²the outdoor control²board 531 has been electrically coupled to the thermostat 540, the method 600 ²may include one or ²more of the following: (step 610) installing the A2L control board 550 and the ²A2L sensor 570 ²into the HVAC system 500, (step 620) testing the A2L sensor 570, (step 630) ²beginning operation ²of the HVAC system 500, (step 640) checking for A2L refrigerant leaks, and ²(step 650) performing² safety measures upon detecting an A2L refrigerant leak.²At step 610, an A2L control board 550 and an A2L sensor 570 may be installed ²into the ²HVAC system 500. Installation of the A2L control board 550 and the A2L sensor ²570 may include, ²at least, (step 611) physically coupling the A2L sensor 570 to the indoor ²evaporator coil 524 of ²the indoor unit 520, (step 612) electrically coupling the A2L sensor 570 to ²the A2L control board²550, (step 613) electrically coupling the A2L control board 550 to the indoor ²control board 526,²(step 614) electrically coupling the A2L control board 550 to the thermostat ²540, and (step 615) ²turning on the A2L control board 550 and opening the G wire relay 554, the Y1 ²wire relay 557, ²the Y2 wire relay 558, the alarm relay 559, and the dry contact relay 564.²In one or more embodiments, at step 611, the A2L sensor 570 may be disposed ²within the²indoor unit 520 such that it is adjacent or connected to the indoor evaporator ²coil 524 such that the²A2L sensor 570 is able to detect an A2L refrigerant leak if one occurs. ²Further, at step 612, the ²A2L sensor 570 may be electrically coupled to the A2L control board 550 such ²that the A2L sensor ²570 and the A2L control board 550 have two-way communication between them. By ²way of ²example, in one or more embodiments, an A2L sensor 570 may be electrically ²coupled to a first²sensor connector 557 of the A2L control board 550 by way of an RS-485 bus. One ²of ordinary²39²CA 03206259 2023- 7- 24²<DP=40>²WO 2022 / 165377 ² PCT / US2022 / 014623²skill in the art would appreciate that in other embodiments, any other ²electric coupling that allows²for two-way communication between the A2L sensor 570 and the A2L control board ²550 may be ²used.²At step 613, the A2L control board 550 may be electrically coupled to the ²indoor control ²board 526. In one or morc embodiments, R, C, G, Wl, W2, Yl, Y2, 0, and Dchum ²wires may be²electrically coupled on one end to a terminal block within the indoor control ²board 526 and on the²other end to the second terminal block 552 of the A2L control board 550. ²Further, at step 614, the ²A2L control board 550 may be electrically coupled to the thermostat 540. In ²one or more ²embodiments, R, C, G, Wl, W2, Yl, Y2, 0, and Dehum wires may be electrically ²coupled on one ²end to a terminal block within the thermostat 540 and on the other end to the ²first terminal block²551 of the A2L control board 550. Thus, in one or more embodiments, the A2L ²control board 550²may be configured to receive control signals from the thermostat 540 and send ²those same control ²signals to the indoor control board 526. Further, in one or more embodiments, ²the A2L control ²board 550 may be configured to provide power to the thermostat 540 by way of ²the R wire so as ²to power on the thermostat, which in turn powers on the outdoor unit 530. In ²one or more²embodiments, the power provided to the thermostat 540 by the A2L control board ²550 is a 24 volt²A / C power.²At step 615, the A2L control board 550 may be turned on, and the G wire relay ²554, the Y1 ²wire relay 557, the Y2 wire relay 558, the alarm relay 559, and the dry ²contact relay 564 may be ²opened. In one or more embodiments, when the A2L control board 550 is turned ²on, the relays are²in the default state, which includes the G wire relay 554, the Y1 wire relay ²557, the Y2 wire relay²558, the alarm relay 559, and the dry contact relay 564 being closed. Thus, in ²order to make sure ²signals are not unnecessarily provided to the indoor control board 526 to tum ²on the blower motor ²523 and the alarm and ventilator are not unnecessarily run, in one or more ²embodiments, when the ²A2L control board 550 powers up, the A2L control board opens the G wire relay ²554, the Y1 wire²relay 557, the Y2 wire relay 558, the alarm relay 559, and the dry contact ²relay 564.² CA 03206259 2023- 7- 24²<DP=41>²WO 2022 / 165377 ² PCT / US2022 / 014623²At step 620, the A2L sensor 570 may be tested to confirm that it is properly ²operational.²Once electrically coupled to the A2L control board 550, in one or more ²embodiments, the A2L ²sensor 570 may perform an internal diagnostic check to make sure that the ²sensor is operating ²properly and may detect an A2L refrigerant leak. If the diagnostic check is ²successful, the A2L ²sensor 570 may communicate the successful diagnostic check to the A2L control ²board 550, which²can begin operation of the HVAC system 500. If the A2L sensor 570 fails the ²diagnostic check,²the A2L sensor 570 will communicate the failed diagnostic check to the A2L ²control board 550, ²which will remain in the default configuration, keeping the HVAC system 500 ²from operating ²until the A2L sensor is repaired or replaced.²At step 630, the A2L control board 550 may begin operation of the HVAC system ²500. In²order to begin operation, in one or more embodiments, the A2L control board ²550 may close the²R wire relay 553 of the A2L control board 550. Closing the R wire relay 553 ²allows for the 24 volt ²A / C power of the A2L control board 550 to pass to the thermostat 540 and ²therefrom to the outdoor ²unit 530. Once power has been turned on for the thermostat 540, it may then be ²able to send signals ²to the indoor unit 520, through the A2L control board 550, as well as to the ²outdoor unit 530 and²the HVAC system 500 may be fully operational.²At step 640, while the HVAC system is running, in one or more embodiments, the ²A2L ²sensor 570 may check for A2L refrigerant leaks. The A2L sensor 570 may ²continuously check for ²A2L refrigerant leaks while the HVAC system 500 is running, such that if a ²check comes back ²negative for an A2L refrigerant leak, the A2L sensor 570 repeats step 640. ²However, if the AL2²sensor 570 detects an A2L leak, then the A2L sensor 570 communicates the A2L ²refrigerant leak²to the A2L control board and the HVAC system continues to step 650.²At step 650, the HVAC system 500, by way of the A2L control board 550, may ²perform ²safety measures to eliminate the threat of the detected A2L refrigerant leak. ²Specifically, the ²HVAC system 500 may (step 652) open the R wire relay 553, (step 653) close the ²G wire relay²554, (step 654) open the W1 wire relay 555 and the W2 wire relay 556, (step ²655) close the Y1²41²CA 03206259 2023- 7- 24²<DP=42>²WO 2022 / 165377 ² PCT / US2022 / 014623²wire relay 557 and the Y2 wire relay 558, (step 656) close the dry contact ²relay 564, and (step 657)²close the alarm relay 559.²At step 652, opening the R wire relay 553 prevents the A2L control board 550 ²from ²distributing the 24 volt A / C power to the thermostat 540. Removing the 24 volt ²A / C power from ²the thermostat 540 in turn removes power from the outside unit 530, which is ²configured to receive²24 volt A / C power signals directly from the thermostat. Additionally, at step ²653, closing the G²wire relay 554 causes the A2L control board 550 to send a 24 volt A / C power ²along the G wire to ²the inside control board 526, which starts the blower motor 523 when it ²receives the signal along ²the G wire. Further, at step 654, opening the W1 wire relay 555 and the W2 ²wire relay 556 ensures ²that no signal is sent to the indoor control board 526 and thus, heating ²operations are not run while²the system is experiencing a refrigerant leak. Furthermore, at step 655, ²closing the Y1 wire relay²557 and the Y2 wire relay 558 causes the A2L control board 550 to send a 24 ²volt A / C power ²along the Y1 and Y2 wires to the indoor control board 526. The indoor control ²board 526 interprets ²the signals along the Y1 and Y2 wires to call for first and second stage ²cooling operations, but ²because the compressor in the outdoor unit 530 is powered off, the only effect ²is that the indoor² control board 526 runs the blower motor 532 at its highest level.²Further, at step 656, closing the dry contact relay 564 causes the 24 volt A / C ²power from the ²A2L control board 550 to power an attached ventilator on if the HVAC system ²500 includes a ²ventilator. Additionally, at step 657, closing the alarm relay 559 causes the ²24 volt A / C power ²from the A2L control board 550 to power the alarm on, which includes, at ²least, powering on visual²and auditory alarms in the form of the buzzer 562 and the LED 563.²Further, while listed as separate steps, one of ordinary skill would ²appreciate that in one or ²more embodiments, steps 652-657 may take place in any order, or in other ²embodiments, steps ²652-657 may occur simultaneously. Additionally, one of ordinary skill in the ²art would appreciate ²that all steps 652-657 may be completed within the requisite time after ²detection of an A2L²refrigerant leak as required by A2L safety standards.²42²CA 03206259 2023- 7- 24²<DP=43>²WO 2022 / 165377 ² PCT / US2022 / 014623²Thus, in one or more embodiments, in response to a communication from the A2L ²sensor²570 that an A2L refrigerant leak has been detected, the A2L control board 550 ²may turn off the ²outdoor unit 530, turn on a ventilator if the HVAC system 500 has one, turn on ²visual and auditory ²alarms that an A2L refrigerant has been detected, and ensure that the only ²signals the indoor unit ²520 will receive and act on will cause the blower motor 523 to be turned on as ²fast as it can go.²While the method 600 is described with respect to an LIVAC system 500 ²including a single²A2L sensor 570, one of ordinary skill in the art, would understand that any ²number of sensors may ²be used in the system and the method may include electrically coupling the ²further sensors to the ²control board, testing the further sensors, and communicating with the further ²sensors as the further ²sensors check for A2L refrigerant leaks.²FIG. 7 shows a communicating HVAC system using an A2L refrigerant, according ²to a one²or more embodiments. In one or more embodiments, an HVAC system 700 may be ²used to ²distribute cooled or heated air throughout a building 710 to adjust the ²ambient air temperature ²inside 711 of the building 710. The LIVAC system may include an indoor unit ²720, an outdoor unit ²730, a thermostat 740, an A2L control board 750, an A2L sensor 770, an outdoor ²relay 70, and a² high pressure switch 790.²Generally, in one or more embodiments, the indoor unit 720 may be fluidly ²coupled to the ²outdoor unit 730 such that an A2L refrigerant may flow between the indoor unit ²720 and the ²outdoor unit 730 to cool or heat air within the indoor unit 720. Further, in ²one or more ²embodiments, both the indoor unit 720 and the outdoor unit 730 may be ²communicatively coupled²to each other by way of an RS-485 system communication. Furthermore, in one or ²more ²embodiments, the A2L control board 750 may be directly electrically and / or ²communicatively ²coupled to both the indoor unit 720 and the thermostat 740, and also ²indirectly electrically coupled ²to the outdoor unit 730 by way of the outdoor relay 780 and the high pressure ²switch 790. The ²thermostat 740 may be electrically coupled to the A2L control board 750 such ²that it may send²communications and signals to the indoor unit 720 through the A2L control ²board 750. Thus, the²43²CA 03206259 2023- 7- 24²<DP=44>²WO 2022 / 165377 ² PCT / US2022 / 014623²A2L control board 750 may be configured to directly affect the operation of ²the indoor unit 720²by way of those communications and signals and may be configured to directly ²affect the operation ²of the outdoor unit 730 by way of the outdoor relay 780 and the high pressure ²switch 790. Further, ²the A2L sensor 770 may be physically disposed within the indoor unit 720 and ²electrically coupled ²to the A2L control board 750. The A2L sensor 770 may be configured to send ²signals to the A2L² control board 750 when an A2L refrigerant leak is detected.²While the A2L control board 750 is depicted as being electrically and ²communicatively ²coupled to the indoor unit 720, the thermostat 740, and the A2L sensor 770 by ²way of a wired ²connection, one of ordinary skill in the art would understand that the indoor ²unit 720, the ²thermostat 740, and the A2L sensor 770 may just be communicatively coupled to ²the A2L control²board 750 wirelessly. In one or more embodiments, the indoor unit 720, the ²thermostat 740, and²the A2L sensor 770 may be communicatively coupled to the A2L control board 750 ²by any ²wireless means, such as Wi-Fi or Bluetooth.²In one or more embodiments, indoor unit 720 may be disposed on the inside 711 ²of the ²building 710. The indoor unit 720 may be configured to distribute cooled or ²heated air to rooms²on the inside 711 of the building 710. The indoor unit 720 may be any type of ²HVAC system that²includes a blower 721 and a heat exchanger 727 having an indoor evaporator ²coil 724. Thus, in ²one or more embodiments, the indoor unit 720 may be either a furnace or an air ²handler, as both ²types of system include, at least, a blower and an indoor evaporator coil. ²Additionally, the indoor ²evaporator coil 724 may be disposed adjacent to the blower 721, such that when ²the blower 721²blows air within the indoor unit 720, the air is blown through the evaporator ²coil 724.²Further, in one or more embodiments, the blower 721 may include a blower fan ²722 and a ²blower motor 723. By way of example, in one or more embodiments, the blower ²motor 723 may ²be constant torque motor, while in other embodiments, the blower motor 723 may ²be a permanent ²split capacitor (PSC) motor. The blower motor 723 may be mechanically coupled ²to the blower²fan 722 such that when the blower motor 723 is turned on, the blower fan 722 ²is configured to spin²44²CA 03206259 2023- 7- 24²<DP=45>²WO 2022 / 165377 ² PCT / US2022 / 014623²and cause a movement of air out from the blower 721 and through the indoor ²evaporator coil 724.²The indoor evaporator coil 724 may be configured to receive the A2L ²refrigerant on the inside of ²the coil while air from the blower 721 is blown across the outside of the ²coil, which allows for ²heat to exchange either from the A2L refrigerant to the air or vice versa. The ²A2L refrigerant, after ²cooling or heating the air, may be cycled back to the outdoor unit 730, where ²it will go through²the reverse heat exchange process before returning to the indoor evaporator ²coil 724. Additionally,²indoor unit 720 is configured to distribute the air that is blown from the ²blower 721 and across the ²indoor evaporator coil 724 to the rooms on the inside 711 of the building 710 ²by way of the force ²of the blower 721.²The indoor unit 720 may also include a transformer 725 and an indoor control ²board 726.²The transformer 725 may be directly electrically coupled to and configured to ²provide 24 volts²A / C power to the indoor control board 726. Further, the indoor control board ²726 may be ²electrically coupled to, at least, the A2L control board 750 and the blower ²motor 723.²Further, the outdoor unit 730 may be disposed on an outside 712 of the ²building 710 and be ²configured to use the outdoor environment to reheat or cool down the A2L ²refrigerant after it has²been run through the indoor evaporator coil 724. The outdoor unit 730 may ²include, but is not²limited to, either a heat pump or an air conditioner. Whether the outdoor unit ²730 is a heat pump ²or an air conditioner, the outdoor unit 730 may include a compressor (not ²shown), an outdoor coil ²(not shown), and an outdoor control board 731. The outdoor unit 730 may be ²configured to ²communicate with the indoor unit 720 through RS-485 system communication ²between the indoor²control board 726 and the outdoor control board 731. Further, the outdoor ²control board 731 may²be electrically coupled to the A2L control board 750 as discussed below.²Still referring to FIG. 7, in one or more embodiments, the A2L sensor 770 may ²be configured ²to detect an A2L refrigerant leak and send a signal reporting as much. In one ²or more embodiments, ²the A2L sensor 770 may be configured to detect an A2L refrigerant leak by one ²of a number of²methods, including, at least, by detecting an amount or a concentration of A2L ²refrigerant in the² CA 03206259 2023- 7- 24²<DP=46>²WO 2022 / 165377 ² PCT / US2022 / 014623²air that exceeds a leak threshold. The A2L sensor 770 may be electrically ²coupled to and²communicate with the A2L control board 750. In one or more embodiments, the ²A2L sensor 770 ²may be electrically coupled to the A2L control board 750 by way of a first ²sensor connector 760. ²The A2L sensor 770 may be configured to communicate to the A2L control board ²750 that the ²A2L sensor 770 is connected to the system and working properly. Additionally, ²when the A2L²sensor 770 detects an A2L refrigerant leak, it may communicate the A2L ²refrigerant leak to the²A2L control board 750, which may be configured to receive the signal and ²perform the safety ²measures required by A2L safety standards. In one or more embodiments, the A2L ²sensor 770 and ²the A2L control board 750 may be electrically coupled by way of an RS-485 bus; ²however, one of ²ordinary skill in the art would understand that any type of electrical ²connection that allows the² A2L sensor 770 to send a signal to the A2L control board 750 may be used.²Further, in one or more embodiments, the A2L sensor 770 may be disposed within ²the indoor ²unit 720 so that it may detect an A2L refrigerant leak that occurs within the ²indoor evaporator coil ²724 of the HVAC system 700. As depicted, in one or more embodiments, the A2L ²sensor 770 may ²be disposed directly against the indoor evaporator coil to minimize the time ²it takes for the A2L²sensor 770 to detect an A2L refrigerant leak. Further, while the A2L sensor ²770 is depicted within²the indoor unit 720, one or ordinary skill in the art would understand that ²the A2L sensor 770 may ²instead be disposed within the outdoor unit 730. Further, while a single ²sensor is depicted, one of ²ordinary skill in the art would understand that multiple sensors may be ²incorporated into the HVAC ²system to ensure that an A2L refrigerant leak is detected and the required ²safety measures are²taken within the time required by A2L safety standards. For example, one of ²ordinary skill in the²art would understand that the HVAC system may include two A2L sensors, with ²both A2L sensors ²disposed within the indoor unit, both A2L sensors disposed within the outdoor ²unit, or one A2L ²sensor disposed within each of the indoor unit and the outdoor unit. Thus, one ²of ordinary skill in ²the art would understand that in one or more embodiments, a plurality of A2L ²sensors may be²disposed within the HVAC system with one or more A2L sensors disposed within ²the indoor unit²46²CA 03206259 2023- 7- 24²<DP=47>²WO 2022 / 165377 ² PCT / US2022 / 014623²and / or one or more A2L sensors disposed within the outdoor unit as may be ²determined necessary²to ensure that an A2L refrigerant leak is detected and the required safety ²measures are taken within ²the time required by A2L safety standards.²Additionally, referring to FIG. 7, in one or more embodiments, the A2L control ²board 750 ²may be disposed inside of the indoor unit 720. However, one of ordinary skill ²in the art would²understand that, in one or more embodiments, the A2L control board 750 may be ²disposed outside²of the indoor unit 720 and either connected to the indoor unit 720 or adjacent ²to the indoor unit ²720. Further, in addition to being electrically coupled to the indoor control ²board 726, the ²thermostat 740, and the A2L sensor 770, as discussed above, the A2L control ²board 750 may be ²electrically coupled to the outdoor control board 731 by way of the outdoor ²relay 780 and the high²pressure switch 790. In one or more embodiments, the outdoor relay 780 and the ²high pressure²switch 790 may be electrically coupled in series between the A2L control board ²750 and the ²outdoor control board 731. In one or more embodiments, the outdoor relay 780 ²may be directly ²electrically coupled to the A2L control board 750 such that the outdoor relay ²780 is configured to ²open upon receiving a 24 volt A / C power signal from the A2L control board 750. ²Further, in one²or more embodiments, the high pressure switch 790 is electrically coupled to ²the outdoor control²board 731 such that when the high pressure switch 790 opens, the outdoor unit ²730 shuts down ²completely. Furthermore, in one or more embodiments, opening the outdoor relay ²780 causes the ²high pressure switch 790 to open, which causes the outdoor unit 730 to shut ²down completely.²In one or more embodiments, the A2L control board 750 may include a power ²supply (not²shown), a first terminal block 751, a second terminal block 752, an R wire ²relay 753, an G wire²relay 754, a W1 wire relay 755, a W2 wire relay 756, a Y1 wire relay 757, a Y2 ²wire relay 758, ²an alarm relay 759, a first sensor connector 760, a second sensor connector ²761, a buzzer 762, an ²LED 763, a dry contact relay 764, first and second ventilator contact points ²765a and 765b, and an ²outdoor unit relay 766. The power supply may be coupled to circuitry on the ²A2L control board²750 such that the A2L control board may open and close, at least, the R wire ²relay 753, the G wire²47²CA 03206259 2023- 7- 24²<DP=48>²WO 2022 / 165377 ² PCT / US2022 / 014623²relay 754, the W1 wire relay 755, the W2 wire relay 756, the Y1 wire relay ²757, the Y2 wire relay²758, the alarm relay 759, the dry contact relay 764 and the outdoor unit relay ²766.²In one or more embodiments, the thermostat 740 may be electrically coupled to ²the first ²terminal block 751, and the indoor control board 726 may be electrically ²coupled to the second ²terminal block 752. Further, in one or more embodiments, any signals received ²by the A2L control²board 750 from the thermostat 740 may be passed unchanged, by the A2L control ²board 750, to²the indoor control board 730 through the second terminal block 752.²In one or more embodiments, the R wire relay 753 may be electrically disposed ²between the ²power supply and the R wire connection of the first terminal block 751. Thus, ²when the R wire ²relay 753 is closed, 24 volt A / C power may be delivered from the A2L control ²board 750 to the²thermostat 740 via the first terminal block 751, which powers the thermostat ²740 on. Further, when²the R wire relay 753 is open, no power is able to reach the thermostat, and ²thus, the thermostat is ²turned off completely. Additionally, as depicted in FIG. 7, in one or more ²embodiments, the default ²state for the R wire relay 753 is to be open.²In one or more embodiments, the G wire relay 754 may be electrically disposed ²between the²power supply and the G wire connection of the second terminal block 752. Thus, ²when the G wire²relay 754 is closed, 24 volt A / C power may be delivered from the A2L control ²board 750 to the ²indoor control board 726 via the first terminal block 751, which signals the ²indoor control board ²726 to power the blower motor 723 on. Further, when the G wire relay 754 is ²open, no signal is ²sent along the G wire to the indoor control board 726, and thus, the blower ²motor 723 is powered²off. Additionally, as depicted in FIG. 7, in one or more embodiments, the ²default state for the G²wire relay 754 is to be closed.²In one or more embodiments, the W1 wire relay 755 may be electrically disposed ²between ²the power supply and the WI wire connection of the second terminal block 752, ²and the W2 wire ²relay 756 may be electrically disposed between the power supply and the W2 ²wire connection of²the second terminal block 752. Thus, when the W1 wire relay 755 and the W2 ²wire relay 756 are²48²CA 03206259 2023- 7- 24²<DP=49>²WO 2022 / 165377 ² PCT / US2022 / 014623²closed, 24 volt A / C power may be delivered from the A2L control board 750 to ²the indoor control²board 726 via the first terminal block 751, which signals the indoor control ²board 726 to run the ²heating system's first and second stages, respectively. Further, when the W1 ²wire relay 755 and ²W2 wire relay 756 are open, no signal is sent along the WI or W2 wires to the ²indoor control ²board 726, and thus, the heating system is powered off. Additionally, as ²depicted in FIG. 7, in one²or more embodiments, the default states for the WI wire relay 755 and the W2 ²wire relay 756 are²to be open.²In one or more embodiments, the Y1 wire relay 757 may be electrically disposed ²between ²the power supply and the Y1 wire connection of the second terminal block 752, ²and the Y2 wire ²relay 758 may be electrically disposed between the power supply and the Y2 ²wire connection of²the second terminal block 752. Thus, when the Y1 wire relay 757 and the Y2 ²wire relay 758 are²closed, 24 volt A / C power may be delivered from the A2L control board 750 to ²the indoor control ²board 726 via the first terminal block 751, which signals the indoor control ²board 726 to run the ²cooling system's first and second stages, respectively. Further, when the Y1 ²wire relay 757 and ²Y2 wire relay 758 are open, no signal is sent along the Y1 or Y2 wires to the ²indoor control board²726, and thus, the cooling system is powered off. Additionally, as depicted in ²FIG. 7, in one or²more embodiments, the default states for the Y1 wire relay 757 and the Y2 wire ²relay 758 are to ²be closed.²Further, in one or more embodiments, the alarm relay 759 may be electrically ²disposed ²between the power supply and an alarm (not shown), which includes, in part, ²the buzzer 762 and²the LED 763. Thus, when the alarm relay 759 is closed, 24 volt A / C power may ²be delivered to²the alarm on the A2L control board 750, which powers at least the buzzer 762 ²and the LED 763 ²on. Further, when the alarm relay 759 is open, no power is delivered to the ²alarm on the A2L ²control board and it remains powered off Additionally, as depicted in FIG. 7, ²in one or more ²embodiments, the default state for the alarm relay 759 is to be closed.²49²CA 03206259 2023- 7- 24²<DP=50>²WO 2022 / 165377 ² PCT / US2022 / 014623²Furthermore, in one or more embodiments, the dry contact relay 764 may be ²electrically²disposed between the power supply and a ventilator (not shown) if the HVAC ²system 700 includes ²a ventilator, which is electrically coupled to the A2L control board 750 by ²way of the first and ²second ventilator contact points 765a and 765b. Thus, when the dry contact ²relay 764 is closed, 24 ²volt A / C power may be delivered to the ventilator, which powers the ventilator ²on. Further, when²the dry contact relay 764 is open, no power is delivered to the ventilator and ²it remains powered²off. Additionally, as depicted in FIG. 7, in one or more embodiments, the ²default state for the dry ²contact relay 764 is to be closed.²Additionally, in one or more embodiments, the outdoor unit relay 766 may be ²electrically ²disposed between the power supply and an outdoor unit contact point 767. In ²one or more²embodiments, the outdoor relay 780 may be electrically coupled to the A2L ²control board 750 by²way of the outdoor unit contact point 767. Thus, when the outdoor unit relay ²766 is closed, 24 volt ²A / C power may be delivered to the outdoor relay 780 causing it to open, thus ²opening the high ²pressure switch 790 and shutting off the outdoor unit 730. Further, when the ²outdoor unit relay ²766 is open, no power is delivered to the outdoor relay 780 and the outdoor ²unit 730 continues to²operate. Additionally, as depicted in FIG. 7, in one or more embodiments, the ²default state for the²outdoor unit relay 766 is to be closed.²Further, in one or more embodiments, once the system is turned on, the A2L ²control board ²750 may be configured to open all relays except for the R wire relay 753, ²which may be configured ²to be closed so as to provide the 24 volt A / C power to the thermostat 740 and ²power the thermostat²740 on. Furthermore, as discussed above, in one or more embodiments, the A2L ²control board 750²may be configured to act as a passthrough for any signals the thermostat sends ²during operation of ²the system. By way of example only, if the HVAC system 700 is required to cool ²the inside of a ²building, the thermostat may send signals along both the G and Y1 wires to the ²A2L control board ²750. The A2L control board 750 may be configured to receive those signals and ²correspondingly²close the G wire relay 754 and the Y1 wire relay 757 such that a 24 volt A / C ²signal may be passed² CA 03206259 2023- 7- 24²<DP=51>²WO 2022 / 165377 ² PCT / US2022 / 014623²to the indoor control board 726 along the G wire and the Y1 wire. Once ²received, the indoor control²board 726 may be configured to turn on the blower motor 723 and run the ²cooling system as is ²called for by a signal on the G wire and Y1 wire.²Further, in one or more embodiments, the power supply may be coupled to the ²first sensor ²connector 760 and the second sensor connector 761, separately. Thus, in one or ²more²embodiments, the A2L control board 750 may separately test one or more A2L ²sensors 770 before²closing the R wire relay 753 and powering up the thermostat 740. This allows ²for the A2L control ²board 750 to make sure that the sensors 770 are working properly and there are ²no A2L refrigerant ²leaks before beginning the system. While two separate sensor connectors are ²depicted, one of ²ordinary skill in the art would understand that the A2L control board may ²instead include a sensor²signal-in contact and a sensor signal-out contact and the one or more sensors ²may be run in series²instead of in parallel.²Thus, when the A2L control board 750 receives a signal from the A2L sensor 770 ²that there ²is an A2L refrigerant leak, the A2L control board 750 may be configured to ²carry out the required ²safety measures required by A2L safety standards. More specifically, in one or ²more embodiments,²if a leak is detected, the A2L control board 750 may be configured to cut off ²power to the²thermostat 740 by opening the R wire relay 753 and to cause the outdoor unit ²730 to turn off by ²closing the outdoor unit relay 766. Further, if a leak is detected, the A2L ²control board 750 may ²be configured to cut off power to all parts of the indoor unit 720 except the ²blower motor 723 by ²opening at least the WI wire relay 755 and the W2 wire relay 756 and closing ²at least the G wire²relay 754. Opening the W1 wire relay 755 and the W2 wire relay 756 will ensure ²that all heating²functions are shut off, while closing the G wire relay 754 will ensure that ²the blower motor 723 is ²turned on. In one or more embodiments, the Y1 wire relay 757 and the Y2 wire ²relay 758 may also ²be closed as cutting power to the outdoor unit 730 ensures that all cooling ²functionality is shut off, ²but the signal on the Y1 and Y2 wire may cause the indoor control board 726 to ²turn up the speed²on the blower motor 723 so it blows more air, faster. Further, closing the ²outdoor unit relay 766 in²51²CA 03206259 2023- 7- 24²<DP=52>²WO 2022 / 165377 ² PCT / US2022 / 014623²response to an A2L refrigerant leak being detected causes power to be directly ²applied to the²outdoor relay 780. Directly applying power to the outdoor relay 780 causes the ²outdoor relay 780 ²to open. Furthermore, opening the outdoor relay 780 is configured to cause the ²high pressure ²switch 790 to open. Additionally, the outdoor unit 730 is configured to shut ²down completely if ²the high pressure switch 790 is opened. Thus, closing the outdoor unit relay ²766 is configured to²shut down the outdoor unit 730 completely. This allows the HVAC system 700 to ²meet the A2L²safety requirements within the requisite time after detection of an A2L ²refrigerant leak.²While FIG. 7 depicts one or more embodiments of the present invention that ²utilize an ²outdoor relay 780 and a high pressure switch 790 in order to shut off the ²outdoor unit in the event ²of an A2L refrigerant leak, one of ordinary skill in the art would understand ²that any means of²turning off the compressor of the outdoor unit would work to properly meet the ²A2L safety²requirements. By way of example, in one or more embodiments, the HVAC system ²may include ²an A2L control board that is electrically coupled to a contactor, where the ²contactor is configured ²to contact the outdoor control board such that the outdoor unit shuts off in ²the event of an A2L ²refrigerant leak being detected. Further, in other embodiments, the A2L ²control board may be²communicatively coupled to the outdoor control board by way of an RS-485 ²system ²communication such that the A2L control board can tell the outdoor control ²board to shut down ²the outdoor unit in the event of an A2L leak being detected. Furthermore, in ²one or more ²embodiments, the A2L control board may be electrically coupled to a relay, ²where the relay is ²disposed between the outdoor control board and the compressor of the outdoor ²unit such that when²the relay is opened, power from the outdoor control board does not reach the ²compressor, and the²compressor shuts down.²Further, while in one or more embodiments a 24 volt A / C signal is used by the ²A2L control ²board to communicate with the outdoor relay to shut down the outdoor unit, one ²of ordinary skill ²in the art would understand that, in one or more embodiments, the A2L control ²board may send²digital signals to the outdoor relay. One of ordinary skill in the art would ²understand that digital²52²CA 03206259 2023- 7- 24²<DP=53>²WO 2022 / 165377 ² PCT / US2022 / 014623²signals may also be used with a contactor or any other relay coupled to the ²outdoor control board²to shut down the outdoor unit. Furthermore, in one or more embodiments, the ²A2L control board ²may be wirelessly, communicatively coupled to the outdoor control board such ²that wireless ²signals may be used to turn off the outdoor unit.²Additionally, in one or more embodiments, if a leak is detected, the A2L ²control board 750²may close the alarm relay 759 and the dry contact relay 764. Closing the alarm ²relay 759 will cause²the alarm on the A2L control panel 750 to be powered on, which will include, ²at least, turning on ²the buzzer 762 and the LED 763 to give auditory and visual alerts that a leak ²has been detected. ²Further, if the HVAC system 700 includes a ventilator, closing the dry contact ²relay 764 will cause ²the ventilator to be powered on, which will aid in removing any concentrations ²of A2L refrigerant² leaked into the HVAC system 700.²Further, in one or more embodiments, if the A2L control board 750 fails, the ²relays all revert ²to their default state. As discussed above and as depicted in FIG. 7, in a ²default state, the G wire ²relay 754, the Y1 wire relay 757, the Y2 wire relay 758, the alarm relay 759, ²the dry contact relay ²764, and the outdoor unit relay 766 may be closed, while the R wire relay 753, ²the W1 wire relay²755, and the W2 wire relay 756 may be open. Thus, if the A2L control board 750 ²fails, the outdoor²unit 730 will be shut down by way of the opened high pressure switch, and the ²only signals the ²indoor unit 720 will receive and act on will cause the blower motor 723 to be ²turned on as fast as ²it can go. Additionally, if the A2L control board 750 fails, the alarm will be ²turned on and the ²ventilator will be turned on.²Referring now to FIG. 8, a flow chart of an embodiment of a method 800 of ²installing and²operating a communicating FIVAC system using an A2L refrigerant as described ²above with ²respect to FIG. 7, according to one or more embodiments, is illustrated. ²Beginning with an HVAC ²system 700 in which the indoor unit 720 has been disposed on an inside 711 of ²a building 710, the ²outdoor unit 730 has been disposed on an outside 712 of the building 710, the ²indoor control board²726 has been electrically coupled to the transformer 725 and a blower motor ²723 of the blower²53²CA 03206259 2023- 7- 24²<DP=54>²WO 2022 / 165377 ² PCT / US2022 / 014623²721, and the outdoor control board 731 has been communicatively coupled to the ²indoor control²board 726, the method 800 may include one or more of the following: (step 810) ²installing the ²A2L control board 750 and the A2L sensor 770 into the HVAC system 700, (step ²820) testing the ²A2L sensor 770, (step 830) beginning operation of the HVAC system 700, (step ²840) checking for ²A2L refrigerant leaks, and (step 850) performing safety measures upon ²detecting an A2L² refrigerant leak.²At step 810, an A2L control board 750 and an A2L sensor 770 may be installed ²into the ²HVAC system 700. Installation ofthe A2L control board 750 and the A2L sensor ²770 may include, ²at least, (step 811) physically coupling the A2L sensor 770 to the indoor ²evaporator coil 724 of ²the indoor unit 720, (step 812) electrically coupling the A2L sensor 770 to ²the A2L control board²750, (step 813) electrically coupling the A2L control board 750 to the indoor ²control board 726,²(step 814) electrically coupling the A2L control board 750 to outdoor control ²board 731. (step 815) ²electrically coupling the A2L control board 750 to the thermostat 740, and ²(step 816) turning on ²the A2L control board 750 and opening the G wire relay 754, the Y1 wire relay ²757, the Y2 wire ²relay 758, the alarm relay 759, the dry contact relay 764, and the outdoor ²unit relay 766.²In one or more embodiments, at step 811, the A2L sensor 770 may be disposed ²within the²indoor unit 720 such that it is adjacent or connected to the indoor evaporator ²coil 724 such that the ²A2L sensor 770 is able to detect an A2L refrigerant leak if one occurs. ²Further, at step 812, the ²A2L sensor 770 may be electrically coupled to the A2L control board 750 such ²that the A2L sensor ²770 and the A2L control board 750 have two-way communication between them. By ²way of²example, in one or more embodiments, an A2L sensor 770 may be electrically ²coupled to a first²sensor connector 757 of the A2L control board 750 by way of an RS-485 bus. One ²of ordinary ²skill in the art would appreciate that in other embodiments, any other ²electric coupling that allows ²for two-way communication between the A2L sensor 770 and the A2L control board ²750 may be ²used.²54²CA 03206259 2023- 7- 24²<DP=55>²WO 2022 / 165377 ² PCT / US2022 / 014623²At step 813, the A2L control board 750 may be electrically coupled to the ²indoor control²board 726. In one or more embodiments, R, C, G, Wl, W2, Yl, Y2, 0, and Dehum ²wires may be ²electrically coupled on one end to a terminal block within the indoor control ²board 726 and on the ²other end to the second terminal block 752 of the A2L control board 750. ²Further, at step 815, the ²A2L control board 750 may be electrically coupled to the thermostat 740. In ²one or more²embodiments, R, C, G, Wl, W2, Yl, Y2, 0, and Dehum wires may be electrically ²coupled on one²end to a terminal block within the thermostat 740 and on the other end to the ²first terminal block ²751 of the A2L control board 750. Thus, in one or more embodiments, the A2L ²control board 750 ²may be configured to receive control signals from the thermostat 740 and send ²those same control ²signals to the indoor control board 726. Further, in one or more embodiments, ²the A2L control²board 750 may be configured to provide power to the thermostat 740 by way of ²the R wire so as²to power on the thermostat 740. In one or more embodiments, the power provided ²to the thermostat ²740 by the A2L control board 750 is a 24 volt A / C power.²At step 814, the A2L control board 750 may be electrically coupled to the ²outdoor control ²board 731. in one or more embodiments, the high pressure switch 790 may be ²electrically coupled²to the outdoor control board 731 such that when the high pressure switch 790 ²opens, the outdoor²control board 731 shuts down. Further, the outdoor relay 780 may be ²electrically coupled to the ²high pressure switch 790 such that when the outdoor relay opens, the high ²pressure switch opens. ²Furthermore, the outdoor relay 780 may be electrically coupled to an outdoor ²unit contact point ²767 of the A2L control board 750 by way of a wire capable of carrying 24 volt ²A / C power. Thus,²by way of example, if outdoor unit relay 766 of the A2L control board 750 ²closes, a 24 volt A / C²signal will be provided to the outdoor relay 780 which causes the outdoor ²relay 780 to open, which ²causes the high pressure switch 790 to open, which shuts down the outdoor unit ²730, including the ²outdoor control board 731.²At step 816, the A2L control board 750 may be turned on, and the G wire relay ²754, the Y1²wire relay 757, the Y2 wire relay 758, the alarm relay 759, the dry contact ²relay 764, and the² CA 03206259 2023- 7- 24²<DP=56>²WO 2022 / 165377 ² PCT / US2022 / 014623²outdoor unit relay 766 may be opened. In one or more embodiments, when the A2L ²control board²750 is turned on, the relays are in the default state, which includes the G ²wire relay 754, the Y1 ²wire relay 757, the Y2 wire relay 758, the alarm relay 759, the dry contact ²relay 764, and the ²outdoor unit relay 766 being closed. Thus, in order to make sure signals are ²not unnecessarily ²provided to the indoor control board 726 to turn on the blower motor 723, the ²outdoor unit 730 is²not unnecessarily shut down by the high pressure switch, and the alarm and ²ventilator are not²unnecessarily run, in one or more embodiments, when the A2L control board 750 ²powers up, the ²A2L control board opens the G wire relay 754, the Y1 wire relay 757, the Y2 ²wire relay 758, the ²alarm relay 759, the dry contact relay 764, and the outdoor unit relay 766.²At step 820, the A2L sensor 770 may be tested to confirm that it is properly ²operational.²Once electrically coupled to the A2L control board 750, in one or more ²embodiments, the A2L²sensor 770 may perform an internal diagnostic check to make sure that the ²sensor is operating ²properly and may detect an A2L refrigerant leak. If the diagnostic check is ²successful, the A2L ²sensor 770 may communicate the successful diagnostic check to the A2L control ²board 750, which ²can begin operation of the HVAC system 700. If the A2L sensor 770 fails the ²diagnostic check,²the A2L sensor 770 will communicate the failed diagnostic check to the A2L ²control board 750,²which will remain in the default configuration, keeping the HVAC system 700 ²from operating ²until the A2L sensor is repaired or replaced.²At step 830, the A2L control board 750 may begin operation of the HVAC system ²700. In ²order to begin operation, in one or more embodiments, the A2L control board ²750 may close the²R wire relay 753 of the A2L control board 750. Closing the R wire relay 753 ²allows for the 24 volt²A / C power of the A2L control board 750 to pass to the thermostat 740. Once ²power has been ²turned on for the thermostat 740, it may then be able to send signals to the ²indoor unit 720, through ²the A2L control board 750, and the HVAC system 700 may be fully operational.²At step 840, while the HVAC system is running, in one or more embodiments, the ²A2L²sensor 770 may check for A2L refrigerant leaks. The A2L sensor 770 may ²continuously check for²56²CA 03206259 2023- 7- 24²<DP=57>²WO 2022 / 165377 ² PCT / US2022 / 014623²A2L refrigerant leaks while the HVAC system 700 is running, such that if a ²check comes back²negative for an A2L refrigerant leak, the A2L sensor 770 repeats step 840. ²However, if the AL2 ²sensor 770 detects an A2L leak, then the A2L sensor 770 communicates the A2L ²refrigerant leak ²to the A2L control board and the HVAC system continues to step 850.²At step 850, the HVAC system 700, by way of the A2L control board 750, may ²perform²safety measures to eliminate the threat of the detected A2L refrigerant leak. ²Specifically, the²HVAC system 700 may (step 852) open the R wire relay 753, (step 853) close the ²G wire relay ²754, (step 854) open the W1 wire relay 755 and the W2 wire relay 756, (step ²855) close the Y1 ²wire relay 757 and the Y2 wire relay 758, (step 856) close the dry contact ²relay 764, (step 857) ²close the alarm relay 759, and (step 858) close the outdoor unit relay 766.²At step 852, opening the R wire relay 753 prevents the A2L control board 750 ²from²distributing the 24 volt A / C power to the thermostat 740. Removing the 24 volt ²A / C power from ²the thermostat 740 ensures that only the signals passed from the A2L control ²board 750 may reach ²the indoor control board 726 and thus, the safety measures may be implemented ²by the HVAC ²system 700. Additionally, at step 853, closing the G wire relay 754 causes the ²A2L control board²750 to send a 24 volt A / C power along the G wire to the inside control board ²726, which starts the²blower motor 723 when it receives the signal along the G wire. Further, at ²step 854, opening the ²W1 wire relay 755 and the W2 wire relay 756 ensures that no signal is sent to ²the indoor control ²board 726 and thus, heating operations are not run while the system is ²experiencing a refrigerant ²leak. Furthermore, at step 855, closing the Yl wire relay 757 and the Y2 wire ²relay 758 causes the²A2L control board 750 to send a 24 volt A / C power along the Y1 and Y2 wires to ²the indoor²control board 726. The indoor control board 726 interprets the signals along ²the Y1 and Y2 wires ²to call for first and second stage cooling operations, but because the ²compressor in the outdoor ²unit 730 is also being powered off in this step as discussed below, the only ²effect is that the indoor ²control board 726 runs the blower motor 732 at its highest level. ²Additionally, at step 858, closing²the outdoor unit relay 766 causes a 24 volt A / C signal to travel to the ²outdoor relay 780, which²57²CA 03206259 2023- 7- 24²<DP=58>²WO 2022 / 165377 ² PCT / US2022 / 014623²causes the outdoor relay 780 to open, which causes the high pressure switch ²790 to open, which²causes the outdoor unit 730 to shut down completely.²Further, at step 856, closing the dry contact relay 764 causes the 24 volt A / C ²power from the ²A2L control board 750 to power an attached ventilator on if the HVAC system ²700 includes a ²ventilator. Additionally, at step 857, closing the alarm relay 759 causes the ²24 volt A / C power²from the A2L control board 750 to power the alarm on, which includes, at ²least, powering on visual²and auditory alarms in the form of the buzzer 762 and the LED 763.²Further, while listed as separate steps, one of ordinary skill would ²appreciate that in one or ²more embodiments, steps 852-858 may take place in any order, or in other ²embodiments, steps ²852-858 may occur simultaneously. Additionally, one of ordinary skill in the ²art would appreciate²that all steps 852-858 may be completed within the requisite time after ²detection of an A2L²refrigerant leak as required by A2L safety standards.²Thus, in one or more embodiments, in response to a communication from the A2L ²sensor ²770 that an A2L refrigerant leak has been detected, the A2L control board 750 ²may turn off the ²outdoor unit 730, turn on a ventilator if the HVAC system 700 has one, turn on ²visual and auditory²alarms that an A2L refrigerant has been detected, and ensure that the only ²signals the indoor unit²720 will receive and act on will cause the blower motor 723 to be turned on as ²fast as it can go. ²While the method 800 is described with respect to an HVAC system 700 including ²a single ²A2L sensor 770, one of ordinary skill in the art, would understand that any ²number of sensors may ²be used in the system and the method may include electrically coupling the ²further sensors to the²control board, testing the further sensors, and communicating with the further ²sensors as the further²sensors check for A2L refrigerant leaks.²Referring now to FIG. 9, an illustrative configuration of A2L sensors for use ²in HVAC ²systems using an A2L refrigerant, according to one or more embodiments is ²shown. In one or more ²embodiments, an HVAC system 900 may include, in part, an A2L control board 950 ²and one or²more A2L sensors 970a, 970b, 970c. Further, as discussed above with respect to ²FIGs. 1, 3, 5, and²58²CA 03206259 2023- 7- 24²<DP=59>²WO 2022 / 165377 ² PCT / US2022 / 014623²7, the A2L sensors 970a, 970b, 970c may be electrically coupled to the A2L ²control board 950,²such that the A2L sensors 970a, 970b, 970c may communicate an A2L refrigerant ²leak to the A2L ²control board 950 if one is detected. Further, in one or more embodiments, an ²RS-485 4 wire ²harness may be used to connect, at least, the first A2L sensor 970a to a first ²sensor connector 957 ²of the A2L control board 950. Further, while an RS-485 connection may used, ²one of ordinary²skill in the art would understand that any method of communicatively and ²electrically coupling the²A2L sensors to the A2L control board may be used. Additionally, in one or more ²embodiments, a ²feedback wire may be used to electrically couple a last A2L sensor 970c to a ²second sensor ²connector 958 of the A2L control board 950.²While each A2L sensor 970a, 970b, 970c and the A2L control board 950 are ²depicted as²being electrically and communicatively coupled to each other by way of a wired ²connection, one²of ordinary skill in the art would understand that each A2L sensor 970a, 970b, ²970c and the A2L ²control board 950 may just be communicatively coupled wirelessly. In one or ²more embodiments, ²each A2L sensor 970a, 970b, 970c and the A2L control board 950 may be ²communicatively ²coupled by any wireless means, such as Wi-Fi or Bluetooth.²In one or more embodiments, each of the A2L sensors 970a, 970b, 970c may ²include sensing²components 971, a bus connector input 972, a bus connector output 973, a ²sensor relay 974, and a ²sensor feedback port 975. The sensing components 971 may be configured to ²detect an A2L gas ²in the air and report the level detected. Additionally, the sensing components ²971 may be ²configured to run internal diagnostic checks to make sure that the sensor is ²still operational.²Further, the bus connector input 972 and the bus connector output 973 may be ²physical²connectors through which the sensor may be communicatively coupled to another ²sensor or the ²A2L control board 950. By way of example, on the first sensor 970a, the bus ²connector input 972 ²may be where an RS-485 4 wire harness is connected to the first A2L sensor ²970a such that the ²first A2L sensor 970a is electrically coupled to the A2L control board 950. ²Also, by way of²example, a bus connector output 973 of the first A2L sensor 970a may be where ²another RS-485²59²CA 03206259 2023- 7- 24²<DP=60>²WO 2022 / 165377 ² PCT / US2022 / 014623²4 wire harness is connected to the first A2L sensor 970a such that the first ²A2L sensor 970a is²electrically coupled to the second A2L sensor 970b.²Furthermore, in one or more embodiments, each A2L sensor may include a sensor ²relay 974. ²The sensor relay 974 may be electrically disposed between the bus connector ²input 972 and the ²bus connector output 973 such that when the sensor relay 974 is open, power is ²blocked from²travelling from the bus connector input 972 to the bus connector output 973. ²Thus, when the sensor²relay 974 is closed, power may travel from the bus connector input 972 to the ²bus connector output²973 and then to whatever is electrically coupled to the bus connector output ²973. In one or more ²embodiments, the default position of the sensor relay 974 may be open. ²Further, in one or more ²embodiments, the sensor relay 974 may be configured to open if the sensor ²fails a diagnostic check.²Thus, in one or more embodiments, the A2L control board 950 may learn that a ²sensor has failed²by way of a loss of signal from the feedback wire coupled to a last A2L sensor ²970e, and then the ²A2L control board may respond by turning off the functionality of the HVAC ²system 900. ²Additionally, in one or more embodiments, each A2L sensor may include a sensor ²feedback ²port 975. In one or more embodiments, the sensor feedback port 975 may be used ²to send sensor²feedback by way of a feedback wire. More specifically, in one or more ²embodiments, the signal,²which may be analog or digital and wired or wireless, that is sent back to the ²A2L control board ²950 by way of the sensor feedback port 975 may indicate that all sensors on ²the network have ²successfully completed their internal checks, are functioning properly, and ²there are no more ²sensors in the chain. The sensor feedback port 975 may be disposed on the ²sensor such that the²sensor relay 974 is electrically disposed between the sensor feedback port 975 ²and the bus²connector input 972. Thus, when the sensor relay 974 is open, power is blocked ²from travelling ²from the bus connector input 972 to the sensor feedback port 975. Further, ²when the sensor relay²974 is closed, power may travel from the bus connector input 972 to the sensor ²feedback port 975 ²and then to whatever is electrically coupled to the sensor feedback port 975.² CA 03206259 2023- 7- 24²<DP=61>²WO 2022 / 165377 ² PCT / US2022 / 014623²In one or more embodiments, as shown in FIG. 9, the first A2L sensor 970a, the ²second A2L²sensor 970b, and the last A2L sensor 970c may be connected in series and ²electrically coupled to ²the A2L control board 950. By way of example, the A2L control board 950 may be ²directly ²electrically coupled to the first A2L sensor by way of an RS-485 4 wire ²harness coupled between ²the first sensor connector 957 and the bus connector input 972 of the first ²A2L sensor 970a.²Further, the first A2L sensor 970a may be directly coupled to the second A2L ²sensor 970b by way²of an RS-485 4 wire harness coupled between the bus connector output 973 of ²the first A2L sensor ²970a and the bus connector input 972 of the second A2L sensor 970b. ²Furthermore, the second ²A2L sensor 970b may be directly coupled to the last A2L sensor 970c by way of ²an RS-485 4 wire ²harness coupled between the bus connector output 973 of the second A2L sensor ²970b and the bus²connector input 972 of the last A2L sensor 970c. Additionally, the last A2L ²sensor 970c may be²directly coupled to the A2L control board 950 by way of a feedback wire ²coupled between the ²sensor feedback port 975 of the last A2L sensor 970c and the second sensor ²connector 958 of the ²A2L control board.²One of ordinary skill in the art, using common sense, would understand that ²the²configuration of A2L sensors 970a, 97013, 970c as described above with respect ²to FIG. 9 may be²utilized in any of the HVAC systems 100, 300, 500, 700 described above with ²respect to FIGs. 1-²8. Further, while only one sensor architecture is shown in FIG. 9, one of ²ordinary skill in the art, ²using common sense, would understand that any A2L sensors may be used. ²Furthermore, one of ²ordinary skill in the art would understand that the configuration of sensors ²as shown in FIG. 9²works with any A2L sensor that has a power input and a power output separated ²by any type of²switch that prevents power from reaching the power output until the sensor has ²passed internal ²diagnostics. Additionally, while the sensor architecture is described as using ²an RS-485 4 wire ²harness in a number of locations, one of ordinary skill in the art would ²understand that any form ²of connecting the sensors and the A2L control board that allows for two-way ²communication may²be used, whether digital or analog and wired or wireless. Further, while three ²sensors are shown²61²CA 03206259 2023- 7- 24²<DP=62>²WO 2022 / 165377 ² PCT / US2022 / 014623²in FIG. 9, one of ordinary skill in the art would understand that two sensors ²may be used in series²in the same manner described above, or a single sensor may be used instead.²Referring now to FIG. 10, a flow chart of a method of installing and testing a ²configuration ²of A2L sensors as described above with regard to FIG. 9 for an HVAC system ²using an A2L ²refrigerant, according to one or more embodiments, is illustrated. The method ²1000 may include²one or more of the following: (step 1010) disposing the A2L sensors 970a, ²970b, 970c within the²HVAC system 900; (step 1020) connect the A2L sensors 970a, 970b, 970c to the ²A2L control ²board 950; (step 1030) power each of the A2L sensors 970a, 970b, 970c on and ²run internal ²diagnostics; (step 1040) send confirmation to the A2L control board 950 that ²the A2L sensors are ²all installed and functioning properly.²At step 1010, each of the A2L sensors 970a, 970b, 970c may be disposed within ²the HVAC²system 900 as necessary to make sure that any A2L refrigerant leaks that may ²occur are detected ²almost immediately. By way of example, disposing the A2L sensors 970a, 970b, ²970c within the ²LIVAC system 900 may include at least, finding a distinct place for each A2L ²sensor 970a, 970b, ²970c that is adjacent to an evaporator coil of the indoor unit of the HVAC ²system 900 and coupling² each sensor 970a, 970b, 970c thereto.²Further, at step 1020, the A2L sensors 970a, 970b, 970c may be coupled to the ²A2L control ²board 950. Coupling the A2L sensors 970a, 970b, 970c to the A2L control board ²950 may include, ²at least: (step 1021) connecting the first A2L sensor 970a to the A2L control ²board 950; (step ²1022) connecting the second A2L sensor 970b to the first A2L sensor 970a; ²(step 1023) connecting²the last A2L sensor 970c to the second A2L sensor 97013; and (step 1024) ²connecting the last A2L²sensor 970c to the A2L control board 950.²At step 1021, the first A2L sensor 970a may be connected to the A2L control ²board 950. In ²one or more embodiments, connecting the first A2L sensor 970a to the A2L ²control board 950 ²may include attaching an RS-485 bus on one end to a first sensor connector 957 ²of the A2L control²board 950 and on the other end to a bus connector input 972 of the first A2L ²sensor 970a. Further,²62²CA 03206259 2023- 7- 24²<DP=63>²WO 2022 / 165377 ² PCT / US2022 / 014623²at step 1022, the first A2L sensor 970a may be connected to the second A2L ²sensor 970b. In one²or more embodiments, connecting the first A2L sensor 970a to the second A2L ²sensor 970b may ²include attaching an RS-485 bus on one end to a bus connector output 973 of ²the first A2L sensor ²970a and on the other end to a bus connector input 972 of the second A2L ²sensor 970b. ²Furthermore, at step 1023, the second A2L sensor 970b may be connected to the ²last A2L sensor²970c. In one or more embodiments, connecting the second A2L sensor 970b to the ²last A2L sensor²970c may include attaching an RS-485 bus on one end to a bus connector output ²973 of the second ²A2L sensor 970b and on the other end to a bus connector input 972 of the last ²A2L sensor 970c. ²Additionally, at step 1024, the last A2L sensor 970c may be connected to the ²A2L control board ²950. In one or more embodiments, connecting the last A2L sensor 970c to the ²A2L control board²950 may include attaching a feedback line on one end to a sensor feedback port ²975 of the last²A2L sensor 970c and on the other end to a second sensor connector 958 of the ²A2L control board ²950.²At step 1030, each of the A2L sensors 970a, 970b, 970c may be powered on and ²run through ²internal diagnostics. Powering on and testing each of the A2L sensors may ²include, at least: the²first A2L sensor 970a (step 1031) receiving power from the A2L control board ²950, (step 1032)²running an internal diagnostic test, and, if it passed the internal diagnostic ²test, (step 1033) closing ²sensor relay 974 of the first A2L sensor 970a; the second A2L sensor 970b ²(step 1034) receiving ²power from the first A2L sensor 970a, (step 1035) running an internal ²diagnostic test, and, if it ²passed the internal diagnostic test. (step 1036) closing sensor relay 974 of ²the second A2L sensor²970b; the last A2L sensor 970c (step 1037) receiving power from the second A2L ²sensor 970b,²(step 1038) running an intemal diagnostic test, and, if it passed the internal ²diagnostic test, (step ²1039) closing sensor relay 974 of the last A2L sensor 970c.²At step 1031, once the A2L sensors 970a, 970b, 970c are physically coupled to ²the A2L ²control board 950, the A2L control board 950 may send power to the first A2L ²sensor 970a, which²the first A2L sensor 970a may receive and use to power on. Further, at step ²1032, the first A2L²63²CA 03206259 2023- 7- 24²<DP=64>²WO 2022 / 165377 ² PCT / US2022 / 014623²sensor 970a may run an internal diagnostic check of the sensing components ²971, in which the²first A2L sensor 970a confirms whether the sensing components 971 are ²functioning properly. ²Additionally, at step 1033, if the first A2L sensor 970a passed the internal ²diagnostic check, then ²the first sensor 970a may close the sensor relay 974, which allows power to ²travel from the bus ²connector input 972 to the bus connector output 973 and the sensor feedback ²port 975.²At step 1034, once the first A2L sensor 970a closes its sensor relay 974, the ²first A2L sensor²970a may send power to the second A2L sensor 970b, which the second A2L sensor ²970b may ²receive and use to power on. Further, at step 1035, the second A2L sensor 970b ²may run an internal ²diagnostic check of the sensing components 971, in which the second A2L sensor ²970b confirms ²whether the sensing components 971 are functioning properly. Additionally, at ²step 1036, if the²second A2L sensor 970b passed the internal diagnostic check, then the second ²sensor 970b may²close the sensor relay 974. which allows power to travel from the bus ²connector input 972 to the ²bus connector output 973 and the sensor feedback port 975.²At step 1037, once the second A2L sensor 970b closes its sensor relay 974, the ²second A2L ²sensor 970b may send power to the last A2L sensor 970c, which the last A2L ²sensor 970c may²receive and use to power on. Further, at step 1038, the last A2L sensor 970c ²may run an internal²diagnostic check of the sensing components 971, in which the last A2L sensor ²970c confirms ²whether the sensing components 971 are functioning properly. Additionally, at ²step 1039, if the ²last A2L sensor 970c passed the internal diagnostic check, then the last ²sensor 970c may close the ²sensor relay 974, which allows power to travel from the bus connector input ²972 to the bus² connector output 973 and the sensor feedback port 975.²At step 1040, once the last A2L sensor 970c closes its sensor relay 974, the ²last A2L sensor ²970c may send power to the A2L control board 950 by way of the feedback line ²connected between ²the sensor feedback port 975 of the last A2L sensor 970c and the second sensor ²connector 958 of ²the A2L control board 950. Receiving this feedback signal from the last A2L ²sensor 970c notifies²the A2L control board 950 that all sensors on the network have successfully ²completed their²64²CA 03206259 2023- 7- 24²<DP=65>²WO 2022 / 165377 ² PCT / US2022 / 014623²internal checks, are functioning properly, and there are no more sensors in ²the chain that need to²be connected and tested. This is so, because, at any point in the chain of ²sensors, if there is a failure ²of a sensor, the sensor relay will not close, and thus, all subsequent sensors ²in the chain and the ²feedback port of the last sensor in the chain will not receive power and the ²A2L control board will ²not receive the feedback it needs.²One of ordinary skill in the art, using common sense, would understand that ²the method 1000²of installation and testing of A2L sensors 970a, 970b, 970c as described above ²with respect to FIG. ²10 may be utilized in any of the methods 200, 400, 600, 800 described above ²with respect to FIGs. ²1-8. Further, while only one sensor architecture is described by the method of ²FIG. 10, one of ²ordinary skill in the art, using common sense, would understand that any A2L ²sensors may be²used. Furthermore, one of ordinary skill in the art would understand that the ²configuration of²sensors as described in the method 1000 of FIG. 10 works with any A2L sensor ²that has a power ²input and a power output separated by any type of switch that prevents power ²from reaching the ²power output until the sensor has passed internal diagnostics. Additionally, ²while the sensor ²architecture is described as using an RS-485 4 wire harness in a number of ²locations, one of²ordinary skill in the art would understand that any form of connecting the ²sensors and the A2L²control board that allows for two-way communication may be used, whether ²digital or analog and ²wired or wireless. Further, while the installation and testing of three ²sensors is described by method ²1000, one of ordinary skill in the art would understand that two sensors may ²be used in series in ²the same manner described above, or a single sensor may be used instead.²Herein, -or" is inclusive and not exclusive, unless expressly indicated ²otherwise or indicated²otherwise by context. Therefore, herein, "A or B" means "A, B, or both," ²unless expressly ²indicated otherwise or indicated otherwise by context. Moreover, "and" is both ²joint and several, ²unless expressly indicated otherwise or indicated otherwise by context. ²Therefore, herein, "A and ²B" means "A and B, jointly or severally," unless expressly indicated otherwise ²or indicated² otherwise by context.² CA 03206259 2023- 7- 24²<DP=66>²WO 2022 / 165377 ² PCT / US2022 / 014623²The scope of this disclosure encompasses all changes, substitutions, ²variations, alterations,²and modifications to the example embodiments described or illustrated herein ²that a person having ²ordinary skill in the art would comprehend. The scope of this disclosure is ²not limited to the ²example embodiments described or illustrated herein. Moreover, although this ²disclosure ²describes and illustrates respective embodiments herein as including ²particular components,²elements, feature, functions, operations, or steps, any of these embodiments ²may include any²combination or permutation of any of the components, elements, features, ²functions, operations, ²or steps described or illustrated anywhere herein that a person having ²ordinary skill in the art would ²comprehend. Furthermore, reference in the appended claims to an apparatus or ²system or a ²component of an apparatus or system being adapted to, arranged to, capable of, ²configured to,²enabled to, operable to, or operative to perform a particular function ²encompasses that apparatus,²system, component, whether or not it or that particular function is activated, ²turned on, or ²unlocked, as long as that apparatus, system, or component is so adapted, ²arranged, capable, ²configured, enabled, operable, or operative.²66²CA 03206259 2023- 7- 24²

Claims

<DP=1>²WO 2022 / 165377 ² PCT / US2022 / 014623² WHAT IS CLAIMED IS:²1. A system for detecting an amount of A2L refrigerant in an air ²temperature controller using ²an A2L refrigerant, the system comprising:²an A2L control board; and²a first A2L scnsor and a second A2L sensor electrically coupled to thc A2L ²control board,²wherein each of the first A2L sensor and the second A2L sensor include:²sensing components configured to detect the amount of A2L refrigerant,²wherein the first A2L sensor and the second A2L sensor are coupled in series ²to the A2L²control board.²2. The system of claim 1, wherein each of the first A2L sensor and the ²second A2L sensor²further include:²a bus connector input;²a bus connector output;²a sensor relay electrically disposed between the bus connector input and the ²bus connector²output; and²a sensor feedback port electrically disposed between the bus connector input ²and the sensor²feedback port.²3. The system of claim 2, wherein:²the A2L control board includes a first sensor connector and a second sensor ²connector;²the bus connector input of the first A2L sensor is electrically and ²communicatively coupled²to the first sensor connector of the A2L control board;²the bus connector output of the first A2L sensor is electrically and ²communicatively²coupled to the bus connector input of the second A2L sensor; and²the sensor feedback port of the second A2L sensor is electrically coupled to ²the second²sensor connector of thc A2L control board.²67²CA 03206259 2023- 7- 24²<DP=2>²WO 2022 / 165377 ² PCT / US2022 / 014623² 4. The system of claim 3, wherein:²the bus connector input of the first A2L sensor is electrically and ²communicatively coupled ²to the first sensor connector of the A2L control board by a first RS-485 ²connection;²the bus connector output of the first A2L sensor is electrically and ²communicatively ²coupled to the bus connector input of thc second A2L sensor by a second RS-485 ²connection; and²the sensor feedback port of the second A2L sensor is electrically coupled to ²the second²sensor connector of the A2L control board by a 24 volt alternating current ²connection.²5. The system of claim 3, wherein the system further comprises:²an indoor unit disposed inside a building, the indoor unit having a heat ²exchanger that uses²the A2L refrigerant;²a blower disposed within and electrically coupled to the indoor unit; and²an outdoor unit disposed outside the building, wherein the outdoor unit is ²electrically²coupled to the indoor unit,²wherein the A2L control board is electrically coupled to the indoor unit and ²the blower.²6. The system of claim 2, wherein:²a first default status of the sensor relay of the first A2L sensor is open;²a second default status of the sensor relay of the second A2L sensor is open;²7. The system of claim 6, wherein:²the first A2L sensor is configured to close the sensor relay of the first A2L ²sensor if the²first A2L sensor passes an internal self-diagnostic test; and²the second A2L sensor is configured to close the sensor relay of the second ²A2L sensor if²the second A2L sensor passes an internal self-diagnostic test.²8. The system of claim 7, wherein the second A2L sensor does not receive ²power to turn on ²until the first A2L sensor passes the internal self-diagnostic test and the ²sensor relay of the first ²A2L sensor is closed.² 68²CA 03206259 2023- 7- 24²<DP=3>²WO 2022 / 165377 ² PCT / US2022 / 014623² 9. The system of claim 8, wherein:²the A2L control board is configured to turn on the air temperature controller ²when it ²receives a feedback signal from the sensor feedback port of the second A2L ²sensor; and²the sensor feedback port of the second A2L sensor does not receive power to ²send the ²feedback signal until the second A2L scnsor passes the internal self-²diagnostic test and the sensor²relay of the second A2L sensor is closed.²10. The system of claim 1, wherein the first A2L sensor is configured to ²communicate with ²the A2L control board if the first A2L sensor detects that the amount of A2L ²refrigerant exceeds ²a leak threshold, and wherein the second A2L sensor is configured to ²communicate with the A2L ²control board if the second A2L sensor detects that the amount of leaked A2L ²refrigerant exceeds²a leak threshold.²11. A method of installing a configuration of A2L sensors in an air ²temperature controller ²using an A2L refrigerant, the method comprising:²disposing an A2L control board, a first A2L sensor, and a second A2L sensor ²into an air ²temperature controller;²electrically coupling the first A2L sensor to the A2L control board; and²electrically coupling the second A2L sensor to the A2L control board,²wherein the first A2L sensor and the second A2L sensor each include sensing ²components²configured to detect an amount of A2L refrigerant, and wherein the first A2L ²sensor and the second²A2L sensor are coupled in series to the A2L control board.² 69²CA 03206259 2023- 7- 24²<DP=4>²WO 2022 / 165377 ² PCT / US2022 / 014623² 12. The method of claim 11, wherein:²each of the first A2L sensor and the second A2L sensor further include:²a bus connector input;²a bus connector output;²a sensor relay electrically disposed between the bus connector input and the ²bus²connector output; and²a sensor feedback port electrically disposed between the bus connector input ²and²the sensor feedback port; and²the A2L control board includes a first sensor connector and a second sensor ²connector.²13. The system of claim 12, further comprising:²electrically and communicatively coupling the bus connector input of the first ²A2L sensor²to the first sensor connector of the A2L control board;²electrically and communicatively coupling the bus connector output of the ²first A2L sensor²to the bus connector input of the second A2L sensor; and²electrically coupling the sensor feedback port of the second A2L sensor to the ²second²sensor connector of the A2L control board.²14. The system of claim 13, wherein:²electrically and communicatively coupling the bus connector input of the first ²A2L sensor ²to the first sensor connector of the A2L control board by a first RS-485 ²connection;²electrically and communicatively coupling the bus connector output of the ²first A2L sensor²to the bus connector input of the second A2L sensor by a second RS-485 ²connection; and²electrically coupling the sensor feedback port of the second A2L sensor to the ²second ²sensor connector of the A2L control board by a 24 volt alternating current ²connection.² CA 03206259 2023- 7- 24²<DP=5>²WO 2022 / 165377 ² PCT / US2022 / 014623²15. The system of claim 13, further comprising:²disposing an indoor unit inside a building, the indoor unit having a heat ²exchanger that uses ²the A2L refrigerant;²disposing a blower within the indoor unit and electrically coupling the blower ²to the indoor ²unit;²disposing an outdoor unit outside the building and electrically coupling the ²outdoor unit to²the indoor unit; and²electrically coupling the A2L control board to the indoor unit and to the ²blower.²16. The system of claim 12, wherein:²a first default status of the sensor relay of the first A2L sensor is open;²a second default status the sensor relay of the second A2L sensor is open;²17. The system of claim 16, further comprising:²running a first internal self-diagnostic test on the first A2L sensor;²closing the sensor relay of the first A2L sensor if the first A2L sensor ²passes the first²internal self-diagnostic test;²running a second internal self-diagnostic test on the second A2L sensor; and²closing the sensor relay of the second A2L sensor if the second A2L sensor ²passes the²second internal self-diagnostic test.²18. The system of claim 17, wherein the second A2L sensor does not receive ²power to turn on ²until the first A2L sensor passes the first internal self-diagnostic test and ²the sensor relay of the²first A2L sensor is closed.²71²CA 03206259 2023- 7- 24²<DP=6>²WO 2022 / 165377 ² PCT / US2022 / 014623² 19. The system of claim 18, further comprising:²Turning on the air temperature controller by the A2L control board when the ²A2L control ²board receives a feedback signal from the sensor feedback port of the second ²A2L sensor, wherein ²the A2L control board does not receive the feedback signal from the sensor ²feedback port of the ²second A2L sensor until the sccond A2L sensor passcs the sccond internal self-²diagnostic test and²the sensor relay of the second A2L sensor is closed.²20. The system of claim 11, wherein the first A2L sensor is ²configured to communicate with ²the A2L control board if the first A2L sensor detects the amount of A2L ²refrigerant exceeds a leak ²threshold, and wherein the second A2L sensor is configured to communicate with ²the A2L control ²board if the second A2L sensor detects the amount of A2L refrigerant exceeds a ²leak threshold.²72²CA 03206259 2023- 7- 24²