Patent Publication Number: US-11662110-B2

Title: Systems and methods for air temperature control including R-32 sensors

Description:
TECHNICAL FIELD 
     The present invention relates to heating, ventilation, and air-conditioning (HVAC) systems, and more particularly to HVAC systems using an American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) Standard 34 classified “A2L” refrigerant called R-32. 
     BACKGROUND 
     Modern residential and industrial buildings use HVAC systems to keep indoor spaces climate controlled. In general, HVAC systems circulate air over low-temperature or high-temperature sources and distribute the cooled or heated air throughout the building to adjust the indoor ambient air temperature. Modern HVAC systems have used the well-known physical principle that a fluid transitioning from gas to liquid releases heat, while a fluid transitioning from liquid to gas absorbs heat, in order to efficiently cool or heat the air before distribution. Typical HVAC systems circulate a fluid refrigerant through a closed loop of tubing, using compressors and other devices to manipulate the refrigerant and cause it to cycle between its liquid and gas phases. Generally, these phase transitions occur within the HVAC&#39;s evaporator and condensing coils, which are part of the closed loop and designed to transfer heat between the circulating refrigerant and flowing ambient air. 
     For a long time, HVAC systems used, and in some places continue to use, a chemical called R-12 or a chemical called R-22 as the refrigerant in the system. While R-12 and R-22 are both classified as “A1” refrigerants under ASHRAE Standard 34, which means they are non-flammable and have lower toxicity, they both posed great threats to the ozone and environment. R-22, while an improvement over R-12 in that it had a much lower ozone depletion potential (ODP) (0.05 for R-22 compared to 1.0 for R-12) and global warming potential (GWP) (1,760 for R-22 compared to 10,200 for R-12), still had adverse effects on the ozone and environment. Thus, in an attempt to solve the ozone depletion issue, the industry, with the help of regulations, began transitioning to the use of R-410A, which is another A1 refrigerant but with an ODP of 0. However, R-410A has a GWP (2,088) that is even higher than that of R-22. 
     Thus, in an attempt to solve the global warming issue created by the use of the above refrigerants, the industry has begun to move from the use of A1 refrigerants to those classified as A2L refrigerants, which means that the refrigerants are still low toxicity but instead of being non-flammable, they have very low flammability. Generally, these A2L refrigerants have much lower GWP than the A1 refrigerants currently and previously used while still having an ODP of 0 like R-410A. Some examples of viable A2L refrigerants include, but are not limited to, R-32 and R-454b, both of which have an ODP of 0 and a GWP of 675 and 466, respectively. However, this now means that HVAC systems incorporating these A2L refrigerants need to employ safety measures to make sure that the refrigerants do not ignite in case there is a leak of A2L refrigerant. Some of these safety requirements for systems using A2L refrigerants include turning on a blower in the HVAC system while shutting off all other components of the HVAC system within the requisite time after detection of an A2L refrigerant leak as required by A2L safety standards. Present HVAC systems are not only unable to achieve these requirements within the required time, but they are unable to detect A2L leaks. 
     SUMMARY 
     The present invention is directed to a system for detecting an amount of R-32 refrigerant in an air temperature controller using an R-32 refrigerant, and a method of installing a configuration of R-32 sensors in the air temperature controller using the R-32 refrigerant. The system includes an R-32 control board, a first R-32 sensor, and a second R-32 sensor. The first R-32 sensor and second R-32 sensor are coupled in series and electrically coupled to the R-32 control board. Further, each of the first R-32 sensor and the second R-32 sensor include sensing components configured to detect the amount of R-32 refrigerant. In one or more embodiments described herein, each of the first R-32 sensor and the second R-32 sensor include a sensor relay electrically disposed between a bus connector input and a bus connector output. Additionally, in one or more embodiments described herein, each of the first R-32 sensor and the second R-32 sensor run an internal self-diagnostic test, and if the sensor passes the internal self-diagnostic test, the sensor closes the sensor relay allowing power to pass through the sensor. 
     The method of installing the configuration of R-32 sensors in an air temperature controller using an R-32 refrigerant includes disposing the R-32 control board, the first R-32 sensor, and the second R-32 sensor into the air temperature controller. Further, the first R-32 sensor is electrically coupled to the R-32 control board and the second R-32 sensor is coupled to the R-32 control board. Additionally, the first R-32 sensor and the second R-32 sensor are coupled in series to the R-32 control board. In one or more embodiments described herein, each of the first R-32 sensor and the second R-32 sensor run an internal self-diagnostic test, and if the sensor passes the internal self-diagnostic test, the sensor closes its sensor relay allowing power to pass through the sensor. 
     The HVAC systems as disclosed herein provide components and architecture that allow for detection of leaks of R-32 refrigerant and for meeting the safety requirements within the required time. Additionally, within the HVAC systems, the components and architecture of the systems for detecting the amount of R-32 refrigerant as disclosed herein ensure that the system meets the safety requirements by ensuring that all R-32 sensors are operating properly while an HVAC system is running. Thus, a system for detecting the amount of R-32 refrigerant may be installed such that HVAC systems incorporating R-32 refrigerant operate safely while reducing the negative environmental impact caused by present HVAC systems. The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the invention, as illustrated in the accompanying drawings, wherein like reference numbers represent like parts of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
         FIG.  1    shows a non-communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  2    is a flow chart illustrating an embodiment of a method of operating a non-communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  3    shows a communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  4    is a flow chart illustrating an embodiment of a method of operating a communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  5    shows another non-communicating HVAC system using an A2L refrigerant, according to a second embodiment; 
         FIG.  6    is a flow chart illustrating another embodiment of a method of operating a non-communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  7    shows another communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  8    is a flow chart illustrating another embodiment of a method of operating a non-communicating HVAC system using an A2L refrigerant, according to one or more embodiments; 
         FIG.  9    is an illustrative configuration of A2L sensors for use in an HVAC system using an A2L refrigerant, according to one or more embodiments; and 
         FIG.  10    is a flow chart illustrating an embodiment of a method of installing and testing a configuration of A2L sensors for use in an illustrative configuration of A2L sensors for use in an HVAC system using an A2L refrigerant, according to one or more embodiments. 
     
    
    
     DESCRIPTION 
     This disclosure generally relates to non-communicating and communicating HVAC systems designed to incorporate the use of an A2L refrigerant and meet the safety standards imposed on systems using A2L refrigerants. While any ASHRAE Standard 34 classified “A2L” refrigerant may be used, in one or more embodiments, the A2L refrigerant may be R-32 refrigerant. R-32, also called difluoromethane, is an organic compound having a chemical formula of CH 2 F 2 . As discussed above, R-32 refrigerant has a GWP of 675 and an ODP of 0. In one or more embodiments, all references to “A2L” below may be specifically related to R-32. By way of example, throughout the specification, an A2L refrigerant may be R-32 refrigerant, an A2L sensor may be an R-32 sensor that is configured to detect amounts of R-32 refrigerant so as to detect an R-32 refrigerant leak, and an A2L control board may be a control board configured to work with R-32 sensors to enact safety measures if an R-32 refrigerant leak is detected. 
       FIG.  1    shows a non-communicating HVAC system using an A2L refrigerant, according to one or more embodiments. In one or more embodiments, an HVAC system  100  may be used to distribute cooled or heated air throughout a building  110  to adjust the ambient air temperature inside  111  of the building  110 . The HVAC system may include an indoor unit  120 , an outdoor unit  130 , a thermostat  140 , an A2L control board  150 , and an A2L sensor  170 . Generally, in one or more embodiments, the indoor unit  120  may be fluidly coupled to the outdoor unit  130  such that an A2L refrigerant may flow between the indoor unit  120  and the outdoor unit  130  to cool or heat air within the indoor unit  120 . Further, in one or more embodiments, both the indoor unit  120  and the outdoor unit  130  may be electrically coupled to the thermostat  140 . The thermostat  140  may be configured to use on/off-type signals for communication and control of the indoor unit  120  and the outdoor unit  130 . Furthermore, in one or more embodiments, the A2L control board  150  may be directly electrically coupled to the indoor unit  120  and the A2L sensor  170 . The A2L control board  150  may act as a passthrough for power to portions of the indoor unit  120 , the outdoor unit  130 , and the thermostat  140  and may be configured to block power from getting to certain parts of the indoor unit  120 , the outdoor unit  130 , and the thermostat  140  if there is an A2L refrigerant leak in the system. Additionally, an A2L sensor  170  may be physically disposed within the indoor unit  120  and electrically coupled to the A2L control board  150 . The A2L sensor  170  may be configured to send signals to the A2L control board  150  when an A2L refrigerant leak is detected. 
     In one or more embodiments, indoor unit  120  may be disposed on the inside  111  of the building  110 . The indoor unit  120  may be configured to distribute cooled or heated air to rooms on the inside  111  of the building  110 . The indoor unit  120  may be any type of HVAC system that includes a blower  121  and a heat exchanger  127  having an indoor evaporator coil  124 . Thus, in one or more embodiments, the indoor unit  120  may be either a furnace or an air handler, as both types of system include, at least, a blower and an indoor evaporator coil. Additionally, the indoor evaporator coil  124  may be disposed adjacent to the blower  121 , such that when the blower  121  blows air within the indoor unit  120 , the air is blown through the evaporator coil  124 . 
     Further, in one or more embodiments, the blower  121  may include a blower fan  122  and a blower motor  123 . By way of example, in one or more embodiments, the blower motor  123  may be constant torque motor, while in other embodiments, the blower motor  123  may be a permanent split capacitor (PSC) motor. The blower motor  123  may be mechanically coupled to the blower fan  122  such that when the blower motor  123  is turned on, the blower fan  122  is configured to spin and cause a movement of air out from the blower  121  and through the indoor evaporator coil  124 . The indoor evaporator coil  124  may be configured to receive the A2L refrigerant on the inside of the coil while air from the blower  121  is blown across the outside of the coil, which allows for heat to exchange either from the A2L refrigerant to the air or vice versa. The A2L refrigerant, after cooling or heating the air, may be cycled back to the outdoor unit  130 , where it will go through the reverse heat exchange process before returning to the indoor evaporator coil  124 . Additionally, indoor unit  120  is configured to distribute the air that is blown from the blower  121  and across the indoor evaporator coil  124  to the rooms on the inside  111  of the building  110  by way of the force of the blower  121 . 
     The indoor unit  120  may also include a transformer  125  and an indoor control board  126 . The transformer  125  may be directly electrically coupled to and configured to provide 24 volts A/C power to the A2L control board  150 . Further, the indoor control board  126  may be electrically coupled to the A2L control board  150  such that the indoor control board  126  may receive 24 volts A/C power indirectly from the transformer  125 . Additionally, the indoor control board  126  may be electrically coupled to, at least, the blower motor  123  and the thermostat  140 . In one or more embodiments, the transformer  125  may be configured to indirectly provide a 24 volt A/C power to both the blower motor  123  and the thermostat  140  by way of indoor control board  126  and the A2L control board  150 . In one or more embodiments, the blower motor has its own source of power. So, while the 24 volt A/C power that the blower motor receives does not power on the blower motor  123 , the 24 volt A/C signal is needed to turn the blower motor  123  on. By way of example only, in one or more embodiments, the indoor control board  126  may be configured to provide power to the thermostat  140 , the thermostat  140  may be configured to send a signal to the indoor control board  126  to turn on the blower motor  123 , and the indoor control board  126  may be configured to provide power to the blower motor  123  to turn it on. 
     Further, the outdoor unit  130  may be disposed on an outside  112  of the building  110  and be configured to use the outdoor environment to reheat or cool down the A2L refrigerant after it has been run through the indoor evaporator coil  124 . The outdoor unit  130  may include, but is not limited to, either a heat pump or an air conditioner. Whether the outdoor unit  130  is a heat pump or an air conditioner, the outdoor unit  130  may include a compressor (not shown), an outdoor coil (not shown), and an outdoor control board  131 . The outdoor unit  130  may be configured to receive power through the outdoor control board  131 , which itself is configured to receive power from the transformer  125  by way of the thermostat  140 , the indoor control board  126 , and the A2L control board  150 . By way of example only, in one or more embodiments, the outdoor control board  131  may be configured to receive power and control signals from the thermostat  140 , such that outdoor control board  131  may start the condenser after receiving a signal from the thermostat  140  to do so. 
     Still referring to  FIG.  1   , in one or more embodiments, the A2L sensor  170  may be configured to detect an A2L refrigerant leak and send a signal reporting as much. In one or more embodiments, the A2L sensor  170  may be configured to detect an A2L refrigerant leak by one of a number of methods, including, at least, by detecting an amount or a concentration of A2L refrigerant in the air that exceeds a leak threshold. The A2L sensor  170  may be electrically coupled to and communicate with the A2L control board  150 . In one or more embodiments, the A2L sensor  170  may be electrically coupled to the A2L control board  150  by way of a first sensor connector  157 . The A2L sensor  170  may be configured to communicate to the A2L control board  150  that the A2L sensor  170  is connected to the system and working properly. Additionally, when the A2L sensor  170  detects an A2L refrigerant leak, it may communicate the A2L refrigerant leak to the A2L control board  150 , which may be configured to receive the signal and perform the safety measures required by A2L safety standards. In one or more embodiments, the A2L sensor  170  and the A2L control board  150  may be electrically coupled by way of an RS-485 bus; however, one of ordinary skill in the art would understand that any type of electrical connection that allows the A2L sensor  170  to send a signal to the A2L control board  150  may be used. 
     While the A2L sensor  170  is depicted as being electrically and communicatively coupled to the A2L control board  150  by way of a wired connection, one of ordinary skill in the art would understand that the A2L sensor  170  may just be communicatively coupled to the A2L control board  150  wirelessly. In one or more embodiments, the A2L sensor  170  may be communicatively coupled to the A2L control board  150  by any wireless means, such as Wi-Fi or Bluetooth. 
     Further, in one or more embodiments, the A2L sensor  170  may be disposed within the indoor unit  120  so that it may detect an A2L refrigerant leak that occurs within the indoor evaporator coil  124  of the HVAC system  100 . As depicted, in one or more embodiments, the A2L sensor  170  may be disposed directly against the indoor evaporator coil to minimize the time it takes for the A2L sensor  170  to detect an A2L refrigerant leak. Further, while the A2L sensor  170  is depicted within the indoor unit  120 , one or ordinary skill in the art would understand that the A2L sensor  170  may instead be disposed within the outdoor unit  130 . Further, while a single sensor is depicted, one of ordinary skill in the art would understand that multiple sensors may be incorporated into the HVAC system to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. For example, one of ordinary skill in the art would understand that the HVAC system may include two A2L sensors, with both A2L sensors disposed within the indoor unit, both A2L sensors disposed within the outdoor unit, or one A2L sensor disposed within each of the indoor unit and the outdoor unit. Thus, one of ordinary skill in the art would understand that in one or more embodiments, a plurality of A2L sensors may be disposed within the HVAC system with one or more A2L sensors disposed within the indoor unit and/or one or more A2L sensors disposed within the outdoor unit as may be determined necessary to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. 
     Additionally, referring to  FIG.  1   , in one or more embodiments, the A2L control board  150  may be disposed inside of the indoor unit  120 . However, one of ordinary skill in the art would understand that, in one or more embodiments, the A2L control board  150  may be disposed outside of the indoor unit  120  and either connected to the indoor unit  120  or adjacent to the indoor unit  120 . Further, in addition to being electrically coupled to the transformer  125 , the indoor control board  126 , and the A2L sensor  170 , as discussed above, the A2L control board  150  may be electrically coupled to the blower motor  123 . In one or more embodiments, the A2L control board  150  may be configured to signal the blower motor  123  to run either by way of a 24 volt A/C line connected to an input lead  128  on the blower motor  123 , if the blower motor  123  is a constant torque motor, or by way of a line voltage provided to the input lead  128  of the blower motor  123 , if the blower motor  123  is a PSC motor. 
     In one or more embodiments, the A2L control board  150  may include a power supply  151 , a power-in contact point  152 , a first relay  153 , a first power-out contact point  154 , a second relay  155 , a second power-out contact point  156 , a first sensor connector  157 , a second sensor connector  158 , a buzzer  159 , a light emitting diode (LED)  160 , a dry contact relay  161 , first and second ventilator contact points  162   a  and  162   b , and a fuse  163 . The power supply  151  may be coupled to circuitry on the A2L control board  150  such that the A2L control board may open and close, at least, the first relay  153 , the second relay  154 , and the dry contact relay  161 . Further, in one or more embodiments, the first relay  153  may be electrically disposed between the power-in contact point  152  and the first power-out contact point  154 , such that when the first relay  153  is open, power from the power-in contact point  152  does not reach the first power-out contact point  154 . Furthermore, the fuse  163  may be electrically disposed between the power-in contact point  152  and the first relay  153 . Similarly, in one or more embodiments, the second relay  155  may be electrically disposed between the power-in contact point  152  and the second power-out contact point  156 , such that when the second relay  155  is open, power from the power-in contact point  152  does not reach the second power-out contact point  156 . Additionally, the fuse  163  may be electrically disposed between the power-in contact point  152  and the second relay  155 . By way of example, in one or more embodiments, when the first relay  153  is open, the second relay  155  is closed, and when the second relay  155  is open, the first relay  153  is closed. Further, in one or more embodiments, in the default state, the first relay  153  is open and the second relay  155  is closed. 
     In one or more embodiments, the transformer  125  may be electrically coupled to the power-in contact point  152 , the first power-out contact point  154  may be electrically coupled to the indoor control board  126 , and the second power-out contact point  156  may be electrically coupled to the blower motor  123 .  FIG.  1    displays a default state of the A2L control board  150 , where the 24 volt A/C power coming from the transformer  125  is routed to the blower motor  123 , causing it to run. Further, in one or more embodiments, if the A2L control board  150  fails, the relays all revert to their default state, and thus, if the A2L control board  150  fails, power will be directed to the blower motor  123 . Furthermore, in one or more embodiments, when the A2L control board  150  is turned on, the second relay  154  immediately opens so that the blower motor  123  is not unnecessarily run. Additionally, after the A2L control board  150  is turned on, when the system is ready to run, the first relay  152  is closed, turning on the HVAC system  100 . 
     Further, in one or more embodiments, the power supply  151  may be coupled to the first sensor connector  157  and the second sensor connector  158 , separately. Thus, in one or more embodiments, the A2L control board  150  may separately test one or more A2L sensors  170  before closing the first relay  153  and powering up the HVAC system  100 . This allows for the A2L control board  150  to make sure that the sensors  170  are working properly and there are no A2L refrigerant leaks before beginning the system. While two separate sensor connectors are depicted, one of ordinary skill in the art would understand that the A2L control board may instead include a sensor signal-in contact and a sensor signal-out contact and the one or more sensors may be run in series instead of in parallel. 
     Thus, when the A2L control board  150  receives a signal from the A2L sensor  170  that there is an A2L refrigerant leak, the A2L control board  150  may be configured to carry out the required safety measures required by A2L safety standards. More specifically, in one or more embodiments, if a leak is detected, the A2L control board  150  may be configured to cut off power to the indoor control board  126  by opening the first relay  153 , while directing power directly to the blower motor  123  by closing the second relay  155 . Since the indoor unit  120 , the thermostat  140 , and the outdoor unit  130  receive power from the indoor control board  126 , when the A2L sensor detects an A2L refrigerant leak and the A2L control board  150  cuts power to the indoor control board  126 , the entire HVAC system  100 , besides the blower motor  123 , is configured to lose power and shut off. This allows the HVAC system  100  to meet the A2L safety requirements within the requisite time after detection of an A2L refrigerant leak. 
     Additionally, as discussed above, in one or more embodiments, the A2L control board  150  may include a buzzer  159 , an LED  160 , a dry contact relay  161 , and first and second ventilator contact points  162   a  and  162   b . In one or more embodiments, the dry contact relay  161  may be electrically coupled to a ventilator (not shown), such that when the A2L control board  150  receives an A2L refrigerant leak signal from the A2L sensor  170 , the dry contact relay  161  will flip and turn on the ventilator. Furthermore, in one or more embodiments, when the A2L control board receives an A2L refrigerant leak signal from the A2L sensor, the LED  160  and the buzzer  159  will receive power. When receiving power, the LED  160  will display an error code and the buzzer  159  will make sound in order to give visual and auditory alarms that the HVAC system  100  is experiencing an A2L refrigerant leak. 
     Referring now to  FIG.  2   , a flow chart of an embodiment of a method  200  of installing and operating a non-communicating HVAC system using an A2L refrigerant as described above with respect to  FIG.  1   , according to one or more embodiments, is illustrated. Beginning with an HVAC system  100  in which the indoor unit  120  has been disposed on an inside  111  of a building  110 , the outdoor unit  130  has been disposed on an outside  112  of the building  110 , the indoor control board  126  has been electrically coupled to the thermostat  140  and a blower motor  123  of the blower  121 , and the outdoor control board  131  has been electrically coupled to the thermostat  140 , the method  200  may include one or more of the following: (step  210 ) installing the A2L control board  150  and the A2L sensor  170  into the HVAC system  100 , (step  220 ) testing the A2L sensor  170 , (step  230 ) beginning operation of the HVAC system  100 , (step  240 ) checking for A2L refrigerant leaks, and (step  250 ) performing safety measures upon detecting an A2L refrigerant leak. 
     At step  210 , an A2L control board  150  and an A2L sensor  170  may be installed into the HVAC system  100 . Installation of the A2L control board  150  and the A2L sensor  170  may include, at least, (step  211 ) physically coupling the A2L sensor  170  to the indoor evaporator coil  124  of the indoor unit  120 , (step  212 ) electrically coupling the A2L sensor  170  to the A2L control board  150 , (step  213 ) electrically coupling the A2L control board  150  to the indoor control board  126 , (step  214 ) electrically coupling the A2L control board  150  to the blower motor  123 , (step  215 ) electrically coupling the A2L control board  150  to the transformer  125 , and (step  216 ) turning on the A2L control board  150  and opening the second relay  155 . 
     In one or more embodiments, at step  211 , the A2L sensor  170  may be disposed within the indoor unit  120  such that it is adjacent or connected to the indoor evaporator coil  124  such that the A2L sensor  170  is able to detect an A2L refrigerant leak if one occurs. Further, at step  212 , the A2L sensor  170  may be electrically coupled to the A2L control board  150  such that the A2L sensor  170  and the A2L control board  150  have two-way communication between them. By way of example, in one or more embodiments, an A2L sensor  170  may be electrically coupled to a first sensor connector  157  of the A2L control board  150  by way of an RS-485 bus. One of ordinary skill in the art would appreciate that in other embodiments, any other electric coupling that allows for two-way communication between the A2L sensor  170  and the A2L control board  150  may be used. 
     At step  213 , the A2L control board  150  may be electrically coupled to the indoor control board  126 . In one or more embodiments, a wire capable of carrying 24 volt A/C power may be electrically coupled on one end to a power-in terminal within the indoor control board  126  and on the other end to a first power-out contact  154  of the A2L control board  150 . Thus, once a transformer  125  is electrically coupled to the A2L control board  150 , providing a 24 volt A/C power to the A2L control board  150 , and a first relay  153  is closed, the indoor control board  126  may receive the 24 volt A/C power. 
     At step  214 , the A2L control board  150  may be electrically coupled to the blower motor  123 . In one or more embodiments, a wire capable of carrying 24 volt A/C power may be electrically coupled on one end to an input lead  128  on the blower motor  123  and on the other end to a second power-out contact  156  of the A2L control board  150 . Thus, once a transformer  125  is electrically coupled to the A2L control board  150  providing a 24 volt A/C power to the A2L control board  150 , the blower motor  123  may receive the 24 volt A/C power whenever the second relay  155  is closed. In one or more embodiments, the default for the second relay  155  may be that it is closed; however, while the HVAC system is running and no A2L leak is detected, the second relay  155  is kept open. Further, in the event that an A2L refrigerant leak is detected, the second relay  155  is closed such that the blower motor  123  may receive the 24 volt A/C power even though the rest of the HVAC system is shut down. 
     At step  215 , the A2L control board  150  may be electrically coupled to the transformer  125 . In one or more embodiments, a wire capable of carrying 24 volt A/C power may be electrically coupled on one end to a power-out terminal within the transformer  125  and on the other end to a power-in contact  152  of the A2L control board  150 . Thus, once the transformer  125  is electrically coupled to the A2L control board  150 , the A2L control board has a 24 volt A/C power that it may distribute to either the indoor control board  126  or the blower motor  123 . 
     At step  216 , the A2L control board  150  may be turned on and the second relay  155  may be opened. In one or more embodiments, when the A2L control board  150  is turned on, the relays are in the default state, which includes the second relay  155  being closed. Thus, in order to make sure power is not unnecessarily diverted to the blower motor  123 , in one or more embodiments, when the A2L control board  150  powers up, the A2L control board  150  opens the second relay  155 . 
     At step  220 , the A2L sensor  170  may be tested to confirm that it is properly operational. Once electrically coupled to the A2L control board  150 , in one or more embodiments, the A2L sensor  170  may perform an internal diagnostic check to make sure that the sensor is operating properly and may detect an A2L refrigerant leak. If the diagnostic check is successful, the A2L sensor  170  may communicate the successful diagnostic check to the A2L control board  150 , which can begin operation of the HVAC system  100 . If the A2L sensor  170  fails the diagnostic check, the A2L sensor  170  will communicate the failed diagnostic check to the A2L control board  150 , which will remain in the default configuration, keeping the HVAC system  100  from operating until the A2L sensor is repaired or replaced. 
     At step  230 , the A2L control board  150  may begin operation of the HVAC system  100 . In order to begin operation, in one or more embodiments, the A2L control board  150  may close the first relay  153  of the A2L control board  150 . Closing the first relay  153  allows for the 24 volt A/C power that the A2L control board  150  receives from the transformer  125  to pass to the indoor control board  126  and power up the rest of the HVAC system  100 . 
     At step  240 , while the HVAC system is running, in one or more embodiments, the A2L sensor  170  may check for A2L refrigerant leaks. The A2L sensor  170  may continuously check for A2L refrigerant leaks while the HVAC system  100  is running, such that if a check comes back negative for an A2L refrigerant leak, the A2L sensor  170  repeats step  240 . However, if the AL2 sensor  170  detects an A2L leak, then the A2L sensor  170  communicates the A2L refrigerant leak to the A2L control board and the HVAC system continues to step  250 . 
     At step  250 , the HVAC system  100 , by way of the A2L control board  150 , may perform safety measures to eliminate the threat of the detected A2L refrigerant leak. Specifically, the HVAC system  100  may (step  252 ) open the first relay  153 , (step  253 ) close the second relay  155 , (step  254 ) close the dry contact relay  161 , (step  256 ) power on the LED  160 , and (step  258 ) power on the buzzer  159 . At step  252 , opening the first relay  153  prevents the 24 volt A/C power that the A2L control board  150  receives from the transformer  125  from passing to the indoor control board  126 . Removing the 24 volt A/C power from the indoor control board  126  in turn removes power from the entire HVAC system  100  since the blower motor  123 , thermostat  140 , and outdoor unit  130  are all configured to receive 24 volt A/C power, either directly or indirectly, from the indoor control board  126 . Additionally, at step  253 , closing the second relay  155  causes the 24 volt A/C power that the A2L control board  150  receives from the transformer  125  to pass to the blower motor  123  directly. The 24 volt A/C power run directly to the blower motor  123  causes the blower motor  123  to run even though the indoor control board  126  and the thermostat  140  have no power and are turned off. Further, while listed as separate steps, one of ordinary skill would appreciate that in one or more embodiments, either step  252  or step  253  may take place before the other, or in other embodiments, step  252  and step  253  may occur simultaneously. Additionally, one of ordinary skill in the art would appreciate that both steps  252  and  253  may be completed within the requisite time after detection of an A2L refrigerant leak as required by A2L safety standards. 
     At step  254 , in one or more embodiments, the A2L control board  150  may close the dry contact relay  161  that turns on a ventilator. In one or more embodiments, a ventilator may be connected to the HVAC system  100  by way of first and second ventilator contact points  162   a  and  162   b  on the A2L control board  150 . Thus, when the A2L sensor  170  detects a leak, the A2L control board  150  may close the dry contact relay  161 , which allows power to run directly to the ventilator and turns on the ventilator. Further, at step  256 , when the A2L control board  150  receives the A2L refrigerant leak communication, the A2L control board  150  may provide power to the LED  160 . Furthermore, at step  258 , when the A2L control board  150  receives the A2L refrigerant leak communication, the A2L control board  150  may provide power to the buzzer  159 . 
     Thus, in one or more embodiments, in response to a communication from the A2L sensor  170  that an A2L refrigerant leak has been detected, the A2L control board  150  may turn off the entirety of the HVAC system  100 , except the blower motor  123 , which is powered on, turn on a ventilator if the HVAC system  100  has one, and turn on visual and auditory alarms that an A2L refrigerant leak has been detected. 
     While the method  200  is described with respect to an HVAC system  100  including a single A2L sensor  170 , one of ordinary skill in the art, would understand that any number of sensors may be used in the system and the method may include electrically coupling the further sensors to the control board, testing the further sensors, and communicating with the further sensors as the further sensors check for A2L refrigerant leaks. 
       FIG.  3    shows a communicating HVAC system using an A2L refrigerant, according to a one or more embodiments. In one or more embodiments, an HVAC system  300  may be used to distribute cooled or heated air throughout a building  310  to adjust the ambient air temperature inside  311  of the building  310 . The HVAC system may include an indoor unit  320 , an outdoor unit  330 , a thermostat  340 , an A2L control board  350 , an A2L sensor  370 , an outdoor relay  380 , and a high pressure switch  390 . 
     Generally, in one or more embodiments, the indoor unit  320  may be fluidly coupled to the outdoor unit  330  such that an A2L refrigerant may flow between the indoor unit  320  and the outdoor unit  330  to cool or heat air within the indoor unit  320 . Further, in one or more embodiments, both the indoor unit  320  and the outdoor unit  330  may be communicatively coupled to each other by way of an RS-485 system communication. The thermostat  340  may be either a non-communicating or communicating thermostat and may be electrically coupled to the indoor unit  320  either by a 24 volt A/C connection or an R-485 system communication. Furthermore, in one or more embodiments, the A2L control board  350  may be directly electrically coupled to the indoor unit  320  and indirectly electrically coupled to the outdoor unit  330  by way of the outdoor relay  380  and the high pressure switch  390 . The A2L control board  350  may act as a passthrough for power to the indoor unit  320  and may be configured to block power from getting to certain parts of the indoor unit  320  if there is an A2L refrigerant leak in the system. Additionally, the A2L control board  350  may be configured to turn off the outdoor unit by way of electrical connections between the A2L control board  350 , the outdoor relay  380 , the high pressure switch  390 , and the outdoor unit  320 . Further, the A2L sensor  370  may be physically disposed within the indoor unit  320  and electrically coupled to the A2L control board  350 . The A2L sensor  370  may be configured to send signals to the A2L control board  350  when an A2L refrigerant leak is detected. 
     In one or more embodiments, indoor unit  320  may be disposed on the inside  311  of the building  310 . The indoor unit  320  may be configured to distribute cooled or heated air to rooms on the inside  311  of the building  310 . The indoor unit  320  may be any type of HVAC system that includes a blower  321  and a heat exchanger  327  having an indoor evaporator coil  324 . Thus, in one or more embodiments, the indoor unit  320  may be either a furnace or an air handler, as both types of system include, at least, a blower and an indoor evaporator coil. Additionally, the indoor evaporator coil  324  may be disposed adjacent to the blower  321 , such that when the blower  321  blows air within the indoor unit  320 , the air is blown through the evaporator coil  324 . 
     Further, in one or more embodiments, the blower  321  may include a blower fan  322  and a blower motor  323 . By way of example, in one or more embodiments, the blower motor  323  may be constant torque motor, while in other embodiments, the blower motor  323  may be a permanent split capacitor (PSC) motor. The blower motor  323  may be mechanically coupled to the blower fan  322  such that when the blower motor  323  is turned on, the blower fan  322  is configured to spin and cause a movement of air out from the blower  321  and through the indoor evaporator coil  324 . The indoor evaporator coil  324  may be configured to receive the A2L refrigerant on the inside of the coil while air from the blower  321  is blown across the outside of the coil, which allows for heat to exchange either from the A2L refrigerant to the air or vice versa. The A2L refrigerant, after cooling or heating the air, may be cycled back to the outdoor unit  330 , where it will go through the reverse heat exchange process before returning to the indoor evaporator coil  324 . Additionally, indoor unit  320  is configured to distribute the air that is blown from the blower  321  and across the indoor evaporator coil  324  to the rooms on the inside  311  of the building  310  by way of the force of the blower  321 . 
     The indoor unit  320  may also include a transformer  325  and an indoor control board  326 . The transformer  325  may be directly electrically coupled to and configured to provide 24 volts A/C power to the A2L control board  350 . Further, the indoor control board  326  may be electrically coupled to the A2L control board  350  such that the indoor control board  326  may receive 24 volts A/C power indirectly from the transformer  325 . Additionally, the indoor control board  326  may be electrically coupled to, at least, the blower motor  323  and the thermostat  340 . In one or more embodiments, the transformer  325  may be configured to indirectly provide a 24 volt A/C power to the blower motor  323  by way of the indoor control board  326  and the A2L control board  350 . In one or more embodiments, the blower motor has its own source of power. So, while the 24 volt A/C power that the blower motor receives does not power on the blower motor  323 , the 24 volt A/C signal is needed to turn the blower motor  323  on. Further, the indoor control board  326  may be electrically coupled to the thermostat by either a 24 volt A/C power connection or by an R-485 system communication depending on whether the thermostat is a non-communicating or communicating thermostat, respectively. 
     Further, the outdoor unit  330  may be disposed on an outside  312  of the building  310  and be configured to use the outdoor environment to reheat or cool down the A2L refrigerant after it has been run through the indoor evaporator coil  324 . The outdoor unit  330  may include, but is not limited to, either a heat pump or an air conditioner. Whether the outdoor unit  330  is a heat pump or an air conditioner, the outdoor unit  330  may include a compressor (not shown), an outdoor coil (not shown), and an outdoor control board  331 . The outdoor unit  330  may be configured to communicate with the indoor unit  320  through RS-485 system communication between the indoor control board  326  and the outdoor control board  331 . Further, the outdoor control board  331  may be electrically coupled to the A2L control board  350  as discussed below. 
     Still referring to  FIG.  3   , in one or more embodiments, the A2L sensor  370  may be configured to detect an A2L refrigerant leak and send a signal reporting as much. In one or more embodiments, the A2L sensor  370  may be configured to detect an A2L refrigerant leak by one of a number of methods, including, at least, by detecting an amount or a concentration of A2L refrigerant in the air that exceeds a leak threshold. The A2L sensor  370  may be electrically coupled to and communicate with the A2L control board  350 . In one or more embodiments, the A2L sensor  370  may be electrically coupled to the A2L control board  350  by way of a first sensor connector  357 . The A2L sensor  370  may be configured to communicate to the A2L control board  350  that the A2L sensor  370  is connected to the system and working properly. Additionally, when the A2L sensor  370  detects an A2L refrigerant leak, it may communicate the A2L refrigerant leak to the A2L control board  350 , which may be configured to receive the signal and perform the safety measures required by A2L safety standards. In one or more embodiments, the A2L sensor  370  and the A2L control board  350  may be electrically coupled by way of an RS-485 bus; however, one of ordinary skill in the art would understand that any type of electrical connection that allows the A2L sensor  370  to send a signal to the A2L control board  350  may be used. 
     While the A2L sensor  370  is depicted as being electrically and communicatively coupled to the A2L control board  350  by way of a wired connection, one of ordinary skill in the art would understand that the A2L sensor  370  may just be communicatively coupled to the A2L control board  350  wirelessly. In one or more embodiments, the A2L sensor  370  may be communicatively coupled to the A2L control board  350  by any wireless means, such as Wi-Fi or Bluetooth. 
     Further, in one or more embodiments, the A2L sensor  370  may be disposed within the indoor unit  320  so that it may detect an A2L refrigerant leak that occurs within the indoor evaporator coil  324  of the HVAC system  300 . As depicted, in one or more embodiments, the A2L sensor  370  may be disposed directly against the indoor evaporator coil to minimize the time it takes for the A2L sensor  370  to detect an A2L refrigerant leak. Further, while the A2L sensor  370  is depicted within the indoor unit  320 , one or ordinary skill in the art would understand that the A2L sensor  370  may instead be disposed within the outdoor unit  330 . Further, while a single sensor is depicted, one of ordinary skill in the art would understand that multiple sensors may be incorporated into the HVAC system to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. For example, one of ordinary skill in the art would understand that the HVAC system may include two A2L sensors, with both A2L sensors disposed within the indoor unit, both A2L sensors disposed within the outdoor unit, or one A2L sensor disposed within each of the indoor unit and the outdoor unit. Thus, one of ordinary skill in the art would understand that in one or more embodiments, a plurality of A2L sensors may be disposed within the HVAC system with one or more A2L sensors disposed within the indoor unit and/or one or more A2L sensors disposed within the outdoor unit as may be determined necessary to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. 
     Additionally, referring to  FIG.  3   , in one or more embodiments, the A2L control board  350  may be disposed inside of the indoor unit  320 . However, one of ordinary skill in the art would understand that, in one or more embodiments, the A2L control board  350  may be disposed outside of the indoor unit  320  and either connected to the indoor unit  320  or adjacent to the indoor unit  320 . Further, in addition to being electrically coupled to the transformer  325 , the indoor control board  326 , and the A2L sensor  370 , as discussed above, the A2L control board  350  may be electrically coupled to the outdoor control board  331  by way of the outdoor relay  380  and the high pressure switch  390 . In one or more embodiments, the outdoor relay  380  and the high pressure switch  390  may be electrically coupled in series between the A2L control board  350  and the outdoor control board  331 . In one or more embodiments, the outdoor relay  380  may be directly electrically coupled to the A2L control board  350  such that the outdoor relay  380  is configured to open upon receiving a 24 volt A/C power signal from the A2L control board  350 . Further, in one or more embodiments, the high pressure switch  390  is electrically coupled to the outdoor control board  331  such that when the high pressure switch  390  opens, the outdoor unit  330  shuts down completely. Furthermore, in one or more embodiments, opening the outdoor relay  380  causes the high pressure switch  390  to open, which causes the outdoor unit  330  to shut down completely. 
     In one or more embodiments, the A2L control board  350  may include a power supply  351 , a power-in contact point  352 , a first relay  353 , a first power-out contact point  354 , a second relay  355 , a second power-out contact point  356 , a first sensor connector  357 , a second sensor connector  358 , a buzzer  359 , an LED  360 , a dry contact relay  361 , first and second ventilator contact points  362   a  and  362   b , and a fuse  363 . The power supply  351  may be coupled to circuitry on the A2L control board  350  such that the A2L control board may open and close, at least, the first relay  353 , the second relay  354 , and the dry contact relay  361 . Further, in one or more embodiments, the first relay  353  may be electrically disposed between the power-in contact point  352  and the first power-out contact point  354 , such that when the first relay  353  is open, power from the power-in contact point  352  does not reach the first power-out contact point  354 . Furthermore, the fuse  363  may be electrically disposed between the power-in contact point  352  and the first relay  353 . Similarly, in one or more embodiments, the second relay  355  may be electrically disposed between the power-in contact point  352  and the second power-out contact point  356 , such that when the second relay  355  is open, power from the power-in contact point  352  does not reach the second power-out contact point  356 . Additionally, the fuse  363  may be electrically disposed between the power-in contact point  352  and the second relay  355 . By way of example, in one or more embodiments, when the first relay  353  is open, the second relay  355  is closed, and when the second relay  355  is open, the first relay  353  is closed. Further, in one or more embodiments, in the default state, the first relay  353  is open and the second relay  355  is closed. 
     In one or more embodiments, the transformer  325  may be electrically coupled to the power-in contact point  352 , the first power-out contact point  354  may be electrically coupled to the indoor control board  326 , and the second power-out contact point  356  may be electrically coupled to outdoor relay  380 .  FIG.  3    displays a default state of the A2L control board  350 , where the 24 volt A/C power coming from the transformer  325  is routed to the outdoor relay  380 . Further, in one or more embodiments, if the A2L control board  350  fails, the relays all revert to their default state, and thus, if the A2L control board  350  fails, power will be directed to the outdoor relay  380 , causing it to open, thus opening the high pressure switch  390  and shutting off the outdoor unit  330 . Furthermore, in one or more embodiments, when the A2L control board  150  is turned on, the second relay  154  immediately opens so that power is not unnecessarily run to the outdoor relay  380  before necessary. Additionally, after the A2L control board  350  is turned on, when the system is ready to run, the first relay  352  is closed, turning on the HVAC system  300 . 
     Further, in one or more embodiments, the power supply  351  may be coupled to the first sensor connector  357  and the second sensor connector  358 , separately. Thus, in one or more embodiments, the A2L control board  350  may separately test one or more A2L sensors  370  before closing the first relay  353  and powering up the HVAC system  300 . This allows for the A2L control board  350  to make sure that the sensors  370  are working properly and there are no A2L refrigerant leaks before beginning the system. While two separate sensor connectors are depicted, one of ordinary skill in the art would understand that the A2L control board may instead include a sensor signal-in contact and a sensor signal-out contact and the one or more sensors may be run in series instead of in parallel. 
     Thus, when the A2L control board  350  receives a signal from the A2L sensor  370  that there is an A2L refrigerant leak, the A2L control board  350  may be configured to carry out the required safety measures required by A2L safety standards. More specifically, in one or more embodiments, if a leak is detected, the A2L control board  350  may be configured to cut off power to the indoor control board  326  by opening the first relay  353 , while directing power directly to the outdoor relay  380  by closing the second relay  355 . Since the indoor unit  320  receives power from the indoor control board  326 , when the A2L sensor detects an A2L refrigerant leak and the A2L control board  350  cuts power to the indoor control board  326 , the indoor unit  320  is configured to lose power and shut off. Further, in one or more embodiments, the blower motor  323  may be configured such that if the blower motor  323  loses signal from the indoor control board  326 , the blower motor  323  turns on and stays on. Thus, when the A2L control board  350  removes power from the indoor control board  326  in response to a detected A2L refrigerant leak, the blower motor  323  will lose a signal from the indoor control board  326  and turn on. Further, closing the second relay  355  in response to an A2L refrigerant leak being detected causes power to be diverted directly to the outdoor relay  380 . Furthermore, in one or more embodiments, power being diverted directly to the outdoor relay  380  causes the outdoor relay  380  to open. Moreover, opening the outdoor relay  380  is configured to cause the high pressure switch  390  to open. Additionally, the outdoor unit  330  is configured to shut down completely if the high pressure switch  390  is opened. Thus, opening the second relay  355  is configured to shut down the outdoor unit  330  completely. This allows the HVAC system  300  to meet the A2L safety requirements within the requisite time after detection of an A2L refrigerant leak. 
     While  FIG.  3    depicts one or more embodiments of the present invention that utilize an outdoor relay  380  and a high pressure switch  390  in order to shut off the outdoor unit in the event of an A2L refrigerant leak, one of ordinary skill in the art would understand that any means of turning off the compressor of the outdoor unit would work to properly meet the A2L safety requirements. By way of example, in one or more embodiments, the HVAC system may include an A2L control board that is electrically coupled to a contactor, where the contactor is configured to contact the outdoor control board such that the outdoor unit shuts off in the event of an A2L refrigerant leak being detected. Further, in other embodiments, the A2L control board may be communicatively coupled to the outdoor control board by way of an RS-485 system communication such that the A2L control board can tell the outdoor control board to shut down the outdoor unit in the event of an A2L leak being detected. Furthermore, in one or more embodiments, the A2L control board may be electrically coupled to a relay, where the relay is disposed between the outdoor control board and the compressor of the outdoor unit such that when the relay is opened, power from the outdoor control board does not reach the compressor, and the compressor shuts down. 
     Further, while in one or more embodiments a 24 volt A/C signal is used by the A2L control board to communicate with the outdoor relay to shut down the outdoor unit, one of ordinary skill in the art would understand that, in one or more embodiments, the A2L control board may send digital signals to the outdoor relay. One of ordinary skill in the art would understand that digital signals may also be used with a contactor or any other relay coupled to the outdoor control board to shut down the outdoor unit. Furthermore, in one or more embodiments, the A2L control board may be wirelessly, communicatively coupled to the outdoor control board such that wireless signals may be used to turn off the outdoor unit. 
     Additionally, as discussed above, in one or more embodiments, the A2L control board  350  may include a buzzer  359 , an LED  360 , a dry contact relay  361 , and first and second ventilator contact points  362   a  and  362   b . In one or more embodiments, the dry contact relay  361  may be electrically coupled to a ventilator (not shown), such that when the A2L control board  350  receives an A2L refrigerant leak signal from the A2L sensor  370 , the dry contact relay  361  will flip and turn on the ventilator. Furthermore, in one or more embodiments, when the A2L control board receives an A2L refrigerant leak signal from the A2L sensor, the LED  360  and the buzzer  359  will receive power. When receiving power, the LED  360  will display an error code and the buzzer  359  will make sound in order to give visual and auditory alarms that the HVAC system  300  is experiencing an A2L refrigerant leak. 
     Referring now to  FIG.  4   , a flow chart of an embodiment of a method  400  of installing and operating a communicating HVAC system using an A2L refrigerant as described above with respect to  FIG.  3   , according to one or more embodiments, is illustrated. Beginning with an HVAC system  300  in which the indoor unit  320  has been disposed on an inside  311  of a building  310 , the outdoor unit  330  has been disposed on an outside  312  of the building  310 , the indoor control board  326  has been electrically coupled to the thermostat  340  and a blower motor  323  of the blower  321 , and the outdoor control board  331  has been communicatively coupled to the indoor control board  326 , the method  400  may include one or more of the following: (step  410 ) installing the A2L control board  350  and the A2L sensor  370  into the HVAC system  300 , (step  420 ) testing the A2L sensor  370 , (step  430 ) beginning operation of the HVAC system  300 , (step  440 ) checking for A2L refrigerant leaks, and (step  450 ) performing safety measures upon detecting an A2L refrigerant leak. 
     At step  410 , an A2L control board  350  and an A2L sensor  370  may be installed into the HVAC system  300 . Installation of the A2L control board  350  and the A2L sensor  370  may include, at least, (step  411 ) physically coupling the A2L sensor  370  to the indoor evaporator coil  324  of the indoor unit  320 , (step  412 ) electrically coupling the A2L sensor  370  to the A2L control board  350 , (step  413 ) electrically coupling the A2L control board  350  to the indoor control board  326 , (step  414 ) electrically coupling the A2L control board  350  to outdoor control board  331 , (step  415 ) electrically coupling the A2L control board  350  to the transformer  325 , and (step  416 ) turning on the A2L control board  150  and opening the second relay  155 . 
     In one or more embodiments, at step  411 , the A2L sensor  370  may be disposed within the indoor unit  320  such that it is adjacent or connected to the indoor evaporator coil  324  such that the A2L sensor  370  is able to detect an A2L refrigerant leak if one occurs. Further, at step  412 , the A2L sensor  370  may be electrically coupled to the A2L control board  350  such that the A2L sensor  370  and the A2L control board  350  have two-way communication between them. By way of example, in one or more embodiments, an A2L sensor  370  may be electrically coupled to a first sensor connector  357  of the A2L control board  350  by way of an RS-485 bus. One of ordinary skill in the art would appreciate that in other embodiments, any other electric coupling that allows for two-way communication between the A2L sensor  370  and the A2L control board  350  may be used. 
     At step  413 , the A2L control board  350  may be electrically coupled to the indoor control board  326 . In one or more embodiments, a wire capable of carrying 24 volt A/C power may be electrically coupled on one end to a power-in terminal within the indoor control board  326  and on the other end to a first power-out contact  354  of the A2L control board  350 . Thus, once a transformer  325  is electrically coupled to the A2L control board  350 , providing a 24 volt A/C power to the A2L control board  350 , and a first relay  353  is closed, the indoor control board  326  may receive the 24 volt A/C power. 
     At step  414 , the A2L control board  350  may be electrically coupled to the outdoor control board  331 . In one or more embodiments, the high pressure switch  390  may be electrically coupled to the outdoor control board  331  such that when the high pressure switch  390  opens, the outdoor control board  331  shuts down. Further, the outdoor relay  380  may be electrically coupled to the high pressure switch  390  such that when the outdoor relay opens, the high pressure switch opens. Furthermore, the outdoor relay  380  may be electrically coupled to a second power-out contact  356  of the A2L control board  350  by way of a wire capable of carrying 24 volt A/C power. Thus, once a transformer  325  is electrically coupled to the A2L control board  350 , providing a 24 volt A/C power to the A2L control board  350 , closing the second relay  355  causes the outdoor relay  380  to open, which causes the high pressure switch  390  to open, which causes the outdoor control board  331  to shut down the outdoor unit  330 . In one or more embodiments, the default for the second relay  355  may be that it is closed; however, while the HVAC system is running and no A2L leak is detected, the second relay  355  is kept open. Further, in the event that an A2L refrigerant leak is detected, the second relay  355  is closed which causes the outdoor unit  330  to shut down completely. 
     At step  415 , the A2L control board  350  may be electrically coupled to the transformer  325 . In one or more embodiments, a wire capable of carrying 24 volt A/C power may be electrically coupled on one end to a power-out terminal within the transformer  325  and on the other end to a power-in contact  352  of the A2L control board  350 . Thus, once the transformer  325  is electrically coupled to the A2L control board  350 , the A2L control board has a 24 volt A/C power that it may distribute to either the indoor control board  326  or the outdoor relay  380 . 
     At step  416 , the A2L control board  350  may be turned on and the second relay  355  may be opened. In one or more embodiments, when the A2L control board  350  is turned on, the relays are in the default state, which includes the second relay  355  being closed. Thus, in order to make sure power is not unnecessarily diverted to the blower motor  323 , in one or more embodiments, when the A2L control board  350  powers up, the A2L control board  350  opens the second relay  355 . 
     At step  420 , the A2L sensor  370  may be tested to confirm that it is properly operational. Once electrically coupled to the A2L control board  350 , in one or more embodiments, the A2L sensor  370  may perform an internal diagnostic check to make sure that the sensor is operating properly and may detect an A2L refrigerant leak. If the diagnostic check is successful, the A2L sensor  370  may communicate the successful diagnostic check to the A2L control board  350 , which can begin operation of the HVAC system  300 . If the A2L sensor  370  fails the diagnostic check, the A2L sensor  370  will communicate the failed diagnostic check to the A2L control board  350 , which will remain in the default configuration, keeping the HVAC system  300  from operating until the A2L sensor is repaired or replaced. 
     At step  430 , the A2L control board  350  may begin operation of the HVAC system  300 . In order to begin operation, in one or more embodiments, the A2L control board  350  may close the first relay  353  of the A2L control board  350 . Closing the first relay  353  allows for the 24 volt A/C power that the A2L control board  350  receives from the transformer  325  to pass to the indoor control board  326  and power up the indoor unit  320 . 
     At step  440 , while the HVAC system is running, in one or more embodiments, the A2L sensor  370  may check for A2L refrigerant leaks. The A2L sensor  370  may continuously check for A2L refrigerant leaks while the HVAC system  300  is running, such that if a check comes back negative for an A2L refrigerant leak, the A2L sensor  370  repeats step  440 . However, if the AL2 sensor  370  detects an A2L leak, then the A2L sensor  370  communicates the A2L refrigerant leak to the A2L control board and the HVAC system continues to step  450 . 
     At step  450 , the HVAC system  300 , by way of the A2L control board  350 , may perform safety measures to eliminate the threat of the detected A2L refrigerant leak. Specifically, the HVAC system  300  may (step  452 ) open the first relay  353 , (step  453 ) close the second relay  355 , (step  454 ) close the dry contact relay  361 , (step  456 ) power on the LED  360 , and (step  458 ) power on the buzzer  359 . At step  452 , opening the first relay  353  prevents the 24 volt A/C power that the A2L control board  350  receives from the transformer  325  from passing to the indoor control board  326 , thus removing the 24 volt A/C power from the indoor unit  320 . As discussed above, removing the power from the indoor unit  320  causes the blower motor  323  to lose its signal from the indoors control board  326  such, which causes the blower motor  323  to turn on and remain on. Additionally, at step  453 , closing the second relay  355  causes the 24 volt A/C power that the A2L control board  350  receives from the transformer  325  to pass to the outdoor relay  380 . As discussed above, the 24 volt A/C power run directly to the outdoor relay  380  causes the outdoor relay  380  to open, which causes the high pressure switch  390  to open, which causes the outdoor control board  331  to turn off completely. Further, while listed as separate steps, one of ordinary skill would appreciate that in one or more embodiments, either step  452  or step  453  may take place before the other, or in other embodiments, step  452  and step  453  may occur simultaneously. Additionally, one of ordinary skill in the art would appreciate that both steps  452  and  453  may be completed within the requisite time after detection of an A2L refrigerant leak as required by A2L safety standards. 
     At step  454 , in one or more embodiments, the A2L control board  350  may close the dry contact relay  361  that turns on a ventilator. In one or more embodiments, a ventilator may be connected to the HVAC system  300  by way of first and second ventilator contact points  362   a  and  362   b  on the A2L control board  350 . Thus, when the A2L sensor  370  detects a leak, the A2L control board  350  may close the dry contact relay  361 , which allows power to run directly to the ventilator and turns on the ventilator. Further, at step  456 , when the A2L control board  350  receives the A2L refrigerant leak communication, the A2L control board  350  may provide power to the LED  360 . Furthermore, at step  458 , when the A2L control board  350  receives the A2L refrigerant leak communication, the A2L control board  350  may provide power to the buzzer  359 . 
     Thus, in one or more embodiments, in response to a communication from the A2L sensor  370  that an A2L refrigerant leak has been detected, the A2L control board  350  may turn off the indoor unit  320  and the outdoor unit  330 , except the blower motor  323 , which is powered on by the loss of signal from the indoor control board  326 , turn on a ventilator if the HVAC system  300  has one, and turn on visual and auditory alarms that an A2L refrigerant leak has been detected. 
     While the method  400  is described with respect to an HVAC system  300  including a single A2L sensor  370 , one of ordinary skill in the art, would understand that any number of sensors may be used in the system and the method may include electrically coupling the further sensors to the control board, testing the further sensors, and communicating with the further sensors as the further sensors check for A2L refrigerant leaks. 
       FIG.  5    shows a non-communicating HVAC system using an A2L refrigerant, according to one or more embodiments. In one or more embodiments, an HVAC system  500  may be used to distribute cooled or heated air throughout a building  510  to adjust the ambient air temperature inside  511  of the building  510 . The HVAC system may include an indoor unit  520 , an outdoor unit  530 , a thermostat  540 , an A2L control board  550 , and an A2L sensor  570 . Generally, in one or more embodiments, the indoor unit  520  may be fluidly coupled to the outdoor unit  530  such that an A2L refrigerant may flow between the indoor unit  520  and the outdoor unit  530  to cool or heat air within the indoor unit  520 . Further, in one or more embodiments, the indoor unit  520  may be indirectly electrically coupled to the thermostat  540 , while the outdoor unit  530  may be directly electrically coupled to the thermostat  540 . The thermostat  540  may be configured to use on/off-type signals for communication and control of the indoor unit  520  and the outdoor unit  530 . Furthermore, in one or more embodiments, the A2L control board  550  may be directly electrically coupled between the indoor unit  520  and the thermostat  540 , such that any communication or signals between the two must pass through the A2L control board  550 . Thus, in one or more embodiments, the A2L control board  550  may act as a passthrough for power to portions of the indoor unit  520 , the outdoor unit  530 , and the thermostat  540  and may be configured to block power from getting to certain parts of the indoor unit  520 , the outdoor unit  530 , and the thermostat  540  if there is an A2L refrigerant leak in the system. Additionally, an A2L sensor  570  may be physically disposed within the indoor unit  520  and electrically coupled to the A2L control board  550 . The A2L sensor  570  may be configured to send signals to the A2L control board  550  when an A2L refrigerant leak is detected. 
     In one or more embodiments, indoor unit  520  may be disposed on the inside  511  of the building  510 . The indoor unit  520  may be configured to distribute cooled or heated air to rooms on the inside  511  of the building  510 . The indoor unit  520  may be any type of HVAC system that includes a blower  521  and a heat exchanger  527  having an indoor evaporator coil  524 . Thus, in one or more embodiments, the indoor unit  520  may be either a furnace or an air handler, as both types of system include, at least, a blower and an indoor evaporator coil. Additionally, the indoor evaporator coil  524  may be disposed adjacent to the blower  521 , such that when the blower  521  blows air within the indoor unit  520 , the air is blown through the evaporator coil  524 . 
     Further, in one or more embodiments, the blower  521  may include a blower fan  522  and a blower motor  523 . By way of example, in one or more embodiments, the blower motor  523  may be constant torque motor, while in other embodiments, the blower motor  523  may be a permanent split capacitor (PSC) motor. The blower motor  523  may be mechanically coupled to the blower fan  522  such that when the blower motor  523  is turned on, the blower fan  522  is configured to spin and cause a movement of air out from the blower  521  and through the indoor evaporator coil  524 . The indoor evaporator coil  524  may be configured to receive the A2L refrigerant on the inside of the coil while air from the blower  521  is blown across the outside of the coil, which allows for heat to exchange either from the A2L refrigerant to the air or vice versa. The A2L refrigerant, after cooling or heating the air, may be cycled back to the outdoor unit  530 , where it will go through the reverse heat exchange process before returning to the indoor evaporator coil  524 . Additionally, indoor unit  520  is configured to distribute the air that is blown from the blower  521  and across the indoor evaporator coil  524  to the rooms on the inside  511  of the building  510  by way of the force of the blower  521 . 
     The indoor unit  520  may also include a transformer  525  and an indoor control board  526 . The transformer  525  may be directly electrically coupled to and configured to provide 24 volts A/C power to the indoor control board  526 . Further, the indoor control board  526  may be electrically coupled to, at least, the A2L control board  550  and the blower motor  523 . 
     Further, the outdoor unit  530  may be disposed on an outside  512  of the building  510  and be configured to use the outdoor environment to reheat or cool down the A2L refrigerant after it has been run through the indoor evaporator coil  524 . The outdoor unit  530  may include, but is not limited to, either a heat pump or an air conditioner. Whether the outdoor unit  530  is a heat pump or an air conditioner, the outdoor unit  530  may include a compressor (not shown), an outdoor coil (not shown), and an outdoor control board  531 . The outdoor unit  530  may be configured to receive power through the outdoor control board  531 , which itself is configured to receive power from the transformer  525  by way of the thermostat  540 , the indoor control board  526 , and the A2L control board  550 . By way of example only, in one or more embodiments, the outdoor control board  531  may be configured to receive power and control signals from the thermostat  540 , such that outdoor control board  531  may start the condenser after receiving a signal from the thermostat  540  to do so. 
     Still referring to  FIG.  5   , in one or more embodiments, the A2L sensor  570  may be configured to detect an A2L refrigerant leak and send a signal reporting as much. In one or more embodiments, the A2L sensor  570  may be configured to detect an A2L refrigerant leak by one of a number of methods, including, at least, by detecting an amount or a concentration of A2L refrigerant in the air that exceeds a leak threshold. The A2L sensor  570  may be electrically coupled to and communicate with the A2L control board  550 . In one or more embodiments, the A2L sensor  570  may be electrically coupled to the A2L control board  550  by way of a first sensor connector  560 . The A2L sensor  570  may be configured to communicate to the A2L control board  550  that the A2L sensor  570  is connected to the system and working properly. Additionally, when the A2L sensor  570  detects an A2L refrigerant leak, it may communicate the A2L refrigerant leak to the A2L control board  550 , which may be configured to receive the signal and perform the safety measures required by A2L safety standards. In one or more embodiments, the A2L sensor  570  and the A2L control board  550  may be electrically coupled by way of an RS-485 bus; however, one of ordinary skill in the art would understand that any type of electrical connection that allows the A2L sensor  570  to send a signal to the A2L control board  550  may be used. 
     While the A2L sensor  570  is depicted as being electrically and communicatively coupled to the A2L control board  550  by way of a wired connection, one of ordinary skill in the art would understand that the A2L sensor  570  may just be communicatively coupled to the A2L control board  550  wirelessly. In one or more embodiments, the A2L sensor  570  may be communicatively coupled to the A2L control board  550  by any wireless means, such as Wi-Fi or Bluetooth. 
     Further, in one or more embodiments, the A2L sensor  570  may be disposed within the indoor unit  520  so that it may detect an A2L refrigerant leak that occurs within the indoor evaporator coil  524  of the HVAC system  500 . As depicted, in one or more embodiments, the A2L sensor  570  may be disposed directly against the indoor evaporator coil to minimize the time it takes for the A2L sensor  570  to detect an A2L refrigerant leak. Further, while the A2L sensor  570  is depicted within the indoor unit  520 , one or ordinary skill in the art would understand that the A2L sensor  570  may instead be disposed within the outdoor unit  530 . Further, while a single sensor is depicted, one of ordinary skill in the art would understand that multiple sensors may be incorporated into the HVAC system to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. For example, one of ordinary skill in the art would understand that the HVAC system may include two A2L sensors, with both A2L sensors disposed within the indoor unit, both A2L sensors disposed within the outdoor unit, or one A2L sensor disposed within each of the indoor unit and the outdoor unit. Thus, one of ordinary skill in the art would understand that in one or more embodiments, a plurality of A2L sensors may be disposed within the HVAC system with one or more A2L sensors disposed within the indoor unit and/or one or more A2L sensors disposed within the outdoor unit as may be determined necessary to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. 
     Additionally, referring to  FIG.  5   , in one or more embodiments, the A2L control board  550  may be disposed inside of the indoor unit  520 . However, one of ordinary skill in the art would understand that, in one or more embodiments, the A2L control board  550  may be disposed outside of the indoor unit  520  and either connected to the indoor unit  520  or adjacent to the indoor unit  520 . Further, as discussed above, the A2L control board  550  may be electrically coupled to the indoor control board  526 , the thermostat  540 , and the A2L sensor  570 . 
     In one or more embodiments, the A2L control board  550  may include a power supply (not shown), a first terminal block  551 , a second terminal block  552 , an R wire relay  553 , an G wire relay  554 , a W1 wire relay  555 , a W2 wire relay  556 , a Y1 wire relay  557 , a Y2 wire relay  558 , an alarm relay  559 , a first sensor connector  560 , a second sensor connector  561 , a buzzer  562 , an LED  563 , a dry contact relay  564 , and first and second ventilator contact points  565   a  and  565   b . The power supply may be coupled to circuitry on the A2L control board  550  such that the A2L control board may open and close, at least, the R wire relay  553 , the G wire relay  554 , the W1 wire relay  555 , the W2 wire relay  556 , the Y1 wire relay  557 , the Y2 wire relay  558 , the alarm relay  559 , and the dry contact relay  564 . 
     In one or more embodiments, the thermostat  540  may be electrically coupled to the first terminal block  551 , and the indoor control board  526  may be electrically coupled to the second terminal block  552 . Further, in one or more embodiments, any signals received by the A2L control board  550  from the thermostat  540  may be passed unchanged, by the A2L control board  550 , to the indoor control board  530  through the second terminal block  552 . 
     In one or more embodiments, the R wire relay  553  may be electrically disposed between the power supply and the R wire connection of the first terminal block  551 . Thus, when the R wire relay  553  is closed, 24 volt A/C power may be delivered from the A2L control board  550  to the thermostat  540  via the first terminal block  551 , which powers the thermostat  540  on. Further, when the R wire relay  553  is open, no power is able to reach the thermostat, and thus, the thermostat and, indirectly, the outdoor unit  530  are turned off completely. Additionally, as depicted in  FIG.  5   , in one or more embodiments, the default state for the R wire relay  553  is to be open. 
     In one or more embodiments, the G wire relay  554  may be electrically disposed between the power supply and the G wire connection of the second terminal block  552 . Thus, when the G wire relay  554  is closed, 24 volt A/C power may be delivered from the A2L control board  550  to the indoor control board  526  via the first terminal block  551 , which signals the indoor control board  526  to power the blower motor  523  on. Further, when the G wire relay  554  is open, no signal is sent along the G wire to the indoor control board  526 , and thus, the blower motor  523  is powered off. Additionally, as depicted in  FIG.  5   , in one or more embodiments, the default state for the G wire relay  554  is to be closed. 
     In one or more embodiments, the W1 wire relay  555  may be electrically disposed between the power supply and the W1 wire connection of the second terminal block  552 , and the W2 wire relay  556  may be electrically disposed between the power supply and the W2 wire connection of the second terminal block  552 . Thus, when the W1 wire relay  555  and the W2 wire relay  556  are closed, 24 volt A/C power may be delivered from the A2L control board  550  to the indoor control board  526  via the first terminal block  551 , which signals the indoor control board  526  to run the heating system&#39;s first and second stages, respectively. Further, when the W1 wire relay  555  and W2 wire relay  556  are open, no signal is sent along the W1 or W2 wires to the indoor control board  526 , and thus, the heating system is powered off. Additionally, as depicted in  FIG.  5   , in one or more embodiments, the default states for the W1 wire relay  555  and the W2 wire relay  556  are to be open. 
     In one or more embodiments, the Y1 wire relay  557  may be electrically disposed between the power supply and the Y1 wire connection of the second terminal block  552 , and the Y2 wire relay  558  may be electrically disposed between the power supply and the Y2 wire connection of the second terminal block  552 . Thus, when the Y1 wire relay  557  and the Y2 wire relay  558  are closed, 24 volt A/C power may be delivered from the A2L control board  550  to the indoor control board  526  via the first terminal block  551 , which signals the indoor control board  526  to run the cooling system&#39;s first and second stages, respectively. Further, when the Y1 wire relay  557  and Y2 wire relay  558  are open, no signal is sent along the Y1 or Y2 wires to the indoor control board  526 , and thus, the cooling system is powered off. Additionally, as depicted in  FIG.  5   , in one or more embodiments, the default states for the Y1 wire relay  557  and the Y2 wire relay  558  are to be closed. 
     Additionally, in one or more embodiments, the alarm relay  559  may be electrically disposed between the power supply and an alarm (not shown), which includes, in part, the buzzer  562  and the LED  563 . Thus, when the alarm relay  559  is closed, 24 volt A/C power may be delivered to the alarm on the A2L control board  550 , which powers at least the buzzer  562  and the LED  563  on. Further, when the alarm relay  559  is open, no power is delivered to the alarm on the A2L control board and it remains powered off. Additionally, as depicted in  FIG.  5   , in one or more embodiments, the default state for the alarm relay  559  is to be closed. 
     Lastly, in one or more embodiments, the dry contact relay  564  may be electrically disposed between the power supply and a ventilator (not shown) if the HVAC system  500  includes a ventilator, which is electrically coupled to the A2L control board  550  by way of the first and second ventilator contact points  565   a  and  565   b . Thus, when the dry contact relay  564  is closed, 24 volt A/C power may be delivered to the ventilator, which powers the ventilator on. Further, when the dry contact relay  564  is open, no power is delivered to the ventilator and it remains powered off. Additionally, as depicted in  FIG.  5   , in one or more embodiments, the default state for the dry contact relay  564  is to be closed. 
     Further, in one or more embodiments, once the system is turned on, the A2L control board  550  may be configured to open all relays except for the R wire relay  553 , which may be configured to be closed so as to provide the 24 volt A/C power to the thermostat  540  and power the thermostat  540  on. Furthermore, as discussed above, in one or more embodiments, the A2L control board  550  may be configured to act as a passthrough for any signals the thermostat sends during operation of the system. By way of example only, if the HVAC system  500  is required to cool the inside of a building, the thermostat may send signals along both the G and Y1 wires to the A2L control board  550 . The A2L control board  550  may be configured to receive those signals and correspondingly close the G wire relay  554  and the Y1 wire relay  557  such that a 24 volt A/C signal may be passed to the indoor control board  526  along the G wire and the Y1 wire. Once received, the indoor control board  526  may be configured to turn on the blower motor  523  and run the cooling system as is called for by a signal on the G wire and Y1 wire. 
     Further, in one or more embodiments, the power supply may be coupled to the first sensor connector  560  and the second sensor connector  561 , separately. Thus, in one or more embodiments, the A2L control board  550  may separately test one or more A2L sensors  570  before closing the R wire relay  553  and powering up the thermostat  540  and the outdoor unit  530 . This allows for the A2L control board  550  to make sure that the sensors  570  are working properly and there are no A2L refrigerant leaks before beginning the system. While two separate sensor connectors are depicted, one of ordinary skill in the art would understand that the A2L control board may instead include a sensor signal-in contact and a sensor signal-out contact and the one or more sensors may be run in series instead of in parallel. 
     Thus, when the A2L control board  550  receives a signal from the A2L sensor  570  that there is an A2L refrigerant leak, the A2L control board  550  may be configured to carry out the required safety measures required by A2L safety standards. More specifically, in one or more embodiments, if a leak is detected, the A2L control board  550  may be configured to cut off power to the thermostat  540 , and thus, to the outdoor unit  530 , by opening the R wire relay  553 . Further, if a leak is detected, the A2L control board  550  may be configured to cut off power to all parts of the indoor unit  520  except the blower motor  523  by opening at least the W1 wire relay  555  and the W2 wire relay  556  and closing at least the G wire relay  554 . Opening the W1 wire relay  555  and the W2 wire relay  556  will ensure that all heating functions are shut off, while closing the G wire relay  554  will ensure that the blower motor  523  is turned on. In one or more embodiments, the Y1 wire relay  557  and the Y2 wire relay  558  may also be closed as cutting power to the outdoor unit  530  ensures that all cooling functionality is shut off, but the signal on the Y1 and Y2 wire cause the indoor control board  526  to turn up the speed on the blower motor  523  so it blows more air, faster. This allows the HVAC system  500  to meet the A2L safety requirements within the requisite time after detection of an A2L refrigerant leak. 
     Additionally, in one or more embodiments, if a leak is detected, the A2L control board  550  may close the alarm relay  559  and the dry contact relay  564 . Closing the alarm relay  559  will cause the alarm on the A2L control panel  550  to be powered on, which will include, at least, turning on the buzzer  562  and the LED  563  to give auditory and visual alerts that a leak has been detected. Further, if the HVAC system  500  includes a ventilator, closing the dry contact relay  564  will cause the ventilator to be powered on, which will aid in removing any concentrations of A2L refrigerant leaked into the HVAC system  500 . 
     Further, in one or more embodiments, if the A2L control board  550  fails, the relays all revert to their default state. As discussed above and as depicted in  FIG.  5   , in a default state, the G wire relay  554 , the Y1 wire relay  557 , the Y2 wire relay  558 , the alarm relay  559 , and the dry contact relay  564  may be closed, while the R wire relay  553 , the W1 wire relay  555 , and the W2 wire relay  556  may be open. Thus, if the A2L control board  550  fails, power will be blocked from the thermostat  540 , and thus, from the outdoor unit  530  and the only signals the indoor unit  520  will receive and act on will cause the blower motor  523  to be turned on as fast as it can go. Additionally, if the A2L control board  550  fails, the alarm will be turned on and the ventilator will be turned on. 
     Referring now to  FIG.  6   , a flow chart of an embodiment of a method  600  of installing and operating a non-communicating HVAC system using an A2L refrigerant as described above with respect to  FIG.  5   , according to one or more embodiments, is illustrated. Beginning with an HVAC system  500  in which the indoor unit  520  has been disposed on an inside  511  of a building  510 , the outdoor unit  530  has been disposed on an outside  512  of the building  510 , the indoor control board  526  has been electrically coupled to a blower motor  523  of the blower  521 , and the outdoor control board  531  has been electrically coupled to the thermostat  540 , the method  600  may include one or more of the following: (step  610 ) installing the A2L control board  550  and the A2L sensor  570  into the HVAC system  500 , (step  620 ) testing the A2L sensor  570 , (step  630 ) beginning operation of the HVAC system  500 , (step  640 ) checking for A2L refrigerant leaks, and (step  650 ) performing safety measures upon detecting an A2L refrigerant leak. 
     At step  610 , an A2L control board  550  and an A2L sensor  570  may be installed into the HVAC system  500 . Installation of the A2L control board  550  and the A2L sensor  570  may include, at least, (step  611 ) physically coupling the A2L sensor  570  to the indoor evaporator coil  524  of the indoor unit  520 , (step  612 ) electrically coupling the A2L sensor  570  to the A2L control board  550 , (step  613 ) electrically coupling the A2L control board  550  to the indoor control board  526 , (step  614 ) electrically coupling the A2L control board  550  to the thermostat  540 , and (step  615 ) turning on the A2L control board  550  and opening the G wire relay  554 , the Y1 wire relay  557 , the Y2 wire relay  558 , the alarm relay  559 , and the dry contact relay  564 . 
     In one or more embodiments, at step  611 , the A2L sensor  570  may be disposed within the indoor unit  520  such that it is adjacent or connected to the indoor evaporator coil  524  such that the A2L sensor  570  is able to detect an A2L refrigerant leak if one occurs. Further, at step  612 , the A2L sensor  570  may be electrically coupled to the A2L control board  550  such that the A2L sensor  570  and the A2L control board  550  have two-way communication between them. By way of example, in one or more embodiments, an A2L sensor  570  may be electrically coupled to a first sensor connector  557  of the A2L control board  550  by way of an RS-485 bus. One of ordinary skill in the art would appreciate that in other embodiments, any other electric coupling that allows for two-way communication between the A2L sensor  570  and the A2L control board  550  may be used. 
     At step  613 , the A2L control board  550  may be electrically coupled to the indoor control board  526 . In one or more embodiments, R, C, G, W1, W2, Y1, Y2, O, and Dehum wires may be electrically coupled on one end to a terminal block within the indoor control board  526  and on the other end to the second terminal block  552  of the A2L control board  550 . Further, at step  614 , the A2L control board  550  may be electrically coupled to the thermostat  540 . In one or more embodiments, R, C, G, W1, W2, Y1, Y2, O, and Dehum wires may be electrically coupled on one end to a terminal block within the thermostat  540  and on the other end to the first terminal block  551  of the A2L control board  550 . Thus, in one or more embodiments, the A2L control board  550  may be configured to receive control signals from the thermostat  540  and send those same control signals to the indoor control board  526 . Further, in one or more embodiments, the A2L control board  550  may be configured to provide power to the thermostat  540  by way of the R wire so as to power on the thermostat, which in turn powers on the outdoor unit  530 . In one or more embodiments, the power provided to the thermostat  540  by the A2L control board  550  is a 24 volt A/C power. 
     At step  615 , the A2L control board  550  may be turned on, and the G wire relay  554 , the Y1 wire relay  557 , the Y2 wire relay  558 , the alarm relay  559 , and the dry contact relay  564  may be opened. In one or more embodiments, when the A2L control board  550  is turned on, the relays are in the default state, which includes the G wire relay  554 , the Y1 wire relay  557 , the Y2 wire relay  558 , the alarm relay  559 , and the dry contact relay  564  being closed. Thus, in order to make sure signals are not unnecessarily provided to the indoor control board  526  to turn on the blower motor  523  and the alarm and ventilator are not unnecessarily run, in one or more embodiments, when the A2L control board  550  powers up, the A2L control board opens the G wire relay  554 , the Y1 wire relay  557 , the Y2 wire relay  558 , the alarm relay  559 , and the dry contact relay  564 . 
     At step  620 , the A2L sensor  570  may be tested to confirm that it is properly operational. Once electrically coupled to the A2L control board  550 , in one or more embodiments, the A2L sensor  570  may perform an internal diagnostic check to make sure that the sensor is operating properly and may detect an A2L refrigerant leak. If the diagnostic check is successful, the A2L sensor  570  may communicate the successful diagnostic check to the A2L control board  550 , which can begin operation of the HVAC system  500 . If the A2L sensor  570  fails the diagnostic check, the A2L sensor  570  will communicate the failed diagnostic check to the A2L control board  550 , which will remain in the default configuration, keeping the HVAC system  500  from operating until the A2L sensor is repaired or replaced. 
     At step  630 , the A2L control board  550  may begin operation of the HVAC system  500 . In order to begin operation, in one or more embodiments, the A2L control board  550  may close the R wire relay  553  of the A2L control board  550 . Closing the R wire relay  553  allows for the 24 volt A/C power of the A2L control board  550  to pass to the thermostat  540  and therefrom to the outdoor unit  530 . Once power has been turned on for the thermostat  540 , it may then be able to send signals to the indoor unit  520 , through the A2L control board  550 , as well as to the outdoor unit  530  and the HVAC system  500  may be fully operational. 
     At step  640 , while the HVAC system is running, in one or more embodiments, the A2L sensor  570  may check for A2L refrigerant leaks. The A2L sensor  570  may continuously check for A2L refrigerant leaks while the HVAC system  500  is running, such that if a check comes back negative for an A2L refrigerant leak, the A2L sensor  570  repeats step  640 . However, if the AL2 sensor  570  detects an A2L leak, then the A2L sensor  570  communicates the A2L refrigerant leak to the A2L control board and the HVAC system continues to step  650 . 
     At step  650 , the HVAC system  500 , by way of the A2L control board  550 , may perform safety measures to eliminate the threat of the detected A2L refrigerant leak. Specifically, the HVAC system  500  may (step  652 ) open the R wire relay  553 , (step  653 ) close the G wire relay  554 , (step  654 ) open the W1 wire relay  555  and the W2 wire relay  556 , (step  655 ) close the Y1 wire relay  557  and the Y2 wire relay  558 , (step  656 ) close the dry contact relay  564 , and (step  657 ) close the alarm relay  559 . 
     At step  652 , opening the R wire relay  553  prevents the A2L control board  550  from distributing the 24 volt A/C power to the thermostat  540 . Removing the 24 volt A/C power from the thermostat  540  in turn removes power from the outside unit  530 , which is configured to receive 24 volt A/C power signals directly from the thermostat. Additionally, at step  653 , closing the G wire relay  554  causes the A2L control board  550  to send a 24 volt A/C power along the G wire to the inside control board  526 , which starts the blower motor  523  when it receives the signal along the G wire. Further, at step  654 , opening the W1 wire relay  555  and the W2 wire relay  556  ensures that no signal is sent to the indoor control board  526  and thus, heating operations are not run while the system is experiencing a refrigerant leak. Furthermore, at step  655 , closing the Y1 wire relay  557  and the Y2 wire relay  558  causes the A2L control board  550  to send a 24 volt A/C power along the Y1 and Y2 wires to the indoor control board  526 . The indoor control board  526  interprets the signals along the Y1 and Y2 wires to call for first and second stage cooling operations, but because the compressor in the outdoor unit  530  is powered off, the only effect is that the indoor control board  526  runs the blower motor  532  at its highest level. 
     Further, at step  656 , closing the dry contact relay  564  causes the 24 volt A/C power from the A2L control board  550  to power an attached ventilator on if the HVAC system  500  includes a ventilator. Additionally, at step  657 , closing the alarm relay  559  causes the 24 volt A/C power from the A2L control board  550  to power the alarm on, which includes, at least, powering on visual and auditory alarms in the form of the buzzer  562  and the LED  563 . 
     Further, while listed as separate steps, one of ordinary skill would appreciate that in one or more embodiments, steps  652 - 657  may take place in any order, or in other embodiments, steps  652 - 657  may occur simultaneously. Additionally, one of ordinary skill in the art would appreciate that all steps  652 - 657  may be completed within the requisite time after detection of an A2L refrigerant leak as required by A2L safety standards. 
     Thus, in one or more embodiments, in response to a communication from the A2L sensor  570  that an A2L refrigerant leak has been detected, the A2L control board  550  may turn off the outdoor unit  530 , turn on a ventilator if the HVAC system  500  has one, turn on visual and auditory alarms that an A2L refrigerant has been detected, and ensure that the only signals the indoor unit  520  will receive and act on will cause the blower motor  523  to be turned on as fast as it can go. 
     While the method  600  is described with respect to an HVAC system  500  including a single A2L sensor  570 , one of ordinary skill in the art, would understand that any number of sensors may be used in the system and the method may include electrically coupling the further sensors to the control board, testing the further sensors, and communicating with the further sensors as the further sensors check for A2L refrigerant leaks. 
       FIG.  7    shows a communicating HVAC system using an A2L refrigerant, according to a one or more embodiments. In one or more embodiments, an HVAC system  700  may be used to distribute cooled or heated air throughout a building  710  to adjust the ambient air temperature inside  711  of the building  710 . The HVAC system may include an indoor unit  720 , an outdoor unit  730 , a thermostat  740 , an A2L control board  750 , an A2L sensor  770 , an outdoor relay  780 , and a high pressure switch  790 . 
     Generally, in one or more embodiments, the indoor unit  720  may be fluidly coupled to the outdoor unit  730  such that an A2L refrigerant may flow between the indoor unit  720  and the outdoor unit  730  to cool or heat air within the indoor unit  720 . Further, in one or more embodiments, both the indoor unit  720  and the outdoor unit  730  may be communicatively coupled to each other by way of an RS-485 system communication. Furthermore, in one or more embodiments, the A2L control board  750  may be directly electrically and/or communicatively coupled to both the indoor unit  720  and the thermostat  740 , and also indirectly electrically coupled to the outdoor unit  730  by way of the outdoor relay  780  and the high pressure switch  790 . The thermostat  740  may be electrically coupled to the A2L control board  750  such that it may send communications and signals to the indoor unit  720  through the A2L control board  750 . Thus, the A2L control board  750  may be configured to directly affect the operation of the indoor unit  720  by way of those communications and signals and may be configured to directly affect the operation of the outdoor unit  730  by way of the outdoor relay  780  and the high pressure switch  790 . Further, the A2L sensor  770  may be physically disposed within the indoor unit  720  and electrically coupled to the A2L control board  750 . The A2L sensor  770  may be configured to send signals to the A2L control board  750  when an A2L refrigerant leak is detected. 
     While the A2L control board  750  is depicted as being electrically and communicatively coupled to the indoor unit  720 , the thermostat  740 , and the A2L sensor  770  by way of a wired connection, one of ordinary skill in the art would understand that the indoor unit  720 , the thermostat  740 , and the A2L sensor  770  may just be communicatively coupled to the A2L control board  750  wirelessly. In one or more embodiments, the indoor unit  720 , the thermostat  740 , and the A2L sensor  770  may be communicatively coupled to the A2L control board  750  by any wireless means, such as Wi-Fi or Bluetooth. 
     In one or more embodiments, indoor unit  720  may be disposed on the inside  711  of the building  710 . The indoor unit  720  may be configured to distribute cooled or heated air to rooms on the inside  711  of the building  710 . The indoor unit  720  may be any type of HVAC system that includes a blower  721  and a heat exchanger  727  having an indoor evaporator coil  724 . Thus, in one or more embodiments, the indoor unit  720  may be either a furnace or an air handler, as both types of system include, at least, a blower and an indoor evaporator coil. Additionally, the indoor evaporator coil  724  may be disposed adjacent to the blower  721 , such that when the blower  721  blows air within the indoor unit  720 , the air is blown through the evaporator coil  724 . 
     Further, in one or more embodiments, the blower  721  may include a blower fan  722  and a blower motor  723 . By way of example, in one or more embodiments, the blower motor  723  may be constant torque motor, while in other embodiments, the blower motor  723  may be a permanent split capacitor (PSC) motor. The blower motor  723  may be mechanically coupled to the blower fan  722  such that when the blower motor  723  is turned on, the blower fan  722  is configured to spin and cause a movement of air out from the blower  721  and through the indoor evaporator coil  724 . The indoor evaporator coil  724  may be configured to receive the A2L refrigerant on the inside of the coil while air from the blower  721  is blown across the outside of the coil, which allows for heat to exchange either from the A2L refrigerant to the air or vice versa. The A2L refrigerant, after cooling or heating the air, may be cycled back to the outdoor unit  730 , where it will go through the reverse heat exchange process before returning to the indoor evaporator coil  724 . Additionally, indoor unit  720  is configured to distribute the air that is blown from the blower  721  and across the indoor evaporator coil  724  to the rooms on the inside  711  of the building  710  by way of the force of the blower  721 . 
     The indoor unit  720  may also include a transformer  725  and an indoor control board  726 . The transformer  725  may be directly electrically coupled to and configured to provide 24 volts A/C power to the indoor control board  726 . Further, the indoor control board  726  may be electrically coupled to, at least, the A2L control board  750  and the blower motor  723 . 
     Further, the outdoor unit  730  may be disposed on an outside  712  of the building  710  and be configured to use the outdoor environment to reheat or cool down the A2L refrigerant after it has been run through the indoor evaporator coil  724 . The outdoor unit  730  may include, but is not limited to, either a heat pump or an air conditioner. Whether the outdoor unit  730  is a heat pump or an air conditioner, the outdoor unit  730  may include a compressor (not shown), an outdoor coil (not shown), and an outdoor control board  731 . The outdoor unit  730  may be configured to communicate with the indoor unit  720  through RS-485 system communication between the indoor control board  726  and the outdoor control board  731 . Further, the outdoor control board  731  may be electrically coupled to the A2L control board  750  as discussed below. 
     Still referring to  FIG.  7   , in one or more embodiments, the A2L sensor  770  may be configured to detect an A2L refrigerant leak and send a signal reporting as much. In one or more embodiments, the A2L sensor  770  may be configured to detect an A2L refrigerant leak by one of a number of methods, including, at least, by detecting an amount or a concentration of A2L refrigerant in the air that exceeds a leak threshold. The A2L sensor  770  may be electrically coupled to and communicate with the A2L control board  750 . In one or more embodiments, the A2L sensor  770  may be electrically coupled to the A2L control board  750  by way of a first sensor connector  760 . The A2L sensor  770  may be configured to communicate to the A2L control board  750  that the A2L sensor  770  is connected to the system and working properly. Additionally, when the A2L sensor  770  detects an A2L refrigerant leak, it may communicate the A2L refrigerant leak to the A2L control board  750 , which may be configured to receive the signal and perform the safety measures required by A2L safety standards. In one or more embodiments, the A2L sensor  770  and the A2L control board  750  may be electrically coupled by way of an RS-485 bus; however, one of ordinary skill in the art would understand that any type of electrical connection that allows the A2L sensor  770  to send a signal to the A2L control board  750  may be used. 
     Further, in one or more embodiments, the A2L sensor  770  may be disposed within the indoor unit  720  so that it may detect an A2L refrigerant leak that occurs within the indoor evaporator coil  724  of the HVAC system  700 . As depicted, in one or more embodiments, the A2L sensor  770  may be disposed directly against the indoor evaporator coil to minimize the time it takes for the A2L sensor  770  to detect an A2L refrigerant leak. Further, while the A2L sensor  770  is depicted within the indoor unit  720 , one or ordinary skill in the art would understand that the A2L sensor  770  may instead be disposed within the outdoor unit  730 . Further, while a single sensor is depicted, one of ordinary skill in the art would understand that multiple sensors may be incorporated into the HVAC system to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. For example, one of ordinary skill in the art would understand that the HVAC system may include two A2L sensors, with both A2L sensors disposed within the indoor unit, both A2L sensors disposed within the outdoor unit, or one A2L sensor disposed within each of the indoor unit and the outdoor unit. Thus, one of ordinary skill in the art would understand that in one or more embodiments, a plurality of A2L sensors may be disposed within the HVAC system with one or more A2L sensors disposed within the indoor unit and/or one or more A2L sensors disposed within the outdoor unit as may be determined necessary to ensure that an A2L refrigerant leak is detected and the required safety measures are taken within the time required by A2L safety standards. 
     Additionally, referring to  FIG.  7   , in one or more embodiments, the A2L control board  750  may be disposed inside of the indoor unit  720 . However, one of ordinary skill in the art would understand that, in one or more embodiments, the A2L control board  750  may be disposed outside of the indoor unit  720  and either connected to the indoor unit  720  or adjacent to the indoor unit  720 . Further, in addition to being electrically coupled to the indoor control board  726 , the thermostat  740 , and the A2L sensor  770 , as discussed above, the A2L control board  750  may be electrically coupled to the outdoor control board  731  by way of the outdoor relay  780  and the high pressure switch  790 . In one or more embodiments, the outdoor relay  780  and the high pressure switch  790  may be electrically coupled in series between the A2L control board  750  and the outdoor control board  731 . In one or more embodiments, the outdoor relay  780  may be directly electrically coupled to the A2L control board  750  such that the outdoor relay  780  is configured to open upon receiving a 24 volt A/C power signal from the A2L control board  750 . Further, in one or more embodiments, the high pressure switch  790  is electrically coupled to the outdoor control board  731  such that when the high pressure switch  790  opens, the outdoor unit  730  shuts down completely. Furthermore, in one or more embodiments, opening the outdoor relay  780  causes the high pressure switch  790  to open, which causes the outdoor unit  730  to shut down completely. 
     In one or more embodiments, the A2L control board  750  may include a power supply (not shown), a first terminal block  751 , a second terminal block  752 , an R wire relay  753 , an G wire relay  754 , a W1 wire relay  755 , a W2 wire relay  756 , a Y1 wire relay  757 , a Y2 wire relay  758 , an alarm relay  759 , a first sensor connector  760 , a second sensor connector  761 , a buzzer  762 , an LED  763 , a dry contact relay  764 , first and second ventilator contact points  765   a  and  765   b , and an outdoor unit relay  766 . The power supply may be coupled to circuitry on the A2L control board  750  such that the A2L control board may open and close, at least, the R wire relay  753 , the G wire relay  754 , the W1 wire relay  755 , the W2 wire relay  756 , the Y1 wire relay  757 , the Y2 wire relay  758 , the alarm relay  759 , the dry contact relay  764  and the outdoor unit relay  766 . 
     In one or more embodiments, the thermostat  740  may be electrically coupled to the first terminal block  751 , and the indoor control board  726  may be electrically coupled to the second terminal block  752 . Further, in one or more embodiments, any signals received by the A2L control board  750  from the thermostat  740  may be passed unchanged, by the A2L control board  750 , to the indoor control board  730  through the second terminal block  752 . 
     In one or more embodiments, the R wire relay  753  may be electrically disposed between the power supply and the R wire connection of the first terminal block  751 . Thus, when the R wire relay  753  is closed, 24 volt A/C power may be delivered from the A2L control board  750  to the thermostat  740  via the first terminal block  751 , which powers the thermostat  740  on. Further, when the R wire relay  753  is open, no power is able to reach the thermostat, and thus, the thermostat is turned off completely. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default state for the R wire relay  753  is to be open. 
     In one or more embodiments, the G wire relay  754  may be electrically disposed between the power supply and the G wire connection of the second terminal block  752 . Thus, when the G wire relay  754  is closed, 24 volt A/C power may be delivered from the A2L control board  750  to the indoor control board  726  via the first terminal block  751 , which signals the indoor control board  726  to power the blower motor  723  on. Further, when the G wire relay  754  is open, no signal is sent along the G wire to the indoor control board  726 , and thus, the blower motor  723  is powered off. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default state for the G wire relay  754  is to be closed. 
     In one or more embodiments, the W1 wire relay  755  may be electrically disposed between the power supply and the W1 wire connection of the second terminal block  752 , and the W2 wire relay  756  may be electrically disposed between the power supply and the W2 wire connection of the second terminal block  752 . Thus, when the W1 wire relay  755  and the W2 wire relay  756  are closed, 24 volt A/C power may be delivered from the A2L control board  750  to the indoor control board  726  via the first terminal block  751 , which signals the indoor control board  726  to run the heating system&#39;s first and second stages, respectively. Further, when the W1 wire relay  755  and W2 wire relay  756  are open, no signal is sent along the W1 or W2 wires to the indoor control board  726 , and thus, the heating system is powered off. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default states for the W1 wire relay  755  and the W2 wire relay  756  are to be open. 
     In one or more embodiments, the Y1 wire relay  757  may be electrically disposed between the power supply and the Y1 wire connection of the second terminal block  752 , and the Y2 wire relay  758  may be electrically disposed between the power supply and the Y2 wire connection of the second terminal block  752 . Thus, when the Y1 wire relay  757  and the Y2 wire relay  758  are closed, 24 volt A/C power may be delivered from the A2L control board  750  to the indoor control board  726  via the first terminal block  751 , which signals the indoor control board  726  to run the cooling system&#39;s first and second stages, respectively. Further, when the Y1 wire relay  757  and Y2 wire relay  758  are open, no signal is sent along the Y1 or Y2 wires to the indoor control board  726 , and thus, the cooling system is powered off. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default states for the Y1 wire relay  757  and the Y2 wire relay  758  are to be closed. 
     Further, in one or more embodiments, the alarm relay  759  may be electrically disposed between the power supply and an alarm (not shown), which includes, in part, the buzzer  762  and the LED  763 . Thus, when the alarm relay  759  is closed, 24 volt A/C power may be delivered to the alarm on the A2L control board  750 , which powers at least the buzzer  762  and the LED  763  on. Further, when the alarm relay  759  is open, no power is delivered to the alarm on the A2L control board and it remains powered off. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default state for the alarm relay  759  is to be closed. 
     Furthermore, in one or more embodiments, the dry contact relay  764  may be electrically disposed between the power supply and a ventilator (not shown) if the HVAC system  700  includes a ventilator, which is electrically coupled to the A2L control board  750  by way of the first and second ventilator contact points  765   a  and  765   b . Thus, when the dry contact relay  764  is closed, 24 volt A/C power may be delivered to the ventilator, which powers the ventilator on. Further, when the dry contact relay  764  is open, no power is delivered to the ventilator and it remains powered off. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default state for the dry contact relay  764  is to be closed. 
     Additionally, in one or more embodiments, the outdoor unit relay  766  may be electrically disposed between the power supply and an outdoor unit contact point  767 . In one or more embodiments, the outdoor relay  780  may be electrically coupled to the A2L control board  750  by way of the outdoor unit contact point  767 . Thus, when the outdoor unit relay  766  is closed, 24 volt A/C power may be delivered to the outdoor relay  780  causing it to open, thus opening the high pressure switch  790  and shutting off the outdoor unit  730 . Further, when the outdoor unit relay  766  is open, no power is delivered to the outdoor relay  780  and the outdoor unit  730  continues to operate. Additionally, as depicted in  FIG.  7   , in one or more embodiments, the default state for the outdoor unit relay  766  is to be closed. 
     Further, in one or more embodiments, once the system is turned on, the A2L control board  750  may be configured to open all relays except for the R wire relay  753 , which may be configured to be closed so as to provide the 24 volt A/C power to the thermostat  740  and power the thermostat  740  on. Furthermore, as discussed above, in one or more embodiments, the A2L control board  750  may be configured to act as a passthrough for any signals the thermostat sends during operation of the system. By way of example only, if the HVAC system  700  is required to cool the inside of a building, the thermostat may send signals along both the G and Y1 wires to the A2L control board  750 . The A2L control board  750  may be configured to receive those signals and correspondingly close the G wire relay  754  and the Y1 wire relay  757  such that a 24 volt A/C signal may be passed to the indoor control board  726  along the G wire and the Y1 wire. Once received, the indoor control board  726  may be configured to turn on the blower motor  723  and run the cooling system as is called for by a signal on the G wire and Y1 wire. 
     Further, in one or more embodiments, the power supply may be coupled to the first sensor connector  760  and the second sensor connector  761 , separately. Thus, in one or more embodiments, the A2L control board  750  may separately test one or more A2L sensors  770  before closing the R wire relay  753  and powering up the thermostat  740 . This allows for the A2L control board  750  to make sure that the sensors  770  are working properly and there are no A2L refrigerant leaks before beginning the system. While two separate sensor connectors are depicted, one of ordinary skill in the art would understand that the A2L control board may instead include a sensor signal-in contact and a sensor signal-out contact and the one or more sensors may be run in series instead of in parallel. 
     Thus, when the A2L control board  750  receives a signal from the A2L sensor  770  that there is an A2L refrigerant leak, the A2L control board  750  may be configured to carry out the required safety measures required by A2L safety standards. More specifically, in one or more embodiments, if a leak is detected, the A2L control board  750  may be configured to cut off power to the thermostat  740  by opening the R wire relay  753  and to cause the outdoor unit  730  to turn off by closing the outdoor unit relay  766 . Further, if a leak is detected, the A2L control board  750  may be configured to cut off power to all parts of the indoor unit  720  except the blower motor  723  by opening at least the W1 wire relay  755  and the W2 wire relay  756  and closing at least the G wire relay  754 . Opening the W1 wire relay  755  and the W2 wire relay  756  will ensure that all heating functions are shut off, while closing the G wire relay  754  will ensure that the blower motor  723  is turned on. In one or more embodiments, the Y1 wire relay  757  and the Y2 wire relay  758  may also be closed as cutting power to the outdoor unit  730  ensures that all cooling functionality is shut off, but the signal on the Y1 and Y2 wire may cause the indoor control board  726  to turn up the speed on the blower motor  723  so it blows more air, faster. Further, closing the outdoor unit relay  766  in response to an A2L refrigerant leak being detected causes power to be directly applied to the outdoor relay  780 . Directly applying power to the outdoor relay  780  causes the outdoor relay  780  to open. Furthermore, opening the outdoor relay  780  is configured to cause the high pressure switch  790  to open. Additionally, the outdoor unit  730  is configured to shut down completely if the high pressure switch  790  is opened. Thus, closing the outdoor unit relay  766  is configured to shut down the outdoor unit  730  completely. This allows the HVAC system  700  to meet the A2L safety requirements within the requisite time after detection of an A2L refrigerant leak. 
     While  FIG.  7    depicts one or more embodiments of the present invention that utilize an outdoor relay  780  and a high pressure switch  790  in order to shut off the outdoor unit in the event of an A2L refrigerant leak, one of ordinary skill in the art would understand that any means of turning off the compressor of the outdoor unit would work to properly meet the A2L safety requirements. By way of example, in one or more embodiments, the HVAC system may include an A2L control board that is electrically coupled to a contactor, where the contactor is configured to contact the outdoor control board such that the outdoor unit shuts off in the event of an A2L refrigerant leak being detected. Further, in other embodiments, the A2L control board may be communicatively coupled to the outdoor control board by way of an RS-485 system communication such that the A2L control board can tell the outdoor control board to shut down the outdoor unit in the event of an A2L leak being detected. Furthermore, in one or more embodiments, the A2L control board may be electrically coupled to a relay, where the relay is disposed between the outdoor control board and the compressor of the outdoor unit such that when the relay is opened, power from the outdoor control board does not reach the compressor, and the compressor shuts down. 
     Further, while in one or more embodiments a 24 volt A/C signal is used by the A2L control board to communicate with the outdoor relay to shut down the outdoor unit, one of ordinary skill in the art would understand that, in one or more embodiments, the A2L control board may send digital signals to the outdoor relay. One of ordinary skill in the art would understand that digital signals may also be used with a contactor or any other relay coupled to the outdoor control board to shut down the outdoor unit. Furthermore, in one or more embodiments, the A2L control board may be wirelessly, communicatively coupled to the outdoor control board such that wireless signals may be used to turn off the outdoor unit. 
     Additionally, in one or more embodiments, if a leak is detected, the A2L control board  750  may close the alarm relay  759  and the dry contact relay  764 . Closing the alarm relay  759  will cause the alarm on the A2L control panel  750  to be powered on, which will include, at least, turning on the buzzer  762  and the LED  763  to give auditory and visual alerts that a leak has been detected. Further, if the HVAC system  700  includes a ventilator, closing the dry contact relay  764  will cause the ventilator to be powered on, which will aid in removing any concentrations of A2L refrigerant leaked into the HVAC system  700 . 
     Further, in one or more embodiments, if the A2L control board  750  fails, the relays all revert to their default state. As discussed above and as depicted in  FIG.  7   , in a default state, the G wire relay  754 , the Y1 wire relay  757 , the Y2 wire relay  758 , the alarm relay  759 , the dry contact relay  764 , and the outdoor unit relay  766  may be closed, while the R wire relay  753 , the W1 wire relay  755 , and the W2 wire relay  756  may be open. Thus, if the A2L control board  750  fails, the outdoor unit  730  will be shut down by way of the opened high pressure switch, and the only signals the indoor unit  720  will receive and act on will cause the blower motor  723  to be turned on as fast as it can go. Additionally, if the A2L control board  750  fails, the alarm will be turned on and the ventilator will be turned on. 
     Referring now to  FIG.  8   , a flow chart of an embodiment of a method  800  of installing and operating a communicating HVAC system using an A2L refrigerant as described above with respect to  FIG.  7   , according to one or more embodiments, is illustrated. Beginning with an HVAC system  700  in which the indoor unit  720  has been disposed on an inside  711  of a building  710 , the outdoor unit  730  has been disposed on an outside  712  of the building  710 , the indoor control board  726  has been electrically coupled to the transformer  725  and a blower motor  723  of the blower  721 , and the outdoor control board  731  has been communicatively coupled to the indoor control board  726 , the method  800  may include one or more of the following: (step  810 ) installing the A2L control board  750  and the A2L sensor  770  into the HVAC system  700 , (step  820 ) testing the A2L sensor  770 , (step  830 ) beginning operation of the HVAC system  700 , (step  840 ) checking for A2L refrigerant leaks, and (step  850 ) performing safety measures upon detecting an A2L refrigerant leak. 
     At step  810 , an A2L control board  750  and an A2L sensor  770  may be installed into the HVAC system  700 . Installation of the A2L control board  750  and the A2L sensor  770  may include, at least, (step  811 ) physically coupling the A2L sensor  770  to the indoor evaporator coil  724  of the indoor unit  720 , (step  812 ) electrically coupling the A2L sensor  770  to the A2L control board  750 , (step  813 ) electrically coupling the A2L control board  750  to the indoor control board  726 , (step  814 ) electrically coupling the A2L control board  750  to outdoor control board  731 , (step  815 ) electrically coupling the A2L control board  750  to the thermostat  740 , and (step  816 ) turning on the A2L control board  750  and opening the G wire relay  754 , the Y1 wire relay  757 , the Y2 wire relay  758 , the alarm relay  759 , the dry contact relay  764 , and the outdoor unit relay  766 . 
     In one or more embodiments, at step  811 , the A2L sensor  770  may be disposed within the indoor unit  720  such that it is adjacent or connected to the indoor evaporator coil  724  such that the A2L sensor  770  is able to detect an A2L refrigerant leak if one occurs. Further, at step  812 , the A2L sensor  770  may be electrically coupled to the A2L control board  750  such that the A2L sensor  770  and the A2L control board  750  have two-way communication between them. By way of example, in one or more embodiments, an A2L sensor  770  may be electrically coupled to a first sensor connector  757  of the A2L control board  750  by way of an RS-485 bus. One of ordinary skill in the art would appreciate that in other embodiments, any other electric coupling that allows for two-way communication between the A2L sensor  770  and the A2L control board  750  may be used. 
     At step  813 , the A2L control board  750  may be electrically coupled to the indoor control board  726 . In one or more embodiments, R, C, G, W1, W2, Y1, Y2, O, and Dehum wires may be electrically coupled on one end to a terminal block within the indoor control board  726  and on the other end to the second terminal block  752  of the A2L control board  750 . Further, at step  815 , the A2L control board  750  may be electrically coupled to the thermostat  740 . In one or more embodiments, R, C, G, W1, W2, Y1, Y2, O, and Dehum wires may be electrically coupled on one end to a terminal block within the thermostat  740  and on the other end to the first terminal block  751  of the A2L control board  750 . Thus, in one or more embodiments, the A2L control board  750  may be configured to receive control signals from the thermostat  740  and send those same control signals to the indoor control board  726 . Further, in one or more embodiments, the A2L control board  750  may be configured to provide power to the thermostat  740  by way of the R wire so as to power on the thermostat  740 . In one or more embodiments, the power provided to the thermostat  740  by the A2L control board  750  is a 24 volt A/C power. 
     At step  814 , the A2L control board  750  may be electrically coupled to the outdoor control board  731 . In one or more embodiments, the high pressure switch  790  may be electrically coupled to the outdoor control board  731  such that when the high pressure switch  790  opens, the outdoor control board  731  shuts down. Further, the outdoor relay  780  may be electrically coupled to the high pressure switch  790  such that when the outdoor relay opens, the high pressure switch opens. Furthermore, the outdoor relay  780  may be electrically coupled to an outdoor unit contact point  767  of the A2L control board  750  by way of a wire capable of carrying 24 volt A/C power. Thus, by way of example, if outdoor unit relay  766  of the A2L control board  750  closes, a 24 volt A/C signal will be provided to the outdoor relay  780  which causes the outdoor relay  780  to open, which causes the high pressure switch  790  to open, which shuts down the outdoor unit  730 , including the outdoor control board  731 . 
     At step  816 , the A2L control board  750  may be turned on, and the G wire relay  754 , the Y1 wire relay  757 , the Y2 wire relay  758 , the alarm relay  759 , the dry contact relay  764 , and the outdoor unit relay  766  may be opened. In one or more embodiments, when the A2L control board  750  is turned on, the relays are in the default state, which includes the G wire relay  754 , the Y1 wire relay  757 , the Y2 wire relay  758 , the alarm relay  759 , the dry contact relay  764 , and the outdoor unit relay  766  being closed. Thus, in order to make sure signals are not unnecessarily provided to the indoor control board  726  to turn on the blower motor  723 , the outdoor unit  730  is not unnecessarily shut down by the high pressure switch, and the alarm and ventilator are not unnecessarily run, in one or more embodiments, when the A2L control board  750  powers up, the A2L control board opens the G wire relay  754 , the Y1 wire relay  757 , the Y2 wire relay  758 , the alarm relay  759 , the dry contact relay  764 , and the outdoor unit relay  766 . 
     At step  820 , the A2L sensor  770  may be tested to confirm that it is properly operational. Once electrically coupled to the A2L control board  750 , in one or more embodiments, the A2L sensor  770  may perform an internal diagnostic check to make sure that the sensor is operating properly and may detect an A2L refrigerant leak. If the diagnostic check is successful, the A2L sensor  770  may communicate the successful diagnostic check to the A2L control board  750 , which can begin operation of the HVAC system  700 . If the A2L sensor  770  fails the diagnostic check, the A2L sensor  770  will communicate the failed diagnostic check to the A2L control board  750 , which will remain in the default configuration, keeping the HVAC system  700  from operating until the A2L sensor is repaired or replaced. 
     At step  830 , the A2L control board  750  may begin operation of the HVAC system  700 . In order to begin operation, in one or more embodiments, the A2L control board  750  may close the R wire relay  753  of the A2L control board  750 . Closing the R wire relay  753  allows for the 24 volt A/C power of the A2L control board  750  to pass to the thermostat  740 . Once power has been turned on for the thermostat  740 , it may then be able to send signals to the indoor unit  720 , through the A2L control board  750 , and the HVAC system  700  may be fully operational. 
     At step  840 , while the HVAC system is running, in one or more embodiments, the A2L sensor  770  may check for A2L refrigerant leaks. The A2L sensor  770  may continuously check for A2L refrigerant leaks while the HVAC system  700  is running, such that if a check comes back negative for an A2L refrigerant leak, the A2L sensor  770  repeats step  840 . However, if the AL2 sensor  770  detects an A2L leak, then the A2L sensor  770  communicates the A2L refrigerant leak to the A2L control board and the HVAC system continues to step  850 . 
     At step  850 , the HVAC system  700 , by way of the A2L control board  750 , may perform safety measures to eliminate the threat of the detected A2L refrigerant leak. Specifically, the HVAC system  700  may (step  852 ) open the R wire relay  753 , (step  853 ) close the G wire relay  754 , (step  854 ) open the W1 wire relay  755  and the W2 wire relay  756 , (step  855 ) close the Y1 wire relay  757  and the Y2 wire relay  758 , (step  856 ) close the dry contact relay  764 , (step  857 ) close the alarm relay  759 , and (step  858 ) close the outdoor unit relay  766 . 
     At step  852 , opening the R wire relay  753  prevents the A2L control board  750  from distributing the 24 volt A/C power to the thermostat  740 . Removing the 24 volt A/C power from the thermostat  740  ensures that only the signals passed from the A2L control board  750  may reach the indoor control board  726  and thus, the safety measures may be implemented by the HVAC system  700 . Additionally, at step  853 , closing the G wire relay  754  causes the A2L control board  750  to send a 24 volt A/C power along the G wire to the inside control board  726 , which starts the blower motor  723  when it receives the signal along the G wire. Further, at step  854 , opening the W1 wire relay  755  and the W2 wire relay  756  ensures that no signal is sent to the indoor control board  726  and thus, heating operations are not run while the system is experiencing a refrigerant leak. Furthermore, at step  855 , closing the Y1 wire relay  757  and the Y2 wire relay  758  causes the A2L control board  750  to send a 24 volt A/C power along the Y1 and Y2 wires to the indoor control board  726 . The indoor control board  726  interprets the signals along the Y1 and Y2 wires to call for first and second stage cooling operations, but because the compressor in the outdoor unit  730  is also being powered off in this step as discussed below, the only effect is that the indoor control board  726  runs the blower motor  732  at its highest level. Additionally, at step  858 , closing the outdoor unit relay  766  causes a 24 volt A/C signal to travel to the outdoor relay  780 , which causes the outdoor relay  780  to open, which causes the high pressure switch  790  to open, which causes the outdoor unit  730  to shut down completely. 
     Further, at step  856 , closing the dry contact relay  764  causes the 24 volt A/C power from the A2L control board  750  to power an attached ventilator on if the HVAC system  700  includes a ventilator. Additionally, at step  857 , closing the alarm relay  759  causes the 24 volt A/C power from the A2L control board  750  to power the alarm on, which includes, at least, powering on visual and auditory alarms in the form of the buzzer  762  and the LED  763 . 
     Further, while listed as separate steps, one of ordinary skill would appreciate that in one or more embodiments, steps  852 - 858  may take place in any order, or in other embodiments, steps  852 - 858  may occur simultaneously. Additionally, one of ordinary skill in the art would appreciate that all steps  852 - 858  may be completed within the requisite time after detection of an A2L refrigerant leak as required by A2L safety standards. 
     Thus, in one or more embodiments, in response to a communication from the A2L sensor  770  that an A2L refrigerant leak has been detected, the A2L control board  750  may turn off the outdoor unit  730 , turn on a ventilator if the HVAC system  700  has one, turn on visual and auditory alarms that an A2L refrigerant has been detected, and ensure that the only signals the indoor unit  720  will receive and act on will cause the blower motor  723  to be turned on as fast as it can go. 
     While the method  800  is described with respect to an HVAC system  700  including a single A2L sensor  770 , one of ordinary skill in the art, would understand that any number of sensors may be used in the system and the method may include electrically coupling the further sensors to the control board, testing the further sensors, and communicating with the further sensors as the further sensors check for A2L refrigerant leaks. 
     Referring now to  FIG.  9   , an illustrative configuration of A2L sensors for use in HVAC systems using an A2L refrigerant, according to one or more embodiments is shown. As discussed above, while any ASHRAE Standard 34 classified “A2L” refrigerant may be used, in one or more embodiments, the A2L refrigerant may be R-32 refrigerant. Further, in one or more embodiments, all references to “A2L” may be specifically related to R-32. By way of example, referring to  FIGS.  9  and  10   , an A2L refrigerant may be R-32 refrigerant, an A2L sensor may be an R-32 sensor that is configured to detect amounts of R-32 refrigerant so as to detect an R-32 refrigerant leak, and an A2L control board may be a control board configured to work with R-32 sensors to enact safety measures if an R-32 refrigerant leak is detected. 
     In one or more embodiments, an HVAC system  900  may include, in part, an A2L control board  950  and one or more A2L sensors  970   a ,  970   b ,  970   c . Further, as discussed above with respect to  FIGS.  1 ,  3 ,  5 , and  7   , the A2L sensors  970   a ,  970   b ,  970   c  may be electrically coupled to the A2L control board  950 , such that the A2L sensors  970   a ,  970   b ,  970   c  may communicate an A2L refrigerant leak to the A2L control board  950  if one is detected. Further, in one or more embodiments, an RS-485 4 wire harness may be used to connect, at least, the first A2L sensor  970   a  to a first sensor connector  957  of the A2L control board  950 . Further, while an RS-485 connection may used, one of ordinary skill in the art would understand that any method of communicatively and electrically coupling the A2L sensors to the A2L control board may be used. Additionally, in one or more embodiments, a feedback wire may be used to electrically couple a last A2L sensor  970   c  to a second sensor connector  958  of the A2L control board  950 . 
     While each A2L sensor  970   a ,  970   b ,  970   c  and the A2L control board  950  are depicted as being electrically and communicatively coupled to each other by way of a wired connection, one of ordinary skill in the art would understand that each A2L sensor  970   a ,  970   b ,  970   c  and the A2L control board  950  may just be communicatively coupled wirelessly. In one or more embodiments, each A2L sensor  970   a ,  970   b ,  970   c  and the A2L control board  950  may be communicatively coupled by any wireless means, such as Wi-Fi or Bluetooth. 
     In one or more embodiments, each of the A2L sensors  970   a ,  970   b ,  970   c  may include sensing components  971 , a bus connector input  972 , a bus connector output  973 , a sensor relay  974 , and a sensor feedback port  975 . The sensing components  971  may be configured to detect an A2L gas in the air and report the level detected. Additionally, the sensing components  971  may be configured to run internal diagnostic checks to make sure that the sensor is still operational. 
     Further, the bus connector input  972  and the bus connector output  973  may be physical connectors through which the sensor may be communicatively coupled to another sensor or the A2L control board  950 . By way of example, on the first sensor  970   a , the bus connector input  972  may be where an RS-485 4 wire harness is connected to the first A2L sensor  970   a  such that the first A2L sensor  970   a  is electrically coupled to the A2L control board  950 . Also, by way of example, a bus connector output  973  of the first A2L sensor  970   a  may be where another RS-485 4 wire harness is connected to the first A2L sensor  970   a  such that the first A2L sensor  970   a  is electrically coupled to the second A2L sensor  970   b.    
     Furthermore, in one or more embodiments, each A2L sensor may include a sensor relay  974 . The sensor relay  974  may be electrically disposed between the bus connector input  972  and the bus connector output  973  such that when the sensor relay  974  is open, power is blocked from travelling from the bus connector input  972  to the bus connector output  973 . Thus, when the sensor relay  974  is closed, power may travel from the bus connector input  972  to the bus connector output  973  and then to whatever is electrically coupled to the bus connector output  973 . In one or more embodiments, the default position of the sensor relay  974  may be open. Further, in one or more embodiments, the sensor relay  974  may be configured to open if the sensor fails a diagnostic check. Thus, in one or more embodiments, the A2L control board  950  may learn that a sensor has failed by way of a loss of signal from the feedback wire coupled to a last A2L sensor  970   c , and then the A2L control board may respond by turning off the functionality of the HVAC system  900 . 
     Additionally, in one or more embodiments, each A2L sensor may include a sensor feedback port  975 . In one or more embodiments, the sensor feedback port  975  may be used to send sensor feedback by way of a feedback wire. More specifically, in one or more embodiments, the signal, which may be analog or digital and wired or wireless, that is sent back to the A2L control board  950  by way of the sensor feedback port  975  may indicate that all sensors on the network have successfully completed their internal checks, are functioning properly, and there are no more sensors in the chain. The sensor feedback port  975  may be disposed on the sensor such that the sensor relay  974  is electrically disposed between the sensor feedback port  975  and the bus connector input  972 . Thus, when the sensor relay  974  is open, power is blocked from travelling from the bus connector input  972  to the sensor feedback port  975 . Further, when the sensor relay  974  is closed, power may travel from the bus connector input  972  to the sensor feedback port  975  and then to whatever is electrically coupled to the sensor feedback port  975 . 
     In one or more embodiments, as shown in  FIG.  9   , the first A2L sensor  970   a , the second A2L sensor  970   b , and the last A2L sensor  970   c  may be connected in series and electrically coupled to the A2L control board  950 . By way of example, the A2L control board  950  may be directly electrically coupled to the first A2L sensor by way of an RS-485 4 wire harness coupled between the first sensor connector  957  and the bus connector input  972  of the first A2L sensor  970   a . Further, the first A2L sensor  970   a  may be directly coupled to the second A2L sensor  970   b  by way of an RS-485 4 wire harness coupled between the bus connector output  973  of the first A2L sensor  970   a  and the bus connector input  972  of the second A2L sensor  970   b . Furthermore, the second A2L sensor  970   b  may be directly coupled to the last A2L sensor  970   c  by way of an RS-485 4 wire harness coupled between the bus connector output  973  of the second A2L sensor  970   b  and the bus connector input  972  of the last A2L sensor  970   c . Additionally, the last A2L sensor  970   c  may be directly coupled to the A2L control board  950  by way of a feedback wire coupled between the sensor feedback port  975  of the last A2L sensor  970   c  and the second sensor connector  958  of the A2L control board. 
     One of ordinary skill in the art, using common sense, would understand that the configuration of A2L sensors  970   a ,  970   b ,  970   c  as described above with respect to  FIG.  9    may be utilized in any of the HVAC systems  100 ,  300 ,  500 ,  700  described above with respect to FIGS.  1 - 8 . Further, while only one sensor architecture is shown in  FIG.  9   , one of ordinary skill in the art, using common sense, would understand that any A2L sensors may be used. Furthermore, one of ordinary skill in the art would understand that the configuration of sensors as shown in  FIG.  9    works with any A2L sensor that has a power input and a power output separated by any type of switch that prevents power from reaching the power output until the sensor has passed internal diagnostics. Additionally, while the sensor architecture is described as using an RS-485 4 wire harness in a number of locations, one of ordinary skill in the art would understand that any form of connecting the sensors and the A2L control board that allows for two-way communication may be used, whether digital or analog and wired or wireless. Further, while three sensors are shown in  FIG.  9   , one of ordinary skill in the art would understand that two sensors may be used in series in the same manner described above, or a single sensor may be used instead. 
     Referring now to  FIG.  10   , a flow chart of a method of installing and testing a configuration of A2L sensors as described above with regard to  FIG.  9    for an HVAC system using an A2L refrigerant, according to one or more embodiments, is illustrated. The method  1000  may include one or more of the following: (step  1010 ) disposing the A2L sensors  970   a ,  970   b ,  970   c  within the HVAC system  900 ; (step  1020 ) connect the A2L sensors  970   a ,  970   b ,  970   c  to the A2L control board  950 ; (step  1030 ) power each of the A2L sensors  970   a ,  970   b ,  970   c  on and run internal diagnostics; (step  1040 ) send confirmation to the A2L control board  950  that the A2L sensors are all installed and functioning properly. 
     At step  1010 , each of the A2L sensors  970   a ,  970   b ,  970   c  may be disposed within the HVAC system  900  as necessary to make sure that any A2L refrigerant leaks that may occur are detected almost immediately. By way of example, disposing the A2L sensors  970   a ,  970   b ,  970   c  within the HVAC system  900  may include at least, finding a distinct place for each A2L sensor  970   a ,  970   b ,  970   c  that is adjacent to an evaporator coil of the indoor unit of the HVAC system  900  and coupling each sensor  970   a ,  970   b ,  970   c  thereto. 
     Further, at step  1020 , the A2L sensors  970   a ,  970   b ,  970   c  may be coupled to the A2L control board  950 . Coupling the A2L sensors  970   a ,  970   b ,  970   c  to the A2L control board  950  may include, at least: (step  1021 ) connecting the first A2L sensor  970   a  to the A2L control board  950 ; (step  1022 ) connecting the second A2L sensor  970   b  to the first A2L sensor  970   a ; (step  1023 ) connecting the last A2L sensor  970   c  to the second A2L sensor  970   b ; and (step  1024 ) connecting the last A2L sensor  970   c  to the A2L control board  950 . 
     At step  1021 , the first A2L sensor  970   a  may be connected to the A2L control board  950 . In one or more embodiments, connecting the first A2L sensor  970   a  to the A2L control board  950  may include attaching an RS-485 bus on one end to a first sensor connector  957  of the A2L control board  950  and on the other end to a bus connector input  972  of the first A2L sensor  970   a . Further, at step  1022 , the first A2L sensor  970   a  may be connected to the second A2L sensor  970   b . In one or more embodiments, connecting the first A2L sensor  970   a  to the second A2L sensor  970   b  may include attaching an RS-485 bus on one end to a bus connector output  973  of the first A2L sensor  970   a  and on the other end to a bus connector input  972  of the second A2L sensor  970   b . Furthermore, at step  1023 , the second A2L sensor  970   b  may be connected to the last A2L sensor  970   c . In one or more embodiments, connecting the second A2L sensor  970   b  to the last A2L sensor  970   c  may include attaching an RS-485 bus on one end to a bus connector output  973  of the second A2L sensor  970   b  and on the other end to a bus connector input  972  of the last A2L sensor  970   c . Additionally, at step  1024 , the last A2L sensor  970   c  may be connected to the A2L control board  950 . In one or more embodiments, connecting the last A2L sensor  970   c  to the A2L control board  950  may include attaching a feedback line on one end to a sensor feedback port  975  of the last A2L sensor  970   c  and on the other end to a second sensor connector  958  of the A2L control board  950 . 
     At step  1030 , each of the A2L sensors  970   a ,  970   b ,  970   c  may be powered on and run through internal diagnostics. Powering on and testing each of the A2L sensors may include, at least: the first A2L sensor  970   a  (step  1031 ) receiving power from the A2L control board  950 , (step  1032 ) running an internal diagnostic test, and, if it passed the internal diagnostic test, (step  1033 ) closing sensor relay  974  of the first A2L sensor  970   a ; the second A2L sensor  970   b  (step  1034 ) receiving power from the first A2L sensor  970   a , (step  1035 ) running an internal diagnostic test, and, if it passed the internal diagnostic test, (step  1036 ) closing sensor relay  974  of the second A2L sensor  970   b ; the last A2L sensor  970   c  (step  1037 ) receiving power from the second A2L sensor  970   b , (step  1038 ) running an internal diagnostic test, and, if it passed the internal diagnostic test, (step  1039 ) closing sensor relay  974  of the last A2L sensor  970   c.    
     At step  1031 , once the A2L sensors  970   a ,  970   b ,  970   c  are physically coupled to the A2L control board  950 , the A2L control board  950  may send power to the first A2L sensor  970   a , which the first A2L sensor  970   a  may receive and use to power on. Further, at step  1032 , the first A2L sensor  970   a  may run an internal diagnostic check of the sensing components  971 , in which the first A2L sensor  970   a  confirms whether the sensing components  971  are functioning properly. Additionally, at step  1033 , if the first A2L sensor  970   a  passed the internal diagnostic check, then the first sensor  970   a  may close the sensor relay  974 , which allows power to travel from the bus connector input  972  to the bus connector output  973  and the sensor feedback port  975 . 
     At step  1034 , once the first A2L sensor  970   a  closes its sensor relay  974 , the first A2L sensor  970   a  may send power to the second A2L sensor  970   b , which the second A2L sensor  970   b  may receive and use to power on. Further, at step  1035 , the second A2L sensor  970   b  may run an internal diagnostic check of the sensing components  971 , in which the second A2L sensor  970   b  confirms whether the sensing components  971  are functioning properly. Additionally, at step  1036 , if the second A2L sensor  970   b  passed the internal diagnostic check, then the second sensor  970   b  may close the sensor relay  974 , which allows power to travel from the bus connector input  972  to the bus connector output  973  and the sensor feedback port  975 . 
     At step  1037 , once the second A2L sensor  970   b  closes its sensor relay  974 , the second A2L sensor  970   b  may send power to the last A2L sensor  970   c , which the last A2L sensor  970   c  may receive and use to power on. Further, at step  1038 , the last A2L sensor  970   c  may run an internal diagnostic check of the sensing components  971 , in which the last A2L sensor  970   c  confirms whether the sensing components  971  are functioning properly. Additionally, at step  1039 , if the last A2L sensor  970   c  passed the internal diagnostic check, then the last sensor  970   c  may close the sensor relay  974 , which allows power to travel from the bus connector input  972  to the bus connector output  973  and the sensor feedback port  975 . 
     At step  1040 , once the last A2L sensor  970   c  closes its sensor relay  974 , the last A2L sensor  970   c  may send power to the A2L control board  950  by way of the feedback line connected between the sensor feedback port  975  of the last A2L sensor  970   c  and the second sensor connector  958  of the A2L control board  950 . Receiving this feedback signal from the last A2L sensor  970   c  notifies the A2L control board  950  that all sensors on the network have successfully completed their internal checks, are functioning properly, and there are no more sensors in the chain that need to be connected and tested. This is so, because, at any point in the chain of sensors, if there is a failure of a sensor, the sensor relay will not close, and thus, all subsequent sensors in the chain and the feedback port of the last sensor in the chain will not receive power and the A2L control board will not receive the feedback it needs. 
     One of ordinary skill in the art, using common sense, would understand that the method  1000  of installation and testing of A2L sensors  970   a ,  970   b ,  970   c  as described above with respect to  FIG.  10    may be utilized in any of the methods  200 ,  400 ,  600 ,  800  described above with respect to  FIGS.  1 - 8   . Further, while only one sensor architecture is described by the method of  FIG.  10   , one of ordinary skill in the art, using common sense, would understand that any A2L sensors may be used. Furthermore, one of ordinary skill in the art would understand that the configuration of sensors as described in the method  1000  of  FIG.  10    works with any A2L sensor that has a power input and a power output separated by any type of switch that prevents power from reaching the power output until the sensor has passed internal diagnostics. Additionally, while the sensor architecture is described as using an RS-485 4 wire harness in a number of locations, one of ordinary skill in the art would understand that any form of connecting the sensors and the A2L control board that allows for two-way communication may be used, whether digital or analog and wired or wireless. Further, while the installation and testing of three sensors is described by method  1000 , one of ordinary skill in the art would understand that two sensors may be used in series in the same manner described above, or a single sensor may be used instead. 
     Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. 
     The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.