# US 11,441,803 B2 · HVAC system and method of circulating flammable refrigerant > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,441,803 B2 - Document ID: US11441803B2 - Status: Granted - Kind: B2 - Application number: 17/155,790 - Filed: 2021-01-22 - Published: 2021-05-13 - Granted: 2022-09-13 - Earliest claimed: 2018-10-17 - Assignees: Lennox Industries Inc. - Applicants: Lennox Industries Inc. - Inventors: Rakesh Goel; Umesh Gokhale - Web page: https://patentgrep.com/patent/US11441803B2 ## CPC - F24F 11/36: to leakage of heat-exchange fluid - F24F 11/39: Monitoring filter performance - F24F 11/52: Indication arrangements, e.g. displays - F24F 11/74: for controlling air flow rate or air velocity - F24F 11/77: by controlling the speed of ventilators - F24F 11/88: Electrical aspects, e.g. circuits - F25B 49/02: for compression type machines, plants or systems - F24F 2110/50: Air quality properties - F24F 2140/10: Pressure - F25B 2400/12: Inflammable refrigerants - F25B 2500/222: Detecting refrigerant leaks - F25B 2600/11: Fan speed control - F25B 2700/13: Mass flow of refrigerants - F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02) - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS ## Abstract A controller of a heating, ventilation, and air conditioning (HVAC) system, the controller comprising instructions that cause the controller to determine an air flowrate of an air blower of the HVAC system and calculate a threshold value based on a minimum required air flowrate. The controller further comprises instructions that cause the controller to send a notification to an operator of the HVAC system indicating that the air flowrate of the air blower is less than the threshold value in response to determining that the air flowrate of the air blower is less than the threshold value and shut down the HVAC system such that the refrigerant is no longer circulated by the componentry of the HVAC system in response to determining that the air flowrate of the air blower is less than the minimum required air flowrate. ## Claims ### Claim 1 A heating, ventilation, and air condition (“HVAC”) system operable to condition an enclosed space, the HVAC system comprising: an air blower operable to push air into the enclosed space; and a controller comprising processing circuitry and a computer readable storage medium comprising instructions that, when executed by the processing circuitry, cause the controller to: determine an air flowrate of the air blower; upon determining that the air blower cannot provide an air flowrate equal to or above a comfort setpoint: operate the air blower at the minimum required air flowrate; determine an external static pressure of the HVAC system when the air blower is operating at the minimum required air flowrate; and in response to determining that the external static pressure of the HVAC system exceeds a maximum external static pressure of the HVAC system, send a notification to an operator of the HVAC system indicating that external static pressure of the HVAC system exceeds the maximum external static pressure of the HVAC system. ### Claim 2 (depends on 1) The system of claim 1, wherein: the HVAC system further comprises a gas sensor configured to detect a refrigerant leak of the HVAC system; and the controller comprises further instructions that, when executed by the processing circuitry, cause the controller to operate the blower in response to detecting the refrigerant leak. ### Claim 3 (depends on 1) The system of claim 1, wherein: the HVAC system further comprises one or more of a subcool sensor or a superheat sensor wherein each of the subcool sensor and the superheat sensor is configured to detect a refrigerant leak of the HVAC system; and the controller comprises further instructions that, when executed by the processing circuitry, cause the controller to operate the blower in response to detecting the refrigerant leak. ### Claim 4 (depends on 1) The system of claim 1, wherein the controller determines the air flowrate of the air blower by receiving data from a motor of the air blower. ### Claim 5 (depends on 1) The system of claim 1, wherein the controller comprises instructions that, when executed by the processing circuitry, cause the controller to calculate a threshold value based on a minimum required air flowrate, wherein: a minimum air flowrate is calculated based on a mass of a refrigerant circulating in the HVAC system and a lower flammability limit corresponding to the refrigerant; the threshold value is greater than the minimum air flowrate; and the threshold value is less than a comfort setpoint. ### Claim 6 (depends on 1) The system of claim 1, wherein the controller further comprises instructions that, when executed by the processing circuitry, cause the controller to: determine that the air flowrate of the air blower is decreasing over a period of time; and send a notification to an operator of the HVAC system indicating that a change in air filter is needed. ### Claim 7 (depends on 1) The system of claim 1, wherein the controller determines the external static pressure by receiving data from a motor of the air blower. ### Claim 8 (depends on 1) The system of claim 1, wherein the controller comprises instructions that, when executed by the processing circuitry, cause the controller to: in response to determining that the air flowrate of the air blower is less the threshold value, send a notification to an operator of the HVAC system indicating that the air flowrate of the air blower is less than the threshold value; and in response to determining that the air flowrate of the air blower is less than the minimum required air flowrate, shut down the HVAC system such that the refrigerant is no longer circulating in the HVAC system. ### Claim 9 A method for a heating, ventilation, and air conditioning (“HVAC”) system, the method comprising: determining, by one or more controllers of the HVAC system, an air flowrate of an air blower of the HVAC system; upon determining, by the one or more controllers, that the air blower cannot provide an air flowrate equal to or above a comfort setpoint operate the air blower at the minimum required air flowrate: determining, by the one or more controllers, an external static pressure of the HVAC system when the air blower is operating at the minimum required air flowrate; and in response to determining that the external static pressure of the HVAC system exceeds a maximum external static pressure of the HVAC system, sending, by the one or more controllers, a notification to an operator of the HVAC system indicating that external static pressure of the HVAC system exceeds the maximum external static pressure of the HVAC system. ### Claim 10 (depends on 9) The method of claim 9, further comprising: detecting, by a gas sensor, a refrigerant leak of the HVAC system; and operate, by the one or more controllers, the blower in response to detecting the refrigerant leak. ### Claim 11 (depends on 9) The method of claim 9, further comprising: detecting, by one or more of a sub cool sensor or a superheat sensor, a refrigerant leak; and operate, by the one or more controllers, the blower in response to detecting the refrigerant leak. ### Claim 12 (depends on 9) The method of claim 9, wherein the one or more controllers determine the air flowrate of the air blower by receiving data from a motor of the air blower. ### Claim 13 (depends on 9) The method of claim 9, further comprising calculating, by the one or more controllers, a threshold value based on a minimum required air flowrate, wherein: a minimum air flowrate is calculated based on a mass of a refrigerant circulating in the HVAC system and a lower flammability limit corresponding to the refrigerant; the threshold value is greater than the minimum air flowrate; and the threshold value is less than a comfort setpoint. ### Claim 14 (depends on 9) The method of claim 9, further comprising: determining, by the one or more controllers, that the air flow rate of the air blower is decreasing over a period of time; and sending, by the one or more controllers, a notification to an operator of the HVAC system indicating that a change in air filter is needed. ### Claim 15 (depends on 9) The method of claim 9, wherein the one or more controllers determine the external static pressure by receiving data from a motor of the air blower. ### Claim 16 (depends on 9) The method of claim 9, further comprising: in response to determining that the air flowrate of the air blower is less the threshold value, sending, by the one or more controllers, a notification indicating that the air flowrate of the air blower is less than the threshold value; and in response to determining that the air flowrate of the air blower is less than the minimum required air flowrate, shutting down, by the one or more controllers, the HVAC system such that the refrigerant is no longer circulating in the HVAC system. ### Claim 17 A controller comprising processing circuitry and a computer readable storage medium comprising instructions that, when executed by the processing circuitry, cause the controller to: determine an air flowrate of an air blower of the HVAC system; upon determining that the air blower cannot provide an air flowrate equal to or above a comfort setpoint operate the air blower at the minimum required air flowrate: determine an external static pressure of the HVAC system when the air blower is operating at the minimum required air flowrate; and in response to determining that the external static pressure of the HVAC system exceeds a maximum external static pressure of the HVAC system, send a notification to an operator of the HVAC system indicating that external static pressure of the HVAC system exceeds the maximum external static pressure of the HVAC system. ### Claim 18 (depends on 17) The controller of claim 17, further comprising instructions that, when executed by the processing circuitry, cause the controller to operate, by the one or more controllers, the blower in response to detecting a refrigerant leak. ### Claim 19 (depends on 17) The controller of claim 17, further comprising instructions that, when executed by the processing circuitry, cause the controller to: determine that the air flow rate of the air blower is decreasing over a period of time; and send a notification to an operator of the HVAC system indicating that a change in air filter is needed. ### Claim 20 (depends on 17) The controller of claim 17, further comprising instructions that, when executed by the processing circuitry, cause the controller to: calculate a threshold value based on a minimum required air flowrate, wherein: a minimum air flowrate is calculated based on a mass of a refrigerant circulating in the HVAC system and a lower flammability limit corresponding to the refrigerant; and the threshold value is greater than the minimum air flowrate. ### Claim 21 (depends on 17) The controller of claim 17, further comprising instructions that, when executed by the processing circuitry, cause the controller to: in response to determining that the air flowrate of the air blower is less the threshold value, send a notification indicating that the air flowrate of the air blower is less than the threshold value; and in response to determining that the air flowrate of the air blower is less than the minimum required air flowrate, shut down the HVAC system such that the refrigerant is no longer circulating in the HVAC system.