# US 2026/0098652 A1 · Controlling a variable-speed heating, ventilation and air-conditioning system using a non-communicating two-stage thermostat > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0098652 A1 - Document ID: US20260098652A1 - Status: Published application - Kind: A1 - Application number: 19/338,996 - Filed: 2025-09-24 - Published: 2026-04-09 - Earliest claimed: 2024-10-07 - Assignees: Carrier Corporation - Applicants: Carrier Corporation - Inventors: Derek Leman - Web page: https://patentgrep.com/patent/US20260098652A1 ## CPC - F24F 11/63: Electronic processing - F24F 11/46: Improving electric energy efficiency or saving - F24F 11/86: by controlling compressors within refrigeration or heat pump circuits - F24F 2110/12: of the outside air - F24F 2130/20: Sunlight - F24F 2140/50: Load - 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) ## Abstract A method is provided for controlling a variable-speed heat, ventilation and air conditioning (HVAC) system. The method includes, responsive to a first signal, determining a system capacity and providing the system capacity by the variable-speed HVAC system to a space, responsive to the first signal and a second signal, providing a system maximum capacity by the variable-speed HVAC system to the space and, responsive to an off signal, shutting off of the variable-speed HVAC system. ## Claims ### Claim 1 A method for controlling a variable-speed heat, ventilation and air conditioning (HVAC) system, the method comprising: responsive to a first signal, determining a system capacity and providing the system capacity by the variable-speed HVAC system to a space; responsive to the first signal and a second signal, providing a system maximum capacity by the variable-speed HVAC system to the space; and responsive to an off signal, shutting off of the variable-speed HVAC system. ### Claim 2 (depends on 1) The method according to claim 1, wherein the space comprises a residential home. ### Claim 3 (depends on 1) The method according to claim 1, wherein the determining of the system capacity comprises calculating a delivered capacity as a function of an instantaneous capacity delivered to the space over a predetermined time. ### Claim 4 (depends on 3) The method according to claim 3, wherein: the delivered capacity is a function of the instantaneous capacity delivered to the space over a past predetermined amount of time, and the delivered capacity is equal to a sum of a previously delivered capacity multiplied by n/m and the instantaneous capacity multiplied by (m−n)/m, where m is a time period and n is a fraction of the time period. ### Claim 5 (depends on 3) The method according to claim 3, wherein: the instantaneous capacity is equal to a refrigerant massflow multiplied by a change in enthalpy, the refrigerant massflow is equal to refrigerant density as a function of suction pressure multiplied by compressor displacement multiplied by compressor RPMs, and the change in enthalpy is equal to a difference between a vapor enthalpy as a function of discharge pressure and discharge temperature and a liquid enthalpy as a function of a liquid service valve temperature. ### Claim 6 (depends on 1) The method according to claim 1, wherein the providing of the system capacity comprises at least one of adding an outside air temperature adjustment and adding a solar gain adjustment. ### Claim 7 A method for controlling a variable-speed heat, ventilation and air conditioning (HVAC) system comprising a thermostat and a controller, the method comprising: determining, by the thermostat, whether to issue: a first signal indicating first HVAC system operation, a second signal indicating second HVAC system operation, and an off signal indicating HVAC system shut-off; issuing, based on determination results, one or more of the first signal, the second signal and the off signal to the controller by the thermostat; determining a system capacity and causing the variable-speed HVAC system to provide the system capacity to a space by the controller when the controller receives only the first signal; causing the variable-speed HVAC system to provide a system maximum capacity to the space by the controller when the controller receives the first and second signals; and shutting off the variable-speed HVAC system by the controller when the controller receives the off signal. ### Claim 8 (depends on 7) The method according to claim 7, wherein the space comprises a residential home. ### Claim 9 (depends on 7) The method according to claim 7, wherein the determining of whether to issue the first signal, the second signal and the off signal is based on a difference between an actual temperature of the space and a set point. ### Claim 10 (depends on 9) The method according to claim 9, wherein: the determining of the system capacity comprises calculating a delivered capacity as a function of an instantaneous capacity delivered to the space over a predetermined time by the controller, and the delivered capacity is a function of the instantaneous capacity delivered to the space over a past predetermined amount of time. ### Claim 11 (depends on 10) The method according to claim 10, wherein the delivered capacity is equal to a sum of a previously delivered capacity multiplied by n/m and the instantaneous capacity multiplied by (m−n)/m, where m is a time period and n is a fraction of the time period. ### Claim 12 (depends on 10) The method according to claim 10, wherein: the instantaneous capacity is equal to a refrigerant massflow multiplied by a change in enthalpy, the refrigerant massflow is equal to refrigerant density as a function of suction pressure multiplied by compressor displacement multiplied by compressor RPMs, and the change in enthalpy is equal to a difference between a vapor enthalpy as a function of discharge pressure and discharge temperature and a liquid enthalpy as a function of a liquid service valve temperature. ### Claim 13 (depends on 7) The method according to claim 7, wherein the causing of the variable-speed HVAC system to provide the system capacity by the controller comprises at least one of adding an outside air temperature adjustment based on outdoor air temperature readings of an outdoor unit sensor by the controller and adding a solar gain adjustment based on a time of day by the controller. ### Claim 14 A system for controlling a variable-speed heat, ventilation and air conditioning (HVAC) system, the system comprising: a controller of the HVAC system; and a thermostat configured to determine whether to issue a first signal indicating low capacity HVAC system operation, a second signal indicating high capacity HVAC system operation and an off signal indicating HVAC system shut-off and to issue one or more of the first signal, the second signal and the off signal to the controller based on determination results, the controller being configured to: determine a system capacity and cause the variable-speed HVAC system to provide the system capacity to a space upon receipt of only the first signal; cause the variable-speed HVAC system to provide a system maximum capacity to the space upon receipt of the first and second signals; and shut off the variable-speed HVAC system upon receipt of the off signal. ### Claim 15 (depends on 14) The system according to claim 14, wherein the space comprises a residential home. ### Claim 16 (depends on 14) The system according to claim 14, wherein the thermostat is configured to determine whether to issue the first signal, the second signal and the off signal based on a difference between an actual temperature of the space and a set point. ### Claim 17 (depends on 14) The system according to claim 14, wherein: the controller is configured to determine the system capacity by calculating a delivered capacity as a function of an instantaneous capacity delivered to the space over a predetermined time, and the delivered capacity is a function of the instantaneous capacity delivered to the space over a past predetermined amount of time. ### Claim 18 (depends on 17) The system according to claim 17, wherein the delivered capacity is equal to a sum of a previously delivered capacity multiplied by n/m and the instantaneous capacity multiplied by (m−n)/m, where m is a time period and n is a fraction of the time period. ### Claim 19 (depends on 17) The system according to claim 17, wherein: the instantaneous capacity is equal to a refrigerant massflow multiplied by a change in enthalpy, the refrigerant massflow is equal to refrigerant density as a function of suction pressure multiplied by compressor displacement multiplied by compressor RPMs, and the change in enthalpy is equal to a difference between a vapor enthalpy as a function of discharge pressure and discharge temperature and a liquid enthalpy as a function of a liquid service valve temperature. ### Claim 20 (depends on 14) The system according to claim 14, wherein the controller is configured to cause the variable-speed HVAC system to provide the system capacity by at least one of adding an outside air temperature adjustment based on outdoor air temperature readings of an outdoor unit sensor and adding a solar gain adjustment based on a time of day.