Controlling a variable-speed heating, ventilation and air-conditioning system using a non-communicating two-stage thermostat

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.

What is claimed is: 
     
         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.   
     
     
         2 . The method according to  claim 1 , wherein the space comprises a residential home. 
     
     
         3 . 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. 
     
     
         4 . 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.   
     
     
         5 . 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.   
     
     
         6 . 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. 
     
     
         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.   
     
     
         8 . The method according to  claim 7 , wherein the space comprises a residential home. 
     
     
         9 . 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. 
     
     
         10 . 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.   
     
     
         11 . 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. 
     
     
         12 . 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.   
     
     
         13 . 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. 
     
     
         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.   
     
     
         15 . The system according to  claim 14 , wherein the space comprises a residential home. 
     
     
         16 . 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. 
     
     
         17 . 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.   
     
     
         18 . 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. 
     
     
         19 . 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.   
     
     
         20 . 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.