Efficiency heating, ventilating, and air conditioning through indirect extension of compressor run times

Abstract

A load control device for improving energy efficiency of a heating, ventilating, and air-conditioning (HVAC) system by controlling shed times of a compressor of the HVAC system. The load control device includes a compressor cutoff switch, a sensing circuit, and a processor. The processor determines a subsequent mandatory shed time based upon a previous shed time, a previous run time, and a minimum run time. A subsequent mandatory shed longer than the previous mandatory shed time causes a subsequent run time to be increased, thereby increasing system efficiency.

What is claimed is: 
     
         1 . A load control device for improving energy efficiency of a heating, ventilating, and air-conditioning (HVAC) system by controlling shed times of a compressor of the HVAC system, the load control device comprising:
 a compressor cutoff switch comprising a first terminal connectable to a second terminal, the first terminal adapted to receive a control signal from a temperature control device of an HVAC system, the second terminal adapted to transmit the control signal to a device controlling power to a compressor of an HVAC system, compressor cutoff switch adapted to selectively cause an electrically-powered compressor of an HVAC system to be disconnected from a power source by disconnecting the first terminal from the second terminal and interrupting the transmission of the control signal to the device controlling power to the compressor;   a sensing circuit in electrical communication with the second terminal of the compressor cutoff switch, the sensing circuit configured to detect the presence of the control signal and transmit a signal representative of the control signal; and   a processor in electrical communication with the sensing circuit and the compressor cutoff switch, the processor configured to receive the signal representative of the control signal, to determine a subsequent mandatory shed time for a subsequent operating cycle of the compressor based on the run time and the shed time of the previous operating cycle of the compressor, and to cause the compressor cutoff switch to disconnect the first terminal from the second terminal for a period of time substantially equal to the determined subsequent mandatory shed time of the previous operating cycle, the period of time following the previous operating cycle.   
     
     
         2 . The load control device of  claim 1 , wherein the subsequent mandatory shed time is determined by adding the difference between a predetermined minimum run time and the run time of the previous operating cycle to the shed time of the previous operating cycle. 
     
     
         3 . The load control device of  claim 1 , further comprising a transceiver, the transceiver configured to receive load control messages, the load control messages including a command causing the first terminal to disconnect from the second terminal for a predetermined load shed time period, thereby causing power to the compressor to be removed for the predetermined load shed time period. 
     
     
         4 . The load control device of  claim 1 , wherein the sensing circuit comprises a trigger sense circuit. 
     
     
         5 . The load control device of  claim 1 , wherein the sensing circuit comprises a conductive path between the second terminal and the processor. 
     
     
         6 . The load control device of  claim 2 , wherein the compressor comprises an air-conditioning compressor used for cooling. 
     
     
         7 . The load control device of  claim 2 , wherein the predetermined minimum run time is received by the load control device as transmitted by a master controller over a network. 
     
     
         8 . The load control device of  claim 2 , wherein the predetermined minimum run time is saved in a memory of the load control device at or before a time of installation of the load control device. 
     
     
         9 . The load control device of  claim 1 , wherein the processor is further configured to determine a system efficiency of the HVAC system. 
     
     
         10 . A method of improving efficiency of a thermostatically-controlled, compressor-based heating or cooling system by controlling a shed time of the compressor with a load-control device that includes a compressor cutoff switch, and a processor, the method comprising:
 determining a mandatory shed time of a previous operating cycle of the compressor;   measuring a run time of the previous operating cycle of the compressor;   determining using a processor a mandatory compressor shed time of a subsequent operating cycle of the compressor, the subsequent operating cycle occurring after the previous operating cycle and comprising the subsequent mandatory shed time followed by a subsequent compressor run time, and the mandatory shed time determined based on the mandatory shed time of the previous operating cycle, the compressor run time of the previous operating cycle, and a predetermined minimum run time;   opening a compressor cutoff switch for a period of time substantially equal to the mandatory shed time of the subsequent operating cycle; and   removing power to the compressor for at least the period of time substantially equal to the mandatory shed time of the subsequent operating cycle as a result of the opening of the compressor cutoff switch, thereby causing the compressor run time of the subsequent operating cycle to increase and increasing an energy efficiency of the heating or cooling system.   
     
     
         11 . The method of  claim 10 , further comprising determining the minimum compressor run time. 
     
     
         12 . The method of  claim 10 , wherein measuring a run time of the previous operating cycle of the compressor includes:
 detecting a control signal transmitted to a control circuit of the compressor, the control signal selectively causing the compressor to be connected to a power source;   receiving a signal representing the control signal at a processor of a load-control device;   determining by the processor a run time of a previous operating cycle of the compressor based upon the received signal representing the control signal.   
     
     
         13 . The method of  claim 10 , wherein measuring a run time of the previous operating cycle of the compressor includes:
 sensing a control signal at an output of the compressor cut-off switch;   determining the duration of the control signal at the output of the compressor cut-off switch, the duration of the control signal at the output of the compressor cut-off switch being representative of the previous operating cycle of the compressor.   
     
     
         14 . The method of  claim 13 , wherein sensing a control signal at an output of the compressor cut-off switch comprises sensing a control signal at an output of the compressor cut-off switch using a sensing circuit in electrical communication with the processor and the output of the compressor cut-off switch. 
     
     
         15 . The method of  claim 10 , wherein determining a mandatory shed time of a previous operating cycle of the compressor comprises retrieving an initial mandatory shed time stored in a memory of the load-control device. 
     
     
         16 . A load control device for improving energy efficiency of a heating, ventilating, and air-conditioning (HVAC) system by controlling shed times of a compressor of the HVAC system, the load control device comprising:
 means for determining a mandatory shed time of a previous operating cycle of the compressor;   means for measuring a run time of the previous operating cycle of the compressor;   means for determining a mandatory compressor shed time of a subsequent operating cycle of the compressor, the subsequent operating cycle occurring after the previous operating cycle and comprising the subsequent mandatory shed time followed by a subsequent compressor run time, and the mandatory shed time determined based on the mandatory shed time of the previous operating cycle, the compressor run time of the previous operating cycle, and a predetermined minimum run time;   means for opening a compressor cutoff switch for a period of time substantially equal to the mandatory shed time of the subsequent operating cycle; and   means for removing power to the compressor for at least the period of time substantially equal to the mandatory shed time of the subsequent operating cycle as a result of the opening of the compressor cutoff switch, thereby causing the compressor run time of the subsequent operating cycle to increase and increasing an energy efficiency of the heating or cooling system.   
     
     
         17 . The load control device of  claim 16 , further comprising means for sensing a duration of a control signal at an output of the compressor cut-off switch, the duration of the sensed control signal indicative of a compressor run time. 
     
     
         18 . A load control device for improving energy efficiency of a heating, ventilating, and air-conditioning (HVAC) system by controlling shed times of a compressor of the HVAC system, the load control device comprising:
 a compressor cutoff switch in electrical communication with a temperature control device of an HVAC system, compressor cutoff switch adapted to selectively cause an electrically-powered compressor of an HVAC system to be disconnected from a power source;   a processor in electrical communication with the compressor cutoff switch, the processor configured to determine a subsequent mandatory shed time for a subsequent operating cycle of the compressor based on a predetermined minimum run time of the compressor, a run time and a shed time of a previous operating cycle of the compressor, and to cause the compressor cutoff switch to cause power to the compressor to be disconnected for a period of time substantially equal to the determined subsequent mandatory shed time of the previous operating cycle, the subsequent mandatory shed time being a first period of time following the previous operating cycle.   
     
     
         19 . The load control device of  claim 18 , further comprising a sensing circuit in electrical communication with the processor and configured to detect the presence of a control signal at an output of the compressor cut-off switch, the control signal requesting that power be connected to the compressor. 
     
     
         20 . The load control device of  claim 19 , wherein the sensing circuit comprises a trigger sense circuit. 
     
     
         21 . The load control device of  claim 18 , wherein the subsequent mandatory shed time is determined by adding a difference between the predetermined minimum run time and the run time of the previous operating cycle to the shed time of the previous operating cycle. 
     
     
         22 . The load control device of  claim 18 , further comprising a receiver, the receiver configured to receive load control messages, the load control messages including a command causing power to the compressor to be removed for a predetermined load shed time period. 
     
     
         23 . The load control device of  claim 22 , wherein the predetermined minimum run time is received by the receiver over a long-haul communications network. 
     
     
         24 . The load control device of  claim 22 , wherein the compressor comprises an air-conditioning compressor used for cooling. 
     
     
         25 . A load control device for determining and selectively improving energy efficiency of a heating, ventilating, and air-conditioning (HVAC) by controlling operation of a compressor of the HVAC system, the load control device comprising:
 a compressor cutoff switch in electrical communication with a temperature control device of an HVAC system, the compressor cutoff switch adapted to selectively cause an electrically-powered compressor of an HVAC system to be disconnected from a power source;   a processor in electrical communication with the compressor cutoff switch, the processor configured to determine a system energy efficiency of the HVAC system based on run times of operating cycles of the compressor and a predetermined optimal run time of the compressor, and to selectively operate the compressor cutoff switch to cause power to the compressor to be disconnected for a mandatory shed-time period, thereby causing a run time of the compressor to be extended and increase the system energy efficiency of the HVAC system.   
     
     
         26 . The load control device of  claim 25 , wherein the mandatory shed time is longer than a shed time of a previous operating cycle, and the processor is further configured to cause the cutoff switch to interrupt transmission of a control signal from the temperature control device.