Load management aware fan control

Abstract

A fan-control device for overriding normal operation of a circulation fan delivering conditioned air through ductwork in an unconditioned space. The fan-control device includes a detection circuit and a fan relay. The detection circuit is configured to detect a cooling system control voltage and a cooling system control current and to output a fan control override signal when the cooling system control voltage is detected and the cooling system control current is absent.

1 . A load-management-aware fan-control device for overriding normal operation of a circulation fan delivering conditioned air through ductwork that is normally controlled by a thermostat that includes a load management device, the load-management-aware fan-control device comprising:
 a detection circuit configured to detect a HVAC system control voltage and a HVAC system control current and to output a fan control override signal when the HVAC system control voltage is detected and the HVAC system control current is absent, the control voltage being detected by the detection circuit when the HVAC system requests that a load under control of a load-management device be powered, and the control current being detected as absent when the HVAC system requests that the load be powered and the load-management device is activated such that the load is not powered; and   a fan relay configured to receive the fan control override signal from the detection circuit and to break an electrical connection between a thermostat of the HVAC system and the fan in response to the fan control override signal, thereby overriding normal control of the fan by the thermostat and preventing operation of the fan and circulation of unconditioned air when the load-management device is activated.   
     
     
         2 . The device of  claim 1 , wherein the detection circuit further includes a current-sensing coil configured to detect the HVAC system control current. 
     
     
         3 . The device of  claim 2 , wherein the current-sensing coil is a snap-on current transformer. 
     
     
         4 . The device of  claim 1 , wherein the fan relay is a normally-closed relay. 
     
     
         5 . The device of  claim 1 , wherein the detection circuit is further configured to detect the HVAC system control voltage at a terminal of a forced-air unit of the HVAC system and the thermostat. 
     
     
         6 . The device of  claim 1 , wherein the HVAC system control voltage is a 24VAC control voltage. 
     
     
         7 . The device of  claim 1 , further including a time delay device in electrical communication with the detection circuit and the fan relay, the time delay device configured to delay the break of the electrical connection between the thermostat of the HVAC system and the fan for a predetermined time period after the detection of a HVAC system control voltage and the detection of the absence of the HVAC system control current. 
     
     
         8 . The device of  claim 7 , wherein the predetermined time period is an amount of time required to force substantially all of a volume of conditioned air remaining in the ductwork after the detection circuit has detected the HVAC system control voltage and the absence of the HVAC system control current, and before the fan relay breaks the electrical connection between the thermostat of the HVAC system and the fan. 
     
     
         9 . The device of  claim 1 , further including a timer device in electrical communication with the detection circuit and the fan relay, the timer device configured to signal the fan relay to make an electrical connection between the thermostat of the HVAC system and the fan after a predetermined time period, the predetermined time period measured from the break of the electrical connection between the thermostat and the fan. 
     
     
         10 . The device of  claim 1 , wherein the detection circuit includes:
 a first detection circuit relay configured to be in an open position in the absence of the HVAC system control current;   a second detection circuit relay in electrical communication with the first detection circuit relay and the fan relay, and configured to be in a closed position when the first circuit relay is in an open position, such that in the presence of the HVAC system control voltage, the HVAC system control voltage is applied to a coil of the fan relay, the fan relay thereby receiving the fan control override signal.   
     
     
         11 . A method of controlling a circulation fan of an HVAC system having ductwork located in an unconditioned space and a load-management device controlling an electrical load, the method of controlling the circulation fan comprising:
 detecting an HVAC system control voltage when the HVAC system requests an electrical load under control of a load-management device be powered;   detecting an absence of an HVAC system control current when the HVAC system requests the electrical load be powered and when the load-management device is activated such that the electrical load is not powered;   in response to detecting the HVAC system control voltage and detecting the absence of the HVAC system control current, generating a fan control override signal for overriding a fan control signal of a thermostat requesting operation of a circulation fan; and   breaking an electrical connection between the thermostat and the circulation fan by receiving the fan control override signal at the fan relay and causing the fan relay to open, thereby overriding the fan control signal of the thermostat and preventing operation of the circulation fan.   
     
     
         12 . The method of  claim 11 , wherein the HVAC system is a cooling system and the electrical load is a compressor, such that detecting an HVAC system control voltage when the HVAC system requests an electrical load under control of a load-management device be powered comprises:
 detecting a cooling system control voltage when the cooling system requests an electrical load under control of a load-management device be powered;   detecting an absence of an HVAC system control current when the HVAC system requests the electrical load be powered and when the load-management device is activated such that the electrical load is not powered comprises detecting an absence of a cooling system control current when the cooling system requests the compressor be powered and when the load-management device is activated such that the compressor is not powered; and   detecting the HVAC system control voltage and detecting the absence of the HVAC system control current comprises detecting the cooling system control voltage and detecting the absence of the cooling system control current.   
     
     
         13 . The method of  claim 11 , further comprising activating the load-management device to interrupt power to the electrical load. 
     
     
         14 . The method of  claim 13 , wherein activating the load-management device to interrupt power to the electrical load comprises receiving a load-management command at the load-management device and activating a relay of the load-management device, thereby breaking a power connection of the electrical load. 
     
     
         15 . The method of  claim 11 , wherein detecting an HVAC system control voltage when the HVAC system requests an electrical load under control of a load-management device be powered comprises detecting a 24VAC HVAC system control voltage. 
     
     
         16 . The method of  claim 11 , further comprising delaying the breaking of the electrical connection between the thermostat and the circulation fan for a predetermined time period after the detecting of the HVAC system control voltage and the detection of the absence of the HVAC system control current. 
     
     
         17 . A method of optimizing cooling efficiency when managing multiple electrical loads of cooling systems of buildings included in a load-management program, at least some of the cooling systems including above-ground ductwork, the method comprising:
 providing a load-management device to each of a plurality of buildings having cooling systems, each of the load-management devices configured to cause power to a compressor of the cooling system to be interrupted in response to a load-management command, and at least one of the plurality of buildings including a cooling system having above-ground ductwork for distributing conditioned air;   providing a fan control device to the at least one of the plurality of buildings including the cooling system having above-ground ductwork, the fan control device configured to communicate with the load-management device provided to the building and to prevent operation of a circulation fan when power to the compressor is interrupted; and   transmitting a load-management command to the plurality of load-management devices, the command causing each of the load-management devices to interrupt power to the compressor, the interruption of power to the compressor of any building of the plurality of buildings having above-ground ductwork causing the fan control device to prevent operation of the circulation fan, thereby preventing unconditioned air from being distributed through the above-ground ductwork in that building.   
     
     
         18 . The method of  claim 17 , wherein providing a load-management device to each of a plurality of buildings having cooling systems includes providing a load-management device to a plurality of residential home-owners as part of a load-management program for a specified geographic region. 
     
     
         19 . The method of  claim 17 , wherein providing a load-management device to each of a plurality of buildings having cooling systems includes providing a load-control receiver having an internal relay configured to open a set of contacts when activated. 
     
     
         20 . The method of  claim 17 , wherein providing a fan control device to the at least one of the plurality of buildings includes providing a fan control device having a detection circuit and a fan relay, the detection circuit and the fan relay in electrical communication with a thermostat and the circulation fan. 
     
     
         21 . The method of  claim 20 , further including:
 the detection circuit being configured to detect the presence of a cooling system control voltage and the absence of a cooling system control current; and   the fan relay configured to break a connection between a thermostat and the circulation fan in response to the detection circuit detecting the presence of a cooling system control voltage and the absence of a cooling system control current.   
     
     
         22 . The method of  claim 17 , wherein transmitting a load-management command to the plurality of load-management devices includes transmitting a load-management command over a wireless communication network. 
     
     
         23 . The method of  claim 22 , wherein transmitting a load-management command over a wireless communication network includes transmitting a radio-frequency load-management command. 
     
     
         24 . The method of  claim 17 , wherein transmitting a load-management command to the plurality of load-management devices includes transmitting a load-management command over a wired communication network. 
     
     
         25 . The method of  claim 24 , wherein the wired communication network is selected from a group consisting of a power line communication network, a telephone service network and an interne service network. 
     
     
         26 . A load-management-aware fan-control device for overriding normal operation of a circulation fan delivering conditioned air through an above-ground ductwork that is normally controlled by a thermostat of a cooling system that includes a load management device controlling a compressor of the system, the load-management-aware fan-control device comprising:
 means for detecting a cooling system control voltage and a cooling system control current and to output a fan control override signal when the cooling system control voltage is detected and the cooling system control current is absent, the control voltage being detected when the cooling system requests that a compressor under control of a load-management device be powered, and the control current being detected as absent when the cooling system requests that the compressor be powered and the load-management device is activated such that the compressor is not powered; and   means for receiving the fan control override signal and breaking an electrical connection between a thermostat of the cooling system and the fan in response to the fan control override signal, thereby overriding normal control of the fan by the thermostat and preventing operation of the fan and circulation of uncooled air when the load-management device is activated.   
     
     
         27 . The device of  claim 26 , further comprising means for delaying the break of the electrical connection between the thermostat of the cooling system and the fan for a predetermined time period after the detection of a cooling system control voltage and the detection of the absence of the cooling system control current. 
     
     
         28 . The device of  claim 26 , further comprising means for activating the load-management device such that the compressor is not powered. 
     
     
         29 . A load-management-aware fan-control device for overriding normal operation of a circulation fan delivering conditioned air through ductwork in an unconditioned space, the circulation fan being normally controlled by a thermostat, the load-management-aware fan-control device comprising:
 a detection circuit configured to detect a cooling system control voltage and a cooling system control current and to output a fan control override signal when the cooling system control voltage is detected and the cooling system control current is absent, the control voltage being detected by the detection circuit when the cooling system requests that a compressor under control of a load-management device be powered, and the control current being detected as absent when the cooling system requests that the compressor be powered and the load-management device is activated such that the compressor is not powered; and   a fan relay configured to receive the fan control override signal from the detection circuit and to break an electrical connection between a thermostat of the cooling system and the fan in response to the fan control override signal, thereby overriding normal control of the fan by the thermostat and preventing operation of the fan and circulation of unconditioned air when the load-management device is activated.   
     
     
         30 . The load-management-aware fan-control device of  claim 29 , wherein the ductwork located in an unconditioned space comprises ductwork located above ground. 
     
     
         31 . The load-management-aware fan-control device of  claim 29 , wherein the ductwork located above ground comprises ductwork located in an attic space. 
     
     
         32 . The device of  claim 29 , wherein the detection circuit further includes an external current-sensing coil configured to detect the cooling system control current. 
     
     
         33 . The device of  claim 29 , wherein the detection circuit further includes internal current-sensing circuitry. 
     
     
         34 . The device of  claim 29 , wherein the cooling system comprises a portion of an HVAC system that also includes a heating system.