Abstract:
Various arrangements for controlling multiple environmental zones are presented. A first zone specific device may be configured to alter an environmental condition of a first environmental zone of the multiple environmental zones. The first zone specific device may include a rechargeable power source for at least partially powering the operation of the first zone specific device. The first zone specific device may include a communication interface for communicating with other devices of the system. Also, a central controller may be present that is configured to communicate with the first zone specific device to determine a power status of the rechargeable power source of the first zone specific device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. Ser. No. 14/183,091, filed Feb. 18, 2014, which is a continuation of U.S. Ser. No. 13/269,155, filed Oct. 7, 2011, which is a continuation of U.S. Ser. No. 11/669,066, filed Jan. 30, 2007, now U.S. Pat. No. 8,033,479, issued Oct. 11, 2011, which is a continuation-in-part application of U.S. Ser. No. 10/959,362, filed Oct. 6, 2004, now U.S. Pat. No. 7,168,627, issued Jan. 30, 2007, which are hereby incorporated by reference in their entirety for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a system and method for directing heating and cooling air from an air handler to various zones in a home or commercial structure. 
         [0004]    2. Description of the Related Art 
         [0005]    Most traditional home heating and cooling systems have one centrally-located thermostat that controls the temperature of the entire house. The thermostat turns the Heating, Ventilating, and Air-Conditioner (HVAC) system on or off for the entire house. The only way the occupants can control the amount of HVAC air to each room is to manually open and close the register vents throughout the house. 
         [0006]    Zoned HVAC systems are common in commercial structures, and zoned systems have been making inroads into the home market. In a zoned system, sensors in each room or group of rooms, or zones, monitor the temperature. The sensors can detect where and when heated or cooled air is needed. The sensors send information to a central controller that activates the zoning system, adjusting motorized dampers in the ductwork and sending conditioned air only to the zone in which it is needed. A zoned system adapts to changing conditions in one area without affecting other areas. For example, many two-story houses are zoned by floor. Because heat rises, the second floor usually requires more cooling in the summer and less heating in the winter than the first floor. A non-zoned system cannot completely accommodate this seasonal variation. Zoning, however, can reduce the wide variations in temperature between floors by supplying heating or cooling only to the space that needs it. 
         [0007]    A zoned system allows more control over the indoor environment because the occupants can decide which areas to heat or cool and when. With a zoned system, the occupants can program each specific zone to be active or inactive depending on their needs. For example, the occupants can set the bedrooms to be inactive during the day while the kitchen and living areas are active. 
         [0008]    A properly zoned system can be up to 30 percent more efficient than a non-zoned system. A zoned system supplies warm or cool air only to those areas that require it. Thus, less energy is wasted heating and cooling spaces that are not being used. 
         [0009]    In addition, a zoned system can sometimes allow the installation of smaller capacity equipment without compromising comfort. This reduces energy consumption by reducing wasted capacity. 
         [0010]    Unfortunately, the equipment currently used in a zoned system is relatively expensive. Moreover, installing a zoned HVAC system, or retrofitting an existing system, is far beyond the capabilities of most homeowners. Unless the homeowner has specialized training, it is necessary to hire a specially-trained professional HVAC technician to configure and install the system. This makes zoned HVAC systems expensive to purchase and install. The cost of installation is such that even though the zoned system is more efficient, the payback period on such systems is many years. Such expense has severely limited the growth of zoned HVAC systems in the general home market. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0011]    The system and method disclosed herein solves these and other problems by providing an Electronically-Controlled Register vent (ECRV) that can be easily installed by a homeowner or general handyman. The ECRV can be used to convert a non-zoned HVAC system into a zoned system. The ECRV can also be used in connection with a conventional zoned HVAC system to provide additional control and additional zones not provided by the conventional zoned HVAC system. In one embodiment, the ECRV is configured have a size and form-factor that conforms to a standard manually-controlled register vent. The ECRV can be installed in place of a conventional manually-controlled register vent—often without the use of tools. 
         [0012]    In one embodiment, the ECRV is a self-contained zoned system unit that includes a register vent, a power supply, a thermostat, and a motor to open and close the register vent. To create a zoned HVAC system, the homeowner can simply remove the existing register vents in one or more rooms and replace the register vents with the ECRVs. The occupants can set the thermostat on the EVCR to control the temperature of the area or room containing the ECRV. In one embodiment, the ECRV includes a display that shows the programmed setpoint temperature. In one embodiment, the ECRV includes a display that shows the current setpoint temperature. In one embodiment, the ECRV includes a remote control interface to allow the occupants to control the ECRV by using a remote control. In one embodiment, the remote control includes a display that shows the programmed temperature and the current temperature. In one embodiment, the remote control shows the battery status of the ECRV. 
         [0013]    In one embodiment, the EVCR includes a pressure sensor to measure the pressure of the air in the ventilation duct that supplies air to the EVCR. In one embodiment, the EVCR opens the register vent if the air pressure in the duct exceeds a specified value. In one embodiment, the pressure sensor is configured as a differential pressure sensor that measures the difference between the pressure in the duct and the pressure in the room. 
         [0014]    In one embodiment, the ECRV is powered by an internal battery. A battery-low indicator on the ECRV informs the homeowner when the battery needs replacement. In one embodiment, one or more solar cells are provided to recharge the batteries when light is available. In one embodiment, the register vent include a fan to draw additional air from the supply duct in order to compensate for undersized vents or zones that need additional heating or cooling air. 
         [0015]    In one embodiment, one or more ECRVs in a zone communicate with a zone thermostat. The zone thermostat measures the temperature of the zone for all of the ECRVs that control the zone. In one embodiment, the ECRVs and the zone thermostat communicate by wireless communication methods, such as, for example, infrared communication, radio-frequency communication, ultrasonic communication, etc. In one embodiment, the ECRVs and the zone thermostat communicate by direct wire connections. In one embodiment, the ECRVs and the zone thermostat communicate using powerline communication. 
         [0016]    In one embodiment, one or more zone thermostats communicate with a central controller. 
         [0017]    In one embodiment, the EVCR and/or the zoned thermostat includes an occupant sensor, such as, for example, an infrared sensor, motion sensor, ultrasonic sensor, etc. The occupants can program the EVCR or the zoned thermostat to bring the zone to different temperatures when the zone is occupied and when the zone is empty. In one embodiment, the occupants can program the EVCR or the zoned thermostat to bring the zone to different temperatures depending on the time of day, the time of year, the type of room (e.g. bedroom, kitchen, etc.), and/or whether the room is occupied or empty. In one embodiment, various EVCRs and/or zoned thermostats thought a composite zone (e.g., a group of zones such as an entire house, an entire floor, an entire wing, etc.) intercommunicate and change the temperature setpoints according to whether the composite zone is empty or occupied. 
         [0018]    In one embodiment, the home occupants can provide a priority schedule for the zones based on whether the zones are occupied, the time of day, the time of year, etc. Thus, for example, if zone corresponds to a bedroom and zone corresponds to a living room, zone can be given a relatively lower priority during the day and a relatively higher priority during the night. As a second example, if zone corresponds to a first floor, and zone corresponds to a second floor, then zone can be given a higher priority in summer (since upper floors tend to be harder to cool) and a lower priority in winter (since lower floors tend to be harder to heat). In one embodiment, the occupants can specify a weighted priority between the various zones. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  shows a home with zoned heating and cooling. 
           [0020]      FIG. 2  shows one example of a conventional manually-controlled register vent. 
           [0021]      FIG. 3A  is a front view of one embodiment of an electronically-controlled register vent. 
           [0022]      FIG. 3B  is a rear view of the electronically-controlled register vent shown in  FIG. 3A . 
           [0023]      FIG. 4  is a block diagram of a self-contained ECRV. 
           [0024]      FIG. 5  is a block diagram of a self-contained ECRV with a remote control. 
           [0025]      FIG. 6  is a block diagram of a locally-controlled zoned heating and cooling system wherein a zone thermostat controls one or more ECRVs. 
           [0026]      FIG. 7A  is a block diagram of a centrally-controlled zoned heating and cooling system wherein the central control system communicates with one or more zone thermostats and one or more ECRVs independently of the HVAC system. 
           [0027]      FIG. 7B  is a block diagram of a centrally-controlled zoned heating and cooling system wherein the central control system communicates with one or more zone thermostats and the zone thermostats communicate with one or more ECRVs. 
           [0028]      FIG. 8  is a block diagram of a centrally-controlled zoned heating and cooling system wherein a central control system communicates with one or more zone thermostats and one or more ECRVs and controls the HVAC system. 
           [0029]      FIG. 9  is a block diagram of an efficiency-monitoring centrally-controlled zoned heating and cooling system wherein a central control system communicates with one or more zone thermostats and one or more ECRVs and controls and monitors the HVAC system. 
           [0030]      FIG. 10  is a block diagram of an ECRV for use in connection with the systems shown in  FIGS. 6-9 . 
           [0031]      FIG. 11  is a block diagram of a basic zone thermostat for use in connection with the systems shown in  FIGS. 6-9 . 
           [0032]      FIG. 12  is a block diagram of a zone thermostat with remote control for use in connection with the systems shown in  FIGS. 6-9 . 
           [0033]      FIG. 13  shows one embodiment of a central monitoring system. 
           [0034]      FIG. 14  is a flowchart showing one embodiment of an instruction loop for an ECRV or zone thermostat. 
           [0035]      FIG. 15  is a flowchart showing one embodiment of an instruction and sensor data loop for an ECRV or zone thermostat. 
           [0036]      FIG. 16  is a flowchart showing one embodiment of an instruction and sensor data reporting loop for an ECRV or zone thermostat. 
           [0037]      FIG. 17  shows an ECRV configured to be used in connection with a conventional T-bar ceiling system found in many commercial structures. 
           [0038]      FIG. 18  shows an ECRV configured to use a scrolling curtain to control airflow as an alternative to the vanes shown in  FIGS. 2 and 3 . 
           [0039]      FIG. 19  is a block diagram of a control algorithm for controlling the register vents. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]      FIG. 1  shows a home  100  with zoned heating and cooling. In the home  100 , an HVAC system provides heating and cooling air to a system of ducts. Sensors  101 - 105  monitor the temperature in various areas (zones) of the house. A zone can be a room, a floor, a group of rooms, etc. The sensors  101 - 105  detect where and when heating or cooling air is needed. Information from the sensors  101 - 105  is used to control actuators that adjust the flow of air to the various zones. The zoned system adapts to changing conditions in one area without affecting other areas. For example, many two-story houses are zoned by floor. Because heat rises, the second floor usually requires more cooling in the summer and less heating in the winter than the first floor. A non-zoned system cannot completely accommodate this seasonal variation. Zoning, however, can reduce the wide variations in temperature between floors by supplying heating or cooling only to the space that needs it. 
         [0041]      FIG. 2  shows one example of a conventional manually-controlled register vent  200 . The register  200  includes one or more vanes  201  that can be opened or closed to adjust the amount of air that flows through the register  200 . Diverters  202  direct the air in a desired direction (or directions). The vanes  201  are typically provided to a mechanical mechanism so that the occupants can manipulate the vanes  201  to control the amount of air that flows out of the register  200 . In some registers, the diverters  202  are fixed. In some registers, the diverters  202  are moveable to allow the occupants some control over the direction of the airflow out of the vent. Registers such as the register  200  are found throughout homes that have a central HVAC system that provides heating and cooling air. Typically, relatively small rooms such as bedrooms and bathrooms will have one or two such register vents of varying sizes. Larger rooms, such as living rooms, family rooms, etc., may have more than two such registers. The occupants of a home can control the flow of air through each of the vents by manually adjusting the vanes  201 . When the register vent is located on the floor, or relatively low on the wall, such adjustment is usually not particularly difficult (unless the mechanism that controls the vanes  201  is bent or rusted). However, adjustment of the vanes  201  can be very difficult when the register vent  200  is located so high on the wall that it cannot be easily reached. 
         [0042]      FIG. 3  shows one embodiment of an Electronically-Controlled Register Vent (ECRV)  300 . The ECRV  300  can be used to implement a zoned heating and cooling system. The ECRV  300  can also be used as a remotely control register vent in places where the vent is located so high on the wall that is cannot be easily reached. The ECRV  300  is configured as a replacement for the vent  200 . This greatly simplifies the task of retrofitting a home by replacing one or more of the register vents  200  with the ECRVs  300 . In one embodiment, shown in  FIG. 3 , the ECRV  300  is configured to fit into approximately the same size duct opening as the conventional register vent  200 . In one embodiment, the ECRV  300  is configured to fit over the duct opening used by the conventional register vent  200 . In one embodiment, the ECRV  300  is configured to fit over the conventional register  200 , thereby allowing the register  200  to be left in place. A control panel  301  provides one or more visual displays and, optionally, one or more user controls. A housing  302  is provided to house an actuator to control the vanes  201 . In one embodiment, the housing  302  can also be used to house electronics, batteries, etc. 
         [0043]      FIG. 4  is a block diagram of a self-contained ECRV  400 , which is one embodiment of the ECRV  300  shown in  FIGS. 3A and 3B  and the ECRV shown in  FIG. 18 . In the ECRV  400 , a temperature sensor  406  and a temperature sensor  416  are provided to a controller  401 . The controller  401  controls an actuator system  409 . In one embodiment, the actuator  409  provides position feedback to the controller  401 . In one embodiment, the controller  401  reports actuator position to a central control system and/or zone thermostat. The actuator system  409  provided mechanical movements to control the airflow through the vent. In one embodiment, the actuator system  409  includes an actuator provided to the vanes  201  or other air-flow devices to control the amount of air that flows through the ECRV  400  (e.g., the amount of air that flows from the duct into the room). In one embodiment, an actuator system includes an actuator provided to one or more of the diverters  202  to control the direction of the airflow. The controller  401  also controls a visual display  403  and an optional fan  402 . A user input device  408  is provided to allow the user to set the desired room temperature. An optional sensor  407  is provided to the controller  401 . In one embodiment, the sensor  407  includes an air pressure and/or airflow sensor. In one embodiment, the sensor  407  includes a humidity sensor. A power source  404  provides power to the controller  401 , the fan  402 , the display  403 , the temperature sensors  406 ,  416 , the sensor  407 , and the user input device  408  as needed. In one embodiment, the controller  401  controls the amount of power provided to the fan  402 , the display  403 , the sensor  406 , the sensor  416 , the sensor  407 , and the user input device  408 . In one embodiment, an optional auxiliary power source  405  is also provided to provide additional power. The auxiliary power source is a supplementary source of electrical power, such as, for example, a battery, a solar cell, an airflow (e.g., wind-powered) generator, the fan  402  acting as a generator, a nuclear-based electrical generator, a fuel cell, a thermocouple, etc. 
         [0044]    In one embodiment, the power source  404  is based on a non-rechargeable battery and the auxiliary power source  405  includes a solar cell and a rechargeable battery. The controller  401  draws power from the auxiliary power source when possible to conserve power in the power source  404 . When the auxiliary power source  405  is unable to provide sufficient power, then the controller  401  also draws power from the power source  404 . 
         [0045]    In an alternative embodiment, the power source  404  is configured as a rechargeable battery and the auxiliary power source  405  is configured as a solar cell that recharges the power source  404 . 
         [0046]    In one embodiment, the display  403  includes a flashing indicator (e.g., a flashing LED or LCD) when the available power from the power sources  404  and/or  405  drops below a threshold level. 
         [0047]    The home occupants use the user input device  408  to set a desired temperature for the vicinity of the ECRV  400 . The display  403  shows the setpoint temperature. In one embodiment, the display  403  also shows the current room temperature. The temperature sensor  406  measures the temperature of the air in the room, and the temperature sensor  416  measures the temperature of the air in the duct. If the room temperature is above the setpoint temperature, and the duct air temperature is below the room temperature, then the controller  401  causes the actuator  409  to open the vent. If the room temperature is below the setpoint temperature, and the duct air temperature is above the room temperature, then the controller  401  causes the actuator  409  to open the vent. Otherwise, the controller  401  causes the actuator  409  to close the vent. In other words, if the room temperature is above or below the setpoint temperature and the temperature of the air in the duct will tend to drive the room temperature towards the setpoint temperature, then the controller  401  opens the vent to allow air into the room. By contrast, if the room temperature is above or below the setpoint temperature and the temperature of the air in the duct will not tend to drive the room temperature towards the setpoint temperature, then the controller  401  closes the vent. 
         [0048]    In one embodiment, the controller  401  is configured to provide a few degrees of hysteresis (often referred to as a thermostat deadband) around the setpoint temperature in order to avoid wasting power by excessive opening and closing of the vent. 
         [0049]    In one embodiment, the controller  401  turns on the fan  402  to pull additional air from the duct. In one embodiment, the fan  402  is used when the room temperature is relatively far from the setpoint temperature in order to speed the movement of the room temperature towards the setpoint temperature. In one embodiment, the fan  402  is used when the room temperature is changing relatively slowly in response to the open vent. In one embodiment, the fan  402  is used when the room temperature is moving away from the setpoint and the vent is fully open. The controller  401  does not turn on or run the fan  402  unless there is sufficient power available from the power sources  404 ,  405 . In one embodiment, the controller  401  measures the power level of the power sources  404 ,  405  before turning on the fan  402 , and periodically (or continually) when the fan is on. 
         [0050]    In one embodiment, the controller  401  also does not turn on the fan  402  unless it senses that there is airflow in the duct (indicating that the HVAC air-handler fan is blowing air into the duct). In one embodiment, the sensor  407  includes an airflow sensor. In one embodiment, the controller  401  uses the fan  402  as an airflow sensor by measuring (or sensing) voltage generated by the fan  402  rotating in response to air flowing from the duct through the fan and causing the fan to act as a generator. In one embodiment, the controller  401  periodically stop the fan and checks for airflow from the duct. 
         [0051]    In one embodiment, the sensor  406  includes a pressure sensor configured to measure the air pressure in the duct. In one embodiment, the sensor  406  includes a differential pressure sensor configured to measure the pressure difference between the air in the duct and the air outside the ECRV (e.g., the air in the room). Excessive air pressure in the duct is an indication that too many vents may be closed (thereby creating too much back pressure in the duct and reducing airflow through the HVAC system). In one embodiment, the controller  401  opens the vent when excess pressure is sensed. 
         [0052]    The controller  401  conserves power by turning off elements of the ECRV  400  that are not in use. The controller  401  monitors power available from the power sources  404 ,  405 . When available power drops below a low-power threshold value, the controls the actuator  409  to an open position, activates a visual indicator using the display  403 , and enters a low-power mode. In the low power mode, the controller  401  monitors the power sources  404 ,  405  but the controller does not provide zone control functions (e.g., the controller does not close the actuator  409 ). When the controller senses that sufficient power has been restored (e.g., through recharging of one or more of the power sources  404 ,  405 , then the controller  401  resumes normal operation. 
         [0053]    Whistling and other noises related to turbulence can be a problem when air of a certain velocity passes through an orifice or opening In one embodiment, the controller  401  uses the physical parameters of the vent to estimate when airflow through the vent may cause undesirable noises such as whistling and the like. The controller  401  can then avoid relatively small vent openings (e.g., smaller partial openings) of the vent that produce unacceptable noises. Since whistling and other such noises are dependent on how much the vent is open and the air pressure across the vent, the openings that would cause unacceptable noises may vary depending on which other vents in the zone system are open or closed. By using data from the pressure/airflow sensor  407  and the dimensions of the vent, the controller  401  can calculate which settings are likely to produce whistling and other noises at any given time and thus, vary the allowed settings accordingly. In one embodiment, a microphone or other acoustic sensor is provided to the controller  401  such that the controller can sense acoustic noise created by air flowing through the vent. In one embodiment, the controller evaluates the amplitude of the noise detected by the acoustic sensor to determine whether unacceptable noise is being produced. In one embodiment, the controller  401  performs spectral properties of the noise (e.g., by using Fourier transform, wavelet transform, etc.) to determine whether unacceptable noise is being produced. The use of a booster fan in connection with the ECRV increases the possibility of noise. The controller  401  can also use noise estimates or measurements to help determine if a booster fan and/or the allowable speed for the fan. 
         [0054]    If too many vents are closed off, then the remaining vents, even when completely open, may cause unacceptable noises. In one embodiment, the controller  401  informs the zone thermostats and/or control systems described below that a vent is producing noise. The zone thermostat and/or control system can then open other vents to reduce the pressure, instruct the blower fan to operate at a lower speed, turn off or reduce the speed of booster fans in the ductwork, etc. 
         [0055]      FIG. 5  is a block diagram of a self-contained ECRV  500  with a remote control interface  501 . The ECRV  500  includes the power sources  404 ,  405 , the controller  401 , the fan  402 , the display  403 , the temperature sensors  406 ,  416 , the sensor  407 , and the user input device  408 . The remote control interface  501  is provided to the controller  401 , to allow the controller  401  to communicate with a remote control  502 . The controller  502  sends wireless signals to the remote control interface  501  using wireless communication such as, for example, infrared communication, ultrasonic communication, and/or radio-frequency communication. 
         [0056]    In one embodiment, the communication is one-way, from the remote control  502  to the controller  401 . The remote control  502  can be used to set the temperature setpoint, to instruct the controller  401  to open or close the vent (either partially or fully), and/or to turn on the fan. In one embodiment, the communication between the remote control  502  and the controller  401  is two-way communication. Two-way communication allows the controller  401  to send information for display on the remote control  502 , such as, for example, the current room temperature, the power status of the power sources  404 ,  405 , diagnostic information, etc. 
         [0057]    The ECRV  400  described in connection with  FIG. 4 , and the ECRV  500  described in connection with  FIG. 5  are configured to operate as self-contained devices in a relatively stand-alone mode. If two ECRVs  400 ,  500  are placed in the same room or zone, the ECRVs  400 ,  500  will not necessarily operate in unison.  FIG. 6  is a block diagram of a locally-controlled zoned heating and cooling system  600  wherein a zone thermostat  601  monitors the temperature of a zone  608 . ECRVs  602 ,  603  are configured to communicate with the zone thermostat  601 . One embodiment of the ECRVs  620 - 603  is shown, for example, in connection with  FIG. 10 . In one embodiment, the zone thermostat  601  sends control commands to the ECRVs  602 - 603  to cause the ECRVs  602 - 603  to open or close. In one embodiment, the zone thermostat  601  sends temperature information to the ECRVs  602 - 603  and the ECRVs  602 - 603  determine whether to open or close based on the temperature information received from the zone thermostat  601 . In one embodiment, the zone thermostat  601  sends information regarding the current zone temperature and the setpoint temperature to the ECRVs  602 - 603 . 
         [0058]    In one embodiment, the ECRV  602  communicates with the ECRV  603  in order to improve the robustness of the communication in the system  600 . Thus, for example, if the ECRV  602  is unable to communicate with the zone thermostat  601  but is able to communicate with the ECRV  603 , then the ECRV  603  can act as a router between the ECRV  602  and the zone thermostat  601 . In one embodiment, the ECRV  602  and the ECRV  603  communicate to arbitrate opening and closing of their respective vents. 
         [0059]    The system  600  shown in  FIG. 6  provides local control of a zone  608 . Any number of independent zones can be controlled by replicating the system  600 .  FIG. 7A  is a block diagram of a centrally-controlled zoned heating and cooling system wherein a central control system  710  communicates with one or more zone thermostats  707   708  and one or more ECRVs  702 - 705 . In the system  700 , the zone thermostat  707  measures the temperature of a zone  711 , and the ECRVs  702 ,  703  regulate air to the zone  711 . The zone thermostat  708  measures the temperature of a zone  712 , and the ECRVs  704 ,  705  regulate air to the zone  711 . A central thermostat  720  controls the HVAC system  720 . 
         [0060]      FIG. 7B  is a block diagram of a centrally-controlled zoned heating and cooling system  750  that is similar to the system  700  shown in  FIG. 7A . In  FIG. 7B , the central system  710  communicates with the zone thermostats  707 ,  708 , the zone thermostat  707  communicates with the ECRVs  702 ,  703 , the zone thermostat  708  communicates with the ECRVs  704 ,  705 , and the central system  710  communicates with the ECRVs  706 ,  707 . In the system  750 , the ECRVs  702 - 705  are in zones that are associated with the respective zone thermostat  707 ,  708  that controls the respective ECRVs  702 - 705 . The ECRVs  706 ,  707  are not associated with any particular zone thermostat and are controlled directly by the central system  710 . One of ordinary skill in the art will recognize that the communication topology shown in  FIG. 7B  can also be used in connection with the system shown in  FIGS. 8 and 9 . 
         [0061]    The central system  710  controls and coordinates the operation of the zones  711  and  712 , but the system  710  does not control the HVAC system  721 . In one embodiment, the central system  710  operates independently of the thermostat  720 . In one embodiment, the thermostat  720  is provided to the central system  710  so that the central system  710  knows when the thermostat is calling for heating, cooling, or fan. 
         [0062]    The central system  710  coordinates and prioritizes the operation of the ECRVs  702 - 705 . In one embodiment, the home occupants and provide a priority schedule for the zones  711 ,  712  based on whether the zones are occupied, the time of day, the time of year, etc. Thus, for example, if zone  711  corresponds to a bedroom and zone  712  corresponds to a living room, zone  711  can be given a relatively lower priority during the day and a relatively higher priority during the night. As a second example, if zone  711  corresponds to a first floor, and zone  712  corresponds to a second floor, then zone  712  can be given a higher priority in summer (since upper floors tend to be harder to cool) and a lower priority in winter (since lower floors tend to be harder to heat). In one embodiment, the occupants can specify a weighted priority between the various zones. 
         [0063]    Closing too many vents at one time is often a problem for central HVAC systems as it reduces airflow through the HVAC system, and thus reduces efficiency. The central system  710  can coordinate how many vents are closed (or partially closed) and thus, ensure that enough vents are open to maintain proper airflow through the system. The central system  710  can also manage airflow through the home such that upper floors receive relatively more cooling air and lower floors receive relatively more heating air. 
         [0064]      FIG. 8  is a block diagram of a centrally-controlled zoned heating and cooling system  800 . The system  800  is similar to the system  700  and includes the zone thermostats  707 ,  708  to monitor the zones  711 ,  712 , respectively, and the ECRVs  702 - 705 . The zone thermostats  707 ,  708  and/or the ECRVs  702 - 705  communicate with a central controller  810 . In the system  800 , the thermostat  720  is provided to the central system  810  and the central system  810  controls the HVAC system  721  directly. 
         [0065]    The controller  810  provides similar functionality as the controller  710 . However, since the controller  810  also controls the operation of the HVAC system  721 , the controller  810  is better able to call for heating and cooling as needed to maintain the desired temperature of the zones  711 ,  712 . If all, or substantially, all of the home is served by the zone thermostats and ECRVs, then the central thermostat  720  can be eliminated. 
         [0066]    In some circumstances, depending on the return air paths in the house, the controller  810  can turn on the HVAC fan (without heating or cooling) to move air from zones that are too hot to zones that are too cool (or vice versa) without calling for heating or cooling. The controller  810  can also provide for efficient use of the HVAC system by calling for heating and cooling as needed, and delivering the heating and cooling to the proper zones in the proper amounts. If the HVAC system  721  provides multiple operating modes (e.g., high-speed, low-speed, etc.), then the controller  810  can operate the HVAC system  721  in the most efficient mode that provides the amount of heating or cooling needed. 
         [0067]      FIG. 9  is a block diagram of an efficiency-monitoring centrally-controlled zoned heating and cooling system  900 . The system  900  is similar to the system  800 . In the system  900  the controller  810  is replaced by an efficiency-monitoring controller  910  that is configured to receive sensor data (e.g., system operating temperatures, etc.) from the HVAC system  721  to monitor the efficiency of the HVAC system  721 . 
         [0068]      FIG. 10  is a block diagram of an ECRV  1000  for use in connection with the systems shown in  FIGS. 6-9 . The ECRV  1000  includes the power sources  404 ,  405 , the controller  401 , the fan  402 , the display  403 , and, optionally the temperature sensors  416  and the sensor  407 , and the user input device  408 . A communication system  1081  is provided to the controller  401 . The remote control interface  501  is provided to the controller  401 , to allow the controller  401  to communicate with a remote control  502 . The controller  502  sends wireless signals to the remote control interface  501  using wireless communication such as, for example, infrared communication, ultrasonic communication, and/or radio-frequency communication. 
         [0069]    The communication system  1081  is configured to communicate with the zone thermometer and, optionally, with the central controllers  710 ,  810 ,  910 . In one embodiment, the communication system  1081  is configured to communicate using wireless communication such as, for example, infrared communication, radio communication, or ultrasonic communication. 
         [0070]      FIG. 11  is a block diagram of a basic zone thermostat  1100  for use in connection with the systems shown in  FIGS. 6-9 . In the zone thermostat  1100 , a temperature sensor  1102  is provided to a controller  1101 . User input controls  1103  are also provided to the controller  1101  to allow the user to specify a setpoint temperature. A visual display  1110  is provided to the controller  1101 . The controller  1101  uses the visual display  1110  to show the current temperature, setpoint temperature, power status, etc. The communication system  1181  is also provided to the controller  1101 . The power source  404  and, optionally,  405  are provided to provide power for the controller  1100 , the controls  1101 , the sensor  1103 , the communication system  1181 , and the visual display  1110 . 
         [0071]    In systems where a central controller  710 ,  810 ,  910  is used, the communication method used by the zone thermostat  1100  to communicate with the ECRV  1000  need not be the same method used by the zone thermostat  1100  to communicate with the central controller  710 ,  810 ,  910 . Thus, in one embodiment, the communication system  1181  is configured to provide one type of communication (e.g., infrared, radio, ultrasonic) with the central controller, and a different type of communication with the ECRV  1000 . 
         [0072]    In one embodiment, the zone thermostat is battery powered. In one embodiment, the zone thermostat is configured into a standard light switch and receives electrical power from the light switch circuit. 
         [0073]      FIG. 12  is a block diagram of a zone thermostat  1200  with remote control for use in connection with the systems shown in  FIGS. 6-9 . The thermostat  1200  is similar to the thermostat  1100  and includes, the temperature sensor  1102 , the input controls  1103 , the visual display  1110 , the communication system  1181 , and the power sources  404 ,  405 . In the zone thermostat  1200 , the remote control interface  501  is provided to the controller  1101 . 
         [0074]    In one embodiment, an occupant sensor  1201  is provided to the controller  1101 . The occupant sensor  1201 , such as, for example, an infrared sensor, motion sensor, ultrasonic sensor, etc. senses when the zone is occupied. The occupants can program the zone thermostat  1201  to bring the zone to different temperatures when the zone is occupied and when the zone is empty. In one embodiment, the occupants can program the zoned thermostat  1201  to bring the zone to different temperatures depending on the time of day, the time of year, the type of room (e.g. bedroom, kitchen, etc.), and/or whether the room is occupied or empty. In one embodiment, a group of zones are combined into a composite zone (e.g., a group of zones such as an entire house, an entire floor, an entire wing, etc.) and the central system  710 ,  810 ,  910  changes the temperature setpoints of the various zones according to whether the composite zone is empty or occupied. 
         [0075]      FIG. 13  shows one embodiment of a central monitoring station console  1300  for accessing the functions represented by the blocks  710 ,  810 ,  910  in  FIGS. 7, 8, 9 , respectively. The station  1300  includes a display  1301  and a keypad  1302 . The occupants can specify zone temperature settings, priorities, and thermostat deadbands using the central system  1300  and/or the zone thermostats. In one embodiment, the console  1300  is implemented as a hardware device. In one embodiment, the console  1300  is implemented in software as a computer display, such as, for example, on a personal computer. In one embodiment, the zone control functions of the blocks  710 ,  810 ,  910  are provided by a computer program running on a control system processor, and the control system processor interfaces with personal computer to provide the console  1300  on the personal computer. In one embodiment, the zone control functions of the blocks  710 ,  810 ,  910  are provided by a computer program running on a control system processor provided to a hardware console  1300 . In one embodiment, the occupants can use the Internet, telephone, cellular telephone, pager, etc. to remotely access the central system to control the temperature, priority, etc. of one or more zones. 
         [0076]      FIG. 14  is a flowchart showing one embodiment of an instruction loop process  1400  for an ECRV or zone thermostat. The process  1400  begins at a power-up block  1401 . After power up, the process proceeds to an initialization block  1402 . After initialization, the process advances to a “listen” block  1403  wherein the ECRV or zone thermostat listens for one or more instructions. If a decision block  1404  determines that an instruction has been received, then the process advances to a “perform instruction” block  1405 , otherwise the process returns to the listen block  1403 . 
         [0077]    For an ECRV, the instructions can include: open vent, close vent, open vent to a specified partially-open position, report sensor data (e.g., airflow, temperature, etc.), report status (e.g., battery status, vent position, etc.), and the like. For a zone thermostat, the instructions can include: report temperature sensor data, report temperature rate of change, report setpoint, report status, etc. In systems where the central system communicates with the ECRVs through a zone thermostat, the instructions can also include: report number of ECRVs, report ECRV data (e.g., temperature, airflow, etc.), report ECRV vent position, change ECRV vent position, etc. 
         [0078]    In one embodiment, the listen block  1403  consumes relatively little power, thereby allowing the ECRV or zone thermostat to stay in the loop corresponding to the listen block  1403  and conditional branch  1404  for extended periods of time. 
         [0079]    Although the listen block  1403  can be implemented to use relatively little power, a sleep block can be implemented to use even less power.  FIG. 15  is a flowchart showing one embodiment of an instruction and sensor data loop process  1500  for an ECRV or zone thermostat. The process  1500  begins at a power-up block  1501 . After power up, the process proceeds to an initialization block  1502 . After initialization, the process advances to a “sleep” block  1503  wherein the ECRV or zone thermostat sleeps for a specified period of time. When the sleep period expires, the process advances to a wakeup block  1504  and then to a decision  1505 . In the decision block  1505 , if a fault is detected, then a transmit fault block  1506  is executed. The process then advances to a sensor block  1507  where sensor readings are taken. After taking sensor readings, the process advances to a listen-for-instructions block  1508 . If an instruction has been received, then the process advances to a “perform instruction” block  1510 ; otherwise, the process returns to the sleep block  1503 . 
         [0080]      FIG. 16  is a flowchart showing one embodiment of an instruction and sensor data reporting loop process  1600  for an ECRV or zone thermostat. The process  1600  begins at a power-up block  1601 . After power up, the process proceeds to an initialization block  1602 . After initialization, the process advances to a check fault block  1603 . If a fault is detected then a decision block  1604  advances the process to a transmit fault block  1605 ; otherwise, the process advances to a sensor block  1606  where sensor readings are taken. The data values from one or more sensors are evaluated, and if the sensor data is outside a specified range, or if a timeout period has occurred, then the process advances to a transmit data block  1608 ; otherwise, the process advances to a sleep block  1609 . After transmitting in the transmit fault block  1605  or the transmit sensor data block  1608 , the process advances to a listen block  1610  where the ECRV or zone thermostat listens for instructions. If an instruction is received, then a decision block advances the process to a perform instruction block  1612 ; otherwise, the process advances to the sleep block  1609 . After executing the perform instruction block  1612 , the process transmits an “instruction complete message” and returns to the listen block  1610 . 
         [0081]    The process flows shown in  FIGS. 14-16  show different levels of interaction between devices and different levels of power conservation in the ECRV and/or zone thermostat. One of ordinary skill in the art will recognize that the ECRV and zone thermostat are configured to receive sensor data and user inputs, report the sensor data and user inputs to other devices in the zone control system, and respond to instructions from other devices in the zone control system. Thus the process flows shown in  FIGS. 14-16  are provided for illustrative purposes and not by way of limitation. Other data reporting and instruction processing loops will be apparent to those of ordinary skill in the art by using the disclosure herein. 
         [0082]    In one embodiment, the ECRV and/or zone thermostat “sleep,” between sensor readings. In one embodiment, the central system  710  sends out a “wake up” signal. When an ECRV or zone thermostat receives a wake up signal, it takes one or more sensor readings, encodes it into a digital signal, and transmits the sensor data along with an identification code. 
         [0083]    In one embodiment, the ECRV is bi-directional and configured to receive instructions from the central system. Thus, for example, the central system can instruct the ECRV to: perform additional measurements; go to a standby mode; wake up; report battery status; change wake-up interval; run self-diagnostics and report results; etc. 
         [0084]    In one embodiment, the ECRV provides two wake-up modes, a first wake-up mode for taking measurements (and reporting such measurements if deemed necessary), and a second wake-up mode for listening for commands from the central system. The two wake-up modes, or combinations thereof, can occur at different intervals. 
         [0085]    In one embodiment, the ECRVs use spread-spectrum techniques to communicate with the zone thermostats and/or the central system. In one embodiment, the ECRVs use frequency-hopping spread-spectrum. In one embodiment, each ECRV has an Identification code (ID) and the ECRVs attaches its ID to outgoing communication packets. In one embodiment, when receiving wireless data, each ECRV ignores data that is addressed to other ECRVs. 
         [0086]    In one embodiment, the ECRV provides bi-directional communication and is configured to receive data and/or instructions from the central system. Thus, for example, the central system can instruct the ECRV to perform additional measurements, to go to a standby mode, to wake up, to report battery status, to change wake-up interval, to run self-diagnostics and report results, etc. In one embodiment, the ECRV reports its general health and status on a regular basis (e.g., results of self-diagnostics, battery health, etc.). 
         [0087]    In one embodiment, the ECRV use spread-spectrum techniques to communicate with the central system. In one embodiment, the ECRV uses frequency-hopping spread-spectrum. In one embodiment, the ECRV has an address or identification (ID) code that distinguishes the ECRV from the other ECRVs. The ECRV attaches its ID to outgoing communication packets so that transmissions from the ECRV can be identified by the central system. The central system attaches the ID of the ECRV to data and/or instructions that are transmitted to the ECRV. In one embodiment, the ECRV ignores data and/or instructions that are addressed to other ECRVs. 
         [0088]    In one embodiment, the ECRVs, zone thermostats, central system, etc., communicate on a 900 MHz frequency band. This band provides relatively good transmission through walls and other obstacles normally found in and around a building structure. In one embodiment, the ECRVs and zone thermostats communicate with the central system on bands above and/or below the 900 MHz band. In one embodiment, the ECRVs and zone thermostats listen to a radio frequency channel before transmitting on that channel or before beginning transmission. If the channel is in use, (e.g., by another device such as another central system, a cordless telephone, etc.) then the ECRVs and/or zone thermostats change to a different channel. In one embodiment, the sensor, central system coordinates frequency hopping by listening to radio frequency channels for interference and using an algorithm to select a next channel for transmission that avoids the interference. In one embodiment, the ECRV and/or zone thermostat transmits data until it receives an acknowledgement from the central system that the message has been received. 
         [0089]    Frequency-hopping wireless systems offer the advantage of avoiding other interfering signals and avoiding collisions. Moreover, there are regulatory advantages given to systems that do not transmit continuously at one frequency. Channel-hopping transmitters change frequencies after a period of continuous transmission, or when interference is encountered. These systems may have higher transmit power and relaxed limitations on in-band spurs. 
         [0090]    In one embodiment, the controller  401  reads the sensors  406 ,  407 ,  416  at regular periodic intervals. In one embodiment, the controller  401  reads the sensors  406 ,  407 ,  416  at random intervals. In one embodiment, the controller  401  reads the sensors  406 ,  407 ,  416  in response to a wake-up signal from the central system. In one embodiment, the controller  401  sleeps between sensor readings. 
         [0091]    In one embodiment, the ECRV transmits sensor data until a handshaking-type acknowledgement is received. Thus, rather than sleep if no instructions or acknowledgements are received after transmission (e.g., after the instruction block  1510 ,  1405 ,  1612  and/or the transmit blocks  1605 ,  1608 ) the ECRV retransmits its data and waits for an acknowledgement. The ECRV continues to transmit data and wait for an acknowledgement until an acknowledgement is received. In one embodiment, the ECRV accepts an acknowledgement from a zone thermometer and it then becomes the responsibility of the zone thermometer to make sure that the data is forwarded to the central system. The two-way communication ability of the ECRV and zone thermometer provides the capability for the central system to control the operation of the ECRV and/or zone thermometer and also provides the capability for robust handshaking-type communication between the ECRV, the zone thermometer, and the central system. 
         [0092]    In one embodiment of the system  600  shown in  FIG. 6 , the ECRVs  602 ,  603  send duct temperature data to the zone thermostat  601 . The zone thermostat  601  compares the duct temperature to the room temperature and the setpoint temperature and makes a determination as to whether the ECRVs  602 ,  603  should be open or closed. The zone thermostat  601  then sends commands to the ECRVs  602 ,  603  to open or close the vents. In one embodiment, the zone thermostat  601  displays the vent position on the visual display  1110 . 
         [0093]    In one embodiment of the system  600  shown in  FIG. 6 , the zone thermostat  601  sends setpoint information and current room temperature information to the ECRVs  602 ,  603 . The ECRVs  602 ,  603  compare the duct temperature to the room temperature and the setpoint temperature and makes a determination as to whether to open or close the vents. In one embodiment, the ECRVs  602 ,  603  send information to the zone thermostat  601  regarding the relative position of the vents (e.g., open, closed, partially open, etc.). 
         [0094]    In the systems  700 ,  750 ,  800 ,  900  (the centralized systems) the zone thermostats  707 ,  708  send room temperature and setpoint temperature information to the central system. In one embodiment, the zone thermostats  707 ,  708  also send temperature slope (e.g., temperature rate of rise or fall) information to the central system. In the systems where the thermostat  720  is provided to the central system or where the central system controls the HVAC system, the central system knows whether the HVAC system is providing heating or cooling; otherwise, the central system used duct temperature information provide by the ECRVs  702 - 705  to determine whether the HVAC system is heating or cooling. In one embodiment, ECRVs send duct temperature information to the central system. In one embodiment, the central system queries the ECRVs by sending instructions to one or more of the ECRVs  702 - 705  instructing the ECRV to transmit its duct temperature. 
         [0095]    The central system determines how much to open or close ECRVs  702 - 705  according to the available heating and cooling capacity of the HVAC system and according to the priority of the zones and the difference between the desired temperature and actual temperature of each zone. In one embodiment, the occupants use the zone thermostat  707  to set the setpoint and priority of the zone  711 , the zone thermostat  708  to set the setpoint and priority of the zone  712 , etc. In one embodiment, the occupants use the central system console  1300  to set the setpoint and priority of each zone, and the zone thermostats to override (either on a permanent or temporary basis) the central settings. In one embodiment, the central console  1300  displays the current temperature, setpoint temperature, temperature slope, and priority of each zone. 
         [0096]    In one embodiment, the central system allocates HVAC air to each zone according to the priority of the zone and the temperature of the zone relative to the setpoint temperature of the zone. Thus, for example, in one embodiment, the central system provides relatively more HVAC air to relatively higher priority zones that are not at their temperature setpoint than to lower priority zones or zones that are at or relatively near their setpoint temperature. In one embodiment, the central system avoids closing or partially closing too many vents in order to avoid reducing airflow in the duct below a desired minimum value. 
         [0097]    In one embodiment, the central system monitors a temperature rate of rise (or fall) in each zone and sends commands to adjust the amount each ECRV  702 - 705  is open to bring higher priority zones to a desired temperature without allowing lower-priority zones to stray too far form their respective setpoint temperature. 
         [0098]    In one embodiment, the central system uses predictive modeling to calculate an amount of vent opening for each of the ECRVs  702 - 705  to reduce the number of times the vents are opened and closed and thereby reduce power usage by the actuators  409 . In one embodiment, the central system uses a neural network to calculate a desired vent opening for each of the ECRVs  702 - 705 . In one embodiment, various operating parameters such as the capacity of the central HVAC system, the volume of the house, etc., are programmed into the central system for use in calculating vent openings and closings. In one embodiment, the central system is adaptive and is configured to learn operating characteristics of the HVAC system and the ability of the HVAC system to control the temperature of the various zones as the ECRVs  702 - 705  are opened and closed. In an adaptive learning system, as the central system controls the ECRVs to achieve the desired temperature over a period of time, the central system learns which ECRVs need to be opened, and by how much, to achieve a desired level of heating and cooling for each zone. The use of such an adaptive central system is convenient because the installer is not required to program HVAC operating parameters into the central system. In one embodiment, the central system provides warnings when the HVAC system appears to be operating abnormally, such as, for example, when the temperature of one or more zones does not change as expected (e.g., because the HVAC system is not operating properly, a window or door is open, etc.). 
         [0099]    In one embodiment, the adaptation and learning capability of the central system uses different adaptation results (e.g., different coefficients) based on whether the HVAC system is heating or cooling, the outside temperature, a change in the setpoint temperature or priority of the zones, etc. Thus, in one embodiment, the central system uses a first set of adaptation coefficients when the HVAC system is cooling, and a second set of adaptation coefficients when the HVAC system is heating. In one embodiment, the adaptation is based on a predictive model. In one embodiment, the adaptation is based on a neural network. 
         [0100]      FIG. 17  shows an ECRV  1700  configured to be used in connection with a conventional T-bar ceiling system found in many commercial structures. In the ECRV  1700 , an actuator  1701  (as one embodiment of the actuator  409 ) is provided to a damper  1702 . The damper  1702  is provided to a diffuser  1703  that is configured to mount in a conventional T-bar ceiling system. The ECRV  1700  can be connected to a zoned thermostat or central system by wireless or wired communication. 
         [0101]    In one embodiment, the sensors  407  in the ECRVs include airflow and/or air velocity sensors. Data from the sensors  407  are transmitted by the ECRV to the central system. The central system uses the airflow and/or air velocity measurements to determine the relative amount of air through each ECRV. Thus, for example, by using airflow/velocity measurements, the central system can adapt to the relatively lower airflow of smaller ECRVs and ECRVs that are situated on the duct further from the HVAC blower than ECRVs which are located closer to the blower (the closer ECRVs tend to receive more airflow). 
         [0102]    In one embodiment, the sensors  407  include humidity sensors. In one embodiment, the zone thermostat  1100  includes a zone humidity sensor provided to the controller  1101 . The zone control system (e.g., the central system, the zone thermostat, and/or ECRV) uses humidity information from the humidity sensors to calculate zone comfort values and to adjust the temperature setpoint according to a comfort value. Thus, for example, in one embodiment during a summer cooling season, the zone control system lowers the zone temperature setpoint during periods of relative high humidity, and raises the zone setpoint during periods of relatively low humidity. In one embodiment, the zone thermostat allows the occupants to specify a comfort setting based on temperature and humidity. In one embodiment, the zone control system controls the HVAC system to add or remove humidity from the heating/cooling air. 
         [0103]      FIG. 18  shows a register vent  1800  configured to use a scrolling curtain  1801  to control airflow as an alternative to the vanes shown in  FIGS. 2 and 3 . An actuator  1802  (one embodiment of the actuator  409 ) is provided to the curtain  1801  to move the curtain  1801  across the register to control the size of a register airflow opening In one embodiment, the curtain  1801  is guided and held in position by a track  1803 . 
         [0104]    In one embodiment, the actuator  1802  is a rotational actuator and the scrolling curtain  1801  is rolled around the actuator  1802 , and the register vent  1800  is open and rigid enough to be pushed into the vent opening by the actuator  1802  when the actuator  1802  rotates to unroll the curtain  1801 . 
         [0105]    In one embodiment, the actuator  1802  is a rotational actuator and the scrolling curtain  1801  is rolled around the actuator  1802 , and the register vent  1800  is open and rigid enough to be pushed into the vent opening by the actuator  1802  when the actuator  1802  rotates to unroll the curtain  1801 . In one embodiment, the actuator  1802  is configured to  FIG. 19  is a block diagram of a control algorithm  1900  for controlling the register vents. For purposes of explanation, and not by way of limitation, the algorithm  1900  is described herein as running on the central system. However, one of ordinary skill in the art will recognize that the algorithm  1900  can be run by the central system, by the zone thermostat, by the ECRV, or the algorithm  1900  can be distributed among the central system, the zone thermostat, and the ECRV. In the algorithm  1900 , in a block  1901  of the algorithm  1900 , the setpoint temperatures from one or more zone thermostats are provided to a calculation block  1902 . The calculation block  1902  calculates the register vent settings (e.g., how much to open or close each register vent) according to the zone temperature, the zone priority, the available heating and cooling air, the previous register vent settings, etc. as described above. In one embodiment, the block  1902  uses a predictive model as described above. In one embodiment, the block  1902  calculates the register vent settings for each zone independently (e.g., without regard to interactions between zones). In one embodiment, the block  1902  calculates the register vent settings for each zone in a coupled-zone manner that includes interactions between zones. In one embodiment, the calculation block  1902  calculates new vent openings by taking into account the current vent openings and in a manner configured to minimize the power consumed by opening and closing the register vents. 
         [0106]    Register vent settings from the block  1902  are provided to each of the register vent actuators in a block  1903 , wherein the register vents are moved to new opening positions as desired (and, optionally, one or more of the fans  402  are turned on to pull additional air from desired ducts). After setting the new vent openings in the block  1903 , the process advances to a block  1904  where new zone temperatures are obtained from the zone thermostats (the new zone temperatures being responsive to the new register vent settings made in block  1903 ). The new zone temperatures are provided to an adaptation input of the block  1902  to be used in adapting a predictive model used by the block  1902 . The new zone temperatures also provided to a temperature input of the block  1902  to be used in calculating new register vent settings. 
         [0107]    As described above, in one embodiment, the algorithm used in the calculation block  1902  is configured to predict the ECRV opening needed to bring each zone to the desired temperature based on the current temperature, the available heating and cooling, the amount of air available through each ECRV, etc. The calculating block uses the prediction model to attempt to calculate the ECRV openings needed for relatively long periods of time in order to reduce the power consumed in unnecessarily by opening and closing the register vents. In one embodiment, the ECRVs are battery powered, and thus reducing the movement of the register vents extends the life of the batteries. In one embodiment, the block  1902  uses a predictive model that learns the characteristics of the HVAC system and the various zones and thus the model prediction tends to improve over time. 
         [0108]    In one embodiment, the zone thermostats report zone temperatures to the central system and/or the ECRVs at regular intervals. In one embodiment, the zone thermostats report zone temperatures to the central system and/or the ECRVs after the zone temperature has changed by a specified amount specified by a threshold value. In one embodiment, the zone thermostats report zone temperatures to the central system and/or the ECRVs in response to a request instruction from the central system or ECRV. 
         [0109]    In one embodiment, the zone thermostats report setpoint temperatures and zone priority values to the central system or ECRVs whenever the occupants change the setpoint temperatures or zone priority values using the user controls  1102 . In one embodiment, the zone thermostats report setpoint temperatures and zone priority values to the central system or ECRVs in response to a request instruction from the central system or ECRVs. 
         [0110]    In one embodiment, the occupants can choose the thermostat deadband value (e.g., the hysteresis value) used by the calculation block  1902 . A relatively larger deadband value reduces the movement of the register vent at the expense of larger temperature variations in the zone. 
         [0111]    In one embodiment, the ECRVs report sensor data (e.g., duct temperature, airflow, air velocity, power status, actuator position, etc.) to the central system and/or the zone thermostats at regular intervals. In one embodiment, the ECRVs report sensor data to the central system and/or the zone thermostats whenever the sensor data fails a threshold test (e.g., exceeds a threshold value, falls below a threshold value, falls inside a threshold range, or falls outside a threshold range, etc.). In one embodiment, the ECRVs report sensor data to the central system and/or the zone thermostats in response to a request instruction from the central system or zone thermostat. 
         [0112]    In one embodiment, the central system is shown in  FIGS. 7-9  is implemented in a distributed fashion in the zone thermostats  1100  and/or in the ECRVs. In the distributed system, the central system does not necessarily exists as a distinct device, rather, the functions of the central system can be are distributed in the zone thermostats  1100  and/or the ECRVs. Thus, in a distributed system,  FIGS. 7-9  represent a conceptual/computational model of the system. For example, in a distributed system, each zone thermostat  100  knows its zone priority, and the zone thermostats  1100  in the distributed system negotiate to allocate the available heating/cooling air among the zones. In one embodiment of a distributed system, one of the zone thermostat assumes the role of a master thermostat that collects data from the other zone thermostats and implements the calculation block  1902 . In one embodiment of a distributed system, the zone thermostats operate in a peer-to-peer fashion, and the calculation block  1902  is implemented in a distributed manner across a plurality of zone thermostats and/or ECRVs. 
         [0113]    In one embodiment, the fans  402  can be used as generators to provide power to recharge the power source  404  in the ECRV. However, using the fan  402  in such a manner restricts airflow through the ECRV. In one embodiment, the controller  401  calculates a vent opening for the ECRV to produce the desired amount of air through the ECRV while using the fan to generate power to recharge the power source  404  (thus, in such circumstance) the controller would open the vanes more than otherwise necessary in order to compensate for the air resistance of the generator fan  402 . In one embodiment, in order to save power in the ECRV, rather than increase the vane opening, the controller  401  can use the fan as a generator. The controller  401  can direct the power generated by the fan  402  into one or both of the power sources  404 ,  405 , or the controller  401  can dump the excess power from the fan into a resistive load. In one embodiment, the controller  401  makes decisions regarding vent opening versus fan usage. In one embodiment, the central system instructs the controller  401  when to use the vent opening and when to use the fan. In one embodiment, the controller  401  and central system negotiate vent opening versus fan usage. 
         [0114]    In one embodiment, the ECRV reports its power status to the central system or zone thermostat. In one embodiment the central system or zone thermostat takes such power status into account when determining new ECRV openings. Thus, for example, if there are first and second ECRVs serving one zone and the central system knows that the first ECRVs is low on power, the central system will use the second ECRV to modulate the air into the zone. If the first ECRV is able to use the fan  402  or other airflow-based generator to generate electrical power, the central system will instruct the second ECRV to a relatively closed position in and direct relatively more airflow through the first ECRV when directing air into the zone. 
         [0115]    It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributed thereof; furthermore, various omissions, substitutions and changes may be made without departing from the spirit of the inventions. For example, although specific embodiments are described in terms of the 900 MHz frequency band, one of ordinary skill in the art will recognize that frequency bands above and below 900 MHz can be used as well. The wireless system can be configured to operate on one or more frequency bands, such as, for example, the HF band, the VHF band, the UHF band, the Microwave band, the Millimeter wave band, etc. One of ordinary skill in the art will further recognize that techniques other than spread spectrum can also be used and/or can be used instead spread spectrum. The modulation uses is not limited to any particular modulation method, such that modulation scheme used can be, for example, frequency modulation, phase modulation, amplitude modulation, combinations thereof, etc. The one or more of the wireless communication systems described above can be replaced by wired communication. The one or more of the wireless communication systems described above can be replaced by powerline networking communication. The foregoing description of the embodiments is, therefore, to be considered in all respects as illustrative and not restrictive, with the scope of the invention being delineated by the appended claims and their equivalents.