Patent Publication Number: US-2010114382-A1

Title: Determination of the Type of Heaving, Ventilating, and Air Conditioning (HVAC) System

Description:
BACKGROUND 
     The smart energy market often utilizes a wireless network to provide metering and energy management. Wireless networking include neighborhood area networks for meters, using wireless networking for sub-metering within a building, home or apartment and using wireless networking to communicate to devices within the home. Different installations and utility preferences often result in different network topologies and operation. However, each network typically operates using the same basic principals to ensure interoperability. Also, smart energy devices within a home may be capable of receiving public pricing information and messages from the metering network. However, these devices may not have or need all the capabilities required to join a smart energy network. 
     A smart energy network may assume different network types, including a utility private home area network (HAN), a utility private neighborhood area network (NAN), or a customer private HAN. A utility private HAN may include an in-home display or a load control device working in conjunction with an energy service portal (ESP), but typically does not include customer-controlled devices. 
     A smart energy network may interface with different types of devices including a heating, ventilating, and air conditioning (HVAC) system. With the increasing cost of energy, it is important that a HVAC system operates efficiently and reliably. Consequently, there is a real market need to provide information of different components in a HVAC system through a wireless network. 
     SUMMARY 
     The present invention provides apparatuses and computer readable media for obtaining information about a heating, ventilating, and air conditioning (HVAC) system and sending the information to a remote networked device. 
     With another aspect of the invention, a control circuit deactivates loads of a HVAC system so that a sampling circuit can inject a test signal into the loads. Based on a resulting signal, a processor determines what loads are connected to a thermostat. The processor can consequently determine the type of the HVAC system. 
     With another aspect of the invention, the processor may utilize a lookup table that maps possible values of the resulting signal with different types of HVAC systems. 
     With another aspect of the invention, the thermostat may send information about the load configuration to a networked device. The thermostat may further detect a change of the load configuration and notify the networked device. The thermostat may periodically inject the test signal into the connected loads when the control relays are deactivated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary of the invention, as well as the following detailed description of exemplary embodiments of the invention, is better understood when read in conjunction with the accompanying drawings, which are included by way of example, and not by way of limitation with regard to the claimed invention. 
         FIG. 1  shows a networked system for obtaining information for a heating, ventilating, and air conditioning (HVAC) system in accordance with an embodiment of the invention. 
         FIG. 2  shows a networking system with a thermostat that determines a type of HVAC system in accordance with an embodiment of the invention. 
         FIG. 3  shows a thermostat in accordance with an embodiment of the invention. 
         FIG. 4  shows a sampling circuit and control circuit in accordance with an embodiment of the invention. 
         FIG. 5  shows a flow diagram for determining the HVAC type in accordance with an embodiment of the invention. 
         FIG. 6  shows a lookup table for determining the HVAC type in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows networked system  100  for obtaining information for heating, ventilating, and air conditioning (HVAC) system  103  in accordance with an embodiment of the invention. HVAC system  103  typically includes different HVAC units such as fan  107 , heating unit (furnace)  109 , and cooling unit (air conditioner)  111 . Each HVAC unit may further have different components (not shown). For example, heating unit  109  may include a heat pump reverse valve, second stage heat pump, and emergency heat component. Cooling unit  111  may include a cooling reverse valve, and a cooling component. Each component, as will be discussed, may appear as a load to a controlling unit (e.g., a thermostat  101 ). 
     One the typical functions of thermostat  101  is to control HVAC system, e.g., activating cooling unit  111  when the measured temperature is too high or activating hating unit  109  when the measured temperature is too low. In addition, thermostat  101  may provide status information to networked device  105  through network  107 . For example, thermostat  101  may provide information to networked device  105  that is indicative of the type of HVAC system. Information about each component in HVAC system  103  may be important in managing and maintaining networked system  100 . For example, in a smart energy area, if the HVAC type is gas furnace, there is typically no need for the system to participate in electricity reduction program. 
     With some embodiments, network  107  supports a wireless protocol, including ZigBee™ or other IEEE 802.15.4 based protocols. Additional embodiments include supporting network protocols using a Wi-Fi® protocol, a Bluetooth® protocol, or using wired connections, such as 10 BASE-T or 100 BASE-T Ethernet. 
     HVAC information may be provided from thermostat  101  to monitoring device  105  in accordance with a ZigBee smart energy specification, e.g., Smart Energy Profile Specification, ZigBee Standards Organization, May 2008 and ZigBee Cluster Library Specification, ZigBee Standards Organization, May 2008, which are incorporated by reference. However, sending HVAC information from thermostat  101  to monitoring device  101  as manufacturing specific information (customer-defined cluster) in a data container (cluster), which may be conveyed by the payload of a ZigBee Cluster Library (ZCL) frame format, may be difficult to an end user because the specific data format is typically not published and thus not easily available to the end user. HVAC information may be facilitated by including HVAC information in a standard available cluster (publicly accessible cluster). 
     A smart energy networking system (e.g., system  100 ) typically includes a gateway, controller (e.g., networked device  105 ), display, and programmable control thermostat (e.g., thermostat  101 ). While the controller typically has the ability to configure the thermostat set point, setback, and heat/cool change over control, the controller may utilize information about the type of HVAC system that is connected to the thermostat. A traditional thermostat usually sets the end HVAC system through hard switches configured by an end user. However, with a traditional thermostat design, it may be difficult to determine what type of HVAC system is connected to the thermostat. With embodiments of the invention, the type of HVAC system is automatically determined. Consequently, information may be sent though network  107  from thermostat  101  to networked device  105  using a predefined data structure or encoded data. 
     There are many type of HVAC system now. Exemplary HVAC types include:
     Basic Heat   Basic Cool   Separated heat/cool system but connected to one thermostat   Heat Pump with Heat/Cool   Heat Pump with two stages heat and one cool   Heat Pump with two stages heat and two stages cool   Heat Pump with three stages heat and two stages cool   

       FIG. 2  shows a networking system with a thermostat  101  that determines a type of HVAC system in accordance with an embodiment of the invention. Thermostat  101  includes processor  201 , which instructs control circuit  205  to control HVAC system  103  in accordance with configuration data, including the temperature set point. As will be discussed further, processor  201  may instruct sampling circuit  203  to generate a test signal through the connected loads of HVAC system  103  when the loads have been deactivated by control circuit  205 . 
     Embodiments of the invention may include forms of computer-readable media as supported by memory  207 . Computer-readable media include any available media that can be accessed by processing circuit  201 . Computer-readable media may comprise storage media and communication media. Storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, object code, data structures, program modules, or other data. Communication media include any information delivery media and typically embody data in a modulated data signal such as a carrier wave or other transport mechanism. 
     A thermostat typically selects heating or cooling operation through a switch. In order to reduce the costs, using a switch arrangement can also eliminate a relay. However, a traditional thermostat typically cannot determine the type of HVAC system that the thermostat is connected to. 
       FIG. 3  shows a block diagram for thermostat  101  in accordance with an embodiment of the invention. With some embodiments of the invention, a sensing technique is used to detect the current flow through a switch/relay in order to determine the type of connected HVAC system.  FIG. 3  shows the general sensing circuitry block diagram according to an aspect of the invention. External loading  311  can be detected by enabling the sampling enable relay  307 , which activates the output status sampling circuitry  303 . The output status from sampling circuitry  303  reflects the zero crossing signal of the loading to the Microprocessor (MCU)  301 . By detecting different input signal simultaneously or using a multiplexer, the connected HVAC system can be detected automatically. 
     Processor  301  controls load  311  (which is typically one of plurality of loads contained in HVAC system  103 ) through output terminal  305  by activating/deactivating switch  309 . (Load  311  may correspond to a heat pump reverse valve, cooling reverse valve, second stage heat pump, emergency heat load, fan, or cooling load.) As will be further discussed, processor  301  may instruct sampling circuit  303  to generate a test signal through load  311  by activating switch  307  when switch  309  is deactivated. As will be further discussed, sampling circuit  303  consequently provides a result signal to processor  301  so that processor  301  can determine whether load  311  is connected to output terminal  305 . 
       FIG. 4  shows a sampling circuit and control circuit in accordance with an embodiment of the invention. R  423   a  and C  423   b  correspond to the 24 VAC input. Each output terminal connects to a corresponding HVAC load  409 - 415 , which is external to thermostat  101  and is typically contained in HVAC system  103 . The following control outputs correspond output terminals: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 B 417: 
                 Heat pump reverse valve 
               
               
                   
                 O 418: 
                 Cooling reverse valve 
               
               
                   
                 W2 419: 
                 Second stage heat pump 
               
               
                   
                 E 420: 
                 Emergency heat 
               
               
                   
                 G 421: 
                 Fan 
               
               
                   
                 Y1 422: 
                 Cooling 
               
               
                   
                 W1 416 
                 Conventional heat 
               
               
                   
                   
               
            
           
         
       
     
     With some embodiments, control relays  401 - 407  are single pole dual contact type relays, where each relay has contact  1  and contact  2 . During initialization, all relays  401 - 407  are reset to contact position  1  (shown in the up position as shown in  FIG. 4 ). Each relay controls HVAC load  409 - 415 , which may or may not be connected to thermostat  101  depending on the HVAC type. Each HVAC load is controlled by a corresponding control relay. For example, control relay  403  controls cooling reverse valve  418 . 
     During normal operation of thermostat  101 , OPT 1  switch  427  is turned off. Control relays  401 - 407  are turned on (ON) and off (OFF) according to the differential of measured temperature and set temperature. Whenever a control relay is OFF, detection of the loading connection can be done. Consequently, thermostat  101  can perform real time diagnostics of HVAC system  103 . If there is any problem with HVAC system  103  where a load connection is removed, thermostat  101  can detect loss of connection and report the occurrence to a networked device. 
     When in a control relay is in the up position (contact  1 ), the corresponding load is deactivated so that a test signal can be inserted into the load. A resulting signal is detected to determine whether the load is connected to thermostat  101 . However, when the control switch is in the down position (contact  2 ), the corresponding load is activated. For example, control relay  421  activates the fan of HVAC system  103  when in the down position. When control relays  401 - 407  are in down position (i.e., the HVAC loads are activated) thermostat  101  does not inject a test signal into the loads. 
     By turning on opto-coupler switch (OPT 1 )  427 , current flows into a load if the load is connected. (For example, switch  427  may correspond to Vishay Semiconductors 6N138 optocoupler.) For loads that are externally connected, feedback current is sensed by switches OPT 2 -OPT 7   428 - 434  because there is zero-crossing signal passing through opto-coupler switches  428 - 434 . (For example, switches  428 - 434  may correspond to a Hewlett Packard HCPL2730 optocoupler.) Processor  301  can determine the HVAC type from resulting signals  435 - 441  available at the outputs of switches  428 - 434 . With some embodiments, an output of switches  428 - 434  is a continuous open or close signal. By detecting the signal, processor  301  can determine whether the HVAC system is connected. 
     Processor  301  determines the HVAC type from the resulting signals  435 - 441 . When a corresponding load is connected, the corresponding resulting signal is pulled to ground (i.e., the resulting signal voltage is zero) because the corresponding opto-coupler switch conducts current through a resistor to ground. As will be further discussed, processor  301  determines the HVAC type from lookup table  600  by comparing the resulting signal to possible values of the resulting signal. 
     With embodiments, processor  401  determines the HVAC type by determining what loads are connected to thermostat  101 . For the example case, the following is an exemplary mapping of different loads to the HVAC type: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 W1, G: 
                 Standard Heat Only 
               
               
                   
                 W1, W2, G: 
                 Standard Heat 2 stage 
               
               
                   
                 Y1, G: 
                 Standard Cool Only 
               
               
                   
                 Y1, W1, G: 
                 Standard 1H/1C Non-Heat Pump 
               
               
                   
                 Y1, W1, W2, G: 
                 Standard 2H/1C Non-Heat Pump 
               
               
                   
                 Y1, O, B, G, E: 
                 1H/1C Heat Pump 
               
               
                   
                 Y1, W2, O, B, G, E: 
                 2H/1C Heat Pump 
               
               
                   
                   
               
            
           
         
       
     
     With an aspect of the invention, processor  401  can detect a HVAC system change by periodically injecting a test signal when the HVAC loads are deactivated (i.e., when control relays  401 - 407  are in the up position). Processor  401  can then send information to a controller (e.g., networked device  105 ). The controller can consequently perform actions based on the information. For example, if the HVAC system changes from gas furnace to heat pump operation, the networked system can determine to participate in an electricity energy conservation program. 
       FIG. 5  shows flow diagram  500  for determining the HVAC type in accordance with an embodiment of the invention. In step  501 , power is applied to thermostat  101 . In step  503 , all control relays  401 - 407  are turned off, and opto-coupler switch  427  is enabled so that a test signal can be injected into the HVAC loads. Processor  401  also sets the flag value to 0×FF. In step  505 , processor  401  determines whether the fan load (corresponding to load  414  as shown in  FIG. 4 ). (All of the exemplary valid HVAC types require that HVAC system  103  be configured with a fan.) If a fan is not detected, process  500  loops on step  505  until a fan is detected. With some embodiments, an indicator may be activated to indicate the occurrence of this situation. 
     In step  507 , processor  401  modifies the value of the flag based on the different loads that are connected to thermostat  101 . Each detected load results in a corresponding bit in the flag being changed to ‘0’. In step  509 , processor  401  utilizes look-up table  600  to determine the HVAC type based on the flag value. 
       FIG. 6  shows lookup table  600  for determining the HVAC type in accordance with an embodiment of the invention. Look-up table  600  maps HVAC types  601 - 607  to flag values 0×DE, 0×D6, 0×9F, 0×9E, 0×96, 0×89, and 0×81, respectively. (With the embodiment shown in  FIG. 6 , bit  7  of the flag is set to ‘1’.) If processor  401  determines that the flag value is not one of the above values, processor  401  may indicate to a user that the HVAC type is invalid. For example, if processor  401  detects only loads W 1 , O, and G (which is not a valid load configuration in the exemplary embodiment), the corresponding flag value is equal to 0×DA. 
     As can be appreciated by one skilled in the art, a computer system with an associated computer-readable medium containing instructions for controlling the computer system can be utilized to implement the exemplary embodiments that are disclosed herein. The computer system may include at least one computer such as a microprocessor, digital signal processor, and associated peripheral electronic circuitry. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.