Abstract:
Reversible draft controllers and exhaust systems incorporating reversible draft controllers are disclosed. One system for controlling draft in a chimney includes a sensor for determining condition data, an axial fan blade, an electronically commutated motor (ECM), and a controller. The ECM is configured to rotate the fan blade in a first direction to increase draft in the chimney and in a second, opposite direction to decrease draft. The controller has a processor and a program of instructions executable by the processor to perform steps for controlling draft in the chimney with the fan blade. The steps include: comparing condition data from the sensor to set point data to determine if an intervention is required; addressing insufficient draft by actuating the ECM to rotate the axial fan blade in the first direction; and addressing excessive draft by actuating the ECM to rotate the fan blade in the second direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Patent Application No. 61/485,474, filed May 12, 2011, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    For chimney systems to work effectively, maintaining certain pressures may be required. In various prior art chimney systems with significant vertical and lateral runs, a draft inducer is included for low-draft situations, and an over-draft damper is included for reducing draft once the chimney has been primed and excessive draft pressures are generated. A controller uses a first feedback loop—often a proportional-integral-derivative (or “PID”) loop—to operate the draft inducer, and uses a second feedback loop—again, often a PID loop—to operate the damper. If pressure in the chimney is excessively positive, the controller increases the speed of the draft inducer to offset the excessive positive pressure. However, if the chimney system becomes excessively negative, the controller switches PID loop control to operate the damper, which baffles flue gas to reduce the excessive negative pressure. 
         [0003]    Limitations may exist in such prior art systems. For example, the draft inducer, the damper, hardware for each PID loop, and software for each PID loop may introduce initial, operational, and maintenance costs to each system. Further, the components may collectively require a relatively large amount of space in the prior art systems. In various embodiments of the current invention, these and/or other limitations may be overcome or reduced. 
         [0004]    Reversible draft controllers and exhaust systems incorporating reversible draft controllers are provided herein. 
       SUMMARY 
       [0005]    Reversible draft controllers and exhaust systems incorporating reversible draft controllers are disclosed. In one embodiment, a system for controlling draft in a chimney includes a sensor for determining condition data relating to the draft in the chimney, an axial fan blade; an electronically commutated motor (ECM), and a controller. The ECM is configured to rotate the axial fan blade in a first direction to increase the draft in the chimney and to rotate the axial fan blade in a second direction (opposite to the first direction) to decrease the draft in the chimney. The controller has a processor and a program of instructions executable by the processor to perform method steps for controlling the draft in the chimney with the axial fan blade. The method steps include: (a) comparing condition data from the sensor to set point data to determine if an intervention is required; (b) addressing insufficient draft in the chimney by actuating the ECM to rotate the axial fan blade in the first direction; and (c) addressing excessive draft in the chimney by actuating the ECM to rotate the axial fan blade in the second direction. 
         [0006]    In another embodiment, a program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for regulating an amount of draft in a chimney, is disclosed. The method steps include: receiving condition data indicating an amount of the draft; accessing from a database stored data comprising set point data; determining if an intervention is needed based on a comparison of the condition data to the set point data; addressing insufficient draft; and addressing excess draft. Insufficient draft is addressed by each of: (a) causing an axial fan blade to rotate in a first direction, the axial fan blade previously rotating in a second direction opposite the first direction or being stationary; (b) causing the axial fan blade to rotate faster in the first direction; and (c) causing the axial fan blade to decrease speed of rotation in the second direction. Excess draft is addressed by each of: (d) causing the axial fan blade to rotate in the second direction, the axial fan blade previously rotating in the first direction or being stationary; (e) causing the axial fan blade to rotate faster in the second direction; and (f) causing the axial fan blade to decrease speed of rotation in the first direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows an exhaust system incorporating a reversible draft controller, according to one embodiment of the invention. 
           [0008]      FIG. 2  shows an exemplary set of steps performed by the reversible draft controller of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIGS. 1 and 2  illustrate a reversible draft controller  100  and an exhaust system  10  using the reversible draft controller  100 , according to one embodiment. Apart from the reversible draft controller  100 , the system  10  includes a user interface  200 , a sensor  300  monitoring draft in a chimney, and a draft inducer (or “fan”)  400 . Very notably, a separate dampener is not required. 
         [0010]    The draft inducer  400  includes an axial fan blade  402  and an electronically commutated motor (or “ECM”)  404 . The user interface  200  may include an input (e.g., keyboard, touchscreen, etc.) and an output (e.g., visual display, audible alarm, etc.), and in some embodiments the user interface  200  may be permanently in data communication with, and local to, the controller  100 . In other embodiments, the user interface  200  may be selectively in data communication with the controller  100 ; for example, the user interface  200  may be a laptop or tablet computer that may be selectively placed in data communication with the controller  100 . Moreover, the user interface  200  may be remotely in data communication with the controller  100 , such as through a network (e.g., the Internet, a telephone network, etc.). 
         [0011]    Focusing on the reversible draft controller  100 , the controller  100  includes a processor  110  in data communication with non-transitory computer memory  120  having programming  130  and a database  140 . As will be appreciated by those skilled in the art, the computer memory  120  may consist of any appropriate computer-storage media (e.g., RAM, ROM, EEPROM, flash memory, etc.) and the database  140  may be any electronic file or combination of electronic files in which data is stored for use by the processor  110 . 
         [0012]    The programming  130  causes the processor  110  to undertake various steps for controlling the fan  400  to both increase and decrease draft, such as shown in  FIG. 2 . Those skilled in the art will appreciate that various steps shown and described can occur in different orders, and that some steps may be omitted or combined. 
         [0013]    At step S 102  of  FIG. 2 , the processor  110  obtains condition data from the sensor  300  about draft in a chimney. The programming then proceeds to step S 104 , where the processor  110  obtains set point data (i.e., data regarding target draft in the chimney) from the memory  120  (e.g., from the database  140 ). At step S 106 , the processor  110  determines whether intervention is required by comparing the condition data from the sensor  300  (from step S 102 ) to the set point data from the memory  120  (from step S 104 ). The set point data may be a range of acceptable draft levels, or may include a particular set point with or without an acceptable margin. If the draft in the chimney is at the set point or within an acceptable margin around the set point, intervention is not required and the programming  130  directs the processor  110  back to step S 102 . If intervention is needed, the programming instead directs the processor  110  to step S 108 . 
         [0014]    At step S 108 , the processor  110  determines if the draft in the chimney is too low, using the set point data and the condition data. If so, the processor  110  continues to step S 110 ; if not, the processor  110  proceeds to step S 120 . 
         [0015]    At step S 108 , the processor  110  determines if the fan  400  is already activated in a first direction that increases draft in the chimney. This determination may be made by maintaining (e.g., in the memory  120 ) and querying a status of the fan  400 , and/or by analyzing data from the fan  400  (e.g., the ECM  404 ) or a sensor associated with the fan  400 . If the processor  110  determines at step S 110  that the fan  400  is already activated, the processor  110  may increase the speed of the fan  400  in the first direction to increase the draft at step S 112 . The amount of increase in fan speed may be incremental, or may be proportional to (or otherwise associated with) the amount of additional draft needed. It may be particularly desirable to use PID algorithms to calculate the amount of increase in fan speed. From step S 112 , the processor  110  is directed to return to step S 102 . 
         [0016]    If the processor  110  determined at step S 110  that the fan  400  was not already activated in the first direction, the processor  110  turns to step S 114  and determines if the fan  400  is already activated in a second direction that decreases draft in the chimney. As noted above, the determination of whether the fan  400  is activated may be made in various ways. For example, a status of the fan  400  may be maintained and queried, and/or data from the fan  400  (e.g., the ECM  404 ) or a sensor associated with the fan  400  may be analyzed. If the fan  400  is already activated in the second direction, the processor  110  (at step S 116 ) may decrease the speed of the fan  400  in the second direction to increase the amount of draft in the chimney. The amount of decrease in fan speed may be incremental, or may be proportional to (or otherwise associated with) the amount of additional draft needed. It may be particularly desirable to use PID algorithms to calculate the amount of decrease in fan speed. From step S 116 , the processor  110  is directed to return to step S 102 . 
         [0017]    If the processor  110  determined at step S 114  that the fan  400  is not already activated in the second (i.e., dampening) direction, the processor  110  may activate the fan  400  at step S 118  in the first (i.e., draft-inducing) direction. Similar to step S 110 , the speed of the fan  400  in the first direction may be incrementally adjusted (e.g., to a first setting) or proportionally adjusted at step S 118 . The programming  130  directs the processor  110  from step S 118  to step S 102 . 
         [0018]    Looking now at step S 120 , which occurs if the processor  110  determines that the draft in the chimney is not too low at step S 108 , the processor  110  determines if the draft in the chimney is too high. Because the processor  110  has already determined that intervention is required (at step S 106 ) and that the draft is not too low (at step S 108 ), it may be automatically determined at step S 120  that the draft in the chimney is too high. The processor  110  proceeds from step S 120  to step S 122 . 
         [0019]    At step S 122 , the processor  110  determines whether the fan  400  is already activated in the second (i.e., dampening) direction. Analysis at step S 122  generally corresponds to that at step S 114  discussed above. If the processor  110  determines at step S 122  that the fan  400  is already activated in the second direction, the processor  110  may increase the speed of the fan  400  in the second direction to decrease the draft at step S 124 . The amount of increase in fan speed may be incremental, or may be proportional to (or otherwise associated with) the amount of additional dampening needed. It may be particularly desirable to use PID algorithms to calculate the amount of increase in fan speed. From step S 124 , the processor  110  is directed to return to step S 102 . 
         [0020]    If the processor  110  determined at step S 122  that the fan  400  was not already activated in the second direction, the processor  110  turns to step S 126  and determines if the fan  400  is already activated in the first direction. As noted above, the determination of whether the fan  400  is activated may be made in various ways. If the fan  400  is already activated in the first direction, the processor  110  (at step S 128 ) may decrease the speed of the fan  400  in the first direction to decrease the amount of draft in the chimney. The amount of decrease in fan speed may be incremental, or may be proportional to (or otherwise associated with) the amount of additional dampening needed. It may be particularly desirable to use PID algorithms to calculate the amount of decrease in fan speed. From step S 128 , the processor  110  is directed to return to step S 102 . 
         [0021]    If the processor  110  determined at step S 126  that the fan  400  is not already activated in the first (i.e., draft-inducing) direction, the processor  110  may activate the fan  400  at step S 130  in the second (i.e., dampening) direction. Similar to step S 110 , the speed of the fan  400  in the second direction may be incrementally adjusted (e.g., to a first setting) or proportionally adjusted at step S 130 . The programming  130  directs the processor  110  from step S 130  to step S 102 . 
         [0022]    In some embodiments, steps S 114 , S 116 , S 126 , and S 128  (for example) may be omitted, such that the fan  400  is automatically rotated in the first direction when additional draft is needed in the chimney, and automatically rotated in the second direction when additional dampening is needed. Omission may be complete (such that steps do not appear in the programming  130 ), or may be triggered upon various events. For example, if the processor  110  determines at step S 108  that the draft is extremely too low, steps S 114  and S 116  may be temporarily skipped. And in any event, steps S 102  and S 104 , steps S 108  and S 120 , steps S 110  and S 114 , steps S 122  and S 126  may be respectively interchanged (e.g., such that step S 104  occurs before step S 102 , etc.). 
         [0023]    Additionally, the programming  130  may include instructions causing the ECM  404  and/or sensors associated with the fan  400  to be periodically or continuously monitored by the processor  110  to verify that the fan  400  is operating correctly, and the processor  110  may send alerts (e.g., to the user interface  200 ) if the fan  400  is operating outside of set parameters. 
         [0024]    Those skilled in the art will appreciate that the controllers and systems set forth herein may be used in exhaust systems with various degrees of precision and tolerance. As an example, chimney pressure may be maintained in a bi-directional manner +/−0.25″ WC. 
         [0025]    Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present invention. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. The specific configurations and contours set forth in the accompanying drawings are illustrative and not limiting.