Abstract:
Systems and methods for control of a heating appliance blower that provide improved the transfer of heat generated in the heating appliance. By automatically timing when the heating appliance blower turns ON and OFF, the heat generated by the heating appliance can be more effectively transferred away from the heating appliance as desired by a user, for example, to improve heating efficiency of the heating appliance.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention generally relates to airflow control in heating appliances, and more specifically relates to systems and methods for improving heating efficiencies of decorative heating appliances by controlling airflow in the heating appliance.  
         [0003]     2. Related Art  
         [0004]     The efficiency of a heating appliance is determined based in part on the amount of heat recovered given the amount of energy consumed. Heating appliances consume energy primarily in the generation of heat using, for example, combustion of fuel (e.g., LP, natural gas, or wood/wood pellets) or the conversion of electricity into heat. Another source of power consumption with a heating appliance relates to the way into which the generated heat is delivered for its intended purpose. Operating a blower in conjunction with a heating appliance is a common way to transfer the generated heat to a desired location (e.g., from the heating appliance into a living space). Blowers require power to operate, thus contributing to the overall efficiency of heating appliance.  
         [0005]     The heat generated by heating appliances can be transferred in many different ways that also affect the efficiency of the appliance. Some of the generated heat escapes the appliance through the exhaust flue of the heating appliance in the case of a combustion heating appliance. Other heat is transferred into the building structure surrounding the heating appliance, into a living space in which the heating appliance is exposed, or into plenum spaces within the heating appliance. The amount of heat transferred from the heating appliance for useful purposes depends on several variables including, for example, the structure, materials, and location of heating appliance. Some types of heating appliances such as gas furnaces are not intended to provide an aesthetic function and can be designed with maximum heating efficiency as a primary objective. Furnaces typically include a relatively small combustion chamber having outer surfaces exposed to large volumes of airflow and are made of relatively thin metal materials. The combustion chamber structure as a whole retains little heat and is designed to quickly transfer all heat generated by the flame into the airflow engaging the outside surface of the combustion chamber.  
         [0006]     Other types of heating appliances, in particular decorative heating appliances such as fireplaces, stove, and fireplace inserts, include relatively large combustion chambers configured to display an actual or simulated decorative flame. The emphasis of many decorative heating appliances is aesthetics rather than efficiency. The structure and materials of decorative heating appliances in addition to their typical mounting within or adjacent to a wall structure of a building, can results in much loss of otherwise useful heat in the heating appliance itself, out of the appliance exhaust system, or into the wall structure. Although significant advances have been made to capture this otherwise lost heat, further improvements are possible.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention relates to systems and method for controlling air flow and the transfer of heat in decorative heating appliances such as fireplaces, stoves, and fireplace inserts. The disclosed embodiments illustrate example systems and methods relate to control of a blower of the heating appliance, wherein blower control results in improved control and transfer of heat generated in the heating appliance. By automatically timing when the heating appliance blower turns ON and OFF, the heat generated by the heating appliance can be more effectively transferred away from the heating appliance as desired by a user, for example, to improve heating efficiency of the heating appliance.  
         [0008]     One aspect of the invention relates to a blower system for use with a heating appliance, wherein the heating appliance including a heat generating unit. The system includes a blower and a blower time control module. The blower timing control module monitors an ON/OFF state of the heat generating unit and controls an ON/OFF state of the blower in response to the monitored ON/OFF state of the heat generating unit. The blower timing control module turns the blower OFF after a first predetermined time period from when an OFF state of the heat generating device is detected, and turns the blower ON after a second predetermined time period from when an ON state of the heat generating unit is detected. The heat generating unit can include a gas valve, and the blower timing system is configured to monitor ON/OFF signals received by the gas valve as part of monitoring an ON/OFF state of the heating appliance.  
         [0009]     Another aspect of the invention relates to a method of controlling air flow in a heating appliance, wherein the heating appliance includes a combustion chamber, a blower, and a heat generating device. The method includes turning ON the heat generating device, turning ON the blower, turning OFF the heat generating device, and turning OFF the blower a first predetermined time period after the heat generating device is turned OFF. The method can also include turning ON the blower after a second predetermined time period after the heat generating device is turned ON.  
         [0010]     A further aspect of the invention relates to a fireplace that includes a heat generating device, a combustion chamber enclosure defining a combustion chamber wherein heat is generated with the heat generating device, a blower configured to create an air flow in the fireplace, and a blower control module. The blower control module is configured to monitor an ON/OFF state of the heat generating device and automatically control an ON/OFF state of the blower in response to the monitored ON/OFF state of the heat generating device. The blower control module turns OFF the blower after a first predetermined time period from when the heat generating device is turned OFF, and can turn ON the blower after a second predetermined time period from when the heat generating device is turned ON. The control module can also monitor the heat generating device during the first and second predetermined time periods to confirm the ON/OFF state of the heat generating device.  
         [0011]     The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description that follow more particularly exemplify certain embodiments of the invention. While certain embodiments will be illustrated and describe embodiments of the invention, the invention is not limited to use in such embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0013]      FIG. 1  is a front view of a heating appliance including an example blower system according to principles of the present invention;  
         [0014]      FIG. 2  is a cross-section view of the heating appliance shown in  FIG. 1  taken along cross-section indicators  2 - 2 ;  
         [0015]      FIG. 3  is a front view another example blower control module according to principles of the present invention;  
         [0016]      FIG. 4  is a schematic diagram representing an example blower control module coupled to a valve, power source, and wall switch for a heating appliance;  
         [0017]      FIG. 5  is a schematic diagram representing another example blower control module coupled to a valve, power source, and ignition system for a heating appliance;  
         [0018]      FIG. 6  is a schematic circuit diagram for the circuit components of the blower control module shown in  FIG. 3 ;  
         [0019]      FIG. 7  is a side cross-sectional view of another heating appliance that includes another example blower system according to principles of the present invention, the heating appliance including multiple blowers;  
         [0020]      FIG. 8  is a schematic flow diagram illustrating steps of an example method of controlling a heating appliance blower; and  
         [0021]      FIG. 9  is a schematic flow diagram illustrating steps of another example method of controlling a heating appliance blower. 
     
    
       [0022]     While the invention is amenable to various modifications and alternate forms, specifics thereof have been shown by way of example and the drawings, and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     The present invention generally relates systems and methods for controlling airflow and heat transfer in a decorative heating appliance. Decorative heating appliances are different from other heat generating appliances in that they include structure that acts as a heat sink (i.e., retains heat during and after shut down of the heat generating features of the heating appliance). Typically, much of this heat is lost without a productive heating purpose. In some cases, users leave a blower of the heating appliance “ON” to capture this heat retained in the structure. Blowers sometimes remain “ON” for extended periods of time well beyond optimum times for efficient transfer of the heat retained in the structure. Efficient heat transfer in this scenario is defined as the ratio between power consumption of the blower and the amount of heat removed from the heating appliance structure for useful purpose.  
         [0024]     One aspect of the invention relates to a system that automatically controls the ON/OFF function of a decorative heating appliance blower relative to the ON/OFF state of the heat generating features of the heating appliance. This automated control can result in optimized operation of the blower to maximize efficient heat transfer from the heating appliance. For example, the system delays turning ON the blower a predetermined time after start up of heat generation in the heating appliance. This delay allows the heating appliance structure to become heated before attempting to transfer heat with an air flow from the blower. In another example, the system delays turning OFF the blower a predetermined time after shut down of heat generating in the heating appliance. This type of delay allows the blower to continue transferring heating from the heating appliance structure that may not otherwise be effectively used, while maintaining efficient power consumption by the blower.  
         [0025]     Some example decorative heating appliances with which the disclosed systems and methods could be used include gas, electric, or wood burning style fireplaces, stoves and fireplace inserts. Other example heating appliances include universal vent, horizontal/vertical vent, B-vent, and dual direct vented fireplaces, stoves and fireplace inserts, as well as multisided heating appliances having two or three glass panels as side panels.  
         [0026]     Referring now to  FIGS. 1 and 2 , an example fireplace  10  is shown including a blower timing system. The fireplace  10  includes an outer enclosure  12 , a combustion chamber enclosure  14 , a valve  16 , an ignition system  18 , a blower  20  and a blower control module  22 . Fireplace  10  also includes a plenum  24 , a burner  26 , a vent assembly  28 , and a power source  29 .  
         [0027]     The combustion chamber enclosure  14  is positioned within the outer enclosure  12  and is sized smaller than the outer enclosure  12  thereby defining the plenum  24 . The combustion chamber enclosure  14  includes side panels  30 ,  32 , top and bottom panels  34 ,  36 , front and rear panels  38 ,  40  and that together define a combustion chamber  42 . Portions of the ignition system  18  and burner  26  are positioned within the combustion chamber. The valve  16 , ignition system  18 , blower  20 , blower control module  22  and power source  29  are positioned within the plenum space  24 . The ignition system  18  is configured to generate a pilot flame that is used to ignite a main flame of the burner  26 . Operation of the ignition system  18  is coordinated with opening and closing of features of the valves  16  to provide gas flow to the ignition system and to the burner for ignition of the pilot flame and the main burner flame. Typically, the valve  16  receives electronic ON/OFF signals for operation of valve features that control fuel flow through the valve  16 .  
         [0028]     The blower control module  22  monitors receipt of the ON/OFF control signals at the valve  16 . When the blower control module  22  identifies receipt of an ON control signal at the valve  16 , the blower control module can initiate a sequence of controls related to ON/OFF control of the blower  20 . Likewise, when the blower control module  22  identifies an OFF signal at the valve  16 , the blower control module can initiate a further sequence of ON/OFF controls for the blower  20 .  
         [0029]     In other embodiments, one or more sensors may be used to detect the actual presence of a main burner flame at the burner or the presence of a pilot flame of the ignition system to determine the ON/OFF state of the heat generating features of the heating appliance. An example monitoring and control system that describes the use of flame sensors to determine the state of an ignition system or a main burner is described in U.S. patent application Ser. No. 11/238,640, filed on Sep. 28, 2005, and titled GAS FIREPLACE MONITORING AND CONTROL SYSTEM, which application is incorporated herein by reference.  
         [0030]     In yet further embodiments, the one or more devices (e.g., thermocouples, thermistors, thermopiles, or thermometers) may be used to detect a temperature within the combustion chamber or other features of the fireplace. When detected temperature exceeds or drops below a predetermined value, the blower ON/Off control sequence(s) is initiated. In one example, a thermistor or thermopile may be positioned inside the combustion chamber, embedded in a panel of the combustion chamber enclosure, within an exhaust duct of the fireplace, or in the plenum defined between the combustion chamber enclosure and the outer enclosure of the fireplace. A blower ON control sequence is initiated when the temperature reaches a specific value such as, for example, about 200° F. to about 400° F. A blower OFF control sequence is initiated when the temperature drops below, for example, about 200° F. to about 300° F. The temperature measure device may be used to measure the ambient temperature of gases in, around, or adjacent to the fireplace, or may be used to measure the physical features of the fireplace.  
         [0031]     The temperature measuring device may generate an electronic signal representative of a predefined temperature that is used to activate the blower timing sequence(s). In some embodiments, different electronic signals representative of different temperatures can be generated by the temperature measuring device. The different signals can be used to activate different types of blower sequences or different blower conditions. For example, the blower speed can be increased or decreased in response to signals from the temperature measuring device that indicate incremental increases or decreases in the measured temperature. In another example, a signal indicating a threshold temperature has been met can initiate a blower sequence in which the blower speed increases automatically at predefined time intervals (e.g., every 2 minutes increases blower speed by 10 rpm) over a predefined period (e.g., 30 minutes) or for a certain number of time intervals (e.g., 10 time intervals). A similar scenario is possible for gradually or intermittently decreasing the blower speed, for example, when the temperature signal indicates the temperature has dropped below a threshold temperature.  
         [0032]     In another embodiment, the blower operation can be controlled in response to operation of other features of the fireplace besides the ignition assembly and burner of the fireplace. For example, blower operation can be controlled in response to ON/OFF control of backlighting, an ember bed, a simulated flame display, or an electric heat generating unit associated with the fireplace.  
         [0033]     In another embodiment, the blower timing sequence(s) may be initiated through ON/OFF activation of the fireplace using a double pole/double throw switch. Such a switch provides starting of the blower timing ON sequence when the fireplace burner ignition sequence is activated by a user turning the switch ON. The switch also provides starting of the blower timing OFF sequence when the fireplace burner ignition sequence is deactivated by the user turning the switch OFF.  
         [0034]     Referring now to  FIG. 3 , an example blower control module  122  is shown including a housing  180 , a control knob  182 , a test button  184 , a label  185 , power wires  186 , and control wires  188 .  FIGS. 4 and 5  illustrate example control modules  222  and  322 , respectively, which are coupled to a power source  229 ,  329  and valves  216 ,  316 , respectively.  FIG. 4  further illustrates coupling of the valve  216  to a wall switch or control panel  256 .  FIG. 5  illustrates the valve  316  coupled to an ignition system  318 . The control modules  222 ,  322  monitor signals received from the wall panel  256  or ignition system  318 , respectively, to determine the ON/OFF control signals being sent to the valve for ON/OFF control of the valve.  
         [0035]      FIG. 6  illustrates a circuit diagram for an example control module such as the blower control module  22 ,  122 ,  222 ,  322  described above. The circuit components illustrated in  FIG. 6  include A/D and D/A converters, power regulators, signal noise filters and the like to help monitor and interpret valve ON/OFF signals and provide control signals to the blower.  
         [0036]     Referring now to  FIG. 7 , another example fireplace  100  is shown including an outer enclosure  112 , a combustion chamber enclosure  114 , a valve  116 , ignition system  118 , first and second blowers  120 ,  121 , and a blower control module  122 . The fireplace  100  also includes first, second and third plenums  123 ,  124 ,  125 , a burner  126 , and first and second vent assemblies  128 ,  129  having ducts  160 ,  161 . The combustion chamber enclosure includes side panel  130 , top and bottom panels  134 ,  136 , front and rear panels  138 ,  140  that define a combustion chamber  142 . An intermediate panel  144  separates the plenum spaces  123 ,  125 . The fireplace  100  illustrates that a blower control module  122  can be used to control multiple blowers and ventilation systems within a fireplace. Fireplace  100  includes a first blower  120  that provides ventilation through the plenum  125  and out of the duct  160 . A second blower system including a blower  119  provides ventilation through the plenum  123  and out of the duct  161 . Still further blowers and blower assemblies may be provided, all of which may be controlled by the blower control module  122 .  
         [0037]     In one embodiment using the fireplace  100 , the blower control module controls the ON/OFF function of the blowers  119 ,  120  using different delay time periods. For example, the blower  119  can be turned ON after a delay of 5 minutes from when the main burner is ignited and the blower  120  is turned ON after a delay of 10 minutes from when the main burner is ignited. The blowers  119  may both be turned OFF at the say delay time of 10 minutes from when the main burner is turned OFF.  
         [0000]     Example Blower Control System  
         [0038]     In one example blower control system, a blower control module monitors a condition of a gas burner of a gas fireplace. In response to the ON/OFF status of the burner, the blower control module controls an air circulation fan or blower at a predefined speed and at specified delay times relative to the burner state. The system operates independent of the ignition controls. The system also uses an A/D sensor input to detect the ON/OFF state of the burner. The A/D sensor detects the presence of a control voltage to a main burner control valve that supplies a flow of gas to the main burner.  
         [0039]     The A/D circuit works as a high impedance voltmeter that measures the main burner valve control voltage without adversely affecting the valve control voltage. The range and sensitivity of this voltmeter input is such that it can read the control voltage of both millivolt controls from an AC power source and low voltage dc controls from a battery backup power source. Random burst and spurious noise pulses can be falsely detected as a valve ON operation. The ignition spark noise of intermittent pilot ignition (IPI) systems could be one source of burst noise. The effect of burst noise is minimized by sampling the valve control voltage at consecutive fixed intervals. The sampling interval is of sufficient length to exclude burst noise. The burst noise would typically need to be present at each consecutive sampling window.  
         [0040]     Low frequency noise could affect the validity of a detected valve operation. A light bulb on a dimmer circuit could be one source of low frequency noise. This noise is minimized by utilizing the averaging of multiple samples during the sample window. The sampling rate is sufficiently fast to exclude low frequency noise. Low level “white noise” could also affect the detected status of valve operation, especially at the millivolt levels of power. This type of noise is ever present at some amplitude level. To minimize the effects of such white noise, the detection decision level contains hysteresis. The ON detect level is at a predefined minimum above zero volts. This effectively ignores the low noise level at both ON and OFF signals. The use of the multiple samples over multiple intervals and requiring consecutive results is a form of “fuzzy logic” that lends integrity to the burner ON/OFF decision.  
         [0041]     A. Power ON Reset (POR) Control Function  
         [0042]     At power ON reset, the fan control microcontroller (PIC) initializes by performing self-calibration and setting of internal counters and variables. During a first predetermined time interval (e.g., 6 minutes) the PIC monitors the “manual test button” (TEST) for operation. If TEST is depressed (e.g., test button  184  as shown in  FIG. 3 ), the PIC will check the ON/OFF status of the “burner valve” (valve).  
         [0043]     B. TEST Control Function  
         [0044]     When TEST is depressed, the fan will come on. This provides the installer an instant opportunity to verify operation and adjust the manual fan speed control for optimum performance. If the burner is OFF, releasing the test button will turn OFF the fan. If the burner is ON, releasing the test button will maintain the fan ON for another predetermined time (e.g., 1 minute). After the expiration of the first predetermined time (e.g. 6 minutes), pressing TEST will turn ON the fan immediately. Releasing TEST will turn OFF the fan immediately. The PIC will not go into the test sequence again and normal operation occurs.  
         [0045]     C. VALVE Monitoring Function  
         [0046]     The PIC determines the status of the valve at regular intervals (e.g., every minute). This ensures that the valve detection circuit (A/D) is immune to power line noise and spurious emissions of pilot ignition noise within the heating appliance. This immunity of the A/D is further enhanced by the averaging of samples within the sample period. A false ON detect would require multiple signal errors in each of the consecutive sample periods, which are spaced at, for example, 1 minute increments. The VALVE status is determined by measuring the voltage applied to the main burner valve solenoid. This system works with either an intermittent pilot ignition (IPI) or a millivolt standing pilot system. The burner ON detect circuit works independent of the fireplace burner ignition and safety controls. The detected status requires the measured A/D valve value to be above a preset minimum detected voltage to be considered as an ON signal and below that limit to be considered an OFF signal. Thus, the minimum detected voltage level is set above zero in order to provide enhanced noise immunity.  
         [0047]     D. NORMAL Operation Function  
         [0048]     An internal counter provides a signal at regular intervals (e.g., 1 minute). After each of these intervals (e.g., once each minute), PIC determines the status of the valve. The PIC updates the ON/OFF state of the fan based on the valve and timer values. An ON_TIMER requires that the valve be detected as ON for each interval of a predetermined time period (e.g., 7 consecutive minutes). The fan is then turned ON at a previously selected speed. An OFF_TIMER requires that the valve be detected as an OFF for each interval of a predetermined time period (e.g., 12 consecutive minutes). The fan is then turned OFF. For normal operations the PIC is in a continuous loop checking the state of the valve. On the occasion of power interruptions, brownouts, or ESD, the PIC performs a POR.  
         [0049]     Referring now to  FIG. 8 , the steps of an example method of using a blower timing control system in a heating appliance are described. The method includes a step  300  of turning ON the heat generating device of the heating appliance. A step  302  includes turning ON the blower a first predetermined time period after the heat generating device is turned ON. Step  304  includes turning OFF the heat generating device, and a step  306  includes turning OFF the blower a second predetermine time period after the heat generating device is turned OFF.  
         [0050]     Referring to  FIG. 9 , another example method of using a blower timing control system for a heating appliance is shown. The method includes a step  400  of sending a control signal to the valve to open the valve. Step  402  includes monitoring the valve to determine if an open control signal has been received at the valve. If the signal has not been received, a step  404  includes continued monitoring of the valve. If an open signal has been received, a step  406  includes waiting a first predetermined time period before turning ON the blower in a step  408 . In a step  410 , a control signal is sent to the valve to close the valve, and a step  412  includes monitoring the valve to determine if a closed control signal has been received at the valve. If the closed control signal has not been received, a step  414  includes continued blower operation. If the closed control signal has been received, a step  416  includes waiting a second predetermined time period. In a step  418 , the system continues to monitor the valve to determine if an open control signal has been received at the valve. If an open signal has been received, the system resets to step  410  and  412 . If the open control signal is not received during the second predetermined time period, a step  420  includes turning OFF the blower.  
         [0051]     The present invention should not be considered limited to the particular examples or materials described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the instant specification.