Abstract:
A water heater includes a water tank adapted to contain water; a flue extending through the water tank and having a first end communicating with the water heater&#39;s combustion chamber for the flow of products of combustion through the tank; a damper communicating with the flue; and an apparatus for creating a flow of air proximate the second end of the flue to resist the flow of warm air out of the second end of the flue due to standby convection.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 09/920,907 filed Aug. 2, 2001, the entire content of which is hereby incorporated by reference. 
     
    
     
       BACKGROUND  
         [0002]    The invention relates to a damper arrangement in a water heater. It is known to use a damper in a water heater flue. Known dampers use a physical obstruction to close the flue during standby. One example of a physical obstruction type damper is disclosed in U.S. Pat. No. 4,953,510.  
         SUMMARY  
         [0003]    The invention relates to a damper arrangement that uses an airflow apparatus to substantially reduce standby heat loss due to natural convection cycles in a water heater flue.  
           [0004]    The invention includes a water heater having a water tank adapted to contain water, a combustion chamber beneath the water tank, a burner within the combustion chamber and operable to create products of combustion, and a flue extending substantially vertically through the water tank. The flue communicates with the combustion chamber to conduct the products of combustion from the combustion chamber and to transfer heat to water stored within the water tank. The water heater also includes an airflow apparatus capable of creating airflow in the absence of any opposition to the airflow. The airflow apparatus communicates with the flue and resists standby convection flow of flue gases out of the flue when the burner is not operating.  
           [0005]    In one construction, the airflow apparatus is automatically adjustable to vary the magnitude of the airflow to more effectively counteract the standby convection flow of flue gases out of the water heater when the burner is not operating.  
           [0006]    In another construction, the airflow apparatus is operable to create a downward airflow in communication with the flue when the burner is not operating to counteract standby convection flow of flue gases and is also operable to create an upward airflow in communication with the flue when the burner is operating to assist the exhaust of the products of combustion from the flue.  
           [0007]    In a further aspect, the airflow apparatus creates airflow to counteract the standby convection flow of flue gases when the burner is not operating and an additional airflow apparatus mixes air with the products of combustion from the combustion chamber prior to entering a catalytic converter to improve the effectiveness of the catalytic converter when the burner is operating, and preferably at startup of the water heater.  
           [0008]    In yet another construction of the invention, the airflow apparatus is an ionic airflow device connected to an over current device that disconnects power to the ionic airflow device in the event of an arcover.  
           [0009]    In a further construction, the airflow apparatus is an ionic airflow device electrically connected to the same high-voltage power supply that powers an ignitor of a direct ignition system of the water heater.  
           [0010]    In another embodiment of the invention, an airflow apparatus creates an airflow in communication with the flue when the burner is operating to create a backpressure in the flue that increases the residence time of the products of combustion within the flue.  
           [0011]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a side elevation view of a water heater according to a first embodiment of the present invention.  
         [0013]    [0013]FIG. 2 is a perspective view of a first construction of an airflow apparatus of the water heater shown in FIG. 1.  
         [0014]    [0014]FIG. 3 is a cross-sectional view taken along line  3 - 3  in FIG. 2.  
         [0015]    [0015]FIG. 4 is a perspective view of a second construction of the airflow apparatus.  
         [0016]    [0016]FIG. 5 is a cross-sectional view taken along line  5 - 5  in FIG. 4.  
         [0017]    [0017]FIG. 6 is a cross-sectional view of a third construction of the airflow apparatus.  
         [0018]    [0018]FIG. 7 is a cross-sectional view taken along line  7 - 7  in FIG. 6.  
         [0019]    [0019]FIG. 8 is a partial section view of a fourth construction of the airflow apparatus.  
         [0020]    [0020]FIG. 9 is a perspective view of the electrodes of the airflow apparatus shown in FIG. 8.  
         [0021]    [0021]FIG. 10 is a perspective view of a fifth construction of the airflow apparatus.  
         [0022]    [0022]FIG. 11 is a partial schematic view of the water heater and the airflow apparatus shown in FIG. 10. 
     
    
       [0023]    Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.  
       DETAILED DESCRIPTION  
       [0024]    [0024]FIG. 1 illustrates a water heater  10  embodying the invention. The water heater  10  comprises a tank  14  for containing water to be heated, an outer jacket  18  surrounding the water tank  14 , insulation  20  between the tank  14  and the jacket  18 , a combustion chamber  22  below the tank  14 , a flue  26  extending substantially vertically through the water tank  14 , and a baffle  28  extending through the flue  26 . The water heater  10  can also include an optional catalytic converter  112  in communication with the flue  26 . The flue  26  includes a first or lower end  30 , and a second or upper end  38 . The water heater  10  also includes a thermostat  40  extending into the water tank  14  and a burner  42  in the combustion chamber  22 . Fuel is supplied to the burner  42  through a fuel line  43 , a gas valve  44 , and a gas manifold tube  45 . The fuel line  43  also provides fuel to a pilot burner  46  next to the burner  42 . The pilot burner  46  ignites fuel flowing out of the burner  42  when the burner  42  is activated. The pilot burner  46  may be continuous such as a small flame or intermittent such as an electric spark ignitor (not shown).  
         [0025]    In operation, the burner  42  burns the fuel supplied by the fuel line  43 , along with air drawn into the combustion chamber  22  through one or more air inlets  47 . The burner  42  creates products of combustion that rise through the flue  26  and heat the water by conduction through the flue walls. The flow of products of combustion is driven by natural convection, but may alternatively be driven by a blower unit (not shown) communicating with the flue  26 . The above-described water heater  10  is well known in the art.  
         [0026]    During standby of the water heater  10  (i.e., when the burner  42  is not operating), the air and other gases in the flue  26  (collectively, “flue gases”) are heated by the water in the tank  14  and by the flame of the pilot burner  46 . This creates natural convection currents and imparts a buoyancy to the flue gases that causes the flue gases to flow toward the upper end  38  of the flue  26 . As used herein, “standby convection” means the natural convection within the flue  26  that occurs when the burner  42  is not operating, and that is caused by the water in the tank  14  and/or the flame of the pilot burner  46  warming the flue gases by heat transfer through the flue walls. Unrestricted flow of warm flue gases out of the flue  26  due to standby convection will result in standby heat loss from the water heater  10 .  
         [0027]    As seen in FIGS.  1 - 3 , to help reduce or eliminate standby convection heat losses, the water heater  10  includes a novel damper assembly  48 . The damper assembly  48  includes a hood  49 , a housing  50 , and an airflow apparatus  54 . The hood  49  permits ambient air to mix with the products of combustion as the products of combustion pass through the damper assembly  48 , and before the products of combustion are vented to the atmosphere.  
         [0028]    As used herein, the term “airflow apparatus” means an apparatus capable of creating airflow in the absence of any opposition to the airflow. The apparatus  54  includes a tubeaxial fan  56  having rotatable blades that create a flow of air parallel to an axis of rotation  58  of the fan blades. The axis of rotation  58  is disposed horizontally, and the fan  56  is exposed to the ambient air surrounding the water heater  10  such that air is drawn into the damper assembly  48  substantially along the axis of rotation  58 . The housing  50  defines an annular cavity surrounding the upper end  38  of the flue  26 . Circumferential slots or apertures  66  are provided in the annular cavity, and the slots  66  are preferably angled down to direct airflow out of the annular cavity into the upper end  38  of the flue  26 . With some modifications to the housing  50 , the tubeaxial fan  56  may be replaced with a radial fan.  
         [0029]    The fan  56  is preferably turned on during water heater standby, when the burner  42  is not operating. The fan  56  creates a downward pressure or back pressure zone over or within the upper end  38  of the flue  26 . The fan  56  and the standby convection currents create countervailing downward and upward pressures, respectively, within the flue  26 . In other words, in the absence of the fan  56 , standby convection would cause the flue gases to move vertically upward out of the upper end  38  of the flue  26 . In the absence of standby convection, the fan  56  would push air downwardly through the flue  26  and out of the air inlets  47 .  
         [0030]    A gate  68  is pivotably mounted in the housing  50  and is adjustable to restrict and open the air flow path from the fan  56  into the annular cavity of the housing  50 . The more open the air flow path, the higher the downward pressure exerted by the fan  56  will be. Therefore, for a single-speed fan  56 , the gate  68  setting determines the amount of downward pressure. Alternatively, the fan  56  may be a variable speed fan, in which case the downward pressure may be adjusted by adjusting the speed of the fan  56 , and the gate  68  would not be necessary.  
         [0031]    In one construction, the airflow apparatus  54  is automatically adjustable to vary the amount of the downward pressure, or airflow, to more effectively counteract the standby convection heat loss of the water heater  10 . In order to eliminate or control the standby convection currents, the opposing airflow generated by the airflow apparatus  54  must precisely balance the standby convection currents. If the airflow and the standby convection currents are not balanced, one will overpower the other resulting in heat loss from the flue  26 . For example, if the airflow apparatus  54  is providing a greater airflow than the standby convection currents, the airflow apparatus  54  will reverse the direction of the standby convection currents causing heat to be lost out the bottom of the combustion chamber  22 . Alternatively, if the airflow apparatus  54  provides a lesser airflow than the standby convection currents, the standby convection currents will bypass the airflow apparatus  54  resulting in heat loss out of the flue  26 . Therefore, to substantially eliminate heat loss for a given magnitude of standby convection currents, the magnitude of the airflow generated by the airflow apparatus  54  can be adjusted to precisely balance the standby convection currents.  
         [0032]    The magnitude of the standby convection currents is dependent upon the temperature of the water stored within the tank  14 . However, this temperature is not constant as the temperature of the water stored in the tank  14  varies during the operation of the water heater  10 . For example, the magnitude of the standby convection currents increases when the water stored in the tank  14  is elevated and decreases when the water stored in the tank  14  is lowered. Because the magnitude of the standby convection currents is variable with the temperature of the stored water, the adjustability of the airflow apparatus  54  is preferred in order to adjust the magnitude of the generated airflow to respond to the changes in the magnitude of the standby convection currents to create a substantially stagnant state within the flue  26 .  
         [0033]    The water heater  10  also comprises a control system for the fan  56 . With reference to FIG. 1, the control system includes a controller  69  operatively interconnected between the fan  56  and a pressure switch  70  mounted on the gas valve  44 . When there is a call for heat, fuel flows through the gas valve  44  and to the burner  42 . The pressure in the gas valve  44  opens the pressure switch  70 , an electrical signal is relayed to the controller  69 , and the controller  69  turns the fan  56  off. Alternatively, a temperature switch  74  (illustrated in broken lines in FIG. 1) may be operatively interconnected with the controller  69  and mounted at the upper end  38  of the flue  26 . When the burner  42  fires, the flue gas temperature rises, thereby opening the temperature switch  74 . An electrical signal is relayed to the controller  69 , and the controller turns off the fan  56 . Alternatively, if there is a sufficiently strong flow of products of combustion through the flue  26  during operation of the burner  42 , and the fan  56  would not unduly restrict the flow of products of combustion out of the flue  26 , the fan  56  may be operated at all times.  
         [0034]    In another embodiment of the invention, the airflow apparatus  54  is operated during operation of the burner  42  to create a downdraft and back pressure that can be used to assist or replace the baffle  28 . The baffle  28  increases pressure drop and residence time of the products of combustion in the flue  26  where heat is transferred to the water stored in the tank  14 . The airflow apparatus  54  can be operated during operation of the burner  42  to create a downdraft and increase the residence time of the products of combustion within the flue, thereby potentially allowing removal of the baffle  28 . Replacement of the baffle  28  is preferred because the baffle  28  is a fixed entity that cannot be varied during burner operation, whereas, as discussed above, the airflow apparatus  54  is capable of being adjusted to vary the baffle effect during different phases of burner operation to thereby optimize the burner operation.  
         [0035]    In another aspect of the invention, an additional airflow apparatus  146  (FIG. 1) can be operated during operation of the burner  42  to mix air with the products of combustion from the combustion chamber prior to the mixture entering the catalytic converter  112 . The addition of air to the products of combustion improves the effectiveness of the catalytic converter  112  during the operation of the burner  42  at startup.  
         [0036]    Combustion products produce substances that are harmful to the environment. A catalytic converter  112  is an optional way to reduce the amount of harmful substances released to the environment. The catalytic converter  112  contains platinum, palladium, or some other element that speeds the conversion of unburned hydrocarbons and carbon monoxide into water and carbon dioxide. A catalytic converter  112  does not work effectively until it reaches a certain elevated temperature. In the absence of the elevated temperatures, the infusion of air by the airflow apparatus  146  improves the performance of the catalytic converter  112 .  
         [0037]    In addition to controlling the activation and deactivation of the airflow apparatus  54 , the control system also automatically adjusts the magnitude of the airflow generated by the airflow apparatus  54 . As discussed above, the magnitude of the standby convection currents is dependent upon the temperature of the water stored within the tank  14 . Therefore, to accurately balance the standby convection currents, the magnitude of the airflow can be controlled based upon the temperature of the stored water. In one construction, the controller  69  adjusts the operation of the airflow apparatus  54  based upon the temperature of the stored water measured by a sensor such as a thermistor  114  (illustrated in broken lines in FIG. 1).  
         [0038]    In other constructions, the magnitude of the airflow can also be controlled based on the temperature or velocity of the standby convention currents within the flue  26  because the temperature and rate of flow of the flue gases in the flue  26  during standby is directly proportional to the temperature of the flue wall which is in turn directly proportional to the temperature of the water in the tank  14 . Due to this proportional relationship, the controller  69  can adjust the operation of the airflow apparatus  54  based on the temperature of the gases within the flue  26  measured by a sensor, such as temperature switch  74  or a thermistor. Alternatively, the controller  69  can adjust the operation of the airflow apparatus  54  based on the velocity of the standby convection currents within the flue measured by a sensor such as an anemometer  116  (shown in broken lines in FIG. 1).  
         [0039]    In yet other constructions, the magnitude of the airflow can be controlled based on the setting of the gas valve  44 . The gas valve  44  is adjusted to control the desired set temperature of the water within the tank  14 . In light of this relationship, the controller  69  can adjust the operation of the airflow apparatus  54  based on the setting of the gas valve  44  measured by a sensor  118  (shown in broken lines in FIG. 1) such as a rotary rheostat, potentiometer, or the like.  
         [0040]    It is desirable to use as little energy as possible to drive the fan  56 . More specifically, the cost of driving the fan  56  should not exceed the cost savings associated with reducing standby heat loss from the flue  26 . One way to reduce the cost of driving the fan  56  is to use a thermoelectric generator  75  (illustrated in broken lines in FIG. 1) that converts heat provided by the pilot burner  46  (FIG. 1) into electricity that drives the fan  56 .  
         [0041]    FIGS.  4 - 11  illustrate alternative versions of the novel damper assembly  48 . Where elements in these figures are the same or substantially the same as the version described above, the same reference numerals are used.  
         [0042]    [0042]FIGS. 4 and 5 illustrate a second version of the damper assembly  48 . In this version, the axis of rotation  58  of the tubeaxial fan  56  is vertically-oriented, and air is drawn upwardly under the hood  49  of the damper assembly  48 , then downwardly through the fan  56  and into an annular cavity substantially identical to that described above. A portion of the hood  49  overhangs the fan  56  and defines a right angle entry channel  76  into the damper assembly  48 . The air then follows a second right angle turn down through the fan  56 , and a third right angle turn into the slots  66 . The right angle turns may be slightly more or less than 90°.  
         [0043]    The second version may also have similar control and power systems as described above, and may operate under the control of a similar controller  69 . The second version may also employ a gate  68  or variable speed fan as described above with respect to the first version. As with the first version, a radial fan may be used in place of the tubeaxial fan  56  with some modifications to the housing  50 . Because the fan  56  used in the first and second versions would cause a downward flow of air into the flue  26  in the absence of standby convection flow of flue gases, the first and second versions may be termed “circumferential downdraft” versions.  
         [0044]    [0044]FIGS. 6 and 7 illustrate a third version of the damper assembly  48 . This version may be termed an “air curtain” version. In this version, a housing  78  is mounted to the upper end  38  of the flue  26 . The housing  78  includes first and second airflow chambers or ducts  82 ,  86  and a turn-around chamber  90 . The chambers  82 ,  86 ,  90  communicate with each other and define a loop for airflow. A radial fan or blower  94  is in the first chamber  82 .  
         [0045]    During operation of the fan  94 , air is drawn and pushed by the fan  94  from the second chamber  86 , through the first chamber  82 , across the upper end  38  of the flue  26 , into the turn-around chamber  90 , and back into the second chamber  86 . The resulting curtain of air flowing across the upper end  38  of the flue  26  substantially prevents the flow of warm flue gases out of the upper end  38  of the flue  26  under the influence of standby convection alone. The third version may also have similar control and power systems as described above, and may operate under the control of a similar controller  69 . The radial fan  94  of this version may be replaced with a tubeaxial fan with some modifications to the housing  78 .  
         [0046]    [0046]FIG. 8 illustrates a fourth version of the damper assembly  48 . This version includes one or more first electrodes  98  having pointed ends. FIG. 9 illustrates one construction in which the first electrodes  98  include four electrodes  98  arranged in a square pattern with a fifth electrode  98  in the center of the square. It should be noted, however, that other numbers and configurations of electrodes  98  may be substituted for the illustrated arrangement. The fourth version is referred to herein as an “ionic airflow device”.  
         [0047]    The first electrodes  98  are connected to a device for providing electrical voltage, such as the illustrated spark plug  102 . The spark plug  102  is interconnected with a power supply  106  by way of a conductive wire  110 . It is preferable to supply DC power to the first electrodes  98 , and the power supply  106  may therefore be a DC power source or an AC power source with a DC converter or an AC signal imposed on a DC power source. The power supply  106  is grounded to the flue wall by way of a grounding wire  114 , and therefore a portion of the flue wall acts as a second electrode having a polarity opposite the first electrodes  98 . There is therefore a high voltage difference between the first electrodes  98  and the flue wall. A voltage difference of 8-10 kV is preferable, but it may also be higher.  
         [0048]    When the power supply  106  is actuated, a positive charge is applied to the first electrodes  98 . The positive charge ionizes particles in the air around the first electrodes  98 , and the ionized particles are drawn or attracted to the oppositely-charged flue wall. The pointed ends of the first electrodes  98  facilitate the creation of the ionized particles, and the relatively large size of the second electrode (i.e., the flue  26 ) ensures that the ionized particles will be attracted to the second electrode. The ionized particles are therefore biased for movement toward the flue wall, and bump into flue gas particles in or exiting the upper end  38  of the flue  26 . This creates a downward pressure on the flue gases that substantially prevents the flue gases from escaping through the upper end  38  of the flue  26 . The fourth version may therefore also be considered a downdraft damper.  
         [0049]    Alternatively, the first electrodes  98  may be positioned to the side of the upper end  38  of the flue  26  and a second electrode or electrodes may be positioned on the other side of the upper end  38  such that a cross-flow of ionic wind is created across the upper end  38 , resulting in an air curtain similar to that described above in the third version. The fourth version may also have similar control system as described above, and may operate under the control of a similar controller  69 . In addition, the magnitude of the airflow generated by the fourth version can be adjusted by varying the magnitude of the voltage difference between the first and second electrodes.  
         [0050]    [0050]FIG. 10 illustrates a fifth version of the airflow apparatus  54 , also referred to herein as an ionic airflow device. The ionic airflow device  54  is operable to direct air downward in the flue  26  during stand-by mode of the water heater  10  to counteract standby convection heat loss and is also operable to direct air upward to assist the exhaust of the products of combustion during the operation of the burner  42 . This version includes first and second electrodes  120 ,  122  separated by a gap. The first electrode  120  includes pins  124  extending toward the second electrode  122 , and the second electrode  122  includes pins  126  extending toward the first electrode  120 . The ionic airflow device  54  also includes a third electrode  128  positioned within the gap between the first and second electrodes  120 ,  122 . In this version, the third electrode  128  is a ring surrounding a screen  130 , however the shape of the third electrode  128  and the presence of the screen  120  is not critical for the operation of the ionic airflow device  54 . The first, second, and third electrodes  120 ,  122 ,  128  are connected by a bracket  132 . FIGS. 10 and 11 illustrate one construction of the first and second electrodes  120 ,  122 , in which the pins  124 ,  126  are arranged in triangular patterns. It should be noted, however, that other configurations of electrodes are known to those of ordinary skill in the art and can be substituted for the illustrated arrangement. For example, the first and second electrodes  120 ,  122  can be structually similar to the third electrode  128 .  
         [0051]    As shown in FIG. 11, the first, second, and third electrodes  120 ,  122 ,  128  are connected to an electrical circuit  134 . The electrical circuit  134  includes a power supply  106  and a switch  136  electrically connected to the power supply  106 , preferably a DC power supply. The first and second electrodes  120 ,  122  are electrically connected to the switch  136  through conductive wires  110 , and the switch  136  is operable to alternatively connect the first electrode  120  and the second electrode  122  to the power supply  106  depending upon the position of the switch  136 . The third electrode  128  and the power supply  106  are grounded through a grounding wire  114 . An over current device  138  is operably connected between the power supply  106  and the switch  136 , and the power supply  106  is also electrically connected to an ignitor  140 .  
         [0052]    When the switch  136  is in a first position, the first electrode  120  is interconnected with the power supply  106  through the electrical circuit  134 . The power supply  106  is grounded to the third electrode  128  by way of the grounding wire  114 , and therefore the third electrode  128  has a polarity opposite the first electrode  120 . There is therefore a high voltage difference between the first electrode  120  and the third electrode  128 . A voltage difference of 5-10 kV is preferable, but it may also be higher.  
         [0053]    When the power supply  106  is actuated, a positive charge is applied to the first electrode  120 . The positive charge ionizes particles in the air around the pins  124  of the first electrode  120 , and the ionized particles are drawn or attracted to the oppositely-charged third electrode  128 . The pins  124  of the first electrode  120  facilitate the creation of the ionized particles, and the relatively large size of the third electrode  128  ensures that the ionized particles will be attracted to the third electrode  128 . The ionized particles are therefore biased for movement toward the third electrode  128  (in the direction of arrows  142 ), and bump into flue gas particles in or exiting the upper end of the flue  26 . This creates a downward pressure on the flue gases substantially preventing the flue gases from escaping through the upper end of the flue  26 .  
         [0054]    When the switch  136  is in a second position, the second electrode  122  is interconnected with the power supply  106  through the electrical circuit  134 . The power supply  106  is grounded to the third electrode  128  by way of the grounding wire  114 , and therefore the third electrode  128  has a polarity opposite the second electrode  122 . There is therefore a high voltage difference between the second electrode  122  and the third electrode  128 . A voltage difference of 5-10 kV is preferable, but it may also be higher.  
         [0055]    When the power supply  106  is actuated, a positive charge is applied to the second electrode  122 . The positive charge ionizes particles in the air around the pins  126  of the second electrode  122 , and the ionized particles are drawn or attracted to the oppositely-charged third electrode  128 . The pins  126  of the second electrode  122  facilitate the creation of the ionized particles, and the relatively large size of the third electrode  128  ensures that the ionized particles will be attracted to the third electrode  128 . The ionized particles are therefore biased for movement toward the third electrode  128  (in the direction of arrows  144 ), and bump into flue gas particles in or exiting the upper end of the flue  26 . This creates an upward pressure that substantially assists the flue gases to escape the flue  26 . In this mode of operation, the ionic airflow device  54  operates as a blower unit.  
         [0056]    Efficiency, heat transfer, and the amount of heat energy removed from the products of combustion in the flue  26  can be increased in a combustion system through elements that increase the pressure drop in the flue  26 , such as the baffle  28 . The baffle  28  increases turbulence, heat transfer area, and residence time, however the increase in pressure drop adversely affects the quality of the combustion unless there is compensation for the restriction caused by the baffle  28 . When the second electrode  122  is powered, the ionic airflow device  54  acts as a blower to push or draw gas through the flue  26 .  
         [0057]    It should be noted that the ionic airflow device  54  may also include a similar control system as described above, and may operate under the control of a similar controller  69 . The magnitude of the airflow generated by the ionic airflow device  54  can also be adjusted by varying the magnitude of the voltage difference between the first and third electrodes  120 ,  128  to adjust the magnitude of the downward airflow and between the second and third electrodes  122 ,  128  to adjust the magnitude of the upward airflow.  
         [0058]    As best shown in FIG. 11, the over current device  138  disconnects power to the ionic airflow device  54  if the ionic airflow device  54  experiences an arcover event. The ionic airflow device  54  requires voltages of at least 5 kV and as high as 20 kV or greater. The electrical current can also be as low as 30 micro-amps or lower. The high voltages involved are capable of conducting through air over short distances on the order of 0.25 inches, which produces a spark. By using the over current device  138 , in the occurrence of an arcover event, the over current device  138  detects an increase of current to the electrode  120 ,  122  and, in response, disconnects the power to the electrode  120 ,  122 . The over current device  138  can also be used with the ionic airflow device  54  described as the fourth version of the airflow apparatus.  
         [0059]    In the construction illustrated in FIG. 11, the ionic airflow device  54  is electrically connected to the same high-voltage power supply  106  that powers the ignitor  140  of a direct ignition system of the water heater  10 . The ignitor  140  uses the high voltage power source  106  to create a spark, which ignites the burner  42  or intermittent pilot. This eliminates the need for a standing pilot and saves on fuel. By using a common power source for the ignitor  140  and the ionic airflow device  54 , the need for a separate power supply for the ignitor  140  is eliminated. The ionic airflow device  54  described as the fourth version of the airflow apparatus can also share the same high voltage power source with an ignitor  140 .  
         [0060]    It should be noted that all versions of the illustrated apparatus for creating airflow are able to substantially prevent the flow of flue gases out of the flue  26  under the influence of standby convection without the use of a physical obstruction (e.g., a conventional solid damper valve) being placed over the upper end  38  of the flue  26 .