Patent Publication Number: US-8985094-B2

Title: Heating system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/473,714 (PROCUSA.070PR4), filed Apr. 8, 2011, and Chinese Patent Application No. 201120401676.3, filed on Oct. 20, 2011. The entire contents of all of the applications to which this application claims priority are hereby incorporated by reference and made a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Certain embodiments disclosed herein relate generally to a heating source for use in a gas appliance. Aspects of certain embodiments may be particularly adapted for single fuel, dual fuel or multi-fuel use. The gas appliance can include, but is not limited to: heaters, boilers, dryers, washing machines, ovens, fireplaces, stoves, etc. 
     2. Description of the Related Art 
     Many varieties of heating sources, such as heaters, boilers, dryers, washing machines, ovens, fireplaces, stoves, and other heat-producing devices utilize pressurized, combustible fuels. However, such devices and certain components thereof have various limitations and disadvantages. 
     SUMMARY OF THE INVENTION 
     According to some embodiments a heating system can include any number of different components such as a fuel selector valve, a pressure regulator, a control valve, a burner nozzle, a burner, and/or an oxygen depletion sensor. In addition, a heating system can be a single fuel, dual fuel or multi-fuel heating system. For example, the heating system can be configured to be used with one or more of natural gas, liquid propane, well gas, city gas, and methane. 
     In some embodiments a heating system can comprise a fuel selector valve. The fuel selector valve can comprise an input, a first output, a second output, a first valve in-between the input and the first output and a second valve in-between the input and the second output. The first valve can include a first valve body and a first valve seat. The first valve can have a closed position wherein the first valve body is engaged with the first valve seat and an open position wherein the first valve body is disengaged from the first valve seat. The second valve can have a second valve body, a second valve seat and a third valve seat. The second valve can have two closed positions, a first closed position wherein the second valve body is engaged with the second valve seat and a second closed position wherein the second valve body is engaged with the third valve seat, and an open position wherein the first valve body is disengaged from both the second and third valve seats. Further, the fuel selector valve can be configured such that a pressure of a fluid entering the input determines whether either the first valve or the second valve is open. 
     In some embodiments, the heating system can further include a first fuel pressure regulator in communication with the first output, the first fuel pressure regulator configured to control the flow of fluid within a first predetermined pressure range and a second fuel pressure regulator in communication with the second output, the second fuel pressure regulator configured to control the flow of fluid within a second predetermined pressure range, different from the first. The fuel selector valve may further comprise first and second biasing members, the first biasing member configured to at least partially control the opening and closing of the first valve and the second biasing member configured to at least partially control the opening and closing of the second valve. In some embodiments, the first and second valve seats can be adjustable and configured to be able to calibrate the first and second valves to open and/or close at particular pressures. 
     In some embodiments, a fuel selector valve can comprise a housing having an input, a first output, and a second output; a first valve in-between the input and the first output, the first valve comprising a first valve body and a first valve seat, the first valve configured to have a closed position wherein the first valve body is engaged with the first valve seat and an open position wherein the first valve body is disengaged from the first valve seat; a second valve in-between the input and the second output, the second valve comprising a second valve body, and a second valve seat, the second valve configured to have a first closed position wherein the second valve body is engaged with the second valve seat and an open position wherein the first valve body is disengaged from the second valve seat; wherein the fuel selector valve is configured such that the first valve and the second valve are configured to move between their respective open and closed position based on a predetermined fluid pressure acting on the valve and the pressure of the fluid entering the input of the fuel selector valve determines whether either the first valve or the second valve is open. 
     In some embodiments, a fuel selector valve can comprise a housing having an inlet, an outlet, a first flow path therethrough and a second flow path therethrough different from the first flow path; at least one pressure sensitive gate within the housing, wherein the at least one pressure sensitive gate is configured to be open when a fluid within a first pressure range is flowing through the fuel selector valve and closed when a fluid within a second pressure range, different from the first, is flowing through the fuel selector valve, wherein the flow of fluid acts on the gate to either open or close the gate; wherein the fuel selector valve is configured such that when the gate is open, fluid flows through the first flow path and when the gate is closed, fluid flows through the second flow path. 
     A heating system of certain embodiments can comprise a fuel selector valve, a burner nozzle and a burner. A fuel selector valve can comprise a housing having an inlet, an outlet, a first flow path and a second flow path and at least one pressure sensitive gate within the housing. The at least one pressure sensitive gate can be configured to be open when a fluid within a first pressure range is flowing through the fuel selector valve and closed when a fluid within a second pressure range, different from the first, is flowing through the fuel selector valve, wherein the flow of fluid acts on the gate to either open or close the gate. Further the fuel selector valve can be configured such that when the gate is open, fluid flows through the first flow path and when the gate is closed, fluid flows through the second flow path. 
     A heating system of certain embodiments can comprise a fuel selector valve comprising a housing having an input, a first output, and a second output. The fuel selector valve further comprises a first valve between the input and the first output, the first valve comprising a first valve passage and a first valve body, the first valve configured to have a first position wherein the first valve body is a first distance from the first valve passage and a second position wherein the first valve body is a second distance from the first valve passage, the second distance being less than the first distance. The fuel selector valve further comprises a second valve in between the input and the second output, the second valve comprising a second valve passage and a second valve body, the second valve configured to have a first position wherein the second valve body is a first distance from the second valve passage, and a second position where the second valve body is a second distance from the second valve passage, the second distance being greater than the first distance. The fuel selector valve is configured such that whether the valves are in a first or second position depends on whether a fluid entering the input is above or below a predetermined fluid pressure threshold. 
     A heating system of certain embodiments can comprise a fuel selector valve comprising a housing having an input, a first output, and a second output. The fuel selector valve further comprises a first valve between the input and the first output, the first valve comprising a first valve passage and a first valve body, the first valve configured to have a closed position wherein the first valve body substantially blocks the first valve passage and an open position wherein the first valve body does not block the first valve passage. The fuel selector valve further comprises a second valve in between the input and the second output, the second valve comprising a second valve passage and a second valve body, the second valve configured to have a closed position wherein the second valve body substantially blocks the second valve passage and an open position wherein the second valve body does not block the second valve passage. The fuel selector valve is configured such that whether the first valve is in an open position depends on whether a fluid entering the input is above or below a predetermined fluid pressure threshold. 
     According to some embodiments, the heating system further comprises a first fuel pressure regulator in communication with the output, the first fuel pressure regulator configured to control the flow of fluid within a first predetermined pressure range; and a second fuel pressure regulator in communication with second output, the second fuel pressure regulator configured to control the flow of fluid within a second predetermined pressure range, different from the first. 
     The at least one pressure sensitive gate of some embodiments can comprise a first and a second pressure sensitive gate. The fuel selector valve can be configured such that when the first pressure sensitive gate is open, the second pressure sensitive gate is closed and when the second pressure sensitive gate is open, the first pressure sensitive gate is closed. The fuel selector valve can be further configured such that when no fluid is flowing through the fuel selector valve both the first and the second pressure sensitive gates are closed. 
     According to some embodiments, the at least one pressure sensitive gate can comprise a spring-loaded valve, or a magnet and a metal ball. In some embodiments, the fuel selector valve can further comprise first and second biasing members, the first biasing member configured to at least partially control the opening and closing of the first pressure sensitive gate and the second biasing member configured to at least partially control the opening and closing of the second pressure sensitive gate. 
     In some embodiments a heating system can comprise a burner nozzle and a burner. The burner nozzle can include a housing defining an inlet, an outlet and an inner chamber between the inlet and the outlet. The housing can be a single or multi-piece housing. The burner nozzle may also include a movable body within the inner chamber and a biasing member. The biasing member can be configured to regulate a positional relationship between the body and a wall of the inner chamber in response to a pressure of a fluid flow, flowing through the burner nozzle. 
     In some embodiments, the positional relationship between the body and the wall of the inner chamber can be configured to determine the amount of fluid flow through the burner nozzle, such that a predetermined increase in pressure of the fluid flow from an at rest position results in the movable body moving closer to the wall of the inner chamber to reduce the cross-sectional area of the flow passage between the body and the wall and correspondingly, a decrease in pressure of the fluid flow results in the movable body moving farther away from the wall of the inner chamber to increase the cross-sectional area of the flow passage between the body and the wall until the rest position is achieved. 
     In some embodiments of heating system, the positional relationship at a constant temperature of the fluid can provide for a constant BTU value as the pressure of the fuel fluctuates. 
     Further, in some embodiments, an increase in pressure of the fluid flow from the at rest position can result in the movable body moving closer to the wall of the inner chamber to reduce the cross-sectional area of the flow passage between the body and the wall until the fluid flow causes the movable body to contact the inner wall and stop the flow of fluid through the burner nozzle outlet. 
     According to certain embodiments, the burner nozzle can further comprise a second outlet, wherein the second outlet is configured to remain open and unobstructed, independent of the position of the movable body. According to some embodiments, the burner nozzle can further comprise a second flow path, substantially unaffected by the position of the movable body that leads to the second outlet. The movable body may further comprise a channel passing therethrough, the channel configured to sealingly connect to the second outlet when the movable body is in contact with the wall of the inner chamber. 
     In some embodiments, the heating system can comprise a burner and a burner nozzle, the burner nozzle comprising at least one inlet, at least one first outlet, and at least one second outlet. The heating system can also comprise a first flow path from a fuel line to the first outlet and a second flow path from the fuel line to the second outlet. The second flow path can include a movable body having a first position in which the second flow path is substantially closed, the flow through the second outlet is substantially close to zero, and the flow through the burner nozzle is less than in a second position. The movement of the movable body between the first and second positions can be controlled by the pressure of a fluid flowing through the burner nozzle. 
     Certain embodiments of a heating system can comprise a burner and a burner nozzle. The burner nozzle can include a housing defining an inlet, an outlet and an inner chamber between the inlet and the outlet; a movable body within the inner chamber; and a biasing member. The biasing member can be configured to regulate a positional relationship between the body and a wall of the inner chamber in response to a pressure of a fluid flow, flowing through the burner nozzle. According to some embodiments, in a first position of the movable body within the inner chamber, the amount of flow allowed through the burner nozzle is more than in a second position and the movable body can be configured such that movement between the first and second positions is controlled by the pressure of the fluid flow acting on the biasing member. 
     According to certain embodiments, the pressure of the flow can act on the biasing member through contact with the movable body. In the second position of some embodiments, the movable body can be configured to sealingly connect to the outlet. The movable body may further comprise a channel passing therethrough. In addition, the burner nozzle may further comprise a second outlet, and when the movable body is in the second position fluid flow can be prevented through the second outlet. In some embodiments, the burner nozzle can further include a second outlet, and when the movable body is in the second position flow of fluid is prevented through either of the outlet or the second outlet. 
     In some embodiments, a heating system can include a burner, a nozzle and a biasing member. The nozzle can have a nozzle housing, an inlet, an outlet and a valve body within the nozzle housing and between the inlet and the outlet. The valve body and biasing member can be configured such that fluid flow of a predetermined pressure acts on the valve body to at least one of 1) move, 2) open, and 3) close the valve body within the nozzle housing to control fluid flow through the nozzle. 
     In some embodiments, the heating system can also include an end cap within the outlet of the nozzle housing. The end cap can have a first end configured to be manipulated so as to adjust the position of the end cap within the outlet and at least one orifice passing through the end cap. The nozzle housing can be configured such that when the valve body is in an open position, fluid flows through the nozzle entering at the inlet and exiting at the outlet through the at least one orifice. The nozzle can be configured such that adjusting the position of the end cap adjusts at least one of the predetermined pressure required to 1) move, 2) open, and 3) close the valve body within the nozzle housing. 
     Many different types of end caps can be used. For example, the biasing member can be between the end cap and the valve body, the end cap configured to calibrate the nozzle to adjust the pressure required to move the valve body to an open position. In some examples, the end cap is a set screw. Also, the end of the end cap can cooperate with a tool to adjust the position of the end cap relative to the valve body. This end of the end cap can include a detent. The end cap can be adjusted from outside of the nozzle. The end cap can also include an orifice and/or the at least one orifice. 
     In some embodiments a heating system can comprise an oxygen depletion sensor (ODS). An ODS can include an igniter, an inlet, an outlet, a first injector, a second injector, a first valve body and a first biasing member to control flow of fuel from the inlet to the first injector and a second valve body and a second biasing member to control flow of fuel from the inlet to the second injector. There maybe one or two, or more inlets and outlets. At a first predetermined fluid pressure the first valve can be open and the second valve can be closed and at a second predetermined fluid pressure, greater than the first, the first valve can be closed by the second predetermined fluid pressure acting on the first valve and the second valve can be opened by the second predetermined fluid pressure acting on the second valve. 
     The valves can be set such that the first biasing member is configured to open the first valve by the first predetermined fluid pressure acting on the first valve, the first predetermined fluid pressure being insufficient to open the second valve. 
     In some embodiments, an ODS can comprise a housing having a single inlet and a single outlet, and having a first fluid flow path and a second fluid flow path through the housing between the inlet and the outlet; a first air intake; a second air intake; a first injector within the housing and defining part of the first fluid flow path, the first injector comprising a first orifice, the first orifice configured to direct a first fuel from the inlet and towards the outlet while drawing air into the housing through the first air intake; a second injector within the housing and defining part of the second fluid flow path, the second injector comprising a second orifice, second first orifice configured to direct a second fuel from the inlet and towards the outlet while drawing air into the housing through the second air intake, wherein the first fuel is at a pressure different from the second fuel; a first valve within the housing and defining part of the first fluid flow path, the first valve configured to control the flow of fuel to the first injector; and a second valve within the housing and defining part of the second fluid flow path, the second valve configured to control the flow of fuel to the second injector. 
     According to some embodiments, a heating system can have a burner, a control valve, and a nozzle. The control valve can include a control valve housing, an input, an output and a first valve body within the control valve housing configured such that the position of the first valve body within the control valve housing determines whether the input is in fluid communication with the output and how much fluid can flow therebetween. 
     A nozzle in some embodiments can include a nozzle housing, a second valve within the nozzle housing, an inlet, at least two outlets, and a biasing member configured such that the second valve is open during fluid flow of a first predetermined pressure, and fluid flow of a second predetermined pressure causes the second valve to close one of the at least two outlets while one of the at least two outlets remains open. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are depicted in the accompanying drawings for illustrative purposes, and should in no way be interpreted as limiting the scope of the inventions, in which like reference characters denote corresponding features consistently throughout similar embodiments. 
         FIG. 1  is a perspective cutaway view of a portion of one embodiment of a heater configured to operate using either a first fuel source or a second fuel source. 
         FIG. 2  is a perspective cutaway view of the heater of  FIG. 1 . 
         FIGS. 3A-C  show some of the various possible combinations of components of a heating assembly  10 .  FIG. 3A  illustrates a dual fuel heating assembly. 
         FIG. 3B  shows another dual fuel heating assembly.  FIG. 3C  illustrates an unregulated heating assembly. 
         FIGS. 4A-B  illustrate an embodiment of a heating assembly in schematic, showing a first configuration for liquid propane and a second configuration for natural gas. 
         FIG. 5  is a chart showing typical gas pressures of different fuels. 
         FIG. 6  is an exploded view of an embodiment of a fuel selector valve. 
         FIGS. 7A-C  are cross-sectional views of the fuel selector valve of  FIG. 6  in first, second and third positions, respectively. 
         FIG. 8A  is a side view of an embodiment of a fuel selector valve and pressure regulator. 
         FIG. 8B  is a cross-section of the fuel selector valve and pressure regulator of  FIG. 8A . 
         FIGS. 9A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 10A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 11A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 12A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 13A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 14A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 15A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 16A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 17A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 18A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 19A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 20A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 21A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIGS. 22A-B  are schematic cross-sectional views of a fuel selector valve in a first position and a second position. 
         FIG. 23  shows an exploded view of an embodiment of a nozzle. 
         FIGS. 23A-C  are sectional views of the nozzle of  FIG. 23  in first, second and third positions, respectively. 
         FIGS. 24A-B  illustrate different configurations for an end of a nozzle. 
         FIG. 25A  shows the nozzle of  FIG. 23  and a control valve. 
         FIG. 25B  illustrates the nozzle separated from the control valve of  FIG. 25A , where control valve is shown in an exploded view including two possible internal valve bodies. 
         FIG. 25C  is a cross-sectional view of the nozzle and control valve of  FIG. 25A . 
         FIGS. 26A-B  show perspective and top views respectively of a barbeque grill. 
         FIGS. 27A-B  show perspective and bottom views respectively of a stove top. 
         FIGS. 28A-B  are sectional views of an embodiment of a nozzle in first and second positions, respectively. 
         FIGS. 29A-B  are schematic cross-sectional views of a nozzle in a first position and a second position. 
         FIGS. 30A-B  are schematic cross-sectional views of a nozzle in a first position and a second position. 
         FIGS. 31A-B  are schematic cross-sectional views of a nozzle in a first position and a second position. 
         FIGS. 32A-B  are schematic cross-sectional views of a nozzle in a first position and a second position. 
         FIGS. 33A-D  are sectional views of an embodiment of a nozzle in first, second, third and fourth positions, respectively. 
         FIGS. 34A-B  show perspective and cross sectional views of a nozzle. 
         FIG. 35  shows an embodiment of an oxygen depletion sensor. 
         FIGS. 36A-B  show perspective and cross sectional views of an oxygen depletion sensor. 
         FIGS. 37A-B  show perspective and cross sectional views of an oxygen depletion sensor. 
         FIGS. 38A-B  show perspective and cross sectional views of an oxygen depletion sensor. 
         FIG. 39A  illustrates an exploded view of an embodiment of a nozzle. 
         FIG. 39B  shows a partial cross section of the nozzle of  FIG. 39A . 
         FIG. 40A  illustrates an exploded view of an embodiment of a nozzle. 
         FIG. 40B  is a partial cross section of the nozzle of  FIG. 40A   
         FIG. 40C  shows the nozzle of  FIG. 40A  in a first position and a second position. 
         FIGS. 41A-B  are sectional views of a pressure selectable valve in a first position and a second position. 
         FIGS. 42A-B  are sectional views of a nozzle in a first position and a second position. 
         FIG. 43  is a perspective cutaway view of a heater. 
         FIG. 44A  shows a possible combination of components of a heating assembly. 
         FIG. 44B  shows a possible combination of components of a heating assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Many varieties of space heaters, wall heaters, stoves, fireplaces, fireplace inserts, gas logs, and other heat-producing devices employ combustible fluid fuels, such as liquid propane and natural gas. The term “fluid,” as used herein, is a broad term used in its ordinary sense, and includes materials or substances capable of fluid flow, such as, for example, one or more gases, one or more liquids, or any combination thereof. Fluid-fueled units, such as those listed above, generally are designed to operate with a single fluid fuel type at a specific pressure or within a range of pressures. For example, some fluid-fueled heaters that are configured to be installed on a wall or a floor operate with natural gas at a pressure in a range from about 3 inches of water column to about 6 inches of water column, while others are configured to operate with liquid propane at a pressure in a range from about 8 inches of water column to about 12 inches of water column. Similarly, some gas fireplaces and gas logs are configured to operate with natural gas at a first pressure, while others are configured to operate with liquid propane at a second pressure that is different from the first pressure. As used herein, the terms “first” and “second” are used for convenience, and do not connote a hierarchical relationship among the items so identified, unless otherwise indicated. 
     Certain advantageous embodiments disclosed herein reduce or eliminate various problems associated with devices having heating sources that operate with only a single type of fuel source. Furthermore, although certain of the embodiments described hereafter are presented in a particular context, the apparatus and devices disclosed and enabled herein can benefit a wide variety of other applications and appliances. 
       FIG. 1  illustrates one embodiment of a heater  100 . The heater  100  can be a vent-free infrared heater, a vent-free blue flame heater, or some other variety of heater, such as a direct vent heater. Some embodiments include boilers, stoves, dryers, fireplaces, gas logs, etc. Other configurations are also possible for the heater  100 . In many embodiments, the heater  100  is configured to be mounted to a wall or a floor or to otherwise rest in a substantially static position. In other embodiments, the heater  100  is configured to move within a limited range. In still other embodiments, the heater  100  is portable. 
     The heater  100  can comprise a housing  200 . The housing  200  can include metal or some other suitable material for providing structure to the heater  100  without melting or otherwise deforming in a heated environment. In the illustrated embodiment, the housing  200  comprises a window  220 , one or more intake vents  240  and one or more outlet vents  260 . Heated air and/or radiant energy can pass through the window  220 . Air can flow into the heater  100  through the one or more intake vents  240  and heated air can flow out of the heater  100  through the outlet vents  260 . 
     Within the housing  200 , the heater  100 , or other gas appliance, can include a heating assembly or heating source  10 . A heating assembly  10  can include at least one or more of the components described herein. 
     With reference to  FIG. 2 , in certain embodiments, the heater  100  includes a regulator  120 . The regulator  120  can be coupled with an output line or intake line, conduit, or pipe  122 . The intake pipe  122  can be coupled with a control valve  130 , which, in some embodiments, includes a knob  132 . As illustrated, the control valve  130  is coupled to a fuel supply pipe  124  and an oxygen depletion sensor (ODS) pipe  126 . The fuel supply pipe  124  can be coupled with a nozzle  160 . The oxygen depletion sensor (ODS) pipe  126  can be coupled with an ODS  180 . In some embodiments, the ODS comprises a thermocouple  182 , which can be coupled with the control valve  130 , and an igniter line  184 , which can be coupled with an igniter switch  186 . Each of the pipes  122 ,  124 , and  126  can define a fluid passageway or flow channel through which a fluid can move or flow. 
     In some embodiments, including the illustrated embodiment, the heater  100  comprises a burner  190 . The ODS  180  can be mounted to the burner  190 , as shown. The nozzle  160  can be positioned to discharge a fluid, which may be a gas, liquid, or combination thereof into the burner  190 . For purposes of brevity, recitation of the term “gas or liquid” hereafter shall also include the possibility of a combination of a gas and a liquid. 
     Where the heater  100  is a dual fuel heater, either a first or a second fluid is introduced into the heater  100  through the regulator  120 . Still referring to  FIG. 2 , the first or the second fluid proceeds from the regulator  120  through the intake pipe  122  to the control valve  130 . The control valve  130  can permit a portion of the first or the second fluid to flow into the fuel supply pipe  124  and permit another portion of the first or the second fluid to flow into the ODS pipe  126 . From the control valve  130 , the first or the second fluid can proceed through the fuel supply pipe  124 , through the nozzle  160  and is delivered to the burner  190 . In addition, a portion of the first or the second fluid can proceed through the ODS pipe  126  to the ODS  180 . Other configurations are also possible. 
       FIGS. 3A-C  show some of the various possible combinations of components of a heating assembly  10 . Such heating assemblies can be made to be single fuel, dual fuel or multi-fuel gas appliances. For example, the heating assembly  10  can be made so that the installer of the gas appliance can connect the assembly to one of two fuels, such as either a supply of natural gas (NG) or a supply of propane (LP) and the assembly will desirably operate in the standard mode (with respect to efficiency and flame size and color) for either gas. 
       FIG. 3A  illustrates a dual fuel system, such as a vent free heater. In some embodiments, a dual fuel heating assembly can include a fuel selector valve  110 , a regulator  120 , a control valve or gas valve  130 , a nozzle  160 , a burner  190  and an ODS  180 . The arrows indicate the flow of fuel through the assembly. As can be seen in  FIG. 3B , a dual fuel heating assembly, such as a regulated stove or grill, can have similar components to the heating assembly shown in  FIG. 3A , but without the ODS. Still further heating assemblies, such as shown in  FIG. 3C , may not have a fuel selector valve  110  or a regulator  120 . This gas system is unregulated and can be an unregulated stove or grill, among other appliances. The unregulated system can be single fuel, dual fuel or multi-fuel. In some embodiments, and as described in more detail below, one or more of the fuel selector valve, ODS and nozzle, in these and in other embodiments can function in a pressure sensitive manner. 
     For example, turning to  FIGS. 4A-B , a schematic representation of a heating assembly is shown first in a state for liquid propane ( FIG. 4A ) and second in a state for natural gas ( FIG. 4B ). Looking at the fuel selector valve  110 , it can be seen that the pressure of the fluid flow through the valve  110  can cause the gate, valve or door  12 ,  14  to open or close, thus establishing or denying access to a channel  16 ,  18  and thereby to a pressure regulator  20 ,  22 . The gate, valve or door  12 ,  14  can be biased to a particular position, such as being spring loaded to bias the gate  12  to the closed position and the gate  14  to the open position. In  FIG. 4A , the gate  12  has been forced to open channel  16  and gate  14  has closed channel  18 . This can provide access to a pressure regulator  20  configured to regulate liquid propane, for example.  FIG. 4B  shows the fuel selector valve  110  at a rest state where the pressure of the flow is not enough to change to state of the gates  12 ,  14  and channel  18  is open to provide access to pressure regulator  22 , which can be configured to regulate natural gas, for example. As will be described herein after, the nozzle  160  and the ODS  180  can be configured to function in similar ways so that the pressure of the fluid flow can determine a path through the component. For example, the natural gas state ( FIG. 4B ) can allow more fluid flow than the liquid propane state ( FIG. 4A ) as represented by the arrows. 
     Different fuels are generally run at different pressures.  FIG. 5  shows four different fuels: methane, city gas, natural gas and liquid propane; and the typical pressure range of each particular fuel. The typical pressure range can mean the typical pressure range of the fuel as provided by a container, a gas main, a gas pipe, etc. and for consumer use, such as the gas provided to an appliance. Thus, natural gas may be provided to a home gas oven within the range of 3 to 10 inches of water column. The natural gas can be provided to the oven through piping connected to a gas main. As another example, propane may be provided to a barbeque grill from a propane tank with the range of 8 to 14 inches of water column. The delivery pressure of any fuel may be further regulated to provide a more certain pressure range or may be unregulated. For example, the barbeque grill may have a pressure regulator so that the fuel is delivered to the burner within the range of 10 to 12 inches of water column rather than within the range of 8 to 14 inches of water column. 
     As shown in the chart, city gas can be a combination of one or more different gases. As an example, city gas can be the gas typically provided to houses and apartments in China, and certain other countries. At times, and from certain sources, the combination of gases in city gas can be different at any one given instant as compared to the next. 
     Because each fuel has a typical range of pressures that it is delivered at, these ranges can advantageously be used in a heating assembly to make certain selections in a pressure sensitive manner. Further, certain embodiments may include one or more pressure regulators and the pressure of the fluid flow downstream of the pressure regulator can be generally known so as to also be able to make certain selections or additional selections in a pressure sensitive manner. 
       FIG. 6  illustrates the components of an embodiment of a fuel selector valve  110 . The fuel selector valve  110  can be for selecting between two different fuels. The fuel selector valve  110  can have a first mode configured to direct a flow of a first fuel (such as natural gas or NG) in a first path through the fuel selector valve and a second mode configured to direct a flow of a second fuel (such as liquid propane or LP) in a second path through the fuel selector valve. This can be done in many different ways such as the opening and/or closing of one or more valves, gates, or doors  12 ,  14  to establish various flow paths through the fuel selector valve  110 . The opening and/or closing of one or more valves, gates, or doors can be performed in a pressure sensitive manner, as explained below. 
     As illustrated, the fuel selector valve  110  of  FIGS. 6-8B  includes a main housing  24 , a fuel source connection  26 , a gasket  28  and valves  12 ,  14 . A heating assembly  10  can connect to a fuel source at the fuel source connection  26 . The fuel source connection  26  can be threaded or otherwise configured to securely connect to a fuel source. The main housing  24  can define channels  16 ,  18  and the valves  12 ,  14  can reside within the channels  16 ,  18  in the main housing  24 . The housing  24  can be a single piece or a multi-piece housing. 
     As will be shown hereafter, in the various embodiments, there can be one or more valves, gates, or doors  12 ,  14  that can function in different ways, as well as one or more channels  16 ,  18  within the housing  24 . The gates, doors or valves  12 ,  14  can work in many different ways to open or close and to thereby establish or deny access to a channel  16 ,  18 . The channels  16 ,  18  can direct fluid flow to an appropriate flow passage, such as to the appropriate pressure regulator  20 ,  22 , if pressure regulators are included in the heating assembly ( FIGS. 8A-B ). For example, channel  16  can direct flow to a first inlet  23  on a regulator  120  that connects to pressure regulator  22  and channel  18  can direct flow to a second inlet  21  that connects to pressure regulator  20 . Both pressure regulators  20 ,  22  can direct flow to the outlet  25 . Though a regulator  120  is shown that combines the two pressure regulators  20 ,  22  into one housing other configurations are also possible. 
     The shown fuel selector valve  110  of  FIGS. 6-8B  further includes, biasing members  32 ,  34 , front portions  30 ,  40  and rear portions  36 ,  38 . Biasing members  32 ,  34  can be metal springs, elastic, foam or other features used to bias the valves  12 ,  14  to a particular position, such as being spring loaded to bias both valves  12 ,  14  to the closed position. Further, the fuel selector valve  110  can be set such that each valve  12 ,  14  will open and/or close at different pressures acting on the valve. In this way, the fuel selector valve  110  can use fluid pressure to select a flow pathway through the valve. In some embodiments, this can be a function of the spring force of each individual spring, as well as the interaction of the spring with the valve. In some embodiments, the position of the spring and the valve can be adjusted to further calibrate the pressure required to open the valve  12 ,  14 . 
     For example, the front portions  30 ,  40  can be threadedly received into the channels  16 ,  18 . This can allow a user to adjust the position of the front portions  30 ,  40  within the channels and thereby adjust the compression on the spring, as can best be seen in  FIG. 7A . In this illustrated embodiment, the spring  32 ,  34  is located between the valve  12 ,  14  and the respective rear portion  36 ,  38 . The spring biases the valve to the closed position where it contacts the front portion  30 ,  40 . Each front portion  30 ,  40  has holes  42  passing therethrough that are blocked by the valve when the valve is in contact with the front portion. Thus, the adjustment of the position of the front portion with respect to the valve can affect the amount of pressure required to move the valve away from the front portion to open the valve. In some embodiments, the front portions  30 ,  40  can be adjustable from outside the housing  24 . This can allow for the valve  110  to be calibrated without having to disassemble the housing  24 . In other embodiments, such as that shown, the front portions  30 ,  40  can be preset, such as at a factory, and are not accessible from outside the housing  24 . This can prevent undesired modification or tampering with the valve  110 . Other methods and systems of calibration can also be used. 
     Fluid pressure acting on the valve  12 ,  14 , such as through the holes  42  can force the valve to open.  FIG. 7A  shows a first open position where a threshold amount of pressure has been achieved to cause the valve  14  to open, while valve  12  still remains closed.  FIG. 7B  illustrates a second open position where a second threshold pressure has been reached to close valve  14  at the rear end of the valve, and a third threshold pressure has been achieved to open valve  12 . In some embodiments, the second and third threshold pressures can be the same. In some embodiments, the third threshold pressure can be greater than the second and the first threshold pressures. Of course, this may change for different configurations, such as where the springs interact and bias the valves in different ways and to different positions. 
     In some embodiments, the fuel selector valve  110  can be used in a dual fuel appliance, such as an appliance configured to use with NG or LP. In this situation, the first threshold pressure to open valve  14  may be set to be between about 3 to 8 inches of water column, including all values and sub-ranges therebetween. In some embodiments, the first threshold pressure is about: 3, 4, 5, 6, 7 or 8 inches of water column. The second threshold pressure to close valve  14  may be set to be between about 5 to 10 inches of water column, including all values and sub-ranges therebetween. The third threshold pressure to open valve  12  can be set to be between about 8 to 12 inches of water column, including all values and sub-ranges therebetween. In some embodiments, the third threshold pressure is about: 8, 9, 10, 11 or 12 inches of water column. In a preferred embodiment, the first and second threshold pressures are between about 3 to 8 inches of water column, where the second is greater than the first and the third threshold pressure is between about 10 to 12 inches of water column. In this embodiment, as in most dual fuel embodiments, the ranges do not overlap. 
     Returning now to calibration, for certain springs, as the spring is compressed it can require a greater force to further compress the spring. Thus, moving the front portion  30 ,  40  away from the respective valve  12 ,  14  would decrease the force required to initially compress the spring, such as to move the valve  14  from a closed position ( FIG. 7A ) to an open position ( FIG. 7B ). The reverse would also be true, moving the front portion closer to the valve would increase the force required to initially compress the spring. 
     In some embodiments, a spring can be used that has a linear spring force in the desired range of movement, compression or extension, used in the fuel selection valve. The spring force for a particular use of a particular spring can be based on many different factors such as material, size, range of required movement, etc. 
     Turning now to  FIG. 7C , the valves  12 ,  14  will now be discussed in more detail. Each valve  12 ,  14  can form one of more valve seats to prevent fluid flow from passing the valve or to redirect fluid flow in a particular manner. For example, valve  12  has a forward ledge portion  43  and valve  14  has a forward ledge portion  44  and a rearward ledge portion  46 , all of which are used to seat the valve  12 ,  14  against another surface and close the valve. As shown, the forward ledge portions  43 ,  44  seat with the front portions  30 ,  40  and the rearward ledge portion  46  seats with a ledge  48  within the outer housing  24 . Other configurations are also possible, such as a valve with a portion that seats in multiple locations within the outer housing, for example to have a first closed position, on open position and a second closed position. A front face and a back face of a ledge on a valve could be used to seat the valve, as one further example. 
     The front  30 ,  40  and rear  36 ,  38  portions can be used to position the valve  12 ,  14  within the housing  24 . For example, the rear portions  36 ,  38  can surround a central region of the valve and the valve can move or slide within the rear portion. Further the spring  32 ,  34  can be between the valve and the rear portion. The front portions  30 ,  40  can have one or more holes  42  passing therethrough. Fluid pressure acting on the valve  12 ,  14 , such as through the holes  42  can force the valve to open. In some embodiments, the front portions  30 ,  40  can have a channel  50 . The channel  50  can be used to guide movement of the valve. In addition, the channel can direct fluid flow at the valve to open the valve. Because there are no exits in the channel, fluid flow does not pass around the valve but rather remains constantly acting against the valve as long as there is flow through the fuel selector valve  110 . 
     In other embodiments, the front and/or rear portions can be permanently or integrally attached to the housing  24 . Some embodiments do not have either or both of a front or rear portion. 
       FIGS. 9-22  show schematic representations of various other designs for a fuel selector valve  110 . Each set of figures “A” &amp; “B” represent the fuel selector valve in a first state (A) and a second state (B) where a fluid flow pressure would preferably be greater in the second state. 
       FIGS. 9A-B  show a series of gates  12 ,  14 . In the initial position and at the first fluid flow, gate  14  is open and gate  12  is closed. An increased fluid pressure acts on the gates to close gate  14  and to open gate  12 . The gates can be resilient and can act as springs. Thus, once the pressure is decreased, the gates can return to their initial positions. 
       FIGS. 10A-B  includes a pressure plate  52  and a spring  32 , where fluid pressure can act on the pressure plate  52  to move it from the initial position where one channel  18  is open to the second position where the original channel  18  is closed and a second channel  16  is open. The pressure plate  52  can have one or more holes  42  to allow fluid to flow through the plate  52  in some locations. In some embodiments the plate  52  can be smaller than the internal chamber so that fluid can flow around the plate instead or in addition to through the plate. 
       FIGS. 11A-B  show a series of gates  12 ,  14  in a teeter-totter configuration and a spring  32 . Gate  14  has an increased surface area compared to gate  12  so that more of the fluid flow and pressure will act on gate  14 . In the initial position and at the first fluid flow, gate  14  is open and gate  12  is closed. An increased fluid pressure acts on gate  14  to close channel  18  while expanding the spring  32 . This also opens gate  12  because the gates are connected by connecting rod  54 . 
       FIGS. 12A-B  show a series of gates  12 ,  14  in the form of steel balls connected to magnets  56 . The initial fluid flow pressure is not enough to overcome the magnetic attraction between the steel balls  12 ,  14  and the magnets  56 . Thus, gate  14  remains open and gate  12  remains closed. Increased fluid pressure overcomes the attraction and the steel balls move from their initial position to close gate  14  and to open gate  12 . Once the pressure is decreased, the magnet  56  will cause the ball to return to the initial position. 
       FIGS. 13A-B  is very similar to  FIGS. 12A-B  except that only one steel ball and a magnet are used instead to two and the ball blocks one path in the first position and blocks another path in the second.  FIGS. 14A-B  show a magnet and sliding gate  12 , similar to the single steel ball and magnet in  FIGS. 13A-B . Holes  42  passing through the gate  12  allow fluid to flow through the gate in the initial position but are blocked in the second position. 
       FIGS. 15A-B  show a diaphragm that works in a similar manner to the pressure plate of  FIGS. 10A-B . An increased pressure causes the diaphragm to move. In the initial position and at the first fluid flow, channel  18  open and channel  16  is closed. An increased fluid pressure acts on the diaphragm to plug channel  18  with gate  14  and to open gate  12 . Gate  12  can be part of a tension rod  60  which may also include a spring  32 . The tension rod can have holes  42  therethrough to allow flow past the diaphragm. Moving the diaphragm advances the rod and the gate  12  is moved away from channel  16  to allow flow therethrough. Once the pressure is decreased, the gates can return to their initial positions. 
     Each of  FIGS. 9-15  illustrates a fuel selector valve  110  that makes a selection between one of two exits.  FIGS. 16-22  show other embodiments with two or more exits where generally all of the exits can be open, and then one or more of the exits can be blocked. As will be readily apparent to one skilled in the art, the fuel selector valves of  FIGS. 16-22  function is similar ways to the fuel selector valves shown in  FIGS. 9-15  and described above. 
     It will be understood that any of the pressure sensitive valves described herein, whether as part of a fuel selector valve, nozzle, or other component of the heating assembly, can function in one of many different ways, where the valve is controlled by the pressure of the fluid flowing through the valve. For example, many of the embodiments shown herein comprise helical or coil springs. Other types of springs, or devices can also be used in the pressure sensitive valve. Further, the pressure sensitive valves can operate in a single stage or a dual stage manner. Many valves described herein both open and close the valve under the desired circumstances (dual stage), i.e. open at one pressure for a particular fuel and close at another pressure for a different fuel. Single stage valves may also be used in many of these applications. Single stage valves may only open or close the valve, or change the flow path through the valve in response to the flow of fluid. Thus for example, the fuel selector valve  110  shown in  FIG. 7A  is shown with a single stage valve  12  and a dual stage valve  14 . The dual stage valve  14  can be modified so that the valve is open in the initial condition and then closes at a set pressure, instead of being closed, opening at a set pressure and then closing at a set pressure. In some instances, it is easier and less expensive to utilize and calibrate a single stage valve as compared to a dual stage valve. In some embodiments, the valve can include an offset. The offset can offset the valve away from the front or rear portion, so that the valve cannot be closed at either the front or back end respectively. Offsets can also be used to ensure the valve does not move beyond a certain position. For example, an offset can be used that allows the valve to close, but that prevents the valve from advancing farther, such as to prevent damage to the valve housing or housing wall. 
     As discussed previously, the fuel selector valve  110  can be used to determine a particular fluid flow path for a fluid at a certain pressure or in a pressure range. Some embodiments of heating assembly can include first and second pressure regulators  20 ,  22 . The fuel selector valve  110  can advantageously be used to direct fluid flow to the appropriate pressure regulator without separate adjustment or action by a user. 
     In some embodiments, the first and second pressure regulators  20 ,  22  are separate and in some embodiments, they are connected in a regulator unit  120 , as shown in  FIGS. 4A-B  &amp;  8 A-B. A regulator unit  120  including first and second pressure regulators  20 ,  22  can advantageously have a two-in, one-out fluid flow configuration, though other fluid flow configurations are also possible including one-in or two-out. 
     The pressure regulators  20 ,  22  can function in a similar manner to those discussed in U.S. application Ser. No. 11/443,484, filed May 30, 2006, now U.S. Pat. No. 7,607,426, incorporated herein by reference and made a part of this specification; with particular reference to the discussion on pressure regulators at columns 3-9 and FIGS. 3-7 of the issued patent. 
     The first and second pressure regulators  20 ,  22  can comprise spring-loaded valves or valve assemblies. The pressure settings can be set by tensioning of a screw that allows for flow control of the fuel at a predetermined pressure or pressure range and selectively maintains an orifice open so that the fuel can flow through spring-loaded valve or valve assembly of the pressure regulator. If the pressure exceeds a threshold pressure, a plunger seat can be pushed towards a seal ring to seal off the orifice, thereby closing the pressure regulator. 
     The pressure selected depends at least in part on the particular fuel used, and may desirably provide for safe and efficient fuel combustion and reduce, mitigate, or minimize undesirable emissions and pollution. In some embodiments, the first pressure regulator  20  can be set to provide a pressure in the range from about 3 to 6 inches of water column, including all values and sub-ranges therebetween. In some embodiments, the threshold or flow-terminating pressure is about: 3, 4, 5, or 6 inches of water column. In some embodiments, the second pressure regulator  22  can be configured to provide a second pressure in the range from about 8 to 12 inches of water column, including all values and sub-ranges therebetween. In some embodiments, the second threshold or flow-terminating pressure is about: 8, 9, 10, 11 or 12 inches of water column. 
     The pressure regulators  20 ,  22  can be preset at the manufacturing site, factory, or retailer to operate with selected fuel sources. In many embodiments, the regulator  120  includes one or more caps to prevent consumers from altering the pressure settings selected by the manufacturer. Optionally, the heater  100  and/or the regulator unit  120  can be configured to allow an installation technician and/or user or customer to adjust the heater  100  and/or the regulator unit  120  to selectively regulate the heater unit for a particular fuel source. 
     Returning now to  FIGS. 3A-4B , fuel selector valves  110  and regulators  120  have been discussed above. As can be seen in the Figures, a heating source may or may not include a fuel selector valve  110  and/or a regulator  120 . In some embodiments, a fuel source can be connected to a control valve  130 , or the fuel selector valve and/or regulator can direct fuel to a control valve  130 . The control valve  130  can comprise at least one of a manual valve, a thermostat valve, an AC solenoid, a DC solenoid and a flame adjustment motor. The control valve  130  can direct fuel to the burner  190  through a nozzle  160 . The control valve  130  may also direct fuel to an ODS  180 . 
     The control valve  130  can control the amount of fuel flowing through the control valve to various parts of the heating assembly. The control valve  130  can manually and/or automatically control when and how much fuel is flowing. For example, in some embodiments, the control valve can divide the flow into two or more flows or branches. The different flows or branches can be for different purposes, such as for an oxygen depletion sensor (ODS)  180  and for a burner  190 . In some embodiments, the control valve  130  can output and control an amount of fuel for the ODS  180  and an amount of fuel for the burner  190 . 
     Turning now to the nozzle  160 , one embodiment of a nozzle  160  is shown in  FIGS. 23-23C . The nozzle  160  used in a heating assembly can be a pressure sensitive nozzle similar to the fuel selector valves  110  described herein.  FIGS. 23-23C  illustrate a nozzle  160  with an internal structure very similar to the fuel selector valve  110  shown in  FIGS. 6-8B . The illustrated nozzle includes a front portion  30 ′, a valve  12 ′, a spring  32 ′, and a rear portion  36 ′. All of which can be positioned inside a nozzle body  62 . The nozzle body  62  can be a single piece or a multi-piece body. 
     The nozzle body can include a flange  68  and threads  70 . The flange and threads can be used to attach the nozzle to another structure, such as a pipe or line running from the control valve. In some embodiments, the flange  68  is configured to be engaged by a tightening device, such as a wrench, which can aid in securing the nozzle  160  to a nozzle line. In some embodiments, the flange  68  comprises two or more substantially flat surfaces, and in other embodiments, is substantially hexagonal as shown. 
     The nozzle body  62  can define a substantially hollow cavity or pressure chamber  16 ′. The pressure chamber  16 ′ can be in fluid communication with an inlet and an outlet. In some embodiments, the outlet defines an outlet area that is smaller than the area defined by the inlet. In preferred embodiments, the pressure chamber  16 ′ decreases in cross-sectional area toward a distal end thereof. 
     As can be seen, a front ledge  43 ′ on the valve  12 ′ can contact the front portion  30 ′ such that the flow passages or holes  42 ′ are blocked, when the nozzle is in the initial “off” position ( FIG. 23A ). The flow passages or holes  42 ′ can define the inlet. Fluid flow into the nozzle  160  and acting on the valve  12 ′, such as acting on the valve  12 ′ by flowing through the holes  42 ′ and the channel  50 ′, can force the valve to compress the spring  32 ′ and move such that fluid can flow through the nozzle  160 .  FIG. 23B  shows the nozzle  160  in a first open position. Fluid is flowing through the nozzle and out the outlet holes or orifices  64 ,  66 . Under certain fluid flows the pressure can cause the valve to advance farther within the nozzle  160  further compressing the spring  32 ′. In this situation, the valve  12 ′ can reduce or block flow through the nozzle  160 . As shown in  FIG. 23C , flow through orifice  64  can be blocked by the valve  12 ′, while one or more orifices  66  remain open. The orifices  66  can have one of many different configurations, such as comprising two, three, four, or more holes or slots as shown in  FIGS. 23-24B . The orifice  64  can also have many different configurations. 
     The nozzle  160  can be used in single fuel, dual fuel or multi-fuel appliances. For example, the nozzle  160  can be used in a dual fuel appliance, such as an appliance configured for use with either of NG or LP. In this situation, the first threshold pressure to open valve  12 ′ may be set to be between about 3 to 8 inches of water column (for NG), including all values and sub-ranges therebetween. In some embodiments, the first threshold pressure is about: 3, 4, 5, 6, 7 or 8 inches of water column. The second threshold pressure to close orifice  64  may be set to be above about 8 inches of water column (for LP). In some embodiments, the second threshold pressure is about: 8, 9, 10, 11 or 12 inches of water column. In this way the nozzle  160  can be used with different fuels and yet provide an amount of fuel to the burner  190  that will create similar size of flames and/or BTU values. 
     Similar to the fuel selector valve  110 , the front portion  30 ′ of the nozzle  160  can be adjusted to calibrate the threshold pressures. In some embodiments, the spring  32 ′, as well as, other single or dual stage springs discussed herein, can have a spring constant (K) of about 0.0067 N/mm, between about 0.006-0.007 N/mm, or between about 0.005-8.008 N/mm. The spring can be approximately 7 mm, or between approximately 6-8 mm long. The spring can have an outer diameter between approximately 5-9 mm. The spring can be made from wire that is approximately 0.15 mm, 0.2 mm, or between approximately 0.1-0.3 mm in diameter. Other sizes, lengths and spring constants can also be used. 
     The nozzle  160  is shown together with a control valve  130  in  FIG. 25A . Referring back to  FIGS. 3A-C , it was pointed out that a heating assembly can have various different combinations of components and can be made to be single fuel, dual fuel or multi-fuel. The control valve  130 , shown in  FIG. 25A  can be used in many different heating assemblies including those discussed with reference to  FIGS. 3B-C . For example, the control valve can be a manual valve such as to adjust a flame height on a grill. The control valve  130  can direct fuel to the burner  190  through the nozzle  160 . The control valve  130  could also be modified to control fuel flow to an ODS but such modifications are not shown. 
     Two examples are shown in  FIGS. 26A-27B .  FIGS. 26A-B  illustrate a barbeque grill  101  having a heating assembly utilizing the nozzle  160  and control valve  130  shown in  FIG. 25A . The barbeque grill  101  is shown with three different types of burners, namely a side burner, an infrared burner, and a recessed burner.  FIGS. 27A-B  similarly show a gas stove top/range having a heating assembly utilizing the nozzle  160  and control valve  130  shown in  FIG. 25A . The barbeque grill  101  and gas stove top can be dual fuel appliances. For example, they can be used with either propane or natural gas. If using propane, an external pressure regulator may also be used. 
     Returning now to  FIGS. 25A-C , a control valve  130  can be connected to a nozzle  160 . The nozzle  160  can be one of many different types of nozzles, including those discussed herein. The control valve  130  can have a knob or other control feature  132  to move a valve body  134  within the control valve housing  136  to the desired position. FIG.  25 B shows two different internal valve bodies  134 ,  134 ′ that could be used, though other configurations are also possible. 
     The first valve body  134  can be used to provide an “OFF” position and two “ON” positions. The two “ON” positions can be a high flow position and a low flow position. The flow of fuel into the control valve can be greater in the high flow position then in the low flow position. The valve body  134  can control the flow by providing two or more different size holes  138  through which the fuel can flow. 
     The second valve body  134 ′ can be used to provide an “OFF” position and an “ON” position. The “ON” position can be adjustable to provide different amounts of fuel depending on the position of the valve body within the control valve housing. For example, the valve body  134 ′ can have low and high positions and can be adjustable between those two positions. Thus, the amount of fuel flow can be adjusted to a desired setting that may include, low, high, medium, or something in-between those positions. 
     The different “ON” positions in the valve bodies  134 ,  134 ′ can be facilitated by one or more holes or slots  138 . The holes/slots can be different sizes, and/or can change size along their length. Valve body  134  has two different sized holes  138  and valve body  134 ′ has a slot  138  that changes size along its length. The control valve housing  136  can have an inlet  135 . The position of the valve body within the housing  136  determines whether the hole or slot  138  is in fluid communication with the inlet  135  and how much fuel can flow through the control valve  130 . 
     The cross-section in  FIG. 25C  shows the control valve  130  in one of the “ON” positions. As has been discussed, the nozzle  160  shown is a pressure sensitive nozzle. The pressure sensitive nozzle can be single or dual stage. With a dual stage pressure sensitive nozzle, the pressure of the fluid flow opens the internal valve  12 ′. Independent of whether the pressure sensitive nozzle is dual stage or single stage, the pressure of the fluid flow controls whether the exit orifice  64  is open or closed and thereby controls the amount of flow through the nozzle. 
     For example, the nozzle  160  and control valve  130  can be set such that one fuel that flows at a known pressure opens the valve  12 ′ and allows the exit orifice  64  to remain open while a second fuel opens the valve  12 ′ yet closes the exit orifice  64 . The second fuel flow would only pass through the exit orifices  66 . The nozzle  160  and control valve  130  can be set so that this is the case independent of the position of the control valve  130 . In other words, whether the control valve  130  is set to a high “ON” position or a low “ON” position the nozzle  160  would operate with a predetermined exit orifice configuration based on the type of fuel used (based on the expected pressure range of that fuel). 
       FIGS. 28-34B  illustrate various additional embodiments of a nozzle  160 . The nozzles are similar to the nozzle described above and illustrate additional ways that one or more orifices can be opened, closed or modified in a pressure sensitive manner. 
       FIGS. 28A-B  show a nozzle  160  with one orifice  64  and a channel  72  in the valve  12 ′. Fluid can flow around the through the valve  12 ′. As the pressure increases, the valve  12 ′ can contact the orifice  64  and decrease the effective size of the orifice  64 . For example, the valve  12  can contact and seal the orifice  64  such that only flow from the channel  72  can leave the nozzle  160  through the orifice. As the channel  72  can have a smaller diameter than the orifice  64 , this can decrease the amount of fluid flow through the nozzle  160 . In some embodiments, the valve  12 ′ can fit inside the orifice  64  as shown ( FIG. 28B ). 
       FIGS. 29A-32B  all show additional nozzles  160  where the fluid flow at a certain pressure can dislodge or move another piece of material to block or close one or more exit orifices  64 .  FIGS. 29A-B  show a steel ball  12 ′ and a magnet  56 ′.  FIGS. 30A-B  show a force plate  52 ′ and a magnet  56 ′.  FIGS. 31A-B  show a resilient gate  12 ′.  FIGS. 32A-B  show a force plate  52 ′ and a magnet  56 ′. The arrows illustrate the fuel flow paths through the various nozzles. 
     Now looking to  FIGS. 33A-D , another embodiment of a nozzle  160  is shown. The nozzle show can be pressure sensitive such that it can be used interchangeably with different fuels, but can also advantageously be self regulating while in use with a single fuel. This is because the nozzle can be configured such that the volume of fluid flowing through the nozzle can be directly related to the fluid pressure. In other words, the nozzle can be configured to control the flow such that as the pressure increases, the volume of fuel flowing through the nozzle decreases. Thus, for a fuel at a constant temperature, the nozzle can provide a varying volume of fuel as the pressure of the fuel fluctuates while maintaining a constant BTU value. 
     This is a result of the ideal gas law:
 
PV=nRT  (1)
 
where “P” is the absolute pressure of the gas, “V” is the volume, “n” is the amount of substance; “R” is the gas constant, and “T” is the absolute temperature. Where amount and temperature remain constant, pressure and volume are inversely related. Thus, as the pressure increases, less volume of fuel is needed to provide the same amount of fuel. The amount is typically recorded in number of moles. A set number of moles of fuel will provide a particular BTU value. Therefore, the pressure sensitive nozzle shown in  FIGS. 33A-D  can advantageously provide a constant amount of fuel for a constant BTU value for a particular fuel, even as the fuel pressure fluctuates.
 
     In some embodiments, the valve  12 ′ can have an end  73  that cooperates with the internal chamber  16 ′ to determine the volume of fluid that can flow through the valve  12 ′. For example, the valve end  73  can be cylindrical while a surface  74  of the internal chamber  16 ′ can be frustoconical. Thus, as the cylinder valve end  73  approaches the frustoconical surface  74  the gap  76  between the two surfaces can slowly decrease, thus a smaller volume of fuel can pass through the gap  76 .  FIGS. 33A , B, C, and D illustrate how the gap can change as the pressure increases and the valve moves closer to the surface, until it contacts the surface and prevents flow through the valve  12 ′. In some embodiments, the valve end  73  includes a gasket  78  to sealingly close the gap  76 . 
     In some embodiments, the nozzle  160  shown in  FIGS. 33A-D  can include one or more additional orifices  66 . In some embodiments, the valve  12 ′ can have a channel running through the valve  12 ′ similar to that shown in  FIGS. 28A-B . 
     In the various embodiments of valves, including those within a nozzle, adjustments can be made to calibrate the valve. For example, in  FIGS. 33A-D , similar to the discussion with respect to the valve in  FIG. 7A , the front portion  30 ′ can be threadedly received into the interior of the nozzle. Calibrating the valve adjusts force required to move the valve  12 ′ within the valve body or housing  62 . This can be done in many ways, such as by adjusting the position of the valve  12 ′ within the valve body or housing  62  and adjusting the compression or tension on a spring. Here, calibration can adjust the position of the valve body  12 ′ in relation to the front portion  30 ′ while adjusting the amount of force required to act on the spring to move the valve a desired amount. In the example of  FIGS. 33A-D , the spring biases the valve to the closed position and adjusting the position of the front portion can increase or decrease the amount of pressure required to further compress the spring and open the valve to allow flow therethrough. 
     In some embodiments, the position of the rear portion  36 ′, as well as, or in addition to the front portion  30 ′ can be adjusted to calibrate the nozzle. For example, the rear portion  36 ′ can be threadedly received into the interior of the nozzle. Further, the front and rear portions can be adjustable from either or both of inside and outside the housing  62 . In some embodiments, the heating assembly can allow for calibration of one or more of the various valves without disassembly of the heating assembly. 
     Turning now to  FIGS. 34A-B , an embodiment of a nozzle  160  is shown. In this nozzle  160 , the position of both the front  30 ′ and rear  36 ′ portions can be adjusted. Further, at least the position of the rear portion  36 ′ can be adjusted from outside the nozzle body or housing  62 . The nozzle  160  can comprise an adjustment feature  88 . The adjustment feature  88  can be threadedly received into the housing. The adjustment feature  88  can comprise an end cap. The adjustment feature  88  can comprise a set screw. Adjustment of the position of the set screw can adjust the position of the rear portion  36 ′ and the pressure of the spring  32 ′ acting on the rear portion  36 ′. The set screw can have a detent  90 , for example, to receive the head of a screw driver, Allen wrench or other tool. The tool can be used to adjust the position of the set screw from outside the nozzle housing  62 . The set screw can include one or more holes that pass through the set screw. The one or more holes can comprise exit orifices  64 ,  66 . As shown, the exit orifice  64  connects to the detent  90 , other configurations are also possible. In some embodiments, the adjustment feature can be a part of the rear portion, or be integrally formed with the rear portion. 
     As illustrated, the adjustment feature  88  can have a frustoconical interior surface  74 ′ similar to the valve interior of  FIGS. 33A-D . The valve end  73  can cooperate with the surface  74 ′ to determine the volume of fluid that can flow through the valve  12 ′. Thus, as the cylinder valve end  73  approaches the frustoconical surface  74 ′ the gap  76  between the two surfaces can slowly decrease, thus a smaller volume of fuel can pass through the gap  76 . 
     The adjustment feature  88  can also be used with other valves and/or nozzles, for example, the nozzles shown in  FIGS. 23-25C ,  28 A-B. The adjustment feature  88  can also be used in such as way so as not to be within or form part of the flow path of fuel through the valve or nozzle. 
       FIG. 34B  also illustrates two offsets  91 ,  93 . The offset  91  can be used to prevent the valve  12 ′ from contacting the front portion  30 ′ in such a way as to close the valve completely at the front end. Offsets or similar structures can be used along the valve to prevent closing the valve on either or both of the front and the back sides of the valve. In some embodiments, an offset can be used with a single stage valve. Offsets can be part of the valve, or part of other structures. For example, the front or rear portion can include an offset. Offsets can also be used to ensure the valve does not move beyond a certain position. For example, an offset  93  can be used that allows the valve to close, but that prevents the valve from advancing farther, such as to prevent damage to the valve housing or housing wall. 
       FIG. 35  shows one embodiment of an oxygen depletion sensor (ODS)  180 . An ODS  180  or pilot light (not shown) can include a nozzle similar to the burner nozzles  160  shown and/or described herein and can be used in some heating assemblies. 
     The ODS  180  shown includes a thermocouple  182 , an electrode  80  and an ODS nozzle  82 . The ODS nozzle  82  can include an injector  84  and an air inlet  86 . A fuel can flow from the ODS line  143  through the ODS nozzle  82  and toward the thermocouple  182 . The fuel flows near the air inlet  86 , thus drawing in air for mixing with the fuel. 
     In some embodiments, the injector  84  can be a pressure sensitive injector and can include any of the features of the pressure sensitive nozzles described herein. For example, the exit orifices  64  and/or  66  can be located along line A-A of  FIG. 35  within the ODS nozzle  82 . The air inlet  86  can also be adjustable so that the air fuel combination is appropriate for the particular type of fuel used. 
     The electrode  80  can be used to ignite fuel exiting the ODS nozzle  82 . In some embodiments, a user can activate the electrode  80  by depressing the igniter switch  186  (see  FIG. 2 ). The electrode can comprise any suitable device for creating a spark to ignite a combustible fuel. In some embodiments, the electrode is a piezoelectric igniter. Igniting the fluid flowing through the nozzle  82  can create a pilot flame. In preferred embodiments, the nozzle  82  directs the pilot flame toward the thermocouple such that the thermocouple is heated by the flame, which permits fuel to flow through the control valve  130 . 
     In various embodiments, the ODS  180  provides a steady pilot flame that heats the thermocouple  182  unless the oxygen level in the ambient air drops below a threshold level. In certain embodiments, the threshold oxygen level is between about 18 percent and about 18.5 percent. In some embodiments, when the oxygen level drops below the threshold level, the pilot flame moves away from the thermocouple, the thermocouple cools, and the control valve  130  closes, thereby cutting off the fuel supply to the heater. 
       FIGS. 36A-38B  show various additional embodiments of an ODS. The ODS can include or can be connected to a valve. The valve can be user selectable or pressure selectable. For example,  FIGS. 36A-B  illustrate an ODS  180 ′ connected to a pressure selectable valve  110 ′ similar to that shown in  FIGS. 6-7C . Any of the pressure selectable valves shown here connected to an ODS can also be used to connect to a pressure regulator or other component of a heating assembly. In addition, other types of user selectable or pressure selectable valves can also be connected to an ODS. 
     Referring first to  FIGS. 36A-B , an ODS  180 ′ with pressure selectable valve  110 ′ is shown. The ODS  180 ′ can include a thermocouple  182 , an electrode  80 , a mounting bracket  92 , and an ODS nozzle  82 ′. The ODS nozzle  82 ′ can include injectors  84 A,  84 B and air inlets  86 A,  86 B. The injectors can each have an exit orifice  94 A,  94 B. The exit orifices  94 A,  94 B can the same or different sizes. The air inlets  86 A,  86 B can also be the same or different sizes, and in some embodiments are adjustable. 
     The valve  110 ′ can be similar to those described herein, such as that in  FIGS. 6-7C . The valve  110 ′ can allow for at least two different flow paths through the valve depending on the pressure of the flow. The valve  110 ′ can include a main housing  24 , a fuel source connection or inlet  26 , valves  12 ″,  14 ″, biasing members  32 ,  34 , front portions  30 ″,  40 ″ and rear portions  36 ″,  38 ″. 
     Looking to  FIG. 36B , a first flow path is shown indicated by the arrows. Fuel at a first pressure can then pass through valve  14 ″ into injector  84 B and thereby fuel can flow through the ODS. In a dual stage configuration, the fuel at the first pressure can also cause valve  14 ″ to open, while valve  12 ″ remains closed to allow the fuel to flow through the valve  110 ′. When fuel at a higher pressure is introduced into the valve  110 ′, the higher pressure fuel can cause the valve  14 ″ to close by contacting the interior surface of the valve  110 ′ at  98 . Valve  12 ″ can be opened by the higher pressure fuel which can then direct the flow to injector  84 A and thereby higher pressure fuel can flow through the ODS. The ODS can have one outlet  95  ( FIGS. 36A-B ), or two outlets  95  ( FIGS. 37A-38B ). The outlets can direct fuel towards the thermocouple. 
     In some embodiments with two outlets  95 , the outlets can be located the same or different distances away from the thermocouple. Also, the ODS can include one or more thermocouples  182  and igniters  80 . In some embodiments, the ODS can have one or more flame directors  97 . The flame directors  97  can be used to position the flame in a predetermined relationship to the thermocouple. Further, the embodiments shown in  FIGS. 37A-B  and  FIGS. 38A-B  including at least some of these features will be understood as functioning in a similar manner to the description of  FIGS. 36A-B . 
     A filter  96  can be included anywhere along the fuel flow path within the heating assembly. As shown in  FIGS. 36B ,  37 B and  38 B, a filter  96  is within the injectors  84 A,  84 B. The filter can filter out impurities in the fuel flow. 
     In some embodiments, the valve  110 ′ can allow for calibration of the valves  12 ″,  14 ″ from outside the housing. The front portions  30 ″,  40 ″ can pass through the housing  24  and can include a detent  90 ′. The detent can be used to adjust the position of the front portion within the valve  110 ′. For example, the detent  90 ′ can receive the head of a screw driver, Allen wrench or other tool to adjust the position of the front portion. 
     Referring now to  FIGS. 41A-B , another embodiment of a pressure selectable valve  110 ″ is shown which can be used with an ODS, a pressure regulator, or other components of a heating assembly. Except where described as operating in a different manner, the embodiments of  FIGS. 41A-B  are understood to function the same as or substantially similar to the embodiments illustrated by  FIGS. 35-38B  and to allow for the specific features described with reference to  FIGS. 35-38B . As illustrated, the pressure selectable valve comprises an inlet  26 , a chamber  16 ′, a plurality of flow paths  45 A,B, a first exit orifice  94 A′, and a second exit orifice  94 B′. Fuel enters the chamber  16 ′ from the inlet  26 , passes through the flow paths  45 A,B and then passes either through a first channel  50 A or a second channel  50 B in order to reach the first or second exit orifices  94 A′,B′, respectively. 
     The pressure selectable valve  110 ″ has a first valve  73 A and a second valve  73 B. The first valve  73 A is movable between a first position where the valve body  79 A is a first distance from the valve seat  77 A, and a second position where the valve body  79 A is a second distance from the valve seat  77 A, the second distance being less than the first distance. The second valve  73 B is movable between a first position where the valve body  79 B is a first distance from the valve seat  77 B, and a second position where the valve body  79 B is a second distance from the valve seat  77 B, the second distance being greater than the first distance. 
     In the first position, the valve body  79 B is desirably in contact with the valve seat  77 B (a closed position), substantially preventing any fluid flow into the second channel  50 B, while the valve body  79 A is desirably spaced from the valve seat  77 A (an open position) so as to allow fluid flow into the first channel  50 A. In the second position, the valve body  79 B is desirably spaced from the valve seat  77 B (an open position) so as to allow fluid flow into the second channel  50 B, while the valve body  79 A is desirably in contact with the valve seat  77 A (a closed position), substantially preventing any flow of fuel into the first channel  50 A. 
     The valve bodies  79 A,B can comprise any structure that can substantially limit the flow of fuel through the channels, such as a gasket, o-ring, rubber stopper, etc.  FIG. 41A  illustrates the first position of valves  73 A,B and  FIG. 41B  illustrates the second position of valves  73 A,B. 
     As illustrated in  FIGS. 41A-B , the first and second valves  73 A,B are connected by means of a lever arm  75  that has a first portion extending through a section of the first valve  73 A and a second portion extending through a section of the second valve  73 B. The lever arm is configured such that when the first valve moves from an open position to a closed position the lever arm will move the second valve from a closed position to an open position. When the first valve returns to an open position the lever arm will move the second valve to a closed position. 
     The movement of each valve as illustrated is translation along a single axis, but in other embodiments the valves can move from a closed position to an open position through translation along multiple axes, by rotating, or by some combination of translation and rotation. 
     The connection between the valves need not be through a lever arm configured as described above but can desirably occur through any device or connection that moves the second valve to an open position when the first valve moves to a closed position, and then returns the second valve to a closed position when the first valve returns to an open position. For example, the connection can occur from a lever arm that does not extend through the valves but is instead affixed to the valves. In other embodiments, the valves can be directly connected to each other. 
     The pressure selectable valve  110 ″ further comprises a biasing member  32  that exerts a force designed to keep the first valve  73 A in a closed position. When fuel enters the pressure selectable valve  110 ″ through the inlet  26 , the pressure from the fuel applies a force against a diaphragm  146  or other structure directly or indirectly connected to the biasing member  32 . In some embodiments, the diaphragm or other structure can act as a spring force and in some embodiments it can serve as the biasing member. If the fuel is at a sufficient, designated pressure, it will keep the biasing member in a compressed state, the first valve  73 A open, and the second valve  73 B closed. When a fuel that operates at a lower pressure is used, the pressure will be insufficient to compress the biasing member  32 , which will exert a closing force on the first valve  73 A, thereby opening the second valve  73 B. The pressure selectable valve  110 ″ can be configured to operate at a designated pressure consistent with the fuels and operating pressures described above. 
     The pressure selector valve  110 ″ can be incorporated into the heating assembly as illustrated in  FIG. 43 .  FIG. 43  is substantially similar to the embodiment of  FIG. 2 , with the exception that the ODS pipe  126  connects to the pressure selectable valve  110 ″ before reaching the ODS  180 . Additionally, the ODS  180  contains two outlets  95 , as described in  FIGS. 37A-38B . In some embodiments, the heating assembly can comprise two separate ODS&#39;s, one for each fuel line leading from the pressure selectable valve  110 ″. 
     Turning now to  FIGS. 39A-B ,  40 A-C, and  42 A-B, three additional embodiments of a nozzle  160  are shown. The nozzle  160  is a pressure sensitive nozzle similar to that described previously. As has also been mentioned previously, various features (such as the internal valve) of the nozzles  160  shown and described can also be used in other components, such as in fuel selector valves, and ODSs. 
     Referring first to  FIGS. 39A-B , the nozzle  160  includes a front portion  30 ″, a valve  12 ″, a spring  32 ′, and a rear portion  36 ′, all of which can be positioned inside a nozzle body  62 . The nozzle body  62  can be a single piece or a multi-piece body and can include a flange  68  and threads  70 . 
     The spring  32 ′ can be a single stage or a dual stage spring. As shown, the spring  32 ′ is a single stage spring and is configured to move from a first position to a second position at a set pressure. In the second position, the valve  12 ″ can reduce or block flow through the nozzle  160 . As shown in  FIG. 39B , flow through orifice  64  can be blocked by the valve  12 ″, while one or more orifices  66  remain open. In this way, the nozzle can function in a manner similar to those previously described. 
     The valve  12 ″ can have a passage  140  through which fluid, such as fuel, can pass. The passage  140  can have an inlet  142  and an outlet  144 . As shown, there is one inlet  142  and two outlets  144 , though any number of inlets and outlets can be used. The passage can be in central region or can direct fluid to or through a central region of the valve  12 ″. The valve  12 ″ can also include a front ledge  43 ″. The front ledge  43 ″ and the passage  140  can be used to direct all, or a substantial portion, of the fluid flow through the valve  12 ″ and can increase the forces acting on the valve to reliably open and/or close the valve. 
     Turning now to  FIGS. 40A-C  another variation of the nozzle  160  is shown. The valve  12 ′″ also has a passage  140  with an inlet  142  and an outlet  144 . The front ledge  43 ′″ of the valve  12 ′″ can be used to connect a diaphragm  146  and a diaphragm retainer  148  to the valve  12 ′″. The nozzle  160  can also include a washer  150  and a front portion  130 ′″. The diaphragm retainer can be force fit or otherwise secured onto the valve  12 ′″. This can allow the diaphragm  146 , the diaphragm retainer  148 , and the valve  12 ′″ to move together. Other configurations to connect a diaphragm to the valve  12 ′″ can also be used. 
     The front portion  130 ′″ can secure the washer  150  and diaphragm  146  in place within the nozzle. For example, in the cross section of  FIG. 40B  the front portion  30 ′″ is not shown, but can be used to secure the washer  150  and diaphragm  146  in place at the location in the nozzle shown. 
     The diaphragm  146  can act as a spring force and in some embodiments can replace the spring  32 ′. In some embodiments, the spring  32 ′ can serve to return the diaphragm  146  to an initial position. In some embodiments, the diaphragm can be set to allow the valve  12 ′″ to move at a set fluid pressure, such as at 8 inches water column, or other pressures as has been described herein with reference to other valves. In some embodiments, the diaphragm can be made from various materials including silicone and/or rubber. 
       FIG. 40C  shows the valve  12 ′″ in two different positions, such as at an initial position at a lower pressure and the second position at a higher pressure. At the higher pressure the hole  64  can be closed by the valve  12 ′″. 
     The valves  12 ″ and  12 ′″ can advantageously have an increased surface area that is exposed to the fluid flowing through the nozzle. This increased exposure can lead to increased repeatability and reliability of the nozzle under different flow circumstances. The increased surface area can help ensure that the valve sealingly closes the hole  64 . Having the fluid flow through the valve and in particular, flow through the central region of the valve can focus the fluid pressure in the center of the valve. As the hole  64  is aligned with the center of the valve focusing the fluid pressure at the center of the valve can increase the reliability of the valve, sealing the hole at increased pressures. In addition, the diaphragm has the added benefit of regulating the gas pressure similar to a typical pressure regulator. This can beneficially provide additional fluid pressure regulation throughout a heater system. 
     In some embodiments, a fuel selector valve and/or an ODS can also have a valve with a passage therethrough and/or a diaphragm. 
       FIGS. 42A-B  show yet another variation of the nozzle  160 . The nozzle has a first flow path  55  through a first channel  51  and out one or more orifices  64 . The first flow path  55  remains continuously open. The nozzle also has a second flow path  57  that passes through a second channel  53  and out one or more orifices  66 . The first channel  51  and second channel  53  can comprise a tube, pipe, or any structure or combination of structures that define a space in which a fluid can flow. 
     The second flow path  57  can be substantially blocked by a valve body  12 ″″. The valve body  12 ″″ can be connected to a diaphragm  146 , a diaphragm retainer, and/or a biasing member  32  such that the valve body  12 ″″ moves with the diaphragm  146 , diaphragm retainer, and/or a biasing member  32 , as described above. The nozzle comprises a valve seat  48 ′ against which the valve body  12 ″″ can seat, substantially closing access to the second channel  53 . As illustrated, the valve body has a beveled portion  47  that seats against the valve seat  48 ′. In other embodiments, the valve body  12 ″″ can be any shape that can mate with a portion of the nozzle to substantially block the second flow path  57 . For example, in some embodiments the valve body  12 ″″ can comprise a ledge portion as in  FIGS. 7A-C . 
       FIG. 42A  illustrates an embodiment where the fuel entering the inlet is at a pressure sufficient to compress the biasing member, seating the valve body  12 ″″ against the valve seat  48 ′ and substantially closing access to the second channel  53 . As illustrated, fuel will only be able to exit the nozzle by flowing along the first flow path, through the first channel  51  and out of the orifice  64 . The pressure needed to close the second channel  53  can be set at 8 inches water column, or other pressures as has been described herein with reference to other valves. 
       FIG. 42B  illustrates an embodiment where the fuel entering the inlet is at a pressure that fails to compress the biasing member  32  to a point where the beveled portion  47  seats against the valve seat  48 ′ and closes access to the second channel  53 . The biasing member at this lower pressure maintains the valve body  12 ″″ open and fuel will flow along both flow paths  55 ,  57  and out the nozzle  160  through the orifices  64 ,  66 . 
     In some embodiments, if the pressure is insufficient to completely close the channel  53 , the valve body  12 ″″ can be in a position close enough to the valve seat  48 ′ such that fluid flow along the second flow path  57  is restricted but access to the channel  53  is not substantially closed. In some embodiments, the valve body  12 ″″ can have a first position at a first fluid pressure and a second position at a second, higher fluid pressure such that there is a greater fluid flow along the second flow path  57  in the first position than in the second position. 
     The embodiments illustrated in  FIGS. 42A-B  are included within a single housing, but in other embodiments the second channel, the first channel, or both can be partially or completely outside of a housing. 
       FIG. 44A  illustrates a schematic representation of the flow of fuel in some embodiments of a dual fuel heating system. In some embodiments, the fuel can travel from the regulator to the control or gas valve, where it splits into two paths. The first path  126  heads toward the pressure selector valve, where a first fuel continues along a first line  99 A and a second fuel continues along a second line  99 B. The two lines either head to a single ODS or pilot with separate fuel outlets as described with reference to  FIGS. 37A-38B , or to two separate ODS or pilots, one for a first fuel and one for a second fuel. The second path  124  from the control valve heads toward a pressure orifice or nozzle, which adjusts its output to the burner based on the pressure of the fuel as described in other embodiments above. 
     In further embodiments, as illustrated in  FIG. 44B , the fuel can flow from the regulator into multiple gas valves, each of which lead to a pressure orifice or nozzle and then to a burner. This configuration illustrates embodiments where the gas is used to fuel multiple burners, such as ovens, stoves, barbecue grills, etc. 
     Advantageously, certain embodiments of the heating assembly as described herein facilitates a single appliance unit being efficaciously used with different fuel sources. This desirably saves on inventory costs, offers a retailer or store to stock and provide a single unit that is usable with more than one fuel source, and permits customers the convenience of readily obtaining a unit which operates with the fuel source of their choice. 
     Advantageously, certain embodiments of the heating assembly can transition between the different operating configurations as desired with relative ease and without or with little adjustment by an installer and/or an end user. Preferably, a user does not need to make a fuel selection through any type of control or adjustment. The systems described herein can alleviate many of the different adjustments and changes required to change from one fuel to another in many prior art heating sources. 
     It will be understood that the embodiments and components described herein can be used with, without and/or instead of other embodiments and components as described herein or otherwise. For example, the fuel selector valve described herein can be connected to the regulator  120  of the heater  100  shown in  FIGS. 1 and 2 . 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics of any embodiment described above may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. 
     Similarly, it should be appreciated that in the above description of embodiments, various features of the inventions are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim require more features than are expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment.